Electrical Alternans in Congenital Dilated Cardiomyopathy
- mitral valve
- ventricular dysfunction
A male infant weighing 3.5 kg with unremarkable cardiac examination developed mild oxygen desaturation. ECG showed sinus rhythm with low voltages (Figure [A]). Echocardiogram demonstrated severely dilated and echogenic left ventricle with markedly depressed biventricular systolic function (Movie I in the Data Supplement; Figure [B and C]). The late opening of mitral valve only with atrial contraction (A wave; Figure [C and H]) suggested significant diastolic dysfunction. He developed alternating normal and abnormal QRS complexes in association with hypokalemia (serum potassium 2.3–2.9 mg/dL), generating systolic blood pressure only with normal beat (Figure [D and E]). M-mode echocardiographic images showed minimal and late systolic opening of aortic valve during abnormal systole (Figure [F], red arrow) without any cardiac output (Figure [G]) suggesting ineffective left ventricular contractility. The following diastole demonstrated earlier and prolonged mitral valve opening with distinct E and A waves (Figure [H]), resulting in adequate cardiac output with next normal systole (Figure [F and G]). His rhythm normalized after potassium supplementation. This rare phenomenon of electric alternans involving both QRS amplitude and ST segment in severely dysfunctional myocardium in this neonate occurred presumably because of ineffective calcium cycling, likely unmasked by hypokalemia.1 Isolated repolarization (T wave) alternans can occur in congenital heart diseases, channelopathies, cardiomyopathy, and also in normal hearts at younger age and higher heart rate.2,3 This case probably reflects the severe end of the spectrum of electric alternans occurring simultaneously in both depolarization (QRS) and repolarization (ST-T wave) phase.
- Received December 16, 2016.
- Accepted January 5, 2016.
- © 2017 American Heart Association, Inc.