RIGHT-VENTRICULAR FUNCTION IN PATIENTS WITH SEVERE COPD EVALUATED FOR LUNG TRANSPLANTATION

Right ventricular function was measured in ten patients with severe CORD (mean FEV(1)=0.48+/-0.2 L/s) as part of an evaluation for single lung transplant (SLT). Right ventricular ejection fraction (RVEF) was determined by two methods: first-pass radionuclide scan by multigated acquisition (MUGA) and by using a fast thermistor tipped RVEF/volumetric pulmonary artery catheter. None of the patients had clinical evidence of active right heart failure, although mild resting pulmonary hypertension (mean pulmonary artery pressure [PAP]=24+/-4 mm Hg) that worsened with minimal exercise (mean PAP=39+/-11 mm Hg) was present, There was a significant difference in RVEF measured by the two methods (mean MUGA RVEF=57+/-10%, mean catheter RVEF=27+/-8%; p<0.00005). RVEF determined by both methods was correlated with hemodynamic and gas exchange variables obtained during rest and at maximal exercise, There were significant, yet inverse, correlations between RVEF measured by catheter and cardiac index measured during exercise (CIex), as well as with exercise pulmonary vascular resistance index (PVRI). There were no significant correlations found between MUGA RVEF and any gas exchange or hemodynamic variables. Significant correlations were found with the catheter-measured right ventricular end-diastolic volume (RVEDV) and CIex (r=0.9 p<0.005), with maximal oxygen consumption during exercise (VO(2)max) (r=0.86 p<0.0025), with exercise stroke volume index (SVI) (r=0.76 p<0.01), and exercise central venous pressure (CVP) (r=0.62 p<0.05). Echocardiographic studies revealed right ventricular dilatation and mild tricuspid regurgitation (TR) in all patients. The strong correlation between RVEDV, CIex, and VO(2)max supports the concept that in these patients, as long as there is no clinical evidence of right heart failure (resting CVP still within normal limits), those with the largest RVEDVs use the Frank Starling principle to their best advantage to remain more functional. Our findings support the concept that in patients with severe COPD, enlarged right ventricles, and TR, the MUGA RVEF best represents the ''total'' volume ejected from the chamber (some volume ejected forwards into the pulmonary artery and some regurgitated backwards through the tricuspid valve). The catheter RVEF best represents the fraction of volume ejected forward. This concept explains the significant differences in RVEF found by different techniques in this selected group of patients.