By Michael H. Crawford, MD, Editor

SYNOPSIS: Investigators performed a retrospective analysis of 544 patients undergoing transcatheter aortic valve replacement (TAVR) at one center to assess the contribution of a frailty score to the Society of Thoracic Surgeons (STS) risk score for predicting mortality post-procedure. The frailty score was found to be an independent predictor of 30-day and one-year mortality and additive to the STS score.

SOURCE: Rogers T, Alraies MC, Moussa Pacha H, et al. Clinical frailty as an outcome predictor after transcatheter aortic valve implantation. Am J Cardiol 2018;121:850-855.

The assessment of the procedural risk of aortic stenosis (AS) patients considered for transcatheter aortic valve replacement (TAVR) almost always includes the Society of Thoracic Surgeons (STS) risk score. Often, some assessment of patient frailty is included, too, but little is known about the incremental value of adding an assessment of frailty to the STS score for predicting short- and long-term outcomes after TAVR.

Researchers from the MedStar Washington Hospital Center in the District of Columbia studied 544 patients with severe symptomatic AS undergoing TAVR who had the STS score calculated and frailty assessed. A frailty score was calculated based on five parameters, with a score range of 0 to 5. The factors were: body mass index (BMI) < 20kg/m², serum albumin < 3.5g/dL, a Katz activities of daily living index of < 4 (six measures total), low grip strength based on sex and BMI, and a slow 15-foot walk time based on sex and height. Frailty was defined as a score of ≥ 3. The outcomes assessed were in-hospital, 30-day, and one-year all-cause mortality, stroke, vascular complications, bleeding complications, and acute kidney injury.

Frailty was observed in 44% of patients. Frail patients were older, suffered from severe chronic obstructive lung disease, demonstrated high STS scores, and were short in stature. The STS score alone was not associated with higher mortality after TAVR at 30 days or one year. After a multivariate analysis, frailty was a significant predictor of mortality at 30 days (odds ratio [OR], 5.06; 95% confidence interval [CI], 1.36-18.8; P = 0.015) and one year (OR, 2.75; 95% CI, 1.55-4.87; P = 0.001). Patients who were frail and registered an STS score of > 8 demonstrated the highest mortality rate (about 25% at one year). When frailty was added to the STS score, the C-statistic for predicting 30-day mortality increased from 0.59 to 0.67 and from 0.62 to 0.66 for one-year mortality, which in both cases resulted in significant net reclassification improvement. The authors concluded that an assessment of frailty should be part of the pre-procedural assessment of all patients with severe AS under consideration for TAVR.

COMMENTARY

A recent paper from France showed a 72% increase in aortic valve replacements from 2007-2015 in the whole country, which was largely due to the introduction of TAVR in 2007. However, the in-hospital mortality rate in those > 75 years of age was not significantly different between TAVR and surgical replacement, whereas in those < 75 years, the TAVR mortality rate was significantly lower.1 These observations from a national administrative database raise the question of whether TAVR is overused, especially among very elderly patients.

This issue is addressed in part in the Rogers et al study, which analyzed the influence of frailty on outcomes after TAVR. The authors demonstrated that frailty is an independent predictor of short- and long-term mortality and added incremental predictive value to the STS score. This is perhaps not surprising since the STS score was designed to determine the risk of surgical valve replacement, which would be expected to be different from transcatheter delivery. If cardiologists design a new risk score for TAVR, an assessment of frailty should be part of it.

There were limitations to this study. It was a retrospective analysis, but of prospectively collected data. All five frailty indices had to be obtained to be included, which may have excluded some very high-risk patients who couldn’t walk 15 feet. Their inclusion likely would have increased the mortality rates observed. Also, Rogers et al did not test each individual frailty measure alone. This would have been useful as there are several frailty measurement tools used.

Based on this study’s results and their experience, the authors proposed 10 parameters that, if present, should initiate a discussion about the futility of TAVR in the patient under assessment: unable to complete a short gait speed test, dependent for most activities of daily living, low serum albumin, unintentional weight loss, significant anemia without a reversible cause, advance dementia, oxygen-dependent lung disease, atrial fibrillation, severe chronic kidney disease (especially if on dialysis), and severe liver disease.

REFERENCE

  1. Nguyen V, Michel M, Eltchaninoff H, et al. Implementation of transcatheter aortic valve replacement in France. J Am Coll Cardiol 2018;71:1614-1627.