Two companies reported new developments in their high-intensity focused ultrasound (HIFU) programs for the ablation of cardiac tissue, specifically atrial fibrillation (AF) one on the surgical side and another in the catheterization laboratory.
On the surgical front, investigators reported that the country's first-ever Maze procedure done using HIFU technology the only energy source that allows surgeons to surgically cure AF while a patient's heart is beating, rather than having to use a heart-lung bypass machine was performed at the Northwestern Cardiovascular Institute at Northwestern Memorial Hospital (Chicago).
This system allows an ablation device to be placed on the outside of a beating heart and deliver HIFU energy across the wall of the heart to create very precise and complete lines of cardiac tissue ablation.
AF, which affects more than 6 million people worldwide, results in reduced cardiac output, exacerbates heart failure and can lead to stroke or other neurological problems.
"Ultrasound technology dramatically simplifies the Maze procedure, eliminates the need to stop the heart from beating and soon will allow us to perform the Maze procedure minimally invasively and routinely as a stand-alone surgery," said Patrick McCarthy, MD, co-director of the Northwestern Cardiovascular Institute and chief of cardiothoracic surgery at Northwestern Memorial Hospital. McCarthy, who performed the surgical "first," is one of the few surgeons trained to use the HIFU surgical ablation technology manufactured by St. Jude Medical (St. Paul, Minnesota).
The HIFU cardiac ablation procedure was performed prior to the accompanying cardiac procedure on the beating heart and off-pump without having to stop the 71-year-old male patient's heart. It added about five minutes to the overall coronary artery bypass procedure time.
"The simplicity of the HIFU system enables a smooth, uncomplicated ablation procedure," McCarthy said. "The introducer system and therapeutic devices facilitate a simple, reproducible technique that we believe will be very effective in adjunctive cardiac surgical procedures, and potentially open up new patient populations for surgical atrial fibrillation therapy."
The HIFU surgical ablation technology was originally developed by Epicor Medical (Sunnyvale, California), a company acquired by St. Jude in June 2004 for $185 million in cash.
That company has worked closely with James Cox, MD, emeritus professor of surgery in the division of cardiothoracic surgery at Washington University School of Medicine (St. Louis) to develop its HIFU ablation system and the related surgical procedure.
Cox is the developer of the Cox-Maze surgical procedure for the treatment of AF and is acknowledged by his peers as a leader in this field.
The Cox-Maze procedure is a surgical technique in which maze-like patterns are cut in the left atrial tissue, blocking the pathways which propagate AF. These techniques are nearly 90% effective, but highly invasive for patients and very technically challenging.
The HIFU technology is designed to allow physicians to safely and effectively create a "simplified Maze" lesion pattern through a less invasive approach, without placing patients on a cardiopulmonary bypass system and arresting their heart.
McCarthy said he anticipates that soon he'll begin doing the simplified Maze procedure with the HIFU technology minimally invasively, with only about an 8 cm incision. That could result in sending patients home after a day or two instead of after five days as is currently typical in patients who've had a traditional Maze procedure, he said.
"Northwestern Memorial Hospital is an outstanding partner to debut our HIFU technology to the U.S.," said Jane Song, president of St. Jude's Atrial Fibrillation business. "Dr. McCarthy's renowned international reputation and vast experience in the surgical treatment of atrial fibrillation, combined with Northwestern Memorial's commitment to building a premier heart program, make them the ideal team to introduce this new approach to surgical cardiac ablation."
Song noted that the company has received "significant interest" from other prominent institutions in the U.S. to be part of its training and market development programs. "We will be expanding these programs throughout 2005," she said.
While considered the "gold standard" in surgical treatment of AF, the Maze procedure still is performed by only a handful of cardiac surgeons across the country due to its technically challenging nature. In addition, because it requires patients to go on a heart-lung machine for up to an hour, it has typically been reserved for patients requiring other cardiac surgical procedures, such as coronary artery bypass graft or valve repair.
"While the Maze procedure is routine and incredibly safe when done by those surgeons who are experienced with the technique, many physicians still think of it as a failure if a patient with AF does not respond to medical therapy and has to be referred for surgery," McCarthy said. He added that the perceived magnitude of this surgery and the possibility of some complications associated with the heart-lung machine are responsible for this trend. He said the ultrasound technology associated with the St. Jude Medical system enables physicians to perform a simplified Maze that is highly reproducible.
"This innovation is likely to lead to more surgeons who can do the procedure and more patient referrals as physicians begin to consider the Maze a much simpler and safer surgery that doesn't require heart-lung bypass," he said, adding, "I think we'll also begin seeing earlier referrals rather than this being the treatment of last resort."
In another piece of HIFU news, ProRhythm (Setauket, New York) formerly known as Transurgical reported the first clinical use of its Steerable HIFU ablation system at St. Georg's Hospital (Hamburg, Germany).
The electrophysiology team at St. Georg's, under the direction of Professor Karl-Heinz Kuck, successfully treated eight patients with the latest generation of this system designed to treat AF.
While these procedures continue to evaluate the clinical efficacy of the system, the company said the device incorporated a significant improvement in catheter design it has designated as Active Steerability. The AF ablation procedure, commonly called pulmonary vein isolation, uses ProRhythm's balloon catheter, which is inserted through a vein in the leg of the patient and advanced into the left atrium of the heart.
Controlled, discrete ablation lesions around the pulmonary veins, created with the HIFU catheter, are intended to prevent unwanted electrical impulses from disrupting the heart's normal rhythm. The new Steerable HIFU Catheter is designed to allow physicians to more easily position the catheter accurately at the site of ablation.
In this initial series, the St. Georg's investigators were able to position the catheter with relative ease at 100% of the pulmonary veins. This ability could dramatically reduce the overall procedure time and, by allowing the user to access all four pulmonary veins, could result in improved procedural success rates, the investigators said.
"We are very pleased with the results of these initial procedures with the Steerable HIFU ablation catheter," said Kuck. "Our past clinical experience with the HIFU system has demonstrated the ability of HIFU to isolate pulmonary veins and reduce or eliminate atrial fibrillation. I believe that these latest improvements may result in procedures of one to two hours for most patients."
ProRhythm said it anticipates that its system will be approved for commercialization in Europe in the first half of this year.