Echocardiographic diagnosis of cardiac allograft rejection

Predictive Parameters of Decreased Left Ventricular Global Longitudinal Strain at 1 Month After Pediatric Heart Transplantation

Previous reports indicate that the decreased left ventricular global longitudinal strain (LVGLS) seen in the early postoperative period of pediatric heart transplant patients generally recovers over the course of 1-2 years. In this study, we investigate the predictive capacity of preoperative parameters on the LVGLS decline seen at 1 month post transplant. Forty-six transplant subjects with 2D echocardiographic images sufficient for speckle tracking echocardiography were enrolled. We excluded patients diagnosed with cardiac allograft vasculopathy or with an episode of rejection 1 month before or after their echocardiographic examinations. The mean LVGLS was significantly reduced at 1 month when compared to 1 year following transplant (- 15.5% vs. - 19.4%, respectively, p < 0.001). The predictors of LVGLS that decline at 1 month were the LV mass z-score [odds ratio (OR) 1.452; 95% confidence interval (CI) 1.007-2.095, p = 0.046], recipient age (OR 1.124; 95% CI 1.015-1.245, p = 0.025), and donor age (OR 1.081; 95% CI 1.028-1.136, p = 0.002) in the univariate logistic regression analyses. Although multivariate analysis yielded no significant predictors, higher LV mass z-scores showed a trend associated with the decline of LVGLS (p = 0.087). The donor/recipient weight ratio was associated with the LV mass z-score (R² = 0.412, p < 0.001).

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.

Reverse ventricular remodeling and improved ventricular compliance after heart transplantation in infants and young children

After heart transplantation (HT) in infants and young children, environmental and intrinsic factors may lead to changes in the geometry and compliance of the donor heart. Serial demographic, clinical, hemodynamic, and echocardiographic data were obtained from HT recipients younger than 4 years of age. Echocardiographic chamber measurement z-scores were compared using recipient body surface area from the time of HT to 1 week, 3 months, and last follow-up visit. Left ventricular end-diastolic volume (LVEDV) z-scores were correlated with pulmonary capillary wedge pressure (PCWP) at each time point. Heart transplantation was performed for 13 children between March 2009 and December 2012, 9 of whom (69%) were boys. The median age at HT was 8 months (range, 4-43 months), and the mean follow-up period was 13 ± 7 months. Left ventricular end-diastolic dimension z-scores decreased significantly (p = 0.03) between HT and 1 week, then increased from 1 week to 3 and 12 months. (-1.32 ± 1.7, -0.71 ± 1.8, 0.41 ± 2.1, 0.79 ± 2.3, respectively). A positive relationship (R(2) = 0.48) between the LVEDV z-score and PCPW was present at the last follow-up visit. For infants and young children, the allograft demonstrates appropriate growth by 1 year after HT. Left ventricular compliance improves over time.

Longitudinal myocardial deformation is selectively decreased after pediatric cardiac transplantation: a comparison of children 1 year after transplantation with normal subjects using velocity vector imaging

The transplanted heart experiences numerous hemodynamic changes during and after cardiac transplantation. This study sought to evaluate the left ventricular myocardial mechanics in the pediatric heart transplant population using Velocity Vector Imaging (VVI). This study retrospectively evaluated 28 heart transplant recipients by echocardiography 12 months after transplantation. Echocardiograms from 28 age- and gender-matched subjects were used as a control group. Peak global longitudinal and circumferential left ventricular strain, systolic strain rate, and diastolic strain rate were obtained. Student's t tests were used to assess differences between the two groups (defined as p ≤ 0.05). The peak global left ventricular longitudinal strain was lower in the transplant group (17.21%) than in the control group (22.14%). The transplant and control groups did not differ significantly in terms of their peak global circumferential strain (20.28% vs. 20.79%, respectively). Similar results were observed for longitudinal and circumferential systolic and diastolic strain rates. The transplant patients showed statistically significant reductions in all peak global longitudinal measures compared with those of the control subjects. Circumferential myocardial deformation appears to be preserved in transplant recipients. This could suggest evidence of ischemia given the known myocardial fiber arrangement of longitudinal fibers toward the endocardial surface, which is also more distal in the coronary arterioles.

Ventricular function in surgery for congenital heart disease

BACKGROUND The history of measuring myocardial edema by two-dimensional echocardiography and the pathophysiology of myocardial edema are reviewed. METHODS The relevance of this subject to management of children undergoing corrective surgery for single ventricle physiology and tetralogy of Fallot is reviewed. RESULTS Evidence is presented that myocardial edema is an ongoing clinical problem with relevance to management and outcomes. Methods for measuring mass increases noninvasively in the range of 10-25% with increases in myocardial water content on the order of 2-4% are now well established. CONCLUSIONS These methods and advanced animal models replicating conditions of surgery for cyanotic congenital heart disease set the stage for clinical advances in this important area.

The transplant recipient for nontransplant surgery

The transplant recipient has traded a life-threatening illness for a chronically immunosuppressed state. Subsequent anesthetic management for non-transplant surgical procedures may be challenging. The anesthesia provider must be aware of the degree of post-transplant organ dysfunction and alter anesthesia techniques accordingly. This article reviews the anesthetic concerns for patients who have undergone a variety of organ transplants.

Echo-guided endomyocardial biopsy in heart transplant recipients

After heart transplantation the effect of immunosuppression is monitored by histopathology of endomyocardial biopsy (EMB). EMB is usually carried out under X-ray guidance. Between January 1998 and March 2003, 1,262 biopsies were collected under echo-guidance in 156 patients. The biopsy access was gained through the internal jugular vein, by the standard catheterization technique. The average time of the procedure was 17 min. Four or five specimens were obtained from each patient, with a success rate of 96%. Complications involved two episodes of partial pneumothorax in one patient, atrial flutter in another and ventricular fibrillation in three patients. Conversion from echo to X-ray guidance was indicated in 11 patients. No case of significant tricuspid regurgitation related to the EMB procedure was recorded. The echo-guided endomyocardial biopsy appears to be a prospective alternative to the conventional approach under X-ray guidance. Its duration is comparable, it eliminates X-ray exposure, enables continuous echocardiographic monitoring and can be performed at the bedside.

Current status of heart transplantation in children: update 2003

Heart transplant is an effective therapy for children with end-stage heart disease. Success of this treatment depends on coordination and careful communication among the family, primary care physician, and transplant team. Primary care physicians play an essential role in the monitoring and management of the medical, nutritional, developmental, and psychosocial issues of pediatric heart transplant patients and their families (Box 3). Ongoing assessment of the child and parent's progress in adapting to transplant is crucial in order for appropriate referrals to occur. Relationships with the primary care team can improve medical outcomes for this complex group of patients and provide a framework for improved adherence to care.

Can the index of myocardial performance be used to detect acute cellular rejection after heart transplantation?

The index of myocardial performance (IMP), combining systolic and diastolic function, was measured in 50 orthotopic heart transplant recipients to determine if it could be used to detect acute rejection. It was calculated as the sum of the isovolumic contraction time (IVCT) and isovolumic relaxation time (IVRT) divided by the ejection time. Comparison of intrarecipient changes in Doppler intervals between rejection and nonrejection states demonstrated an increase in IVCT and decrease in IVRT during rejection with no significant change in the IMP. Rejection is likely to be best detected by assessing these parameters independently rather than by measuring the IMP.

The current state of, and future prospects for, cardiac transplantation in children

During the last two decades, several advances have resulted in marked improvement in medium-term survival, with excellent quality of life, in children undergoing cardiac transplantation. Improved outcomes reflect better selection of donors and recipients, increased surgical experience in transplantation for complex congenital heart disease, development of effective surveillance for rejection, and wider choice of immunosuppressive medications. Despite all of these advances, recipients continue to suffer from the adverse effects of non-specific immunosupression, including infections, induction of lymphoproliferative disorders and other malignancies, renal dysfunction, and other important end-organ toxicities. Furthermore, newer immunosuppressive regimes, thus far, appear to have had relatively little impact on the incidence of chronic rejection. Progress in our understanding of the immunologic mechanisms of rejection and graft acceptance should lead to more targeted immunosuppressive therapy and avoidance of non-specific immunosupression. The ultimate goal is to induce a state of tolerance, wherein the recipient will accept the allograft indefinitely, without the need for long-term immunusupression, and yet remain immuno-competent to all non-donor antigens. This quest is currently being realized in many animal models of solid organ transplantation, and offers great hope for the future.

Anesthetic considerations in the patient with a heart transplant

As programs to increase the awareness of organ donation grow, more patients undergo cardiac transplantation. Because immunosuppressive therapy and postoperative care are improved, the 1-year survival rate of these patients has increased to more than 80%. Not surprisingly, these patients may, either coincidentally or as a result of medications, require other procedures using anesthesia, frequently at hospitals other than the highly specialized institution that performed the transplant. Because the denervated heart responds differently than the normal heart to many perioperative drugs, physicians, including cardiologists who are frequently consulted preoperatively, must have a special awareness of the particular problems in this group of patients.

High-frequency ultrasound for quantitative characterization of myocardial edema

Myocardial edema has been associated with impaired ventricular compliance and diastolic filling. To determine the sensitivity of high-frequency (40 MHz) ultrasound to myocardial edema, we employed a model in which myocardial edema was induced by immersion of tissue in isotonic saline. The effect of freezing tissue on edema formation was also evaluated. Rat hearts were arrested at end-diastole and insonified fresh within 15 min of excision (n = 5) or following being frozen for 24 h and thawed (n = 4). Measurements of attenuation, backscatter, tissue thickness and speed of sound were performed at baseline and hourly for 4 h, and compared with direct measurements of myocardial edema. Fresh tissue demonstrated a greater propensity for the development of edema than frozen tissue. Integrated backscatter increased in both tissues, whereas the magnitude and slope of attenuation decreased as edema evolved. We conclude that high-frequency ultrasound sensitively detects myocardial edema, and we propose that the extension of these methods to clinical frequencies may prove useful for monitoring and treatment of cardiac edematous disease states.

Cardiac function of transplanted rat hearts using a working heart model assessed by magnetic resonance imaging

BACKGROUND

A direct correlation between graft rejection and cardiac contractile function in small-animal models has been difficult to establish because (i) the conventional non-working heart model is greatly different from the orthotopic heart in terms of left ventricular work and (ii) it is difficult to obtain hemodynamic data in situ. We have used magnetic resonance imaging (MRI) techniques to obtain noninvasive, in-situ quantitation of ventricular volume after heterotopic cardiac transplantation.

METHODS

Infra-renal heterotopic cardiac transplantation was performed on rats using syngeneic and allogeneic untreated donors in both working and non-working left heart models. An occluding balloon catheter in the inferior vena cava was used to vary the pre-load to the graft. An arteriovenous fistula was created to raise inferior caval oxygen saturation. Magnetic resonance imaging measurements were carried out at day 3, 4, and 5 post-transplantation. Left ventricle end-diastolic and end-systolic volumes were calculated using a biplanar ellipsoid model.

RESULTS

Stroke volume was significantly increased in the working heart model as compared to the non-working model. At day 4 post-transplant, the diastolic pressure-volume relationship in the allograft group was significantly shifted, indicative of decreased myocardial distensibility, whereas the indices of systolic function were preserved.

CONCLUSIONS

We have developed a heterotopic transplant working rat heart model and have used it to assess in-situ cardiac function by MRI. Sensitive indices of diastolic contractile function can be obtained in this rodent transplant model that correlate well with histologic evidence of early rejection.

Noninvasive markers for acute heart transplant rejection in children with the use of automatic border detection

A noninvasive method to detect heart transplant rejection would allow for increased monitoring at reduced risk. Automatic border detection is a new method to assess diastolic abnormalities. The purpose of this study was to determine whether automatic border detection of left ventricular filling detects rejection in children. Nineteen episodes of biopsy-proven rejection in 10 children were retrospectively reviewed. Echocardiograms during rejection were compared with those before rejection and during recovery. Automatic border detection indices were percentage of total left ventricular filling as a result of rapid filling, diastasis, and atrial contraction. The percentage of total ventricular filling during diastasis increased significantly during rejection (10% +/- 6% versus 15% +/- 8%, p = 0.02), and the percentage of filling during the rapid filling phase decreased during rejection (82% +/- 8% versus 77% +/- 11%, p = 0.08). These changes were even more marked for the most severe episodes of rejection. These changes resolved at recovery. Automatic border detection of left ventricular filling patterns are altered during cardiac rejection in children. Filling during diastasis increases significantly, and filling during the rapid filling phase decreases. A prospective analysis is needed to determine whether these changes in filling can obviate the need for cardiac biopsy.

Echocardiographic indexes of rejection in pediatric cardiac transplant recipients managed without maintenance steroid immunosuppression

Several noninvasive echocardiographic indexes were found to correlate with biopsy-confirmed cardiac rejection. Of these, changes in the diastolic flow profile across the mitral valve showed the best correlation.

Iatrogenic myocardial edema: increased diastolic compliance and time course of resolution in vivo

BACKGROUND

Perfusion-induced edema reduces diastolic compliance in isolated hearts, but this effect and the time for edema to resolve after blood reperfusion have not been defined in large animals.

METHODS

Edema was induced by coronary perfusion with Plegisol (750 mL, 289 mOsm/L) during a 1-minute aortic occlusion in 6 pigs. This was followed by whole blood reperfusion, inotropic support, and circulatory assistance until sinus rhythm and contractile function were restored. A control group (n = 6) was treated similarly, with 1 minute of electrically induced ventricular fibrillation and no coronary perfusion. Recorded data included electrocardiogram, left ventricular pressure and conductance, aortic flow, and two-dimensional echocardiography. Preload reduction by vena caval occlusion was used to define systolic and diastolic properties. Data were recorded at baseline and at 15-minute intervals for 90 minutes after reperfusion.

RESULTS

In the edema group, average left ventricular mass (132 +/- 7 [standard error of the mean] versus 106 +/- 4 g) and ventricular stiffness constant (0.15 +/- 0.02 versus 0.05 +/- 0.01) increased after Plegisol versus baseline (p < 0.05), returning to normal after 45 minutes of reperfusion. In controls, mass (118 +/- 6 versus 116 +/- 4 g) and ventricular stiffness (0.06 +/- 0.01 versus 0.05 +/- 0.01) did not change significantly. There was no significant change in systolic function. Myocardial water content at the end of the study was not different for the two groups.

CONCLUSIONS

Crystalloid-induced edema and diastolic stiffness resolve after 45 minutes in pigs. This suggests that edema caused solely by cardioplegia during cardiac operations should not cause significant perioperative ventricular dysfunction.

Frequency and significance of left ventricular thickening in transplanted hearts in children

The pediatric myocardium has been shown to thicken markedly during steroid administration for the treatment of pulmonary or neurologic disease. Yet, in the pediatric heart transplant patient, left ventricular (LV) thickening is sometimes used as a marker for rejection without accounting for steroid immunosuppression. The aim of this study was to determine timing and correlates of changes in LV thickness in pediatric cardiac transplant patients. In 11 patients (11 days old to 16 years old), LV thickness (mass) was first measured during the entire post-transplant course. Second, thickness was measured before and during rejection. Last, to separate the independent effects of rejection and steroids on LV mass, echocardiograms were reviewed in the immediate post-transplant period, when our protocol prescribes dramatic changes in steroid doses and rejection episodes were rare. Specifically, the donor heart underwent 5 evaluations: at donation, at peak steroid dose, 5 days after peak steroid dose, at moderate steroid dose, and at very low maintenance dose. LV mass changed most dramatically and consistently during the first 20 to 40 days after transplant. Thereafter, mass had little consistent changes and did not change significantly during any of the 52 rejection episodes. Mass increased 5 days after peak steroid dose (54 +/- 30 to 74 +/- 38 g/ht2.7, p < 0.05) and decreased during low maintenance levels of steroids. Thickening was associated with cumulative steroid dose (r = 0.66, p = 0.03) and age (r = -0.62, p = 0.04). Thus, in pediatric heart transplant patients, as in other pediatric diseases, LV thickening is associated with steroid administration. Thickening may be an unreliable marker for acute cellular rejection.

Discriminating between preservation and reperfusion injury in human cardiac allografts using heart weight and left ventricular mass

BACKGROUND

Myocardial edema caused by injury during preservation or reperfusion can affect cardiac function after heart transplantation. This study was designed to distinguish these forms of injury in human allografts.

METHODS AND RESULTS

In 15 donor hearts preserved in University of Wisconsin solution, heart weight (HW) was obtained immediately after explantation and after transport before implantation. Left ventricular mass (LVM) was calculated separately in 18 patients with the use of epicardial two-dimensional echocardiograms obtained both before explantation from the donor and after transplantation and weaning from cardiopulmonary bypass. While changes in LVM could be due to preservation or reperfusion injury, changes in HW can only be due to edema occurring during transport. HW averaged 339 +/- 24 g (mean +/- SE) before and 340 +/- 24 g after transport (P = NS); however, LVM increased 14 g, from 164 +/- 8 to 178 +/- 11 g (P < .05, paired t test). LVM increased in 10 of 18 patients (56%). No correlation was demonstrated between duration of ischemia (mean, 172 +/- 13 minutes) and changes in HW or LVM. Two patients died as a result of primary graft failure. In the first, HW increased 54 g, 2 SD above the mean. In the second, LVM increased 66 g, 2 SD above the mean, but HW changed minimally.

CONCLUSIONS

While current preservation methods result in minimal change in HW during transport, reperfusion injury frequently increases LVM. LVM determination by two-dimensional echocardiography may prove valuable in detecting allograft injury.

Effects of edema on systolic and diastolic function in vivo

Recent advances in the study of myocardial edema are reviewed. A rat model, developed for the study of diastolic properties, is differentiated from larger mammals by less myocardial water content in the control state, by less cardioplegia-induced edema, and by more rapid evolution of ischemic contracture. The model has proven useful in defining the time course of recovery from iatrogenic edema, which requires less than 15 minutes, and in defining the time course and determinants of changes in compliance during transplant rejection. In pigs, a new experimental model allows study of left ventricular (LV) mass variation and changes in systolic and diastolic properties during resolution of iatrogenic edema. Initial studies indicate that iatrogenic edema and related increases in LV stiffness resolve in less than 45 minutes in pigs, in the absence of substantial ischemic injury. No significant changes in systolic performance were demonstrable statistically, but contractility was depressed immediately after reperfusion, requiring inotropic and mechanical circulatory support. In patients, measured changes in intraoperative LV mass are small and require correction for effects of changes in LV volume to define significance.

Left ventricular mass increases during cardiac allograft vascular rejection

OBJECTIVES

This study evaluated whether left ventricular mass increases during cellular or vascular (humoral) cardiac allograft rejection.

BACKGROUND

An increase in left ventricular mass during cellular cardiac allograft rejection has been described by other investigators, although controversy has existed over the validity of these findings. Left ventricular mass changes have not been evaluated in the setting of vascular (humoral) cardiac allograft rejection.

METHODS

To determine the effect of allograft rejection on left ventricular mass, we retrospectively reviewed endomyocardial biopsy results and corresponding echocardiograms in 41 cardiac transplant recipients undergoing treatment for allograft rejection. Left ventricular mass was assessed by two-dimensional echocardiography using the method of Schiller. Maintenance immunosuppression included cyclosporine in all patients.

RESULTS

Although significant changes in left ventricular wall thickness, mass and dimensions were not observed in patients experiencing moderate or severe cellular allograft rejection (International Society for Heart and Lung Transplantation grades III and IV, n = 27), marked changes were noted in patients with vascular (humoral) rejection (n = 14). Patients with vascular rejection demonstrated an echocardiographic mean (+/- SEM) increase in left ventricular wall mass (from 109 +/- 17 to 151 +/- 17 g), and left ventricular wall thickness (from 1.3 +/- 0.1 to 1.6 +/- 0.1 cm) during the rejection episode. Additionally, vascular rejection was associated with a trend toward an increase in left ventricular systolic dimension (from 2.6 +/- 0.1 to 3.0 +/- 0.2 cm) and a decrease in left ventricular fractional shortening and increased incidence of hemodynamic compromise with rejection (50% for vascular vs. 11% for cellular rejection).

CONCLUSIONS

Left ventricular mass increases during episodes of vascular (humoral) rejection, but there is no significant change in left ventricular mass during cellular cardiac allograft rejection.

Cardiac transplantation: a review

Cardiac transplantation is currently a highly successful treatment for selected patients with end-stage cardiac failure. The long-term results are limited by the development of coronary artery vasculopathy, infection and malignancy. The activity of transplantation programmes worldwide is severely limited by the availability of donor organs. Further refinements of immunosuppressive agents are likely to result in improved prevention of both acute and chronic rejection. The donor pool is unlikely to be significantly extended as a result of measures to increase donor organ supply. Alternative methods to allograft transplantation need further investigation to increase the number of therapeutic options available for those patients with end-stage heart failure.

Management of patients after cardiac transplantation

During the past decade, the morbidity and mortality associated with cardiac transplantation have decreased dramatically. The current survival for patients who undergo orthotopic cardiac transplantation is 80 to 90% at 1 year and 70 to 80% at 5 years; these results are attributed chiefly to improved immunosuppression and the consequent decrease in infectious illnesses and rejection. Because surgical mortality and technique have not changed appreciably during the past 20 years, improved survival can be ascribed to advances in the medical management of recipients of cardiac transplants. Medical problems frequently encountered in such patients include allograft rejection, allograft vasculopathy, hypertension, renal dysfunction, hyperlipidemia, hyperglycemia, malignant disorders, general surgical disease, and osteopenic bone disease. Hence, the expertise needed for management of patients who undergo cardiac transplantation is not confined to a particular specialty--optimal care necessitates the integrated efforts of a team, including transplant physicians and personnel to provide broad subspecialty and laboratory support. Meticulous management with proactive intervention and minimal effective immunosuppression will prevent or ameliorate many problems and contribute to increased survivorship and improved quality of life. For additional substantive improvement in long-term survival and quality of life for recipients of cardiac allografts, multicenter, prospective, and placebo-controlled clinical investigations will be necessary.