Laser Therapy of Coronary Artery Obstructions

Needles to promote ventricular blood into the ischemic myocardium applied in a rat heart transplant model: an acute observation [corrected]

Two needles were designed in order to revascularize an ischemic myocardium in the event of left coronary artery occlusion. This study was conducted by performing the Lee modified Fox-Montorsi heart-lung transplant on 25 San Diego Microsurgical Institute-bred Sprague Dawley rats that were subjected to left coronary artery ligation in each case. Of these 25 rats, a straight-porous (SP) needling procedure was applied to 9 heterotopically transplanted rat hearts, and a distinct horseshoe (HS)-shaped needle application was performed on the remaining 16 heterotopically transplanted rat hearts. This report represents an acute study on the efficiency of these two needles to transmit oxygen-rich blood from the left ventricle into the ischemic myocardium. Doppler readings for male vs. female transplants showed that the control peak (PK) and mean (MN) kHz values are on the average of 0.20 kHz higher in males than in females. However, control heart rate values in both sexes are approximately equal. Ligation of the left coronary artery caused a dramatic decrease of PK and MN kHz values in both sexes, while heart rate showed no significant decrease from the original control values in response to ischemia. Application of the SP needle showed only a slight return of PK and MN values in both sexes, but heart rate values increased to levels higher than the original control values. The HS needling procedure was able to recover approximately 80% of the control PK and MN kHz values in both sexes. Thus, these data indicate that the HS needle can successfully transmit left ventricular blood into the myocardium.

Early experiences with laser-assisted thermal angioplasty for peripheral vascular disease

Laser-assisted angioplasty has been used on 47 occasions in 45 patients for the management of atherosclerosis of the superficial femoral and proximal popliteal arteries. Twenty-four procedures were performed to treat disabling intermittent claudication and 23 procedures were performed for a "threatened limb" (rest pain, ischaemic ulceration or digital gangrene). Technical success was achieved in 40 (85%) cases; the mean length of occluded segment was 7.7 cm. The presence of heavily calcified occlusions contributed significantly (P less than 0.001) to technical failure. In 28 (70%) of the successfully treated cases, the recanalized arteries were patent at one month and in 21 (53%) cases they have remained patent during the follow-up period. In five of nine cases with a nine-month follow-up, the arteries still were patent. The mean length of the occluded segments that were treated initially was 7.1 cm in those that remained patent compared with 8.2 cm in those that reoccluded. Thirty-six (77%) patients were discharged from hospital on the day after the procedure. Laser-assisted angioplasty is a promising new technique that is applied best to short-segment, non-calcified occlusions and should reduce the requirement for femoropopliteal arterial bypass surgery.

Effect of CO2 and blood media on laser probe temperature

Blood may limit laser ablation of arterial plaque by decreasing thermal energy transfer from metal-capped probes to arterial occlusions. Since a gas is a good insulator of heat, CO2 may be a better medium for laser recanalization. To study this possibility, a metal-capped fiber was positioned in a segment of blood-filled polyethylene tubing and activated with an argon laser. Probe temperatures were measured in blood and as the blood was displaced by flowing CO2 gas. Probe temperatures were higher at all powers studied in CO2 gas than in blood. Maximum probe temperatures averaged 518 +/- 24 degrees C after CO2 infusion versus 320 +/- 7 degrees C in blood, (P less than 0.0001). Blood aggregate formation was noted on the probe surface in blood but not in CO2 medium. Thus CO2 gas may be a preferable medium for laser recanalization, since higher probe temperatures are achieved, and the probe surface remains free of insulating blood coagulate.

Correlation of coronary angioscopic to angiographic findings in coronary artery disease

An Olympus ultrathin fiberscope, 1.8 mm outer diameter, was inserted intraluminally into 11 stenoses of the left anterior descending and circumflex coronary arteries in 8 patients at coronary bypass surgery. Intraluminal views were obtained by coupling the angioscope to a color video camera and videotape recorder, and compared with preoperative coronary angiographic findings in right and left anterior oblique views. Atherosclerotic plaque was observed as yellow-white mass attached onto the luminal lining, which may be large enough to virtually obliterate the vascular lumen. Angioscopy provided a topographic view and cross-sectional picture of stenosis not observed by angiography. Single-plane angioscopic cross-sectional stenotic lumens correlated well (r = 0.90, p less than 0.001) with calculated angiographic luminal narrowings. However, with subtotal obstruction, lesion length must be assessed angiographically. Coronary angioscopy can be a useful adjunct to angiography by providing the added dimension of the true cross-sectional view of obstruction.

Applicability of laser to assist coronary balloon angioplasty

Severe atherosclerotic obstructed coronary artery disease (CAD) may preclude passage of a balloon catheter for transluminal coronary angioplasty (TCA). Since lasers have been shown to effectively vaporize CAD plaque, the initial application of laser to effect a lumen large enough to accommodate the angioplasty catheter for further dilatation was explored. Eleven postmortem human CAD segments which did not permit passage of a 1.33 mm shaft diameter angioplasty catheter were studied. Argon laser radiation (14 to 90 J) transmitted via 400 micron core diameter quartz fiber onto the stenotic channel of 0.58 mm created a vaporized lumen of 1.77 mm (mean increase of 1.31 +/- 0.25 mm, p less than 0.001). The laser procedure allowed the balloon angioplasty catheter to be pushed into the stenosis. TCA was then performed (7 atm, 45 seconds) and expanded the channel to 2.12 mm (additional mean increase of 0.38 +/- 0.07 mm, p less than 0.001). In terms of percent luminal narrowing, laser radiation reduced obstruction from 80% to 45% (mean difference of -38.7 +/- 4.6%, p less than 0.001), and TCA caused a further decrease to 37% (mean difference of -9.3 +/- 1.9%, p less than 0.001). Thus, in tight atherosclerotic lesions, the laser may be useful in creating an initial opening enabling the placement of the balloon angioplasty catheter which, in turn, can further dilate the lased stenotic coronary lumen.