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Exercise-induced ST elevation in patients with non-ischemic dilated cardiomyopathy and narrow QRS complexes: novel predictor of long-term prognosis from exercise testing.

BACKGROUND
The clinical significance and prevalence of exercise-induced ST elevation (ESTE) in non-ischemic dilated cardiomyopathy (NIDCM) patients are unknown.


METHODS AND RESULTS
We retrospectively examined 12-lead ECGs during cardiopulmonary exercise testing in 360 consecutive NIDCM patients (left ventricular ejection fraction (LVEF) <45%) with narrow QRS. ESTE was defined as ≥1.0mm ST (J-point) elevation compared with baseline. During long-term follow-up for major cardiac events (death, transplantation, or LV assist device implantation), ESTE was recognized in 50 patients (14%). They had much lower LVEF than patients without ESTE (20±7% vs. 27±7%, respectively, P<0.001), whereas the differences in peak VO2 (P=0.01) and VE/VCO2 slope (P=0.04) were relatively small. Major cardiac events occurred more frequently in patients with ESTE than in those without ESTE (39% vs. 12% at 48 months). Increased event rates were associated with low peak VO2 (<14ml·min(-1)·kg(-1)) in patients without ESTE (39% vs. 23%, P<0.05), but not in those with ESTE (50% vs. 62%, NS). Cox multivariate analysis revealed ESTE as the strongest independent prognosticator among exercise parameters (hazard ratio: 2.41 [95% confidence interval 1.03-5.63], P<0.05).


CONCLUSIONS
A substantial number of NIDCM patients exhibit ESTE, which indicates a poor prognosis. Low peak VO2 and ESTE may reflect different aspects of the pathophysiological processes that deteriorate heart failure.