title: Validation of a novel noninvasive cardiac index of left ventricular contractility in patients.
abstract: 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 sigma*/dt(max), where sigma* = sigma/P and sigma and P are circumferential stress and pressure, respectively). To validate this parameter, d sigma*/dt(max) was determined from contrast cine-ventriculography-assessed LV cavity and myocardial volumes and compared with LVEF, dP/dt(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 sigma*/dt(max). There was a significant correlation between d sigma*/dt(max) and dP/dt(max) (d sigma*/dt(max) = 0.0075 dP/dt(max) - 4.70, r=0.88, P<0.01), E(a,max) (d sigma*/dt(max) = 1.20E(a,max) + 1.40, r=0.89, P<0.01), and E(es(SB)) [d sigma*/dt(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 sigma*/dt(max) is equivalent to dP/dt(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 sigma*/dt(max) can be assessed with noninvasive cardiac imaging and, thereby, should have more routine clinical applicability.
authors.affiliation: Department of Cardiology, National Heart Centre, University of New South Wales-Asia, Singapore.
authors.forename: Liang
authors.initials: L
authors.lastname: Zhong
authors.forename: Ru-San
authors.initials: RS
authors.lastname: Tan
authors.forename: Dhanjoo N
authors.initials: DN
authors.lastname: Ghista
authors.forename: Eddie Yin-Kwee
authors.initials: EY
authors.lastname: Ng
authors.forename: Leok-Poh
authors.initials: LP
authors.lastname: Chua
authors.forename: Ghassan S
authors.initials: GS
authors.lastname: Kassab
mesh_terms: D000368:Aged; D006328:Cardiac Catheterization; D002316:Cardiotonic Agents; D002933:Cineradiography; D004280:Dobutamine; D004548:Elasticity; D004562:Electrocardiography; D005260:Female; D006331:Heart Diseases / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000503:physiopathology; D006801:Humans; D008297:Male; D008875:Middle Aged; D008955:Models, Cardiovascular; D009200:Myocardial Contraction; D005996:Nitroglycerin; D011237:Predictive Value of Tests; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012965:Sodium Chloride; D013314:Stress, Mechanical; D013318:Stroke Volume; D013599:Systole; D014463:Ultrasonography; D014665:Vasodilator Agents; D016277:Ventricular Function, Left; D017725:Ventricular Pressure
chemical_list: D002316:Cardiotonic Agents; D014665:Vasodilator Agents; D004280:Dobutamine; D012965:Sodium Chloride; D005996:Nitroglycerin