Development of a method for measuring myocardial contractility with gated myocardial SPECT and arterial tonometry

Background. Gated myocardial single photon emission computed tomography (SP ECT) and radial artery applanation tonometry were used, respectively, to qu antify the time-volume curve of the left ventricle and to estimate ventricu lar pressure wave, We developed ways of determining end-systolic elastance (Ees) with the normalized-single-beat method and tested the reproducibility of these measurements. Methods and Results. In patients with coronary artery disease (male/female = 33:2, age 66 +/- 10 years, ejection fraction 22% to 77%), rest thallium-2 01 gated/poststress technetium-99m sestamibi gated SPECT/24-hour rest Tc-99 m sestamibi gated SPECT and arterial tonometry were performed. Quantitative gated SPECT software yielded a systolic time-volume curve, and tonometrica lly measured radial artery pressure wave yielded central aortic pressure wa ve. With systolic half of pressure-volume curve, void volume (Vo) was estim ated and Ees was calculated. Over 71 measurements Ees ranged from 1.7 to 5. 3 and Vo from -4 to 200 mt. Ejection duration, other indexes of central pre ssure waveform, end-diastolic volume, end-systolic volume, and ejection fra ction were reproducible. The reproducibility of Vo was excellent (r = 0.97) . Ees at rest (n = 15) showed fair reproducibility between Tc-99m-sestamibi and Tl-201 SPECT (r = 0.51). Conclusion, With gated myocardial SPECT, a noninvasive method of quantifing myocardial global contractility was developed. Reproducibility of this mea surement was sufficient for use in clinical routine. Ees measured by this m ethod warrants validation by invasively measured Ees.