QT Dispersion as Marker of Risk in Patients Awaiting Heart Transplantation

Objectives. The objectives of this study were to determine whether signal-averaged electrocardiogram (SAECG) or measurement of interlead variability of QT intervals on an electrocardiogram (ECG) obtained at the time of wait-listing could provide prognostic value with respect to cardiac death during the waiting period. Background. Because heart transplantation is life-saving but limited resource, there remains an urgent need to identify those patients at greatest risk of dying while awaiting heart transplantation as part of the strategy to optimize the allocation of donor organs to those in greatest need. This study was undertaken to prospectively identify clinical, ECG or SAECG variables that might predict mortality during the waiting period. Methods. Of 108 consecutive patients referred for heart transplant evaluation, 80 were placed on waiting list, at which time standard 12-lead ECG and SAECG were recorded. In this cohort of 80 patients, QT dispersion was characterized from the 12-lead ECG as either the maximal–minimal QT interval (QTDISP) or as the coefficient of variation of all QT intervals (QTCV). Results. During the 25-month follow-up period (mean time on waiting list, 201 days), the mortality rate was 27%/year, divided equally between heart failure and sudden deaths. No clinical variable identified at entry predicted mortality. QTDISP and QTCV were strong mortality predictors, with 4.1-fold increase in mortality in patients with QTDISP >140 ms compared with those patients with QTDISP ≤140 ms (95% CI 1.1 to 14.9), whereas QTCV ≥9% also predicted 4.1-fold increased risk of death (95% CI 1.4 to 11.8). Although 88% of all SAECGs were abnormal, no patient with normal SAECG died suddenly during the waiting period. Conclusions. Indexes of QT dispersion provide means of stratifying patient’s risk of dying while awaiting heart transplantation and may help to establish priority on heart transplant waiting list.