Heart Rate Trajectory Phenotypes and Clinical Outcomes

Early heart rate (HR) response to therapy for atrial fibrillation with rapid ventricular response (Afib-RVR) may provide prognostic information beyond static measurements. Identifying HR trajectory phenotypes could improve the prediction of treatment success and early adverse events, especially in heterogeneous populations presenting to the emergency department (ED).

We performed a retrospective cohort study of ED patients with Afib-RVR between 2019 and 2023. HR trajectories were classified into rapid responders (HR <110 by 2 hours), gradual responders (HR <110 by 4 hours), and non-responders (HR ≥110 through 4 hours). Primary outcomes were 6-hour rate control and composite adverse events. Multivariable logistic regression adjusted for age, baseline HR, and heart failure with reduced ejection fraction (HFrEF).

Among 311 patients, 26.4% were rapid responders, 18.0% gradual responders, and 55.6% non-responders. Rate control was achieved in 80.5% of rapid responders, 82.1% of gradual responders, and 38.2% of non-responders. In adjusted models, non-response was strongly associated with failure to achieve control (adjusted odds ratio [aOR] 0.13; 95% CI, 0.06–0.27), whereas rapid and gradual responders had similar odds of achieving control. HFrEF was independently associated with a lower odds of control (aOR 0.51; 95% CI 0.30–0.87). Adverse events occurred in 23.2% of rapid responders, 26.8% of gradual responders, and 33.5% of non-responders, but the trajectory group was not significantly associated with adverse events after adjustment. Increasing age was associated with an increased risk of adverse events (aOR 1.26 per decade; 95% CI 1.02–1.55).

Heart rate trajectory phenotypes offer meaningful prognostic insight in Afib-RVR. Non-responders constitute a high-risk phenotype with markedly lower likelihood of achieving rate control and higher crude adverse event rates. Early HR trajectories may serve as actionable intermediate markers to identify patients needing alternative therapeutic strategies or closer monitoring.