Continuous measurement of left ventricular volume using a single dimensional transducer: a comparison of two techniques in open chested dogs

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Abstract
A comparison has been made of the continuous measurement of left ventricular volume in open chested dogs by two simple dimensional transducer systems: a mercury in-rubber strain gauge measuring epicardial arc length at the ventricular equator and a pair of electromagnetically coupled coils placed on opposite sides of the left ventricle to measure its diameter. The single dimensional measurements were converted to volume measurements after death by filling an intraventricular balloon with known volumes of liquid. The strain gauge proved clearly superior to the coupled coils because it was not possible in practice to position the coils precisely facing each other and they did not remain tangential to the epicardial surface throughout the cardiac cycle. A single epicardial strain gauge can provide sufficiently accurate measurements of left ventricular volume to warrant its use in physiological studies of cardiac function. Althongh considerable attention to detail is required this technique has the advantages of being inexpensive and producing a continuous record which is easily interpreted.