Myocarditis vrs cardiomyopathy

CARDIOMYOPATHY OR MYOCARDITISName: Student Doctor. Rashama HolderLecturer: Dr. Wilbert Walcott

Objectives

• Introduction• Summary of the Heart

» Embryology» Anatomy» Physiology» Histology

• Cardiomyopathy• Myocarditis• Comparison of Cardiomyopathy and Myocarditis

Introduction

• Cardiomyopathy is a group of diseases that affect the heart muscle

• Myocarditis is an inflammation of the myocardium, the middle layer of the heart wall.

The Heart

The Heart

The heart is a muscular organ about the size of a fist, located between your lungs in the middle of your chest, behind and slightly to the left of your breastbone (sternum). Its between the 2nd to 5th / 6th rib anteriorly and between the 5th to 8th thoracic vertebrae posteriorly, in an area called the Mediastinum. The apex (lowest point) lies on the diaphragm.

Embryology of the Heart

The heart is the first organ to form within the embryo and this complex developmental process begins during the fourth week. At the beginning of 4th week of development, heart is a continuous and valve-less linear tube that resembles a chicken hung upside-down. It consists of 5 embryonic dilatation, that are destined to be the inflow and outflow tract and compartments of the hear without septum and valves.



The heart derives from splanchnopleuric mesenchyme in the neural plate which forms the cardiogenic region. Two endocardial tubes form here that fuse to form a primitive heart tube known as the tubular heart. Between the third and fourth week, the heart tube lengthens, and begins to fold to form an S-shape within the pericardium. This places the chambers and major vessels into the correct alignment for the developed heart. Further development will include the septa and valves formation and remodelling of the heart chambers. By the end of the fifth week the septa are complete and the heart valves are completed by the ninth week.


Before the fifth week, there is an opening in the fetal heart known as the foramen ovale. The foramen ovale allowed blood in the fetal heart to pass directly from the right atrium to the left atrium, allowing some blood to bypass the lungs. Within seconds after birth, a flap of tissue known as the septum primum that previously acted as a valve closes the foramen ovale and establishes the typical cardiac circulation pattern. A depression in the surface of the right atrium remains where the foramen ovale once walls, called the fossa ovalis



The embryonic heart begins beating at around 22 days after conception (5 weeks after the last normal menstrual period, LMP). It starts to beat at a rate near to the mother's which is about 75–80 beats per minute (bpm). The embryonic heart rate then accelerates and reaches a peak rate of 165–185 bpm early in the early 7th week (early 9th week after the LMP). After 9 weeks (start of the fetal stage) it starts to decelerate, slowing to around 145 (±25) bpm at birth. There is no difference in female and male heart rates before birth.


Anatomy of the Heart

The heart weighs between 7 and 15 ounces (200 to 425 grams) and is a little larger than the size of your fist. By the end of a long life, a person's heart may have beat (expanded and contracted) more than 3.5 billion times. In fact, each day, the average heart beats 100,000 times, pumping about 2,000 gallons (7,571 liters) of blood our heart is located between your lungs in the middle of your chest, behind and slightly to the left of your breastbone (sternum). A double-layered membrane called the pericardium surrounds your heart like a sac. The outer layer of the pericardium surrounds the roots of your heart's major blood vessels and is attached by ligaments to your spinal column, diaphragm, and other parts of your body. The inner layer of the pericardium is attached to the heart muscle. A coating of fluid separates the two layers of membrane, letting the heart move as it beats.

The heart has 4 chambers. The upper chambers are called the left and right atria, and the lower chambers are called the left and right ventricles. A wall of muscle called the septum separates the left and right atria and the left and right ventricles. The left ventricle is the largest and strongest chamber in your heart. The left ventricle's chamber walls are only about a half-inch thick, but they have enough force to push blood through the aortic valve and into the body.



Figure shows; A magnetic resonance image of mid-thorax showing the heart and all four chambers and septum


Four valves regulate blood flow through your heart:

•The tricuspid valve or right atrioventricular valve, is on the right dorsal side of the mammalian heart, between the right atrium and the right ventricle. It regulates blood flow between the right atrium and right ventricle. •The pulmonary valve is located between the right ventricle and the pulmonary artery and controls blood flow from the right ventricle into the pulmonary arteries, which carry blood to your lungs to pick up oxygen.•The mitral valve or bicuspid valve is situated between the left atrium and the left ventricle. lets oxygen-rich blood from your lungs pass from the left atrium into the left ventricle. •The aortic valve is located between the right ventricle and the pulmonary artery and opens the way for oxygen-rich blood to pass from the left ventricle into the aorta, the body's largest artery.



Layers of the heart:• PericardiumThe heart sits within a fluid-filled cavity called the pericardial cavity. The walls and lining of the pericardial cavity are a special membrane known as the pericardium. Pericardium is a type of serous membrane that produces serous fluid to lubricate the heart and prevent friction between the ever beating heart and its surrounding organs. Besides lubrication, the pericardium serves to hold the heart in position and maintain a hollow space for the heart to expand into when it is full. The pericardium has 2 layers—a visceral layer that covers the outside of the heart and a parietal layer that forms a sac around the outside of the pericardial cavity.


Anatomy of the HeartStructure of the Heart WallThe heart wall is made of 3 layers: epicardium, myocardium and endocardium.

•Epicardium. The epicardium is the outermost layer of the heart wall and is just another name for the visceral layer of the pericardium. Thus, the epicardium is a thin layer of serous membrane that helps to lubricate and protect the outside of the heart. Below the epicardium is the second, thicker layer of the heart wall: the myocardium.

•Myocardium. The myocardium is the muscular middle layer of the heart wall that contains the cardiac muscle tissue. Myocardium makes up the majority of the thickness and mass of the heart wall and is the part of the heart responsible for pumping blood. Below the myocardium is the thin endocardium layer.

• Endocardium. Endocardium is the simple squamous endothelium layer that lines the inside of the heart. The endocardium is very smooth and is responsible for keeping blood from sticking to the inside of the heart and forming potentially deadly blood clots.

The thickness of the heart wall varies in different parts of the heart. The atria of the heart have a very thin myocardium because they do not need to pump blood very far—only to the nearby ventricles. The ventricles, on the other hand, have a very thick myocardium to pump blood to the lungs or throughout the entire body. The right side of the heart has less myocardium in its walls than the left side because the left side has to pump blood through the entire body while the right side only has to pump to the lungs.



The heart needs its own reliable blood supply in order to keep beating- the coronary circulation. There are two main coronary arteries, the left and right coronary arteries, and these branch further to form several major branches (see image). The coronary arteries lie in grooves (sulci) running over the surface of the myocardium, covered over by the epicardium, and have many branches which terminate in arterioles supplying the vast capillary network of the myocardium. Even though these vessels have multiple anastomoses, significant obstruction to one or other of the main branches will lead to ischaemia in the area supplied by that branch.



PHYSIOLOGY OF THE HEART

The heart is the pump responsible for maintaining adequate circulation of oxygenated blood around the vascular network of the body. It is a four-chamber pump, with the right side receiving deoxygenated blood from the body at low presure and pumping it to the lungs (the pulmonary circulation) and the left side receiving oxygenated blood from the lungs and pumping it at high pressure around the body (the systemic circulation).

The myocardium (cardiac muscle) is a specialised form of muscle, consisting of individual cells joined by electrical connections. The contraction of each cell is produced by a rise in intracellular calcium concentration leading to spontaneous depolarisation, and as each cell is electrically connected to its neighbour, contraction of one cell leads to a wave of depolarisation and contraction across the myocardium. This depolarisation and contraction of the heart is controlled by a specialised group of cells localised in the sino-atrial node in the right atrium- the pacemaker cells.



• These cells generate a rhythmical depolarisation, which then spreads out over the atria to the atrio-ventricular node.

• The atria then contract, pushing blood into the ventricles.• The electrical conduction passes via the Atrio-ventricular

node to the bundle of His, which divides into right and left branches and then spreads out from the base of the ventricles across the myocardium.

• This leads to a 'bottom-up' contraction of the ventricles, forcing blood up and out into the pulmonary artery (right) and aorta (left).

• The atria then re-fill as the myocardium relaxes.

Histology of the Heart

• The heart is composed of cardiac muscle, specialised conductive tissue, valves, blood vessels and connective tissue.

• Cardiac muscle, the myocardium, consists of cross-striated muscle cells, cardiomyocytes, with one centrally placed nucleus.

• Nuclei are oval, rather pale and located centrally in the muscle cell which is 10 - 15 µm wide.

• Cardiac muscle cells excitation is mediated by rythmically active modified cardiac muscle cells.

• Cardiac muscle is innervated by the autonomic nervous system (involuntary), which adjusts the force generated by the muscle cells and the frequency of the heart beat.

• Cardiac muscle cells often branch at acute angles and are connected to each other by specialisations of the cell membrane in the region of the intercalated discs.

– Intercalated discs invariably occur at the ends of cardiac muscle cells in a region corresponding to the Z-line of the myofibrils.

• Cardiac muscle does not contain cells equivalent to the satellite cells of skeletal muscle


•Image of primate heart stained with Alizarin blue.Red Blood Cells (orange cells) Cardiac Muscle Cells (blue)•Cardiac muscle cells are cut longitudinally.•At high magnification see both striations and the large nuclei of the cardiac muscle cells.•Follow the course of individual cardiac muscle cells and note fine, dark blue lines which seem to cross (traverse) the fibres.•Intercalated Discs that connect the individual muscle cells and permit the conduction of electrical impulses between the cells.

• seen in longitudinal sections.


Endocardium•Inner layer of the heart (lines the atria and ventricles and covers the heart valves) and contains blood vessels.•Has 3 sublayers:

– Endothelium - innermost portion a simple squamous epithelium.– Smooth Muscle and Connective Tissue - middle layer of the

endocardium is mix of connective tissue and smooth muscle.– Subendocardial Layer - outer layer of the endocardium is loose

connective tissue joining the endocardium and myocardium.

•equivalent to tunica intima.


Myocardium

•Middle layer of the heart, thickest layer contains cardiomyocytes, blood vessels.

– contains cardiac muscle fibres and loose endomysial connective tissue containing many capillaries.

•Muscular layer.•equivalent to tunica media


Epicardium

•Outer layer of the heart, contains blood vessels and lymphatics.

– Fibro-elastic connective tissue, blood vessels, lymphatics and adipose tissue.

•Visceral layer of pericardium rather thin.•equivalent to tunica adventitia.


Cardiomyopathy

Cardiomyopathy

The term cardiomyopathy (literally, heart muscle disease) is used to describe heart disease resulting from a primary abnormality in the myocardium. Although chronic myocardial dysfunction due to ischemia should be excluded from the cardiomyopathy rubric, the term ischemic cardiomyopathy has gained some popularity among clinicians to describe CHF caused by CAD (as discussed in the section "Chronic Ischemic Heart Disease").

EtiologyOften, the cause of the cardiomyopathy is unknown. In some people, however, doctors are able to identify some contributing factors. Possible causes of cardiomyopathy include:•Genetic conditions•Long-term high blood pressure•Heart tissue damage from a previous heart attack•Chronic rapid heart rate•Heart valve problems•Metabolic disorders, such as obesity, thyroid disease or diabetes

Etiology

• Nutritional deficiencies of essential vitamins or minerals, such as thiamin (vitamin B-1)

• Pregnancy complications• Drinking too much alcohol over many years• Use of cocaine, amphetamines or anabolic steroids• Use of some chemotherapy drugs and radiation to treat cancer• Certain infections, which may injure the heart and trigger

cardiomyopathy• Iron build-up in your heart muscle (hemochromatosis)• A condition that causes inflammation and can cause lumps of cells to

grow in the heart and other organs (sarcoidosis)• A disorder that causes the build-up of abnormal proteins (amyloidosis)• Connective tissue disorders

Types of Cardiomyopathy

Cardiomyopathies can be classified according to avariety of criteria, including the underlying genetic basisof dysfunction; indeed, a number of the arrhythmia inducingChannel opathies that are included in some classificationsof cardiomyopathy were alluded to earlier. Forpurposes of general diagnosis and therapy, however, threetime-honored clinical, functional, and pathologic patternsare recognized:

Dilated cardiomyopathy

Hypertrophic cardiomyopathy

Restrictive cardiomyopathy


Functional Pattern Left Ventricular Ejection Fraction *

Mechanisms of Heart Failure Causes

Indirect Myocardial Dysfunction (Not Cardiomyopathy)

Dilated <40%Impairment of contractility (systolic dysfunction)

Idiopathic; alcohol; peripartum; genetic; myocarditis; hemochromatosis; chronic anemia; doxorubicin (Adriamycin); sarcoidosis

Ischemic heart disease; valvular heart disease; hypertensive heart disease; congenital heart disease

Hypertrophic 50–80%

Impairment of compliance (diastolic dysfunction)

Genetic; Friedreich ataxia; storage diseases; infants of diabetic mothers

Hypertensive heart disease; aortic stenosis

Restrictive 45–90%

Impairment of compliance (diastolic dysfunction)

Idiopathic; amyloidosis; radiation-induced fibrosis

Pericardial constriction


Figure shows: The three major forms of cardiomyopathy. Dilated cardiomyopathyleads primarily to systolic dysfunction, whereas restrictive and hypertrophic cardiomyopathies result in diastolic dysfunction. Note the changes in atrial and/or ventricular dilation and in ventricular wall thickness. Ao, aorta; LA, left atrium; LV, left ventricle.

Another rare form of cardiomyopathy is left ventricular non-compaction; it is a congenital disorder characterized by a distinctive “spongy” appearance of the ventricles, associated with CHF and arrhythmias. Among these three categories, the dilated form is most common (90% of cases), and the restrictive is least prevalent. Within the hemodynamic patterns of myocardial dysfunction, there is a spectrum of clinical severity, and overlap of clinical features often occurs between groups. Moreover, each of these patterns can be either idiopathic or due to a specific identifiable cause or secondary to primary extra-myocardial disease.


• Dilated Cardiomyopathy: The term dilated cardiomyopathy (DCM) is applied to a form of

cardiomyopathy characterized by progressive cardiac dilation and contractile (systolic) dysfunction, usually with concomitant hypertrophy. It is sometimes called congestive cardiomyopathy. Although it is recognized that approximately 25% to 35% of individuals with DCM have a familial (genetic) form, DCM can result from a number of acquired myocardial insults that ultimately yield a similar clinico-pathologic pattern. These include toxicities (including chronic alcoholism, a history of which can be elicited in 10% to 20% of patients), myocarditis (an inflammatory disorder that precedes the development of cardiomyopathy in at least some cases, as documented by endo-myocardial biopsy), and pregnancy-associated nutritional deficiency or immunologic reaction. In some patients, the cause of DCM is unknown; such cases are appropriately designated as idiopathic dilated cardiomyopathy.


Pathogenesis:By the time it is diagnosed, DCM has frequently already progressed to

end-stage disease; the heart is dilated and poorly contractile, and at autopsy or cardiac transplant, fails to reveal any specific pathologic features. Nevertheless, genetic and epidemiologic studies suggest that at least five general pathways can lead to end-stage DCM :

Genetic causes. DCM has a hereditary basis in 20% to50% of cases and over 40 genes are known to be mutated in this form of

cardiomyopathy; autosomal dominant inheritance is the predominant pattern, most commonly involving mutations in encoding cytoskeletal proteins, or proteins that link the sarcomere to the cytoskeleton (e.g.,

α-cardiac actin).

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X-linked DCM is most frequently associated with dystrophin gene mutations affecting the cell membrane protein that physically couples the intracellular cytoskeleton to the ECM; (different types of dystrophinmutations also underlie Duchenne and Becker muscular dystrophies. Uncommon forms of DCM are caused by mutations of genes in the mitochondrial genome that encode proteins involved in oxidative phosphorylation or fatty acid β-oxidation, presumably leading to defective ATP generation. Other cytoskeletal proteins that areaffected in genetic forms of DCM include desmin (the principal intermediate filament protein in cardiac myocytes), and the nuclear lamins A and C. Since contractile myocytes and conduction fibers share a common developmental pathway, congenital conduction abnormalities also can be a feature of inherited forms of DCM.

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• Infection. The nucleic acid “footprints” of coxsackievirus B and other enteroviruses can occasionally be detected in the myocardium from late-stage DCM patients. Moreover, sequential endomyocardial biopsies have documented instances in which infectious myocarditis progressed to DCM. Consequently, many cases of DCM are attributed to viral infections (discussed later), even though inflammation is absent from the end-stage heart. Simply finding viral transcripts or demonstrating elevated antiviral antibody titers may be sufficient to invoke a myocarditis that was “missed” in its early stages.

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• Alcohol or other toxic exposure. Alcohol abuse isstrongly associated with the development of DCM. Alcohol and its

metabolites (especially acetaldehyde) have a direct toxic effect on myocardium. Moreover, chronic alcoholism can be associated with thiamine deficiency, introducing an element of beriberi heart disease.

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• Morphology

In DCM, the heart is usually heavy, often weighing two to three times normal, and large and flabby, with dilation of all chambers (seen in figure below ). Nevertheless, because of the wall thinning that accompanies dilation, the ventricular thickness may be less than, equal to, or greater than normal. Mural thrombi are common and may be a source of thrombo-emboli. There are no primary valvular alterations, and mitral or tricuspid regurgitation, when present, results from left ventricular chamber dilation (functional regurgitation). The coronary arteries are usually free of significant narrowing, but any coronary artery obstructions present are insufficient to explain the degree of cardiac dysfunction.

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The characteristic histologic abnormalities in DCM are nonspecific, and do not typically point to a specific etiologic entity. An exception is DCM secondary to iron overload, in which marked accumulation of intra-myocardial hemosiderin is demonstrable by staining with Prussian blue. In general, the severity of morphologic changes in DCM does not necessarily reflect either the degree of dysfunction or the prognosis. Most myocytes exhibit hypertrophy with enlarged nuclei, but many are attenuated, stretched, and irregular. There is also variable interstitial and endocardial fibrosis, with scattered areas of replacement fibrosis; the latter mark previous myocyte ischemic necrosis caused byhypoperfusion.

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Figure shows: Four-chamber dilation and hypertrophy are evident. A small mural thrombus can be seen at the apex of the left ventricle .

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Figure shows: The nonspecific histologic picture in typical DCM, with myocyte hypertrophy and interstitial fibrosis (collagen is blue in this Masson trichrome–stained preparation).

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Hypertrophic cardiomyopathy (HCM) is characterized by myocardial hypertrophy, defective diastolic filling, and—in a third of cases—ventricular outflow obstruction. The heart is thick-walled, heavy, and hypercontractile, in striking contrast with the flabby, poorly contractile heart in DCM.Systolic function usually is preserved in HCM, but the myocardium does not relax and therefore exhibits primary diastolic dysfunction. HCM needs to be distinguished clinically from disorders causing ventricular stiffness (e.g., amyloid deposition) and ventricular hypertrophy (e.g., aortic stenosis and hypertension).

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PATHOGENESISMost cases of HCM are caused by missense mutations in one of several genes encoding proteins that form the contractile apparatus. In most cases, the pattern of transmission is autosomal dominant, with variable expression. Although more than 400 causative mutations in nine different genes havebeen identified, HCM is fundamentally a disorder of sarcomeric proteins. Of these, β-myosin heavy chain is most frequently affected, followed by myosin-binding protein C and troponin T. Mutations in these three genesaccount for 70% to 80% of all cases of HCM. The diverse mutations underlying HCM have one unifying feature: they all affect sarcomeric proteins and increase myofilament activation. This results in myocyte hypercontractilitywith concomitant increase in energy use and net negative energy balance. Some of the genes mutated in HCM are also mutated in DCM (e.g., beta-myosin) but in DCM the (allelic) mutations depress motor function as opposed to gain of function in HCM.

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MORPHOLOGYHCM is marked by massive myocardial hypertrophy without ventricular dilation. Classically, there is disproportionate thickening of the ventricular septum relative to the left ventricle free wall (so-called asymmetric septal hypertrophy); nevertheless, in about 10% of cases of HCM, concentric hypertrophy is seen. On longitudinal sectioning, the ventricular cavity loses its usual round-to-ovoid shape and is compressed into a “banana-like” configuration. An endocardialplaque in the left ventricular outflow tract and thickening of the anterior mitral leaflet reflect contact of the anterior mitral leaflet with the septum during ventricular systole; these changes correlate with functional left ventricular outflow tract obstruction. The characteristic histologic features in HCM are marked myocyte hypertrophy, haphazard myocyte (and myofiber) disarray, and interstitial fibrosis.

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Clinical FeaturesAlthough HCM can present at any age it typically manifestsduring the post pubertal growth spurt. The clinical symptoms can be best understood in the context of the functional abnormalities. It is characterized by a massively hypertrophied left ventricle that paradoxically provides a markedly reduced stroke volume. This condition occurs as a consequence of impaired diastolic filling and overall smaller

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Figure shows: Hypertrophic cardiomyopathy with asymmetric septal hypertrophy. A, The septal muscle bulges into the left ventricular outflow tract, giving rise to a “banana-shaped” ventricular lumen, and the left atrium is enlarged. The anterior mitral leaflet has been moved away from the septum to reveal a fibrous endocardial plaque (arrow) (see text). B, Histologic appearance demonstrating disarray, extreme hypertrophy, and characteristic branching of myocytes, as well as interstitial fibrosis.

A B

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Restrictive CardiomyopathyRestrictive cardiomyopathy is characterized by a primarydecrease in ventricular compliance, resulting in impaired ventricularfilling during diastole (simply put, the wall is stiffer). Because the contractile (systolic) function of the left ventricle usually is unaffected, the functional state can be confused with constrictive pericarditis or HCM. Restrictive cardiomyopathy can be idiopathic or associated with systemic diseases that also happen to affect the myocardium, for example radiation fibrosis, amyloidosis, sarcoidosis, or products of inborn errors of metabolism.

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MORPHOLOGYThe ventricles are of approximately normal size or onlyslightly enlarged, the cavities are not dilated, and the myocardiumis firm. Biatrial dilation commonly is due to poor ventricularfilling and pressure overloads. Microscopic examinationreveals variable degrees of interstitial fibrosis. Although grossmorphologic findings are similar for restrictive cardiomyopathyof disparate causes, endomyocardial biopsy often canreveal a specific etiologic disorder.

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Three forms of restrictive cardiomyopathy merit brief mention: Amyloidosis is caused by the deposition of extracellularproteins with the predilection for forming insoluble β-pleated sheets . Cardiac amyloidosis can occur with systemic amyloidosis or can be restricted to the heart, particularly in the case of senile cardiac amyloidosis. In the latter instance, deposition of normal (ormutant) forms of transthyretin (a liver-synthesized circulatingprotein that transports thyroxine and retinol) in the hearts of elderly patients results in a restrictive cardiomyopathy. Four percent of African Americans carry a specific mutation of transthyretin that is responsiblefor a four-fold increased risk of isolated cardiac amyloidosisin that population.

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Endomyocardial fibrosis is principally a disease of childrenand young adults in Africa and other tropical areas; it is characterized

by dense diffuse fibrosis of the ventricular endocardium and subendocardium, often involving the tricuspid and mitral valves. The fibrous tissue markedly diminishes the volume and compliance of affected chambers, resulting in a restrictive physiology. Endomyocardial

fibrosis has been linked to nutritional deficiencies and/or inflammation related to helminthic infections (e.g., hypereosinophilia); worldwide, it is the most common form of restrictive cardiomyopathy.

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Loeffler endomyocarditis also exhibits endocardial fibrosis, typically associated with formation of large mural thrombi, but without geographic predilection. Histologic examination typically shows peripheral hypereosinophilia and eosinophilic tissue infiltrates; release of eosinophil granule contents, especially major basic protein, probably engenders endo- and myocardial necrosis, followed by scarring, layering of the endocardium by thrombus, and finally thrombus organization. Of interest, some patients have an underlying hypereosinophilic myeloproliferative disorder driven by constitutivelyactive platelet derived growth factor receptor (PDGFR) tyrosine kinases (Chapter 11). Treatment of such patients with tyrosine kinase inhibitors can result in hematologic remission and reversal of the endomyocardial lesions.

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• Arrhythmogenic right ventricular dysplasia. In this rare type of cardiomyopathy, the muscle in the lower right heart chamber (right ventricle) is replaced by scar tissue. This can lead to heart rhythm problems. This condition is often caused by genetic mutations. Morphologically, the right ventricular wall is severely thinned owing to myocyte replacement by massive fatty infiltration and lesser amounts of fibrosis. Many of the mutations involve genes encoding desmosomal junctional proteins at the intercalated disk (e.g., plakoglobin), as well as proteins that interact with the desmosome (e.g., the intermediate filament desmin).

• Other types of cardiomyopathy. Other types of cardiomyopathy (unclassified cardiomyopathies) exist, but they don't fit within the other types of cardiomyopathy.

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Figure shows: Arrhythmogenic right ventricular cardiomyopathy.The right ventricle is markedly dilated with focal, almost transmural replacementof the free wall by adipose tissue and fibrosis. The left ventricle has a grossly normal appearance in this heart; it can be involved (albeit to a lesser extent) in some instances.

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Figure shows: Arrhythmogenic right ventricular cardiomyopathy.The right ventricular myocardium (red) is focally replaced by fibrous connective tissue (blue) and fat (Masson trichromestain).

In the early stages, people with cardiomyopathy may not have any signs and symptoms. But as the condition advances, signs and symptoms usually appear. Cardiomyopathy signs and symptoms may include:•Breathlessness with exertion or even at rest•Swelling of the legs, ankles and feet•Bloating of the abdomen due to fluid build-up•Cough while lying down•Fatigue•Irregular heartbeats that feel rapid, pounding or fluttering•Chest pain•Dizziness, light-headedness and fainting

Symptoms

Diagnosis

Your doctor will conduct a physical examination, take a personal and family medical history, and ask when your symptoms occur — for example, whether exercise brings on your symptoms. If your doctor thinks you have cardiomyopathy, you may need to undergo several tests to confirm the diagnosis. These tests may include : Chest X-ray Echocardiogram Treadmill stress test Cardiac catheterization Cardiac magnetic resonance imaging (MRI) Cardiac computerized tomography (CT) scan Blood tests Genetic testing or screening

Treatment

The overall goals of treatment for cardiomyopathy are to manage your signs and symptoms, prevent your condition from worsening, and reduce your risk of complications. Treatment varies by which major type of cardiomyopathy: Dilated cardiomyopathyIf you're diagnosed with dilated cardiomyopathy, your doctor may recommend treatment including:Medications. Your doctor may prescribe medications to improve your heart's pumping ability and function, improve blood flow, lower blood pressure, slow your heart rate, remove excess fluid from your body or keep blood clots from forming.

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Surgically implanted devices. If you're at risk of serious heart rhythm problems, the doctor may recommend an implantable cardioverter-defibrillator (ICD) — a device that monitors your heart rhythm and delivers electric shocks when needed to control abnormal heart rhythms. In some cases, the doctor may recommend a pacemaker that coordinates the contractions between the right and left ventricles (biventricular pacemaker).

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Hypertrophic cardiomyopathy

If you're diagnosed with hypertrophic cardiomyopathy, the doctor may recommend several treatments, including:

•Medications. The doctor may prescribe medications to relax your heart, slow its pumping action and stabilize its rhythm.

•Implantable cardioverter-defibrillator (ICD). If you're at risk of serious heart rhythm problems, your doctor may recommend an ICD to monitor your heart rhythm and deliver electric shocks when needed to control abnormal heart rhythms.

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•Septal myectomy. In a septal myectomy, your surgeon removes part of the thickened heart muscle wall (septum) that separates the two bottom heart chambers (ventricles). Removing part of the heart muscle improves blood flow through the heart and reduces mitral valve regurgitation.

•Septal ablation. In septal ablation, a small portion of the thickened heart muscle is destroyed by injecting alcohol through a long, thin tube (catheter) into the artery supplying blood to that area.

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Restrictive cardiomyopathy

Treatment for restrictive cardiomyopathy focuses on improving symptoms. Your doctor will recommend you pay careful attention to your salt and water intake and monitor your weight daily. Your doctor may also recommend you take diuretics if sodium and water retention becomes a problem. You may be prescribed medications to lower your blood pressure or control abnormal heart rhythms.If the cause of your restrictive cardiomyopathy is found, treatment will also be directed at the underlying disease, such as amyloidosis.

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Arrhythmogenic right ventricular dysplasia

If you have arrhythmogenic right ventricular dysplasia, your doctor may recommend treatment including:•Implantable cardioverter-defibrillator (ICD). If you're at risk of dangerous heart rhythms, your doctor may recommend an ICD. An ICD monitors your heart rhythm and delivers electric shocks when needed to control abnormal heart rhythms.•Medications. If an ICD isn't appropriate to treat your condition, or if you have an ICD and have frequent fast heart rhythms, your doctor may prescribe medications to regulate your heart rhythm

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Radiofrequency ablation. If other treatments aren't controlling your abnormal heart rhythms, your doctor may recommend radiofrequency ablation. In this procedure, doctors guide long, flexible tubes (catheters) through your blood vessels to your heart. Electrodes at the catheter tips transmit energy to damage a small spot of abnormal heart tissue that is causing the abnormal heart rhythm.

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Ventricular assist devices (VADs)

Ventricular assist devices (VADs) can help blood circulate through your heart. They usually are considered after less invasive approaches are unsuccessful. These devices can be used as a long-term treatment or as a short-term treatment while waiting for a heart transplant.

Heart transplant

You may be a candidate for a heart transplant if medications and other treatments are no longer effective, and you have end-stage heart failure.

Complication

Having cardiomyopathy may lead to other heart conditions, including:Heart Failure Blood Clots Valve problems Cardiac arrest and sudden death

MYOCARDITIS

MyocarditisMyocarditis is an inflammatory disease of the myocardium with a wide range of clinical presentations, from subtle to devastating. The image below depicts numerous lymphocytes with associated myocyte damage.

Figure shows: H and E, low power, showing numerous lymphocytes with associated myocyte damage

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Myocarditis encompasses a diverse group of clinical entities in which infectious agents and/or inflammatory processes primarily target the myocardium. It is important to distinguish these conditions from those, such as IHD, in which the inflammatory process is a consequence of some other cause of myocardial injury.

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PATHOGENESIS In the United States, viral infections are the most common cause of myocarditis, with coxsackie viruses A and B and other enteroviruses accounting for a majority of the cases. Cytomegalovirus (CMV), human immunodeficiency virus (HIV), influenza virus, and others are less common pathogens. Offending agents occasionally can be identified by nucleic acid footprints in infected tissues, or by serologic studies showing rising antibody titers. While some viruses cause direct cytolytic injury, in most cases the injury resultsfrom an immune response directed against virally infected cells; this is analogous to the damage inflicted by virus-specific T cells on hepatitis virus–infected liver cells. In some cases viruses trigger a reaction against cross-reacting proteins such as myosin heavy chain.

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The nonviral infectious causes of myocarditis run the entire gamut of the microbial world. The protozoan Trypanosoma cruzi is the agent of Chagas disease. Although uncommon in the northern hemisphere, Chagas disease affects up to half of the population in endemic areas of South America, with myocardial involvement in the vast majority. About 10% of the patients die during an acute attack; others can enter a chronic immune-mediated phase with developmentof progressive signs of CHF and arrhythmia 10 to 20 years later. Toxoplasma gondii (household cats are the most common vector) also can cause myocarditis, particularly in immunocompromised persons. Trichinosis is the most common helminthic disease with associated cardiac involvement.

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Myocarditis occurs in approximately 5% of patients with Lyme disease, a systemic illness caused by the bacterial spirocheteBorrelia burgdorferi. Lyme myocarditis manifests primarily as self-limited conduction system disease, frequently requiring temporary pacemaker insertion. Noninfectious causes of myocarditis include lesionsassociated with systemic diseases of immune origin, such assystemic lupus erythematosus and polymyositis. Drug hypersensitivityreactions (hypersensitivity myocarditis) also can occur with exposure to any of a wide range of agents; such reactions typically are benign and only in rare circumstances lead to CHF or sudden death.

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MORPHOLOGYIn acute myocarditis, the heart may appear normal or dilated; in advanced stages, the myocardium typically is flabby and often mottled with pale and hemorrhagic areas. Mural thrombi can be present. Microscopically, active myocarditis is characterized by edema, interstitial inflammatory infiltrates, and myocyte injury A diffuse lymphocytic infiltrate is most common , although the inflammatory involvement is often patchy and can be “missed” on endomyocardial biopsy. If the patient survives the acute phase of myocarditis, lesions can resolve without significant sequelae or heal byprogressive fibrosis.

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Figure shows: Myocarditis with scarring. Short-axis gross photograph of autopsy specimen from 8-year-old child with clinical myocarditis shows scarring of both ventricles, more prominent in left ventricle. Fibrosis shows random distribution with epicardial, myocardial, and pericardial involvement.

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Figure shows: Myocarditis. A, Lymphocytic myocarditis, with edema and associated myocyte injury. B, Hypersensitivity myocarditis, characterized by perivascular eosinophil-rich inflammatory infiltrates. C, Giant cell myocarditis, with lymphocyte and macrophage infiltrates, extensive myocyte damage, and multinucleate giant cells. D, Chagas myocarditis. A myofiber distended with trypanosomes is present, along with mononuclear inflammation and myofiber necrosis.

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In hypersensitivity myocarditis, interstitial and perivascular infiltrates are composed of lymphocytes, macrophages, and a high proportion of eosinophils. Giant cell myocarditis is a morphologically distinctive entity characterized by widespread inflammatory cellular infiltrates containing multinucleate giant cells (formed by macrophage fusion). Giant cell myocarditis probably represents the aggressive end of the spectrum of lymphocytic myocarditis, and there is at least focal—and frequently extensive—necrosis . This variant carries a poor prognosis. Chagas myocarditis is characterized by the parasitizationof scattered myofibers by trypanosomes accompanied by an inflammatory infiltrate of neutrophils, lymphocytes, macrophages, and occasional eosinophils.

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Clinical FeaturesThe clinical spectrum of myocarditis is broad; at one end, the disease is asymptomatic, and patients recover without sequelae. At the other extreme is the precipitous onset of heart failure or arrhythmias, occasionally with sudden death. Between these extremes are many levels of involvement associated with a variety of signs and symptoms,including fatigue, dyspnea, palpitations, pain, and fever. The clinical features of myocarditis can mimic those of acute MI. Clinical progression from myocarditis to DCM occasionally is seen.

Myocarditis

SymptomsMyocarditis usually manifests in an otherwise healthy person and can result in rapidly progressive (and often fatal) heart failure and arrhythmia. Patients with myocarditis have a clinical history of acute decompensation of heart failure, but they have no other underlying cardiac dysfunction or have low cardiac risk.Patients with myocarditis may present with the following signs and symptoms:•Mild symptoms of chest pain (in concurrent pericarditis), fever, sweats, chills, dyspnea •In viral myocarditis: Recent history (≤1-2 wk) of flulike symptoms of fevers, arthralgias, and malaise or pharyngitis, tonsillitis, or upper respiratory tract infection •Palpitations, syncope, or sudden cardiac death due to underlying ventricular arrhythmias or atrioventricular block (especially in giant cell myocarditis) •Heart failure

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Myocarditis in children

When children develop myocarditis, they might have signs and symptoms including:•Fever•Fainting•Breathing difficulties•Rapid breathing•Rapid or abnormal heart rhythms (arrhythmias)

Diagnosis

To diagnose myocarditis, your doctor may conduct a physical examination, and discuss your medical history and any signs or symptoms you may have. If your doctor suspects myocarditis, he or she might order one or more tests to confirm the diagnosis and determine the severity of your condition, including:

Electrocardiogram (ECG) Chest X-ray MRI Echocardiogram Blood tests Cardiac catheterization and endomyocardial biopsy

Treatment

In many cases myocarditis improves, either on its own or with treatment, leading to a complete recovery. Myocarditis treatment focuses on treating the underlying cause.

In mild cases, your doctor might tell you to rest and might prescribe medication to help your body fight off the infection causing myocarditis while your heart recovers. If bacteria are causing the infection, your doctor will prescribe antibiotics. Although antiviral medications are available, they haven't proven effective in the treatment of most cases of myocarditis.

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Certain rare types of viral myocarditis, such as giant cell and eosinophilic myocarditis, respond to corticosteroids or other medications to suppress the immune system response. In some cases caused by chronic illnesses, such as lupus, the treatment is directed at the underlying disease.

Drugs to help your heart

If myocarditis is causing heart failure or rapid or irregular heartbeats as a symptom, your doctor might hospitalize you. You might receive drugs or other treatments to regulate your heartbeat if you have an abnormal heart rhythm (arrhythmia). If you have certain abnormal heart rhythms or severe heart failure, you may be prescribed medications to reduce the risk of blood clots forming in your heart.

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If the heart is weak, the doctor might prescribe medications to reduce the heart's workload or help eliminate excess fluid. These medications might include:

•Angiotensin-converting enzyme (ACE) inhibitors. These medications, such as enalapril (Vasotec), captopril (Capoten), lisinopril (Zestril, Prinivil) and ramipril (Altace), relax the blood vessels in your heart and help blood flow more easily.•Angiotensin II receptor blockers (ARBs). These medications, such as losartan (Cozaar) and valsartan (Diovan), relax the blood vessels in your heart and help blood flow more easily.•Beta blockers. Beta blockers, such as metoprolol (Lopressor, Toprol-XL), bisoprolol (Zebeta) and carvedilol (Coreg), work in multiple ways to treat heart failure and help control irregular or fast heart rhythms.•Diuretics. These medications, such as furosemide (Lasix), relieve sodium and fluid retention.

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Treating severe cases

In some severe cases of myocarditis, aggressive treatment might be necessary, such as:

Intravenous (IV) medications. Ventricular assist devices Intra-aortic balloon pump Extracorporeal membrane oxygenation (ECMO)

Complication

When myocarditis is severe, it can permanently damage your heart muscle. This damage might cause:

Heart failure. Heart attack or stroke. Irregular heart rhythms (arrhythmias) Sudden death.

Cardiomyopathy vrs Myocarditis

Myocarditis and cardiomyopathy are a group of disorders that primarily affect the myocardium in the absence of hypertensive, congenital, ischemic or valvular heart disease. The distinction between them is somewhat arbitrary and not always made. Although, some people list myocarditis as a subset of cardiomyopathy, few differences help to distinguish the two conditions.

Comparison of Cardiomyopathy and Myocarditis

Cardiomyopathy Myocarditis

Cardiomyopathy follows a chronic course in which inflammatory features are not prominent. Etiology of the disease may be unknown or associated with toxic, metabolic, degenerative, amyloidosis, myxedema, thyrotoxicosis or glycogen storage diseases although they are very rare.

It is the acute inflammation of the myocardium. In most of the occasions, cause is idiopathic, but viral infections found to be playing a major role. Most common viral infections are coxsackie virus B, mumps, influenza. Other causes include autoimmune conditions such as rheumatic fever, rheumatoid arthritis, SLE, systemic sclerosis, toxins, sarcoidosis and radiation


Cardiomyopathies are classified according to the functional disturbances as dilated, hypertrophic, restrictive and obliterative. Histological features are non specific. Irregular atrophy and hypertrophy with progressive fibrosis may be seen.

In myocarditis, heart is dilated, flabby and pale. Small-scattered petechial hemorrhages may be seen in the myocardium. Microscopically cardiac muscles are edematous and hyperaemic. There can be infiltration of lymphocytes, plasma cells and eosinophils. Patient may be asymptomatic and sometimes recognized by the presence of an inappropriate tachycardia or abnormal ECG or from the features of heart failure.



Mostly patients are asymptomatic or presents with features of acute coronary syndrome. Chest pain is common. In severe cases, there may be associated heart failure, arrhythmias and systemic embolisation. ECG changes may be present.

Biochemical markers of myocardial ischemia are elevated in proportion to the extent of damage. There may be leukocytosis and raised ESR depending on the cause. Endomyocardial biopsy is diagnostic, but it is performed rarely.



Treatment depends on the type of cardiomyopathy but mainly include drugs, implanted pace makers, defibrillators or ablation. Chronic alcoholism is a recognized cause of dilated cardiomyopahty and the effect can be reversed with the cessation of alcohol consumption for 10-20 years. The prognosis depends on the degree of impairment of myocardial function and associated complications

Disease is self limiting. Management is mainly supportive with antibiotic therapy depending on the cause. Arrhythmias and cardiac failure should be treated accordingly. It is advised to avoid intense physical exertion during the active illness. The disease has an excellent prognosis. But in severe cases death may occur due to ventricular arrhythmias and heart failure.


Differences between Myocarditis and Cardiomyopathy

What is the difference between myocarditis and cardiomyopathy?• Myocarditis is acute while cardiomyopathy is more of a chronic condition.• Myocarditis is usually caused my infectious agents and toxins, but cardiomypathy is mostly genetic or may be associated with degenerative conditions.• In myocarditis features of acute inflammation in myofibrils are prominent but it is not in cardiomyopahty.• In myocarditis cardiac markers are elevated depending on the extent of the damage.• Myocarditis has a good prognosis.• Management options are different in the two conditions.

Differences between Myocarditis and Cardiomyopathy

Bibliography

• Robbins Basic Pathology, 8th edition and 9th edition, Edited by :Vinay Kumar, Abul K. Abbas, Jon C. Aster, Printed in Canada.

• http://epomedicine.com• www.Wikipedia.com• http://www.texasheart.org• https://embryology.med.unsw.edu.au• http://www.mayoclinic.org • www.differencebetween.com• www.Medscape.com

http://epomedicine.com/

http://www.wikipedia.com/

http://www.texasheart.org/

https://embryology.med.unsw.edu.au/

http://www.mayoclinic.org/

http://www.differencebetween.com/

http://www.medscape.com/

THE END

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Health & Medicine

Myocarditis vrs cardiomyopathy