Internal Medicine PGY3 McMaster University Hamilton, Ontario, Canada
Background: For patients with symptomatic bradycardia, temporizing treatment options include chronotropic drugs and temporary cardiac pacing. Unclear evidence supports the use of individual therapies, and guidelines do not provide direction in the selection of therapies. This review aims to consolidate the available evidence of various chronotropic drugs and temporary pacing modalities.
METHODS AND RESULTS: We conducted systematic searches on MEDLINE, CINAHL, and MEBASE for single-arm or comparative observational and randomised studies of ≥10 patients experiencing acute symptomatic bradycardia, treated with either chronotropic drugs or temporary pacing. In the first phase of this review, we extracted the populations, interventions, comparisons, and outcomes from studies to better understand the current literature. In the second phase, we administered a survey to physicians to identify which outcomes were clinically important. In the third phase, we extracted data from studies on the outcomes determined by the survey. We assessed the risk of bias using the CLARITY tool.
After screening 13,144 abstracts and 291 full texts, we identified 99 studies that met the inclusion criteria, of which 15 were comparative and 84 were single-arm. 7 comparative and 68 single-arm studies assessed transvenous pacing, 4 comparative and 5 single-arm studies assessed transcutaneous pacing, 2 comparative and 6 single-arm studies assessed isoproterenol, 2 comparative studies assessed dopamine, 1 single-arm study assessed norepinephrine, and no studies assessed epinephrine. Additionally, 3 comparative studies assessed a mix of medical management and 8 assessed observation only. Among the comparative studies, we judged 2 studies to be at high risk of bias and 13 studies at very high risk of bias.
The outcomes and complications that were most frequently assessed in the comparative studies and that were deemed clinically important are listed in the attached table. The only clinically important outcome available that was amenable to network meta-analysis was mortality, which was assessed in 11 of the 15 studies. Network meta-analysis demonstrated very low-quality evidence that mixed medical management may be associated with lower mortality compared to transvenous pacing, transcutaneous pacing, dopamine, and isoproterenol. Similarly, isoproterenol may be associated with lower mortality compared to transvenous pacing and observation, but with higher mortality compared to transcutaneous pacing or dopamine. None of the other clinically important outcomes or complications were amenable to meta-analyses.
Conclusion: There is an overwhelming lack of evidence to guide the selection of interventions for acute bradycardia. Further studies are required to provide an evidence basis in the management of these critically ill patients.
