SNOWMASS, COLO. – The Society of Thoracic Surgeons Predicted Risk of Mortality score draws criticism when it’s used to help decide whether a patient should undergo surgical or transcatheter aortic valve replacement, because the algorithm excludes plenty of information pertinent to that task. Yet for now it’s an indispensible tool for cardiologists and surgeons alike, Dr. Vinod H. Thourani asserted at the Annual Cardiovascular Conference at Snowmass.
"Calculate an STS score for all patients, as annoying as it is. The goal should be to fit the patient with the best operation, not to force the patient into one technique or the other. The STS score is the only thing we have right now. Work is underway on a new TAVR risk scoring system, but it’s not ready yet," said Dr. Thourani, associate director of cardiothoracic surgery at Emory University, Atlanta.
The STS score was originally developed to predict the risk of mortality in coronary artery bypass graft (CABG) patients. But despite the score’s limitations when applied to patients requiring aortic valve replacement, a new analysis of the massive STS national database demonstrates that the tool is surprisingly accurate for this purpose.
Dr. Vinod H. Thourani
"In reality, the STS score does a pretty good job of predicting what you’re going to do in open surgery. Everybody poo-poos the score, but here we’ve got data on 142,000 patients undergoing isolated surgical aortic valve replacement, and it’s actually pretty close. So I think you can use the STS score for prediction of surgical valve mortality," according to Dr. Thourani.
Among the 141,905 patients in the STS database who underwent isolated surgical aortic valve replacement (SAVR) during roughly the past 6 years, 6% were high risk as defined by an STS predicted risk of mortality score greater than 8%. Another 14% were intermediate risk, with an STS score of 4%-8%. The remaining 80% were low risk, with an STS score of less than 4%.
In a soon-to-be-published report by Dr. Thourani and his coinvestigators, the median postoperative length of stay was 6.0 days in the group with a low-risk STS score, 8.0 days in the intermediate-risk patients, and 9.0 days in those with an STS score greater than 8%. Actual national in-hospital mortality in SAVR patients with an STS score of less than 4% was 1.4%, whereas the mean and median STS for predicted in-hospital mortality in this cohort was 1.7% and 1.5%, respectively. In-hospital mortality in the intermediate-risk group was 5.1%; the mean and median STS scores in this group were 5.5% and 5.2%. And in the high-risk group, in-hospital mortality was 11.8%, compared with 13.7% and 11.2% mean and median predicted rates based on STS scores.
At Emory and other multidisciplinary heart centers around the country, patients needing aortic valve replacement who have an STS score below 4% typically get SAVR with either a stented or sutureless valve. Intermediate-risk patients – those with an STS score of 4%-8% – get SAVR or are enrolled in a mid-risk TAVR clinical trial, provided it’s an option at that site. High-risk patients with an STS score greater than 8% have the option of an open or mini-SAVR, although Dr. Thourani said most of his high-risk patients now undergo TAVR. Extremely high-risk patients having an STS score greater than 15% aren’t candidates for surgery; their options are commercially available TAVR or palliation via balloon valvuloplasty and/or medical therapy.
Patients in need of aortic valve replacement who present to a multidisciplinary heart center undergo an extensive battery of tests aimed at helping the team decide whether SAVR or TAVR is best for that individual. These tests assess relevant factors not included in the STS score algorithm. For example, frailty assessment is not incorporated in the STS score, yet most patients in need of a new aortic valve are elderly. At Emory, patients being evaluated for aortic valve replacement undergo five different measures of frailty: gait speed, grip strength, activities of daily living assessment, nutrition, and the mini–mental status examination. If someone fails three of these five measures, Dr. Thourani rules out the option of SAVR.
Other routine tests include a computed tomography (CT) scan to evaluate the ascending aorta and femoral and iliac arteries for calcification, echocardiography to determine annular sizing, carotid duplex ultrasound, pulmonary function tests, and cardiac catheterization.
TAVR is the best option for patients with porcelain aorta, a hostile chest due to prior radiation therapy, end-stage renal disease, severe lung disease, advanced liver disease, prior CABG surgery with an internal mammary artery graft crossing the midline, more than two prior sternotomies, or moderate dementia.