ALSYNC: LV Endocardial Pacing Could Help in CRT Nonresponse

May 12, 2014

SAN FRANCISCO, CA — With ways to make cardiac resynchronization therapy (CRT) more successful in greater numbers of patients with heart failure a priority research goal, patients who can't receive or didn't respond well to CRT with standard transvenous lead systems could possibly benefit from pacing-lead placement within the left ventricle[1]. In a 138-patient safety and efficacy study of LV endocardial-lead CRT, conducted at 16 centers in Europe and two in Canada, about two-thirds of the group showed some kind of functional or reverse-remodeling response characteristic of standard CRT over at least six months of follow-up.

By positioning the pacing lead within the left ventricle, principal investigator Prof John Morgan (Southampton University Hospitals Trust, UK) explained to heartwire , "We have the landscape of the left ventricular from which to choose the most appropriate pacing site." Indeed, he said, there's evidence that such endocardial pacing produces a better physiological response to CRT than with conventional transvenous leads, whose placement is limited by venous anatomy.

Patients in the study, called the Alternate Site Cardiac Resynchronization (ALSYNC) study, which Morgan presented here at the Heart Rhythm Society 2014 Scientific Sessions , all had indications for CRT but could not have transvenous leads suitably positioned or failed to show a response to standard CRT within six months. Interestingly, the patients had a lot of comorbidities; about half had atrial fibrillation or other indications for oral anticoagulation, softening the impact, somewhat, of one of the LV endocardial-lead strategy's main disadvantages: an indefinite need for oral anticoagulation.

Another disadvantage, at least theoretically, is that the technique calls for the LV pacing lead to be inserted through the interatrial septum and across the mitral valve, raising the possibility that the lead might interfere with MV function. Were that to happen, Morgan said, it would be almost immediately noticeable; but "we certainly didn't see it either immediately after implantation or at six-month follow-up." Moreover, MV function improved in many of the patients. "I think there is potential reduction in mitral regurgitation as a response to resynchronization, which we're seeing at the six-month follow-up. That beneficial effect may be further enhanced with longer follow-up and further [improvements in] ventricular remodeling."

Rates of Achieving Functional, Reverse-Remodeling Improvements in ALSYNC

End Points All Patients (%) Patients With Prior Failed CRT Implant (%) Patients With Prior CRT Nonresponse (%)
LVESV >15% improvement 55 57 47
LVEF >5-point improvement 64 65 61
NYHA class >1 class improvement 60 63 52
Mitral regurgitation >1 class improvement 33 29 43
LVESV=left ventricular end-systolic volume
LVEF=left ventricular ejection fraction

The study enrolled 138 patients with indications for CRT and included 40% with ischemic cardiomyopathy, 50% with atrial fibrillation, 78% with a failed prior attempt to engage a CRT system, and 22% with prior successful CRT-device implantation but no response within six months. About 75% were initially in NYHA functional class 3 or 4. Successful CRT pacing with the LV endocardial lead system was achieved in 89% of attempted cases, Morgan reported.

By the six-month follow-up, 60% of patients showed improved in NYHA class and 55% showed an improvement in LV end-systolic volume of at least 15%.

Complications in the first six months included some related to anticoagulation, such as implantation-site hematoma, but also some infections, one aortic puncture at transfemoral implantation, one case of intraventricular thrombosis, two strokes, four cases of transient ischemic attack (TIA), and 10 deaths—only one, from a pneumothorax, that was related to the device implantation.

Morgan said "this is a safe procedure in the right hands." ALSYNC suggests that "we are not exposing these patients to any significantly greater risk with the actual implant procedure itself," and there is "no unexpected adverse complication rate that bothers us about this procedure in clinical terms." He emphasized that the procedure's safety depended on using the right tools, which included conventional equipment except for an investigational transseptal lead delivery system (Medtronic) designed specifically for the procedure.

It could be an option, he said, for about 30% of patients with CRT indications, those with obstacles to the standard technique. "It may be that, even in those patients who respond to conventional CRT, there are subgroups in whom the response may be even greater if they had this type of pacing approach."

Morgan discloses receiving consulting fees, honoraria, or fellowship support from Medtronic, the sponsor of ALSYNC; receiving research grants from Medtronic, Boston Scientific, and St Jude Medical; and being on a speaker's bureau for the Sorin Group. Disclosures for the coauthors are listed in the abstract.

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