A Behavioural Weight Loss Intervention Delivered in Cardiac Rehabilitation for Patients With Atrial Fibrillation and Obesity

Background: One-in-four Canadians will develop atrial fibrillation (AF), increasing risk of heart failure and stroke. Obesity (i.e., BMI ≥30 kg/m2) represents a strong, independent risk factor for increased incidence and severity of AF. Weight loss reduces AF symptom burden, and patients with obesity who lose ≥10% of their body weight may achieve AF regression/remission. Cardiac rehabilitation (CR) improves AF risk factors including hypertension and cardiorespiratory fitness (CRF), yet the efficacy of CR for reducing AF symptom burden is not established. CR rarely includes targeted obesity management and, on average, has a negligible impact on BMI. Adding behavioural weight-loss treatment (BWLT) to traditional CR may therefore enhance weight loss and lead to improvements in AF prognosis, symptoms, and health-related quality-of-life (HRQOL) in patients with AF and obesity.

Given the high prevalence of obesity among individuals with AF, and its detrimental effect on AF burden and outcomes, there is a critical need for interventions that can support weight-loss-promoting behaviours and can be integrated into routine clinical care for AF. CR programs are available in all major Canadian cities and have a proven track-record of achieving clinically-relevant improvements in important AF risk factors including hypertension, lipid profile, and exercise capacity. Therefore, CR represents an ideal setting to promote risk factor management for patients with AF. Yet, because traditional CR does not produce meaningful weight loss there is a clear gap in the ability of current CR programming to meet the needs of a growing population of individuals with AF and obesity. The addition of a novel BWLT component to CR is needed to bridge this gap and provide the appropriate treatment regimen of comprehensive risk factor management, exercise, and weight loss to achieve optimal AF outcomes.

The primary aim is to: Assess whether the combination of an AF-specific 'small changes' BWLT and traditional CR results in a greater proportion of patients with AF and obesity achieving ≥ 10% body weight loss compared to patients who receive standard care (traditional CR alone).

The secondary aims of the proposed study are to evaluate the impact of BWLT+CR on: 1) mean % weight loss of controls vs. intervention group; 2) AF burden; 3) self-reported AF symptom burden; 4) disease-specific and generic patient-reported outcome measures (e.g., AF- and health-related quality-of-life [HRQoL]; psychological distress); and 5) exercise volume measured in weekly steps.

Hypotheses:

The primary study hypothesis is that patients in the BWLT+CR group will be more likely to achieve ≥10% weight loss at 12 months post-randomization relative to the CR-only group.

Secondary hypotheses are that: patients in the BWLT+CR group will experience greater improvements in AF burden, AF self-reported symptom burden, increased HRQoL, decreased psychological distress, and increased leisure-time exercise and CR exercise session attendance relative to the CR-only group.

Study design:

Design and Procedure. Patients will be assessed for eligibility at TotalCardiology Rehabilitation (TCR). Eligible patients who consent to participate will be enrolled into the CR program and randomized to either the BWLT+CR or CR-only group. Prior to randomization, patients will complete a questionnaire battery including socio-demographic variables (age, sex, ethnicity, income, education), self-reported weight and height to establish BMI, and validated questionnaires assessing AF symptom burden, AF-related quality-of-life, general HRQOL, and psychological distress at baseline (T1). Patients will be re-administered the test battery following the 12-week BWLT+CR program, or 12 weeks of the CR-only program (T2). (Note: T2 measures will be administered even if the patient is still completing their remaining CR exercise sessions. CR completion/adherence will be determined after patients have completed their 12-week exercise program). The test battery will be administered for a final time approximately 24 weeks post-randomization. Weight loss from baseline to 52-weeks will be calculated and converted to a percentage of initial body weight at baseline. Clinical variables (e.g., CRF from graded exercise tests; blood pressure, lipids) will be obtained by TCR chart review.

Recruitment. Patients will be recruited in two ways: (1) directly from TotalCardiology Rehabilitation using referrals from Dr. Wilton and TCR clinic staff, and (2) from an existing database of patients who participated in the Part I qualitative study and Part II acceptability study that provided consent to be contacted about future studies. The recruitment period will be from October 2022 to April 2024. Equal numbers of men and women will be recruited. AF clinic patients who are both (a) eligible for the CR program and (b) eligible for the proposed study will be identified by Dr. Wilton and/or TCR clinic staff. Dr. Wilton/TCR clinic staff will inform patients who meet (a) and (b) criteria about the study and invite them to participate. Interested patients will receive a CR referral and their contact information will be provided to the research coordinator. The research coordinator (B. Valdarchi) will contact patients, provide additional information about the study, and obtain informed consent. The research coordinator will then send an email link to complete baseline questionnaires. Following the completion of the questionnaires, participants will be informed about the group they were randomized to, and scheduled for BWLT groups if needed. Concurrently, patients will be contacted by CR staff to schedule their orientation appointment, as per typical clinic procedures. This recruitment procedure will also apply to patients who previously participated in Part I and II (i.e the qualitative and acceptability studies, respectively). TCR patients who are currently enrolled in CR will also be recruited. A research team member will identify CR patients who have consented to be approached about research and who are eligible for inclusion by reviewing patient chart data. An RA will contact patients by telephone to review study procedures and obtain patients' informed consent.

Sample Size/Analysis. Analysis will be by intention to treat. Conservatively assuming a 5% success rate in the control group and a 30% success rate in the intervention group, 78 patients (39 per group) will provide 80% power to detect a difference using a two-sided independent test of proportions with a 5% significance level. The investigators estimate loss to follow-up and drop-outs of 20% and 10% respectively, therefore 120 patients will be recruited in total (60 per group). The primary analysis will compare the proportion in each group achieving ≥10% weight loss between baseline and 52 weeks post-randomization. A secondary per-protocol analysis will be performed including only participants who complete at least the initial 12-weeks of the BWLT. AF burden will be calculated as a % of total ECG tracings and compared between treatment and controls. Self-reported secondary outcomes will be evaluated using linear mixed modelling.