Heart rate variability and microvolt T wave alternans changes during ajmaline test may predict prognosis in Brugada syndrome

PurposeDrug-induced type I Brugada syndrome (BrS) is associated with a ventricular arrhythmia (VA) rate of 1 case per 100 person-years. This study aims to evaluate changes in electrocardiographic (ECG) parameters such as microvolt T wave alternans (mTWA) and heart rate variability (HRV) at baseline and during ajmaline testing for BrS diagnosis.MethodsConsecutive patients diagnosed with BrS during ajmaline testing with 5-year follow-up were included in this study. For comparison, a negative ajmaline control group and an isoproterenol control group were also included. ECG recordings during ajmaline or isoproterenol test were divided in two timeframes from which ECG parameters were calculated: a 5-min baseline timeframe and a 5-min drug timeframe.ResultsA total of 308 patients with BrS were included, 22 (0.7%) of which suffered VAs during follow-up. One hundred patients were included in both isoproterenol and negative ajmaline control groups. At baseline, there was no difference in ECG parameters between control groups and patients with BrS, nor between BrS with and without VAs. During ajmaline testing, BrS with VAs presented longer QRS duration [159 +/- 34 ms versus 138 (122-155) ms, p = 0.006], higher maximum mTWA [33.8 (14.0-114) mu V versus 8.00 (3.67-28.2) mu V, p = 0.001], and lower power in low frequency band [25.6 (5.8-53.8) ms(2) versus 129.5 (52.7-286) ms(2), p < 0.0001] when compared to BrS without VAs.ConclusionsAjmaline induced important HRV changes similar to those observed during isoproterenol. Increased mTWA was observed only in patients with BrS. BrS with VAs during follow-up presented worse changes during ajmaline test, including lower LF power and higher maximum mTWA which were independent predictors of events.

Automated summary

This study evaluated changes in electrocardiographic parameters during ajmaline testing for the diagnosis of Brugada syndrome (BrS). The results showed that important heart rate variability changes were induced by ajmaline in BrS patients, and increased microvolt T wave alternans (mTWA) was observed only in BrS patients. Patients with BrS who experienced ventricular arrhythmias during follow-up showed worse changes during ajmaline testing, including lower low frequency power and higher maximum mTWA.