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 (P(LV)) 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 (P(a)) (as a surrogate for P(LV)) in a canine model using automated algorithms. In eight anesthetized mongrel dogs, we simultaneously measured P(LV), LV area, and P(a) (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 μg · mg^-1 · min^-1), and after bolus propranolol (2 mg/kg) with both P(LV) and P(a) 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 E'(es) from P(a) were closely correlated with E'(es) from P(LV) by both the semiautomated and automated methods (r = 0.93; P < 0.01). The relationship between E'(es) obtained from P(a) 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 ondine P(a) 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.