Technology and application of ultraminiature catheter pressure transducers.

After a brief historical account of the methods for pressure measurements in the cardiovascular system, the basic structural elements of a new generation of miniaturized catheter pressure transducers are described. These catheters have an outside diameter at the tip of 0.9 mm (3 French) and have been routinely applied in left and right heart catheterization in intact, anesthetized rats. Together with cardiac output measured by the thermodilution technique, a complete set of basal functional parameters can be obtained in vivo. The method of cardiac catheterization in rats is accurate, reliable and easy to perform. As to left heart function, changes occurring in several models of cardiac hypertrophy and heart failure have been recorded and correlated with morphological and metabolic alterations. In addition, the functional effects of catecholamines and thyroid hormones have been evaluated. In addition to the routine catheterization procedure, a double catheter method has been introduced recently, which allows measurement of left ventricular isovolumetric pressure in intact rats. Catheterization of the right ventricle requires a more refined catheter with a characteristic bend at the tip so that it can be comfortably slid from the right atrium into the right ventricle. With this method it was found that right ventricular systolic pressure was elevated markedly in rats with chronic myocardial infarction induced by ligation of the left anterior descending coronary artery, by pulmonary artery banding, by intermittent chronic hypoxia and by noradrenaline administration. The ultraminiature catheter pressure transducer has also been successfully applied in an isolated working rat heart preparation. Recent modifications of this kind of catheters also enabled the catheterization of the left ventricle in mice. Future applications of ultraminiature catheter pressure transducers may be directed to catheterization of the pulmonary artery in rats and to the in vivo and in vitro assessment of heart function of transgenic mice.