For patients at high-risk of sudden cardiac arrest, an electrical malfunction in the heart that causes abrupt loss of heart function, an “extravascular” system with pacemaker and defibrillator features has the potential to provide pacing without the need for intracardiac hardware placement, according to a recent study in the journal HeartRhythm, led by researcher and principal investigator Darius Sholevar, M.D., of Lourdes Cardiology.
The manuscript titled, Feasibility of Extravascular Pacing with a Novel Substernal Electrode Configuration: The Substernal Pacing Acute Clinical Evaluation (SPACE) included 26 patients from eight sites in the U.S. and Canada — with Lourdes having 13 patients, the most of any site in the world.
Data demonstrated that pacing is possible from this extravascular space (a lead placed outside the heart and under the rib cage), with the majority of patients (69 percent) achieving consistent and appropriate ventricular pacing results. Medtronic sponsored the study and is currently developing an extravascular (EV) ICD system.
“The extravascular system has the potential to be more effective than current subcutaneous ICD systems in terms of correcting an abnormal heart rhythm,” said Dr. Sholevar. “In this study, the technique proved that we may be able to bypass the issues experienced with the other ICD techniques.”
Sudden cardiac arrest is the chief cause of natural death in the U.S., with 325,000 people dying each year. For patients who are high-risk, an implantable cardioverter defibrillator, or ICD, may be inserted as a preventive treatment. The device is similar to a pacemaker, however it can detect and correct a fatally fast heart rate with a high energy shock to get the heart back to a normal rhythm.
There are currently two types of ICDs — transvenous and subcutaneous — that offer a high rate of effectiveness, however, both have limitations.
Traditional transvenous ICDs offer consistent and reliable pacemaker activity to speed up slow heart beats and often last in excess of 12 years. Leads inserted through veins and into the heart have extra risks and problems for patients with underlying structural cardiac abnormalities or with difficult vascular access. The vast majority of patients who receive traditional ICDs do well but a small number may have problems throughout their lifetimes. For young individuals receiving the device, there is a significant lifetime risk of problems related to the wires in the heart. Wires can break, malfunction or be involved in infections. Lead revision and extraction procedures are feasible and generally safe but they include some significant risks.
The other currently available ICD, the subcutaneous system, is positioned under the skin outside of chest wall. It is limited in that it does not work as a pacemaker (unlike a transvenous ICD which is both a pacemaker and defibrillator). The subcutaneous ICD can deliver post-shock pacing therapy, but in doing so, it also paces the muscle wall, which can be uncomfortable in conscious patients. Due to the fact that wires are placed outside the chest wall, the device must be larger to deliver a higher energy shock. This results in a device that is roughly twice the size of transvenous ICDs and that lasts half as long at 5 to 7 years.
Researchers are hoping extravascular ICD therapy will help bypass these limitations, since the approach includes pacemaker and defibrillator capabilities.
Dr. Sholevar adds that further work needs to be done in this area. “The SPACE study looked at a novel extravascular approach and the feasibility of pacing from this location. The results are promising and we look to further study to make this a reality for those at risk of sudden cardiac death.”
Lourdes Cardiology is one of the largest providers of cardiac services in Delaware Valley, with the best and most impressive track record for efficiency, cost effectiveness and quality, as recently featured in the New York Times. Our Lady of Lourdes Medical Center is recognized consistently by Healthgrades, Becker’s and Truven Analytics for cardiac care. Lourdes is the only hospital in New Jersey approved to perform kidney, pancreas and liver transplants. It is also the only hospital in New Jersey, Pennsylvania or Delaware ever to have been awarded the American Hospital Association’s top honor for excellence in community outreach services.