EFFECTS OF REST AND EXERCISE ON CARDIAC BLOOD-VOLUME DETERMINATIONS

Aim: The purpose of this study was to investigate the changes in blood activity during rest, exercise and recovery, and to assess its influe nce on left ventricular (LV) volume determination using the count-base d method requiring blood sampling. Methods: Forty-four patients underw ent rest-stress radionuclide ventriculography; Tc-99m-human serum albu min was used in 13 patients (Group I), red blood cells was labeled usi ng Tc-99m in 17 patients (Group II) in vivo, and in 14 patients (Group Ill) by modified in vivo/in vitro method. LV volumes were determined by a count-based method using corrected count rate in blood samples ob tained during rest, peak exercise and after recovery. Results: In grou p I at stress, the blood activity decreased by 12.6 +/- 5.4%, p < 0.05 , as compared to the rest level, and increased by 25.1 +/- 6.4%, p < 0 .001, and 12.8 +/- 4.5%, p < 0.05, above the resting level in group II and III, respectively. This had profound effects on LV volume determi nations if only one rest blood aliquot was used: during exercise, the LV volumes significantly decreased by 22.1 +/- 9.6%, p < 0.05, in grou p I, whereas in groups ii and ill it was significantly overestimated b y 32.1 +/-: 10.3%, p < 0.001, and 10.7 +/- 6.4%, p < 0.05, respectivel y. The changes in blood activity between stress and recovery were not significantly different for any of the groups. Conclusion: The use of only a single blood sample as volume aliquot at rest in rest-stress st udies leads to erroneous estimation of cardiac volumes due to signific ant changes in blood radioactivity during exercise and recovery.