Abstract 2122: ECG Quantification of Myocardial Scar in Cardiomyopathy Patients with or without Conduction Defects: Correlation with Cardiac Magnetic Resonance and Arrhythmogenesis
Background: Myocardial scarring from infarction (MI) or nonischemic fibrosis forms an arrhythmogenic substrate. The Selvester QRS-score estimates MI size by quantifying changes in Q-, R- and S-wave durations, amplitudes and morphologies from the 12-lead electrocardiogram (ECG). It provides 32 possible points with each point reflecting scarring of 3% of the left ventricle (LV). Although QRS scoring has been extensively validated for estimating MI scar size in the absence of ECG confounders, it has not been validated in patients with left ventricular hypertrophy (LVH), fascicular/bundle branch blocks or nonischemic scar. We assessed the hypotheses that
QRS-scores (modified for each conduction type) correctly identify and quantify both ischemic and nonischemic scar as compared to the reference standard of Cardiac Magnetic Resonance - Late Gadolinium Enhancement (CMR-LGE) and
QRS-estimated scar size is associated with inducible sustained monomorphic ventricular tachycardia (MVT) during electrophysiologic (EP) testing.
Methods and Results: A prospective 162 patient cohort with LV dysfunction (95 ischemic, 67 nonischemic) received 12-lead ECG and CMR-LGE before defibrillator (ICD) implantation for primary prevention of sudden cardiac death. QRS-scores correctly diagnosed CMR-scar presence with receiver operating characteristics (ROC) area under the curve (AUC)=0.91 and correlation for scar quantification of r=0.74, p<0.0001, for all patients. Performance within the LVH, bundle branch/fascicular block and nonischemic subgroups ranged from AUC 0.81– 0.94, r=0.60 – 0.80, p<0.001 for all. Of the 137 patients undergoing EP or device testing, 37/82 (45%) of ischemic and 7/55 (13%) of nonischemic patients had inducible MVT. For each 3 QRS point increase (9% LV scarring), the odds ratio for inducing MVT was 2.2 [95% CI: 1.5–3.2, p<0.001] for all patients; 1.7 [1.0 –2.7, p=0.04)] for ischemics; and 2.2 [1.0 –5.0, p=0.05] for nonischemics.
Conclusions: Compared to CMR, QRS-scores identify and quantify MI and nonischemic scar despite ECG confounders. Higher QRS-estimated scar size is associated with increased arrhythmogenic potential and warrants further study as a risk-stratifying tool for patients with left ventricular dysfunction.