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The volume of septal reduction procedures for obstructive hypertrophic cardiomyopathy (HCM) is being spread too thin across too many hospitals -- and therefore compromising patient outcomes -- a retrospective study suggests.

Among U.S. centers analyzed over a 9-year period, 59.9% performed 10 or fewer total septal myectomies, while 66.9% performed 10 or fewer alcohol septal ablation procedures, , of Weill Cornell Medical College in New York, and colleagues, reported in JAMA Cardiology

Accordingly, the median number of myectomy cases was one per year -- 0.7 per year for alcohol septal ablation -- at a given hospital.

Following septal myectomy, the top tertile centers for volume centers had the lowest rates of:

• In-hospital death (3.8% versus 9.6% for second quartile versus 15.6% for first quartile, P<0.001)
• Need for a permanent pacemaker (8.9% versus 13.8% versus 10.0%, P<0.001)
• Bleeding complications (1.7% versus 3.8% versus 3.3%, P<0.001)

Being in the bottom tertile for septal myectomy volume was found to independently predict in-hospital mortality (odds ratio [OR] 3.11, 95% confidence interval [CI] 1.98-4.89) and bleeding (OR 3.77, 95% CI 2.12-6.70) after multivariable adjustment.

"More efforts by the cardiology community are needed to encourage referral of patients with HCM to centers of excellence for septal reduction therapy," Kim and colleagues concluded, as "septal myectomy procedures performed at low volume centers were associated with in-hospital mortality that far exceeds the recommended threshold."

That threshold comes from current guidelines, which give a class I indication that "only experienced operators with cumulative operator volume of at least 20 procedures should perform septal myectomy," the authors noted. Understandably, "septal myectomy can be a technically demanding operation, with few centers currently having extensive surgical expertise in the procedure."

Given the results, however, , and , both of Mayo Clinic in Rochester, Minn., raised the burning question: "Seriously, only 1 case per year? Why would we subject our patients to this?"

"The low-volume safety data are unacceptable. The middle volume data are not good enough. Even the highest volume tertile safety data are dramatically inferior to that achieved at HCM Centers of Excellence," they wrote in an accompanying editorial.

Kim's study "does go a long way to making an excellent case for having a few highly focused centers that specialize in the care of patients with HCM," they suggested, because these high-volume institutions see mortality rates that approach 0%.

A note from journal editors , and , both of Chicago's Northwestern Memorial Hospital, called attention to the discovery of this "gulf between clinical practice guidelines and practice."

"Continuous quality improvement necessitates that we remain vigilant in our application of cardiovascular care, transparent in our metrics of quality, and aligned with best practices," Bonow and Yancy wrote.

Kim's investigation included records from 11,248 patients who were hospitalized for septal reduction procedures from 2003 to 2011. The data came from 248 institutions and were collected as part of the Nationwide Inpatient Sample.

Institutions performing the most alcohol septal ablations were tied to a lower incidence of death (0.6% versus 0.8% for second quartile versus 2.3% for first quartile, P=0.02) and acute renal failure (2.4% versus 7.6% versus 6.2%, P<0.001). However, those advantages dissipated upon adjustment.

That more experience with alcohol ablation did not improve outcomes as it did with myectomy "could be a reflection of a significantly steeper learning curve associated with septal myectomy and the relative ease of adapting alcohol septal ablation by operators with experience in catheter-based therapy," Kim's group suggested.

The authors noted that they could not account for unmeasured confounders such as conduction and anatomical abnormalities in their retrospective study. In addition, "it is possible that the overall volume of procedures was underrepresented or over-represented by the sample," they acknowledged.

"In the end, it is not a matter of logistics, convenience, or referral patterns; it is the right thing to make sure patients get the opportunity to experience the safety and effectiveness that true expertise provides," Ommen and Nishimura concluded. "Let's heed this clarion call to help our patients."