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Hyperthyroid Heart Disease

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Alterations in Cardiac Parameters

resting heart rate

myocardial contractility

left ventricular muscle mass predisposition to atrial arrhythmias

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Molecular and Cellular Mechanisms

Action of thyroid hormones on the heart

direct effect on the transcription of specific and

nonspecific cardiac genes

non-genomic action on plasma membranes,

mitochondria, and the sarcoplasmic reticulum

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Cardiac Manifestations

Classical symptoms

heat intolerance, irritability, nervousness, emotional the ability,

muscle weakness,menstrual abnormalities, weight loss

Cardiovascular symptoms

tachycardia (90%), palpitation (85%), dyspnea on exertion and

fatigue (50%), angina pectoris is uncommon

Physical findings

bounding peripheral pulses, wide pulse pressure, active precordium,

systolic ejection murmur (50%), Means-Lerman scratch (rubbing of

the hyperdynamic pericardium against the pleura, mimickingpericarditis),an increased incidence of mitral valve prolapse

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Prevalence of Symptoms and Signs

tachycardia 90

palpitations 85

exercise intolerance 65

bounding pulses 75

wide pulse pressure 75

hyperactive precordium 75

dyspnea on exertion 50

fatigue 50

systolic murmurs 50

systolic hypertension 30

atrial fibrillation 15

angina pectoris 5

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Rhythm Disturbances

Atrial fibrillation

the most common complication of hyperthyroidism

occurs in approximate 15% of patients

more common among men and with advancing age (25 to40% in individuals over the age of 60)

subclinical hyperthyroidism (low-TSH) is associated with

> 3x increase and the risk of developing AF

atrial flutter, paroxysmal SVT, and VT areuncommon

N Engl J Med 1994; 331:1249-1252

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Heart Failure

the hyperthyroid heart may be performing at its maximal

capacity, with little cardiac reserve - even at resting

conditions

high-output heart failure usually occurs in young individuals

with severe and long-standing hyperthyroidism and respond

well to treatment with diuretics

hyperthyroid cardiomyopathy may be due to the

detrimental effect of sustained tachycardia on the heart; the

systolic dysfunction is often but not always reversible once aeuthyroid state is reestablished

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Hypertension

systolic hypertension is found in 1/3 of patients, this

is partly due to the inability of the vascular system

to accommodate the increase in stroke volume

diastolic hypertension is rare in hyperthyroidism dueto the fall in SVR

establishment ofa a euthyroid state leads to

complete reversal of these changes

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Diagnosis of Suspected Hyperthyroidism

serum TSH concentration permits the detection of

subclinical and occult hyperthyroidism

measurement of free T4 is helpful

T3 should also be measured to detect patients withT3- toxicosis

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Causes of Hyperthyroidism

Graves disease

Hyperfunctioning adenoma

Toxic or nodular goiter

Subacute thyroiditis Chronic thyroiditis with

transient thyrotoxicosis

Thyrotoxicosis facticia

Ectopic thyroid hormone

production

Stroma ovarri

Metastatic follicular

carcinoma

Excess production of TSH

Trophoblastic tumor

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Abnormal Thyroid Hormone Levels

nonthyroidal systemic illnesses may cause

low T3 state in up to 50% of hospitalized patients, or

low T3/T4 state with normal TSH levels in severely ill pts

chronic amiodarone therapy > 50% of patients have elevated T4 levels (at an average

of 44% of baseline) with normal T3 and TSH

2-24% of treated patients may develop clinical

hyperthyroidism with decrease TSH level

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Treatment of Cardiovascular Disease

Associated with Hyperthyroidism

conservative therapy in stable patients

intravenous beta-blockers in patients with unstable

cardiac symptoms, and thyrotoxic storm

correction of the hyperthyroid state should betreated with propylthiouracil to inhibit synthesis of

thyroid hormone

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Treatment of Cardiovascular Disease

Associated with Hyperthyroidism

congestive heart failure

diuretics helps to reverse volume overload

digoxin is less useful - relative resistance

atrial fibrillation beta blocker to control ventricular rate

iv CCB should be avoided due to SVR and BP

cardioversion should not be made before restoration of a

euthyroid state; 2/3 of patients will revert spontaneously embolic risk similar to other causes of AF

Stroke 1988;19:15-18

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References

Hyperthyroidism as a high-tech output state. Am Heart J 1970; 79: 265-275.

Stroke in thyrotoxicosis with atrial fibrillation. Stroke 1988; 19:15-18.

Subclinical thyrotoxicosis. Endocrinol Metab Clin North Am 1998; 27: 37-49

Thyrotoxicosis and the heart. Endocrinol Metab Clin North Am 1998; 27: 51-62

Propranolol for thyroid storm. N Engl J Med 1997; 297: 671-672

Effects of amiodarone on thyroid function. Ann Int Med 1997; 126: 63-73 treatment of hyperthyroid disease. Ann Int Med 1994; 121: 281-288

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