The use of left ventricular end-ejection pressure and peak pressure in the estimation of the end-systolic pressure-volume relationship.

Abstract

The end-systolic pressure-volume relationship (ESPVR) as derived from left ventricular pressure-volume loops has gained increasing acceptance as an index of ventricular contractile function. In animal experiments the ESPVR has been defined as a line connecting the upper left corners of several differently loaded pressure-volume (P-V) loops with a slope parameter Ees and a volume axis intercept parameter V.. In the clinical setting, several variants of the ESPVR have been determined with use of peak left ventricular pressure, end-ejection pressure, and end-ejection volume. The maximum P-V ratio has also frequently been measured. We attempted to determine which of these alternatives resulted in good approximations of the reference ESPVR in eight isolated canine ventricles that ejected into a simulated arterial impedance system with resistance, compliance, and characteristic impedance. We determined various versions of the ESPVR from the same set of beats quickly obtained with little change in inotropic background. To vary ventricular pressure wave forms, each of the arterial impedance parameters was independently controlled at 50%, 100%, and 200% of normal. Against each of the nine combinations of the impedance parameters four P-V loops were obtained under four preloads and from each of the sets offour P-V loops, the reference ESPVR, linear regression of the peak pressure on end-ejection volume (ESPVRPP-EEV), and linear regression of end-ejection pressure on endejection volume (ESPVREEPV) were determined. In addition, the maximum P-V ratio (MPVR) was calculated for each P-V loop. At all combinations of afterload impedance parameters ESPVRPP-EEV was shifted to the left (slope 5.4 vs 5.2 mm Hg/ml, intercept 6.6 vs 7.4 ml) and ESPVREEPV was shifted rightward (slope 5.0 mm Hg/ml, intercept 7.7 ml) from ESPVRREF. These differences, however, were quantitatively very small. MPVR was much smaller than the slope of ESPVRREF (4.0 vs 5.2 mm Hg/ml) and was load dependent. We conclude that as long as the P-V measurements are made under a fixed afterload system and different preloads, ESPVRpp EEV and ESPVREEPV, but not MPVR, can be used to approximate ESPVRREF.

Muscle metaboreflex control of ventricular contractility during dynamic exercise

“…This motivated us to study the effect of MMR on ventricular contractility not only with the ϩdP/dt max approach but also in the pressure-volume plane. Several investigators have demonstrated that the ESPVR, as well as its slope (maximal ventricular elastance), E max , is relatively insensitive under physiological conditions to changes in preload and afterload yet sensitive to changes to the contractile state of the ventricle (5,10,11,15,16,40). In the present study, we observed that from rest to mild exercise, dP/dt max rose significantly, yet this rise was Ͻ5%.…”

“…To overcome these limitations, LV contractility has been studied with the pressure-volume technique. The maximal elastance (E max ), measured as LV end-systolic pressure-volume relationship (ESPVR) obtained under different loading conditions, has been validated by several investigators as a model to evaluate LV contraction and is useful for quantifying inotropic state independent of preload and afterload under physiological conditions (7,10,11,15,17,40,41). Employing the pressure-volume analysis technique, we conducted this investigation in an effort to clarify how the MMR modifies LV contractility during mild and moderate dynamic exercise.…”

Heart failure attenuates muscle metaboreflex control of ventricular contractility during dynamic exercise

“…Moreover, they also are influenced by changes in cardiac mass and morphology. It is widely accepted that the end-systolic pressure-volume relationship, as well as its slope, E max , are relatively insensitive under physiological conditions to changes in preload and afterload yet sensitive to changes to the contractile state of the ventricle (7,14,15,21,22,49). Since E max also is known to be susceptible to changes in chamber size (an increase in cardiac size-volume decreases E max regardless of contractility) (48), we also calculated PRSW [a modification of the Sarnoff's curve that represents the slope of the relationship between stroke work (SW ϭ pressure ϫ volume) and end-diastolic volume (EDV)].…”

“…Ventricular contractility was assessed by employing the slope of the line intersecting the end-systolic pressure-volume relationships (E max : maximal elastance index) and preload-recruitable stroke work index (PRSW) calculated from the stroke work-end-diastolic volume relationship. Both have been shown to be sensitive to changes in ventricular contractility and relatively insensitive to loading conditions, and the latter measure (PRSW) has been shown to be independent of changes in ventricular chamber size (9,14,15,21,23,49,50). We hypothesized that in the HF state, the muscle metaboreflex-induced increase in LV contractility during mild and moderate dynamic exercise would be impaired as shown by a smaller rise or no change in E max and PRSW.…”

Single-Beat Estimation of End-Systolic Elastance Using Bilinearly Approximated Time-Varying Elastance Curve

“…The E es and V 0 were calculated by an iterative linear regression method. 17,18 We excluded the first 5 beats to avoid the possible effects of changes in parallel conductance associated with alterations in right ventricular volume. …”