MitraClip for Obstructive Hypertrophic Cardiomyopathy? Small Series Raises Hopes
Physicians at the Minneapolis Heart Institute say they are the first in the world to successfully use a mitral clip as initial therapy in a small series of patients with severe heart failure due to obstructive hypertrophic cardiomyopathy (HCM) who were not suitable for surgery.
According to Paul Sorajja, MD, and colleagues, percutaneous treatment with the MitraClip (Abbott Vascular) may offer new hope to a sizeable number of patients who have HCM due to left ventricular outflow tract (LVOT) obstruction, who also suffer from symptomatic mitral regurgitation (MR).
“My understanding is, we were the first in the world to do this in a patient who had not had any other procedure done,” Sorajja told TCTMD, adding that all patients had received maximal medical therapy. A German group has previously reported using a mitral clip in a patient with hypertrophic obstructive cardiomyopathy 2 years after septal myectomy in conjunction with mitral valve repair.
“Our series,” said Sorajja, “is the first to essentially take a patient who hasn’t had anything done to them and try this.” The procedure, he added, is technically the same as what is commercially being done with the MitraClip already in the setting of degenerative mitral valve disease. “That’s why we find it very exciting. It’s kind of one of these things where people say, why didn’t I think of it? That’s what people tend to say when we show them our results.”
The report was published online ahead of the June 21, 2016, issue of the Journal of the American College of Cardiology this week.
Sorajja et al tried their approach in six elderly patients with obstructive HCM, all of whom were in NYHA class III despite optimal medical management. All patients had dynamic LVOT obstruction due to elongated mitral valve leaflets and grade III or IV MR. Surgical septal myectomy—the gold standard therapy in this group—was ruled out due to the advanced age of the subjects. Instead, they were referred for alcohol septal ablation but mitral valve “plication,” using the MitraClip, was offered as an experimental alternative.
The authors report that a single mitral clip was successfully delivered to five of the six patients. The sixth developed cardiac tamponade during transseptal puncture and was converted to surgical repair and was later discharged to home care. In the MitraClip patients, postprocedure echocardiography showed elimination of systolic anterior motion in all patients, and reductions in LVOT gradient, left atrial pressure, and MR grade. In four patients, cardiac output was doubled.
At follow-up ranging from 10 to 19 months, all patients continued to demonstrate symptom improvement, with NYHA class improving by at least one functional class; three patients reported being symptom free. All patients were in MR grade 0 or 1 at the time of follow-up.
Three patients, however, had high peak LVOT velocities at follow-up, prompting operators to investigate further, performing an invasive hemodynamic study and echocardiography in a single subject. In this patient, they say, a discrepancy was seen between the direct catheter-based measurement of LVOT gradient and the much higher Doppler-estimated gradient.
High Residual LVOT Gradients Need Scrutiny
These residual high gradients, however, caught the eye of Hartzell V. Schaff, MD (Mayo Clinic, Rochester, MN), who wrote the editorial accompanying the study.
“It seems critically important to continue follow-up and investigation of the patients with high residual intracavitary velocities to understand whether the Doppler signals are benign and not related to obstruction, or whether these reflect midventricular gradients that can lead to the same symptoms caused by subaortic LVOT gradients,” Schaff writes.
Commenting on the study for TCTMD, Michael A. Fifer, MD, director of the hypertrophic cardiomyopathy program at Massachusetts General Hospital in Boston, called the paper “noteworthy” for exploring a “promising technique for patients with HOCM with symptoms refractory to optimal medical therapy.”
But Fifer, too, pointed to the high LVOT gradients as a potential problem that needs following. “I think that’s something we’re going to need to understand better before we adopt this approach in a more widespread way,” he said.
Even so, Fifer has personally discussed the approach with Sorajja and told TCTMD that he is considering the therapy in a patient who is not a candidate for either septal myectomy or septal ablation. For him to consider using the MitraClip in this setting more widely, however, Fifer says he’ll need to see results in more patients over longer follow-up, with “further investigation of these residual gradients.” With both septal myectomy and septal ablation, he noted, gradients fall by 75% or more, which is what is required to see hypertrophy regression following these treatments.
To TCTMD, Sorajja agreed that the finding of persistent, high LVOT velocities on echo is concerning and worth watching.
“We want to study them more, because we don’t know what their clinical significance is,” he said. “One avenue of benefit may be that as long as you take care of the MR, it doesn’t matter what the gradients are—they occur late in systole and they may not be meaningful,” Sorajja said. “I think the long-term benefit will likely come down to how much MR correction there is, and how much of a gradient reduction there is, but it remains to be seen how much of a gradient is necessary.”
Investigators are moving ahead with a multicenter pilot trial that will enroll 20 to 30 patients, starting in the fall with Sorajja as lead investigator.
As for the number of patients who could potentially benefit, the number is not insignificant, Sorajja said. More than half a million people have HCM in the United States alone, of whom 400,000 to 450,000 have obstructive disease. Only 5% to 10% of these will develop symptoms that require some kind of surgical therapy, Sorajja pointed out, and for eligible patients, surgery remains the best option. A percutaneous option, however, if proven safe and effective, could play an important role, particularly since alcohol ablation has known hazards, including the risk of myocardial infarction and the need for pacemaker implantation.
Septal ablation does not, however, require general anesthesia, which was used in the MitraClip procedures—a point made to TCTMD by Fifer.
Sorajja P, Pedersen WA, Bae R, et al. First experience with percutaneous mitral valve plication as primary therapy for symptomatic obstructive hypertrophic cardiomyopathy. J Am Coll Cardiol. 2016;67:2811-2818.
Schaff HV. Transcatheter mitral valve plication. Innovative approach for relief of LVOT obstruction in high-risk HCM patients. J Am Coll Cardiol. 2016;67:2819-2820.
- Sorajja reports receiving funding for consulting and serving on the speakers bureau for Abbott Vascular.
- Schaff reports having no relevant conflicts of interest.
- Fifer reports receiving a research grant from Gilead and consulting for MyoKardia, both of which have investigational drugs for HCM.