Nuclear ejection fraction measurements with a small crystal detector: methodological investigations

Intra- and Interhospital Repeatability of Radionuclide Left Ventricular Ejection Fraction in Post-Infarction Patients

OBJECTIVE

To evaluate intra- and interobserver and interhospital repeatability of radionuclide left ventricular ejection fraction in post-infarction patients.

DESIGN

The study comprised 131 patients who were examined in three different hospitals 2-7 days post infarction. The radionuclide examinations were conducted in a standardized manner, and different observers carried out repeated measurements blind on the stored raw data.

RESULTS

The coefficients of variation were between 1.5% and 6.2%, and limits of agreement between +/- 0.012 and 0.056. There were no significant differences between the intra- and interobserver or interhospital repeatability in average, but some significant differences between individual observers were noted.

CONCLUSION

The repeatability of LVEF was acceptable, with limits of agreement in the range +/- 0.012-0.056. Some differences between observers and hence hospitals were noted, which may be of clinical relevance.

Oxygen consumption in infants and children during heart catheterization

Oxygen consumption was measured in infants, children, and adolescents during diagnostic heart catheterizations. A total of 825 measurements of oxygen consumption (VO2) was performed in 504 subjects using a semiopen hood system and a paramagnetic oxygen analyzer. In 256 subjects under 3 years of age, body dimensions and heart rate were found to be significant factors for oxygen consumption. The regression equation for both sexes was: VO2/BSA (ml/min.m2) = 3.42.height (cm) - 7.83.weight (kg) + 0.38.HR - 54.1 (r2 = 0.39, SD = 38.7), where BSA is body surface area and HR is heart rate. VO2/BSA was significantly lower in infants less than 3 months of age (133 +/- 33 ml/min.m2) compared with infants of 3-12 months (171 +/- 37 ml/ min.m2; p < 0.01). In 272 children aged 3 years and older and adolescents, gender was a significant factor in oxygen consumption together with BSA and HR. The regression line equation for males was VO2/BSA (ml/ min.m2) = 0.79.HR - 7.4.BSA(m2) + 108.1 (r2 = 0.45, SD = 34.2). The regression line equation for females is VO2/BSA (ml/min.m2) = 0.77.HR - 5.2.BSA(m2) + 106.8 (r2 = 0.43, SD = 34.4). Hematocrit, systemic oxygen saturation, and blood pressure were not significant factors. The predictive value of nomograms for oxygen consumption is limited because of the large interindividual variations not explained by differences in gender, body size, or simple hemodynamic variables. Preferably, oxygen consumption is measured; but if nomograms for oxygen consumption are used for hemodynamic assessment, the wide confidence intervals should be considered.

Comparison between transesophageal Doppler echocardiography and nuclear cardioangiography for the evaluation of left ventricular filling during coronary artery bypass grafting

This study examines the relative contribution of early (E) and atrial (A) filling of the left ventricle. Ten patients were studied under anesthesia before and after coronary artery bypass grafting (CABG) using measurements of the mitral velocity-time integral (VTI) with transesophageal pulsed Doppler echocardiography and nuclear angiocardiography simultaneously. Thermodilution cardiac output measurements were made simultaneously in order to express the E and A filling in quantitative terms. The mean difference between methods in estimating E filling was -1.0 mL and the figures for the mean +/- 2 SD were 5.7 and -7.8 mL, r = 0.98 using regression analysis. The mean difference during A filling was 0.9 mL and the corresponding figures for the mean +/- 2 SD were 7.9 and -6.1 mL, r = 0.88. There was a reduction in the volume entering the left ventricle during the E filling (42-26 mL) and in the A phase (27-22 mL) from before surgery in comparison to after CABG. There was good agreement between transesophageal Doppler echocardiographic and nuclear angiocardiographic methods concerning the volume contribution during E and A phases of left ventricular filling.

A comparative study of five different techniques to reduce left ventricular dysfunction during endotracheal intubation

Thirty-five non-selected, consenting patients were studied during induction of anesthesia before coronary artery bypass grafting. Anesthesia was induced with diazepam, thiopentone and fentanyl, followed by pancuronium. Before induction, 200 MBq Tc 99 m - HSA was given i.v. and ejection fraction (EF) of the left ventricle was measured with a collimated single-crystal probe. The patients were allocated to five groups (seven patients in each) treated with: Group A: nitroglycerin i.v. bolus 4 micrograms x kg-1 given 30-60 s before laryngoscopy; Group B: nitroglycerin i.v. in continuous infusion, 1 micrograms x kg-1 x min-1 started before induction; Group C: two-stage topical anesthesia of the vallecula region and larynx with lidocain; Group D: a combination of nitroglycerin and topical anesthesia (as in Group B and C); and Group E: propranolol i.v. 0.01 mg x kg-1 given 5 min before intubation. All groups reacted in the same way during induction of anesthesia up to the point of laryngoscopy. End-diastolic volume and systemic arterial pressure decreased while cardiac index remained unchanged and EF increased. During laryngoscopy and intubation, however, differences between the groups were evident. Nitroglycerin i.v. as a bolus effectively prevented a reduction in EF and an increase in left ventricular volume. In addition to these beneficial hemodynamic effects, there was a moderate increase in heart rate and a reduction of stroke index. Continuous infusion of nitroglycerin and propranolol i.v. had no effect, since EF fell and left ventricular volume increased. Patients receiving topical anesthesia demonstrated a blunted response to endotracheal intubation with a moderate decrease in EF and an unchanged (Group C) or slightly increased (Group D) left ventricular volume.