Comparison of microvolt T-wave alternans measurements using atrial pacing compared to atropine administration

Background: Microvolt T-wave alternans (MTWA) has been associated with malignant ventricular arrhythmias in patients (pts) with structural heart disease. MTWA has been shown to be a strong heart rate-dependent arrhythmia marker. However, in clinical practice some pts in which MTWA should be assessed are unable to perform physical exercise to increase heart rate due to various reasons.
Methods: In this study, we investigated the feasibility of noninvasive MTWA measurement by using intravenous atropine to increase heart rate and compared the results to MTWA measurement by right atrial (RA) pacing during electrophysiologic (EP) study in 27 consecutive pts (53 ± 14 years; nine women). Determining the arrhythmia event-rate, a follow-up of 18 months was performed in all pts.
Results: Using atropine, five pts (18%) did not reach the target heart rate (105 bpm). In the remaining group of pts, concordant results for MTWA assessment could be found in 21 pts (96%). Comparing MTWA positive tests there were slightly higher amplitudes using right atrial (RA) pacing than atropine (7.0 ± 2.3μV vs 6.3 ± 2.2μV, P = 0.03; r = 0.97). During follow-up all pts with a positive MTWA test had documented ventricular arrhythmias. There were no arrhythmic events in the MTWA negative group.
Conclusion: Whenever target heart rate for MTWA evaluation is obtained by intravenous atropine, the results are comparable to RA pacing. In using atropine there has been observed no pharmacologically influenced increase of MTWA voltage leading to false positive MTWA results. Therefore the use of atropine can be recommended as a safe, non-invasive, and reliable method for MTWA assessment.