Normal limits for left ventricular ejection fraction and volumes estimated with gated myocardial perfusion imaging in patients with normal exercise test results: influence of tracer, gender, and acquisition camera.

BACKGROUND: Myocardial imaging with tracers such as technetium-99m sestamibi or thallium-201 is extensively used as a means of measuring myocardial perfusion. With gated acquisition, these tracers can also be used as a means of measuring left ventricular ejection fraction (EF) and end diastolic and end systolic volumes (EDV and ESV, respectively). The objective of this study was to determine the normal range of EF, EDV, and ESV and to evaluate differences caused by either the tracer used, the gender of the patient, or the acquisition camera used. METHODS AND
RESULTS: A total of 1513 consecutive patients (mean age, 60+/-12 years [SD]) who had normal results on Bruce exercise tests had either Tc-99m sestamibi (n = 884) or Tl-201 (n = 629) injected at peak stress. Although all patients were referred for the evaluation of chest pain or dyspnea and many had cardiac risk factors, all had normal exercise capacity corrected for age, no electrocardiographic signs of ischemia, normal results on perfusion scans, and normal wall motion determined by means of quantitated gated single photon emission computed tomography (QGS). Scans were acquired on 1 of 3 different cameras. The mean EF for all patients who had gated Tc-99m sestamibi scans was 63% +/- 9%, not different from patients who had gated Tl-201 scans (63% +/- 9%). However, when the gender of the patient was considered, the mean EF for women was 66% +/- 8% with Tc-99m sestamibi (n = 519), higher than the mean EF for men (58% +/- 8%, n = 365, P<.0001). Similarly, the mean EF for women studied with Tl-201 (67% +/- 8%, n = 326) was higher than that of men (59% +/- 7%, n = 303,P<.0001). Patients with diabetes mellitus (n = 153) had a slightly reduced EF (62% +/- 10%, P<.001). In a subset of 240 patients, 140 patients studied with Tc-99m sestamibi and 100 studied with Tl-201, the EDV and ESV for women (n = 124) was estimated by means of QGS to be lower (57 +/- 17 mL and 19 +/- 11 mL, respectively) than those for men (74 +/- 22 mL-and 29 +/- 13 mL, respectively; n = 116; P<.001 for each comparison). No clinically significant differences in EF or volumes were noted based on tracers used or acquisition camera. For patients with normal results on exercise treadmill tests and perfusion imaging, the lower limit of normal for EF with gated perfusion imaging with QGS was 50% for women and 43% for men. For EDV and ESV, the upper limit of normal was 91 mL and 40 mL, respectively, for women and 119 mL and 55 mL, respectively, for men.
CONCLUSIONS: No significant differences related to either tracer or acquisition camera used were noted for EF, suggesting equivalency for clinical trials for patients with normal results on exercise tests. However, EF, EDV, and ESV determined by means of gated perfusion imaging need to be corrected for gender.