Imaging by Angioscopy

Imaging by Angioscopy

Michael Rees (Bangor University, Wales)
DOI: 10.4018/978-1-61350-095-8.ch007
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Abstract

Within this chapter, the basic clinical and research utilities of Angioscopy are described. Among its paragraphs, an attempt is made to outline the role of angioscopy to the understanding of cardiovascular disease as well as its contribution to the understanding of cardiovascular procedures. Additionally, the techniques, which combine stenting procedures with angioscopy, are detailed.
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Background: History Of Angioscopy

Angioscopy is a technique of direct visualisation of an artery that became commonly used as an intravascular imaging technique in the late 1980’s and early 1990’s (White, Ramee, Collins, Mesa, Jain, & Ventur, 1993). The introduction however, of angioscopy was much earlier and developed from a technique named cardioscopy which was prompted by the need to develop imaging within the heart to supplement or replace other diagnostic methods. The technique of cardioscopy was documented in 1924 (Cutler, Levine, & Beck, 1924). This reference describes that the technique was practised as far back as 1913 by Rhea and Walker who described a rigid cardioscope which had to be held against the mitral valve. These early attempts of visualisation were generally unsuccessful as there was no method for displacing blood from between the scope and the valve despite the fact that the scopes were illuminated with small light bulbs. Later attempts at cardioscopy during the 1930’s used balloons inflated with saline to partially fill the cardiac chamber and displace blood away from the valves (Harken & Glidden, 1932) .For the next decades significant research in this field was carried out in Japan where a number of techniques were developed to combine cutting devices with cardioscopes to perform valvotomy. Most of these devices used saline inflated balloons attached to the scopes to aid visualisation. Cardioscopy developed as a technique during this period as the majority of cardiac surgical procedures were closed heart rather than the later open heart techniques been developed after cardio-pulmonary by-pass. For this reason most of the cardioscopy devices incorporated a knife or other cardiotomy devices to cut the valve.

Experimental devices in the 1950’s were made of transparent plastic (Butterworth, 1951) but were primarily used as research devices and were not implemented in the clinical context. It was generally felt by most surgeons experimenting with these devices that transparent balloons to gain a visual field were more successful than direct viewing instruments or using saline flushing to visualise the heart.

A step forward was achieved in intra-cardiac imaging by the use of fibre-optic endoscopes which were first trialled in 1967 by Gamble and Ennis; they used a large inflatable balloon to displace the blood from the visual field (Gamble & Ennis, 1967). In experimental conditions in an animal model they reported good imaging of the left heart including the aortic valve. An alternative method of visualisation was the displacement of blood by clear fluid. This required a pressurised injection. This method was proved in animal experiments producing clear visualisation of the aortic valve however this was accompanied by drastic methods to reduce cardiac output which could not be reproduced in closed heart surgery in humans (Dee & Crosby, 1977). Pressurised injection of clear fluid in an animal model was also found to cause trauma, an experience which was repeated in early cases of peripheral angioscopy using flexible instruments where fluid irrigation caused rupture of a fragile arterial wall after atherectomy (Vollmar & Storz). Despite all of these early difficulties with technique and instrumentation, angioscopy did develop into a viable adjunct procedure to a significant number of surgical and interventional techniques particularly in peripheral vessels. This was achieved by developments in instrumentation which included the introduction of thin fibre scopes and angioscopes with balloons attached to the scopes and improvements in sterilisation and delivery of clear fluid.

Figure 1.

Coronary angioscope

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