Chris Kaiser, Editor

The FDA in February approved the NaviStar ThermoCool Catheter (Biosense Webster) to treat atrial fibrillation (AF), the first ablation catheter in the U.S. to be approved to treat AF.

The FDA based the approval on a clinical study of 167 patients at 19 medical centers that showed the device effectively eliminated symptomatic recurrence of AF in a majority of patients. The device is also approved to treat atrial flutter and ventricular tachycardia.

In March, the FDA approved the ThermoCool catheter for use with remote magnetic navigation (Niobe Magnetic Navigation System, Stereotaxis), the first such approval of its kind. The use of remote navigation has been shown to reduce fluoroscopy time and to enable better control in difficult-to-reach areas.

Cooling the RF catheter tip during ablation procedures allows the operator to deliver more heat, thus creating larger, deeper lesions without charring, which can result in thrombus. Andrea Natale, MD, executive director of the Texas Cardiac Arrhythmia Institute at St. David's Medical Center, called the device “revolutionary.”

Australian researchers in 2004 found that an open irrigated tip catheter (Biosense Webster) was superior to ablation with conventional 4-mm tip catheters (Biosense Webster or Boston Scientific) in pulmonary vein isolation for patients with atrial fibrillation (Europace 2004 6(4):330-335). Patients in the irrigated-tip group (48 out of 79) were less likely to experience symptomatic recurrences or require further therapy for post-procedural arrhythmias.

The authors noted that the efficacy of irrigated-tip ablation has been demonstrated in the treatment of recurrent accessory pathways after conventional RF procedures, atrial flutter and ventricular tachycardia. “In these examples, there is a clear advantage in producing deeper lesions,” they said.

In 2007, Natale (then at the Cleveland Clinic) and colleagues reported that remote navigation and catheter ablation of atrial fibrillation (AF) was feasible. However, their total electrical disconnection rate was low. Researchers concluded that the 4-mm tip catheter is not capable of creating adequate lesions for AF ablation. “This suggests that until the 8-mm or open-irrigation catheters become available, the magnetic system should not be used for AF ablation procedures targeting the antrum,” they said (J Am Coll Cardiol 2007;50:868–74).

Nevertheless, the authors noted that magnetic navigation does not require a long learning curve and that its use significantly reduces fluoroscopy time compared with the manual technique. But now that in irrigated catheter is approved for use in remotely navigated systems, the problems cited by Natale et al should be solvable. We'll wait to see what the studies determine.

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Chris P. Kaiser

Editor