Electrophysiological Twisting: Electrical Alternans in Congenital Dilated Cardiomyopathy.

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 …