The effect of QRS duration in the diagnosis of LVH in complete right bundle branch block.

The difficulty in diagnosing LVH in the presence of CRBBB is presumably due to the Intraventricular Conduction Defect (IVCD). Since QRS duration reflects the degree of IVCD, the accuracy in diagnosis of LVH with CRBBB may depend on the severity of the conduction abnormality. Vandenberg et al evaluated several ECG criteria in the diagnosis of LVH in the presence of CRBBB but only four of these criteria had specificities ranging from 66-96% and sensitivities ranging from 27-68%, namely: 1) R in III + S in III 25mm; 2) R in AVL 12mm; 3) S in III + (R + S) in maximal precordial lead 30mm; 4) S in III + (R + S) 30mm + LAD. This study evaluated the applicability of these criteria in varying degrees of right bundle branch block. One hundred ninety-eight cases having CRBBB with QRS durations ranging from 0.12 to 0.16 milliseconds were studied. Forty-two percent (42%) had concommitant LVH while the remaining 58% did not. LV mass index was determined from echocardiograms using the PENN Method. Correlating each criterion with the data subgrouped as to the QRS duration (+LVH vs. -LVH, QRS = .12 - .14 vs. QRS .14), only criterion 3 was reliable in diagnosing LVH in the presence of CRBBB on the condition of a prolonged QRS duration of .14. All results were tabulated and analyzed using the Chi-square test.