PURPOSE: Prolonged QT dispersion (QTd) found in acute ischemia and during the early post infarction period is associated with an increased incidence of ventricular arrhythmias. Corrected QT (QTc) interval and QTd decreases post reperfusion with primary percutaneous coronary intervention(PPCI) and during recovery from acute myocardial infarction (AMI). However, the time taken for normalization of QTc and decrease in QTd post PPCI and its relationship to in-hospital and long term events have not been elucidated so far.
METHODS: In this retrospective study, we reviewed the medical charts and electronic records of 52 consecutive patients admitted with AMI from January 2006 to December 2006. 14 patients were excluded with Bundle Branch Block (n=10), Complete Heart Block (n=2), and Atrial Fibrillation (n=2). The changes in QTc and QTd were monitored from time of admission to 24 hours post PCI. 38 patients were followed for in-hospital events (ventricular ectopic beats, non-sustained and sustained ventricular tachycardia, ventricular fibrillation, and sudden cardiac death), and long-term events (death, ventricular arrhythmias, Congestive Heart Failure and re-infarction) for six months. Fisher's exact test was used to analyze categorical data.
RESULTS: Amongst the 20 patients with in-hospital events, QTc remained prolonged in 16 (p=0.27) and QTd in 16 patients (p=0.004) at 24 hours post PCI. Six patients were lost to follow-up. Five patients had long-term events within the following six months(two died, two had reinfarction, one readmitted with congestive heart failure). All five had persistently prolonged QTc (p=ns) and four had prolonged QTd (p=ns).
CONCLUSION: In-hospital events were more prevalent in patients with a persistently elevated QTd 24 hours post PPCI for AMI. Though statistically insignificant, patients with persistently prolonged QTc and QTd had higher long-term events.
CLINICAL IMPLICATIONS: Increase in QTd is an electrocardiographic measure of ventricular repolarization and also a risk marker for ventricular tachyarrhythmia. In patients with AMI undergoing PCI, monitoring the time taken for normalization of the QTc and QTd may be helpful in predicting the short and long term complications. Larger studies are needed for further validation.
DISCLOSURE: Anuj Agarwal, None.