As a Clinical Exercise Physiologist who has worked in the field of cardiac rehab (CR) for over 30 years, I occasionally see a topic pop up that draws my attention.

I have noticed some buzz around the risk stratification approach lately and wanted to shine some light on the topic. The goals of the approach are twofold; to avoid a patient waitlist as well as to expedite the patient experience as they move through the program. As we explore the concept in more detail below, I will first define the concept, then, highlight the risk stratification tools from both the American College of Sports Medicine1 (ACSM) and American Association of Cardiovascular and Pulmonary Rehabilitation2 (AACVPR). Finally, I will share some information related to dose response in cardiac rehab patients.

Defining Risk Stratification

According to the American Academy of Family Physicians, the definition of risk stratification is “the process of assigning a health risk status to a patient and using the patient's risk status to direct and improve care.” Specific to cardiac rehab, risk stratification can provide a useful perspective in exercise prescription. Both AACVPR and ACSM recommend that patients starting cardiac rehabilitation (CR) undergo stratification to identify risk for exercise-related adverse events.

Looking to the Guidelines

For decades, AACVPR and ACSM have been the leading resources for the treatment of patients in cardiac rehab. Both entities recommend evaluating the level of risk an individual faces to prescribe the appropriate exercise intensity within a CR program. There has been no attempt in the recent versions to stratify the number of sessions a patient attends. Instead, stratification is meant to determine a safe level of exercise intensity, behavior change recommendations, and an appropriate level of supervision.

Clinical Performance and Quality Measures – 2018

The 2018 ACC/AHA Clinical Performance and Quality Measures for Cardiac Rehabilitation states, “Although observational data show an association between dose of CR and patient outcomes, optimal outcomes occur with a full dose of CR (i.e., attending all 36 sessions prescribed sessions)…the writing committee proposed that this full dose measure be introduced as a quality measure, which CR programs and patients are encouraged to ideally achieve.”

Relationship Between Cardiac Rehabilitation and Long-Term Risks of Mortality and Myocardial Infarction Among Elderly Medicare Beneficiaries

Among Medicare beneficiaries, a significant dose-response relationship was found between the number of cardiac rehabilitation sessions attended and long-term outcomes. Compared to attending fewer sessions, attending all 36 sessions, reimbursed by Medicare was associated with a lower risk of mortality and MI in the 4 years after the initiation of cardiac rehabilitation. This demonstrates that greater use of cardiac rehabilitation services should be encouraged. Team members should strive to understand the barriers that prevent patients from attending the sessions to which they are entitled.

For an accessable breakdown of this graph, visit the image hyperlink.
Cumulative Incidence of Mortality by Number of Cardiac Rehabilitation Sessions Attended: Overall mortality during the first 36 weeks was 2.0% (n = 605). From this point through the end of follow-up, mortality differed significantly by the total number of rehabilitation sessions attended (P < .001). Mortality was consistently highest among patients who attended fewer than 12 sessions and lowest among patients who attended 36 or more sessions.
Dose of Cardiac Rehabilitation to Reduce Mortality and Morbidity: A Population-Based Study

This historical study of cardiac rehab patients between 2002-2012 demonstrated and confirmed the dose-response association between session attendance and major adverse cardiac events. It went on to indicate there was no apparent lower threshold or ceiling effect. It was found that the more sessions attended, the greater the risk reduction. Interestingly, no upper threshold was found. See figure below.

A significant dose–response association between cardiac rehabilitation session attendance and reductions in MACEs is observed. MACE indicates major adverse cardiovascular event. For an accessible breakdown of this graph, visit the image hyperlink.
Kaplan–Meier survival curve by cardiac rehabilitation dose category. A significant dose–response association between cardiac rehabilitation session attendance and reductions in MACEs is observed. MACE indicates major adverse cardiovascular event.

Putting it Into Practice

I understand the desire to efficiently treat as many patients as possible through risk stratification, but limiting sessions isn’t ideal based on what we know about the power of dose-response. The Million Hearts Campaign offers the following strategies to improve cardiac rehabilitation uptake:

  • Create web-based, home-based, or telemedicine-monitored programs. Virtual rehab is covered through 2024 for physician groups!
  • Use a hybrid approach for people unable to attend all 36 sessions in a cardiac rehab facility.
  • Reward eligible people for completing cardiac rehab programs.
  • Reward programs with high completion rates.
  • Share best practices and lessons learned, including innovations.


Based on research demonstrating a strong dose-response (more sessions = better outcomes), my belief is that risk stratifying one’s number of sessions should be the last line of defense. Besides reducing cardiovascular events and mortality, the benefit of a higher dose appears to be linear, with greater risk reduction at higher doses and no upper threshold. Until more research is available, striving for more time with patients regardless of their risk stratification is the most logical approach.

  1. American College of Sports Medicine. ACSM's Guidelines for Exercise Testing and Prescription. Philadelphia: Wolters Kluwer, 2021
  2. American Association of Cardiovascular & Pulmonary Rehabilitation. Guidelines for Cardiac Rehabilitation and Secondary Prevention Programs, 6th Edition. Champaign, IL: Human Kinetics, 2021

For more information, visit the following:

Million Hearts® Cardiac Rehabilitation Change Package
The Cardiac Rehabilitation Change Package presents a listing of process improvements for optimizing CR utilization.
Heart Treatments
Learn about different treatments for heart diseases and conditions.
Association of Cardiac Rehabilitation With Decreased Hospitalization and Mortality Risk After Cardiac Valve Surgery - PubMed
Fewer than half of Medicare beneficiaries undergoing cardiac valve surgery enroll in CR programs, and there are marked racial/ethnic disparities among those that do. Cardiac rehabilitation is associated with decreased 1-year cumulative hospitalization and mortality risk after valve surgery. These re…
Cardiac Rehabilitation Reduces Risk of Death Years After Heart Surgery, Still Underutilized - University of Michigan Health on The Good Men Project