Beat-to-beat left ventricular performance assessed from the equilibrium cardiac blood pool using a computerized nuclear probe.

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Abstract
The feasibility, accuracy and reproducibility of continuous beat-to-beat evaluation of left ventricular performance with a computerized nonimaging scintillation probe was assessed in 71 patients. This portable instrument has enough sensitivity to generate a real-time relative left ventricular volume curve using the labeled equilibrium blood pool without electrocardiographic gating. The probe was positioned at the left ventricular and background regions of interest using a systematic series of computerized algorithms and operator routines that were developed and standardized during the initial phase of this study. In each patient, left ventricular ejection fraction was calculated manually from the strip-chart recording in 10 consecutive sinus beats. Beat-to-beat left ventricular ejection fraction determined by the probe correlated well with first-pass studies obtained using a computerized multicrystal scintillation camera (r = 0.92). There was no systematic over- or underestimation, and the correlation was evident over a wide range of first-pass values (15-81%). There was excellent agreement between initial and repeat analyses (n = 58, r = 0.97) and between initial and repeat studies (n = 48, r = 0.94). The absolute variability of beat-to-beat ejection fraction measurements determined from all 710 beats was +/- 5.9% (expressed in ejection fraction units as +/- 2 SD). This technique should provide a reliable means of addressing pathophysiologic questions that require sampling of data directly on a beat-to-beat basis.

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