Estimation of left ventricular elastance without altering preload or afterload in the conscious dog

• Published in: Cardiovascular research 1993-05, Vol.27 (5), p.868-873
• Main Authors: Nakamoto, Takaaki, Cheng, Che-Ping, Santamore, William P, Iizuka, Masahiko
• Format: Article
• Language: English
• Subjects: Animals; Awareness - physiology; Biological and medical sciences; Cardiovascular system; contractility; Dobutamine - pharmacology; Dogs; Echocardiography; haemodynamics; Hemodynamics - drug effects; Investigative techniques of hemodynamics; Investigative techniques, diagnostic techniques (general aspects); left ventricle; left ventricular elastance; Manometry; Medical sciences; Myocardial Contraction - physiology; Reproducibility of Results; Stroke Volume - physiology; Ventricular Function, Left - physiology; Verapamil - pharmacology
• ISSN: 0008-6363; 1755-3245
• DOI: 10.1093/cvr/27.5.868

Objective: The aim was to determine the slope (EES) of the left ventricular end systolic pressure-volume line (ESPVL) without altering preload or afterload in conscious dogs. Methods: Dogs (n=10) were instrumented to determine left ventricular volume from ultrasonic left ventricular internal dimensions, and to measure left ventricular pressure using a micromanometer. Studies were performed one to two weeks after instrumentation while the animals were conscious. ESPVL was determined from variably loaded left ventricular pressure-volume (P-V) loops generated by the vena caval occlusion. Contractile state was increased by intravenous dobutamine (8 μg·kg−1·min−1) and decreased by intravenous verapamil (10 mg) given after autonomic blockade. From a single normally ejecting beat, we calculated EES-single beat (mm Hg·ml−1) as peak isovolumetric pressure (Pmax) minus end systolic pressure divided by stroke volume. Sunagawa's technique was used to estimate Pmax by fitting the pressure during the isovolumetric contraction and relaxation as: P(t)=l/2 × Piso[1-cos(ωt+c)]+LVEDP, where Piso=peak isovolumetric developed pressure, LVEDP=left ventricular end diastolic pressure, c=constant accounting for variations in phase angle, and ω=2 π/T in which T is duration of contraction. Results: After dobutamine, EES increased, from 8.9(SEM 0.8) to 12.5(1.0) mm Hg·ml−1 (p < 0.05), and Epg-single beat increased from 9.1(0.9) to 12.0(1.4) mm Hg·ml−1 (p < 0.05). Conversely, after verapamil, EES decreased, from 11.1(1.2) to 6.3(1.1) mm Hg·ml−1, (p < 0.05), and EES-single beat also decreased, from 9.6(1.0) to 7.3(1.2) mm Hg·ml−1, (p < 0.05). Conclusions: EES calculated from one beat is similar to EES determined from variably loaded left ventricular loops and responds appropriately to inotropic stimulation. This technique provides a reasonable method to calculate EES from left ventricular pressure and stroke volume without altering preload or afterload. Cardiovascular Research 1993;27:868-873