Cardiac Dysrhythmias


arly Stage squareA cardiac dysrhythmia is an abnormal heart beat: the rhythm may be irregular in its pacing or the heart rate may be low or high. These can be potentially life threatening, while others are normal.

While implantable devices for cardiac pacing have been used for over 50 years, there remains the desire for a less invasive approach. Implanted cardiac pacemakers carry the risks for dislocation, failure, bleeding, and stimulation in an undesired site. Recent efforts in wireless pacing are looking at endocardial wireless leads that will capture pacing information sent from a nearby transmitter to deliver pacing information to the heart. These wireless leads are a minimally invasive approach, as they still require placement in the heart, but they show the continued desire for non-invasive treatments as the final goal.

Current Treatment

Although there is interest in wireless pacemakers, the bulk of current treatment for cardiac pacing consists of wired components, which are typically inserted under sterile technique with electrodes that can attach in several locations in the heart. The typical location for the power pack is near the right shoulder, and it is connected to the electrodes and concealed in the subcutaneous tissue. The function can be updated and controlled with electronic intervention, and if electrodes fail or batteries need replacement, the device can be replaced. While the bulk of these procedures occur without difficulty, there will be always be adverse outcomes and even deaths that can occur due to the risks involved.

Focused Ultrasound Research

There is recent interest in using noninvasive focused ultrasound to stimulate cardiac muscle for a truly extracorporeal approach to cardiac pacing. This work is still in the preclinical stage, and will take ongoing refinement to be clinically applicable.

Marquet et. al. have showed data where a truly extracorporeal approach has shown ex-vivo and in-vivo pacing in preclinical studies. They base the concept on the shock wave stimulation of cardiac muscle that has been seen with Extracorporeal Shock Wave Lithotripsy. Their technique required several key components, including precise targeting, ECG gating, reliable stimulation with no associated tissue alteration, real time electrical and hemodynamic results, and consecutive pacing of a variety of locations in the heart. Functioning within these parameters, they were able to pace the heart in an entirely extracorporeal manner. The team listed clinical applicability in at least the following settings: symptomatic bradycardia, symptomatic tachydysrhythmias, asystole, multiple conduction abnormalities involving the AV node, disruption of ET related arrhythmias, and optimizing delayed atrial timing.

Notable Papers

Fabrice Marquet, Pierre Bour, Fanny Vaillant, Sana Amraoui, Rémi Dubois, Philippe Ritter, Michel Haïssaguerre, Mélèze Hocini, Olivier Bernus, and Bruno Quesson. Non-invasive cardiac pacing with image-guided focused ultrasound. Published online 2016 Nov 9. doi: 10.1038/srep36534

Reyes G, Ruyra X, Valderrama F, Jimenez A, Duran D, Perez E, Daroca T, Moya J, Ramirez U, Aldamiz G. High intensity focused ultrasound ablation for atrial fibrillation: results from the National Spanish Registry. Minerva Cardioangiol. 2016 Oct;64(5):501-6.

Kohut AR, Vecchio C, Adam D, Lewin PA. The potential of ultrasound in cardiac pacing and rhythm modulation. Expert Rev Med Devices. 2016 Sep;13(9):815-22. doi: 10.1080/17434440.2016.1217772.

Livneh A, Kimmel E, Kohut AR, Adam D. Extracorporeal acute cardiac pacing by high intensity focused ultrasound. Prog Biophys Mol Biol. 2014 Aug;115(2-3):140-53. doi: 10.1016/j.pbiomolbio.2014.08.007.