Dobutamine stress echocardiography for assessing coronary artery disease after transplantation in children

Multimodality Imaging to Detect Rejection, and Cardiac Allograft Vasculopathy in Pediatric Heart Transplant Recipients—An Illustrative Review

The three most common modalities of graft surveillance in pediatric heart transplant (HT) recipients include echocardiography, coronary angiography, and endomyocardial biopsy (EMB). The survival outcomes after HT in children have improved considerably in recent years. However, allograft rejection and cardiac allograft vasculopathy remain the leading cause of death or re-transplantation. The routine surveillance by EMB and coronary angiography are invasive and risky. Newer noninvasive echocardiographic techniques, including tissue Doppler imaging (TDI), 2-D speckle tracking echocardiography, CT coronary angiography (CTCA), cardiovascular magnetic resonance (CMR), single-photon emission computed tomography (SPECT), and positron emission tomography (PET) and invasive techniques such as intravascular ultrasound (IVUS), functional flow reserve (CFR) of coronary arteries, optical coherence tomography (OCT), have emerged as powerful tools which may help early recognition of sub-clinical rejection, response to treatment, early detection, and progression of CAV. The multimodality imaging approach, including noninvasive and invasive tests, is the future for the transplanted heart to detect dysfunction, rejections, and early CAV. This review illustrates noninvasive and invasive imaging techniques currently used or could be considered for clinical use in detecting heart transplant rejection, dysfunction, and CAV in children.

Prognostic Value of Exercise Stress Echocardiography in Pediatric Cardiac Transplant Recipients

BACKGROUND

Cardiac allograft vasculopathy (CAV) is a leading cause of long-term morbidity and mortality in pediatric heart transplant (HTx) recipients. Exercise stress echocardiography (ESE) has been shown to be useful in the detection of angiographically-confirmed CAD in children. However, the prognostic utility of ESE for prediction of cardiac events in HTx survivors is unknown.

STUDY AIM AND HYPOTHESIS

Therefore, we aim to assess if an abnormal (positive) ESE will be associated with a higher risk of future cardiovascular (CV) outcomes in pediatric HTx recipients.

MATERIAL AND METHODS

We conducted a retrospective review of CV outcomes of a cohort of 95 pediatric HTx recipients who underwent 188 ESE over a 10-year period. A composite endpoint for CV events including myocardial infarction, hospitalization for non-rejection heart failure, coronary revascularization, need for repeat transplantation, and death was used. Based on the interpretation of the ESE results, each ESE study was classified for this study as either positive (abnormal), or negative (normal) for ischemia. Results of the coronary angiograms performed near the time of ESE were also assessed and classified for this study as positive (abnormal) or negative (normal) for CAV according to standard HTx criteria for CAV.

RESULTS

51 (27%) ESE were positive for ischemia. There was a total of 35 CV events in 23 patients. A positive ESE was associated with increased risk of any CV event [Hazard ratio [HR] 3.55, 95% CI 1.52, 8.28, and also an increased risk of CV death (HR 3.19, 95% CI 1.23, 8.28) Freedom from composite CV outcome at 1, 2, and 3 years following a positive ESE was 89.9% (CI = 77.3%, 95.7%), 81.5% (CI = 65.9%, 90.5%), and 63.2% (CI = 41.9%, 78.5%), respectively. Freedom from composite cardiovascular outcome at 1, 2, and 3 years following a negative ESE was 99.3% (94.8, 99.9), 98.4% (93.6, 99.6), and 97.0% (90.6, 99.1) respectively. No patient died within 1 year of a negative ESE.

CONCLUSIONS

In this largest study of ESE in pediatric HTx recipients, a positive or abnormal ESE is associated with increased future cardiovascular morbidity and mortality. Conversely, a negative ESE can help predict CV event-free survival. Even in the setting of a normal ANG, our pilot data show that an abnormal ESE may be still clinically important. Use of ESE in follow-up may improve risk stratification and management of pediatric HTx recipients.

Cardiac allograft vasculopathy: A review

BACKGROUND

Heart transplantation has become the standard of care for pediatric patients with end-stage heart disease, and outcomes have consistently improved over the last few decades. CAV, however, remains a leading cause of morbidity and mortality in heart transplantation and is the leading cause of death beyond 3 years post-transplantation. We sought out to provide an in-depth overview of CAV in the pediatric heart transplant population.

METHODS

Database searches were conducted in both Medline and Embase on the topic of cardiac vasculopathy in pediatric heart transplant recipients. The search used five broad concept terms: heart transplant; pediatric; CAV; diagnosis, prognosis, and risk factors; and guidelines and reviews. References were captured if there was at least one term in each of the concepts. The search was limited to articles in the English language.

RESULTS

A total of 148 articles were identified via the literature search with further articles identified via review of references. Pediatric data regarding the etiology and development of CAV remain limited although knowledge about the immune and non-immune factors playing a role are increasing. CAV continues to be difficult to detect with many invasive and non-invasive methods available, yet their effectiveness in the detection of CAV remains suboptimal. There remains no proven medical intervention to treat or reverse established CAV disease, and CAV is associated with high rates of graft loss once detected. However, several medications are used in hopes of preventing, slowing progression, or modifying the outcomes.

CONCLUSION

This review provides a comprehensive overview of CAV, discusses its clinical presentation, risk factors, diagnostic tools used to identify CAV in the pediatric population, and highlights the current therapeutic options and the need for ongoing research.

Abnormalities of the Coronary Arteries in Children: Looking beyond the Origins

Coronary arterial abnormalities are uncommon findings in children that have profound clinical implications. Although anomalies of the coronary origins are well described, there are many other disease processes that affect the coronary arteries. Immune system-mediated diseases (eg, Kawasaki disease, polyarteritis nodosa, and other vasculiditides) can result in coronary arterial aneurysms, strictures, and abnormal tapering of the vessels. Because findings at imaging are an important component of diagnosis in these diseases, the radiologist's understanding of them is essential. Congenital anomalies may present at varying ages, and findings in hemodynamically significant anomalies, such as fistulas, are key for both diagnosis and preoperative planning. Pediatric heart surgery can result in wide-ranging postoperative imaging appearances of the coronary arteries and also predisposes patients to a multitude of complications affecting the heart and coronary arteries. In addition, although rare, accidental trauma can lead to injury of the coronary arteries, and awareness and detection of these conditions are important for diagnosis in the acute setting. Patients with coronary arterial conditions at presentation may range from being asymptomatic to having findings of myocardial infarction. Recognition of the imaging findings is essential to direct appropriate treatment. ^©RSNA, 2017.

Global Deformation Parameters Response to Exercise in Adolescents with Repaired Tetralogy of Fallot

Exercise stress echocardiography is rarely used in the follow-up of children with congenital heart disease following surgical repair. There are no data on global longitudinal strain (GLS) and global circumferential strain (GCS) during exercise in adolescents with repaired tetralogy of Fallot (TOF). The purpose of this prospective study was to investigate GLS and GCS using speckle tracking two-dimensional echocardiography (2D-STE) at rest and during exercise in adolescents with repaired TOF. Twenty patients with repaired TOF and 20 controls were included. The subjects exercised on a semi-supine cycle ergometer using a two-staged 3-min step protocol of 20-40 W at 60-75 rpm. Exercise images with 2D-STE measurements were available for all 40 subjects. In the study group, the GLS values changed significantly between the baseline and third and sixth minute of exercise (-18.10 ± 2.20, -16.23 ± 4.47, -14.22 ± 2.63, respectively, p < 001). GCS did not vary significantly from baseline to end of the exercise testing (-17.49 ± 5.14, -17.15 ± 9.20, -15.66 ± 3.59, respectively, p > 0.05). There was a statistically significant difference between the Stage I longitudinal strain values of the study and control groups (-14.26 ± 9.13 and -20.22 ± 2.88, respectively, p = 0.02) but no significant difference between the Stage II values of these groups (-14.22 ± 2.63 and -15.11 ± 2.45, respectively, p > 0.05). The results revealed significant changes in GLS during exercise in patients with repaired TOF. Data gathered from deformation analysis of 2D-STE during exercise testing can enhance the ability to detect subtle ventricular dysfunction in the follow-up of children with repaired TOF.

Semi-supine exercise stress echocardiography in children and adolescents: feasibility and safety

Although exercise stress echocardiography (ESE) is a well-validated technique in adult population, its use in children is quite limited. We aimed to assess the feasibility, the safety and the reproducibility of ESE, using on-line scanning in semi-supine cyclo-ergometer protocol in a large pediatric population. Between July 2008 and January 2013, 42 patients (mean age 14 ± 3) were evaluated with a bicycle ESE performing 50 studies. ESE was successfully performed and well tolerated by all patients. None of the patients presented with adverse effects of stress-induced ischemia. HR was 82 ± 13 at rest, and 153 ± 19.1 during peak exercise. Among 544 views analyzed for grading of image quality, the visualization was optimal in 473 (87 %), suboptimal in 39, and inadequate in 32 (6 %). 37 tests were performed in patients with congenital or acquired coronary abnormality. Regional wall motion abnormalities (RWMA) were revealed in nine cases (24 %). The agreement between the two different observers showed a K index of 0.7276 (95 % CI 0.6497-0.8055) for the image quality and a K index of 0.5125 (95 % CI 0.4782-0.5468) for the RWMA analysis. Among ten patients with hypertrophic cardiomyopathy, we were able to demonstrate the new comparison of significant left ventricular outflow tract gradient (≥30 mmHg) during exercise in three patients (30 %). Bicycle stress echocardiography performed by on-line scanning during exercise is a feasible, safe, and reproducible modality in children. Further data to assess its diagnostic accuracy are, however, needed. Stress echocardiography provides a dynamic assessment of the myocardial structure and function under conditions of physiologic or pharmacologic stress.

Detection and grading of coronary allograft vasculopathy in children with contrast-enhanced magnetic resonance imaging of the coronary vessel wall

BACKGROUND

Coronary allograft vasculopathy is the leading cause of late death after heart transplantation in children. It is poorly detected by conventional angiography. Intravascular ultrasound is invasive and costly. This study shows that magnetic resonance imaging (MRI) late gadolinium enhancement (LGE) of the coronary vessel wall can detect and grade coronary allograft vasculopathy.

METHODS AND RESULTS

Twenty-four children (10 male; age range, 9-17 years) underwent coronary angiography, intravascular ultrasound, and MRI. Maximal intimal thickness and mean intimal index were recorded. MRI included coronary magnetic resonance angiogram and LGE vessel wall imaging with 1.5 T (n=12) and 3.0 T (n=12). Ten healthy control subjects also underwent LGE MRI. Mean time posttransplantation was 5.5 years (range, 0.25-14 years). Seven patients had Stanford grade IV coronary allograft vasculopathy on intravascular ultrasound, 3 of whom had angiographic disease. Maximal intimal thickness and mean intimal index were 0.73±0.50 mm and 20.9±10.6%, respectively. On MRI, mean diameter of enhancement of vessel wall was 6.57±4.91 mm, and mean enhancement index (indexed to vessel lumen size) was 1.10±1.72. The control group showed little or no LGE. Correlation of LGE with maximal intimal thickness using the Pearson coefficient was 0.80 (P<0.001) and with mean intimal index was 0.92 (P<0.001). An MRI diameter >7.5 mm gave 86% sensitivity and 93% specificity.

CONCLUSIONS

LGE scores correlate well with traditional intravascular ultrasound measures. These promising early results encourage larger-scale clinical studies to investigate whether LGE MRI will allow closer follow-up and better prevention of coronary allograft vasculopathy in children.

Utility of exercise stress echocardiography in pediatric cardiac transplant recipients: a single-center experience

BACKGROUND

Annual coronary angiography (ANG) to assess for significant epicardial coronary artery disease (CAD) is an integral part of follow-up care for pediatric cardiac transplant recipients at Children's Hospital Boston. Exercise stress echocardiography (ESE) is an important, non-invasive tool for the detection of ischemia in adults but has been rarely used in children. Therefore, the aim of this study was to assess the feasibility and utility of ESE in excluding ANG-detected epicardial CAD at our center, where ESE has been implemented since 2007.

METHODS

We conducted a retrospective review of all pediatric cardiac transplant recipients at our institution who had undergone ESE and ANG between January 2007 and December 2010, and with testing performed < 12 months apart. ESE results were compared against ANG.

RESULTS

The study cohort comprised 47 cardiac transplant recipients. One patient's ESE images were inadequate for interpretation. Of the remaining 46 patients, ESE had a sensitivity of 88.9% (95% confidence limits [CL], 51.8%, 99.7%), a specificity of 91.9% (95% CL, 71.8%, 98.3%), and a negative predictive value of 97% (95% CL, 85.1%, 99.1%) for the ANG-detected CAD.

CONCLUSIONS

This large, single-center study showed ESE was feasible and had a high specificity and excellent negative predictive value in excluding epicardial CAD in pediatric cardiac transplant recipients. Future prospective, large-scale studies are needed to confirm these findings and help identify a subset of children for whom a negative ESE could decrease the frequency of routine ANG.

International Society for Heart and Lung Transplantation working formulation of a standardized nomenclature for cardiac allograft vasculopathy-2010

The development of cardiac allograft vasculopathy remains the Achilles heel of cardiac transplantation. Unfortunately, the definitions of cardiac allograft vasculopathy are diverse, and there are no uniform international standards for the nomenclature of this entity. This consensus document, commissioned by the International Society of Heart and Lung Transplantation Board, is based on best evidence and clinical consensus derived from critical analysis of available information pertaining to angiography, intravascular ultrasound imaging, microvascular function, cardiac allograft histology, circulating immune markers, non-invasive imaging tests, and gene-based and protein-based biomarkers. This document represents a working formulation for an international nomenclature of cardiac allograft vasculopathy, similar to the development of the system for adjudication of cardiac allograft rejection by histology.

Evaluation of the myocardial performance index and tissue doppler imaging by comparison to near-simultaneous catheter measurements in pediatric cardiac transplant patients

BACKGROUND

Parameters derived from Doppler echocardiography, such as the myocardial performance index (MPI) and the ratio of peak velocity of early diastolic prograde flow (E) across the atrioventricular valve (AVV) divided by the peak velocity of early diastolic tissue motion at the AVV annulus (E') (E:E' ratio), are routinely used to assess ventricular function. However, they have not been compared with measurements obtained by cardiac catheterization (CC) in children.

METHODS

We prospectively studied post-cardiac transplant children undergoing CC with near-simultaneous echocardiographic imaging for MPI and E:E'. CC data included right atrial pressure (RAp), pulmonary artery wedge pressure (PAWp) and cardiac index (CI). One investigator, who was blinded to the CC data, measured right ventricular (RV) and left ventricular (LV) MPI and E:E' offline. Correlations between echocardiographic and catheter measurements were calculated. Receiver-operating-characteristics (ROC) curves were created to evaluate the utility of echocardiographic measurements that exhibited statistically significant correlations with CC measurements.

RESULTS

Twenty-four patients (age range 0.8 to 21 years) underwent 142 CCs during the study period. Of the 12 correlations studied, 3 met statistical significance (p < 0.05) (RV E:E' vs RAp, RV E:E' vs PAWp and LV MPI vs CI). The ROC areas for these correlations were 0.38, 0.42 and 0.68, respectively. There were no cut-off points where both the sensitivity and specificity for any measurement were >0.80.

CONCLUSIONS

Our data suggest that MPI and E:E' are poor predictors of simultaneously obtained, catheter-derived hemodynamic parameters in post-transplant children. These limitations should be carefully considered before ascribing diagnostic value to these measurements.

Stress imaging in congenital cardiac disease

In patients with coronary arterial disease, stress imaging is able to demonstrate abnormalities in the motion of the ventricular walls, and abnormalities in coronary arterial perfusion not apparent at rest. It can also provide information on prognostic factors. In patients with congenitally malformed hearts, stress imaging is used to determine contractile reserve, abnormalities of mural motion, and global systolic function, but also to assess diastolic and vascular function. In most of these patients, stress is usually induced using pharmacological agents, mainly dobutamine given in varying doses. The clinical usefulness of abnormal responses to the stress induced in such patients has to be addressed in follow-up studies. The abnormal stress might serve as surrogate endpoints, predicting primary endpoints at an early stage, which are useful for stratification of risk in this population of growing patients. We review here the stress imaging studies performed to date in patients with congenitally malformed hearts, with a special emphasis on echocardiography and cardiac magnetic resonance imaging.

A prospective study of dobutamine stress echocardiography for the assessment of cardiac allograft vasculopathy in pediatric heart transplant recipients

Transplant CAV is the leading cause of graft loss beyond one yr post-heart transplant. Diagnosis can be challenging and the previous "gold standard," coronary ANG, tends to underestimate disease. The purpose of this study was to relate DSE to ANG for the diagnosis of CAV. Prospective annual DSE at a single centre on all heart transplant patients (1999-2006) were compared with results from routine coronary angiograms. Progression of CAV over time as determined by DSE and ANG and associated factors were sought through logistic regression models adjusted for repeated measures. There were 102 heart transplant patients (54 males) transplanted between 1989 and 2006. Median age at transplant was 17 months (0-16.6 yr). The initial DSE was at a median of 10-months post-transplantation. There was a high correlation between an abnormal DSE and an abnormality on ANG (p = 0.002). There was an increased probability of an abnormal DSE with increasing grade of CAV as assessed by ANG (p < 0.001). Factors associated with an abnormal DSE included older age at transplant (p = 0.04), higher grade of rejection (p = 0.002), higher total cholesterol (p = 0.04), higher LDL (p < 0.05), and older age at the time of DSE (p = 0.002). DSE result was not related to HDL, triglyceride or homocysteine levels, or to steroid or statin use. The probability of an abnormal DSE result increases with increasing angiographic grade of CAV, and thus DSE may be used for initial screening for CAV with ANG reserved for confirmation and grading. Patients transplanted at an older age and those with a greater history of rejection were at higher risk of a positive DSE and may require increased surveillance for CAV.

Cardiovascular risk reduction in high-risk pediatric patients: a scientific statement from the American Heart Association Expert Panel on Population and Prevention Science; the Councils on Cardiovascular Disease in the Young, Epidemiology and Prevention, Nutrition, Physical Activity and Metabolism, High Blood Pressure Research, Cardiovascular Nursing, and the Kidney in Heart Disease; and the Interdisciplinary Working Group on Quality of Care and Outcomes Research

Although for most children the process of atherosclerosis is subclinical, dramatically accelerated atherosclerosis occurs in some pediatric disease states, with clinical coronary events occurring in childhood and very early adult life. As with most scientific statements about children and the future risk for cardiovascular disease, there are no randomized trials documenting the effects of risk reduction on hard clinical outcomes. A growing body of literature, however, identifies the importance of premature cardiovascular disease in the course of certain pediatric diagnoses and addresses the response to risk factor reduction. For this scientific statement, a panel of experts reviewed what is known about very premature cardiovascular disease in 8 high-risk pediatric diagnoses and, from the science base, developed practical recommendations for management of cardiovascular risk.

Cardiovascular Risk Reduction in High-Risk Pediatric Patients

Although for most children the process of atherosclerosis is subclinical, dramatically accelerated atherosclerosis occurs in some pediatric disease states, with clinical coronary events occurring in childhood and very early adult life. As with most scientific statements about children and the future risk for cardiovascular disease, there are no randomized trials documenting the effects of risk reduction on hard clinical outcomes. A growing body of literature, however, identifies the importance of premature cardiovascular disease in the course of certain pediatric diagnoses and addresses the response to risk factor reduction. For this scientific statement, a panel of experts reviewed what is known about very premature cardiovascular disease in 8 high-risk pediatric diagnoses and, from the science base, developed practical recommendations for management of cardiovascular risk.

Location and variability of epicardiac ganglia in human fetuses

The aim of the study was to determine the morphology of epicardiac ganglia in human fetuses at different stages of their development as these ganglia are considered to be of a pivotal clinical importance. Twenty-one fetal hearts were investigated applying a technique of histochemistry for acetylcholinesterase to visualize the epicardiac neural ganglionated plexus with its subsequent stereoscopic examination on total organs. In all of the examined fetuses, epicardiac neural plexus with numerous ganglia was well recognizable and could be clearly differentiated into seven ganglionated subplexuses, topography and structural organization of which were typical for hearts of adult human. The largest ganglion number comprising 77% of all counted ganglia was identified on the dorsal atrial surface. Fetal epicardiac plexus in gestation period of 15-40 weeks contained 929 +/- 62 ganglia, but ganglion amount did vary substantially from heart to heart. In conclusion, this study implies that the human fetal epicardiac ganglia occupy their definitive location already at gestation period from 15 weeks and their number as well as distribution on heart surface presumably is not age dependent.

The impact and outcome of transplant coronary artery disease in a pediatric population: a 9-year multi-institutional study

BACKGROUND

Transplant coronary artery disease (TCAD) limits survival in heart transplant recipients; however, its incidence in children is unknown. The purpose of this study was to determine the angiographic incidence of TCAD, potential risk factors, and outcomes in a large pediatric cohort.

METHODS

From January 1993 to December 1, a total of 1,222 children, aged newborn to 17 years, underwent primary cardiac transplantation at 20 institutions. A total of 2,049 coronary angiograms were performed in 751 patients. All angiograms were graded for coronary disease and results were submitted to the Pediatric Heart Transplant Study database. We analyzed time-related freedom from graded severity and events from coronary disease, and we examined risk factors.

RESULTS

The incidence of angiographic abnormalities at 1, 3, and 5 years was 2%, 9%, and 17%, respectively; however, moderate-to-severe disease occurred in only 6% at 5 years, compared with 15% in the adult transplant database (p <0.0001). The major risk factors were older recipient and donor age. Two or more episodes of rejection in the 1st year correlated with coronary disease (p = 0.05). Overall freedom from graft loss caused by primary TCAD was 99%, 96%, and 91% at 1, 5, and 9 years after heart transplantation, respectively. Death or graft loss occurred within 2 years of diagnosis in patients with severe disease; 24% of patients with any coronary disease died within 2 years.

CONCLUSIONS

The incidence of TCAD in children is smaller than the incidence in adults, but increases with age. Graft loss is infrequent in children; however, severe coronary disease correlates with poor prognosis.

Exercise assessment in infants after cardiac transplantation

BACKGROUND

Few data describe exercise performance after cardiac transplantation during infancy. The aim of this study was to compare the cardiorespiratory response to exercise in healthy subjects with that of subjects who had undergone heart transplantation during infancy to treat hypoplastic left heart syndrome.

METHODS

Subjects (24 heart transplant recipients and 25 healthy controls) exercised on a treadmill using pediatric ramp protocols. We measured heart rate (HR), blood pressure, and metabolic data. Median age at transplantation was 20 days (range, 4 to 97 days). Age of recipients at exercise testing was 9.7 +/- 2.3 years and in healthy subjects was 10.5 +/- 1.4 years (p=not significant [NS]).

RESULTS

Exercise duration was similar in both groups (10.3 +/- 2.0 minutes in recipients vs 11.1 +/- 1.5 minutes in healthy subjects, (p=NS). Heart rate at rest was greater in recipients (94 +/- 15 beats per minute [bpm] vs 85 +/- 11 bpm, p=0.02). Peak HR also was less in the recipient group (158 +/- 15 bpm vs 189 +/- 12 bpm, p <0.001). Peak oxygen consumption was 14% less in the recipients (32.3 +/- 5.6 ml/kg/min vs 36.8 +/- 5.5 ml/kg/min, p <0.01). Ventilatory anaerobic threshold was decreased in recipients, 27.6 +/- 9.6 vs 32.8 +/- 6.0, p <0.05. Respiratory exchange ratio at peak exercise was equal in both groups (1.06 +/- 0.06 vs 1.06 +/- 0.08). Oxygen pulse index did not differ significantly, 5.5 +/- 1.1 ml/beat/m2 in recipients and 6.1 +/- 1.7 ml/beat/m2 in healthy subjects (p=NS).

CONCLUSIONS

Overall, children who undergo cardiac transplantation in infancy have exercise capacities within the normal range. These recipients have a decreased heart rate reserve that may account for the differences in peak oxygen consumption when compared with healthy subjects.

Echocardiographic evaluation before and after cardiac transplantation

Transplantation of the heart remains a viable option not only as primary treatment for hypoplastic left heart syndrome, but also for end-stage problems after the Norwood sequence of palliations. In this review, I discuss the pre-operative, intra-operative, and post-operative echocardiographic evaluation of these patients, with special emphasis on hemodynamic and functional assessment as well as surveillance for rejection and coronary arterial disease.

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.

Non-invasive detection of coronary artery disease by dobutamine-stress echocardiography in children after heart transplantation

BACKGROUND

Coronary vasculopathy is the main cause of cardiac graft failure. Because yearly coronary angiography is invasive in children, a non-invasive method for detecting graft vasculopathy is needed. The aim of this study was to test dobutamine-stress echocardiography in a pediatric population to determine its feasibility, safety and reliability in the detection of graft coronary artery disease.

METHODS

Eighteen patients, aged 2 days to 16.8 years at transplantation (mean 8.4 years), underwent 44 dobutamine-stress echocardiography (DSE) exams, at a follow-up of 1.1 to 11.8 years (mean 5.1 years). Selective coronary angiography was performed for comparison. Echocardiographic recordings were obtained in 4 standard views of the left ventricle and measurements carried out within the frames of a 16-segment model. Segmental scores of contractility were obtained for each segment and a total segmental contractility index was calculated at each stage.

RESULTS

All patients reached the maximum dose stage. Maximum heart rate was 57% to 90% of predicted maximum. Maximum systolic blood pressure reached 190 mmHg. Segmental scores were normal in 37 and abnormal in 7 cases. Echographic results were concordant with angiography in 82% and discordant in 18% of the cases (4 negative DSEs with minor angiographic lesions, 2 positive DSEs with normal angiography), but there was no significant angiographic lesion with normal DSE.

CONCLUSIONS

DSE is a safe and highly feasible non-invasive technique in transplanted children. A normal DSE study successfully predicts the absence of significant coronary artery disease in the post-transplant population.

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.

Anesthesia for Noncardiac Surgery in Pediatric Patients Following Cardiac Transplantation

Pediatric cardiac transplantation has been performed with increasing frequency to treat hypoplastic left heart syn drome and other types of congenital heart disease. A large number of these patients will require anesthesia posttrans plantation for noncardiac surgery. A review of our series of 92 anesthetics in 46 patients has better defined periopera tive risk factors, anesthetic management, common surgical procedures, and complications associated with noncardiac surgery in posttransplantation patients. Anesthetic manage ment concerns include allograft coronary artery disease, graft rejection, denervation, cardiac dysrhythmias, immuno suppression, cyclosporine-induced hypertension, drug inter actions, renal dysfunction, and intravenous access prob lems. Preoperative evaluation must include the possibility and definition of these problems. Medically stable patients undergoing noncardiac/nonthoracic surgery after cardiac transplantation undergo the same surgical procedures as similarly aged nontransplantation patients. Similar induc tion techniques can be used as in nontransplantation pa tients. These patients may also be scheduled for same-day surgery if other significant medical problems are not present and the difficulty of the surgery is compatible with an out patient setting. Patients with more complex medical prob lems, including chronic rejection, significant coronary artery disease, or a history of congestive failure may need over night monitoring in a hospital setting despite that only a minor surgical procedure is being performed.

Overview of stress echocardiography: uses, advantages, and limitations

Responses of the heart to changes in our environment are probably even more important than how the heart functions at rest. Accordingly, stress testing with noninvasive imaging has become important for diagnosis, prognosis, and monitoring the effects of therapy. Echocardiography at rest and with stress permits characterization of global and segmental left ventricular function as well as valvular structure and function. Moreover, echocardiography can be performed during or after a number of different physical or even mental stressors. Advantages of stress echocardiography include its ready availability, relatively low capital cost, and incremental value in that it allows characterization of cardiac anatomy as well as the myocardial response to a potentially ischemic stimulus. Moreover, echocardiography has the potential to image myocardial perfusion along with wall motion and wall thickening. Substantial literature has now been accumulated on the value of stress echocardiography for the diagnosis of ischemic disease, preoperative risk assessment, and assessment of myocardial viability. Echocardiography has compared generally well with nuclear imaging techniques for the detection of angiographic coronary artery disease. Overall sensitivity, however, has been slightly less, particularly for the detection of single-vessel coronary disease, although specificity has been on average somewhat higher than nuclear cardiology techniques. Because of the potential for variability in study acquisition as well as interpretation, careful safeguards need to be employed. Specifically, meticulous technique needs to be applied to obtain high-quality images and to assure that those images are obtained promptly after treadmill exercise stress. Only readers with specific interest and expertise should interpret stress echocardiography studies. Continuing efforts need to be made to assess and minimize variability and to assure continuing quality improvement. Advances in instrumentation, including evolving technology for real-time 3-dimensional imaging, and echocardiography contrast assessment of myocardial perfusion will likely improve the sensitivity of echocardiography and further extend its usefulness.

Late rejection is a predictor of transplant coronary artery disease in children

OBJECTIVE

The study objectives were to determine posttransplant coronary artery disease (TxCAD) incidence, predisposing factors and optimal timing for retransplantation (re-Tx) in pediatric heart transplantation (Tx) recipients.

BACKGROUND

The TxCAD limits long-term survival following heart Tx, with re-Tx being the primary therapy. Information on risk factors and timing of listing for re-Tx is limited in children.

METHODS

The records of children who survived >1 year post-Tx at Loma Linda University were reviewed. Nonimmune and immune risk factors were analyzed.

RESULTS

TxCAD was documented in 24 of 210 children. Freedom from TxCAD was 92 +/- 2% and 75 +/- 5% at 5 and 10 years' post-Tx, respectively. The TxCAD diagnosis was established at autopsy in 10 asymptomatic patients who died suddenly within nine months following the most recent negative angiograms. The remaining 14 children had angiographic diagnoses of TxCAD and had symptoms and/or graft dysfunction (n = 10) or positive stress studies (n = 4). Three of 14 died within three months after the diagnosis was made. Eleven patients underwent re-Tx within seven months of diagnosis; nine survived. Univariate and multivariate analyses showed that only late rejection (>1 year posttransplant) frequency (p = 0.025) and severity (hemodynamically compromising) (p < 0.01) were independent predictors of TxCAD development. Freedom from TxCAD after severe late rejection was 78 +/- 8% one year postevent and 55 +/- 10% by two years.

CONCLUSIONS

Late rejection is an independent predictor of TxCAD. Patients suffering severe late rejection develop angiographically apparent TxCAD rapidly and must be monitored aggressively. Both TxCAD mortality and morbidity occur early; therefore, we recommend immediate listing for re-Tx upon diagnosis.

Evaluation of regional wall motion and quantitative measures of ventricular function during dobutamine stress echocardiography in pediatric cardiac transplantation patients

BACKGROUND

Graft coronary disease is a leading cause of death in patients who have undergone cardiac transplantation. The purpose of this study was to evaluate regional wall motion response and quantitative measures of ventricular function during dobutamine stress echocardiography (DSE) in pediatric transplantation patients.

METHODS

Eleven patients were evaluated the first year after transplantation (10/11 no rejection). Ten of the 11 were reevaluated 1.2 +/- 0.3 years later (9/10 no rejection).

RESULTS

Dobutamine stress echocardiography revealed the following: (1) baseline regional wall motion abnormalities in 80% that resolved in all, (2) increased heart rate and blood pressure, (3) no change in left ventricular end-diastolic diameter, (4) decreased end-systolic diameter, (5) decreased wall stress and increased velocity of circumferential fiber shortening, (6) increased VCFcZ score (representing systolic left ventricular function), and (7) a decreased mitral passive-to-active filling ratio. Patients with rejection had abnormal VCFcZ scores at rest.

CONCLUSIONS

Pediatric transplantation patients without rejection have baseline regional wall motion abnormalities. With DSE, the following are present: (1) resolution of wall motion abnormalities, (2) increased contractility independent of load, and (3) changes in diastolic parameters that reflect increased heart rate. Patients with rejection may have abnormal contractility at rest.

The role of stress echocardiography in children

Exercise and pharmacological stress echocardiography are well-accepted techniques of evaluating coronary artery disease in adults. In children, however, experience with stress echocardiography is limited and continues to evolve. The objective of this focused review was to describe the experience with exercise and dobutamine stress echocardiography in the pediatric population, with an emphasis on technique, current indications, and future directions. Experience is reported in children with prior Kawasaki disease or heart transplant recipients, as well as patients with congenital coronary abnormalities. In addition, stress echocardiography has been used in patients who have undergone coronary artery bypass graft surgery to evaluate short- and long-term graft patterning. Stress echocardiography appears to be a feasible, safe, and useful modality for the noninvasive assessment of flow-limiting stenosis in the pediatric population and can be used serially in the routine follow-up and risk stratification in children at risk for coronary events.

Noninvasive imaging in congenital heart disease

Imaging algorithms in congenital heart disease, as in the patient with acquired heart diseases continue to evolve, with more and more information gleaned noninvasively. The emphasis will be on the newer aspects of imaging, not cross sectional echocardiography with color Doppler.

Transplant coronary artery disease in children

Transplant coronary artery disease is an accelerated vasculopathy that occurs in adult and pediatric heart transplant recipients, and it is a leading cause of death among late survivors. This form of coronary disease, also known as graft coronary disease, differs from classical atherosclerosis in both histologic and angiographic features and it progresses much more rapidly. Although its pathogenesis has not been determined precisely, both immune and non-immune mechanisms appear to contribute, with a final common pathway of endothelial injury due to both antigen-dependent and antigen-independent factors. Many investigators believe both cellular and/or humoral rejection play a direct role in its etiology. In children the true incidence of the condition is unknown, although a multicenter survey identified 58 (7.2%) patients among 815 transplant recipients at 17 centers. Detection remains difficult. In the past, non-invasive methods have been unsatisfactory, although recent experience has suggested that Dobutamine stress echocardiography may be promising. Once a diagnosis is made, treatment has been limited to palliation by either intracoronary interventional procedures or surgical coronary bypass grafting, and to cardiac retransplantation with its own set of problems. Current efforts are directed at prevention. Blood levels of cholesterol have been reduced in adults treated with Pravastatin, but there have been no reports of its use in children. In adults additional agents with potential benefit have included calcium channel blockers and ACE inhibitors. A multicenter trial in children is needed to answer the many remaining questions regarding transplant coronary disease in this age group.

Transplant coronary artery disease in pediatric heart transplant recipients

BACKGROUND

Transplant coronary artery disease (TxCAD) contributes to a large percentage of late morbidity and mortality among adult heart transplant recipients. Intracoronary ultrasound (ICUS) is a sensitive tool in the diagnosis of TxCAD in adult patients and has allowed analysis of factors contributing to disease development. Experience with ICUS in pediatrics, however, has been limited. By using ICUS we sought to determine the overall prevalence of TxCAD in pediatrics and to characterize factors associated with its development in this population.

METHODS

Eighty-six studies were performed in 51 pediatric patients a median of 3.4 years after heart transplantation. Evaluation included angiography and ICUS in 83 and angiography alone in 3 studies. Donor and recipient characteristics were obtained. The ICUS images were analyzed for intimal thickening and compared with coronary angiograms. The presence of any intimal thickening on ICUS was considered TxCAD. An intimal index and point of maximal intimal thickening (MIT) were measured. Vessel disease was graded 0 to 4 based on these results. Four patients had evidence of vasculopathy by angiography, whereas 32 patients (63%) had evidence of intimal proliferation by ICUS. Grade 2 or greater disease was present in 19 (37%) patients. A positive correlation was found when comparing time from transplant with intimal index and MIT (p < 0.001). No other factors were found to predict the development of disease. The overall prevalence of disease was 74% in patients studied at least 5 years after transplant. Intracoronary ultrasound can be performed safely in pediatric patients. Transplant coronary artery disease is common in infants and children after heart transplantation, although its prevalence appears to be less than in adult recipients at similar time intervals. We found no factor other than time from transplant was associated with development of disease.

Coronary artery to pulmonary artery collaterals after heart transplantation

Collaterals are described between coronary and pulmonary arteries after orthotopic heart transplantation. It is likely the collaterals developed as a result of adhesions in the pericardial space. This is a previously unrecognized complication of heart transplantation with potential clinical implications, as coronary to extracardiac artery collaterals have been shown to cause myocardial ischemia.