Jie J Cao

Left Ventricular Filling Pressure Assessment Using Left Atrial Transit Time by Cardiac Magnetic Resonance Imaging

Background—Left atrial (LA) size and function reflect left ventricular (LV) hemodynamics. In the present study, we developed a novel method to determine LA circulation transit time (LATT) by MRI and demonstrated its close association with LV filling pressure. Methods and Results—All subjects were prospectively recruited and underwent contrast-enhanced MR dynamic imaging. Mean LATT was determined as the time for contrast to transit through the LA during the first pass. In an invasive study group undergoing clinically indicated cardiac catheterization (n=25), LATT normalized by R-R interval (nLATT) was closely associated with LV early diastolic pressure (r=0.850, P=0.001), LV end-diastolic pressure (r=0.910, P<0.001), and mean diastolic pressure (r=0.912, P<0.001). In a larger noninvasive group (n=56), nLATT was prolonged in patients with LV systolic dysfunction (n=47) (10.1±3.0 versus 6.6±0.7 cardiac cycles in normal control subjects, n=9; P<0.001). Using a linear regression equation derived from the invasive group, noninvasive subjects were divided into 3 subgroups by estimated LV end-diastolic pressure: ⩽10 mm Hg, 11 to 14 mm Hg, and ≥15 mm Hg. There were graded increases from low to high LV end-diastolic pressure subgroups in echocardiographic mitral medial E/e′ ratio: 9±5, 11±4, and 13±3 (P=0.023); in B-type natriuretic peptide (interquartile range): 44 (60) pg/mL, 87 (359) pg/mL, and 371 (926) pg/mL (P=0.002); and in N-terminal pro–B-type natriuretic peptide: 57 (163) pg/mL, 208 (990) pg/mL, and 931 (1726) pg/mL (P=0.002), demonstrating the ability of nLATT to assess hemodynamic status. Conclusions—nLATT by cardiac MR is a promising new parameter of LV filling pressure that may provide graded noninvasive hemodynamic assessment.

Effects of Hemodynamics on Global and Regional Lung Perfusion A Quantitative Lung Perfusion Study by Magnetic Resonance Imaging

Background—Cardiac hemodynamics affect pulmonary vascular pressure and flow, but little is known of the effects of hemodynamics on lung perfusion at the tissue level. We sought to investigate the relationship between hemodynamic abnormalities in patients with left heart failure and global and regional lung perfusion using lung perfusion quantification by magnetic resonance imaging. Methods and Results—Lung perfusion was quantified in 10 normal subjects and 28 patients undergoing clinically indicated left and right heart catheterization and same day research cardiac magnetic resonance imaging. A total of 228 lung slices were evaluated. Global lung perfusion, determined as the average of 6 coronal lung slices through the anterior, mid, and posterior left and right lungs, was significantly lower in patients with reduced cardiac index (<2.5 L/min per m2): 94±30 mL/100 mL per minute versus 132±40 mL/100 mL per minute in those with preserved cardiac index (≥2.5 L/min per m2; P=0.003). The gravitational anterior to posterior perfusion gradient was inversely associated with left ventricular end-diastolic pressure (r=−0.728; P<0.001), resulting in a blunted perfusion gradient in patients with elevated left ventricular end-diastolic pressure, a finding largely attributed to the perfusion reduction in posterior lung regions. In a multivariate regression analysis adjusting for all hemodynamic variables, altered lung perfusion gradient was most closely associated with increased mean pulmonary arterial pressure (P=0.016). Conclusions—Increased left ventricular filling pressure and the resultant increase in pulmonary arterial pressure are associated with disruption of the normal gravitational lung perfusion gradient. Our findings underscore the complexity of heart-lung interaction in determining pulmonary hemodynamics in left heart failure.Background— Cardiac hemodynamics affect pulmonary vascular pressure and flow, but little is known of the effects of hemodynamics on lung perfusion at the tissue level. We sought to investigate the relationship between hemodynamic abnormalities in patients with left heart failure and global and regional lung perfusion using lung perfusion quantification by magnetic resonance imaging. Methods and Results— Lung perfusion was quantified in 10 normal subjects and 28 patients undergoing clinically indicated left and right heart catheterization and same day research cardiac magnetic resonance imaging. A total of 228 lung slices were evaluated. Global lung perfusion, determined as the average of 6 coronal lung slices through the anterior, mid, and posterior left and right lungs, was significantly lower in patients with reduced cardiac index (<2.5 L/min per m2): 94±30 mL/100 mL per minute versus 132±40 mL/100 mL per minute in those with preserved cardiac index (≥2.5 L/min per m2; P =0.003). The gravitational anterior to posterior perfusion gradient was inversely associated with left ventricular end-diastolic pressure ( r =−0.728; P <0.001), resulting in a blunted perfusion gradient in patients with elevated left ventricular end-diastolic pressure, a finding largely attributed to the perfusion reduction in posterior lung regions. In a multivariate regression analysis adjusting for all hemodynamic variables, altered lung perfusion gradient was most closely associated with increased mean pulmonary arterial pressure ( P =0.016). Conclusions— Increased left ventricular filling pressure and the resultant increase in pulmonary arterial pressure are associated with disruption of the normal gravitational lung perfusion gradient. Our findings underscore the complexity of heart-lung interaction in determining pulmonary hemodynamics in left heart failure.

Quantifying passive myocardial stiffness and wall stress in heart failure patients using personalized ventricular mechanics

Background Heart failure (HF) patients present with a spectrum of phenotypes, including preserved ejection fraction (HFpEF) and reduced EF (HFrEF). The underlying mechanisms of HFpEF and HFrEF may be related to mechanical factors such as stiffness and stress. This study aimed to quantify passive mechanical properties in HFrEF and HFpEF patients using personalised left ventricular (LV) biomechanical analysis.

Left atrial volume measurement with magnetic resonance imaging: a comparison of biplane, short axis and long axis methods

Left atrial (LA) dilation is an important index in cardiovascular disease. The CMR volumetric short axis method is the reference imaging standard but has limited ability to define the mitral valve plane accurately. The biplane method is simpler and frequently employed in clinical settings. We hypothesized that long axis two chamber (2ch) imaging might better define left atrial boundaries.

MRI feature tracking strain profiles distinguish patients with left ventricular systolic and diastolic dysfunction with and without clinical heart failure

Background Characterizing myocardial mechanical properties is valuable in understanding cardiomyopathy with and without clinical heart failure (HF). We sought to examine the incremental value of strain assessment in patients with left ventricular systolic dysfunction without HF (LVSD), HF with reduced ejection fraction (HFrEF), LV diastolic dysfunction without HF (LVDD) and HF with preserved EF (HFpEF) during routine cardiac MR (CMR) evaluation.

Relationship of prolonged global and regional central circulatory transit time with hemodynamics

Methods Forty nine subjects undergoing clinically indicated right and left heart cardiac catheterization were prospectively recruited to undergo MRI in a 1.5T scanner. First pass perfusion using steady state free precession saturation recovery sequence was performed with gadolinium infusion at 0.01 mmol/kg. Global TT was defined as the time between the peaks of time intensity curves between the right atrium and the ascending aorta. Segmental TT included TT between right atrium to pulmonary artery (right heart TT), pulmonary artery to left atrium (pulmonary TT), or left atrium to ascending aorta (left heart TT). All TTs were normalized to heart rate. Multivariate regression analysis was performed to delineate the relationship of hemodynamic parameters measured during cardiac catheterization to TT. Receiver operating characteristic (ROC) analyses were performed to assess ability of global and segmental TT to predict elevated LVEDP.

Afterload excess and myocardial performance.

Background Systolic circumferential and longitudinal strain(CSt%, LSt %) are widely used to assess myocardial performance, but their afterload dependence has not been well characterized. Using geometric estimates of left ventricular (LV) circumferential and meridional wall stress(CWS, MWS) as indices of afterload at the myocardial level, we compared LV CSt and LSt to estimates of CWS and MWS in normals (NL, n= 39, 46% female, age 54.6+/-14.6 yrs) and patients with dilated cardiomyopathy (DCM, n= 35, 23% female, age 50.8+/-15.0 yrs, EF 27.2+/-10.8%). Methods

1076 Effects of age and gender on right ventricular structure and function: a turning point at age fifty

Methods We studied 218 (99 male, 119 female) normotensive, non-obese (BMI < 28), non-diabetic volunteers aged 20– 90 (mean 54 ± 15) with normal 2-D echocardiograms on a 1.5 T Siemens Sonata scanner. TrueFISP cine imaging was used to obtain contiguous 8 mm short axis slices of the entire RV at end-expiration. Volumetric analysis was performed using Medis MASS. RV volume at end-diastole and end-systole and RV mass were determined and indexed to body surface area (EDVi, ESVi, RVMi) including papillary muscles in the cavity volume.

Association of reduced right ventricular global and regional wall motion with abnormal right heart hemodynamics

Background The relationship of right ventricular (RV) regional and global systolic function to right heart hemodynamics is not well understood. In this study we used MRI feature tracking to assess regional RV wall motion, cine MR to evaluate global RV function and examined the relationship of regional wall motion and global RV function to right heart hemodynamics. Methods Fifty patients undergoing clinically indicated right heart catheterization were prospectively recruited to a research CMR within 5 hours of catheterization. Majority of the heart failure cases were due to left heart failure. SSFP cine images were acquired to evaluate RV regional and global function. RV longitudinal and long axis radial strains were derived from the 4-chamber cine, and mid wall septal circumferential and radial strains from the short-axis plane in mid ventricle using CIM feature tracking software (Auckland, NZ). Right heart hemodynamics was assessed during catheterization. Results Mean age was 64±13 years, mean RV ejection fraction (EF) 51±13%. Reduced longitudinal and radial displacement in 4 chamber view was significantly associated with reduced RVEF, r=-0.621 (p<0.001) and r=0.346 (p=0.014), respectively. Similarly, in short axis plane reduced septal circumferential and radial strain were also significantly correlated with RVEF, r=-0.488 (p=0.001) and r=0.527 (p<0.001) respectively. In regression analysis reduced RVEF had strongest association with increased pulmonary wedge pressure (r=-0.622, p<0.001) in univariate analysis and in multivariate analysis (p<0.001) after adjusting for all the right heart hemodynamic parameters. Pulmonary wedge pressure contributed to 41% of RVEF variation in this cohort with predominant left heart failure. While also significantly correlated with pulmonary wedge pressure, regional wall motion including longitudinal strain, septal circumferential and radial strain had strongest association with mean pulmonary arterial pressure, r=0.577 (p<0.001), r=0.440 (p=0.002) and r=-0.451 (p=0.001), respectively. Conclusions It is feasible to use MR feature tracking to characterize RV regional wall motion. Reduced global and regional RV systolic functions are associated with right heart hemodynamic abnormalities. In patients with predominant left heart failure, pulmonary wedge pressure contributes importantly to RVEF variation. Funding None.

Comparisons of myocardial strain and strain rate in patients with heart failure with preserved and reduced ejection fraction using Feature Tracking of cine MR images

Methods All participants were prospectively recruited and underwent CMR in a 1.5 T scanner. LVEF 400 pg/ml. Patients with myocardial infarction were excluded. Myocardial circumferential strain (CST) and strain rate (CSR) was analyzed in mid LV of the short axis plane and the longitudinal strain (LST) and strain rate (LSR) in 4-chamber view of the SSFP cine images using feature tracking (CIM software, Auckland, New Zealand). LV end diastolic pressure (LVEDP) was estimated using normalized left atrial transition time from time-intensity curves of the first pass perfusion images.