By Nicholas Tullo, MD
Cardiac pacemakers are electronic devices used in patients who have an excessively slow heartbeat. A recent study shows that a new technology known as His Bundle Pacing may prove to be better in some patients than the standard pacemaker that people have been receiving for generations.
Most pacemaker systems consist of two parts: a battery operated “pulse generator” implanted under the skin at the upper chest and one or more wires or “leads” (pronounced LEEDS) inserted into a vein and positioned on the inside of the heart chamber. The pacemaker delivers a tiny electrical signal to the heart muscle to stimulate the heart to beat, in order to maintain a normal heart rate. Nearly every pacing system includes a lead positioned in the lower chamber or right ventricle (RV). Since the dawn of pacing technology, the right ventricular lead was generally positioned at the deepest, furthest recess of the ventricle known as the RV apex, since there are muscular strands that held those early generation wires in place. Unfortunately, the RV apex is the worst place to stimulate the heart from because it results in a significant disturbance in the electrical activation of the bottom chambers, which reduces the efficiency of the left ventricular contraction. This may eventually lead to weakening of the heart muscle, which can cause congestive heart failure.
Heart rhythm specialists (cardiac electrophysiologists) have known all along that the natural electrical system of the heart, known as the cardiac conduction system, is designed to rapidly distribute the signal to all parts of the ventricles simultaneously, and thus keeps the heart squeezing most efficiently. Pacing the right ventricular apex essentially bypasses that normal electrical system, which is why standard pacemaker systems can be detrimental to the heart function. Over the last few years, these specialists have learned how to directly stimulate the main electrical pathway of the heart, known as the Bundle of His, by using a special pacemaker lead that literally screws directly into that very small region in the center of the heart’s anatomy. By stimulating the His bundle directly, the electrical activation of the bottom chambers remains rapid and efficient, leading to a more normal appearance to the signals on the electrocardiogram or ECG. This translates into a more effective contraction of the heart muscle.
The study, published in the Journal of the American College of Cardiology, included patients who received a pacemaker at the Geisinger Medical Center in Pennsylvania. The study showed that a His bundle pacing system was able to be implanted successfully in 92% of patients attempted, making it feasible and safe in a real-world situation. Not only that, His bundle pacing was associated with lower incidence of heart failure and the need for pacemaker upgrade, primarily in patients who used their RV lead significantly. This is especially good news for patients who already have mildly reduced heart function, since those patients are particularly at risk for heart failure after implantation of a standard RV pacemaker.
If you have a slow heartbeat because of problems with your electrical system, specifically if you have atrioventricular (AV) block in combination with a reduced heart muscle function, and especially if you have a prior history of heart failure, you should ask your doctor about His Bundle Pacing. Your heart may thank you for it!
Feature image via Dr. Walter Kerwin Cardiac Electrophysiologist