TAVR versus SAVR: Who determines the risk?

In this edition of the Journal, Kim et al1 report the most recent trends in surgical (SAVR) and transcatheter (TAVR) aortic valve replacement from the Michigan Society of Thoracic and Cardiovascular Surgeons Quality Collaborative database from 2012 to 2017. They found that the total annual AVR volume increased by 40% (2086-2920) with a 13.3% decrease in SAVR (1892-1640) and a 560% increase in TAVR (194-1280). These results mirror the dramatic rise in TAVR volume recently reported by the Society of Thoracic Surgery (STS) Adult Cardiac Surgery Database.2 So why is this report different from previous studies which have shown a dramatic rise in TAVR volume? In their study, Kim and colleagues found that >90% of SAVR patients had an STS predicted risk of mortality (PROM) of <8%. In contrast, >70% of TAVR patients now had a PROM <8%. This increase in TAVR patients with a PTOM <8% was due to the assignment of a higher risk score by Heart Teams using risk factors that are not identified by the current STS scoring system. This included the presence of end-stage liver disease, a prolonged 5-m walk test, the need for home oxygen, the use of bronchodilators, and abnormal pulmonary function tests. When both SAVR and TAVR patients were stratified using STS PROM scores, TAVR patients had a statistically significant increased incidence of older age, peripheral vascular disease, congestive heart failure, arrhythmias, home oxygen use, and a previous history of a coronary revascularization procedure. However, when SAVR and TAVR patients were stratified by the Heart Team, only older age and a history of a previous coronary revascularization procedure were found to be statistically increased in TAVR patients. Furthermore, SAVR patients assessed a risk score by the Heart Team, had a significantly higher incidence of renal disease including dialysis, and a history of a previous coronary revascularization procedure. Unfortunately, a major limitation of this study is that short- (30 days) and long-term outcomes were not reported for these patients. Therefore, it is unknown as to whether risk stratification by Heart Teams actually improved survival in the TAVR patients, or had an effect on SAVR mortality. Undoubtedly, as noted in other studies, improved patient selection will ultimately result in better short- and long-term survival following TAVR procedures.3 The trend toward performing TAVR in lower-risk patients is currently the subject of an ongoing clinical trial and will most likely show improved short-term outcomes for TAVR in these low-risk, healthier patients. With short-term mortality no longer an issue in deciding whether TAVR or SAVR is best for low-risk patients, long-term endpoints such as durability and the effects of permanent pacemaker placement will now assume more importance for risk stratification by Heart Teams when deciding which procedure will be best for an individual patient.