Catherine L. Dent

Rejection is reduced in thoracic organ recipients when transplanted in the first year of life

BACKGROUND Infant heart transplant recipients have been reported to have decreased rates of rejection when clinical criteria are used for diagnosis. This study compares the rates of acute episodes of rejection in heart and lung transplant recipients transplanted in the first year of life to those of older recipients utilizing pathologic criteria. METHODS Records of 100 consecutive lung transplant recipients (cystic fibrosis patients excluded) and 107 consecutive heart transplant recipients were reviewed with respect to: time to first rejection; total number; single versus multiple; and early (<90 days) versus late (>180 days) biopsy-proven rejection episodes. Rejection was defined as ISHLT biopsy Grade 3A or A2 for heart and lung transplant recipients, respectively. Biopsy and immunosuppression protocols were similar between groups. RESULTS Kaplan-Meier analysis for freedom from rejection showed infant heart recipients were more often rejection-free (p = 0.004) as were infant lung recipients (p = 0.0001). Multivariate analysis revealed age at transplant as the most significant factor in predicting time to first rejection (age <1 year: risk ratio 0.19 [0.068-0.54] for lung transplant recipients and risk ratio 0.46 [0.27-0.78] for heart transplant recipients). Early rejection episodes occurred with less frequency in both the infant heart (19 of 63 [30%] versus 24 of 44 [50%]; p = 0.016) and lung (3 of 26 [12%] versus 63 of 74 [85%]; p = 0.001) groups. Late episodes of rejection were also less frequent in infant heart (4 of 53 [8%] versus 10 of 36 [28%], p = 0.016) and lung (0 of 23 [0%] versus 29 of 65 [45%]; p = 0.001) recipients. Multiple (> or =2) rejection episodes occurred less in infant heart (4 of 63 [6%] versus 9 of 41 [22%]; p = 0.037) and lung recipients (0 of 26 [0%] versus 17 of 74 [23%]; p = 0.003). CONCLUSIONS These results demonstrate that age of <1 at time of thoracic transplantation confers significant protection from early, late and multiple episodes of acute rejection, as well as significantly greater freedom from rejection and time to first rejection.

Patterns and Potential Value of Cardiac Troponin I Elevations After Pediatric Cardiac Operations

BACKGROUND Perioperative myocardial injury is a major determinant of postoperative cardiac dysfunction for congenital heart disease, but its assessment during this period is difficult. The objective of this study was to determine the suitability of using postoperative serum concentrations of cardiac troponin I (cTnI) for this purpose. METHODS Cardiac troponin I levels were measured serially in the serum of patients undergoing uncomplicated repairs of atrial septal defect (n = 23), ventricular septal defect (n = 16) or tetralogy of Fallot (n = 16). The concentrations were correlated with intraoperative parameters (cardiopulmonary bypass time, aortic cross-clamp time, and cardiac bypass temperature), and postoperative parameters (magnitude of inotropic support, duration of intubation, and postoperative intensive care and hospital stay). RESULTS Postoperative absolute cTnI levels were lesion specific, with a pattern of increase and decrease similar for each lesion. For the total cohort, significant correlations between postoperative cTnI levels at all times (r = 0.43 to 0.83, p < 0.05) until 72 hours were noted for all parameters, except for cardiac bypass temperature. When evaluated as individual procedure groups, no significant relationships were noted in the atrial septal defect group, whereas postoperative cTnI levels were more strongly correlated with all intraoperative and postoperative parameters in the ventricular septal defect group than in the tetralogy of Fallot group. CONCLUSIONS This study suggests that cTnI values immediately after operation reflect the extent of myocardial damage from both incisional injury and intraoperative factors. Cardiac tropinin I levels in the first hours after operation for congenital heart disease are a potentially useful prognostic indicator for difficulty of recovery.

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.

High-frequency ultrasound detection of the temporal evolution of protein cross linking in myocardial tissue

The progressive increase in stiffening of the myocardium associated with the aging process and abetted by comorbid conditions such as diabetes may be linked to an excessive number of collagen cross links within the myocardial extra-cellular matrix. To determine whether ultrasound can delineate changes in the physical properties of heart tissue undergoing cross linking, the authors employed a model in which increased cross linking was induced by treating rat myocardial tissue with specific chemical fixatives. Rat hearts (n=5 each group) were arrested at end-diastole, insonified (30 to 50 MHz) fresh within a few minutes of excision in a phosphate buffered solution, placed in a fixative (10% formalin or 2.5% glutaraldehyde) and insonified at 30-minute intervals thereafter for 24 hours. Ultrasonic attenuation increased in tissues cross linked with formalin (maximal change: 27.2/spl plusmn/3.4 dB/cm) and glutaraldehyde (maximal change: 40.2/spl plusmn/5.6 dB/cm) over a 24-hour period. The frequency dependence of the attenuation coefficient increased as a function of the extent of collagen cross links in formalin (maximal change: 0.8/spl plusmn/0.3 dB/cm-MHz) and glutaraldehyde (maximal change: 0.9/spl plusmn/0.6 dB/cm-MHz). This study represents the first time that the precise time course of myocardial protein cross linking in situ has been characterized by using real time monitoring, and the physiologic effect has been delineated on microscopic material properties.

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.

Long-term therapy for pulmonary hypertension in children.

This review recounts recent advances in the understanding and treatment of the processes that cause pulmonary hypertension in infancy and childhood. New discoveries have begun to unveil connections between the basic physiological mechanisms responsible for the regulation of pulmonary vascular tone and the abnormal responses of the pulmonary vasculature in a variety of disease conditions. These discoveries raise hope for new therapeutic interventions that may improve the high mortality and morbidity of both children and adults with pulmonary vascular disease. In the meantime, treatment efforts continue to be focused on the relief of pulmonary vasoconstriction with inhaled nitric oxide and intravenous prostacyclin in the short term and oral calcium channel blockers as the mainstay of long-term therapy. Lung transplantation often remains as the only viable option for continued survival when the pulmonary vascular disease is progressive.

Monitoring of myocardial edema with quantitative ultrasonic parametric imaging

Myocardial edema is associated with impaired ventricular compliance and diastolic dysfunction. To determine the sensitivity of high-frequency ultrasound to myocardial edema, we employed a model in which edema was induced by immersion of heart tissue in isotonic saline. Formation of edema after rapid-freezing and thawing of myocardium was also evaluated. Rat hearts were arrested at end-diastole and insonified fresh within 15 minutes of excision (n=5) or after being frozen for 24 hours and thawed (n=4). A high-frequency, acoustic microscope was employed to perform ultrasonic measurements of attenuation, backscatter, speed of sound, and tissue thickness at baseline and hourly for 4 hours while immersed in solution. Parametric images of these ultrasonic indices were constructed to monitor changes in microscopic material properties due to edema and to allow identification of localized regions of interest. Fresh tissue demonstrated a greater propensity for the development of edema than frozen tissue. Integrated backscatter increased in both tissues while the magnitude and slope of attenuation decreased as edema evolved. We conclude that high-frequency ultrasound sensitively detects myocardial edema and may prove useful for monitoring and treatment of cardiac edematous disease states.

Long-term therapy for pulmonary hypertension in children

This review recounts recent advances in the understanding and treatment of the processes that cause pulmonary hypertension in infancy and childhood. New discoveries have begun to unveil connections between the basic physiological mechanisms responsible for the regulation of pulmonary vascular tone and the abnormal responses of the pulmonary vasculature in a variety of disease conditions. These discoveries raise hope for new therapeutic interventions that may improve the high mortality and morbidity of both children and adults with pulmonary vascular disease. In the meantime, treatment efforts continue to be focused on the relief of pulmonary vasoconstriction with inhaled nitric oxide and intravenous prostacyclin in the short term and oral calcium channel blockers as the mainstay of long-term therapy. Lung transplantation often remains as the only viable option for continued survival when the pulmonary vascular disease is progressive.