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A method to assess the degree to which an atheroma plaque has been disrupted by percutaneous interventional methods could be of considerable benefit. An intravascular ultrasound catheter could provide quantitative information about the distribution and quality of the atheroma prior to and following a balloon dilatation, laser, or atherectomy procedure. Additionally, the ultrasound transducer could be configured within an angioplasty balloon to visualize the arterial wall in cross section during the dilatation. Visualization of the atheroma and arterial wall also might be of benefit to help characterize the type of tissue within the plaque, which may potentially help suggest which of several alternative therapies may be most effective. The intravascular imaging catheter would provide a feasible method of identifying normal and diseased arterial wall structures during diagnostic and interventional angiographic procedures. This distinction is critical during laser therapy of eccentric plaques to prevent exposure of the uninvolved wall (Fig. 7). These high quality ultrasound images may allow quantitative assessment of the extent of atheromatous involvement of artery walls as well as the character of the atheroma tissue. Such an approach, performed percutaneously in the catheterization lab, could represent a fundamental departure from traditional angiographic methods for assessing the severity of coronary, carotid, or peripheral arterial disease.

The application of noninvasive techniques to the evaluation of cardiac function in iron overload has identified a high incidence of abnormalities in asymptomatic patients prior to the onset of overt cardiac deterioration. Of the tests we have used, radionuclide cineangiography appears to be the most sensitive because it can be conveniently applied during the physiological stress of exercise. Other tests of cardiac function that include stress are also likely to be more sensitive than resting measurements of cardiac function. Systematic application of these techniques to the study of patients on iron chelation therapy should results in an early determination of the efficacy of such treatment.

Phycocyanin is a phycobiliprotein with peak absorption at 620 nm. The laser activation, cytotoxic effects, and uptake into atherosclerotic plaque of phycocyanin was studied. Optimal activation was produced by argon dye laser at 0.5 W and a total energy dose of 300 J/cm2 at 620 nm and 650 nm, irradiated through blood with a hematocrit of 8%. Activation was evidenced by reduction of optical density by 0.3 units at 340 nm caused by oxidation of the reduced nicotinamide adenine dinucleotide phosphate (NADPH) in a buffered reaction solution containing 0.1 mg/ml of phycocyanin. Cytotoxicity was evaluated by measuring viability of mouse myeloma cells in culture after incubation with phycocyanin (0.25 mg/ml) and irradiated by 300 J/cm2 at 514 nm. After 72 hours post-treatment the cells showed 15% viability compared to 69% and 71% for control cells exposed to laser only or phycocyanin only, respectively. Atherosclerotic artery segments obtained within 5 hours postmortem were perfused with 0.1 mg/ml phycocyanin in oxygenated Krebs Ringer solution at 30 mm Hg for 5 minutes followed by washout with phycocyanin-free Krebs for 10 minutes. Artery sections examined histologically by light and fluorescence microscopy showed specific fluorescence localization within the plaque particularly at the elastic laminae and to a larger extent at the internal elastic lamina but not in the medial muscle layer. In conclusion, phycocyanin is a cytotoxic photosensitizer that exhibits specific binding to plaque and is activated at a wavelength minimally absorbed by blood. These properties suggest potential therapeutic use for plaque localization and regression.