Changes in QT dispersion after thrombolysis for stroke.

BACKGROUND: QT dispersion (QTD) reflects heterogeneity of myocardial repolarization, which is modulated by the central nervous system. Although largely studied in patients with cardiovascular disease, QTD is increased in acute stroke and this finding is an independent predictor of functional outcome and mortality following acute neurological events.

HYPOTHESIS: The hypothesis of this study was to determine whether changes in QTD in patients presenting with ischemic stroke parallel changes in neurologic function.

METHODS: We retrospectively studied 30 consecutive patients (76+/-9 years, 50% male) who received thrombolytic therapy for acute ischemic stroke between September 1996 and August 2002, and had multiple electrocardiograms (ECGs). QTD was calculated from the admission ECG and the last available ECG (median 3 days) during hospital admission as the absolute difference between the maximum and minimum QT intervals in at least 11 of 12 leads. The National Institute of Health Stroke Scale (NIHSS) was used to assess neurological status on admission and discharge. DeltaQTD was calculated as the absolute difference between QTD measured on admission and on the last available ECG. Absolute changes in heart rate corrected QTD (DeltaQTDc) and NIHSS scores (DeltaNIHSS) were also calculated.

RESULTS: DeltaQTD was significantly higher in the 27% of patients who died as compared to the survivors (44+/-26 ms vs. -2+/-21 ms, p<.001). DeltaNIHSS correlated directly with DeltaQTD (r=0.57, p<0.001) and with DeltaQTDc (r=0.60, p<0.001). The NIHSS score changed in the same direction 3.1 units (95% CI: 2.0, 4.2) for every 10 ms change in QTD.

CONCLUSION: DeltaQTD are associated with changes in neurological function in patients treated with thrombolytic therapy for acute ischemic stroke.