BACKGROUND: Left ventricular dyssynchrony is a frequently observed feature in patients with heart failure and is recognized as important predictor of poor outcome if left untreated. Cardiac resynchronization therapy (CRT) is an important treatment for patients with congestive heart failure and ventricular dyssynchrony, but response to CRT is highly variable. We sought to evaluate change in ventricular dyssynchrony after treatment of heart failure. METHODS: 21 patients with severe heart failure (left ventricular ejection fraction <35%), pulmonary edema (NYHA class 3 or 4) and regular sinus rhythm were studied. Patients with atrial fibrillation were excluded. Intraventricular and interventricular dyssynchrony were evaluated at admission(on pulmonaey edema) and discharge (off pulmonary edema) by echocardiography. RESULTS: Intraventricular dyssynchrony was reduced significantly after recovery of pulmonary edema (p<0.05). However, the interventricular dyssynchrony (Doppler and M-mode) was not statistically significantly different (Table 1). CONCLUSIONS: Intraventricular dyssynchrony correlates with severity of pulmonary edema in severe heart failure.