What cardiac findings are associated with hypothyroidism (underactive Thyroid (thyroid gland))?

From the Guidelines

In a patient with hypothyroidism, cardiac examination may reveal bradycardia, diastolic hypertension, and decreased cardiac output, which are the hallmark findings of this condition. The pulse may feel weak and the blood pressure could show diastolic hypertension. Heart sounds might be diminished with reduced intensity, and a pericardial effusion may produce muffled heart sounds if present. The examiner might also detect a decreased cardiac output manifested by cool extremities and delayed capillary refill. In severe cases of hypothyroidism (myxedema), cardiomegaly may be present due to dilated cardiomyopathy. These cardiac findings occur because thyroid hormones significantly influence cardiac function by regulating heart rate, contractility, and vascular resistance. Reduced thyroid hormone levels lead to decreased beta-adrenergic receptor sensitivity, impaired calcium handling in cardiac myocytes, and increased peripheral vascular resistance, collectively resulting in the characteristic cardiovascular manifestations of hypothyroidism, as noted in the study by 1.

Some key points to consider in the cardiac examination of a patient with hypothyroidism include:

• Bradycardia, which is a slow heart rate, typically less than 60 beats per minute
• Diastolic hypertension, which is an increase in the diastolic blood pressure
• Decreased cardiac output, which can manifest as cool extremities and delayed capillary refill
• Pericardial effusion, which can produce muffled heart sounds
• Cardiomegaly, which can be present in severe cases of hypothyroidism (myxedema)

The study by 1 highlights the importance of considering thyroid function in patients with cardiovascular disease, as thyroid hormones play a significant role in regulating cardiac function. Additionally, the study by 1 notes that hypothyroidism can lead to myocardial fibrosis, impaired blood flow, and maladaptive changes in myocyte shape, which can contribute to the development of cardiovascular disease.

Overall, the cardiac findings in a patient with hypothyroidism are primarily related to the decreased levels of thyroid hormones, which can lead to decreased cardiac contractility, increased peripheral vascular resistance, and decreased cardiac output. The most important consideration in the management of these patients is to recognize the potential for cardiovascular disease and to initiate appropriate treatment to improve cardiac function and reduce the risk of morbidity and mortality, as noted in the study by 1.

From the Research

Cardiac Findings in Hypothyroidism

The cardiac findings in a patient with hypothyroidism can be summarized as follows:

• ECG changes:
  • Sinus bradycardia 2
  • Prolonged QTc interval 2
  • Changes in the morphology of the T-wave 2
  • QRS duration 2
  • Low voltage complexes 2
• Echocardiography changes:
  • Diastolic dysfunction 2, 3, 4
  • Asymmetrical septal hypertrophy 2
  • Pericardial effusion 2, 5
• Other cardiac findings:
  • Increased risk for atherosclerotic cardiovascular disease 3
  • Heart failure 6, 3
  • Diastolic hypertension 6
  • Atherosclerosis 6
  • Coronary artery disease (CAD) 6
  • Decreased insulin sensitivity 6
  • Impaired myocardial contractility 4, 5
  • Altered endothelial function 5
  • Blunted response to catecholamines 5

Clinical Manifestations

The clinical manifestations of hypothyroidism can include:

• Fatiguability 2
• Dyspnea 2
• Weight gain 2
• Lower limb swelling 2
• Bradycardia 2
• Pallor 2
• Tiredness or weakness 2
• Exertional chest pain 6