Percutaneous coronary laser balloon angioplasty: initial results of a multicenter experience.

A multicenter clinical trial was initiated to test the potential safety and short-term efficacy of a percutaneous coronary application of laser balloon angioplasty, which has been shown experimentally to alleviate the common causes (dissection, recoil, thrombus) of suboptimal luminal results of conventional balloon angioplasty. Fifty-five patients, the majority (62%) of whom had relatively high risk lesions, were treated in 10 centers with a laser balloon that was identical in size (3 x 20 mm) to a balloon used for conventional balloon angioplasty performed on the same lesion immediately before laser balloon angioplasty. One or more neodymium:yttrium aluminum garnet (Nd:YAG) (1,060 nm) laser doses of 250 to 450 J were each delivered over a 20 s duration per exposure. Immediately and 1 day after laser balloon angioplasty no significant adverse effects on the arterial lumen were noted in any patient. By computerized image analysis of cineangiograms initial conventional balloon angioplasty failed to achieve a minimal luminal diameter greater than 1.5 mm in 14 patients (25%), including 3 patients with acute closure. However, after subsequent laser balloon angioplasty, minimal luminal diameter exceeded this value in all patients including this subgroup. Overall, minimal luminal diameter increased from 1.74 +/- 0.46 mm after conventional balloon angioplasty to 2.32 +/- 0.31 mm after laser balloon angioplasty (p less than 0.001) with no change found on 1 day and 1 month follow-up angiograms. Thus, laser balloon angioplasty is a safe, effective procedure for improving luminal dimensions after conventional balloon angioplasty.

Laser balloon angioplasty versus balloon angioplasty in normal rabbit iliac arteries.

Reduction of vascular recoil is an important goal of laser balloon angioplasty (LBA), wherein Nd:YAG laser radiation is delivered radially during balloon inflation. To define the acute and chronic effects of LBA on the normal arterial lumen in comparison with those of balloon angioplasty (BA), 36 New Zealand White male rabbits (3-4 kg) were subjected to LBA of an external iliac artery and to BA of the contralateral artery with two 1-minute balloon inflations. During LBA, which was performed during the second balloon inflation, either 300 (n = 26) or 176 (n = 10) J were delivered to achieve high and moderate laser doses, respectively, in different LBA groups. Angiography was performed pre- and post-LBA/BA and subsequently at intervals of either 1, 2, 7, 28, 48, or 223 days. Automated analysis of digitized images was used to measure lumen diameter. No instance of perforation or thrombosis occurred. LBA-treated arteries acutely showed an increase in mean diameter over baseline (+ .5 mm, P less than .01) and that of BA-treated arteries (+ .4 mm, P less than .01). While arteries treated with the high laser dose showed a loss of the initial gain in lumen diameter by 1 month, caused by both extravascular fibrosis of the thinwalled (less than 0.1 mm) artery and mild neointimal proliferation which were not reduced by daily administration of aspirin in seven rabbits, arteries treated with the moderate laser dose retained the increment in mean diameter at 1 month over that of BA-treated arteries (+ .5 mm, P less than .05). Thus, unlike BA, LBA increases luminal diameter acutely and, at a moderate laser dose, chronically.

Computerized axial tomographic reconstruction of coronary tree cross sections from a small number of cineradiographic views.

Three-dimensional reconstruction of the coronary tree from a conventional cineangiographic study is limited, in part, by the small number of available cineangiographic views. The potential utility of a maximum entropy iterative algorithm (MENT) for reconstruction of myocardial planes perpendicular to the axis of cineangiographic rotation from a small number (n = 6-18) of cineangiographic views was tested in vitro. The coronary arteries of postmortem human, canine, and calf hearts were filled with a silicone/thorium oxide mold to simulate in vivo angiographic contrast. Thirty-five-millimeter cineradiographs of each heart were obtained at 10 degrees intervals over 180 degrees about a myocardial central axis of rotation under exposure conditions which simulated the clinical setting. Projection data were derived from cinedensitometric scans across the entire myocardial shadow, perpendicular to the axis of rotation in each view, after 512 X 512 digitization with a vidicon camera/digitizer interfaced to a VAX computer. Comparison of MENT-reconstructed images with corresponding anatomic myocardial cross sections indicate that as few as 6 to 12 views can be used to reconstruct the cross sections of the multiple coronary branches (n = 6-11) within a plane of reconstruction.

Predictors, therapeutic options and long-term outcome of abrupt reclosure.

To ascertain the clinical and procedural factors that relate to the occurrence and management of abrupt reclosure, data on 1,160 consecutive patients who underwent coronary angioplasty between December 1981 and December 1986 were analyzed. Abrupt reclosure occurred in 54 patients (4.7%), developing during the dilatation procedure in 43 patients (80%) and delayed by 11 +/- 2 hours after the procedure in 11 patients (20%). Patients were divided into 3 groups based on subsequent management: (1) 22 patients (40%) in whom the involved vessel was reopened by additional dilatation, (2) 14 patients (26%) in whom the involved vessel was not reopened but the patient was treated medically, and (3) 18 patients (33%) in whom abrupt reclosure was managed by emergency bypass surgery, yielding an overall emergency surgery rate of 1.6%. Patients whose abrupt reclosure was reopened were more likely to have luminal thrombus (54 vs 28%) and less likely to have extensive local dissection after dilatation (14 vs 61%; p less than 0.025) than patients undergoing emergency surgery. Patients treated medically despite continued vessel occlusion were more likely to have collateral blood flow to the occluded zone (54 vs 11%, p less than 0.01) than patients undergoing surgery. While 10 of 18 patients (56%) undergoing emergency surgery sustained a myocardial infarction, all patient subgroups appeared to do well during long-term follow-up.

Laser balloon angioplasty: effect of exposure duration on shear strength of welded layers of postmortem human aorta.

Laser Balloon Angioplasty (LBA) is a technique that may improve the results of balloon angioplasty by thermally sealing arterial dissections and reducing elastic recoil. To define the relationship between laser-exposure duration and the strength of thermal welds made between separated layers of arterial wall, 360 1-cm discs of human postmortem aorta were lased for six different exposure intervals at three different temperature ranges, comparing shear strength of thermal welds in the different groups. Twenty discs were lased to achieve plateau adventitial temperatures of 95 degrees C-104 degrees C (group A), 105 degrees C-114 degrees C (group B), or 115 degrees C-124 degrees C (group C) at each of the exposure periods (5, 10, 15, 20, 25, and 30 sec). A 400-micron fiberoptic coupled to a 1.06 micron continuous wave neodymium:YAG laser was placed perpendicularly 8 mm above the luminal surface of each disc, which had been split midway between the intimal and adventitial surface and reapposed. Mean laser energy ranged 78-378 J delivered in a decremental stepwise fashion to achieve quickly and maintain the target plateau tissue temperature. Mean weld strength increased in relation to both achieved tissue temperature and laser-exposure duration, with at least 10 sec necessary, at temperatures greater than 95 degrees C, for reliable thermal welding. Laser exposure for greater than 20 sec provided no statistical increment in weld strength. In the anticipated clinical performance of LBA, these data suggest that when thermal fusion of disrupted arterial tissues is desired, a laser-exposure duration of 10-20 sec is optimal.

Plaque-media rewelding with reversible tissue optical property changes during receptive cw Nd:YAG laser exposure.

Laser dosimetry for thermal fusion of plaque-wall separations during laser balloon angioplasty (LBA) is dependent upon the optical properties of the atheromatous arterial wall during one or more exposures to cw Nd:YAG laser radiation. An integrating sphere technique was used to measure relative transmission and reflection continuously during irradiation of human postmortem atheromatous aortic sections. Tissue luminal surface temperature was recorded continuously with a thermographic video imager during repetitive 20-30-sec, 8-15-watt exposure of a 3-mm nominal spot. In all specimens, transmission fell progressively during each exposure by 10-70% of baseline values. This effect was reversible with normalization of transmission during the initial phase of each subsequent exposure. Changes in transmission were inversely related to temperature over a 50-170 degrees C range, whereas relative reflection remained constant. Accompanying reversible transmission changes was the observation that the weld strength of plaque-aortic wall separations was unchanged by repetitive laser welding and tissue separation of individual sections. In conclusion, temperature-dependent reversible optical and physical properties of plaque occur during exposure to 1.06 microns cw laser radiation.

Laser balloon angioplasty: effect of tissue temperature on weld strength of human postmortem intima-media separations.

Dehiscence of portions of atheromatous plaques fractured during percutaneous transluminal coronary angioplasty may contribute to both abrupt reclosure and gradual restenosis. Laser balloon angioplasty has been shown to be effective in welding human plaque-arterial wall separations in vitro by heating tissues with a Nd:YAG laser during balloon inflation. To define the potentially useful therapeutic range of tissue temperature required to achieve thermal welds, 220 1-cm diameter discs of human postmortem atheromatous aortic tissue, the intimal plaque of which had been separated from the media, were exposed to 3-25 watts of Nd:YAG laser radiation delivered over a 12-mm2 nominal spot size for 20 seconds via a 400-micron core optical fiber. As measured with a thermistor, adventitial temperature reflected the temperature at the plaque-media junction to within 10 degrees C. The degree of tissue temperature elevation was related to delivered energy, while effective tissue penetration increased to maximum depth of 3 mm at the highest power density. Strength of tissue welds was defined as the force required to shear opposing layers of welded segments. Adventitial tissue temperatures below 80 degrees C were not associated with appreciable welds, while equilibrium temperatures between 95 degrees C and 140 degrees C were consistently associated with effective mean weld strengths, which increased linearly from 25 to 110 g, respectively. Temperatures greater than 150 degrees C were associated with rapid tissue dehydration and charring. These data suggest that the therapeutic range of tissue temperature that provides effective thermal fusion of intima-media separations is broad and that the depth and degree of thermal coagulation can be controlled by manipulation of laser energy delivery.

Laser balloon angioplasty: effect of constant temperature versus constant power on tissue weld strength.

Thermal fusion of intimal plaque with the arterial wall during coronary balloon angioplasty may significantly reduce the incidence of abrupt closure and may reduce the occurrence of delayed restenosis by improvement of luminal size and shape. Although Nd:YAG laser energy has been shown to be effective in the thermal fusion of plaque-arterial wall separations in vitro, the most efficient manner of energy delivery for rapid achievement of therapeutically useful equilibrium tissue temperature during laser exposure has not been defined. A comparison of weld strength achieved was therefore made between two formats of laser delivery: constant power vs. decremental power with an initial high dose followed by the minimal serial decrements necessary to maintain tissue temperature constant for 15 seconds. One hundred sixty-six tissue discs of human postmortem aorta of 11 mm diameter were studied. Intimal plaque was separated from the media, the two layers were juxtaposed, a force of 4 pounds was applied, and a fiberoptic-delivered laser beam was directed perpendicular to the tissue over a 3-mm-diameter nominal spot size. Weld strength was measured as the shear force required to separate completely the two tissue layers. The mean weld strength (75 g) achieved by use of the decremental power format was significantly higher (P less than .01) than the mean strength (32 g and 56 g) achieved by using constant power for 20 and 30 seconds, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Uptake of hematoporphyrin derivative by valvular vegetations in experimental infective endocarditis.

Drugs that localize in valvular vegetations may be useful in the diagnosis and treatment of infective endocarditis. We therefore tested the hypothesis that parenterally injected hematoporphyrin derivative (HPD), which is concentrated in tumors and atherosclerotic plaques, localizes in the vegetations of experimental infective endocarditis. In 14 rabbits, various bacteria were given intra-arterially immediately after injury to the aortic valve. In 12 additional rabbits, sterile vegetations on the aortic valve were produced by the trauma caused by an indwelling catheter that had been in place over a long period. HPD, 2.5 mg/kg, was injected intravenously 1 to 2 days before the animals were killed in six rabbits with sterile vegetations and in seven rabbits with infected vegetations. In all rabbits, multiple vegetations on the aortic valve leaflets were identified. On exposure to ultraviolet light, strong porphyrin fluorescence of all vegetations, whether sterile or infected, was observed only in rabbits given HPD. In two rabbits given HPD 10 weeks after catheter implantation across the aortic valve, however, only mild fluorescence could be detected in healing endocardial vegetations. In frozen sections of HPD-laden lesions, a patchy distribution of fluorescence was observed that was similar to the pattern of HPD localization in atheromatous plaques. Since vegetations in experimental infective endocarditis selectively concentrate HPD, porphyrins could be useful in the diagnosis and treatment of infective endocarditis.

Predicted early failure of cardiac pacemakers.

This paper describes a study on pacemaker longevity carried out on 65 subjects using mostly the Telectronics model 171 and model 173 pacemakers and based on an analysis of pacing rate reduction as a function of time since implant. Three different modes of rundown were observed. The shortest predicted lifetime was 23 months for a model 171 unit. This study was undertaken after the manufacturer and battery companies clearly delineated the existence of the problem and steps to be taken in the follow-up of patients. Careful analysis of medical records of the patients did not yield any correlation between sex, age, indications for implantation, initial pacing threshold, or amount of use of the pacemaker, and the early rundown of these pacemakers. Our study indicated that, in general, the model 173 had a shorter expected lifetime than the model 171. Using a reduction in pacing rate of 5.5 bpm from the rate at implant as the end-of-life indicator, the study showed that 16% of the model 173 pacemakers would need to be replaced within 3 years of implant and 78% within 6 years of implant. In the case of the model 171 units, 10% would need to be replaced within 3 years of implant and 48% within 6 years. Follow-up of patients with these units should be scheduled to monitor closely the rate of rundown in order to predict replacement dates.