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In-Heart Pacemaker Benefits Shown in Clinical Trial

Nanostim device

Nanostim device (St. Jude Medical)

31 August 2015. First reports from a clinical trial of a heart pacemaker placed inside the heart without wires shows after six months the device maintained effective pacing of patients’ hearts and worked without serious adverse effects in a vast majority of cases. Results of the trial testing the Nanostim device by St. Jude Medical were published yesterday in New England Journal of Medicine and presented at a meeting of the European Society of Cardiology in London.

Heart pacemakers are implanted in patients with an irregular or slower than normal heart rate, and generate normal-paced electrical impulses through thin wires into the heart called leads, which also sense the patient’s heart rhythm to send a compensating electrical signal. These conventional pacemakers are surgically implanted under the patient’s collarbone, with the leads running to the heart. The leads, however, need time to set requiring the patient to keep the area around the pulse generator inactive for a few weeks, to prevent disconnecting. Surgical implants also run a risk of infection around the implant site.

The Nanostim device is about one-tenth the size of a conventional pacemaker and self-contained with a battery, circuitry, and sensors sitting inside the heart, removing the need for wire leads. It is designed for patients needing to stimulate one chamber of the heart, a condition affecting 20 to 30 percent of patients requiring pacemakers.

The device is inserted with a minimally-invasive procedure using a catheter that sends the device through the femoral vein in the thigh into the heart. It can also be repositioned or retrieved after initial implant, such as for battery replacement. Science & Enterprise reported in March 2014 of an early-stage trial testing implantation of the Nanostim device.

The clinical trial, led by cardiology professor Vivek Reddy at Mount Sinai medical center in New York, tested the Nanostim among 526 individuals averaging 76 years of age enrolled at 56 sites in 3 countries, all of whom were diagnosed with heart rhythm problems in one chamber. The findings published and presented yesterday reported on experiences of the first 300 people in the group, looking primarily at Nanostim’s functioning over 6 months as well as any safety issues, including the ability to retrieve the device if necessary. The trial is still underway and aims to enroll 667 participants.

The findings show the device met both its functional and safety objectives among the large preponderance of cases. After 6 months, devices implanted in 90 percent of the 300 participants — 93 percent of the 289 patients with successful implantation — continued to meet sensing and pacing targets. Of participants tracked over 12 months, sensing and pacing threshold values improved from the time the devices were first implanted.

The authors say 504 or 96 percent of the total 526 individuals had successful Nanostim implantations, with 30 percent requiring repositioning of the device. Of the 300 participants tracked over the 6 months, 22 adverse effects were reported in 20 individuals, due to  cardiac perforation, device dislodgement, vascular complications, and elevated pacing thresholds in 1 to 2 percent of cases for each type of problem. Similar rates of adverse effects were reported for all 526 participants.

Where devices needed to be retrieved, in 7 cases, the retrievals occurred without complications. Due to individual requirements of participants, 3 received new Nanostim devices, while 2 were fitted with conventional pacemakers, and 2 people with heart failure received cardiac-resynchronization therapy.

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