Study: Delaying Mitral Valve Surgery for Patients with Obesity Increases Risk of Comorbidities and Mortality

Doctors sometimes delay open-heart surgery for people with obesity, concerned that excess body fat may complicate the results. But operating sooner rather than later can help reduce the risk of patients with obesity, especially women, dying in the hospital after mitral valve surgery, according to new research published in JTCVS Open.

A team working with Joseph Lamelas, M.D., chief of the Division of Cardiothoracic Surgery at the University of Miami Miller School of Medicine, analyzed one of the most recent and largest study samples yet of hospitals in the U.S. Because mitral valve surgery is one of the most common open-heart procedures nationwide, the study examined outcomes for 48,755 patients with obesity who underwent mitral valve replacement or repair between 2012 and 2020.

“We found that obesity per se is not what drives this mortality risk. It’s actually the delayed presentation,” said medical student Ahmed Alnajar, who headed the research. “Patients with obesity often come to the surgery late, with additional comorbidities that increase their risk of mortality during the hospital stay. So, the main message is that if these patients are operated on earlier, it would benefit both the surgeon and the patient.”

The article, “Predictors of Outcomes in Patients with Obesity Following Mitral Valve Surgery,”  grew out of a study of hospital encounters from the National Inpatient Sample database that was presented at the national Mitral Conclave workshop of the American Association for Thoracic Surgery.

Elixhauser Scores Associated with In-hospital Mortality

The authors applied regression and random forest analysis to the data. Random forest uses “ensemble machine learning,” including multiple decision trees, to “tackle large, complex datasets without making overly strict assumptions about the predictive model,” said J. Sunil Rao, Ph.D., a professor and director of biostatistics in the Department of Public Health Sciences. “Data-driven models often outperform single models in terms of predictive accuracy,” Dr. Rao said.

The analysis specifically used the Elixhauser Comorbidity Index, a model based on 31 comorbidities, such as liver and kidney problems, that is designed to estimate preoperative risk. The index can be applied to various types of surgeries, including open-heart procedures.

The study found that a higher Elixhauser score — with more comorbidities — was associated with higher in-hospital mortality for the patients. Indeed, the Elixhauser score was the single most important predictive variable of survival in the hospital after the valve surgery, said Alnajar.

“When a patient has a higher Elixhauser score, we know the patient already has many diseases.  When these problems accumulate, that’s what increases their risk of mortality after surgery, more than a number on the body mass index [BMI],” which indirectly measures fat and obesity, said Alnajar.

Of course, morbid obesity — a BMI over 40 — did increase the chances of in-hospital death somewhat. And many of the morbidly obese were female, with higher Elixhauser scores. “Those females may be suffering in silence, and they come to surgery very late,” said Alnajar, urging earlier interventions.

Dr. Lamelas, a renowned pioneer in minimally invasive cardiac surgery known as the Miami Method, oversaw the team. He has performed mitral valve surgeries on patients with obesity and morbid obesity.

Dr. Lamelas said the findings confirm his preference to perform the procedures on patients with obesity earlier, and as noninvasively as possible, to reduce potential complications, minimize use of resources and improve outcomes both for patients and the health system.

“I don’t require that these higher-risk patients lose weight prior to the surgery,” said Dr. Lamelas. “I prefer to operate before the onset of additional comorbidities that will ultimately add risk, as we have documented in our study.”

Tags: cardiothoracic surgery, Department of Public Health Sciences, Division of Cardiothoracic Surgery, Dr. Ahmed Alnajar, Dr. J. Sunil Rao, Dr. Joseph Lamelas, Journal of Thoracic and Cardiovascular Surgery, JTCVS Open, mitral valve surgery, obesity, USNWR Cardiovascular