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Articles by S. P Thomas
Total Records ( 2 ) for S. P Thomas
  G Sivagangabalan , J Pouliopoulos , K Huang , M. A Barry , J Lu , S. P Thomas , D. L Ross , A Thiagalingam and P. Kovoor
 

Background— We assessed a novel simultaneous biventricular mapping and ablation approach for septal ventricular tachycardia (VT) in a chronic ovine infarct model.

Methods and Results— In 8 sheep with inducible VT, mapping and ablation were performed 9±3 months after percutaneously induced myocardial infarction, with left ventricular ejection fraction 23±8%. Scar was identified by EnSite Dynamic Substrate Mapping plus CARTO voltage mapping. Thirty VT episodes (cycle length, 235±42 ms) were mapped with simultaneous analyses using EnSite arrays deployed in both the left ventricle and the right ventricle. Short ablation lines were created perpendicular to the breakout pathway along the scar border in the ventricle with earliest activity. If septal VT was still inducible, this line was extended before ablation in the second chamber. The end point of noninducibility of VT was achieved in all animals. The mean difference in delay in noncontact breakout timing between the ventricles was shorter for VT with (n=18) than without (n=12) septal breakout (32±7.8 ms, P<0.001). In 5 of 6 animals, after ablation in one ventricle, septal VT was still inducible with a common breakout site in the second ventricle. After septal ablation in the second ventricle, VT was no longer inducible. In the 6 animals in which septal VT had been ablated, transmural septal ablation was identified at the scar border, with overlapping left ventricular and right ventricular ablation lesions present in 5 of 6 (septal thickness 8 to 17 mm) and left ventricular endocardial ablation being transmural in 1 of 6 (6 mm).

Conclusions— Biventricular scar and VT activation mapping correctly localizes septal VT pathways, directing ablation from one or both septal endocardial aspects. Creation of a transmural septal lesion at the scar border interrupting VT exit points is highly effective at ablating septal VT.

  C. H. C Hsieh , S. P Thomas and D. L. Ross
 

Background— Percutaneous approaches for radiofrequency ablation of ventricular tachycardia (VT) in the left ventricle are typically transarterial retro-aortic, antegrade transmitral via an interatrial septal puncture, or epicardial. However, all 3 approaches may be contraindicated in certain cases. We describe 2 cases of VT ablation in which aortic and mitral valve replacements did not permit utilization of any of these techniques.

Methods and Results— Direct access to the left ventricular cavity was achieved with a percutaneous puncture through the intercostal space overlying the apex in the first case and through a left minithoracotomy in the second. A sheath was then inserted via the Seldinger technique, allowing catheter access for mapping and ablation of the VT. After successful ablation, the sheaths were withdrawn and hemostasis was achieved. A large left hemothorax occurred from the left ventricular apical puncture in the first case. Direct closure with a purse-string suture in the second case achieved hemostasis.

Conclusions— Direct percutaneous left ventricular puncture is a viable option for mapping and ablation of left ventricular VT. A minithoracotomy allows better hemostatic control. This technique has a role when other percutaneous approaches are contraindicated.

 
 
 
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