[QT dispersion and myonecrosis after stent percutaneous coronary intervention]

QT dispersion (QTd) is the difference between the maximum and the minimum QT interval in the 12-lead ECG. There is currently no information on the relationship between QTd and creatine kinase (CK)-MB release in patients undergoing percutaneous coronary intervention (PCI).

Among 118 patients undergoing successful PCI stenting, QTd and corrected QTd (QTdc) were measured at standard 12-lead ECG before PCI and at 6 and 18 hours after PCI. The median of QTdc variation (deltaQTdc = baseline QTdc - QTdc at 6 hours) was 9.5 ms (range -48 / +89 ms). Patients were divided into two groups according to deltaQTdc: group A "recoverers" (deltaQTdc > 9.5 ms, n = 59, 50%), group B "non-recoverers" (deltaQTdc < 9.5 ms, n = 59, 50%). CK-MB release was compared in the two groups.

Eighty-three percent of patients were male, with mean age of 62 years (range 41-80 years). Unstable angina was present in 35% of cases, with similar distribution in the two groups. PCI was performed in 1.94 lesions/patient with the implantation of 1.6 stent/patient. Compared to baseline, a reduction in both QTc and QTdc was documented at 6 and 18 hours after PCI (p < 0.05). Periprocedural variations (CK-MB > 2 upper limit of normal) was detected in 4 patients (7%) of group A and 12 patients (20%) in group B (p = 0.06). Peak CK-MB release was significantly lower in group A (13 +/- 14.3 IU/l) compared to group B (23.2 +/- 35 IU/l, p < 0.05).

After successful coronary stenting there is a rapid normalization of QTd and QTdc. The lack of recovery of both QTd and QTdc is related to minor elevations of CK-MB and may therefore be further explored as a useful non-invasive marker of heterogeneous reperfusion after PCI.