Dos the presence of hibernating myocardium in patients with impaired left ventricular contraction affect QT dispersion?

Background Hibernating myocardium is associated with increased cardiovascul ar events. Increased QT dispersion on the surface electrocardiogram is a ma rker For serious ventricular arrhythmias. In this study, we determine wheth er hibernating myocardium is associated with increased QT dispersion in pat ients with coronary artery disease and impaired left ventricular contractio n. Methods Positron emission tomography with N-13-ammonia and F-18-fluorodeoxy glucose determined the presence of metabolic-perfusion mismatch defect. QT dispersion was measured by means of a digitizing tablet with validated soft ware. QT intervals were measured on two separate occasions by two investiga tors blinded to the result of the positron emission tomography scans. Results Forty-two patients with impaired left ventricular contraction were studied. They were divided into two groups: group A was made vp of patients with mismatch defects (n = 26) and group B was made vp of patients with no mismatch defects (n = 16). The mean (SD) QT dispersion measurements were 6 1.7 +/- 29.8 ms and 70 +/- 24.6 ms for groups A and B, respectively (not si gnificant). When the patients were divided according to the dominant viabil ity status of the impaired myocardial segment, a similar result was found. The patients whose impaired myocardium was dominantly hibernating (n = 19) had a mean QT dispersion of 66.4 +/- 31.9 ms compared with 63.6 +/- 24.8 ms in the patients whose impaired myocardium was mainly scarred (not signific ant). Conclusions QT dispersion is not affected by the presence of hibernating my ocardium and is therefore not clinically useful in identifying patients wit h this phenomenon. This is in contrast with recent reports by other groups and calls for further investigation of this dichotomy.