Dyssynchrony may be Atrioventricular: Between atrial and ventricular contraction Interventricular: Between left and right ventricular contraction Intraventricular: Between different segments of left ventricular contraction Patients at risk for dyssynchrony include those with the following: Ischemic or nonischemic dilated cardiomyopathy Prolonged QRS interval (≥ 130 millisecond) particularly in the form of typical left bundle branch block Left ventricular end-diastolic dimension ≥ 55 mm Left ventricular ejection fraction ≤ 35% in sinus rhythm Cardiac dyssynchrony can be suspected based on electrocardiogram (ECG) parameters (eg, left bundle branch block) and advanced echocardiography techniques (eg, tissue Doppler index, strain rate).