CryoCath updates pivotal AF study
CryoCath Technologies has released twelve month follow-up data from 15 patients treated during the feasibility stage of its STOP AF trial. The pivotal trial aims to evaluate the company's proprietary Arctic Front catheter to treat atrial fibrillation (AF), a minimally invasive cryo-balloon catheter designed specifically to treat AF.
The trial's primary endpoint will be the absence of detectable AF at the end of the 12-month follow up period. The trial's design also allows patients randomised into the drug arm to cross over into the ablation arm if they do not show improvement.
During the study's feasibility stage, a total of 33 patients were treated. At the six month mark, 11 of the original 15 patients (73%) were AF free. Of the 11, nine are AF free at twelve months and off anti-arrhythmic drugs (AAD's), and two did not show up for their one year visits. Of the four that were not AF free at six months, all are off AAD's at 12 months, suggesting their AF condition improved to the level that AAD treatment is no longer necessary.
Jean-Pierre Desmarais, CryoCath's CEO explained, "The twelve month data is encouraging and strongly suggests that we are creating permanent lesions, producing a significant clinical benefit, including, in the majority of cases, freedom of AF. It is critical to note that those patients that were AF free at six months remained so at twelve months. This is the key result."
The researchers further explained that of the remaining 18 patients from the feasibility stage, five have reached the six month mark and off AAD's, and four of these are AF free and all. Of the balance of thirteen patients, all have reached their three month follow up and are off AAD's.
As many as 250 patients, randomised into two arms, will be enrolled to complete the trial. One cohort will receive cryoablation therapy with AF, the other will receive currently prescribed drug therapies. For every two patients in the ablation arm, there will be one in the control arm.
First closed-chest, robotic procedure
In further developments, MedicalCV has reported that Dr Allen R Raczkowski, a cardiothoracic surgeon at Banner Baywood Heart Hospital in Mesa, Arizona, completed the first closed-chest, robotic procedure using the AtriLaze Surgical Ablation System to treat AF in conjunction with a minimally invasive mitral valve repair.
"By leveraging both the focused, coherent energy and the low profile, flexible fibre optic wand of the AtriLaze System, I was able to create the precise lesion sets in the left atrium in a closed-chest setting with robotic assistance," said Raczkowski, a pioneer in minimally invasive cardiac surgery. "The patient has done quite well, post-operatively; he has been discharged from the hospital is currently experiencing normal heart rhythm."
Marc P Flores, president and CEO of MedicalCV commented, "This closed-chest, robotic procedure represents a unique application of the AtriLaze wand-based technology platform, and it further demonstrates its inherent advantages in cardiac tissue ablation." Flores added, "The combination of our flexible fibre optic wand and focused, coherent energy delivery system affords surgeons an opportunity to provide patients with an exciting, less invasive solution for cardiac tissue ablation today. We are gratified by both the outcome of this procedure and the opportunity to partner with this innovative physician to provide superior patient care."
High-energy clamp simplifies heart surgery for AF
Heart surgeons at Washington University School of Medicine in St Louis, US have used radiofrequency devices instead of surgical techniques for treatment of AF.
"Because of the devices, the procedure - called the Cox-Maze procedure - has gone from an operation that hardly anyone was doing to one that 80 to 90% of US heart surgeons are now performing," says Dr Ralph J Damiano, the John Shoenberg Professor of Surgery and chief of cardiac surgery at the School of Medicine and a cardiac surgeon at Barnes-Jewish Hospital.
Damiano and his colleagues have been involved in the development and testing of radiofrequency devices for AF. The devices deliver high-energy radiofrequency waves to heart tissue and very quickly create scars or ablations, which replace most of the complex incisions required by the Cox-Maze procedure. The ablations disrupt the atria's abnormal electrical activity and normalise heart rhythm.
The Cox-Maze procedure is named for Dr James Cox, former director of Washington University's division of cardiothoracic surgery, who led the St Louis research group that developed the procedure in 1987.
The clamp-like jaws of the radiofrequency ablation devices latch onto a section of heart muscle and deliver a thin, focused line of energy that heats and ablates the tissue. Ablation with the devices can replace all but two small incisions that would typically be made during a traditional Cox-Maze procedure.
"We've not only reduced the time needed for the procedure, we've made the procedure easier to perform," Damiano says. "In addition to eliminating most of the incisions, the radiofrequency ablation clamp removes the potential for error by monitoring when the lesion goes all the way through the tissue and automatically shutting the power off at that point."
By simplifying the Cox-Maze surgery, the method will make the procedure available to more patients. "This has made it possible to offer this curative operation to almost everyone coming for heart surgery who has chronic atrial fibrillation," Damiano says.
Damiano and colleagues are now working to develop a device that will make the Cox-Maze procedure even less invasive. The device would allow surgeons to perform the procedure on the beating heart and do away with the need to stop the heart and place the patient on a heart-lung machine. Heart-lung machines can introduce the potential for stroke or organ failure with extended use.
"We've made the first big step: we've taken a very complicated operation and made it simpler. We've tremendously decreased morbidity and virtually eliminated mortality," explained Damiano. "Now we are aggressively working on a device that would allow us to do the full set of Cox-Maze lesions without using a heart-lung machine."
Late recurrence observed in AF patients 'cured'
Recently, a small study has revealed that even among patients cured of AF with pulmonary-vein isolation, there is a still a risk of late recurrence. This finding stresses the importance of long-term follow-up care and anticoagulation strategies in these patients, report investigators.
Presenting the findings at the American Heart Association 2006 Scientific Sessions in Chicago, lead investigator Dr Arti Shah (St Luke's-Roosevelt Hospital Center, New York) showed that in a cohort of patients free from AF at one year, symptomatic AF recurred in 8.7%, with the attrition rate beginning approximately two years after the initially successful ablation.
Shah explained that although a large population of patients who undergo pulmonary-vein isolation for AF have a complete response to therapy and are free of the arrhythmia, it is unclear whether these patients are cured or whether there is a late attrition rate. To examine the possibility of late recurrence, researchers studied patients free from AF at one year, all of whom discontinued drug therapy at one month. Patients, the majority of whom were male (72%) and had paroxysmal AF (82%), were then followed for one to five years.
According to Shah, all pulmonary-vein-isolation ablations were electrophysiology-guided using a lasso catheter, and the aim of procedure was complete electrical disconnection. If a repeat ablation was needed three to six months after the initial ablation, the pulmonary veins were reisolated and additional left atrial and mitral isthmus lesion sets were performed as necessary. Overall, 264 patients were free from AF at one year. Of these patients, 233 were free of the arrhythmia after the first ablation and 31 were free from AF after a follow-up ablation procedure performed within three to six months.
Furthermore, of the 264 patients, symptomatic recurrence was observed in 23 patients free from AF at one year, occurring approximately two years after the initial ablation procedure. Most late recurrences were associated with a pulmonary vein-left atrial reconnection, noted Shah.
Shah concluded by explaining that overall, there were no significant baseline differences, such as age, sex, type and duration of atrial fibrillation, duration of procedure, left ventricular ejection fraction, or presence of coronary artery disease, among long-term responders to ablation and those who developed late-recurrence atrial fibrillation. The presence of hypertension and hyperlipidemia, however, did predispose to late atrial-fibrillation recurrence.
Date: Jan/2007
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