Effect of implantable cardioverter defibrillator implantation on frontal QRS-T angle

The frontal plane QRS-T [f(QRS-T)] angle refers to the mean difference between the depolarization and repolarization vectors and can easily be measured by digital electrocardiography (ECG). Pacemaker leads can cause fibrosis of the myocardium adjacent to the electrode-tissue interface. We aimed to evaluate whether a right ventricular implantable cardioverter-defibrillator (ICD) lead modifies the f(QRS-T) angle in patients with systolic heart failure (HF).

We prospectively analyzed 101 systolic HF patients who underwent single-lead ICD implantation. The f(QRS) angle before and after ICD implantation was compared with the Wilcoxon signed-rank test.

No significant difference in the f(QRS-T) angle was observed before and 6 months after ICD implantation (89.5° ± 97.8° vs. 93.0° ± 90.3°, p=0.211).

Histopathological studies showed that the irritating effect of ICD leads may cause fibrosis and scar tissue. However, we found that fibrosis and scar tissue did not affect the f(QRS-T) angle, which suggests that these pathologies may not have clinical significance. Further studies on the f(QRS-T) angle are warranted to understand its clinical significance in ICD-induced local fibrosis.