Estimation of Vmax in auxotonic systoles from the rate of relative increase of isovolumic pressure: (dP/dt)kP

Abstract

A B S T R A C T High speed oscilloscopic recordings (4000 mm/sec) of left ventricular pressure (micromanometer) and its first derivative were used to calculate contractile element velocity (Vce) during the isovolumic period of auxotonic beats in anesthetized dogs. At 0.5-2.0 msec intervals of isovolumic systole, Vce was derived as (dP/dt)/kP, where k = 24 cm-'. Plots of Vce and P yielded inverse curves from peak Vce to aortic valve opening pressure which averaged 27 msec in controls, and 11 msec during norepinephrine administration. Extrapolated Vmax, in muscle lengths/second, averaged 3.6 (controls), 3.6 (volume load), and 6.6 (norepinephrine). In each experimental state, Vmax was also determined from force-velocity relations of isovolumic beats (abrupt aortic occlusion) analyzed at 10 msec intervals from conventional pressure recordings.Vmax by both methods correlated well (r = 0.88). While good correlations were also noted between Vmax and maximum dP/dt, (max dP/dt)/integrated isovolumic pressure, (max dP/dt)/peak isovolumic pressure, and (max dP/dt)/kP, only the last two of these successfully distinguished changes between volume load and inotropic stimulation. Thus, assuming an unchanged series elasticity, the contractile state of the auxotonic ventricle may be determined utilizing a single high-fidelity catheter system and high speed recordings of isovolumic pressure. INTRODUCTIONThe contractile state of the myocardium can be characterized by the instantaneous relationship between developed force and contractile element velocity, provided that information regarding muscle length and time are

Extent of Carotid Sinus Regulation of the Myocardial Contractile State in Conscious Dogs

“…The same level of pressure which occurred during isometric contraction, before and after each intervention, was used for this calculation and dP/dt and P were determined at that level of pressure. This technique for evaluating the myocardial contractile state has been described in detail previously (12,19,20).…”

“…8, 9). (12,19,20,23). The classical studies of A. V. Hill demonstrated that the inverse relationship between the force generated and the velocity of shortening is an important property of skeletal muscle (24).…”

“…It has also been utilized to characterize the myocardial contractile state in intact, unanesthetized man (18). Similarly, dP/dt has been employed as an indicator of myocardial contractility and the relationship between dP/dt and developed pressure (dP/dt)/P has recently been demonstrated to be a more useful index since it is relatively insentive to changes in preload and afterload (19,20). Both of these indices (force-velocity relation and (dP/ dt)/P) have been demonstrated to be useful in characterizing inotropic effects in the conscious animal (12) and accordingly were employed in this study to reflect induced changes in the myocardial contractile state.…”

Effects of cardiac depression and of anesthesia on the myocardial action of a cardiac glycoside

“…All isolength points were obtained during the first one-third of ejection. In addition, the effects of peak dP/dt and the relations of dP/dt to developed pressure, i.e., (dP/dt) / (P) were examined (32,33). The latter was calculated as the quotient of dP/dt and left ventricular pressure minus end diastolic pressure; the same level of pressure which occurred during the isovolumetric contraction period, before and after ouabain and in the control, anesthetized, and propranolol-treated animals was used for this calculation and dP/dt was always measured at that level of pressure.…”

Effect of Regurgitant jet Direction on Left Ventricular Diastolic Performance in Patients With Aortic Regurgitation

“…Previous studies have established that the ICT is important in the assessment of systolic function [16] and the IRT in the assessment of early diastolic function [17]. These intervals correspond to periods of active LV chamber contraction and early relaxation [18].…”