Left ventricular performance assessed by echocardiographic automated border detection and arterial pressure.

Automated echocardiographic measures of left ventricular (LV) cavity area are closely correlated with changes in volume and can be coupled with LV pressure (PLV) to construct pressure-area loops in real time. The objective was to rapidly estimate LV contractility from end-systolic relationships of cavity area (as a surrogate for LV volume) and central arterial pressure (Pa) (as a surrogate for PLV) in a canine model using automated algorithms. In eight anesthetized mongrel dogs, we simultaneously measured PLV, LV area, and Pa (fluid-filled catheter). End-systolic pressure-area relationships in terms of pressure-area elastance (E'es)] from pressure-area loops during inferior vena caval occlusions were determined during basal conditions (control), dobutamine infusion (5-10 micrograms.mg-1.min-1), and after bolus propranolol (2 mg/kg) with both PLV and Pa by semiautomated and automated iterative regression methods. E'es increased during dobutamine infusion and decreased after propranolol infusion in all animals and with all iterative methods. Estimates of Ees from Pa were closely correlated with E'es from PLV by both the semiautomated and automated methods (r = 0.93; P < 0.01). The relationship between E'es obtained from Pn for the two methods was also closely correlated. Although the automated methods displayed larger differences from the semiautomated iterative technique by Bland-Altman analysis, the change in E'es with all techniques during dobutamine infusion and after propranolol infusion was of similar magnitude and direction among the three techniques. Greater variability with the dobutamine runs was partially due to abnormally conducted ventricular beats that minimized the number of consecutive beats that could be used for these analyses. We conclude that on-line Pa recordings from fluid-filled catheters can be used with echocardiographic automated border detection to rapidly calculate E'es as a means to estimate LV contractility

A system for the on-line acquisition, visualization, and analysis of pressure-area loops

Transesophageal echocardiography is a widely accepted technique for the assessment of left ventricular (LV) function in the operating room, intensive care unit, and cardiac catheterization suite. Not only do the images generated by these systems provide the observer with dynamic viewsof currently ongoing cardiac mechanics, but the computed LV area values obtained by the automated border detection system can be converted to an analog signal and then used to generate pressure-area loops if LV pressure is measured simultaneously. The intraventricular area has been shown to correlate closely with intraventricular volume and to vary proportionately. Therefore, it can be substituted for volume to generate pressure-area loops that display equivalent behavior to external perturbations as pressure-volume loops. Visualization of these waveforms and the values extracted from them, along with the associated hemodynamic values, provide valuable insight into ventricular function and heart-lung interactions. This paper describes a system that was designed and developed to acquire, display, store, and analyze pressure-area loops in addition to other associated hemodynamic signals of interest. © 1994 Academic Press, Inc

Rapid estimation of left ventricular contractility from end-systolic relations by echocardiographic automated border detection and femoral arterial pressure

Background: Automated echocardiographic measures of left ventricular (LV) cavity area are closely correlated with changes in volume and can be coupled with LV pressure to construct pressure-area loops in real time. The objective was to rapidly estimate LV contractility from the end-systolic relations of cavity area (as a surrogate for LV volume) and femoral arterial pressure (as a surrogate for LV pressure) in patients undergoing cardiac surgery. Methods: Studies were attempted on 18 consecutive patients with recordings of LV pressure, LV area, and femoral arterial pressure on a computer workstation interfaced with the ultrasound system. End-systolic pressure-area relations (in terms of pressure-area elastance [E'(es)]) from pressure-area loops during inferior vena caval occlusions were determined before and immediately after cardiopulmonary bypass using both LV and arterial pressure by semiautomated and automated iterative linear regression methods. Results: Data sets were available for 13 patients before and 8 patients after bypass (21 studies in 14 patients). E'(es) by arterial pressure was closely correlated with E'(es) by LV pressure: r = 0.96, standard error of the estimate = 2 mmHg/cm2, y = 1.01 x -0.7 by the semiautomated method and r = 0.94, standard error of the estimate = 3 mmHg/cm2, y = 1.02 x -0.5 by the automated method. Analysis of semiautomated and automated estimates of E'(es) from arterial pressure and E'(es) using LV pressure by the Bland-Altman method showed no systematic measurement bias and calculated limits of agreement of 8 and 9 mmHg/cm2, respectively. Similar decreases in E'(es) by arterial and LV pressure occurred from before to after bypass in 7 patients with paired data sets: 32 ± 12 to 15 ± 6 mmHg/cm2 and 32 ± 15 to 15 ± 7 mmHg/cm2, respectively (P < 0.05 for both). Conclusions: On-line femoral arterial pressure and LV area data by echocardiographic automated border detection may be used to rapidly calculate E'(es) as a means to estimate LV contractility in selected patients