A new perspective on an old method: gated SPECT imaging for left ventricular contractile function assessment.

The ejection fraction (LVEF) is a commonly used marker of left ventricular function. However, because it is strongly influenced by loading conditions, it can be inaccurate in representing cardiac contractility. We therefore evaluated a gated SPECT based tool to simultaneously assess preload, afterload, and contractility. Using gated SPECT-determined ventricular volumes and arterial tension measurements, we calculated ventricular and arterial elastance (Ev and Ea), as well as end-diastolic volumes, which are surrogates for contractility, afterload, and preload, respectively. We applied this protocol to 1462 consecutive patients and assessed the ventricular function in patients with and without myocardial infarction. The median LVEF was 68% (IQR 62-74%). Patients with infarction exhibited decreased contractility (ventricular elastance of 3 mmHg/ml vs. 6 mmHg/ml), compensated by an increase of preload (end-diastolic volume of 100 ml vs. 78 ml) and a decrease in afterload (arterial elastance of 1.8 mmHg/ml vs. 2.2 ml/mmHg). These interactions yielded a preserved ejection fraction in both groups. Gated SPECT-measured volumes were consistent with values reported in the literature. In addition, the combination of nuclear imaging and arterial tension measurement accounted for not only the ejection fraction but also the loading context, providing a more accurate representation of cardiac contractility.

Ventricular-arterial coupling assessment using gated single-photon emission computed tomography: relationship with reserve pulse pressure and repolarization abnormalities.

AIMS: In patients with normal myocardial perfusion, ST-segment depression and reserve pulse pressure (rPP) can identify patients at higher risk of cardiovascular events. We aimed to explore the prevalence of impaired ventricular-arterial coupling (VAc) in patients with normal myocardial perfusion imaging and its relationship with ST-segment depression and rPP. METHODS AND RESULTS: The present study included consecutive patients with normal myocardial perfusion imaging by single-photon emission computed tomography and ST-segment depression. Stroke volume, end-systolic pressure, arterial elastance (Ea), ventricular elastance (Ev), and VAc (Ea/Ev) were estimated both at rest and during stress. The difference between stress and rest (ΔVAc) was calculated. A positive ΔVAc was considered an impaired ΔVAc (iVAc). RESULTS: A total of 92 patients were prospectively included. iVAc was identified in 44 (59%) patients with ST-segment depression compared with 3 (16%) patients with normal repolarization (P=0.001). A higher incidence of abnormal rPP was identified in patients with ST-segment depression compared with the control group (61 vs. 16%, P=0.0001). ST-segment depression was identified as the only independent predictor of iVAc (adjusted OR 7.5; 95% CI 1.9-30.0, P=0.004). CONCLUSION: Noninvasive assessment of VAc is feasible with gated single-photon emission computed tomography and appears to be related to ST-segment depression and reserve rPP.