Assessment Of Left Ventricular Performance Research Articles

State-of-the-art methodologies used in preclinical studies to assess left ventricular diastolic and systolic function in mice, pitfalls and troubleshooting.

Cardiovascular diseases (CVD) are still the leading cause of death worldwide. The improved survival of patients with comorbidities such as type 2 diabetes, hypertension, obesity together with the extension of life expectancy contributes to raise the prevalence of CVD in the increasingly aged society. Therefore, a translational research platform that enables precise evaluation of cardiovascular function in healthy and disease condition and assess the efficacy of novel pharmacological treatments, could implement basic science and contribute to reduce CVD burden. Heart failure is a deadly syndrome characterized by the inability of the heart to meet the oxygen demands of the body (unless there is a compensatory increased of filling pressure) and can manifest either with reduced ejection fraction (HFrEF) or preserved ejection fraction (HFpEF). The development and progression of HFrEF is mostly attributable to impaired contractile performance (systole), while in HFpEF the main problem resides in decreased ability of left ventricle to relax and allow the blood filling (diastole). Murine preclinical models have been broadly used in research to understand pathophysiologic mechanisms of heart failure and test the efficacy of novel therapies. Several methods have been employed to characterise cardiac systolic and diastolic function including Pressure Volume (PV) loop hemodynamic analysis, echocardiography and Magnetic Resonance Imaging (MRI). The choice of one methodology or another depends on many aspects including budget available, skills of the operator and design of the study. The aim of this review is to discuss the importance of several methodologies that are commonly used to characterise the cardiovascular phenotype of preclinical models of heart failure highlighting advantages and limitation of each procedure. Although it requires highly skilled operators for execution, PV loop analysis represents the "gold standard" methodology that enables the assessment of left ventricular performance also independently of vascular loading conditions and heart rate, which conferee a really high physiologic importance to this procedure.

Determinants of Diastolic Dysfunction in Swine with HFpEF Arising From Transient Repetitive Left Ventricular Pressure Overload

ObjectiveWe recently demonstrated that swine subjected to 2‐weeks of repetitive pressure overload (RPO) exhibit adaptive myocardial remodeling in the absence of left ventricular (LV) hypertrophy. This remodeling is similar to that arising in many patients with heart failure and a preserved ejection fraction (HFpEF). While LV compliance is markedly reduced, the relative contribution of altered myocardial relaxation vs. passive myocardial properties to this is unclear. Accordingly, the objective of the present study was to determine how RPO affects passive myocardial stiffness and active myocardial relaxation, two key components of LV diastolic function.MethodsSwine (n=14) were subjected to 2‐weeks of RPO via daily infusions of phenylephrine (300 ug/min, 2 hours/day). Invasive measurements of LV performance were collected before and after RPO at rest and during alterations in loading conditions elicited by transient manipulation of venous return. To assess reversibility, a subset of animals (n=6) underwent repeat studies 2‐weeks after cessation of RPO. After the final study, myocardial tissue was collected from the LV free wall for post‐mortem assessment of calcium handling protein expression (western blot; n=8), passive myocardial stiffness (uniaxial tensile testing; n=3), and quantification of interstitial fibrosis (picrosirius red staining).ResultsCompared with baseline measurements, 2‐weeks of RPO did not significantly affect the LV relaxation time constant (Tau) or the rate of LV pressure change during isovolumic relaxation (dP/dtmin; Table ). Consistent with this observation, myocardial expression of calcium handling proteins SERCA (from 0.58±0.24 to 0.52±0.25, p=0.62), ryanodine receptor (from 0.37±0.17 to 0.36±0.14, p=0.99), and phospholamban (from 0.46±0.21 to 0.33±0.15, p=0.17) was not different following RPO vs. normal controls (n=8). However, assessment of LV performance under altered loading conditions revealed a significant increase in the LV stiffness coefficient (β) during IVC occlusion as well as the ΔEDP/ΔEDV ratio during rapid saline loading. These functional changes persisted for 2‐weeks following cessation of RPO and were accompanied by a significant increase in passive myocardial stiffness and interstitial fibrosis.ConclusionsThese results demonstrate that the reduction in LV compliance arising after RPO is not related to delayed active myocardial relaxation at rest or altered expression of sarcoplasmic reticulum calcium handling proteins. However, RPO elicits a persistent increase in passive myocardial stiffness that is likely mediated by interstitial collagen deposition. These passive diastolic properties may explain exercise intolerance in HFpEF patients despite normal resting hemodynamics and the absence of anatomic LV hypertrophy.Support or Funding InformationFunding Sources: The National Heart Lung and Blood Institute (HL‐061610), the American Heart Association (17SDG33660200), the National Center for Advancing Translational Sciences (UL1TR001412), the Department of Veterans Affairs (1IO1BX002659), the Community Foundation for Greater Buffalo, and the Albert and Elizabeth Rekate Fund in Cardiovascular Medicine. Baseline/Control RPO Cessation of RPO Tau (ms) 36.5 ± 1.6 35.9 ± 1.6 34.3 ± 1.7 dP/dtmin (mmHg/s) −2116 ± 369 −2301 ± 133 −2464 ± 272 Diastolic Stiffness Coefficient (β) 0.025 ± 0.003 0.054 ± 0.007 * 0.043 ± 0.009 * ΔEDP/ΔEDV During Saline Loading (mmHg/mL) 0.09 ± 0.02 0.21 ± 0.04 * 0.23 ± 0.03 * Ex Vivo Passive Stiffness (kPa) 77.8 ± 11.0 ‐‐‐ 131.0 ± 6.1 * Interstitial Fibrosis (%) 6.6 ± 0.7 12.9 ± 1.8 * 16.3 ± 1.1 * Values are mean ± SEM. *p<0.05 vs. Baseline/Control

Description of a Novel Set-up for Functional Echocardiographic Assessment of Left Ventricular Performance During Ex Vivo Heart Perfusion.

Ex vivo heart perfusion (EVHP) is a new technology aimed at decreasing cold ischemia time and evaluating cardiac function before transplanting a donor heart. In an experimental EVHP swine model, we tested a 3D-printed custom-made set-up to perform surface echocardiography on an isolated beating heart during left ventricular loading. The views obtained at any time point were equivalent to standard transesophageal and transthoracic views. A decrease in left ventricular function during EVHP was observed in all experiments.

Good agreement between echocardiography and impedance cardiography in the assessment of left ventricular performance in hypertensive patients

ABSTRACTBackground: Impedance cardiography (ICG) is a noninvasive hemodynamic monitoring tool which can define hypertensive patients’ hemodynamic profiles and help to tailor antihypertensive therapy. This study assesses the concordance between ICG-derived indexes used to evaluate left ventricular performance and transthoracic echocardiography (TTE) in hypertensive patients. Methods: In this IMPEDDANS post-hoc analysis, the ICG-derived indexes are compared with TTE by Bland–Altman method. Statistical significance of the relationship between the values obtained was assessed by generalized linear mixed-effects models. Results: In supine position, Bland–Altman analysis showed good concordance for cardiac output (CO) (mean difference of 0.006 mL/min [−0.120; 0.133]), cardiac index (CI) (mean difference of 0.016 mL/min/m2 [−0.471; 0.504]), pre-ejection period (PEP) (mean difference of −0.216 ms [−4.510; 4.077]), left ventricular ejection time (LVET) (mean difference of −0.140 ms [−6.573; 6.293]), and systolic time ratio (STR) (mean difference of −0.00004 [−0.008; 0.008]). In orthostatic position, good concordance was found for CO (mean difference 0.028 mL/min [−2.036; 1.980]), CI (mean difference −0.012 mL/min/m2 [−1.063; 1.039]), and STR (mean difference −0.101 [0.296; 0.094]). No significant difference between methods was identified by the linear mixed-effects models. Conclusion: The ICG-derived indexes CO, CI, PEP, LVET, and STR in supine position have good agreement with TTE. Therefore, ICG can be used to accurately evaluate left ventricular performance.

GW28-e0262 Assessment of left ventricular performance in heart transplant recipients by three-dimensional speckle tracking imaging

GW28-e0262 Assessment of left ventricular performance in heart transplant recipients by three-dimensional speckle tracking imaging

Assessment of left ventricular performance in heart transplant recipients by three-dimensional speckle tracking imaging.

To calculate left ventricular (LV) global performance values in heart transplant (HT) recipients by three-dimensional speckle tracking imaging (3D-STI) and to observe the changes in LV global performance over time after HT and investigate the correlated factors.The 30 HT patients were divided into 2 groups according to postoperative time: 1 month postoperatively (HT-1) group and 6 months postoperatively (HT-2) group. Thirty healthy subjects were enrolled as control group. 3D-STI was performed to assess LV torsion, LV systolic dyssynchrony index (SDI), and LV global strain (GS). Global performance index (GPI) was calculated, and correlations factors with GPI were studied.Heart rate (HR), left atrium (LA), interventricular septum thickness (IVST), left ventricular posterior wall thickness (LVPWT), and left ventricular mass (LVM) in both HT groups were higher than those in the control group. Compared with the control group, SDI was significantly higher in both HT groups, and SDI of the HT-1 group was much higher than that of HT-2 group. Compared with the control group, apical rotation (RoA), twist and torsion in the both HT groups decreased significantly. There were no significant differences in these values between the 2 HT groups; Basal rotation (RoB) showed no significantly difference among the 3 groups. GS in the both HT groups decreased significantly compared with the control group, and there were no significant differences in these values between the 2 HT groups. GPI of the both HT groups was significantly lower than that of the control group; however, GPI of HT-2 group was higher than that of HT-1 group. Multivariate stepwise regression analysis identified global left ventricular longitudinal peak systolic strain (GLS), the time length since surgery, left ventricular mass (LVM), and RoA as predictors of LV GPI. GLS was the most influential to GPI.The values of LV rotation, twist and SDI can be used to assess the LV systolic function and dyssynchrony. The GPI value based on 3D-STI may accurately reflect LV performance changes over time after HT. The GPI value has potential applications in clinical practice. GLS, the time length since surgery, LVM and RoA values can be the predictors of LV global performance, and as long as the left ventricular ejection fraction (LVEF) is preserved, the left ventricular global performance of HT recipients remains stable, and tends to improve over time after HT.

Assessment of left ventricular performance in patients with aortic regurgitation: a strain rate imaging study

Background Aortic regurgitation (AR) results in left ventricular (LV) hemodynamic changes ranging from maladaptive hypertrophy and dilatation to heart failure. Conventional echocardiography and tissue doppler imaging are unable to reveal the early abnormalities in LV function caused by AR; however, two-dimensional speckle tracking echocardiography (2D STE) provides an objective way to detect subtle LV changes among AR patients. Objective The aim of this study was to assess functional changes in the myocardium in asymptomatic patients with AR using 2D STE-based strain and strain rate measurement, and its usefulness in early detection of subclinical LV dysfunction. Materials and methods Fifty asymptomatic patients with significant AR and 20 age and sex-matched healthy individuals were examined using conventional echocardiography, tissue doppler imaging, and 2D STE-based measurement of global and segmental LV systolic longitudinal strain (esys), systolic strain rate (SRs), and early strain rate (SRe) and late (SRa) diastolic strain rates. Results The AR group showed significant reduction in global systolic strain (esys) compared with the control group. Global LV longitudinal systolic SRs, diastolic SRe, and SRa were significantly reduced in the AR group in comparison with the control group. In addition, peak esys, SRs, SRe, and SRa showed negative correlation with LV mass index in AR. Conclusion Patients with AR had subclinical LV dysfunction using 2D STE-based strain and strain rate imaging. The index where volume was corrected by deformation should form the basis for predicting subclinical LV dysfunction in patients with increasing LV dilatation.

Assessment of left ventricular performance in patients with essential hypertension by global performance index based on three-dimensional speckle tracking imaging

Objective To investigate the left ventricular (LV) performance in patients with essential hypertension(EH) by global performance index (GPI) based on three-dimensional speckle tracking imaging (3D-STI).Methods A total of 164 EH patients were enrolled and divided into four subgroups according to LV configuration:LV normal group (LVN,n =67),concentric cardiac remodeling group (CCR,n =49),concentric cardiac hypertrophy group (CCH,n =28) and eccentric cardiac hypertrophy group (ECH,n =20).Thirty age and sex matched healthy volunteers were enrolled as controls.3D-STI was performed to assess LV 3D global strain and LV torsion,then LV systolic dyssynchrony index (SDI) and global performance index (GPI) were calculated.Global strain parameters were investigated among the groups,and correlations with GPI were studied.Results GPI,global longitudinal strain(GLS),global area strain(GAS),global radial strain(GRS) and global 3D strain(G3DS) in EH groups were respectively lower than those in the normal controls,and there were statistical differences among the respective parameters (P ＜0.05,respectively).SDI in group CCH and ECH were significantly higher than that in normal controls (P ＜ 0.05,respectively).In multivariate stepwise regression analysis,GAS was the most influential to GPI.Conclusions GPI based on 3D-STI may accurately reflect LV performance in patients with EH,and has potential applications in clinical practice. Key words: Echocardiography; Hypertension; Ventricular function, left; Three-dimensional speckle tracking imaging

Al-Razi Award (Second place for physicians): Assessment of left ventricular performance in patients with chronic obstructive pulmonary disease

Introduction: Chronic obstructive pulmonary disease (COPD) is currently the fourth leading cause of death in the world, and cardiovascular diseases are the most common cause of mortality in these patients. The use of pulse contour analysis for assessment of cardiac output CO in patients with COPD is a new approach not studied before in this type of patients. Aim of work: The aim of the study was to assess left ventricle (LV) performance and CO in patients with COPD by the use of pulse contour analysis, transthoracic echocardiography, and first-pass radionuclide LV imaging and correlate data obtained by them to each other. Methods: Thirty consecutive patients with COPD admitted to the intensive care unit were subjected to conservative therapy and assessment of LV functions, including CO, mean arterial pressure (MAP), stroke volume, ejection fraction, and diastolic function by the 3 methods mentioned. Results: Ten patients (33%) had MAP below normal, and 18 patients (60%) had low CO as measured by the Vigileo monitor. It was found that CO and stroke volume by Vigileo monitor and transeosaphageal echocardiography are highly correlated (P = .001); diastolic dysfunction was present in 63% of patients, whereas dilated LV with low ejection fraction was present in 43% of them. Patients with pulmonary hypertension had significantly lower MAP (P = .0001) and diastolic dysfunction (P = .035) in comparison with those without pulmonary hypertension. Patients with dilated right ventricle (RV) had significantly lower CO and MAP and also showed significantly higher systolic pulmonary artery pressure compared with those with normal RV dimensions (P = .001). Conclusions: LV systolic and diastolic dysfunctions are common in patients with COPD and both give rise to dyspnea, which is the main symptom in those patients. Low CO and low MAP are especially common in patients with COPD with high pulmonary artery pressure; both can be accurately measured by the arterial platform monitor and transthoracic echocardiography.

Validation of a Novel Method for Cardiac Output Estimation by CT Coronary Angiography

Background: Cardiac output can be estimated during retrospectively gated CT coronary angiography by anatomically determining left ventricular volumes; prospective triggering to minimize radiation precludes this methodology. We propose an alternative method for cardiac output estimation based on preclinical models suggesting that cardiac output may be inversely related to contrast washout from the aortic root during timing bolus scanning, as measured by peak aortic root contrast attenuation. Methods: 34 patients had CT coronary angiography timing bolus performed with 20 ml iodixanol at 5.5 ml/s followed by 20 ml normal saline at 5.5 ml/s through an 18-Ga antecubital catheter. Peak aortic root contrast attenuation was correlated to cardiac output calculated by echocardiography using heart rate stroke volume from biplane Simpson’s method.Results: Mean age was 58 ± 13 years; body surface area, 2.0 ± 0.5 m2. 53% were women. Stroke volume, cardiac output and cardiac index were 67 ± 19 ml, 4.5 ± 1.6 L/min, and 2.2 ± 0.7 L/min/m2, respectively. Peak aortic root contrast attenuation was 207 ± 46 HU and correlated to cardiac output and cardiac index with r = –0.64, p Conclusion: This novel method for cardiac output estimation by CTCA appears feasible. The CT physiologic parameters using the timing test-bolus data moderately correlated with echocardiographic assessment of cardiac output. The calculation of cardiac output adds important hemodynamic data to anatomic information provided by CTCA, and further development of this method may preserve assessment of left ventricular performance in prospective triggering.

Feasibility of Left Ventricular Shape Analysis from Transthoracic Real-Time 3-D Echocardiographic Images

Despite the potential ability of left ventricular (LV) shape analysis to provide independent information complementary to ventricular size and function, in clinical practice only ejection fraction (EF) is currently assessed while LV shape is not routinely quantified. Moreover, geometric assumptions in the computation of EF from multiple two-dimensional (2-D) cut-planes by disc summation or area-length methods, introduce inaccuracies in the estimates. Also, previous approaches for the quantification of LV shape were based on geometric modeling and, as a result, proved inaccurate. Our aims were (1) to develop and test a three-dimensional (3-D) technique for direct quantification of LV shape from real-time 3-D echocardiographic (RT3DE) images without the need for geometric modeling using a new class of LV shape indices; and (2) to study the relationship between these indices and ventricular size and function in normal and abnormal ventricles. Spherical (S), ellipsoidal (E) and conical (C) shape indices were calculated using custom software for analysis of transthoracic RT3DE images on both global and regional levels and initially tested on computer simulated objects of different shapes. The feasibility of using these indices to differentiate between normal and abnormal ventricles was tested in three groups of patients: normal volunteers (NL, n=9), dilated cardiomyopathy (DCM, n=9) and coronary artery disease with apical regional wall motion abnormalities (RWMA, n=9). Computer simulation demonstrated that these shape indices are size-independent and can correctly classify the simulated objects. In human ventricles, both S and C but not E correlated well with LV volumes and EF. Also, S and C changed throughout the cardiac cycle while E remained almost constant. In addition, both regional and global S and C were able to identify differences between NL and abnormal ventricles: normal ventricles were less spherical and more conical than those of patients with DCM at both end-systole and end-diastole ( p<0.05) both globally and regionally. In contrast, in patients with RWMA, similar differences were noted only at end-systole, both on a global level and in the apical region. In this study, we demonstrated the feasibility of quantifying LV shape from transthoracic RT3DE images at both global and regional levels. Potentially, such 3-D shape analysis could be combined with conventional evaluation of LV volume and function to provide a more comprehensive assessment of left ventricular performance. (E-mail: francesco.maffessanti@mail.polimi.it)

A comparative study of preload‐adjusted maximal and peak power: assessment of ventricular performance in clinical practice

This study was performed to determine whether preload-adjusted peak power can act as a surrogate for preload-adjusted maximal power in the assessment of left ventricular performance in the clinical setting. Ninety-nine consecutive patients who had undergone elective coronary artery bypass grafting were studied. Fifty-five of these patients were divided into four study groups. Afterload was changed with phenylephrine (n = 12) or glyceryl trinitrate (n = 13), preload was increased with intravenous colloid (n = 18), and contractility was increased with dobutamine (n = 12). There was excellent correlation between the two indices (r = 0.99, y = 1.0168x + 0.0769; p < 0.0001). Manipulation of neither preload nor afterload affected the indices. Both indices increased significantly during dobutamine infusion (p = 0.002). In conclusion, preload-adjusted peak power can be used as a substitute for preload-adjusted maximal power in the determination of ventricular performance in clinical practice.

Reproducibility of left ventricular volume measurements at rest and during bicycle exercise in patients with congestive heart failure: a combined radionuclide and haemodynamic study.

A series of 14 patients with heart failure due to coronary artery disease and impaired left ventricular function underwent radionuclide ventriculography with simultaneous thermodilution measurement of cardiac output by pulmonary artery catheter on two occasions (m1, m2) separated by 6 weeks in order to determine the reproducibility of haemodynamic and left ventricular volume measurements at rest and during supine bicycle exercise. The patients were in NYHA grade II or III and had baseline left ventricular ejection fractions below 40%. Derived haemodynamic variables were calculated from the thermodilution cardiac output and from the radionuclide ejection fraction as follows: stroke volume = thermodilution cardiac output/heart rate; left ventricular end-diastolic volume = stroke volume/ejection fraction; left ventricular end-systolic volume = end-diastolic volume - stroke volume. The percentage difference (PD) between each pair of data (m1, m2) was calculated using the following formula: PD = 100% x (m2-m1)/m1. The data showed that reproducible measurements of left ventricular volume can be obtained at rest and during exercise. The mean (+/- S.D.) PD values for end-systolic volume and end-diastolic volume at rest were - 0.1 +/- 17% and - 0.2 +/- 13%, respectively. The mean PD values for end-systolic volume and end-diastolic volume during exercise were - 0.3 +/- 19% and - 0.7 +/- 15%, respectively. By contrast, the reproducibility of the pulmonary capillary wedge pressure measurements was poor, as reflected by a PD value of 14 +/- 51% for exercise pulmonary capillary pressure. Combining radionuclide ventriculography and the thermodilution measurement of cardiac output is useful for measuring left ventricular volume at rest and during exercise in patients with heart failure. This minimally invasive technique allows for a comprehensive assessment of left ventricular performance and appears to be particularly suited for assessing the effects of therapeutic interventions aimed at minimizing the progressive left ventricular enlargement in heart failure.

Echocardiographic and cardiac doppler assessment of mice

Recent studies have suggested that intermediate-frequency M-Mode transthoracic echocardiographic imaging is a promising method for evaluating the left ventricle in transgenic mice. However, there is a paucity of data regarding two-dimensional (2-D) echocardiography and cardiac Doppler echocardiography in this model. Therefore we studied 15 mice (body weights 38 to 65 gm) with an ultrasound system equipped with a 9 MHz transducer. M-mode, 2-D, pulsed, and color-flow Doppler studies were performed. Mean +/- SD for septal, posterior wall, and left ventricular cavity dimensions at end diastole were the following: M-mode: 1.1 +/- 0.2, 1.0 +/- 0.2, and 3.7 +/- 0.7 mm; 2-D: 1.0 +/- 0.2, 1.1 +/- 0.3, and 3.0 +/- 0.6mm. Left ventricular fractional shortening was assessed from the M-mode echocardiogram: mean 53.7% +/- 10.7% (range 42% to 77%). 2-D assessment of left ventricular mass correlated better with left ventricular mass identified at necropsy than left ventricular mass identified by M-mode echocardiography (r = 0.70; p = 0.007 versus r = 0.07; p not significant). 2-D visualization of left ventricle, proximal aorta, and aortic and mitral valves was excellent and was obtained mainly from a "parasternal" window. Apical views were more difficult to obtain. Mean +/- SD for aortic peak and mean velocities and velocity-time integral were 0.53 +/- 0.13, 0.32 +/- 0.08, and 0.025 +/- 0.008 m/sec. Estimated stroke volume was 0.0506 +/- 0.018 ml/beat. Cardiac output was 12.64 +/- 7.87 ml/min. Mean +/- SD for mitral peak E, peak A, and E/A ratio were 0.45 +/- 0.09 m/sec, 0.19 +/- 0.06 m/sec, and 2.4 +/- 0.66 m/sec, respectively. In all mice the E/A ratio was greater than 1 (range 1.76 to 3.6). Color-flowing imaging clearly displayed normal mitral inflow and left ventricular outflow. In one mouse, aortic regurgitation was recorded by pulsed Doppler echocardiography. Echocardiographic, pulsed, and color-flow Doppler assessment of mice is feasible. In this study left ventricular mass was assessed better by 2-D measurement of left ventricular dimensions. Assessment of left ventricular performance is feasible. Color Doppler-guided evaluation of aortic flow and aortic root measurement permits assessment of stroke volume and cardiac output.

Comparison of the bruce and ramp protocols in the assessment of left ventricular performance during exercise in healthy women

Our results also show that women utilize the FrankStarling mechanism and increased contractility during upright exercise, and these compensatory mechanisms are not affected by the choice of protocol.

Assessment of left ventricular performance by on-line pressure-area relations using echocardiographic automated border detection

Objectives. The purpose of this study was to evaluate left ventricular performance by on-line pressure-area relations using echocardiographic automated border detection in the in situ canine heart in a manner similar to pressure-volume analyses.Background. Echocardiographic automated border detection can measure ventricular cavity area as an index of volume and may be interfaced with pressure to construct pressure-area loops on-line.Methods. Eight anesthetized open chest dogs had simultaneous measurement of ventricular pressure, aortic flow and midventricular short-axis area. Pressure-area loops were constructed by a computer workstation interfaced with the ultrasound system. Stroke area (Maximal area — Minimal area) and stroke force (∝P dA [P = pressure; A = area]) values during inferior vena cava (n = 8) and aortic (n = 4) occlusions were compared with stroke volume and estimates of stroke work, respectively. Inotropic modulation was induced with dobutamine infusion (2 to 5 μg/kg body weight per min), followed by propranolol infusion (2 to 5 mg). End-systolic and maximal elastance and preload recruitable stroke force (stroke force versus end-diastolic area) were derived for each period.Results. Changes in stroke area and stroke force were significantly correlated with changes in stroke volume and estimates of stroke work during caval occlusion (n = 8) (r = 0.87 ± 0.02, SEE = 8 ± 1% and r = 0.90 ± 0.03, SEE = 8 ± 2%, respectively). In dogs with aortic occlusion (n = 4), changes in stroke area significantly correlated with changes in stroke volume for pooled data (r = 0.84, SEE = 8%, y = 1.0x + 3). Ventricular performance increased with dobutamine infusion (n = 7): endsystolic elastance 30 ± 11 to 67 ± 24 mm Hg/cm2(p < 0.02 vs. control values); maximal elastance 37 ± 11 to 82 ± 26 mm Hg/cm2(p < 0.02 vs. control values); preload rcruitable stroke force 81 ± 24 to 197 ± 92 mm Hg (p < 0.02 vs. control values). Decreases occurred with propranolol infusion (n = 5) end-systolic elastance 20 ± 4 to 13 ± 4 mm Hg/cm2(p < 0.002 vs. control values); maximal elastance 29 ± 8 to 15 ± 5 mm Hg/cm2(p < 0.002 vs. control values); preload recruitable stroke force 66 ± 14 to 40 ± 9 mm Hg (p < 0.002 vs. control values).Conclusions. On-line pressure-area relations are a potentially useful means to assess left ventricular performance in a manner that is quantitatively similar to the predicted responses of pressure-volume relations.

Radionuclide assessment of left ventricular performance on exercise after external conduit operation.

Only limited information is available concerning left ventricular (LV) response to exercise after an external conduit operation for cyanotic congenital heart disease. Sixteen patients who had undergone external conduit repair (EC group) were studied with multi-gated cardiac pool imaging using a supine bicycle ergometer on 20 occasions. Six patients with a history of Kawasaki disease without coronary artery stenosis served as controls (control group). Myocardial imaging and cardiac catheterization were also performed in the EC group. There was no significant difference in left ventricular ejection fraction (LVEF) at rest between the groups. However, on exercise, LVEF of the EC group was significantly lower than that of the control group. Nine patients in the EC group showed a perfusion defect (PD) on 12 occasions. LVEF on exercise of the patients with PD was significantly lower than that of the patients without PD. Furthermore, only the patients with PD showed a LVEF decrease of 5% or more in response to exercise. In the EC group, a significant inverse relationship was demonstrated between right ventricular systolic pressure (RVP) and LVEF response to exercise. However, two out of four patients who underwent external conduit replacement improved their LVEF response to exercise with successful reduction of RVP. These findings indicate that an impaired left ventricular response to exercise was common in patients after external conduit operations. Myocardial damage and right ventricular outflow tract obstruction could be the causes of this left ventricular dysfunction.

Noninvasive computerized assessment of left ventricular performance and systemic hemodynamics by study of aortic root pressure and flow estimates in healthy men, and men with acute and healed myocardial infarction

Aortic root pressure and flow data can be used to assess left ventricular (LV) performance and properties of the systemic arterial tree. The calibrated subclavian arterial pulse trace was combined with echocardiographic imaging and Doppler velocity recordings to obtain noninvasive estimates of aortic root pressure and flow in 8 healthy subjects (group A), 12 patients with recent myocardial infarction (group B), and 8 with healed myocardial infarction and a dilated left ventricle (group C). The pressure and flow data were transferred to a computer and processed in specially designed software, including a new procedure for estimation of 3-element Windkessel model parameters. There were no significant group differences for either aortic root pressure estimates or heart rate. In groups B and C, stroke and cardiac indexes were lower and total peripheral resistance higher than in group A. There were no group differences in the model estimates of total arterial compliance, whereas the characteristic impedance was greater in group C than in A, indicating a less compliant aorta in C. Both LV total and steady power were less in groups B and C than in A, whereas no group difference was found for percent oscillatory power. The reproducibility for recording was good for the aortic root pressure estimates, and lower for the derived parameters (stroke and cardiac indexes, Windkessel model parameters and LV power), whereas that for interpretation was generally good. This method provides a unique noninvasive access to important parameters of LV function and the systemic circulation.

Cardiac function after surgery for subaortic stenosis: non-invasive assessment of left ventricular performance.

To examine left ventricular function after surgical resection of subaortic stenosis during childhood. Left ventricular performance was measured non-invasively in all patients who responded to an invitation for formal assessment. Outpatient study, tertiary referral centre. Twenty three (12 male and 11 female) patients (age range 3 to 31 years) of 43 consecutive patients with fixed subaortic stenosis undergoing surgical resection between 1975 and 1989 reattended for formal assessment 16 months to 15 years (median 4 years 4 months) after operation. Left ventricular dimension, left ventricular wall thickness, left ventricular Doppler inflow velocities, and left ventricular diastolic pressure (measured from apexcardiograms). Results were compared with those in controls individually matched for age and sex. All patients were symptom free. Left ventricular cavity dimensions were normal, as was the mean fractional shortening. Posterior wall thickness tended to be greater in the patients and there was a significant increase in septal thickness. Normalised peak rate of posterior wall thinning was significantly lower in the patients and the isovolumic relaxation time was significantly shorter. Doppler inflow velocity measurements showed that early diastolic mitral flow acceleration time was normal but deceleration time was significantly shorter in the patients. The ratio of mitral flow in early diastole (E) to E plus mitral flow in late diastole (A) was significantly higher in the patients and in two patients there was complete absence of A wave flow despite large A waves on the apexcardiogram. Systolic function was well preserved in patients after operation for subaortic stenosis. A restrictive pattern of left ventricular filling was common, however, and presumably reflected a response to the chronic pressure load and to surgery in the paediatric heart.

The echocardiographic assessment of left ventricular performance during sevoflurane and halothane anesthesia.

The cardiovascular effects of sevoflurane were studied and compared with those of halothane in 30 healthy patients. The patients were assigned to receive 1 MAC sevoflurane (n = 10), 2 MAC sevoflurane (n = 10) or 1 MAC halothane (n = 10) in N(2)O 2 l.min(-1) and O(2) 4 l.min(-1). The changes in left ventricular diastolic and systolic dimension (Dd and Ds), fractional shortening (FS), mean velocity of circumferential fiber shortening (mVcf), left ventricular diastolic and systolic volume (Vd and Vs), stroke volume (SV), ejection fraction (EF) and cardiac index (CI) were evaluated by echocardiography. Sevoflurane produced significant dose-dependent decreases in FS, mVcf, EF and SV, but no significant changes in Dd and Vd. Therefore, the decrease in SV was due mainly to the increase in left ventricular residual volume (Vs). One MAC halothane produced a more significant decrease in FS, mVcf, EF and SV, when compared to values obtained at 1 MAC sevoflourane ( P < 0.01). CI was more significantly decreased with 1 MAC halothane than with 1 MAC and 2 MAC sevoflurane ( P < 0.01). This was brought about by a slight decrease in HR with halothane and a slight increase in HR with sevoflurane, in addition to a smaller decrease in SV with sevoflurane than with halothane. This study suggests that sevoflurane may better preserve cardiac function as a pump in healthy patients, when compared to halothane.