Worse Outcomes With Lower Volume in Septal Myectomy for Cardiomyopathy

Most US hospitals that offer septal reduction therapy for obstructive hypertrophic cardiomyopathy performed few annual septal myectomy (SM) and alcohol septal ablation (ASA) procedures, according to an analysis of a nationwide inpatient database, published in JAMA Cardiology.

The lower volume of procedures is “below the threshold” recommended by the 2011 American College of Cardiology Foundation/American Heart Association Task Force Guideline for the Diagnosis and Treatment of Hypertrophic Cardiomyopathy.

Currently, surgical SM is the “preferred strategy” for relief of left ventricular outflow tract (LVOT) obstruction, as described by the authors. However, ASA is a minimally invasive alternative to surgery performed using a percutaneous catheter technique with absolute alcohol in order to induce a targeted septal myocardial infarction.

Researchers measured rates of adverse in-hospital events (death, stroke, bleeding, acute renal failure, and need for permanent pacemaker) as the main outcomes. They used multivariate logistic regression analyses to compare overall outcomes after each type of procedure based on tertiles of hospital volumes of SM and ASA.

Of the 11 248 patients who underwent septal reduction procedures from 2003 through 2011, 6386 (56.8%) underwent SM and 4862 (43.2%) underwent ASA. When stratified by first, second, and third tertiles of hospital volume, incidence of in-hospital death after SM was 15.6%, 9.6%, and 3.8% (P<.001). Incidences of bleeding complications were 3.3%, 3.8%, and 1.7% (P<.001) and need for pacemaker were 10.0%, 13.8%, and 8.9% (P<.001).

After ASA procedures, death and acute renal failure rates were also lower in the higher-volume centers (2.3%, 0.8, and 0.6%; P=.02 and 6.2%, 7.6%, and 2.4%; P<.001), respectively.

Researchers discovered that the lowest tertile of SM volume was an independent predictor of in-hospital all cause mortality (adjusted odds ratio [OR]: 3.11; 95% confidence interval [CI]: 1.98-4.89) and bleeding (OR: 3.77; 95% CI: 2.12-6.70). In contrast, the lowest tertile of ASA by volume was not independently associated with an increased risk of adverse events post-procedure.

In 2003, 2.00 SM procedures per million people per year were performed compared with 1.51 SM procedures per million people per year in 2011—a decrease of 24.5%. Conversely, ASA procedure rates actually increased 56.2%—from 1.60 procedures per million people per year in 2003 to 2.49 procedures per million people per year in 2011.  Researchers pointed out, “The trends in overall rates of SM or ASA procedures during the study period, however, were not significant. The median numbers of cases for SM and ASA were 1.0 and 0.7 per year per institution, respectively.”

“Undergoing SM in centers that rarely perform septal reduction operations was associated with worse posprocedural outcomes compared with high-volume centers, with a 3-fold higher mortality (in first- vs third-tertile institutions by volume),” they added. “On the other hand, undergoing ASA in lower-volume institutions was not associated with worse outcomes after ASA compared with high-volume ASA centers.”

Ultimately, a more concerted effort should be made to refer patients with hypertrophic cardiomyopathy to the best-equipped institutions for septal reduction therapy, the authors concluded.

Reference

Kim LK, Swaminathan RV, Looser P, et al. Hospital volume outcomes after septal myectomy and alcohol septal ablation for treatment of obstructive hypertropic cardiomyopathy. US nationwide inpatient database, 2003-2011. JAMA Cardiol. 2016. doi: 10.1001/jamacardio.2016.0252.