Thermal effects of laser and electrical discharge on cardiovascular tissue: Implications for coronary artery recanalization and endocardial ablation

Abstract

To determine the thermal responses of cardiovascular tissues to laser and electrical ablation, and to characterize the effects of different superfusing media and temperatures on target tissue temperatures and resulting extent of tissue injury, 184 laser and 15 electrical discharges were delivered to segments of human and canine aorta and canine ventricular endocardium. Tissue temperatures were measured 2 mm from the point of contact of laser fiber tip and tissue. When superfusing media consisted of whole blood or plasma at room temperature, a standard 40 J laser discharge caused peak arterial temperatures to rise 29.2 +/- 1.6 degrees C and 30 +/- 1.4 degrees C, respectively; however, tissue cooling was significantly slower in blood than in plasma. When saline solution was superfused, tissue temperatures rose by 11.4 +/- 2.2 degrees C, and tissue cooling occurred significantly faster than with either plasma or blood. The dimensions of the resulting aortic lesions were larger when blood (1.69 +/- 0.26 mm) was superfused than when plasma (1.39 +/- 0.04 mm) or saline (0.77 +/- 0.13 mm) was superfused (p less than 0.0001). Similar findings were observed with ventricular endocardium using blood or saline as the superfusing medium. In arterial tissue, superfusion with cold blood or saline solution resulted in lower peak temperature elevations (22 +/- 3.8 degrees C and 13.5 +/- 1.3 degrees C, respectively) and faster tissue cooling after laser discharge. Corresponding aortic lesion sizes were significantly smaller (1.4 +/- 0.03 and 0.5 +/- 0.02 mm, respectively) than when blood or saline medium was superfused at room temperature (p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of blood flow on laser probe temperature in human arteries

“…This apparent decreased efficiency of probe heat generation and thermal ablation in saline can possibly be explained by the fact that saline will remain at 100°C until water is vaporized [3,22]. Despite this, some have advocated adding a saline perfusion during laser angioplasty to minimize vessel wall injury and to improve laser penetration [20,23,24]. However, our findings suggest that saline may act as a heat sink, potentially reducing the effectiveness of the thermal probe by reducing its temperature.…”

“…The results reported here suggest that laser probe temperatures of this level can be attained in blood but not in saline (using argon laser energy and aluminum tipped fibers). Other investigators have reported higher energy requirements for plaque ablation in saline [13,19,20], and Welch et al [21] have reported that lower laser probe temperatures are achieved in water than in blood for the same amount of energy input. This apparent decreased efficiency of probe heat generation and thermal ablation in saline can possibly be explained by the fact that saline will remain at 100°C until water is vaporized [3,22].…”

Excimer laser ablation for valvular angioplasty in pulmonary atresia and intact ventricular septum

“…Serial slides were stained with hematoxylin and eosin, Elastic van Giemsa and in some instances trichrome stains. During the macroscopic and histopathologic examination alike, specific attention was given to evidence of laser induced thermal injury including such as charring [6][7][8][9], edge disruption manifested by ''ground glass'' appearance of cells or shredded cells [9], and vascular (''acoustic'') injury [6][7][8][9]. Our previously published grading score for laser-induced tissue injury [10] was used: Grade 0, Figure 10 depicts the laser catheter as it crossed the atretic pulmonary valve in a specimen of heart from an infant who had PA/IVS.…”