Incidence and Survival Rate of In-Hospital Cardiac Arrest Following Open-Heart Surgery: A Five-Year Retrospective Cohort Study in Western Iran Running title: Incidence and Survival of Cardiac Arrest After Cardiac Surgery

Every year, millions of people around the world undergo open-heart surgery to repair damaged valves or bypass blocked arteries. These operations are complex and life-saving, but they carry a hidden danger: the heart can stop beating unexpectedly while the patient is still in the hospital. When this happens, the medical team must act instantly to restart the heart, a process known as cardiopulmonary resuscitation. While doctors have become very good at performing the surgery itself, the outcome after the heart stops remains a difficult challenge. The window for saving a life is narrow, and even when the heart starts beating again, the patient may not survive the day, or they may wake up with serious brain damage. Understanding exactly how often this happens, who survives, and what factors tip the balance between life and death is crucial for improving care in the hours and days following these major operations.

A team of researchers in western Iran set out to map this difficult terrain by looking back at five years of patient records. They studied everyone who had undergone open-heart surgery at a major teaching hospital in Kermanshah between 2019 and 2024. Out of more than five thousand surgeries, they identified two hundred and forty-two patients who suffered a cardiac arrest inside the hospital and required resuscitation efforts. The researchers gathered every detail they could find, from the age of the patient and their medical history to the specific drugs given during the emergency and how long the team worked to restart the heart. Their goal was to move beyond general statistics and find the specific patterns that determined who lived and who did not.

The results painted a stark picture of the risks involved. In this group of patients, the heart stopped in just over five percent of all surgeries. When the team managed to restart the heart, a state doctors call return of spontaneous circulation, it happened in only about one out of every four patients. The odds of walking out of the hospital alive were even slimmer, with only sixteen percent of those who suffered an arrest surviving to discharge. The timeline of survival was particularly revealing; while sixteen percent made it out of the hospital, that number dropped slightly over the next month and fell further to just eleven percent by the six-month mark. This means that nearly one-third of the patients who survived the initial hospital stay died within the first six months after leaving, highlighting that the danger does not end when the patient is discharged.

However, the study also uncovered specific factors that made a difference. The researchers found that younger patients, specifically those under sixty-two years old, had a much better chance of surviving the arrest and leaving the hospital. Having a history of coronary artery disease, which is a narrowing of the heart's own blood vessels, surprisingly turned out to be a positive predictor for survival, likely because these patients were already under close cardiac care and their hearts were more responsive to treatment. The type of medication used during the emergency also mattered significantly. Patients who received a specific drug called calcium gluconate during resuscitation were far more likely to have their hearts restarted and to survive. Conversely, the use of epinephrine, a common heart-stimulating drug, was associated with lower survival rates, though the researchers noted this might be because the drug was given to the sickest patients who needed it most, rather than the drug itself causing harm.

Among the few who did survive, the quality of their recovery was a major focus. Of the patients who left the hospital, nearly eighty percent had a good neurological outcome, meaning they were able to think clearly and function well without severe brain damage. This suggests that when the heart is restarted quickly and effectively in a hospital setting, the brain often recovers well. The study also confirmed that the length of time the heart was stopped was a critical factor; shorter resuscitation times were linked to better outcomes. The researchers emphasized that while the overall survival rates remain low, identifying these specific predictors allows medical teams to better understand which patients are at the highest risk and what interventions might help them.

This research does not offer a simple cure, but it provides a clear roadmap of the current reality for patients facing cardiac arrest after open-heart surgery. It shows that while the odds are steep, age, specific medical histories, and the precise use of medications during the emergency play a decisive role in the outcome. The sharp decline in survival rates after patients leave the hospital serves as a reminder that the journey to recovery continues long after the initial crisis is over. By understanding these patterns, hospitals can refine their monitoring and care plans, potentially turning the tide for more of these vulnerable patients in the future.