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P133

COMPARISON OF 3 DIFFERENT LASER TECHNIQUES FOR TRANSMYOCARDIAL REVASCULARISATION IN THE PIG

B.H. Walpoth , I. Genyk , B. Aeschbacher , M. Frenz , Th. Schaffner , U. Althaus , T. Carrel

Thoracic & Cardiovascular Surgery, Cardiology, Pathology and Institute of Applied Physics, University Hospital, Berne, Switzerland

Abstract

Objective: Transmyocardial laser revascularisation (TMLR) may be an alternative or additive treatment for end stage coronary artery disease. It often improves patients symptoms despite unknown pathophysiologic mechanisms. The aim of the study was to assess the chronic effects on left ventricular function and histology resulting from 3 different laser modalities.


Methods: In 6 intubated pigs (25 kg) TMLR was performed via left thoracotomy. In 4 randomised left ventricular areas 3 wholes were drilled using the following lasers: 1. CO2, (10.6 µm, 32 J, Heartlaser, USA), 2. Holmium-Yag (2.1 µm, 2 J, Cardiogenesis, USA) with both a fibre ending with a lens or a bare fibre and 3. Erbium (2.9 µm, 0.3 J, IAP, CH). Echocardiography (Sequoia, Acuson, USA) was carried out intraoperatively before and after laser therapy, 1 week postoperatively and before euthanasia following 6 weeks. Histologic evaluation based on 27 sections per laser type included reparative alterations with special emphasis on neoangiogenesis (semi quantitative assessment, score 0--3).


Results: (mean values ± 1 SD):

  • Ventricular perforation in one shot was achieved only with the CO2 laser; Holmium-Yag laser required usually 3 shots and Erbium laser 9 to 12 shots.
  • Early after the TMLR procedure scarce channels could be visualized whereas subsequently no channel was detected by echocardiography or histology. Intra- and late postoperatively cardiac morphology and function did not show significant alterations (LV mass: 94, 88, 89 g and LVEF: 66, 62, 62% respectively).
  • No significant histological differences were evident between the different laser types regarding scar formation and cell density but Holmium or Erbium lasers induced more mechanical damage. A trend to less scar reaction was found for the CO2 as compared to the Holmium-Yag and Erbium laser. Neoangiogenesis was most pronounced with the Holmium-Yag laser, which showed the highest damage when used with a bare fibre.


    • Conclusions: In contrast to the CO2 laser, TMLR can be applied with the Holmium-Yag and Erbium laser through a fibre, thus allowing minimal invasive or thorascopic approach. Disadvantages are that more shots are required to enter the left ventricular cavity. Histologically all laser lesions demonstrate an increased neoangiogenesis after 2 months in the region of the original laser channels which were all closed. The question whether the documented neovascularisation may contribute to improve myocardial metabolism needs further investigation.


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    © 1998 European Association for Cardio-Thoracic Surgery.