From the Guidelines
Hyperthyroidism is most commonly associated with systolic flow murmurs, which are typically soft, high-pitched, and heard best at the left sternal border and cardiac apex, as a result of the hyperdynamic circulation caused by excess thyroid hormone, as described in the context of increased cardiac output and flow across heart valves 1.
Key Characteristics of Murmurs in Hyperthyroidism
- These murmurs are functional rather than structural in nature, resulting from the increased contractility and stroke volume caused by excess thyroid hormone.
- Patients with hyperthyroidism may also develop a midsystolic click with late systolic murmur if mitral valve prolapse develops as a complication.
- In cases of severe or long-standing hyperthyroidism, patients may develop atrial fibrillation, which can produce an irregular rhythm and potentially lead to varying intensity of the murmur.
Clinical Implications
- The initial treatment of patients with cardiac-related symptoms and signs of hyperthyroidism should include a β-blocker to lower the heart rate to nearly normal, as recommended in the 2016 scientific statement from the American Heart Association 1.
- Successful treatment of the underlying hyperthyroid state typically leads to the resolution of these murmurs, as the hyperdynamic circulation normalizes with restoration of euthyroidism.
Diagnosis and Management
- Echocardiography may be necessary to separate a prominent and exaggerated benign midsystolic murmur from one due to valvular disease, as noted in the 2008 focused update incorporated into the ACC/AHA 2006 guidelines for the management of patients with valvular heart disease 1.
- The goal of therapy is to manage the symptoms and signs of hyperthyroidism, including the cardiac manifestations, and to restore euthyroidism, which typically leads to the resolution of the murmurs.
From the Research
Hyperthyroidism and Murmurs
There is no direct evidence in the provided studies that specifically addresses the type of murmurs associated with hyperthyroidism.
Cardiovascular Manifestations
However, the studies do mention the impact of hyperthyroidism on the cardiovascular system, including:
- Hypertension 2
- Tachycardia 2 These cardiovascular manifestations can be treated with beta blockers 2.
Treatment of Hyperthyroidism
The treatment options for hyperthyroidism include:
- Anti-thyroid medications (methimazole and propylthiouracil) 3, 4, 5, 6
- Radioactive iodine ablation of the thyroid gland 2, 3
- Surgical thyroidectomy 2, 3
Murmurs and Hyperthyroidism
Although the studies do not directly address the type of murmurs associated with hyperthyroidism, it can be inferred that the cardiovascular manifestations of hyperthyroidism may lead to murmurs. However, there is no specific evidence to support this claim.