Novel echocardiographic strategies for rejection diagnosis

The Role of Echocardiography in the Management of Heart Transplant Recipients

Transthoracic echocardiography is the primary non-invasive modality for the investigation of heart transplant recipients. It is a versatile tool that provides comprehensive information on cardiac structure and function. Echocardiography is also helpful in diagnosing primary graft dysfunction and evaluating the effectiveness of therapeutic approaches for this condition. In acute rejection, echocardiography is useful with suspected cellular or antibody-mediated rejection, with findings confirmed and quantified by endomyocardial biopsy. For identifying chronic rejection, ultrasound has a more significant role and, in some specific patients (e.g., patients with renal failure), it may offer a role comparable to coronary angiography to identify cardiac allograft vasculopathy. This review highlights the usefulness of echocardiography in evaluating normal graft function and its role in the management of heart transplant recipients.

Worsening in Longitudinal Strain and Strain Rate Anticipates Development of Pediatric Transplant Coronary Artery Vasculopathy as Soon as One Year Following Transplant

Transplant coronary artery vasculopathy (TCAV) following orthotopic heart transplantation (OHT) continues to be the primary reason for late graft failure in children. The current gold standard of diagnosis of TCAV is coronary angiography with or without intravascular ultrasound. This study investigates the longitudinal use of speckle-tracking echocardiographic strain imaging as an early non-invasive marker to screen for development of TCAV. Echocardiograms from patients who underwent OHT between 2006 and 2010 at Children's Hospital Colorado (n = 50) were retrospectively assessed. Studies were evaluated at baseline (within a month of transplant), then at each annual clinical follow-up for peak longitudinal (LS) and circumferential (CS) strain, systolic strain rate, and diastolic strain rate using Siemens Velocity Vector Imaging software. Comparisons were made between subjects who did and did not develop TCAV. Mean time to TCAV diagnosis following OHT was 3.2 years (range 1-5.1 years). One year after transplant, significant differences were seen between groups in LS (non-TCAV mean -19.6%, TCAV mean -17.3%, p = 0.03) and longitudinal strain rate (non-TCAV mean -1.7%/s, TCAV mean -1.4%/s, p = 0.04). These differences persisted in subsequent years. Differences in LS preceded the catheterization-based diagnosis of TCAV in pediatric heart recipients and were noted as early as one year post transplant. Additionally, within-subject LS changes may have utility as a non-invasive screening tool to predict those patients at increased risk for development of TCAV.

Increasing Levels of Positive End-expiratory Pressure Improve the Left Ventricular Strain

PURPOSE

The goal of this study was to evaluate possible changes in the left myocardial performance of patients with cardiogenic shock (CS) during ascending levels of positive end-expiratory pressure (PEEP) using speckle-tracking echocardiography.

MATERIALS AND METHODS

This was an interventional clinical study performed on CS patients under mechanical ventilation. These patients underwent echocardiography after 15 to 30 minutes of progressive increases in PEEP zero end-expiratory pressure (ZEEP) (PEEP 5, PEEP 10, PEEP 15 cm H2O). We evaluated the changes caused by these increasing levels of PEEP on the E/E' ratio and the parameters of left ventricular systolic and diastolic functions, including longitudinal strain (S) and strain rate (SR). Analyses of mean values were carried out using analysis of variance.

RESULTS

A total of 65 CS patients were included. Their mean age was 68.58±14.61 years. Progressive increases in PEEP induced a significant decrease in the E/E' ratio (ZEEP=12.87±1.81; PEEP=5, 8.39±3.61; PEEP=10, 6.34±1.73; and PEEP=15, 7.10±0.37; P<0.0001). Although we did not find significant changes in left ventricular ejection fraction, a clear increase in left ventricular S and SR occurred (ZEEP=-13, 15±1.27; PEEP=5, -16.97±4.01; PEEP=10, -16.89±0.46; PEEP=15, -15.39±4.21; and ZEEP=-1.02±0.02; PEEP=5, -1.49±0.13; PEEP=10, -1.57±0.21; PEEP=15, -1.24±0.29, respectively; all values were significant).

CONCLUSIONS

Increasing levels of PEEP improve the left ventricular S and SR. PEEP levels could modify the performance of left ventricular fibers.

Alteration of Cardiac Deformation in Acute Rejection in Pediatric Heart Transplant Recipients

The objective of this study is to assess changes in cardiac deformation during acute cellular- and antibody-mediated rejection in pediatric HT recipients. Pediatric HT recipients aged ≤18 years with at least one episode of biopsy-diagnosed rejection from 2006 to 2013 were included. Left ventricular systolic S (SS) and SR (SSr) data were acquired using 2D speckle tracking on echocardiograms obtained within 12 h of right ventricular endomyocardial biopsy. A mixed effect model was used to compare cardiac deformation during CR (Grade ≥ 1R), AMR (pAMR ≥ 2), and mixed rejection (CR and AMR positive) versus no rejection (Grade 0R and pAMR 0 or 1). A total of 20 subjects (10 males, 50%) with 71 rejection events (CR 35, 49%; AMR 21, 30% and mixed 15, 21%) met inclusion criteria. The median time from HT to first biopsy used for analysis was 5 months (IQR 0.25-192 months). Average LV longitudinal SS and SSr were reduced significantly during rejection (SS: -17.2 ± 3.4% vs. -10.7 ± 4.5%, p < 0.001 and SSr: -1.2 ± 0.2 s^- 1 vs. -0.9 ± 0.3 s^- 1; p < 0.001) and in all rejection types. Average LV short-axis radial SS was reduced only in CR compared to no rejection (p = 0.04), while average LV circumferential SS and SSr were reduced significantly in AMR compared to CR (SS: 18.9 ± 4.2% vs. 20.8 ± 8.8%, p = 0.03 and SSr: 1.35 ± 0.8 s^- 1 vs. 1.54 ± 0.9 s^- 1; p = 0.03). In pediatric HT recipients, LV longitudinal SS and SSr were reduced in all rejection types, while LV radial SS was reduced only in CR. LV circumferential SS and SSr further differentiated between CR and AMR with a significant reduction seen in AMR as compared to CR. This novel finding suggests mechanistic differences between AMR- and CR-induced myocardial injury which may be useful in non-invasively predicting the type of rejection in pediatric HT recipients.

Decline in ventricular function as a result of general anesthesia in pediatric heart transplant recipients

Echocardiography is frequently performed under anesthesia during procedures such as cardiac catheterization with EMB in pediatric HTx recipients. Anesthetic agents may depress ventricular function, resulting in concern for rejection. The aim of this study was to compare ventricular function as measured by echocardiography before and during GA in 17 pediatric HTx recipients. Nearly all markers of ventricular systolic function were significantly decreased under GA, including EF (-4.2% ±1.2, P < .01) and RV FAC (-0.05 ± 0.02, P = .04). Subjects in the first post-transplant year (n = 9) trended toward a more significant decrease in EF vs those beyond the first post-transplant year (n = 8; -6.0% ±1.2 vs -2.1 ± 2.0, P = .1). This information quantifies a decline in biventricular function that should be expected in pediatric HTx recipients while under GA and can assist the transplant clinician in avoiding unnecessary treatment of transient GA-induced ventricular dysfunction.