Effectiveness of holmium laser-assisted coronary angioplasty. The Holmium Laser Coronary Registry.

The efficacy of holmium laser-assisted angioplasty was studied in 365 narrowings in 331 consecutive patients with coronary artery disease. Clinical indications for study were unstable angina pectoris in 140 patients (42%), stable angina in 136 patients (41%), postmyocardial infarction angina in 35 patients (10.5%), silent myocardial ischemia in 11 patients (3%), acute myocardial infarction in 1 patient (0.3%) and undefined in 8 patients (2%). Coronary morphology characteristics by Multivessel Angioplasty Prognosis Study group criteria were type A in 12.6%, type B1 in 34.2%, type B2 in 27.4% and type C in 25.4%. The laser successfully crossed the total length of the narrowing in 85.2%. Procedural success was 94.2%. Laser alone reduced mean percent luminal narrowing from 88 +/- 11% to 57 +/- 22%. Subsequent balloon angioplasty further reduced the mean luminal narrowing to 23 +/- 18%. Major complication rate was 2.7% (death 0.3%, Q-wave myocardial infarction 0.5%, and emergent bypass surgery 2.7%). Six-month angiographic restenosis (> 50% stenosis) rate was 44%.

The interaction between excimer laser energy and vascular tissue.

The effects of XeF1 excimer laser on isolated normal and atherosclerotic aorta were studied. Experiments were performed in flowing water at constant temperature, flow rate, water depth, pulse width (10 nsec), wavelength (351 nm), beam size (1 mm2) and focal length (50 cm). The number of pulses, the pulse energy, and the pulse frequency were varied, and the vascular tissue was studied histologically. The following observations were made: tissue ablation required a minimum threshold pulse energy and was nonlinearly proportional to the number of pulses and the pulse energy delivered; precise tissue ablation occurred at low pulse frequencies, but changes resembling a thermal process were seen as pulse frequency increased; calcified plaque was more photoresistant than atheroma or normal vessel; excimer laser energy was markedly attenuated by blood; and the time interval between pulses and high peak power are related to the precision of ablation by pulsed excimer laser. It is concluded that excimer laser can rapidly and precisely ablate vascular tissue by a photothermal process.

Optimizing strategies for laser angioplasty.

The intrinsic optical properties of normal and diseased vascular tissues and their interaction with continuous wave (cw) and pulsed laser light were investigated to determine the optimal source for laser angioplasty. Both intima and atheromatous plaque demonstrated increasing spectral absorbance at shorter wavelengths (in the near ultraviolet). The relative differences in absorbance between diseased and nondiseased tissues were not sufficient to allow selective ablation of plaque. Atheromatous plaque appears more resistant than normal intima to damage by cw argon laser. The interaction of tissue with a high-power, pulsed ultraviolet laser showed a nonlinear response as pulse repetition rate and pulse energy were varied. From theoretical considerations and our experimental results, we propose that a pulsed ultraviolet laser with 50 millijoules of power per pulse and a repetition rate of 10 pps would be safer and more effective for recanalization than the cw argon laser.

Methionine intolerance: a possible risk factor for coronary artery disease.

Homocystinuria, an inherited disorder associated with premature atherosclerosis, represents a severe form of methionine intolerance. To analyze the importance of milder forms of methionine intolerance in the genesis of vascular disease, the relation between provokable methionine intolerance and coronary artery disease was investigated. In a group of 138 men, aged 31 to 65 years (mean 53), referred for cardiac catheterization, plasma homocystine was measured before and 6 hours after an oral l-methionine load (0.1 g/kg). Thirty-nine subjects found to have normal coronary arteries had a mean post-load plasma homocystine level of 0.59 +/- 0.37 mumol/liter. A criterion at the 95th percentile (1.64 SD above the mean) was selected and applied to the remaining 99 subjects with coronary artery disease (0.70 +/- 0.68 mumol/liter). Sixteen (16%) of 99 subjects with coronary artery disease exceeded this level as compared with 1 (2%) of 39 subjects without coronary artery disease (p less than 0.04). The risk of coronary artery disease in men with provokable methionine intolerance was increased sevenfold as estimated by the odds ratio. By correlation matrix and multivariate regression analyses, provokable homocystinemia was predictive of coronary artery disease and was independent of tobacco smoking, hypertension, diabetes mellitus, serum cholesterol and age. It is proposed that men with mild methionine intolerance exposed to the high methionine content of the Western diet may develop intermittent homocystinemia and thus may be at greater risk for the development of coronary artery disease.

Selective absorption of ultraviolet laser energy by human atherosclerotic plaque treated with tetracycline.

Tetracycline is an antibiotic that absorbs ultraviolet light at 355 nm and preferentially binds to atherosclerotic plaque both in vitro and in vivo. Tetracycline-treated human cadaveric aorta was compared with untreated aorta using several techniques: absorptive spectrophotometry, which demonstrated a distinct absorptive peak at 355 nm in tetracycline-treated plaque that was absent in treated normal vessel; ultraviolet microscopy, which showed that treated atheroma acquired the characteristic fluorescence of tetracycline under ultraviolet light; and tissue uptake of radiolabeled tetracycline, which showed 4-fold greater uptake by atheroma than by normal vessel. In addition, intravenous tetracycline administered to patients undergoing vascular surgery demonstrated characteristic fluorescence in surgically excised diseased arteries. Because of tetracycline's unique properties, we exposed tetracycline-treated and untreated aorta to ultraviolet laser radiation at a wavelength of 355 nm. We found enhanced ablation of tetracycline-treated atheroma compared with untreated atheroma. The plaque ablation caused by ultraviolet laser radiation was twice as extensive in tetracycline-treated vs nontreated plaque (2.2 +/- 0.25 mm vs 1.3 +/- 0.55 mm, p less than 0.017). This study demonstrates the potential of tetracycline plaque enhancement for the selective destruction of atheroma by ultraviolet laser radiation.