QT Dispersion: A Predictor of Outcome Following Acute Neurologic Events
BACKGROUND: QT dispersion (QTD) reflects heterogeneity of myocardial repolarization, which is modulated by the central nervous system. Pervious studies have shown increased QTD to be a predictor of adverse outcome in various cardiac disease states. However, the central nervous system effects on QTD and its relation to functional outcomes have not been previously studied in patients with acute neurological events (NE). The objective of this study was to determine whether increased QTD is related to functional outcome in patients with cerebrovascular accidents (CVA) and transient ischemic attacks (TIA). METHODS: We studied 140 consecutive pts. aged 72±10 yrs. (48% male) admitted to our institution with NE from 1/98 to 4/98. QTD was calculated from admission EKG as the difference between maximum and minimum QT intervals. 120 pts. had interpretable EKGs with measurable QT intervals in at least 11 of 12 leads. Three separate functional scales (NIHSS, Barthel, and Rankin) were obtained on admission and discharge were recorded. RESULTS: QTD was higher in pts. with intracerebral hemorrhage as compared to CVA and TIA (70±15 vs. 53±27 vs. 48±31 msecs. p=0.03). Increased QTD was associated with lower functional outcome on all 3 scales (all p<0.05) and with higher mortality (p=0.02). QTD was higher in pts. with congestive heart failure (80±43 vs. 47±24 msecs. p=0.006) and carotid disease (59±32 vs. 46±27 msecs. p=0.045) as compared to those without. QTD was not associated with atrial fibrillation or coronary disease. All patients with TIA survived. On multivariate analysis, other independent predictors of poorer outcome were QTD (OR 1.35, 95% CI 1.08–1.68) and a trend towards age (OR 1.07, 95% CI 0.99–1.16). On age-adjusted logistic regression, mortality increased by an OR 1.28, 95% (CI 1.02–1.61) for every 10 msec increase in QTD. CONCLUSION: QTD is an independent predictor of functional outcome and mortality following acute neurological events. In this setting, QTD reflects acute neurological injury as well as underlying heart disease. The mechanism of these findings merits further study.