A series of 14 patients with heart failure due to coronary artery disease and impaired left ventricular function underwent radionuclide ventriculography with simultaneous thermodilution measurement of cardiac output by pulmonary artery catheter on two occasions (m1, m2) separated by 6 weeks in order to determine the reproducibility of haemodynamic and left ventricular volume measurements at rest and during supine bicycle exercise. The patients were in NYHA grade II or III and had baseline left ventricular ejection fractions below 40%. Derived haemodynamic variables were calculated from the thermodilution cardiac output and from the radionuclide ejection fraction as follows: stroke volume = thermodilution cardiac output/heart rate; left ventricular end-diastolic volume = stroke volume/ejection fraction; left ventricular end-systolic volume = end-diastolic volume - stroke volume. The percentage difference (PD) between each pair of data (m1, m2) was calculated using the following formula: PD = 100%×(m2-m1)/m1.
The data showed that reproducible measurements of left ventricular volume can be obtained at rest and during exercise. The mean (± S.D.) PD values for end-systolic volume and end-diastolic volume at rest were 0.1 ± 17% and - 0.2 ± 13%, respectively. The mean PD values for end-systolic volume and end-diastolic volume during exercise were - 0.3 ± 19% and - 0.7 ± 15%, respectively. By contrast, the reproducibility of the pulmonary capillary wedge pressure measurements was poor, as reflected by a PD value of 14 ± 51% for exercise pulmonary capillary pressure.
Combining radionuclide ventriculography and the thermodilution measurement of cardiac output is useful for measuring left ventricular volume at rest and during exercise in patients with heart failure. This minimally invasive technique allows for a comprehensive assessment of left ventricular performance and appears to be particularly suited for assessing the effects of therapeutic interventions aimed at minimizing the progressive left ventricular enlargement in heart failure.
© Lippincott-Raven Publishers.