Left ventricular performance is closely related to the physical properties of the arterial system: Landmark clinical investigations in the 1970s and 1980s.

Left ejection fraction (LVEF)--resulting from the difference between end-diastolic volume (EDV) and end-systolic volume (ESV), divided by EDV--is a poor index of left ventricular (LV) systolic performance due to its dependency on load conditions, inotropic state and LV remodelling. The characteristic impedance of the ascending aorta (Zc) integrates factors opposing LV ejection during the early ejection period when arterial wave reflection can be neglected. Zc is related to the pressure wave velocity (C) and the cross-sectional area of the aorta. The aim is to demonstrate that LV performance and geometry are closely related to the physical properties of the arterial system. LV pressure-volume loops were obtained from simultaneous measurements of LV (or aortic) pressure and LV volume. The slope Ees (also called LV end-systolic elastance) of the ESP-ESV relationship was assessed. Aortic diameters, pressure and flow measurements were synchronized to evaluate C, aortic forward and backward pressure waves, the elasticity of the aorta (Ep) and thereby Zc. In contrast to LVEF, LV end-systolic elastance (Ees), which reflects the stiffness of the chamber at maximal myofilament activation, is relatively insensitive to load conditions and may be considered as an index of ventricular chamber contractility. For a given Ees value, the end-systolic pressure (ESP) determines the LV end-systolic volume. Ees is determined by cardiac myocytes contractility and density, and thereby concentric remodelling. A tight correlation between Zc and the degree of LV concentric remodelling was found in hypertensive and in normal subjects. Zc was found to increase throughout the full lifespan and also with hypertension. Both Zc and wave reflections determine aortic input impedance estimated from the aortic pressure-flow relationship. Increased arterial stiffness resulted in increasing C and overlap of forward and backward waves and thereby in greater pulse pressure and ESP and a greater difference between ESP and diastolic pressure. Ees is an accurate index of LV systolic performance. Besides the inotropic state of myofibers, Ees depends on the concentric remodelling and thereby on the characteristic impedance of the aorta.

Combined dipyridamole-exercise stress echocardiography for detection of myocardial ischemia in hemodialysis patients: an alternative to stress nuclear imaging.

BACKGROUND: Stress nuclear imaging is the noninvasive technique currently used to detect coronary artery disease (CAD) in dialysis patients. Stress echocardiography is recognized as an alternative to stress nuclear imaging for the general population. The aim of this study is to assess the diagnostic accuracy of stress echocardiography for detecting myocardial ischemia in hemodialysis patients. METHODS: Stress echocardiography and stress technetium-99m-tetrofosmin (Myoview; Amersham International Plc) imaging were performed simultaneously for 66 asymptomatic hemodialysis patients in a single session, using a combination of high-dose dipyridamole and symptom-limited exercise. Coronary angiography was performed in 44 patients with at least one abnormal noninvasive test result or who were considered high-risk despite normal noninvasive test results. RESULTS: Results for stress echocardiography were abnormal in 15 patients (22%); stress Myoview, in 14 patients (21%); and coronary angiography, in 12 patients (18%). The sensitivity of stress echocardiography for detecting myocardial ischemia (defined as stress Myoview defect) was 86%; specificity, 94%; positive predictive value, 80%; negative predictive value, 96%; and overall accuracy, 92%. The sensitivity of stress echocardiography for detecting CAD (defined as abnormal coronary angiography result) was 83%; specificity, 84%; positive predictive value, 67%; negative predictive value, 93%; and overall accuracy, 84%. Stress echocardiography and stress Myoview did not differ significantly in overall accuracy for detecting CAD (84% versus 91%; P = not significant). CONCLUSION: In hemodialysis patients, combined dipyridamole-exercise echocardiography is an accurate method to detect both myocardial ischemia and CAD and represents an alternative to stress nuclear imaging.