Assessment of Cardiac Contractility

Abstract

SUMMARYIt was considered that the relationship between dp/dt and simultaneously developed pressure during the course of isovolumic contraction might afford a more accurate measure of contractility than the maximum rate of intraventricular pressure rise (peak dp/dt). In six cat papillary muscles contracting isometrically from any given preload, the ratio of the rate of tension development (dT/dt) to simultaneously occurring isometric tension always varied directly with the contractile state. This ratio rose slightly as preload was increased, but it was not affected by changes in afterload. In 17 experiments in an intact canine heart preparation in which left ventricular end-diastolic pressure was constant, dp/dt at any given pressure during isovolumetric contraction again was observed to be a function of the contractile state when the latter was enhanced by norepinephrine and acetylstrophanthidin. High-fidelity left ventricular pressures and dp/dt were recorded throughout isovolumic contraction in eight patients. Isoproterenol and exercise raised the level of dp/dt at any given pressure prior to ejection. Interventions known to alter ventricular loading but not to influence the contractile state, such as elevation of ventricular end-diastolic pressure by leg raising and increases in aortic pressure induced by methoxamine, did not influence this relation significantly. In conclusion, the determination of dp/dt and intraventricular pressure throughout isovolumic contraction in the presence of variable arterial pressure and small changes of preload provides a useful, simple, and experimentally verified approach to the assessment of alterations of the contractile state of the heart in intact man.

The Influence of Preload Measured as Diastolic Mural Force on Myocardial Contractility Indices

“…The LaPlace relation defines force in a hollow body as the product of pressure and radius squared, and has been used by numerous investigators to determine the tension in the ventricular wall (13)(14)(15)(16)(17)(18)(19). Hefner et al demonstrated that this arch measured this product of pressure and radius squared, and subsequent studies by Newman and Walton (10,20,21) have demonstrated (2)(3)(4)10). that values obtained with this arch corresponded with calculated values of wall force, being influenced by changes in ventricular size and/or pressure.…”

“…From the data in Table I1 there appears to be no significant change in this index with changes in preload. However, there is a great deal of variation (1,2,10).…”

“…The index (dP/dt)/CPIP, or as in this study (dP/dt)K. 30, has been considered to be the most reliable index for measuring contractility (2,12) ; therefore, the effects of an increased preload due to increasing blood volume were examined in all dogs using LVEDP as an index of preload as well as ADMF in the 12 dogs in which this was determined. The results of this examination are summarized in Table 11.…”

Validation of a novel noninvasive cardiac index of left ventricular contractility in patients

“…Hence, it is more appropriate to formulate an LV contractility index on the basis of LV wall stress (5,9,24). Numerous methods have been devised to measure LV wall stress (13) or to approximate it by use of geometric models (8,19,36). Measurement of transmural wall stress (with implantable strain gauges) is hampered, however, by the degree of coupling between the transducer and the ventricular wall (5).…”

Left ventricular shape-based contractility index

“…A great deal of effort has been made to assess their specificity and prediction capability (Mason et al, 1971;Peterson et al, 1974;Lambert et al, 1983;Kass et al, 1987;Kass and Beyer, 1993). Most studies have indicated the peak of the first time derivative of the ventricular pressure dP/dt max to be the most sensitive cardiac index of inotropic changes (Kass et al, 1987).…”