A new dual-probe system for the rapid bedside assessment of left ventricular function

A mobile dual-probe system has been developed for the rapid bedside measurement of left ventricular ejection fraction (LVEF) from the beat-to-beat count rate variations that occur during the transit of a single radionuclide bolus through the left ventricle (LV). Cardiac output, pulmonary blood volume, and left ventricular end-diastolic volume can also be calculated. The dual-probe system incorporates a central collimated probe for monitoring activity in the LV surrounded by an annular detector collimated in such a manner as to provide simultaneous real-time monitoring of the LV background activity. The LVEFs obtained from this system correlated well with LVEFs derived from conventional single-plane contrast angiography (r=0.90) in a series of 33 patients with coronary artery disease. Positioning the dual probe over the midpoint of the LV is accomplished with standard M-mode ultrasound. Since the method is noninvasive and sensitive to volume changes in the LV, the dual probe is particularly useful for monitoring seriously ill patients as well as those with segmental wall-motion abnormalities.