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

• Published in: American journal of physiology. Heart and circulatory physiology Vol. 292; no. 6; pp. H2764 - H2772
• Main Authors: Zhong, Liang, Tan, Ru-San, Ghista, Dhanjoo N, Ng, Eddie Yin-Kwee, Chua, Leok-Poh, Kassab, Ghassan S
• Format: Journal Article
• Language: English
• Published: United States American Physiological Society 01.06.2007
• Subjects: Aged; Biochemistry; Cardiac Catheterization; Cardiology; Cardiotonic Agents; Cardiovascular system; Cineradiography; Coronary vessels; Dobutamine; Elasticity; Electrocardiography; Female; Heart; Heart Diseases - diagnosis; Heart Diseases - diagnostic imaging; Heart Diseases - physiopathology; Humans; Male; Middle Aged; Models, Cardiovascular; Myocardial Contraction; Nitroglycerin; Predictive Value of Tests; Reproducibility of Results; Sensitivity and Specificity; Sodium Chloride; Stress, Mechanical; Stroke Volume; Systole; Ultrasonography; Vasodilator Agents; Ventricular Function, Left; Ventricular Pressure
• ISSN: 0363-6135; 1522-1539
• DOI: 10.1152/ajpheart.00540.2006

1 Department of Cardiology, National Heart Centre, 2 Division of Engineering, Science, and Technology, University of New South Wales-Asia, and 3 College of Engineering, School of Mechanical and Aerospace Engineering, Nanyang Technological University, Singapore; and Departments of 4 Biomedical Engineering, 5 Surgery, and 6 Cellular and Integrative Physiology, Indiana University-Purdue University Indianapolis, Indianapolis, Indiana Submitted 25 May 2006 ; accepted in final form 15 January 2007 Although there are several excellent indexes of myocardial contractility, they require accurate measurement of pressure via left ventricular (LV) catheterization. Here we validate a novel noninvasive contractility index that is dependent only on lumen and wall volume of the LV chamber in patients with normal and compromised LV ejection fraction (LVEF). By analysis of the myocardial chamber as a thick-walled sphere, LV contractility index can be expressed as maximum rate of change of pressure-normalized stress (d */d t max , where * = /P and and P are circumferential stress and pressure, respectively). To validate this parameter, d */d t max was determined from contrast cine-ventriculography-assessed LV cavity and myocardial volumes and compared with LVEF, dP/d t max , maximum active elastance ( E a,max ), and single-beat end-systolic elastance [ E es(SB) ] in 30 patients undergoing clinically indicated LV catheterization. Patients with different tertiles of LVEF exhibit statistically significant differences in d */d t max . There was a significant correlation between d */d t max and dP/d t max (d */d t max = 0.0075dP/d t max – 4.70, r = 0.88, P < 0.01), E a,max (d */d t max = 1.20 E a,max + 1.40, r = 0.89, P < 0.01), and E es(SB) [d */d t max = 1.60 E es(SB) + 1.20, r = 0.88, P < 0.01]. In 30 additional individuals, we determined sensitivity of the parameter to changes in preload (intravenous saline infusion, n = 10 subjects), afterload (sublingual glyceryl trinitrate, n = 10 subjects), and increased contractility (intravenous dobutamine, n = 10 patients). We confirmed that the index is not dependent on load but is sensitive to changes in contractility. In conclusion, d */d t max is equivalent to dP/d t max , E a,max , and E es(SB) as an index of myocardial contractility and appears to be load independent. In contrast to other measures of contractility, d */d t max can be assessed with noninvasive cardiac imaging and, thereby, should have more routine clinical applicability. cardiac mechanics; ventricular elastance; ventriculography; wall stress Address for reprint requests and other correspondence: G. S. Kassab, Dept. of Biomedical Engineering, Indiana-Purdue Univ., Indianapolis, IN 46202 (e-mail: gkassab{at}iupui.edu )