Electrocardiographic Markers and the Left Ventricular Ejection Fraction have Cumulative Effects on Risk of Sudden Cardiac Death.

OBJECTIVES: To assess potential improvement in SCD risk prediction by adding selected risk markers from the 12-lead ECG to measurement of the left ventricular ejection fraction (LVEF).

BACKGROUND: Novel strategies to improve risk stratification for sudden cardiac death (SCD) are needed. Given the modest odds associated with most individual risk markers, combining multiple markers may be a useful approach.

METHODS: From the ongoing Oregon Sudden Unexpected Death Study, SCD cases with pre-event LVEF available were compared to matched control subjects with coronary artery disease. Resting heart rate, QRS duration (QRSD), and JTc intervals were measured from archived ECGs prior and unrelated to the SCD event. Independent odds of SCD for individual and combined ECG markers were calculated.

RESULTS: SCD cases (n= 317; 67.9 ± 12.9 years) were more likely than controls (n=317; 67.9 ± 12.8 years) to have LVEF ≤ 35% (26% vs. 11%). Mean heart rate, QRSD, and JTc were significantly higher in cases (all p<0.0001). In adjusted analyses, higher heart rate [OR 2.6 (1.8 - 3.7)], QRSD [OR 1.5 (1.0 - 2.5)] and JTc [OR 2.3 (1.6 - 3.4)] were independently associated with SCD. When ECG markers were combined, SCD odds progressively increased with one [OR 3.4 (2.1 - 5.4)] and ≥ 2 elevated markers [OR 6.3 (3.3 - 12.1)]. Addition of ECG markers to an adjusted model with LVEF improved discrimination (C statistic 0.724 vs. 0.642) and net reclassification (by 22.7%) (p<0.0001).

CONCLUSIONS: Combining selected 12-lead ECG markers with LVEF improves SCD risk prediction, and warrants further investigation in prospective studies.