Intercalative Angiography

Abstract

Intercalative angiography is the elecItronically controlled spot-filming of an opacified portion of the cardiovascular system. This form of angiography differs from the selective angiography described by Jönsson et al. (1) and by Lind et al. (2) in that the injection of the medium and x-ray exposure are programmed by the electrocardiogram. The electronic sequence is activated by the R-wave of the electrocardiogram, which is recognized by a specially designed cardiac programmer, which discriminates between the P- or T-waves. A refractory period is inserted so that the discharge impulse is delivered at the desired millisecond after the R-wave. This discharge impulse then either initiates a rapidly acting injector or passes through a second timing device which trips off the x-ray exposure. This apparatus was designed for coronary arteriography but has widespread application for other selective angiography technics. Intercalative angiography obviates most of the limitations of the standard cardiovascular x-ray procedures. Because the volume of the injected radiopaque material is small, the injection time is shortened and there is therefore a discrete localization of the substance at the selected site. In addition, the electronically controlled and highly selective x-ray exposure eliminates unnecessary radiation. The purpose of this report is to describe the apparatus and record the experiences gained from its application, the method of procedure, and the characteristics of cardiovascular spot-filming which approach the ideal. Instrument Characteristics (a) Cardiac Programmer: The development of the cardiac programmer began more than four years ago in our laboratories and made possible the study reported by Casten et al. (3). Further developments and modifications have been made since that initial report. This instrument synchronizes injection of the opaque medium with x-ray triggering. The R-wave of the electrocardiogram provides the initiating trigger. This trigger first fires a one-shot multivibrator that has a long enough recovery time to prevent refiring before the next QRS complex. Simultaneously, a scaler circuit is initiated to provide output pulses for every two or four waves. A “count-down” of every wave from one to four can therefore be obtained. A second trigger, in series with the first, is activated by the specified wave. Following this second trigger there is a variable delay circuit which can be preset from 0.01 to 1.5 seconds. After this delay, a similar circuit fires to provide a signal, adjustable within the range of 0.01 to 1.5 seconds, which in turn biases two output thyratrons. These provide power to a solenoid valve, which in turn activates the hydraulic injector piston. (b) Injector: The hydraulic injector is designed for high-speed injection and convenience of operation. It is entirely self-contained and motor-driven with a continuously operating pump. The oil recirculates and may be used an indefinite number of times.