Does Afternoon Heart Surgery Improve Patient Outcomes? Key Findings on Timing & Evidence

Afternoon starts for on-pump heart surgery may reduce heart muscle injury compared to morning starts, according to a review of medical evidence updated January 26, 2025. The review found no significant difference in survival rates, heart attack frequency, or overall hospital stay length between the two timeframes.

The findings are based on a search for high-quality randomized controlled trials comparing patient outcomes for those undergoing surgery in the morning versus the afternoon. Researchers analyzed data to determine if scheduling influenced survival, heart damage, and post-operative complications.

Does surgery timing affect heart muscle injury?

One small study involving 88 participants suggested that patients who had surgery in the afternoon experienced lower levels of heart muscle injury. Researchers measured this injury using troponin, a protein released into the blood when the heart muscle is damaged.

Despite the lower troponin levels in afternoon patients, the evidence did not show a corresponding improvement in other critical metrics. According to the review, there was no clear difference between morning and afternoon groups regarding the number of heart attacks that occurred during or after the procedure.

Why does the time of day matter for heart surgery?

The human body operates on a circadian rhythm, a natural 24-hour cycle that influences various biological processes, including heart function. Some medical theories suggest the heart may tolerate surgical stress more effectively in the afternoon, which could potentially lower the risk of complications.

This timing is specifically relevant to on-pump heart surgery. These operations treat problems with heart valves or the vessels supplying blood to the heart and require a heart-lung machine to temporarily replace the functions of the heart and lungs while the surgeon operates.

What outcomes remained unchanged?

The review found that surgical timing did not appear to influence several key recovery and survival markers. According to the analyzed data, there were no differences in:

• Survival: No patients in the included study died during their hospital stay, regardless of whether surgery started in the morning or afternoon.
• Complications: There was no difference in the occurrence of irregular heartbeats, specifically atrial fibrillation.
• Heart Function: Left ventricular ejection fraction, a measure of how much blood the heart pumps out with each contraction, remained consistent across both groups.
• Hospitalization: The length of time patients needed to stay in the hospital did not vary based on the start time of the surgery.

What are the limitations of this evidence?

The current evidence is limited because the findings rely on only one small study. Because the sample size was limited to 88 people, researchers cannot be certain if the reduced heart muscle injury in afternoon patients was a result of the timing or happened by chance.

The review also noted significant gaps in available data. No studies were found that tracked short-term or long-term survival after patients were discharged from the hospital. Additionally, there is no current data on how surgery timing affects long-term heart function, the required duration of intensive care, or the overall quality of life following the procedure.

Further high-quality studies with larger patient populations are required to determine if scheduling heart surgery later in the day consistently improves patient outcomes.