Scoring systems may overstate risk of minimally invasive aortic valve procedures

Joseph Lamelas

Current scoring systems used to assess the risk of mortality in minimally invasive aortic valve replacement surgery (miAVR) may overestimate the risk of the procedure, a paper published in the journal Innovations: Technology and Techniques in Cardiothoracic and Vascular Surgery suggests. Accuracy in assessing the risk of miAVR is necessary, the study’s authors write, as more low-risk patients are considered for transcatheter aortic valve implantation (TAVI).

Authored by Joseph Lamelas, chief and program director of cardiothoracic surgery at the University of Miami Health System (Miami, USA) and colleagues, the study analysed 1,018 low-risk patients undergoing miAVR surgery for aortic stenosis, to evaluate the accuracy of current risk scores in predicting outcomes after the procedure.

The study team looked at the four available risk scoring systems used to assess the risk of mortality from the procedure. These include the Society of Thoracic Surgeons Predicted Risk of Mortality (STS-PROM), European System for Cardiac Operative Risk Evaluation (EuroSCORE) II, TAVR Risk Score (TAVR-RS), and age, creatinine, and ejection fraction score (ACEF).

Researchers compared all four scores’ accuracy in predicting miAVR 30-day mortality by computing each score’s observed-to-expected mortality ratio (O:E). Area under the receiver operating characteristic (ROC) curves tested discrimination, and the Hosmer–Lemeshow goodness-of-fit tested calibration.

“Surgical risk scores are designed to help physicians and patients evaluate their options,” said  Lamelas. “However, they overestimate the risk for minimally invasive aortic valve replacement (miAVR) procedures through a mini thoracotomy, which can provide better outcomes and faster recoveries than open-heart surgeries through the sternum.”

The study team found that among 941 eligible patients (mean age, 72±12 years), six deaths occurred within 30 days (actual mortality rate, 0.6%). This is despite all four scoring systems overpredicting expected mortality after mini-AVR: ACEF (1.4%), EuroSCORE II (1.9%), STS-PROM (2.0%), and TAVR-RS (2.1%).

This led the study’s authors to conclude that the current surgical scoring systems for miAVR overpredict mortality by two-to-three-fold. Alternative dedicated scoring systems for mini-AVR are needed for more accurate outcomes assessment, they suggest.

“I think physicians can reassure people that their risk scores are over predicting their outcomes. The risk score by itself doesn’t matter as long as patients receive appropriate care by experienced teams,” said Ahmed Alnajar, co-researcher and quality management analyst at the Miller School of Medicine Department of Surgery, Miami USA.

“miAVR has significant advantages over conventional, sternotomy-based surgery for many patients, including shorter length of stay and recovery time, greater satisfaction, less renal failure, and better postoperative respiratory function,” added Lamelas. “That can lead to faster recovery and better survival, as well as less operative blood loss and fewer transfusions. Increasingly, patients themselves are requesting minimally invasive procedures because of these potential benefits.”

Lamelas added that risk scores for aortic valve repair procedures may change as more cardiac surgeons adapt the minimally invasive approach. “Once surgeons get past the learning curve, they find there are clear benefits for their patients,” he said. “Meanwhile, we need to develop alternative dedicated scoring systems for miAVR to help our patients make more accurate outcome assessments.”


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