(P117) EXAGGERATED HEART RATE RESPONSE LIMITS PEAK EXERCISE CAPACITY FOR PATIENTS WITH ATRIAL FIBRILLATION

Background: Atrial fibrillation (AF) is the most treated arrhythmia, affecting more than 60 million patients globally. Current management of AF focuses on minimizing risk of stroke and controlling rapid heart rates. While early landmark trials suggested that rate controlling the heart rate to less than 110 bpm was sufficient, patients with AF often have exaggerated heart rate responses to increased metabolic demand, leading to poor exercise tolerance and quality of life. Our retrospective study aims to characterize cardiac responses to increased metabolic demand in patients with AF during cardiopulmonary exercise testing (CPET) and compared with those in sinus rhythm during CPET.

METHODS AND RESULTS: Retrospective analysis of patients with a history of AF undergoing CPET by standard Bruce protocol from January 1st, 2017 to December 31st, 2023 at London Health Sciences Centre. Response to exercise was measured using heart rate reserve and maximal rate of oxygen uptake (metabolic rate). Results were standardized to predicted maximum heart rate and metabolic rate values using patient age, height, weight, and sex. All analyses were performed using Microsoft® Excel® for Microsoft 365 MSO.
CPET data was analyzed for 127 patients with a history of paroxysmal AF. 47 studies were of patients in AF during their CPET, and 80 studies were of patients in sinus rhythm during their CPET. Nine patients had CPET studies in both AF and normal sinus rhythm (NSR). In the AF cohort, mean age was 68.8 (SD 8.9) years, 3 were female (6%), mean duration of exercise was 385 seconds (SD 156) and peak oxygen consumption was 17.4 mL/kg/min (SD 5.4). In the NSR cohort, mean age was 63.8 (SD 11.1) years, 11 were female (14%), mean duration of exercise was 465 seconds (SD 180) and average peak oxygen consumption was 20.6 mL/kg/min (SD 6.8). Patients in AF during their test had an exaggerated heart rate response with decreased maximal oxygen uptake when compared to patients with history of paroxysmal atrial fibrillation in NSR during CPET (Figure 1).

Conclusion: Patients in AF have exaggerated heart rate response to increased metabolic demand leading to poor exercise tolerance when compared to patients in NSR with a history of paroxysmal AF. Further studies are required on optimal medical therapy of AF.