Prediction of Pulmonary Arterial Pressure in Chronic Obstructive Pulmonary Disease by Radionuclide Ventriculography: Conclusion
In contrast, Marchandise et al found a correlation between the acceleration time measured by Doppler echocardiography and PAP in patients with COPD. In our study, the time between the onset and peak pulmonary flow velocity is reflected by the difference between time to peak ejection rate and pre-ejection period. This parameter has not allowed an accurate evaluation of pulmonary arterial pressure. The discrepancies between our results and Marchandises suggest that the measurement of systolic and diastolic delays might be less accurate by the isotopic method than by the Doppler technique. This is probably due to the surimposition of the right auricle and the right ventricle. Moreover, the evaluation of mean pulmonary arterial pressure by parameters derived from a right ventricular equilibrium curve rather than the evaluation of pulmonary arterial pressure values during one heart cycle implies less precise measurements because of chest movements and a variability in duration of the heart cycles.
The speed of right ventricular emptying at different moments of the systolic phase decreases when pulmonary hypertension increases in our work. Since the right ventricular contractility either does not change or increases with deteriorating pulmonary function, the decrease of right ventricular emptying speed might be caused by an increase of RV afterload, and thus, of pulmonary arterial pressure. Unfortunately, in our work, those indices correlate to 20 to 25 percent of measured pulmonary arterial pressure and are of no clinical interest for evaluating pulmonary arterial pressure.
Finally, our findings suggest a slightly negative correlation between pulmonary arterial pressure and right ventricular filling speed during the first third of diastole. This slower early filling speed of the right ventricle is probably to be ascribed to a decreased compliance secondary to both muscular hypertrophy and chamber dilation observed in COPD with pulmonary hypertension. In conclusion, our findings show that pulmonary hypertension in patients with COPD affects both the systolic and diastolic phase of the right ventricular function. The isotopic methods proposed do not yet provide a reliable estimation of pulmonary arterial pressure in our patients.