The ablation of atrial fibrillation with the loop catheter design: what we have learned from the animal model.

Ablation of chronic atrial fibrillation (AF) with the use of transcutaneous catheter ablation is yet to become a clinical tool. This article summarizes the development of the technology and the technique for the ablation of AF that was tested on the rapidly paced AF dog model. The current ablation technology using the standard ablation technique used in humans is not suitable for the creation of transmural contiguous linear lesions, and such technology is subjecting the patient to the prolonged procedures with considerable risk of complication. The use of the loop catheter design or other designs of ablation technology, which is specifically targeted for the creation of linear lesions, should be developed if the catheter approach for the ablation of AF is to succeed. This article describes the data available for the loop catheter design that is currently undergoing human feasibility studies.

Ablation of atrial fibrillation in the rapid pacing canine model using a multi-electrode loop catheter.

OBJECTIVES: This investigation details our experience using a loop catheter to ablate atrial fibrillation (AF) in dogs. BACKGROUND: Atrial fibrillation is the most common arrhythmia and has significant morbidity. Maintenance of normal sinus rhythm (NSR) after conversion in many patients is still a challenge. METHODS: A multi-electrode loop catheter was used to create linear atrial lesions to ablate AF in a rapid atrial pacing model in 29 dogs. Rhythm status was assessed over a six-month recovery period, after which tissue analysis was performed. RESULTS: Acute conversion to NSR or atrial tachycardia (AT) was achieved in 90% of cases. Six of 26 conversions occurred after only left atrial (LA) lesions, and two after just right atrial lesions. Sixteen (62%) of 26 lesions that resulted in AF conversion were in the LA, and 11 of these 16 conversions occurred during a lesion connecting the mitral ring to the pulmonary veins. Acute conversion rate was similar with ring and coil electrodes, but AT was more frequent with coil electrodes (63% vs. 31%). At six months 80% of dogs were in NSR, 14% were in AT, and 7% remained in AF. There was an average reduction in P-wave amplitude of 64 +/- 26% after power application. Tissue analysis revealed transmural contiguous lesions when final outcome was NSR, and nontransmural/noncontiguous lesions where AF persisted. CONCLUSIONS: Multi-electrode loop catheters can create contiguous transmural lesions in either atrium to safely and effectively ablate AF and provide a stable long-term rhythm outcome in this dog model. The left atrium appears to be the dominant chamber that sustains AF. Atrial tachycardia is a frequent acute outcome with coil electrodes.

Time course of left atrial mechanical recovery after linear lesions: normal sinus rhythm versus a chronic atrial fibrillation dog model.

INTRODUCTION: The extent of left atrial (LA) mechanical function recovery after creation of linear lesions using the loop catheter has not been determined. METHODS AND RESULTS: LA mechanical function was assessed before and after linear lesions using transthoracic two-dimensional and Doppler echocardiography in two groups: (1) normal, which consisted of eight healthy dogs in normal sinus rhythm (NSR); and (2) atrial fibrillation (AF), which consisted of nine dogs in spontaneous AF for 6 months following rapid pacing-induced AF. NSR was restored with linear lesions in all AF dogs. All animals were in NSR 5 months after linear lesions. In the normal dogs, the maximal velocity of the transmitral flow "A" wave was reduced by 42% during the first week postablation and by 24% at 5 months versus preablation. At 5 months, no differences in LA function were noted between the normal and the AF group for all measured Doppler parameters. At 5 months, the LA systolic area in AF dogs was reduced by 40% (preablation 12.9 +/- 2.9 cm2, postablation 7.6 +/- 1.2 cm2; P < 0.01) and in the normal dogs by 21% (preablation 10.0 +/- 0.9 cm2, postablation 7.8 +/- 1.2 cm2; P < 0.02), being the same in both groups within 3 months of recovery. CONCLUSION: The creation of linear lesions with the loop catheter does not result in LA expansion. In normal dogs, LA mechanical activity is reduced for 3 weeks postablation. The time course of LA mechanical function recovery is the same for the AF and the NSR dogs, and it is complete at 3 months postablation. At 5 months, LA systolic function parameters in both groups are reduced by 24% versus the preablation values of the normal dogs. Linear lesions result in a significant reduction in LA size.

Ability of the no-reflow phenomenon during an acute myocardial infarction to predict left ventricular dysfunction at one-month follow-up.

Despite angiographically successful opening of an infarct-related vessel within a 6-hour time frame, some patients do not recover left ventricular regional wall function in the infarct zone after an acute myocardial infarction (AMI). Recent evidence suggests that this finding is due to the no-reflow phenomenon, or failure to recover tissue perfusion despite patient epicardial arteries. We performed myocardial contrast echocardiography to assess tissue perfusion before and after opening of an infarct-related artery. Coronary angiograms, regional wall motion scoring, and myocardial contrast enhancement were graded by 3 observers. Of 24 patients with AMI, 7 (29%) failed to recover tissue perfusion in > or = 1 region of myocardium. Of 106 regions subtended by the infarct-related artery, 16 (15%), 43 (41%), and 47 (44%) regions had no-reflow, partial, or normal flow, respectively, after arterial patency was established. There was a spectrum of reperfusion patterns ranging from no-reflow to normal perfusion. One-month follow-up angiographic and myocardial contrast echocardiographic studies were performed in 12 of the 24 patients. At 1 month, all segments of myocardium that had immediate normal perfusion had regained normal wall motion. In contrast, 17 segments that had partial or no-reflow were identified. Of these 17, 3 regained normal function, 10 segments were hypokinetic, and 4 segments were akinetic. We conclude that myocardial contrast echocardiography can be used to identify the no-reflow phenomenon in up to 29% of patients with AMI. Additionally, we found that the immediate-reflow pattern can predict degree of left ventricular dysfunction at 1-month follow-up.

[Ultrastructure of the nerve plexuses of the arteries of healthy rabbits and rabbits with Brown-Pearce tumors]. / Ul'trastruktura nervnykh spletenii arterii krolika v norme i pri opukholi Brauna-Pirsa.

The neural formations of intact rabbit major arteries and nerves of the same arteries in rabbits with the II and IV stages of the malignant Brown--Pearce tumor have been studied. Periarterial neural fasciculi, fibers and terminal branches have been revealed. According to ultrastructure of their cytoplasmic matrix, they can be divided into adrenergic, cholinergic or sensitive. When the malignant tumor is growing, the arterial neural formations undergo certain distrophic-destructive changes; they are especially pronounced in the membranous structures of the neural elements. Their cytoplasmic and basal membranes are partly or completely destroyed. In mitochondria the matrix is altered, some of them are vacuolized. Neurotubules and vesicles change their form and size and are partly destroyed. Membranous structures of lemmocytes are altered. The electron microscopic investigation adds something new to our data on ultrastructural changes in the arterial neural formations under growth of the malignant tumor previously obtained by means of neurohistological and neurohistochemical methods.