Prediction of Pulmonary Arterial Pressure in Chronic Obstructive Pulmonary Disease by Radionuclide Ventriculography: Discussion
The most commonly used radionuclide parameter is the RVEF. Indeed, correlations have been found between pulmonary arterial pressure and RVEF, but within both the normal and abnormal range, the variability of estimated pulmonary arterial pressure is important and small changes in RVEF may reflect large variations in pulmonary pressure. Therefore, more reliable radionuclide parameters have been sought. Friedman and Holman used regional RVEF during the second half of systole and noted that this improved accuracy in evaluating pulmonary arterial hypertension as compared to the global ejection fraction. However, in their report, accurate and reproducible results were said to require a high degree of proficiency. Marmor et al proposed another index composed by RVEF and right atrial emptying rate. In their hands, this parameter seems to evaluate the severity of pulmonary arterial hypertension very precisely.
We were interested in other radionuclide approaches. First, we used 81mKr radionuclide ventriculography because it solves most of the technical problems posed by classical methods: the surimposi-tion of the heart chambers for equilibrium techniques, the low count rate or low resolution for first pass study, for instance. But the correlation between 81mKr RVEF and pulmonary arterial pressure hardly improved and the range of pulmonary arterial values corresponding to each RVEF was still too large. The use of 8,mKr RVEF as an accurate pulmonary arterial pressure predictor index was thus questioned. Second, the use of right ventricular curve parameters derived from a ““Tc red blood cells ECG gated equilibrium study. Indeed, systolic or diastolic delays, right ventricular ejection or filling speed have not yet been tested as indices evaluating pulmonary arterial pressure. But neither systolic nor diastolic delays could be correlated with pulmonary arterial pressure in our work.