Characteristics of the signal-averaged P wave in orthotopic heart transplant recipients.

UNLABELLED

Rejection remains the Achilles heel of orthotopic cardiac transplantation (OHT). Reliable noninvasive markers of rejection are desirable for timely therapy and to reduce risks and costs. Changes in atrial electrophysiology may precede ventricular changes during acute rejection. Although P wave duration in the signal-averaged ECG reflects atrial conduction, the feasibility of such measurement and the range of its values in OHT patients in absence of rejection is uncertain. This study compared the filtered P wave duration in 15 hypertensive OHT patients free of rejection with that in 15 age-matched hypertensive controls. All OHT patients had biatrial anastomoses. Two electrophysiologists interpreted the tracings independently. Three tracings (2 OHT, 1 control) could not be interpreted by either reader. An adequate P wave signal-averaged ECG was obtained in the remaining patients, despite the frequent presence of dissociated P waves (recipient and donor atria) on standard ECG in OHT patients. There was good interobserver agreement in the measurement of filtered P wave duration (r = 0.91; P < 0.0001).

CONCLUSIONS

The filtered P wave duration was significantly shorter in the OHT patients (112 +/- 15 ms versus 128 +/- 14 ms; P = 0.008). Filtered P wave duration can be measured in most OHT. Filtered P wave duration is shorter in OHT patients than in hypertensive controls, possibly as a result of the reduced mass of the truncated donor atria. Further studies are needed to determine whether the signal-averaged P wave can be useful to predict acute cardiac rejection.