Effect of catheter movement and contact during application of radiofrequency energy on ablation lesion characteristics

The efficient delivery of radiofrequency (RF) energy through an endocardial ablation catheter is affected by variable tissue contact due to cardiac motion with myocardial contraction and respiration. In addition, many operators intentionally move an ablation catheter during the delivery of radiofrequency energy when targeting specific arrhythmias that require lines of conduction block such as atrial flutter and atrial fibrillation. We sought to characterize and quantify any effects of catheter movement and intermittent ablation catheter contact on lesion characteristics. An ex vivo model consisting of recently excised viable bovine myocardium, a circulating saline bath at 37 A degrees C, a submersible load cell, and a deflectable sheath with an ablation catheter was assembled. A stepper motor attached to an ablation catheter apparatus was programmed to simulate linear drag lesions and series of point lesions with variable contact using constant force. Lesion volumes were analyzed using a digital micrometer by measuring depth, max width, depth at max width, and surface width and compared. The drag lesion was significantly larger than a point-by-point linear lesion using a constant force of 15 g (2,088 +/- 122 mm(3) vs. 1,595 +/- 121.6; p = 0.01) when controlling for RF time and power. For single point lesion assessment, constant contact lesions were significantly larger than lesions created with intermittent contact using the same duration of RF (194 +/- 68 mm(3) vs. 112.5 +/- 53; p = 0.03). There was no significant difference in lesion size between the constant contact at 60 s and 90-s intermittent contact lesions (194 +/- 68 mm(3) vs.186 +/- 69). In our ex vivo model, externally irrigated radiofrequency catheters produced drag lesion volumes equal to or larger than those created by a point-by-point method. We also found decreased lesion size due to intermittent contact can be overcome by increasing duration of ablation time.