How is thyroid linked to heart disease? Cardiology Basics

How is thyroid linked to heart disease? Cardiology Basics

Disorders of thyroid gland can cause heart disease in multiple ways. Heart disease can occur with both hypothyroidism and hyperthyroidism. In hyperthyroidism, heart rate increases and there is a hyperdynamic circulatory state which can lead to high output cardiac failure. Unlike in the usual congestive heart failure in which the extremities are cold due to vasoconstriction, in heart failure due to hyperthyroidism, the extremities are warm. Instead of a low volume pulse in usual heart failure, thyrotoxic heart failure has a high volume pulse.

Another important cardiac problem in hyperthyroidism is atrial fibrillation with fast ventricular rate, which can also contribute to worsening of heart failure. Some authors feel that hyperthyroidism with atrial fibrillation has a high risk of stroke and other thromboembolic episodes while others disagree. 

Hypothyroidism can be associated with heart disease in different ways. Cholesterol levels go up in hypothyroidism, which can enhance plaque build up in coronary arteries enhancing obstruction. But there is a caveat, due to the low heart rate and level of activity in hypothyroidism, they may not present with angina. On the other hand, when hypothyroidism is treated with thyroid supplementation, hitherto silent coronary artery disease can become manifest. That is why thyroxine supplementation is started in low dose and titrated up slowly when associated coronary artery disease is likely.

Another important aspect is the occurrence of pericardial effusion in hypothyroidism. Along with generalised anasarca, fluid can also collect in the pericardial cavity and sometimes even cause cardiac tamponade. Though cholesterol pericarditis is usually described in rheumatoid arthritis, pericardial effusion with high cholesterol content has also been reported in hypothyroidism. In one case, scintillating yellow fluid with “gold paint” appearance was obtained on pericardial aspiration done for relief of cardiac tamponade. Microscopy of fluid showed plenty of cholesterol crystals and foamy histiocytes [1].

Reference

1. Setty NS, Sadananda KS, Nanjappa MC, Patra S, Basappa H, Krishnappa S. Massive pericardial effusion and cardiac tamponade due to cholesterol pericarditis in a case of subclinical hypothyroidism: a rare event. J Am Coll Cardiol. 2014 Apr 15;63(14):1451. doi: 10.1016/j.jacc.2013.10.093. Epub 2014 Feb 19. PMID: 24561150.