QRS duration in isolated left bundle branch block: a marker of ventricular remodling and septal hypoperfusion

Isolated left bundle branch block [LBBB] per se may compromise cardiac mechanics and perfusion; this may contribute to the unfavorable outcome of such patients. The relation of QRS duration in isolated LBBB with cardiac function and perfusion is unknown. So, we sought to evaluate the left ventricular [LV] function and myocardial perfusion in isolated LBBB in relation to QRS duration. The study included 30 patients with isolated LBBB and 10 age and gender matched subjects without conduction delay. All study population had normal coronary angiogram. LBBB patients were divided into group I [17 patients] with 120/=140 msec. LV end diastolic dimension [LVED], LV end systolic dimension [LVES], septal wall thickness [SWT], posterior wall thickness [PWT] and LV ejection fraction [LVEF] were detected by echocardiography and myocardial perfusion was assessed by Thallium-201 [[201]Th] scintigraphy. LV remodeling [as detected from increased LVSD and PWT and decreased LVEF] and septal hypoperfusion [as detected by 201Th scintigraphy] were more frequent in group II [patients with QRS>140 msec]. QRS as it correlated positively with LVES [r 0.79, p<0.001] and negatively with LVEF [r-0.56, p<0.002], it also showed good agreement with myocardial perfusion imaging, the prolonged QRS the more frequent septal hypoperfusion. Moreover, there was a relation between cardiac function and myocardial perfusion in LBBB patients as these patients with perfusion defects showed increased LVES and SWT and decreased LVEF versus those without perfusion defects suggesting that there is link between cardiac function and myocardial perfusion in LBBB. Electrocardiography is commonly used as the first assessment tool for possible cardiac disease. QRS duration in patients with isolated LBBB is closely related to LV remodeling and septal hypoperfusion