Assessing Left Ventricular Performance

Abstract

T he physiology of conduit arteries can be approximated noninvasively. One simple method to estimate arterial load is by computation of effective arterial elastance (E a ). E a incorporates the steady component (peripheral resistance) and the pulsatile components of arterial load, including total arterial compliance and aortic characteristic impedance. Invasive studies and simulations have shown that E a can be approximated by the ratio of left ventricular (LV) end-systolic pressure to stroke volume in normal and hypertensive human subjects. 1,2 An important practical advantage of the calculation of E a is the merging of all components of arterial load into a single quantitative variable, although it has the limitations of not separating the relative contributions of steady and pulsatile components 2 and of relative sensitivity to variation of heart rate. 3 E a influences stroke volume and is related to LV contractility, as assessed at end ejection by the pressure-volume loop and determination of the LV elastance (E max ). 4,5 Thus, E a has been combined with E max , the slope of a regression line connecting end-systolic pressures and volumes obtained at different loading conditions. The ratio E a /E max is widely used as a measure of LV-arterial coupling. As emphasized recently by Baicu et al, 6 LV function, LV performance, LV contractility, and myocardial contractility are not interchangeable terms. Experimental studies suggest that LV performance, measured as stroke work (SW), 6 is maximal when E max ϭE a . LV performance increases its efficiency when, for a given SW, myocardial oxygen consumption is lower. The optimal efficiency of LV performance is achieved at E a ϭ0.5E max . 5,7 However, beyond these clear-cut limits, there is also evidence that SW may remain near maximal for a broad range of E a /E max values, 7 mostly depending on the magnitude of preload and preload-recruitable SW. 8 In addition to end-ejection phase indices, LV contractility can also be measured by isovolumic phase indices (peak positive dP/dt) and ejection phase indices (end-systolic wall stress versus fractional shortening). Because measures of LV contractility using LV volumes or shortening assess the inotropic state of the LV chamber, they may be influenced by LV geometric changes that alter the relation of the chamber to myocardial contractility. 9 LV Function, Performance, and E a /E max in HypertensionIn this issue of the journal, Osranek et al 10 demonstrate noninvasively that optimal control of arterial hypertension can shift LV work from maximal SW (E a /E max Ϸ1) to optimal efficiency (E a /E max Ϸ0.5). In other words, after optimal control of blood pressure, the lower E a /E max suggests that the left ventricle may develop the same amount of work with much lower oxygen consumption. The authors attribute this dramatic improvement to a possible increase in the coronary blood supply, as suggested by the Buckberg index (ie, the ratio between the diastolic and the systolic areas under the pressure waveform). However, as they rec...

Myocardial Longitudinal Peak Systolic Acceleration (pSac): Relationship to Ejection Phase, Pressure, and Contractility

“…The study demonstrates the insensitivity of most parameters, but stroke work derived indices, in reflecting negative inotropy induced by esmolol, while most parameters do reflect positive inotropy as induced by dobutamine. pSac was insensitive to the changes induced by esmolol which is not uncommon for contractility parameters 18,19 . Important is the fact that acceleration, as measured in this experiment, reflects longitudinal function, while ESPVR, E max , and PRSW are global indices.…”

“…pSac was insensitive to the changes induced by esmolol which is not uncommon for contractility parameters. 18,19 Important is the fact that acceleration, as measured in this experiment, reflects longitudinal function, while ESPVR, E max , and PRSW are global indices. ET was found to be an important determinant of pSac, and negatively correlated with dP/dt max , which is in keeping with the early works of Suga and Sagawa demonstrating that ET shortens with increasing inotropy.…”

“…Homeometric regulation as a result of afterload and heart rate changes are coupled to load dependent mechanisms of contractility. That is why all measured parameters need to be seen in the context of parallel hemodynamic phenomenons 19 . Statistical modeling may compensate for this.…”

“…That is why all measured parameters need to be seen in the context of parallel hemodynamic phenomenons. 19 Statistical modeling may compensate for this. Measurements were performed in a semiautomatic fashion by a single operator and the variance of this method was not tested.…”

Rashomon Effect on the Decision Process of Severe Coronary Artery Pathology: "Coronary Artery Bypass Surgery or Percutaneous Coronary Angioplasty"

“…Whether an invasive or surgical approach or a medical treatment approach is preferred prior to the ischemia trial, perhaps the best strategy is to involve patients in the decision process. 2 The role of the Rashomon effect has been investigated by interesting studies in the medical literature, such as: examination of ventricle function with echocardiography, 9 data collection approaches in scientifi c studies, 10 dual antiplatelet therapy, 11 medical cost, 12 integrated care/teamwork in cardiovascular fi elds. 13 In the fi rst setting, there were two major indication differences between cardiologists and surgeons: PCI and CABG.…”