SNOWMASS, COLO. – The first-ever national study of the impact of hospital volume on outcomes of septal myectomy versus alcohol septal ablation for treatment of obstructive hypertrophic cardiomyopathy deserves to be practice-changing, Rick A. Nishimura, MD, said at the Annual Cardiovascular Conference at Snowmass.

Prior to release of these eye-opening data, conventional thinking held that referral for percutaneous septal ablation was the preferred option for elderly, sedentary patients with lots of comorbid conditions and a limited remaining lifespan, while surgical septal myectomy was the best fix for young, active, relatively healthy patients because of its impressive durability of benefit.

But while the outcomes of myectomy are significantly better than for septal ablation when the two procedures are done in high-volume centers, the national study showed that 80% of myectomies performed in the United States during 2003-2011 actually took place at centers doing fewer than 20 cases in total over that 9-year period. And in-hospital mortality and other key outcomes in those low-volume centers were far, far worse than when the surgery was done at one of the nation’s roughly two dozen hypertrophic cardiomyopathy centers of excellence recognized by the Hypertrophic Cardiomyopathy Association.

Similarly, 80% of alcohol ablations took place at centers doing less than 20 cases over 9 years. But the success of the percutaneous procedure was less dependent upon large institutional volumes. Only at the lowest-volume centers, where a total of fewer than 10 of the procedures were done over 9 years, was procedural mortality significantly higher – indeed, three- to fourfold higher – than at mid- or high-volume institutions or centers of excellence, all of which had similar mortality rates. The same was true for rates of postoperative complete heart block requiring a permanent pacemaker: significantly higher only at the lowest-volume institutions, according to the investigators from Weill Cornell Medical College in New York (JAMA Cardiol. 2016 Jun 1;1[3]:324-32).

“I think the bottom line is this: for the patient who is severely symptomatic with obstruction on optimal medical therapy, septal myectomy probably offers the best chance of excellent long-term symptomatic improvement, but the mortality depends on the center and the surgical expertise there, and complications do, too. This is something good to know that we never had data on before, that if you can’t get to a center with an experienced surgeon doing myectomies, it’s reasonable to go to a center doing ablations as long as there is some experience with the procedure there,” said Dr. Nishimura, professor of cardiovascular diseases and hypertension at the Mayo Clinic in Rochester, Minn.

Of the 11,248 patients treated for obstructive hypertrophic cardiomyopathy identified by the Cornell investigators using the Agency for Healthcare Research and Quality National Inpatient Sample database, 57% got myectomy and 43% underwent ablation. During the study years ablation increased in popularity by about 50%, rising from an annual rate of 1.6 to 2.5 procedures per million per year, while myectomy declined from 2.0 to 1.5 cases per million population per year. But that’s not what’s happened at the Mayo Clinic and other hypertrophic cardiomyopathy centers of excellence.

At the Mayo Clinic, for example, the volume of septal myectomies climbed from roughly 50 procedures per year in 2000 to close to 250 in 2015. Meanwhile the rate of alcohol septal ablation procedures remained steady at fewer than 20 per year.

“With shared decision making at Mayo, surgery has gone way up,” said Dr. Nishimura. “In an experienced surgeon’s hands, operative mortality is 0.8%, the gradient improves to 3%, and 94% of patients are postoperative New York Heart Association class I or II. This lasts for decades. We have 20-, 30-, and 40-year follow-up data now showing that over 90% of patients will have an excellent symptomatic benefit and be able to return to a normal lifestyle. The septum doesn’t come back. They’re good for life. So it’s a wonderful operation.”

In contrast, catheter-based septal ablation has a 4-year rate of survival free of death, NYHA class III or IV, or myectomy of 76%.

“One in four treated patients will not benefit,” the cardiologist emphasized.

The percutaneous procedure entails instilling alcohol into the septal perforator artery supplying the area of obstruction in order to cause a localized MI. Over a period of several weeks this causes the septum to shrink, thereby relieving the outflow tract obstruction.

When the procedure fails to bring about improvement, it’s often because the patient had a very long septal perforator artery and instilling the alcohol caused a large MI, making things worse. Or the patient didn’t have a septal perforator artery, or had one with so many branches that the cardiologist couldn’t identify the right one to treat to target the septum.

Dr. Nishimura reported having no financial conflicts.

bjancin@frontlinemedcom.com

New thinking on septal myectomy vs. alcohol ablation for obstructive cardiomyopathy