One of the most effective treatments for patients with abnormally fast heart rhythms arising from the lower chambers of the heart (referred to as ventricular arrhythmias) is catheter ablation. During a catheter ablation procedure, a specialized cardiologist—a cardiac electrophysiologist—advances an ablation catheter (a catheter capable of delivering radiofrequency energy that can burn targeted heart tissue responsible for these abnormal heart rhythms) into the lower chamber of the heart.
To access the left ventricle, the most commonly targeted lower chamber, two approaches can currently be used. The first is a transseptal puncture. In this approach, the electrophysiologist enters a vein in the upper leg and advances a long needle inside a long, hollow catheter called a sheath into the right side of the heart. Using an ultrasound catheter also advanced from a vein in the upper leg to provide visual guidance, the electrophysiologist than passes the needle across the thin wall (i.e., the interatrial septum) between the right upper heart chamber (i.e., the right atrium) and the left upper heart chamber (i.e., the left atrium). Once that needle is in the left atrium, the sheath is advanced over the needle, and the needle is then removed. The ablation catheter is then advanced through the sheath into the left atrium, across the heart valve separating the left atrium from the left ventricle, and into the left ventricle.
The second option is the retrograde aortic approach. In this approach, the electrophysiologist accesses an artery (a higher-pressure blood vessel compared with a vein) in the leg and advances the ablation catheter directly via that artery into the largest artery in the body, the aorta. The ablation catheter is then curved into a loop to avoid piercing vital structures with the tip and advanced up the aorta until it crosses the aortic valve and into the left ventricle. We recently discovered that more than 60 percent of patients who undergo a retrograde aortic approach experience new small areas of damage in the brain detected by magnetic resonance imaging, or MRI. These lesions were most consistent with injury to the brain that occurred because material traveling within the bloodstream blocked blood flow to certain areas of the brain.
Based on previous literature regarding other procedures in which the inside of the aorta is used and the much lower rates of these brain lesions observed during catheter ablation procedures for a different arrhythmia (called atrial fibrillation) that always use a transseptal puncture, we believe this high rate of MRI-detected brain lesions occurs because the catheter is scraping off material from the inside wall of the aorta or aortic valve that then travels to the brain when the procedure is performed via the retrograde aortic approach. Importantly, as patients who experienced these brain lesions detected by MRI did not exhibit any obvious symptoms, the real ramifications of this brain injury remain unknown.
In speaking with patients with ventricular arrhythmias, including several who have undergone this procedure, they care most about possible effects on their ability to think, plan, and perform calculations. The best and most sensitive way to evaluate that sort of brain functioning is via neurocognitive testing.
We therefore plan to perform a study in which we will compare brain MRIs and results from neurocognitive testing before and after patients either undergo a transseptal puncture or a retrograde aortic approach for their left ventricular ablation. To attempt to avoid differences that might arise due to individual patient or operator characteristics, we will randomly assign half of the patients to the transseptal puncture and half to the retrograde aortic approach. To make sure we have enough patients to answer our research questions, we will work with six other large groups of electrophysiologists.