Atsuko Miwa

Percutaneous intracardiac surgery with cardioscopic guidance

The feasibility of a novel catheter system of percutaneous transluminal cardiomyotomy and valvulotomy was examined in anesthetized dogs. The system was composed of a guiding balloon catheter, a cardioscope, and a pair of scissors with or without guide wire at the distal tip. The system without guide wire was introduced into the left ventricle, the balloon was inflated and was pushed against the endocardial surface. After confirmation by cardioscopy, the targeted tissues were incised by the scissors. By these maneuvers, the trabeculae, papillary muscles, and chordae were incised or transected in 7, 6, and 6 of 7 dogs, respectively. The system without guide wire was advanced to the aortic root, the guide wire was introduced into the left ventricle to prevent dislocation of the catheter system, the balloon was manipulated against the aortic cusp and the cusp was successfully incised with cardioscopic guidance in all five dogs. The results indicate that percutaneous transluminal cardiomyotomy and valvulotomy can be performed with cardioscopic guidance.

Comparative studies on transluminal angiomicroscopic and ex-vivo microscopic features of vascular lesions

To visualize small vascular luminal changes which can not be detected by conventional angioscope, a new angiomicroscopy system was developed and its feasibility was examined in anesthetized dogs and isolated human coronary artery. The system was composed of a 3 mm or 4 mm in diameter rigid angiomicroscope (magnification rate: 150 X on a 14 inch monitor), a CCD camera, and monitor television. An angiomicroscope was introduced in retrograde fashion through a sheath into the right iliac artery of anesthetized dogs, and the luminal changes were examined during infusion of saline. Details of the exfoliated endothelium and naked subendothelial layers, and the changes due to vasospasm, could be identified by the system. These changes could more easily be discriminated after staining with Evance blue, Tripan blue or Fucsin. In removed and perfused human coronary artery, small luminal changes due to atherosclerosis could also be identified. By simultaneous insertion of a metallic thread (70 (mu) in diameter) the size of the changes could be calibrated. Light microscopic examination was performed after removal and staining of the targeted portion. It was revealed that 10 (mu) or more in diameter could be discriminated. The results indicate potential use of this angiomicroscopy system for percutaneous transluminal identification of the small vascular changes which otherwise cannot be detected.

Rheological significance of tandem lesions of the coronary artery

SummaryIt is not known whether the individual lesions that constitute tandem lesions of the coronary artery are developmentally or rheologically related. Luminal changes and their rheological significance were examined by percutaneous angioscopy in 44 tandem lesions of 21 patients with ischemic heart disease. Angioscopically, individual narrowing of angiographically documented tandem lesions appeared only as a tangentially expressed prominent portion of an atherosclerotic spiral fold. The directions of the fold were counterclockwise in the proximal to middle segments and clockwise in the distal segment of the right coronary artery, clockwise in the proximal to middle segments and counterclockwise in the distal segment of the left anterior descending artery, and counterclockwise in the proximal to middle segments of the left circumflex artery. The bloodstream always ran along the spiral folds in the tandem lesions. The results suggest that angiographically documented tandem coronary lesions are merely a tangential expression of atherosclerotic spiral folds and that they may act to prevent blood turbulence by generating a spiral laminal flow.

Transluminal angiomicroscopy of arterial thrombosis and thrombolysis

To examine the process of microscopic changes during arterial thrombosis and thrombolysis a novel angiomicroscope (3 or 4 mm in diameter, magnification rate X 145) was introduced through a sheath into the right iliac artery of anesthetized dogs. A small portion of the luminal surface was mechanically damaged and processes of thrombogenesis were examined. Platelet aggregation on the damaged portion, fibrin thread growth on the exfoliated endothelium and naked subendothelial layers, trapping of red blood cells by fibrin networks, and gradual growth of mixed thrombi were observed. Following administration of prourokinase, or t-PA, dispersion of platelet aggregates and red blood cells, simulating sandstorm and gradual melting of fibrin, were also observed. The results indicate that detailed microscopic processes of thrombogenesis and thrombolysis can be observed percutaneously by angiomicroscopy.

Laser irradiation reduces vasoreactivity of coronary artery: implication for prevention of coronary spasm

Vasoreactivity of laser-treated coronary artery was investigated in canine left circumflex coronary artery (LCx). Excimer laser (XeCl 308 nm, 50 mJ/mm2), holmium YAG laser (2.1 micrometers , 150 mJ/pulse), or argon laser (488 nm, 3 W), were used through a single optical fiber. Two 3-mm long segments were obtained from the treated segments and controls in Krebs-bicarbonate buffer. Contraction of LCx was induced with KCl at 30 mM or 3,4 DAP and expressed as developed tension (gram; g). Eighteen dogs were used. Reduction of vasocontactility was observed in excimer treated vessels (0.17 +/- 0.24 g with KCl and 0.34 +/- 0.55 g with 3,4 DAP vs 2.13 +/- 0.85 with KCl and 3.1 +/- 1.9 with 3,4 DAP in control, P < 0.001 respectively), holmium YAG treated vessels (0.43 +/- 0.48 g with KCl and 0.46 +/- 0.24 with 3,4 DAP vs 2.42 +/- 0.49 g with KCl and 3.2 +/- 0.46 with 3,4 DAP in control, P < 0.001 respectively) and argon treated vessels (0.48 +/- 0.79 g vs 4.4 +/- 0.88 in control, P < 0.001). Either pulsed or argon laser irradiation results in loss of vasoreactivity to either constrictive or relaxation agent.

Percutaneous cardioscopy of the cardiac chambers in patients with hypertrophic cardiomyopathy

Recent advances in fiberoptic technology enables us to observe the cardiac chambers percutaneously in various categories of heart disease. We applied cardioscopy in 4 patients with HCM. Two of them presented excessive or good left ventricular function and no history of congestive heart failure (CHF). The other two patients showed reduced left ventricular function with a history of CHF. Cardioscopy was successfully performed in all patients. In patients with excessive or good left ventricular function, the color of the endocardial surface was light brown mixed with white. The trabeculae were significantly thick and contracted vigorously. In patients with reduced left ventricular function, the color was whiter, and the thickness and contraction of the trabeculae were reduced obviously. Myocardial biopsy revealed that interstitial fibrosis was prominent in the latters. These results indicate that (1) cardioscopy is safe and useful for evaluation of the internal surface of the ventricle in patients with HCM, and (2) cardioscopic characteristics of the ventricle are closely related to histopathological features.

Antithrombotic and thrombolytic effects of antithrombin: comparison with either heparin or defibrase

Anti-thrombotic and thrombolytic effects of anti-thrombin agent (Argatroban;Arg 0.5 mg/kg) was evaluated by angioscopy and compared with heparin (250 U/kg). Occlusive thrombus was produced in canine iliac artery by balloon injury. At another side, balloon denudation was attempted at 20 minutes after the administration of the agent. One hour thrombus was control. Angioscopic percent luminal obstruction with thrombus reduced by Arg (from 69 to 32%, P < 0.0001), but not by heparin (from 53% to 59%). Both agents had antithrombotic effects and prevented thrombus formation. The activated partial thromboplastin time (APTT) prolonged to 190% with argatroban and 1253% with heparin (P < 0.0001). Thus, antithrombin agent has both preventive effect of thrombosis and thrombolytic effect without marked prolongation of the APTT.