Thyrotoxic cardiac disease

Abstract

The most recognizable features of hyperthyroidism are those that result from the effects of triiodothyronine (T3) on the heart and cardiovascular system: decreased systemic vascular resistance and increased resting heart rate, left ventricular contractility, blood volume, and cardiac output. Although these measures of cardiac performance are enhanced in hyperthyroidism, the finding of clinical cardiac failure can be somewhat paradoxical. About 6% of thyrotoxic individuals develop symptoms of heart failure, but less than 1% develop dilated -cardiomyopathy with impaired left ventricular systolic function. Heart failure resulting from thyrotoxicosis is due to a tachycardia-mediated mechanism leading to an increased level of cytosolic calcium during diastole with reduced ventricular contractility and diastolic dysfunction, often with tricuspid regurgitation. Pulmonary artery hypertension in thyrotoxicosis is gaining awareness as a cause of isolated right-sided heart failure. In both cases, older individuals are more likely to be affected. Treatment needs to be directed at management of the acute cardiovascular complications, control of the heart rate, and thyroid-specific therapy to restore a euthyroid state that will lead to resolution of the signs and symptoms of heart failure.

Current Diagnostic and Treatment Strategies for Specific Dilated Cardiomyopathies: A Scientific Statement From the American Heart Association

“…Hyperthyroidism thus results in an increased preload, a decreased afterload, and a cardiac output that is increased by up to 300% from a euthyroid state. 374 In contrast to a fall in mean systemic arterial pressure, pulmonary artery hypertension is increasingly being recognized in hyperthyroidism. 375 This finding could be the result of an increased pulmonary blood flow unaccompanied by the same decrease in pulmonary vascular resistance that occurs in the systemic circulation.…”

ANIMAL MODELS OF DISEASE: Feline hyperthyroidism: an animal model for toxic nodular goiter

“…As in older human patients, some cats will develop an apathetic form of the disease, in which the appetite is reduced and lethargy, rather than hyperexcitability or nervousness, is noted (Mooney & Peterson 2012, Peterson 2013a. Cardiac signs, including sinus tachycardia and cardiac murmur, are also very common in hyperthyroid cats, as these are in human patients with thyrotoxicosis (Klein & Danzi 2007, Dahl et al 2008. Occasionally vomiting, especially after overeating, is relatively common; other gastrointestinal signs, such as hyperdefecation or diarrhea, may also be reported.…”

Tachycardia mediated cardiomyopathy: Pathophysiology, mechanisms, clinical features and management

“…This can occur with sinus tachycardia or atrial fibrillation with a rapid ventricular response. HF resulting from thyrotoxicosis is due to a tachycardia-mediated mechanism leading to increased levels of cytosolic calcium during diastole with reduced ventricular contractility and diastolic dysfunction (99). Most patients recover their LV systolic function after control of tachycardia and achievement of a euthyroid state.…”