Myxedema Heart and Pseudotamponade

Abstract

Context: Thyroid hormone plays a critical role in cardiovascular function. Severe hypothyroidism can be associated with "myxedema heart" characterized by relative bradycardia and pericardial effusion. Effusions associated with severe hypothyroidism can be large. Despite the large volume of effusions, tamponade is not a common consequence. However, with the incorporation of echocardiography into routine practice for evaluation of effusion, echocardiographic findings suggestive of clinical tamponade occur frequently.

Case description: We report a series of 3 patients with large pericardial effusions secondary to severe hypothyroidism. These cases serve to demonstrate the discordance between echocardiographic signs consistent with tamponade with a patient's stable clinical hemodynamics. We also report the development of bronchial obstruction, a rare complication of a large effusion due to severe hypothyroidism.

Conclusions: While pericardial effusion associated with severe hypothyroidism has been described for decades, the echocardiographic findings may be less well known and may lead to unnecessary downstream testing or invasive management. We use our case series to facilitate a summary of what is known about the epidemiology, mechanism and physiology, and expected outcomes of myxedema associated pericardial effusion. Finally, in the setting of current paucity of clinical guidelines, we aim to familiarize clinicians with the phenomenon of pseudotamponade and suggest management strategies for myxedema associated pericardial effusion to guide clinicians to use conservative medical management in majority of cases.

Keywords: Hashimoto’s Disease; bradycardia; hypothyroidism; pericardial effusion.

Figure 1.

Lead II ECG findings on admission demonstrating findings consistent with myxedema heart. 1a (Case 1) demonstrates sinus bradycardia with flattened t waves; 1b (Case 2) and 1c (Case 3) with low voltage and T-wave flattening.

Figure 2.

Case 3 transthoracic echocardiogram, subxiphoid view, demonstrating large pericardial effusion with RV collapse during diastole.

Figure 3.

Case 3 axial computed tomographam demonstrating large pericardial effusion (arrowhead) causing narrowing of distal left mainstem bronchus.

Figure 4.

Pericardial effusion management in a hypothyroid patient. ŧ Echocardiographic findings of IVC plethora due to increased right atrial pressure and RA and RV diastolic collapse; respiratory variation of diastolic flow across the mitral valve may be present in the absence of hemodynamic compromise consistent with pseudotamponade. ˠ Findings on ECG consistent with myxedema heart include low voltage, flattened or inverted T waves, relative bradycardia, prolongation of QTc, and ±electrical alternans. *Initial dose of levothyroxine dependent on clinical severity of hypothyroidism and history/suspicion of cardiac comorbidities.