LAUSR

Left ventricle–only pacing with fusion of intrinsic right bundle branch activation and automatic A-V interval programming could accommodate electrical dyssynchrony of left anterior hemiblock. Introduction Cardiac resynchronization therapy (CRT) improves cardiac function by correcting electrical dyssynchrony in patients with symptomatic heart failure (HF). However, current guidelines focus on QRS interval alone with respect to electrical dyssynchrony. We implanted CRT in a patient with a QRS interval of 126 ms with left anterior hemiblock because a temporary pacing study before CRT showed correction of left anterior hemiblock with hemodynamic improvement via pacing at the electrically delayed left anterior site alone. The patient’s HF symptoms improved from New York Heart Association (NYHA) class III to I with left ventricular (LV) reverse remodeling. A left anterior hemiblock is another category of electrical dyssynchrony, and the current new CRT system can accommodate to correct individual electrical dyssynchrony. Thus, patients with HF and left anterior hemiblock can be suitable candidates for CRT. CRT is a well-established treatment for symptomatic HF, depressed left ventricular ejection fraction (LVEF), and electrical dyssynchrony. Current guidelines support CRT use in patients with prolonged QRS intervals; however, its use is not recommended in patients with narrow or slightly prolonged QRS intervals (,130 ms). Electrical dyssynchrony can be evaluated using the QRS duration and QRS axis. This report presents a case of QRS axis deviation with a QRS interval of ,130 ms and a left anterior hemiblock that was treated with CRT.