Defective recovery of QT dispersion predicts late cardiac mortality after percutaneous coronary intervention

BACKGROUND: It has been suggested that corrected QT dispersion (cQTD) provides a measure of repolarisation inhomogeneity; however, the existence of a relationship between cQTD and cardiac outcomes is controversial. OBJECTIVE: To assess whether changes in cQTD following percutaneous coronary intervention (PCI) predict long-term survival. DESIGN: Prospective observational study. SETTING: Single tertiary care centre. Main outcome measures Cardiac mortality. PATIENTS: 612 patients had a 12-lead ECG recorded before and 6 h after PCI, and were followed-up for 49 ± 10 months. RESULTS: PCI was associated with a significant overall reduction of cQTD at 6 h versus baseline (p < 0.001); a reduction in cQTD occurred in 343 patients (56%). During the follow-up, 46 deaths (7.5%) were recorded, 21 of which for non-cardiac and 25 for cardiac causes. At Cox regression analysis, a reduced ΔcQTD (cQTD baseline - 6 h) was an independent predictor of cardiac mortality (HR = 1.497; 95% CI 1.081 to 2.075 for each 20 ms decrease; p = 0.015), together with age (HR = 1.672; 95% CI 1.039 to 2.691 per 10 years increase; p = 0.034), diabetes (HR = 2.622; 95% CI 1.112 to 6.184; p=0.028), peak CK-MB (HR = 1.798; 95% CI 1.063 to 3.039 per each unit increase over normal level; p = 0.029), three-vessel coronary artery disease (HR=3.626; 95% CI 1.079 to 12.187; p = 0.037) and the number of treated lesions (HR=2.066; 95% CI 1.208 to 3.532; p = 0.008). Patients in the lowest tertile of ΔcQTD and having a post-procedural increase of CK-MB had a considerably higher cardiac mortality than the remaining population (14.6 vs 2.4%, p < 0.001). CONCLUSIONS: cQTD decreases after PCI. A defective cQTD recovery, suggesting the persistence of repolarisation inhomogeneities, predicts long-term cardiac mortality.