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Memmler’s The Human Body in Health and Disease

11th edition

Chapter 14

The Heart and Heart Disease

Circulation and the Heart

Circulation Continuous one-way circuit of the blood vessels Propelled by heart

Location of the Heart

Between the lungs Left of the midline of the body In mediastinum Apex pointed toward left

Location of the Heart

The mediastinum is a non-delineated group of structures in the thorax, surrounded by loose connective tissue. It is the central compartment of

the thoracic cavity. It contains the heart, the great vessels of the heart, esophagus, trachea,

phrenic nerve, cardiac nerve, thoracic duct,

thymus, and lymph nodes of the central chest.

Mediastinum

Structure of the Heart

Three tissue layers

Endocardium lines heart’s interior

Myocardium is thickest layer; the heart muscle

Epicardium is thin outermost layer

The Pericardium

The sac that encloses the heart Fibrous pericardium holds heart in place Serous membrane

Parietal layer Pericardial cavity Visceral layer (epicardium)

The Pericardium

Layers of the heart wall and pericardium. The serous pericardium covers the heart and lines the fibrous pericardium.

• Which layer of the heart wall is the thickest?

Special Features of the Myocardium

Cardiac muscles Are lightly striated (striped) Have single nucleus cells Are controlled involuntarily Have intercalated disks Have branching muscle fibers

Divisions of the Heart

Double pump Right side pumps blood low in oxygen to the

lungs Pulmonary circuit

Left side pumps oxygenated blood to remainder of body Systemic circuit

Four Chambers

Right atrium Receives low-oxygen blood returning from body tissue

through superior vena cava and inferior vena cava Left atrium

Receives high-oxygen blood from lungs Right ventricle

Pumps blood from right atrium to lungs Left ventricle

Pumps oxygenated blood to body

The Latin word atrium referred to the open central court, from which the enclosed rooms led off, in the type of large ancient

Roman house known as a domus.

Middle English, from Old French ventricule, from Latin ventriculus, diminutive of venter,

belly

Four Chambers

There are four chambers in the

heart: the top two chambers are

called the right and left atria, and the

bottom two chambers are the

right and left ventricles.

Pathway of blood through the heart.

Blood from the systemic circuit enters the right atrium (1) through the superior and inferior venae cavae, flows through the right AV (tricuspid) valve (2), and enters the right ventricle (3). The right ventricle pumps the blood through the pulmonary (semilunar) valve (4) into the pulmonary trunk, which divides to carry blood to the lungs in the pulmonary circuit.

Blood returns from the lungs in the pulmonary veins, enters the left atrium (5), and flows through the left AV (mitral) valve (6) into the left ventricle (7). The left ventricle pumps the blood through the aortic (semilunar) valve (8) into the aorta, which carries blood into the systemic circuit.

The heart as a double pump. The right side of the heart pumps blood through the pulmonary circuit to the lungs to be oxygenated; the left side of the heart pumps blood through the systemic circuit to all other parts of the body.

ZOOMING IN • What vessel carries

blood into the systemic circuit?

The heart and great vessels.

ZOOMING IN • Which heart

chamber has the thickest wall?

Four Valves

Atrioventricular valves Entrance valves Right atrioventricular (AV) valve (tricuspid valve) Left atrioventricular (AV) valve (bicuspid valve)

Semilunar valves Exit valves Pulmonary valve Aortic valve

Valves of the heart (superior view from anterior, atria removed). (A) When the heart is relaxed (diastole), the AV valves are open and blood flows freely from the atria to the ventricles. The pulmonary and aortic valves are closed. (B) When the ventricles contract, the AV valves close and blood pumped out of the ventricles opens the pulmonary and aortic valves. How many cusps does the right AV valve have? The left?

Blood vessels that supply the myocardium. Coronary arteries and cardiac veins are shown. (A) Anterior view. (B) Posterior view.

Opening of coronary arteries in the aortic valve (anterior view). (A) When the left ventricle contracts, the aortic valve opens. The valve cusps prevent filling of the coronary arteries. (B) When the left ventricle relaxes, backflow of blood closes the aortic valve and the coronary arteries fill.

Function of the HeartLeft and right sides of heart work together in

cardiac cycle (heartbeat) Systole (active phase, contraction) Diastole (resting phase)

The cardiac cycle. ZOOMING IN • When the ventricles contract, what valves close? What valves

open?

Cardiac Output

Calculating cardiac output Cardiac output (CO) Stroke volume (SV) Heart rate (HR) CO = HR 3 SV

Cardiac Output

The Heart’s Conduction System

Electrical energy stimulates heart muscle Nodes

Sinoatrial (SA) node (pacemaker) Atrioventricular (AV) node

Specialized fibers Atrioventricular bundle (bundle of His) Purkinje fibers (conduction myofibers)

Intercalated disks

The Heart’s Conduction

System

a, Normal rhythm; b, atrial fibrillation.

Representative action potentials are shown from the sinoatrial

node (SAN), atrium, AV node and ventricles. The vertical line on

each action potential recording corresponds

to a common time reference. LA, left

atrium; LV, left ventricle; RA, right atrium; RV, right

ventricle.

Conduction system of the heart. The sinoatrial (SA) node, the atrioventricular (AV) node, and specialized fibers conduct the electrical energy that stimulates the heart muscle to contract.

• What parts of the conduction system do the internodal pathways connect?

The Conduction Pathway

Sinus rhythm Sinoatrial (SA) node Atria Atrioventricular (AV) node Internodal pathways Bundle of His Bundle branches and Purkinje fibers Ventricles

Control of the Heart Rate

Influences that allow heart to meet changing needs rapidly

Autonomic nervous system (ANS) Sympathetic nervous system Parasympathetic system

Cranial nerve X


Autonomic nervous system. The autonomic nervous system is a part of the nervous system that non-voluntarily controls all organs and systems of the body. As the other part of nervous system ANS has its central (nuclei located in brain stem) and peripheral components (afferent and efferent fibers and peripheral ganglia) accessing all internal organs.

There are two branches of the autonomic nervous system - sympathetic and parasympathetic (vagal) nervous systems that always work as antagonists in their effect on target organs.


Sympathetic nervous systemFor most organs including heart the sympathetic nervous system stimulates organ's functioning. An increase in sympathetic stimulation causes increase in HR, stroke volume, systemic vasoconstriction, etc. The heart response time to sympathetic stimulation is relatively slow. It takes about 5 seconds to increase HR after actual onset of sympathetic stimulation and almost 30 seconds to reach its peak steady level.


Parasympathetic nervous systemIn contrast, the parasympathetic nervous system inhibits functioning of those organs. An increase in parasympathetic stimulation causes decrease in HR, stroke volume, systemic vasodilatation, etc. The heart response time to parasympathetic stimulation is almost instantaneous. Depending on actual phase of heart cycle it takes just 1 or 2 heartbeats before heart slows down to its minimum proportional to the level of stimulation.


At rest both sympathetic and parasympathetic systems are active with parasympathetic

dominance. The actual balance between them is constantly changing in attempt to achieve

optimum considering all internal and external stimuli.


Variations in Heart Rates

Bradycardia - a heart rate below 60 beats/min) is not infrequently found during a routine physical examination. Visualizing the conduction system of the heart recalls the sick sinus syndrome

Tachycardia Sinus arrhythmia Premature beat (extrasystole)


Early repolarisation syndrome


Sinus bradycardia



Tachycardia - rapid resting heart rate initiated within the ventricles, typically at 160 - 240 beats per minute (normal resting

rate is 60 - 100 beats per minute).

Sinus arrhythmia Premature beat (extrasystole)


Sinus bradycardia





Sinus arrhythmia is what can be defined as the anxious state of the slowing down of the heart while breathing out or during expiration and increasing of the heart beat while inhaling or during inspiration. This abnormality could prove to be dangerous and if remained uncured might as well lead to the death of the patient.

Premature beat (extrasystole)

systematic failure of the medulla oblongata results in the condition

which is termed as sinus arrhythmia


Sinus Arrhythmias





Sinus arrhythmia is what can be defined as the anxious state of the slowing down of the heart while breathing out or during expiration and increasing of the heart beat while inhaling or during inspiration. This abnormality could prove to be dangerous and if remained uncured might as well lead to the death of the patient.

Premature beat describes beats arising from the atrium and occurring before the expected sinus beats. Premature beats can occur randomly or in a pattern.


Atrial Premature Beat (APB) is an abnormal P wave As P waves are small and rather shapeless the difference in an APB is usually subtle. The one shown here is a clear example.

occurs earlier than expectedfollowed by a compensatory pause - but not a full compensatory pause

Heart Sounds

Lub Dup Murmurs

Organic Functional

Heart Sounds

The first heart sound(S1) as recorded by a high-resolution phonocardiography consist of 4 sequential components: (1) small low frequency vibrations, usually inaudible, that coincide with the beginning of left ventricular contraction and felt to be muscular in origin;(2) a large high- frequency vibration, easily audible related to mitral valve closure (M1);(3) followed closely by a second high frequency component related to tricuspid valve closure T1;

Heart Sounds

(4) small frequency vibrations that coincide with the acceleration of blood into the great vessel ( see below). The two major components audible at the bedside are the louder M1 best heard at the apex followed by T1 heard best at the

left lower sternal border. They are separated by only 20-30ms and at the apex are only appreciated as a single sound in the

normal subject.

Heart Disease

Most common cause of death in industrialized countries is heart and circulatory system disease

Chest pain or discomfort (angina) is the most common symptom. You feel this pain when the heart is not getting enough blood or oxygen. How bad the pain is varies from person to person.

It may feel heavy or like someone is squeezing your heart. You feel it under your breast bone (sternum), but also in your neck, arms, stomach, or upper back.

The pain usually occurs with activity or emotion, and goes away with rest or a medicine called nitroglycerin.

Other symptoms include shortness of breath and fatigue with activity (exertion).

Classifications of Heart Disease

Anatomical classification Endocarditis Myocarditis Pericarditis

Causative factors classification Congenital heart disease Rheumatic heart disease Coronary artery disease Heart failure




Inflammation of the heart muscle can be caused by:

* Infections, bacterial viruses, or fungi.* Rheumatic fever, which can occur when the body sends antibodies to fight a throat infection attacks the joints and heart tissue.* Drug or chemical poisoning.* Connective tissue diseases like lupus or rheumatoid arthritis.




Iinflammation of the pericardium, or sac-like membrane that envelopes the heart.


Causative factors classification Congenital heart disease - Congenital heart disease refers to a problem

with the heart's structure and function due to abnormal heart development before birth. Congenital means present at birth.

Rheumatic heart disease - Rheumatic heart disease is a condition in which the heart valves are damaged by rheumatic fever.

Coronary artery disease - Coronary heart disease (CHD) is a narrowing of the small blood vessels that supply blood and oxygen to the heart. CHD is also called coronary artery disease.

Heart failure - Heart failure, also called congestive heart failure, is a condition in which the heart can no longer pump enough blood to the rest of the body.


Congestive heart failure (CHF), or heart failure, is a condition in which the heart can't pump

enough blood to the body's other organs. This can result from

narrowed arteries that supply blood to the heart muscle — coronary artery disease

past heart attack, or myocardial infarction, with scar tissue that interferes with the heart

muscle's normal work

high blood pressure

heart valve disease due to past rheumatic fever or other causes

primary disease of the heart muscle itself, called cardiomyopathy.

heart defects present at birth — congenital heart defects.

infection of the heart valves and/or heart muscle itself — endocarditis and/or myocarditis

Congenital Heart Disease

Congenital heart disease often results from fetal development defects

Atrial septal defect Patent (open) ductus arteriosus Ventricular septal defect Coarctation of the aorta Tetralogy of Fallot

Patent Ductus Arteriosus

Tetralogy of Fallot

Coarctation of the Aorta

Rheumatic Heart Disease

Streptococci release toxins during infection Antibodies that combat toxin also attack heart

valves Heart valves become inflamed Valve cusps thicken and harden Pulmonary congestion occurs

Congenital Heart Disease

Preductal coarctation: The narrowing is proximal to the ductus arteriosus. If severe, blood flow to the aorta distal to the narrowing (supplying lower body) is dependent on a patent ductus arteriosus, and hence its closure can be life-threatening. This is the type seen in approximately 5% of infants with Turner Syndrome.

Ductal coarctation: The narrowing occurs at the insertion of the ductus arteriosus. This kind usually appears when the ductus arteriosus closes.

Postductal coarctation: The narrowing is distal to the insertion of the ductus arteriosus. Even with an open ductus arteriosus blood flow to the lower body can be impaired. This type is most common in adults.

Coronary Artery Disease

Coronary arteries can degenerate Myocardial infarction

Creatine kinase released upon any muscle damage. Tests for certain forms of CK indicate whether an MI occurred.

Angina pectoris Abnormalities of heart rhythm Treatment of heart attacks

Heart Failure

Heart is unable to pump sufficient blood Heart chambers enlarge Blood backs up into lungs Ventricular muscles have decreased ability Fluid accumulates in lungs, liver, abdomen,

legs

Heart Failure

The Heart in the Elderly

How the heart can age Heart shrinks Decreased contraction strength Valves become less flexible Murmur develops Cardiac output decreases Abnormal rhythms Heart block

Prevention of Heart Disease

Risk factors that cannot be modified Age Gender Heredity Body type

Risk factors that can be modified Smoking Physical inactivity Weight Diet Blood pressure Diabetes, gout

Prevention of Heart Disease

Thiamine is involved in the breakdown of energy molecules such as glucose and is also found on the membranes of neurons. Symptoms of beriberi include severe lethargy and fatigue, together with complications affecting the cardiovascular, nervous, muscular, and gastrointestinal systems

Heart Studies

Stethoscope Electrocardiograph (ECG or EKG)

Electrodes Catheterization

Fluoroscope Echocardiography (ultrasound cardiography)

Oscilloscope

Heart Studies

Stethoscope Electrocardiograph (ECG or EKG)

Electrodes Catheterization

Fluoroscope Echocardiography (ultrasound cardiography)

Oscilloscope

Complications

Irregular heart rhythm Infection Bleeding at the catheter insertion site Continued chest pain or angina Mild to moderate skin reactions (like sun-burn) from X-ray

exposure Kidney Failure Heart attack, blood clots, stroke or death Acute closure of coronary artery Emergency coronary artery bypass graft (CABG) surgery

Treatment of Heart Disease

Medical approaches Surgical approaches Combined approaches

Medications

Digitalis Nitroglycerin Beta-adrenergic blocking agents (beta-

blockers) Antiarrhythmic agents Slow calcium-channel blockers Anticoagulants

Aspirin


Digitalis - Cardiac glycosides are used therapeutically mainly in the treatment of cardiac failure, due to their anti-arrhythmic effects. These are caused by the ability to increase cardiac output by increasing force of contraction by prolonging the plateau phase of cardiac depolarization thus slowing ventricular contraction and allowing more time for ventricular filling. subsiding of chest painMedicines from foxgloves are called

"Digitalin". The use of Digitalis purpurea extract containing cardiac glycosides for

the treatment of heart condition


Nitroglycerin will dilate veins more than arteries because dilation of the veins help so that the heart does less work and requires less oxygen and blood. It also lowers the pressure in the arteries against which the heart must pump. Dilating the veins, decreases cardiac preload and leads to the following therapeutic effects during episodes of angina pectoris:

subsiding of chest pain decrease of blood pressure increase of heart rate. orthostatic hypotension

Correction of Arrhythmias


Artificial pacemaker Set rate Only when heart skips beat Adjustable pacing rate

Implantable cardioverter-defibrillator (ICD)



ECG rhythm strip of a threshold determination in a patient with a temporary (epicardial) ventricular pacemaker. The epicardial pacemaker leads were placed after the patient collapsed during aortic valve surgery. In the first half of the tracing, pacemaker stimuli at 60 beats per minute result in a wide QRS complex with a right bundle branch block pattern. Progressively weaker pacing stimuli are administered, which results in asystole in the second half of the tracing. At the end of the tracing, distortion results from muscle contractions due to a (short) hypoxic seizure. Because decreased pacemaker stimuli do not result in a ventricular escape rhythm, the patient can be said to be pacemaker-dependent and needs a definitive pacemaker.


An ECG in a person with an atrial pacemaker. Note the circle around one of the sharp electrical spike in the position were one would expect the P wave

Heart Surgery

Coronary artery bypass graft (CSBG) Angioplasty Valve replacement Surgical transplantation of heart or heart and

lungs Artificial heart

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