VALVUILAR HEART DISEASE Right atrial pressure-volume relationships in tricuspid regurgitation

Pressure-volume relationships in the right atrium were examined before and after the creation of acute exerimental tricuspid regurgitation in pigs. A 1.3 kHz multielectrode impedance catheter with a measuring current of 4 mA was used to determine instantaneous right atrial pressure and relative blood volume; right atrial dimension was assessed simultaneously with ultrasonic crystals attached to the atrial walls. Impedance volume waveforms and ultrasonic crystal dimensions closely paralleled each other at baseline and after the induction of tricuspid regurgitation. The normal right atrial pressure-volume plot exhibited a figure-of-eight configuration, with an "a-loop" and a "v-loop" corresponding to the a-wave and v-wave of the right atrial pressure tracing. With severe tricuspid regurgitation, atrial pump function was abolished, and the pressure-volume plot exhibited a single clockwise loop, consistent with complete ventricularization of the right atrium. Intermediate degrees of tricuspid regurgitation preserved the figure-of-eight loop, but the size of both the a-loop and the v-loop were increased, consistent with a Starling-type load imposed on the atrium by the regurgitant blood volume. Increased right ventricular afterload mediated by constriction of the pulmonary artery and infusion of methoxamine reversibly converted the right atrial pressure-volume loop from that of mild to that of severe tricuspid regurgitation. Alternatively, constriction of the inferior vena cava and infusion of nitroprusside changed the right atrial pressure-volume loop from that of a severe pattern of tricuspid regurgitation to a less severe type of pattern. Infusion of dobutamine increased the size of the a-loop relative to the v-loop both at baseline and after induction of tricuspid regurgitation. We conclude that tricuspid regurgitation induces changes in right atrial mechanics that can be detected and quantified with an impedance catheter. Circulation 73, No. 4, 799-808, 1986. TRICUSPID REGURGITATION remains a difficult condition to evaluate for severity and effects on circulatory dynamics." 2 Angiographic assessment may be unreliable when the tricuspid valve is crossed with an angiographic catheter. Noninvasive techniques, including contrast echocardiography and Doppler ultrasound, have been shown to be relatively sensitive and specific in the diagnosis of tricuspid regurgitation but have not been fully validated for quantifying the deFrom the Charles A. Dana Research Institute and the Harvard-Thorndike Laboratory of Beth Israel Hospital, Departments of Medicine (Cardiovascular Division) and Radiology, Beth Israel Hospital and Harvard Medical School, Boston. Supported in part by Research Training Grant HL07394 from the USPHS. Michael Miller was a fellow of the Stanley Sarnoff Society for Cardiovascular Research during the conduct of this study. Address for correspondence: Raymond G. McKay, M.D., Cardiovascular Division, Beth Israel Hospital, 330 Brookline Ave., Boston, MA 02215. Received July 24, 1985; revision accepted Jan. 9, 1986. A preliminary report was presented at the 57th Annual Scientific Sessions of the American Heart Association, Miami, November 1984. Vol. 73, No. 4, April 1986 gree of regurgitation.3 In addition, noninvasive quantification of right atrial volume has been difficult because of the anatomic relationships and complex geometry of the chamber. Even if the degree of regurgitation is determined, the clinical significance and optimal therapeutic intervention (medical management vs surgical correction) remain difficult to determine,4 5primarily because tricuspid regurgitation is most often secondary to, or accompanied by, another disease process.'9 The relative contribution of the regurgitant blood flow to the clinical situation may be difficult to assess in the face of right ventricular failure or elevated pulmonary arterial pressure. Normal right atrial function in man and the changes in function induced by tricuspid regurgitation have not been adequately described. This is due in part to the difficulties associated with determining atrial volumes and beat-to-beat changes in volume. '0 Previous reports 799 by gest on M ay 8, 2017 http://ciajournals.org/ D ow nladed from