Relationship Between the Right Ventricular Pressure Waveform and the Vasodilator Response of Pulmonary Artery Pressure in Pulmonary Artery Hypertension

ABSTRACT

BACKGROUND AND OBJECTIVES: This study was performed to discern whether the vasodilatory response of pulmonary artery pressure could be predicted by the right ventricular (RV) pressure waveforms, and therefore, from continuous wave Doppler signals of tricuspid regurgitant jet (CWTR). SUBJECTS AND METHODS: Twelve patients with pulmonary hypertension who underwent cardiac catheterization were enrolled. Nitroprusside was infused at a dose of 0.5 microgram/kg/min, with the dosage being increased by 0.5 microgram/kg/min every 5 minutes to a maximum of 4 microgram/kg/min. Cardiac output (CO), pulmonary vascular resistance (PVR), peak systolic RV pressure (Pp), RV pressure at the inflection point (Pi), deltaP (Pp-Pi) and CWTR were obtained before and at the end of the nitroprusside infusion. A positive response to the vasodilator was defined when there was > or =20% change in the mean pulmonary artery pressure at the end of the nitroprusside infusion. RESULTS: Eight patients did not show a positive response (Group 1) while four patients did (Group 2). Mean decrements in Pp following the nitroprusside test were 4.1+/-7.7 mmHg in group 1 and 27.8+/-5.6 mmHg in group 2. There were no significant differences between groups 1 and 2 in baseline CO, PVR or Pp. However group 1 had a significantly higher deltaP than group 2 (29.0+/-10.5 mmHg vs. 13.3+/-3.0 mmHg, p<0.05). In the configuration analysis of CWTR, the slope between the inflection point and peak velocity was linear in group 1, while there was an indentation in group 2. CONCLUSION: Patients with a small difference between Pp and Pi tend to be reactive to a vasodilator and this tendency can be predicted from the configuration of CWTR.