Behavioural Weight Loss Treatment for Patients with Atrial Fibrillation and Obesity in Cardiac Rehabilitation

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.

A recent qualitative investigation of potential barriers and facilitators to patient uptake of a BWLT+CR intervention demonstrated that a combined CR+BWLT program is desirable to patients with AF and obesity. Results of this study will be used to adapt the existing small changes BWLT to meet the unique needs of this patient population prior to testing the intervention. Demonstrating that an AF adapted-version of the BWLT, delivered during a traditional 12-week CR program, is acceptable to patients with AF and comorbid obesity is a necessary next-step in intervention development, prior to testing the intervention in randomized designs.

The primary aim is to: Demonstrate acceptability of an adapted 12-week BWLT program, provided in the context of 12-weeks of exercise-based CR, among patients with AF and obesity.

The secondary aims of the proposed study are to: (a) Evaluate the feasibility of the fixed BWLT protocol in terms of recruitment, retention, drop out rates, treatment protocol adherence (by interventionists), and intervention adherence (attendance at BWLT and CR completion), and (b) evaluate potential improvements in weight, AF symptom burden, and psychological distress (depression, anxiety) from pre- to post-BWLT+CR program.

Hypotheses:

The primary study hypothesis is that patients will find the AF-adapted BWLT+CR program acceptable, as evidenced by ≥80% satisfaction with the intervention on the post-intervention assessments.

Secondary hypotheses are that: patients will demonstrate reductions in weight, BMI, waist circumference (when measured), AF symptom burden, as well as improved psychological distress from pre- to post- intervention.

Study design:

Design and Procedure. Patients will be assessed for eligibility at the Calgary AF clinic and TotalCardiology Rehabilitation (TCR). Eligible patients who consent to participate will be enrolled into the CR program and scheduled for the next available BWLT group session. Prior to their first BWLT session, 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 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). Additionally, intervention acceptability will be assessed using a patient survey at T2. Weight loss from baseline to 12-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 three ways: (1) directly from the Calgary AF clinic using referrals from co-investigator S. Wilton, (2) from TotalCardiology Rehabilitation, and (3) from an existing database of patients who participated in the Part I qualitative study who provided consent to be contacted about future studies. The recruitment period will be November 2021 to May 2022. 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 propose study will be identified by Dr. Wilton and/or AF clinic staff. Dr. Wilton/AF 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 (T. Williamson) will contact patients, provide additional information about the study, and obtain informed consent. The research coordinator will then schedule patients for the next available BWLT session and send an email link to complete baseline questionnaires. 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 (i.e the qualitative study).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. Patients who agree to participate will be scheduled for the next available BWLT session and e-mailed a link to complete the study questionnaire battery (T1) online via Qualtrics Software system. Patients will be instructed to complete the questionnaire battery prior to attending the first BWLT session.

Sample Size/Analysis. Analysis will be by intention to treat. Powering early-phase studies to detect statistically significant effects is not typically recommended. A final sample of 30 (15 women) will be used; 40 patients will be recruited to allow for a 25% LTFU. The primary outcome of intervention acceptability will be evaluated using descriptive statistics of acceptability survey responses and qualitative analysis of patients' open-field responses. Feasibility outcomes will also be assessed through descriptive statistics reporting adherence, drop out, recruitment, and fidelity rates. The secondary outcome of weight change will be evaluated in a within-subjects mixed (Gender; Time) ANOVA. Changes in additional secondary and exploratory variables will be evaluated in within-subjects mixed ANOVAs.