A larger vectorcardiographic QRS area is associated with left bundle branch block and good prognosis in patients with cardiac resynchronization therapy.

Background: The association between the vectorcardiographic QRS area, bundle branch pattern and clinical long-term prognosis in patients who have undergone cardiac resynchronization therapy (CRT) has been unclear.

Methods: We enrolled 50 consecutive patients who underwent CRT. Vectorcardiograms were constructed from preprocedural digital 12-lead electrocardiograms using the inverse Dower method. The vectorcardiographic QRS area was defined as the root of the sum of the square in the integral between the ventricular deflection curve and the baseline from QRS beginning to end in leads X, Y, and Z. The primary endpoints were total mortality and admission due to heart failure.

Results: The vectorcardiographic QRS area in left bundle branch block (N = 13), right bundle branch block (N = 13), interventricular conduction delay (N = 11) and pacemaker rhythm (N = 13) were 218 ± 99, 97 ± 44, 90 ± 40, and 131 ± 58 μVs, respectively (ANOVA p < 0.001). During the mean follow-up period of 28 (2-86) months, 13 primary endpoints occurred. We divided patients into two groups: a large QRS area group (QRS area ≥114 μVs, N = 25) and a small QRS area group (QRS area <114 μVs, N = 25) by the median. The large QRS area group had a significantly lower rate of the primary endpoint compared with that of the small QRS area group (log rank 4.35, p = 0.037). The Cox regression analysis revealed that a QRS area <114 μVs was a significant predictor of the primary endpoint (HR 3.98, 95% CI 1.01-15.63, p = 0.048).

Conclusions: A larger preprocedural vectorcardiographic QRS area was associated with left bundle branch block and good prognosis in patients who underwent CRT.