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J Thorac Cardiovasc Surg 2003;126:1859-1866
© 2003 The American Association for Thoracic Surgery
Cardiopulmonary support and physiology |
a Division of Cardiothoracic Surgery, University of Pittsburgh, Pittsburgh, Pa, USA
b Atrial Arrhythmia Center, University of Pittsburgh, Pittsburgh, Pa, USA
c Medtronic Inc, Minneapolis, Minn, USA
Received for publication December 17, 2002; revisions received April 22, 2003; accepted for publication June 9, 2003.
* Address for reprints: Marco A. Zenati, MD, Division of Cardiothoracic Surgery, University of Pittsburgh, 200 Lothrop St., Suite C-700, Pittsburgh PA 15213, USA
zenatim{at}upmc.edu
OBJECTIVE: A technique for mimicking left atrial atriotomies using an ablation device that can be deployed without cardiopulmonary bypass has been developed.
METHODS: In 12 healthy large (35-50 kg) adult pigs, maze-like ablation lesions were directly applied to the left atrial epicardium on the beating heart. The ablation device is irrigated, with a bipolar "hemostat" morphology, utilizing radiofrequency energy. Prior to and after ablation, left atrial electromechanical properties were measured during sinus rhythm in the latest 5 pigs using percutaneous endocardial catheter electromechanical mapping and intracardiac echocardiography. Pathologic analysis was performed acutely.
RESULTS: All ablation lesions demonstrated conduction block along their entire course. Global left atrial conduction time (49.4 ± 8.8 milliseconds before vs 58.8 ± 9 milliseconds after) and pattern were not significantly altered. Although a significant amount (17.12% ± 9%) of myocardium was either ablated or electrically isolated, ablation was not associated with significant alterations in global left atrial mechanics (left atrium ejection fraction 19% before vs 17% after; pulmonary vein peak flow velocity 1.22 m/s before vs 1.38 m/s after; peak mitral inflow velocity 2.34 m/s before vs 2.64 m/s after), mitral valve function, nor left ventricular function. There was no evidence of atrial thrombus formation. Transmurality was achieved in most lesions with no evidence of charring or barotrauma.
CONCLUSIONS: Utilizing this ablation device, atrial lesions similar to the left component of the Maze procedure were deployed with uniform success in a beating heart without cardiopulmonary bypass or atriotomy and without adverse effects on left atrial electromechanics.
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