Abstract 2310: Morphology of Exercise Induced Ventricular Arrhythmia Identifies Patients with Increased Myocardial Scar Burden
Background: It has been demonstrated that exercise induced ventricular arrhythmia (EIVA) is associated with greater likelihood of nuclear perfusion defects. Although fixed perfusion defects may be associated with scar related re-entry circuits, some EIVA, notably right ventricular outflow tract (RVOT) EIVA, is classically benign.
Methods: Data on 6,138 patients undergoing exercise nuclear perfusion imaging were prospectively collected. Exercise electrocardiograms of the 295 patients with complex EIVA (2 or more consecutive or multifocal ectopic ventricular beats) were reviewed for morphology, coupling interval, and tachycardia cycle length. Significant scar was defined as >5% total myocardium with a fixed defect on nuclear perfusion imaging.
Results: The percentage of patients with scar was greater in those with EIVA compared to those without (22.8% vs. 11.7%, p<0.0001), but presence of inducible ischemia was not different between groups (32.7% vs. 37.2%, p=0.08). Scar was present in 19.7% of those with single morphology of EIVA compared to 28.0% of those with multiple morphologies of EIVA (p<0.0001). Scar was present in only 8.6% of those with LBBB morphology EIVA compared to 30.5% of those with RBBB morphology EIVA (χ2 for trend, p<0.0001). In those with EIVA of suspected RVOT origin (LBBB morphology, inferiorly directed, precordial transition before V4), the prevalence of scar was 8.4%. Of those with EIVA, the presence of scar was associated with a longer coupling interval of the first beat (454±105 ms vs. 413±97 ms, p<0.0001) and longer tachycardia cycle length (381±113 ms vs. 330±83 ms, p<0.0001).
Conclusions: Complex EIVA is not associated with myocardium at risk but rather scar burden. Discrimination of EIVA morphology allows identification of a subset of patients with lower likelihood of scar. Both multiple morphologies and slower EIVA are associated with myocardial scar, consistent with the understanding of scar re-entry mechanisms. Further study is warranted to assess the relation of EIVA morphology to perfusion abnormalities and outcomes.