Prediction of Pulmonary Arterial Pressure in Chronic Obstructive Pulmonary Disease by Radionuclide Ventriculography: Material and Methods
A triple lumen thermodilution 7F Swan-Ganz catheter was introduced into the right internal jugular vein using the Seldinger technique, and advanced under constant pressure wave and fluoroscopic control in the right pulmonary artery. Pulmonary pressure was measured using a physiologic pressure transducer and recorded on a thermal writing recorder. The zero reference was placed at midchest level and values for pressures were averaged for three successive respiratory cycles. Heart rate was derived from a continuously monitored ECG lead. Cardiac output was measured in triplicate by the thermodilution method using a computer. The following formulae were used for hemodynamic calculations: cardiac index (1/min/m*) = cardiac output (L/min) / body surface area (m2); pulmonary vascular resistance index (dyne*s«cm ~ *m2) = 80 x (mean pulmonary arterial pressure—pulmonary wedge pressure)/cardiac index.
Right Ventricular Ejection Fraction techniques
In 16 patients (group 1), RVEF was determined using 8,mKr within the seven days following right heart catheterization. The detailed procedure of the “Kr right ventricular study has been described previously. Briefly, the patient was studied supine, in a 30° right anterior oblique projection. The “”Kr was continuously infused and 16 ECG-gated frames were acquired. Background activity was corrected using “”Tc MAA lung perfusion scintigraphy acquired in the same position immediately after the completion of the gated study. End-diastolic and end-systolic right ventricular ROIs were carefully delineated on the background corrected images taking into account isocount lines and the phase and amplitude images of the first and second Fourier harmonics constructed from the original gated data. In 41 patients (group 2), ECG-gated equilibrium “”Tc RBC ventriculography was performed simultaneously with right heart catheterization. The patient was studied supine in 45° left anterior oblique projection and 16 ECG-gated frames were acquired. End-diastolic right ventricular ROI was delineated following the limits of the ventricular phase area. For background correction, 50 percent of the maximum activity in the right ventricular area in the end-diastolic frame was subtracted on each pixel of the 16 gated-frames. The end-systolic right ventricular ROI was therefore automatically defined. The RVEF was calculated using the classical end-diastolic minus end-systolic over end-diastolic count rates. A three-harmonics Fourier curve fitting was then applied on the corrected right ventricular volume curve; and the following parameters were calculated (Fig 1): pre-ejection period, ms; time to the first third of the systole, ms; time to peak ejection rate, ms; total ejection time, ms; first third ejection rate, counts*s; peak ejection rate, counts*s_I; mean ejection rate, counts*s_l; first third ejection on total ejection, FTE/TE; rapid filing time, ms; slow filing time, ms; time to the first third diastole, ms; time to peak filing rate, ms; total filing time, ms; first third filing rate, counts*s_1; peak filing rate, counts*s_l; mean filing rate, counts*s; and first third filing on total filing, FTF/TF.
Figure 1. Parameters calculated from the right ventricular curve during the systolic and diastolic phases. For the signification of the abbreviations, see methods.