Two new studies presented April 27, 2015, at the American Association for Thoracic Surgery Annual Meeting in Seattle, WA, highlight prognostic markers that may enhance conventional risk assessment of patients with severe aortic stenosis and help steer them toward the most appropriate therapy. One study focuses on core muscle mass as an objective measure of frailty, while the other evaluates pulmonary function.

Measuring Core Muscle

In the study on muscle mass, Himanshu J. Patel, MD, and colleagues from the University of Michigan Medical Center (Ann Arbor, MI), looked at 296 patients (mean age 74 years; 65.4% men) who underwent surgical aortic valve replacement (SAVR; 52.9%) or transcatheter aortic valve replacement (TAVR; 47.1%) between 2011 and 2013. Mean Society of Thoracic Surgeons (STS) risk score was 4.4%, with the SAVR cohort predicted to be at lower risk than the TAVR cohort (3.0% vs 6.5%; P < .001).

Preoperative CT was used to calculate gender-standardized total psoas muscle area as a validated measure of sarcopenia. Overall, SAVR patients were 0.25 mm² above the mean, while TAVR patients came in 0.29 mm² below the mean (P < .001).

Overall, 8.4% of patients experienced an early poor outcome (30-day death, stroke, renal failure, prolonged ventilation, or deep wound infection). Two-year survival was lower in patients with vs without sarcopenia, defined as the lowest tertile of total psoas area (85.7% vs 93.8%; P = .02). In addition, 23.1% of patients required high resource utilization (hospital length of stay > 14 days, intensive care unit [ICU] length of stay > 7 days, or hospital readmission within 30 days) following valve replacement.

Cox regression analysis identified numerous independent predictors of these outcomes (table 1).

When the results were analyzed by treatment type, low total psoas area was an independent predictor of high resource utilization after SAVR (OR 0.4; P < .001) but not TAVR (P = .66).

Dr. Patel noted that a larger sample size and prospective analysis are needed to determine differential effects of the psoas metric on mortality in SAVR vs TAVR. Moreover, he acknowledged, sarcopenia does not evaluate other important cognitive and social aspects of frailty.

Nonetheless, he concluded, “Use of conventional risk calculators along with heart team evaluation and assessment for sarcopenia may provide optimal selection of therapy for aortic stenosis in the transcatheter era.”

In a telephone interview with TCTMD, Philippe Généreux, MD, of Columbia University Medical Center (New York, NY), applauded the effort to quantify frailty, noting that results of commonly used measures such as gait speed and the 6-minute walk test can vary depending on the kind of day the patient is having. In contrast, measurement of the psoas muscle is both easy—CT scans of the area are routinely performed for other reasons—and reproducible, he said.

Total psoas area alone is unlikely to tip the table in deciding between SAVR and TAVR, but it is an additional variable to be considered by the heart team, Dr. Généreux said. In addition, depending on its severity, sarcopenia may help identify patients who are too frail for any intervention and thus may have to be managed medically, he observed.

Dr. Généreux added that it would be interesting to see if over time muscle mass improves as a result of greater mobility in patients who respond to valve replacement.

Assessing Pulmonary Power Failure

The second study zeroed in on the role of lung disease in assessing aortic stenosis patients.

According to presenter Matthew C. Henn, MD, of Barnes-Jewish Hospital (St. Louis, MO), the STS risk score is strongly influenced by the presence and severity of lung disease, which is predominantly determined by pulmonary function test results. However, there is uncertainty over how to interpret these test results in patients with concomitant heart failure, because reduced function might be due to pulmonary edema rather than intrinsic lung disease, he noted.

To investigate the role of lung disease, Dr. Henn and colleagues retrospectively analyzed 535 patients who underwent pulmonary function tests before SAVR (n = 289) or TAVR (n = 246) between 2008 and 2013. Overall, 65% had suspected lung disease, based on a history of smoking, bronchodilator or inhaled steroid use, or home oxygen use. Pulmonary function tests showed that 49% of this group had moderate or severe lung disease compared with 21% of those without suspected lung disease

In the SAVR population, moderate/severe lung disease was associated with increased ICU utilization and longer hospital stay (both P < .001), while in the TAVR group, it was linked to more median ICU hours (P = .024) and a higher rate of ICU readmission (P = .017). However, there was no difference in perioperative mortality between those with or without moderate/severe lung disease.

Kaplan-Meier estimates of 1-year mortality rose with the severity of lung disease, from 11% for no disease to 25% for severe disease in SAVR patients (log-rank P = .034) and from 12% for no disease to 36% for severe disease in TAVR patients (log-rank P = .011). In the overall cohort, moderate/severe lung disease was associated with increased risk of 1-year mortality (adjusted HR 2.1; 95% CI 1.3-3.3). There were no interactions between lung disease severity and smoking history, suspicion of lung disease, NYHA class, or valve replacement type with respect to 1-year mortality.

“These findings suggest that pulmonary function tests should be a routine part of the preoperative workup for patients with severe aortic stenosis undergoing SAVR or TAVR,” Dr. Henn concluded.

“It is interesting to see that in patients with severe aortic stenosis, even without obvious lung disease, pulmonary function tests were abnormal,” Dr. Généreux observed. However, he added, this suggests that over time multiple episodes of heart failure may affect lung tissue and function. As with sarcopenia, it would be interesting to see if the problem resolves after valve replacement, he noted.

Knowledge of lung deficits may help identify patients who are sicker than others, Dr. Généreux noted, but he said he was skeptical about the need for pulmonary function testing in every patient. On the other hand, he commented, if TAVR was the preferred therapy, abnormal lung function results might steer operators toward conscious sedation rather than general anesthesia.

Sources:
1. Patel HJ. Use of psoas muscle size as a frailty assessment tool for open and transcatheter aortic valve replacement. Presented at: American Association for Thoracic Surgery Annual Meeting; April 27, 2015; Seattle, WA.

 2. Henn MC. Preoperative pulmonary function tests consistently predict mortality after surgical or transcatheter aortic valve replacement. Presented at: American Association for Thoracic Surgery Annual Meeting; April 27, 2015; Seattle, WA.

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