Introduction: ECG changes diagnostic for Brugada syndrome may be precipitated by sodium channel blocker (SCB) challenge. The SCB ajmaline has been demonstrated to be an effective pharmacological agent of choice. Published studies recommend a dose of 1 mg/kg bodyweight (maximum 100 mg) given either as a continuous infusion or by repeated boluses at 10 mg/minute intervals. To our knowledge, there has been no comparison of these two administration methods. We aimed to compare the safety and efficacy of these two methods.
Methods: Retrospective comparison was undertaken of two cohorts undergoing SCB provocation with ajmaline in the United Kingdom: St. George’s Hospital, London using continuous infusion (n=332), and Royal Papworth Hospital, Cambridge using repeated boluses (n=148). All patients received ajmaline at a dose of 10 mg/kg with a maximum dose of 100 mg. ECGs, including high right ventricular lead positions, were compared at baseline, before drug administration, and at maximum drug effect (defined as the ECG performed after the end of infusion/last bolus administered which showed either the highest J-point elevation in the context of a type 1 Brugada ECG pattern, or maximum QRS duration in the context of a negative test). The proportion of positive test results between the two groups was compared as an indicator of diagnostic yield. Any adverse events associated with the test were documented for comparison of safety of the two administration methods. Since the likelihood of a positive test was highly dependent on the pre-test probability, the change in heart rate and QRS duration were also measured as these have been shown to increase similarly in positive and negative ajmaline provocation tests. Results were reported as proportional changes from baseline. Results are reported as mean ± standard deviation. Continuous variables were compared with a student t-test. Categorical variables were compared with a chi-squared test.
Results: The infusion and bolus cohorts were similar in terms of age (39.4 ± 14.8 versus 42.0 ± 14.4, p=0.07) and sex (56% male versus 44% male, p=0.14). There were no significant differences in the proportion of a positive test (38% versus 34%, p=0.41) between the two groups. The proportional increase in heart rate (13% versus 12%, p=0.36) and QRS duration (37% versus 26%, p=0.07) were also similar between the two groups. There were no adverse outcomes documented with either ajmaline administration method.
Conclusions: Ajmaline can be administered via continuous infusion or repeated boluses with similar safety and efficacy. Studies using both methods can be considered directly comparable. ❑
