Temporal repolarization inhomogeneity and reperfusion arrhythmias in patients undergoing successful primary percutaneous coronary intervention for acute ST-segment elevation myocardial infarction: impact of admission troponin T.

BACKGROUND: The presence of admission cardiac troponin-T (cTnT) is a means of identifying a high-risk subgroup in patients with acute ST-segment elevation myocardial infarction (AMI). Because a substantial number of these patients has malignant ventricular arrhythmias, we hypothesized that there is a relation between cTnT status on admission and inhomogeneity of ventricular repolarization, and we tested this assumption in the setting of primary percutaneous coronary intervention (PCI).

METHODS: Temporal fluctuations of ventricular repolarization were studied during and after primary PCI (Thrombolysis In Myocardial Infarction [TIMI] 2 and 3) in 94 consecutive patients with a first AMI by continuous beat-to-beat QT-interval measurement, performed with Holter monitoring initiated on admission. Troponin-T levels on admission were >0.1 ng/mL in 53 patients (cTnT+) and <0.1 ng/mL in 41 patients (cTnT-). There were no significant differences in baseline clinical characteristics between the groups.

RESULTS: The incidence of severe reperfusion arrhythmias (RAs) was significantly higher in patients in the cTnT+ group within the first 2 hours after recanalization. The course of the QT interval revealed a significant decline (P <.001) after recanalization of the infarcted vessel within 10 hours in both groups; however, hourly values were significantly lower and normalization of the QT parameters was more rapid in patients in the cTnT- group than patients in the cTnT+ in this period (QTc, 438.5 +/- 28.3 ms vs 449.3 +/- 35.3 ms [hour 1, P <.01]; 413.6 +/- 35.8 ms vs 420.1 +/- 39.2 ms [hour 10, P <.05]). QT-interval variability also significantly declined within 4 hours after PCI (P <.001), and likewise, patients in the cTnT- group exhibited lower values in this period (QTSD, 29.7 +/- 6.8 ms vs 33.5 +/- 10.5 ms [hour 1, P <.01]; 23.0 +/- 6.1 ms vs 25.9 +/- 7.5 ms [hour 4, P <.01]).

CONCLUSIONS: Positivity of cTnT on admission is associated with a significantly higher temporal inhomogeneity of ventricular repolarization and a higher incidence of malignant RAs, which suggests more advanced microvascular injury. Early successful primary PCI ultimately results in a significant recovery of parameters of QT interval and mean RR interval in all patients, although it was significantly delayed in patients in the cTnT+ group.