Abstract 2419: The Presence of Q Waves, QRS Fragmentation or QRS Duration Does Not Correlate with Scar Volume in Patients with Ischemic Cardiomyopathy.
Background. Recent studies have suggested that scar volume is one of the predictors of ICD utilization. We hypothesized that noninvasive ECG predictors of myocardial scar (number of leads with Q waves and/or fragmented QRS complexes, fQRS) would correlate with infarct size and could predict patients with a depressed ejection fraction that would be the most likely to benefit from imaging scar volume.
Methods. Patients with ischemic cardiomyopathy eligible for an ICD for the primary prevention of sudden death underwent PET imaging (n=78). Scar volume (% LV) was quantified from 18FDG uptake during insulin stimulation and 13N-ammonia flow using a validated algorithm (MyoPC, Ottawa Heart Institute). Pathologic Q waves and fQRS (RSR morphology or notching in R or S waves) on the 12-lead ECG were assessed by consensus of three blinded readers.
Results. Subjects were 67 ± 12 years of age and 87% male. Average ejection fraction was 28 ± 10%. Myocardial scar encompassed 17.1 ± 7.3% of the left ventricle, with a very wide range among subjects (1.9 to 34.4%). In patients with a QRS duration <120 msec (n=47), there was very poor correlation between scar volume and the number of leads with Q waves, fQRS or both (R2=0.01– 0.06, Table⇓). Furthermore, patients with a wide QRS (>120 msec) did not have an increase in scar volume (Table⇓).
Conclusions. These results indicate that 1.) The volume of scar varies widely in patients with ischemic cardiomyopathy that are eligible to receive an ICD for primary prevention and 2.) Infarct volume is independent of electrocardiographic indices of scar. Thus, imaging is necessary to stratify risk for SCD as a function of scar volume.