Click to Enlarge: The cumulative hazards for mortality risk across CRF categories are illustrated with survival curves. At the mean follow-up, ten years after surgery, more than 80% of High-Fit patients are alive compared to approximately 55% of patients in the Least-Fit category. CABG = Coronary Artery Bypass Grafting. Source:Journal of Clinical Medicine
WASHINGTON, D.C. — Having higher cardiorespiratory fitness scores or being in better physical condition are linked to improved long-term survival in U.S. veterans after coronary artery bypass graft surgery, according to a recent study.
The study published in the Journal of Clinical Medicine evaluated the “association between cardiorespiratory fitness and long-term survival in U.S. veterans undergoing coronary artery bypass graft surgery,” the study reported.1
This is the “first study to assess the relationship between directly measured cardiorespiratory fitness and long-term survival after coronary artery bypass grafting and to establish cardiorespiratory fitness as a risk factor for long-term mortality after coronary artery bypass grafting,” the study authors suggested.
The study authors are affiliated with the Washington D.C. VAMC in Washington, DC; The George Washington University Medical Center in Washington, DC; Walter Reed National Military Medical Center in Bethesda, MD; Henry M. Jackson Foundation for the Advancement of Military Medicine in Bethesda, MD; Rutgers University in New Brunswick, NJ; and George Washington University in Washington, DC.
Coronary artery disease is “the leading cause of death in the United States and represents a tremendous burden to the U.S. healthcare system,” the authors pointed out. For many patients, coronary artery bypass grafting “provides long-term survival benefits in excess of what can be achieved via medical management or percutaneous intervention, but factors associated with long-term mortality have not been as well defined,” the study authors explained.
“Coronary artery bypass grafting (CABG) remains the most common cardiac surgery procedure worldwide and for United States military veterans,” Gregory Trachiotis, MD, professor of surgery and biomedical engineering and chief of cardiothoracic surgery at The George Washington University Medical Center and the Washington D.C. VAMC-VISN-5, told U.S. Medicine.
“Although nationwide in the U.S., as well as worldwide, the volume of CABG procedures has decreased in selected veterans with coronary artery disease, CABG remains the most durable procedure to treat ischemic chest pain (or angina) and maintain symptom control and survival as cardiovascular disease in the U.S., among veterans and worldwide, remains the No. 1 all-cause of mortality and cost burden,” Trachiotis said.
In this study, the authors identified 14,550 U.S. veterans who underwent coronary artery bypass grafting at least six months after completing a symptom-limited exercise treadmill test with no evidence of cardiovascular disease, the study reported. The cohort of study participants was derived from the Exercise Testing and Health Outcomes Study (ETHOS) led by the Washington, D.C. VAMC, which was initiated in April 2016 and aimed to investigate associations between cardiorespiratory fitness and health outcomes, Trachiotis added.
To determine the association between cardiorespiratory fitness and risk of mortality, the authors followed up with patients after an average of 10 years and formed five fitness categories based on peak workload achieved (least-fit, low-fit, moderate-fit, fit and high-fit), the study explained. Statistical analysis was used to calculate risk across cardiorespiratory fitness categories. The models were adjusted for age, body mass index, race, cardiovascular disease, percutaneous coronary intervention prior to exercise treadmill test, cardiovascular medications and cardiovascular disease risk factors, according to the authors.
“Our study identified more than 14,000 veterans who had undergone coronary artery bypass grafting from 740,075 veterans who had undergone cardiorespiratory fitness testing, and we found those who had higher fitness scores or were in better physical condition (metabolic equivalents or METS) as determined by preoperative fitness testing had marked improved long-term survival after coronary artery bypass graft surgery (CABG), with a reduced mortality of 66% in most fit compared to 22% least fit; yet among all groups, selected patients for CABG fared well,” Trachiotis said.
The study found “improved survival with increased cardiorespiratory fitness across the spectrum of fitness levels,” Trachiotis suggested.
“Each 1-MET increase in cardiorespiratory fitness was associated with an 11% lower mortality risk,” Trachiotis said. “This finding suggests that even slight improvements in cardiorespiratory fitness, regardless of baseline fitness level, could potentially lead to improved long-term outcomes after CABG. There is a significant survival advantage for a relatively modest cardiorespiratory fitness level that most adults can likely attain by adhering to national physical activity guidelines.”
“In a second analysis of this data set, we also found a moderate cardiorespiratory fitness level resulted in 40% lower likelihood of undergoing future bypass,” Trachiotis added. “Therefore, our studies in general indicate that, if our veterans maintain, improve or achieve cardiorespiratory fitness goals and couple this with reducing cardiac vascular risk factors such as controlling diabetes, lipids or cholesterol, and hypertension and drink water, veterans can achieve healthier, longer lives. This may potentially reduce the need for future intervention, or if needing CABG, those veterans will have better and sustained outcomes with being fit.”
For healthcare professionals who are treating U.S. veterans with coronary artery disease, the study authors note that “it’s well-established that aerobic exercise is beneficial after a diagnosis of coronary artery disease, as well as after a coronary artery disease event such as myocardial infarction, and that participation in structured cardiac rehabilitation is strongly supported by national guidelines.”
“Our data provide additional support for these guidelines, particularly for patients with existing coronary artery disease and a prior percutaneous coronary intervention (PCI) who may derive a survival advantage with greater fitness levels, should they go on to require CABG,” Trachiotis said.
“The strong relationship between cardiorespiratory fitness and survival suggests a potential mortality benefit from an exercise program aimed at increasing cardiorespiratory fitness,” Trachiotis wrote. “Such a program would best be prescribed by an exercise physiologist and supervised and encouraged by a primary care physician or preventative cardiologist. It is important that these patients be assessed carefully by the health care and heart team, as this study did not include those veterans with unstable angina or poorly controlled angina or cardiac symptoms.”
- Duggan J, Peters A, Antevil J, Faselis C, Samuel I, Kokkinos P, Trachiotis G. Long-Term Mortality Risk According to Cardiorespiratory Fitness in Patients Undergoing Coronary Artery Bypass Graft Surgery. J Clin Med. 2024 Jan 31;13(3):813. doi: 10.3390/jcm13030813. PMID: 38337507; PMCID: PMC10856621.