30 December 2025
A recent study conducted by the cardiac surgical team at Harefield Hospital has revealed that performing heart bypass surgery without a heart-lung machine leads to better long-term survival for patients with advanced coronary artery disease.
Coronary artery disease is a condition in which blood vessels supplying the heart are narrowed or blocked. To restore this vital blood supply, surgeons perform coronary artery bypass grafting (CABG). This procedure uses healthy blood vessels from the arm or leg to bypass the blockages and enable continued blood supply to the heart.
During this surgical procedure, the patient is traditionally placed on cardiopulmonary bypass, which means blood bypasses the heart and lungs through a machine that oxygenates it externally before circulating it back through the body.
The research, led by Mr Shahzad Raja, consultant cardiac surgeon, compared long-term survival and mortality predictors for two types of CABG procedures: on-pump CABG, where the patient is on cardiopulmonary bypass, and off-pump CABG, where the surgery is performed without bypass support.
The study analysed outcomes from 13,326 patients between 1996 and 2023 and found that off-pump coronary artery bypass grafting (OPCAB) was associated with significantly improved 25-year survival rates, compared to on-pump coronary artery bypass grafting (ONCAB). It further highlighted the key predictors of long-term mortality, which could guide surgeons in choosing the best approach for each case.
This research follows on from a previous study led by Mr Shahzad Raja, which reviewed gender-based outcomes for minimally invasive surgical techniques for coronary artery disease.
Spanning over 27 years, this study was the first comprehensive evaluation of OPCAB and ONCAB. The team acknowledged that surgical techniques and institutional practices have evolved within the data collected, however, to make the comparison fair, they used a statistical method called propensity score matching, which helps create two groups of patients that are as similar as possible.
Additionally, the data was analysed from the cardiac surgery database at Harefield Hospital and unlike other studies, did not involve multiple centres. This is important because it shows how having highly skilled surgeons and a hospital with a large volume of cases can make a big difference in the success of OPCAB procedures.
When commenting on the findings, Mr Raja stated:
"This landmark research reinforces Harefield Hospital’s position as the UK’s highest-volume centre for off-pump coronary artery bypass surgery, delivering exceptional outcomes for both high-risk and low-risk patients. Our findings demonstrate that off-pump CABG is not only safe but offers superior 25-year survival compared to conventional on-pump techniques.
“These results have profound implications for surgical practice, supporting a tailored approach that prioritises long-term survival while minimising perioperative risk. By leveraging decades of experience and advanced techniques, Harefield continues to set the standard in coronary surgery."
You can access the full paper here.
Read more research stories or sign up to the research newsletter.