on December 2, 2008
Published online before print December 2, 2008, doi: 10.1161/CIRCEP.108.798660
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Original Article |
ECG Quantification of Myocardial Scar in Cardiomyopathy Patients with or without Conduction Defects: Correlation with Cardiac Magnetic Resonance and Arrhythmogenesis
1 Johns Hopkins Medical Inst., Baltimore, MD; Duke , Durham, NC; Lund University Hospital, Sweden;
2 Memorial Hospital Research Center, Long Beach, CA;
3 Johns Hopkins Medical Inst., Baltimore, MD;
4 Lund University Hospital, Sweden;
5 Cedars-Sinai Heart Institute, Los Angeles, CA;
6 Duke Clinical Research Institute, Durham, NC
7 E-mail: kwu{at}jhmi.edu
Background—Myocardial scarring from infarction (MI) or nonischemic fibrosis forms an arrhythmogenic substrate. The Selvester QRS-score has been extensively validated for estimating MI scar size in the absence of ECG confounders, but has not been tested to quantify scar in patients with hypertrophy, bundle branch/fascicular blocks or nonischemic cardiomyopathy. We assessed the hypotheses that (1) QRS-scores (modified for each ECG confounder) correctly identify and quantify scar in ischemic and nonischemic patients as compared to the reference standard of Cardiac Magnetic Resonance-Late Gadolinium Enhancement (CMR-LGE) and (2) QRS-estimated scar size predicts inducible sustained monomorphic ventricular tachycardia (MVT) during electrophysiologic (EP) testing.
Methods and Results—162 patients with left ventricular ejection fraction 
35% (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 area under the curve (AUC)=0.91 and correlation for scar quantification of r=0.74, p<0.0001, for all patients. Performance within hypertrophy, conduction defect and nonischemic subgroups ranged from AUC 0.81-0.94, r=0.60-0.80, p<0.001 for all. Among the 137 patients undergoing EP or device testing, each 3 point QRS-score increase (9% LV scarring) was associated with an odds ratio for inducing MVT of 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—QRS-scores identify and quantify scar in ischemic and nonischemic cardiomyopathy patients despite ECG confounders. Higher QRS-estimated scar size is associated with increased arrhythmogenesis and warrants further study as a risk-stratifying tool.
Key Words: arrhythmia • cardiomyopathy • electrocardiography • imaging • infarction
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