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Pattern Breaks on the Surface ECG: Can We Anticipate a Long Day Ahead?

In 1988, Miller et al.1 reported their experience with the correlation between 12-lead electrocardiograms (ECG) and endocardial sites of ventricular tachycardia (VT) origin in patients with coronary artery disease. In this series of 182 VTs in 108 patients, they noted numerous precordial transition patterns, one of which was a “regression/growth” pattern, with loss of R waves in the mid-precordial leads and then “regrowth” in the left precordial leads during right bundle branch block morphology VT. Limited additional clinical research has been published on precordial ECG pattern breaks in structural heart disease over the past 29 years. In the idiopathic VT literature, abrupt changes have been described in the LV summit but also on the opposite surface of the heart in the cardiac crux.2-6 Therefore, it appears that PVCs/VT arising from the basal aspect of the interventricular sulcus are prone to these pattern breaks whether anterior or posterior (Fig. 1). In the current issue, Hiyashi et al.7 report their retrospective experience with outflow premature ventricular contractions (PVC)/VT demonstrating a pattern break in standard ECG lead V2. Loss of R wave amplitude in V2 relative to V1 and V3 correlated with an origin in close proximity to the left anterior descending artery (LAD) in 12 out of 130 patients in their experience with left bundle branch (LBBB) morphology PVCs. These PVCs demonstrated earliest sites of activation in four related anatomic regions, all with close proximity to the anterior interventricular sulcus: anteroseptal right ventricular outflow tract (RVOT), left coronary cusp (LCC), coronary venous system (anterior interventricular vein), and epicardium. The overall ablation success rate was lower than outflow sites of origin not associated with this ECG pattern (58% vs. 89%, P = 0.0125). Proximity to the left anterior descending (LAD) artery was a major limitation to success in these cases. The authors, in describing their experience and findings, provide a number of valuable insights: