QT dispersion as a predictor of long-term mortality in patients with acutemyocardial infarction and clinical evidence of heart failure

Background QT interval dispersion is a marker of inhomogeneous ventricular repolarization, and therefore has the potential to predict re-entry arrhyth mias. Following acute myocardial infarction, increased QT dispersion has be en associated with a higher risk of ventricular arrhythmias. However, wheth er or not QT dispersion predicts prognosis post-acute myocardial infarction is not clear. We addressed this issue by analysing the AIREX study registr y. Methods AIREX was a follow-up study of 603 post-acute myocardial infarction patients who exhibited clinical signs of heart failure and were randomly a llocated to ramipril or placebo. An interpretable 12-lead ECG obtained betw een day 0 and day 9 after the index infarction (median time 2 days) was ava ilable in 501 patients. We examined whether QT dispersion was a predictor o f all-cause mortality in the AIREX study registry (mean follow-up 6 years). Results QT dispersion measurements were significantly increased in patients who subsequently died (QT dispersion: 92.0 +/- 38.5ms vs 82.7 +/- 34.3ms, P=0.005; rate corrected QT dispersion: 105.7 +/- 427 ms vs 93.1 +/- 35.9 ms , P<0001). Univariate analysis showed that QT dispersion was a predictor of all-cause mortality risk (QT dispersion: hazard ratio per 10ms 1.05, [95% CI 1.02 to 1.09], P=0.004; rate corrected QT dispersion: 1.07 [1.03 to 1.10 ], P<0001); an increase of 10 ms added a 5-7% relative risk of death. QT di spersion remained an independent predictor of all-cause mortality risk on m ultivariate analysis (QT dispersion: 1.05 [1.01 to 1.09], P=0.027; rate cor rected QT dispersion: 1.05 [1.01 to 1.09], P=0.022). Conclusion QT dispersion, measured from a routine 12-lead ECG following acu te myocardial infarction complicated by heart failure provides independent information regarding the probability of long-term survival. However, the l ow sensitivity of this electrocardiographic marker limits its usefulness fo r risk stratification if used in isolation.