CRITERIA FOR THE ACCURATE INTERPRETATION OF CHANGES IN LEFT-VENTRICULAR EJECTION FRACTION AND CARDIAC VOLUMES AS ASSESSED BY REST AND EXERCISE GATED RADIONUCLIDE ANGIOGRAPHY

Although serial left ventricular ejection fraction and volumetric measurements using gated radionuclide angiography are commonly used to evaluate clinical changes and therapeutic outcomes in individual patients, criteria are not available for accurately interpreting whether a change in any of these hemodynamic measurements is clinically meaningful. Accordingly, the magnitude of inherent variability among sequential measurements of hemodynamic variables assessed by gated radionuclide angiography was investigated in a double-blind placebo-controlled fashion in 39 patients during two placebo periods separated by 6 weeks. All patients analyzed had remained clinically stable during the study period. Although the mean values for all hemodynamic variables between the two placebo periods were minimally changed, the differences in individual patients were striking. Criteria were developed to allow meaningful interpretation of changes in hemodynamic variables by estimating the likelihood that an observed change is due to variability alone. On the basis of this analysis of placebo radionuclide angiographic data, variation due to chance alone is unlikely to account for all variability if a change observed between the two rest gated studies in a patient is greater-than-or-equal-to 7% units for left ventricular ejection fraction, greater-than-or-equal-to 45 ml/m2 for end-diastolic volume index, greater-than-or-equal-to 35 ml/m2 for end-systolic volume index, greater-than-or-equal-to 20 ml/m2 for stroke volume index and greater-than-or-equal-to 1.25 liters/min per m2 for cardiac index. An observed 4% unit change in left ventricular ejection fraction (increase or decrease) after a medical intervention in an individual patient occurs by random variation > 25% of the time. The criteria presented are applicable to clinical practice because they allow precise interpretation of hemodynamic changes measured by gated radionuclide angiography in individual patients whether the change is due to altered clinical status or to a medical intervention.