Application of an end-systolic pressure-segment length relationship for measuring regional contractility
- 17 Downloads
A method for estimating regional contractility is described using the end-systolic relationships between left ventricular pressure and myocardial segment-lengths in rapidly volume-loaded beats. The approach was based on the success of previously developed end-systolic relationships between left ventricular used to describe glopal contractility in beating hearts. The regional end-systolic relationship was more complicated than its global counterpart, which was load independent, and appeared curvilinear to rapid volume loading. As an approximation of this relationship, a linear slope was constructed between maximum and minimum (pre-ejection) loaded beats of equal cycle length. Because of its load dependency and in order to compare slope relationships between interventions, slope functions were derived only from similarly loaded beats either within or between interventions. Slopes generated by this technique had a reasonable constancy at control conditions and coronary flows with an average SEM of 9.1% of the slope means. End-systolic slopes also appeared sensitive to changes in contractile state, increasing appropriately following treatments with dobutamine and decreasing after propranolol. Following shifts in the end-systolic slopes were unreliable, however, in describing the regional changes in contractility with ischemia. At milder levels of flow restriction, the slopes declined as expected. At moderate levels of flow restriction, the pressure-segment loops shifted markedly rightward and the slope increased. At advanced levels of ischemia, the loops were so distorted, that end-systole could not be identified accurately and the loops essentially described the diastolic compliance characteristics of the left ventricle.
Thus the slope estimates of regional contractility as described in this report provided a reliable assessment of inotropic background during modifications with positive and negative inotropic drugs but became invalid as systolic shortening was replaced by aneurysmal bulging high-grade ischemia.
Key wordspositive and negative inotropy dobutamine propranolol regional ischemia working swine hearts
Unable to display preview. Download preview PDF.
- 4.Maughan, W. L., K. Sunagawa, K. Sagawa: Rightward shift of the canine left ventricular end-systolic pressure-volume relation with regional ischemia. Circulation64 IV-230 (1981).Google Scholar
- 12.Schuler, G., K. von Olshausen, F. Schwarz, H. Mehmel, H. Mehmel, M. Hofman, H. J. Hermann, D. Lange, W. Kubler: Noninvasive assessment of myocardial contractility in asymptomatic patients with severe aortic regurgitation and normal left ventricular ejection fraction at rest. Amer. J. Cardiol.50, 45–52 (1982).PubMedGoogle Scholar
- 15.Urschel, C. W., P. S. Vokonas, A. H. Henderson, A. J. Liedtke, L. D. Horwitz, E. H. Sonnenblick: Critical evaluation of indices of myocardial contractility derived from the isovolumic phase of contraction. Cardiol.65, 4–22 (1980).Google Scholar