Cardiac performance analysis v 3

Using either Phillips IE 33 or GE E95 machines, echocardiograms were obtained within 24 h of endomyocardial biopsy. Sedation status and anesthetic usage were matched for the baseline and rejection echocardiograms. Conventional echocardiographic measurements were collected retrospectively after being analyzed in the clinical environment using Xcelera^© (Phillips Healthcare) by non-invasive imaging pediatric cardiologists in accordance with the American Society of Echocardiography recommendations.^{7 (link),8 (link)} Circumferential and longitudinal strain were prospectively measured by a single observer from parasternal short axis at the mid-papillary level and apical 4-chamber views, respectively, using Cardiac Performance Analysis v. 3.0 (TOMTEC). Strain is reported as a negative value with a more negative value signifying better ventricular deformation. For this study’s purpose, a less negative value is described as a decrease in strain and a more negative value an increase or improvement in strain.
Hemodynamic data and coronary angiography from invasive catheterization were captured. Additionally, EKG intervals and laboratory values assessing end organ function (creatinine, liver enzymes, and brain natriuretic peptide), immunosuppression levels, DSA, and leukocyte gene expression profiling (Allomap™) were recorded when available at the time of a biopsy/echo pair.

Echocardiograms were analyzed if they occurred within 1 month of catheterization. Echocardiograms were obtained using a Philips iE33 system (Andover, MA, USA) then stored in DICOM format at a frame rate of 30 fps on the clinical server. These studies were retrieved to perform two-dimensional speckle tracking echocardiography offline using vendor independent software (Tomtec Cardiac Performance Analysis v3.0). Six segments from the apical four-chamber view were averaged to measure global longitudinal strain, strain rate, and early diastolic strain rate (EDSR). Six segments from the parasternal short-axis view at the mid-ventricular level were averaged to obtain global circumferential strain, strain rate, and EDSR. Radial strain was not used in this analysis due to its high measurement variability.^{14 (link)} If the myocardium was not visualized well, the specific segments were excluded. Strain measures were excluded if more than two cardiac segments were excluded from the analysis due to poor tracking. Examples of speckle tracking analysis in a single left ventricle and single right ventricle are shown in Figures 1 and 2, respectively. A single blinded reviewer (DS) made all measurements. Intra-and inter-observer variabilities were assessed for longitudinal and circumferential measures of myocardial deformation on 10 echocardiograms.