Quantitative Assessment Of Cardiac Function With Strain And Tissue Doppler Imaging In Pigs. Comparison With Pressure-volume Loops

ObjectiveThere is currently no optimal method for quantifying regional myocardial systolic dysfunction by echocardiography.Tissue Doppler imaging(TDI)- derived strain rate and strain measurements are new quantitative indices of intrinsic cardiac deformation.The aim of this study was to validate and compare these new indices of regional cardiac function to measurements of pressure-volume loops as an independent gold standard.Material and MethodsAnimal PreparationTen male pigs weighing 23.4 to 30.2 kg were anesthetized,intubated,and mechanically ventilated.An ear vein was cannulated for infusion purposes.A balloon catheter was advanced into the inferior vena cava through the right femoral vein.The balloon was inflated to reduce venous return and decrease preload.The thoracic aorta was cannulated with a catheter in the right femoral artery.The aortic balloon was inflated to cause an occlusion and increase the afterload of LV.Insert jugular vein catheter to record right atrial pressure.A high-fidelity pressure catheter was advanced into the LV (retrograde from the right carotid artery through the aortic valve) to record pressure volume loop and recordings were taken at end expiration.From a surface ECG the heart rate was monitored.Double Desflurane decreases contractility and Infuse Adrenaline increase contractility.echocardiographyIn 10 anesthetized pigs,transthoracic ehocardiography was performed.All studies were acquired with the use of a Vivid 7 digital ultrasound scanner(GE Medical Systems). After views were optimized in fundamental mode,images were acquired in TDI mode. Both myocardial velocities and strain values could be assessed from the same heartbeat. Myocardial longitudinal strain was measured on apical four chamber view of left ventricle (LV) and myocardial radial strain was measured on parastemal short axis view of LV.3 cardiac cycles were stored in cineloop format.The studies were stored digitally for subsequent offline analysis.Analysis of strain imagines(SI) and TDI images was performed offline on a personal computer with the aid of a customized software package (Echopac,GE Medical Systems).Peak longitudinal strain was assessed from the basal, mid,and apical segments,using the same regions as for peak systolic myocardial velocity measurements.Peak radial strain and peak systolic myocardial velocity were measured from interventricular septum and posterior wall of LV.Statistical AnalysisValues are expressed as the mean±SD.Comparisons between values by echocardiography and PV loop were performed by linear regression analysis.Differences between myocardial peak systolic strains and peak velocities in each myocardial segment were analyzed with paired Student's t tests.Comparisons of myocardial peak systolic strains and velocities at baseline and different hemodynamic were analyzed with one-way ANOVA methods.A value of P less than 0.05 was considered statistically significant.ResultsThere is a good correlation between the echocardiographic values and PV loops.In normal condition,longitudinal strain and myocardial Doppler velocities decreased progressively from base to apex.Myocardial strain and Doppler velocities were changed under different hemodynamic conditions in all segments.Like myocardial Doppler velocities,strain is load-dependent.ConclusionsMyocardial strain and velocity by Doppler echocardiography may represent a new, powerful method for quantifying regional myocardial function noninvasively in pigs under different conditions. ObjectiveThis study was done to estimate the left ventricular regional systolic function using strain and strain rate imaging in patients with coronary heart disease(CHD) before and after intracoronary stent implantation.Material and methodsThirty patients with coronary heart disease were scanned by conventional echocardiography and dynamic tissue velocity imaging(TVI) at the day before and the seventh day after intracoronary stent implantation,twenty healthy people as control.Left ventricular ejection fraction(LVEF) was measured by Simpson's method.The dynamic tissue velocity imagings(TVI) were obtained at apical four-chamber view,apical two-chamber view and apical longitudinal view.Septal,lateral,anterior,inferior, anteroseptal and posterior walls were divided into basal,mid and apical segments respectively.The systolic peak strain(ε) and strain rate(SR) were measured respectively for basal and middle segments of ischemic myocardium and compared with that of the controls.The relationship between strain and strain rate in different regional wall and contractile function were analyzed in patients with coronary heart disease before and after intracoronary stent implantation.Results(1) The shapes of strain and strain rate-time curve of 235/240 normal myocardial segments were regularity and the systolic peak value of strain and strain rate did not vary with individual.The postsystolic shortening(PSS) wave appeared in 95/240 segments.(2) 360 LV segments were investigated in patients with coronary heart disease,and we found 122 segments with regional wall motion abnormalities by gray-scale two-dimensional and M-mode echocardiography.Compared with normal myocardium,the shapes of strain and strain rate-time curve of 185 segments before operation were deformed and the systolic peak value of strain and strain rate was lower than that of controls(P＜0.05).The postsystolic shortening(PSS) wave appeared in 160 segments before operation.LVEF(0.536±0.084)was lower than controls(0.719±0.061 ),P＜0.05.(3) 188 LV ischemic myocardial segments were improved by intracoronary stent implantation and were investigated after operation.Among 122 segments with regional wall motion abnormalities demonstrated by two-dimensional and M-mode echocardiography,102 segments were accordance with angiographiy ischemic segments. Disceming ischemic myocardium by gray-scale two-dimensional and M-mode echocardiography was 54%sensitivity and 84%specificity.172/185 segments of strain and strain rate abnormalities were accordance with above-mentioned segments.The best cut-off was a value of over 20%normal reference value that predicted ischemic myocardial segments with a 91%sensitivity and 93%specificity.97/102 segments with wall motion abnormalities were improved at the seventh day after operation.The shapes of strain and strain rate-time curve of 169/172 ischemic myocardial segments at the seventh day after operation were nearly normal and the systolic peak value of strain and strain rate were higher than that before operation(P＜0.05).The PSS wave disappeared in 92/160 segments.LVEF at the seventh day after operation(0.582±0.079) were higher than that before operation(0.536±0.084),p＜0.05.ConclusionsSI and SRI can differentiate abnormal perfusion segments from normal ones and can quantitive analyze the left ventricular regional myocardial functional changes.The postsystolic shortening(PSS) may be a fine index to discem ischemic myocardium.