Hyperthyroid Disorders

Lesson 8: Accompanying Conditions and Complications

Cardiac Manifestations of Hyperthyroidism

Cardiac Manifestations
Hyperthyroidism can have a number of different cardiac consequences, especially in elderly patients. These conditions often become the most significant aspect of the hyperthyroid disorder.

Hyperthyroidism is associated with arrhythmias, which are disturbances in the hearts normal rhythm and tachycardia, which causes a rapid heart rate. Palpitations are also common and related to increased blood flow. Both sinus tachycardia and disturbances in atrial rhythm can also contribute to palpitations. Heart rate recovery after exercise is also prolonged in hyperthyroidism. The heart rate in hyperthyroidism is rapid both during the day and during sleep. Shortness of breath and exercise intolerance are also common and may also be related to weakness of skeletal and respiratory muscles. Beta adrenergic blocking agents such as propranolol are reported to improve muscle function and exercise tolerance in these patients.

Patients with thyrotoxicosis may have chest pain similar to that of angina pectoris related to decreased oxygen supply relative to the demands of the hyperthyroid heart. ATDs usually cause rapid improvement when chest pain occurs. Atrial fibrillation is also a common occurrence although hyperthyroidism overall accounts for fewer than 5 percent of all cases of atrial fibrillation. In the absence of atrial fibrillation, heart failure is rare.

Cardiac problems resolve rapidly when thyrotoxicosis is treated and thyroid hormone levels return to the normal range. Beta blockers are usually prescribed to reduce cardiac symptoms as soon as hyperthyroidism is diagnosed. These medications are generally continued until thyroid hormone levels are controlled. Because beta blockers mask symptoms of hyperthyroidism, they should be tapered slowly rather than abruptly discontinued. Hypothyroidism can also cause cardiac problems, including congestive heart failure, so it’s important to regularly check thyroid hormone levels so that hypothyroidism can be avoided.

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