Pacemaker sans leads

September 12, 2018 0 By S Harachand

Another transcatheter device that is making waves in interventional cardiology is Micra pacemakers. Micra is a small, single chamber, leadless transcatheter pacing system delivered percutaneously directly into the right ventricle.

The use of the device is indicated to patients with high-grade atrioventricular (AV) block in the presence or absence of atrial fibrillation (AF) as an alternative to dual chamber pacing when atrial lead placement is considered difficult. It is also approved for use in heart rhythm abnormalities like bradycardia-tachycardia syndrome or sinus node dysfunction (sinus bradycardia/sinus pauses).

“In India, the physician response has been enthusiastic with more than180 implants that have happened across the country, since launch,” says Abhishek Dubewar, Senior Director of Cardiac and Vascular Group, Indian Subcontinent, Medtronic.

According to Medtronic data, more than 18,000 patients across the world have been implanted Micra.

The unique feature of this device is its size. It is 93% smaller than conventional pacemakers. Micra MC1VR01 is only 25.9 mm long with a mass of 1.75 gm and an outer diameter of 6.7 mm. The bipolar device has a nominal pacing cathode with a
steroid eluting electrode and minimum pacing anode. Two of its four nitinol tines have 15 times the holding force necessary to hold the device in place. The three-axis accelerometer in Micra adjusts the heart rate automatically by sensing changes in the body related to activity level. It has a proximal retrieval feature as well to enable recovery of the device in critical situations.

Since the device is placed in the heart via a vein in the leg, it leaves no scar of a chest incision, or the bump that results from conventional pacemakers. Micra is completely self-contained within the heart.

Data from a clinical study in 719 implanted patients with average follow-up of 4.4 months showed that Micra provides the same benefits as a traditional pacemaker to increase the heart rate and help relieve the symptoms of bradycardia. Primary, prespecified safety, effectiveness and long-term performance studies have found that Micra implantations have 63% fewer major complications than traditional pacemakers.

“The advantage of Micra pacemaker is it eliminates potential infections from the implantation site or from the lead wires, as in conventional pacemakers,” says Dr Hisham Ahamed, Consultant Interventional Cardiolgist, AIMS, Kochi.

However, a limiting factor with Micra is that it is a single chamber pacemaker, pointed out Dr Ahamed. But trials are ongoing using an experimental device which can work in tandem with Micra while remaining in the adjacent chamber of the heart.