Stress Management and Biomarkers of Risk in Cardiac Rehabilitation

Coronary heart disease (CHD) is the leading cause of death in the United States and in roughly half the cases its first clinical manifestations, myocardial infarction (MI) or sudden cardiac death (SCD), are fatal. There is considerable evidence that "stress" plays a significant and independent role in the occurrence of CHD and its complications. This evidence has provided the rationale for developing interventional strategies to reduce stress in susceptible individuals in order to modify the natural history of these clinical events. There are now promising data to suggest that stress management training (SMT) is one such approach, and that SMT can have beneficial effects on psychosocial and medical outcomes. However, many of the randomized clinical trials (RCTs) employing stress management approaches in CHD patients have had important methodological limitations and several of the larger RCTs have failed to demonstrate a benefit for SMT over usual care, raising questions about the value of SMT for patients with CHD. Reliance on "hard" clinical endpoints is problematic because studies require such large sample sizes that they are logistically difficult to conduct and are prohibitively expensive. The use of intermediate pathophysiologic endpoints that have been shown independently to be associated with increased risk represents a novel and exciting opportunity to examine the added value of SMT in exercise-based cardiac rehabilitation (CR) compared to CR without SMT on key biomarkers of risk in vulnerable CHD patients.

This 12-week study will enroll adults with stable CHD who are eligible for CR. Participants will be randomly assigned to either standard cardiac rehabilitation or standard cardiac rehabilitation enhanced with weekly SMT. Prior to randomization, medical screening, standardized psychosocial questionnaires, mental stress testing, assessment of diet and physical activity, and exercise testing will be conducted. Additional biomarkers of risk will be assessed through measures of flow-mediated vasodilation, inflammation, platelet function, stress hormones, baroreflex, and heart rate variability.

Participants assigned to CR alone will engage in supervised exercise routines 3 times per week. Participants will be encouraged to maintain consistent exercise duration and effort throughout each session. Participants assigned to CR enhanced with SMT will engage in standard exercise-based cardiac rehabilitation and also receive weekly group SMT. At the conclusion of the 12-week intervention, participants will return for repeat assessments of stress and biomarker measures. At 6 months, 12 months, and annually up to 4 years participants will be contacted for information regarding major adverse cardiovascular events, other medical events and medication use.

Additionally a group of age, gender, and disease matched cardiac patients referred to CR, during the same time interval, but who elected not to participate in CR will form a non-randomized comparison group for cardiac events.

Overall, 164 participants were consented for study participation at Duke University Medical Center. Of these, 151 participants were randomized to either Standard Cardiac Rehabilitation or Enhanced Cardiac Rehabilitation. Post-intervention assessments were completed on 145 participants; 151 participants were available for intention-to-treat analysis.

Inclusion criteria

• Diagnosis of Coronary Heart Disease (CHD)
• Eligibility for Cardiac Rehabilitation (CR) in North Carolina
• Capacity to give informed consent and follow study procedures

Exclusion criteria

• Received heart transplant
• LVEF < 30%
• Labile ECG changes prior to testing
• Currently using a pacemaker
• Resting BP > 200/120 mm Hg
• Left main disease > 50%
• Unable to comply with assessment procedures
• Unwilling or unable to be randomized to treatment groups
• Primary diagnosis of the following psychiatric disorders: schizophrenia, dementia, current delirium, or other psychotic disorder
• Current alcohol or substance abuse disorder
• Acute suicide risk
• Actively undergoing ongoing psychiatric treatment