Bacteria Endocarditis Caused by Mycoplasma hyorhinis in a Juvenile, Immunosuppressed Pig (Sus scrofa domesticus) following Partial Heart Transplantation.

Domestic swine (Sus scrofa domesticus) are important translational models for cardiovascular transplant studies. This can be attributed to the anatomic and physiologic similarities of their cardiovascular system to humans. Transplant studies frequently employ clinically relevant immunosuppression regimens to prevent organ rejection postoperatively. Immunosuppression can lead to opportunistic infection, including presentations that are novel or poorly described in immunocompetent hosts. In this study, we describe the first case of Mycoplasma hyorhinis-induced endocarditis affecting the pulmonary valve in a juvenile, immunosuppressed pig following a partial heart transplantation procedure. Clinical signs of infection began at 15 d postoperation, were consistent with a variety of infectious agents, including Mycoplasma hyorhinis, and included lethargy, respiratory signs, and elevated white blood cell counts. By 28 d post procedure, lameness and soft tissue swelling around the left tarsus developed. Joint fluid obtained by arthrocentesis was PCR positive for Mycoplasma hyorhinis and negative for other tested pathogens. Despite antimicrobial treatment, the transplanted pulmonary valve developed leaflet thickening, stenosis, and insufficiency starting at 30 d after the procedure. At 86 d posttransplantation, the pig reached experimental endpoints and was humanely euthanized for necropsy and histopathology. The pulmonary valve had numerous dark red vegetative expansions of all 3 leaflets. Postmortem testing of a vegetative lesion was positive for Mycoplasma hyorhinis, confirming the etiologic agent responsible for endocarditis. Mycoplasma hyorhinis-induced endocarditis of an orthotopic transplanted pulmonary valve has yet to be described in swine. This case report demonstrates that infections following immunosuppression may present with novel or undercharacterized clinical signs.

Surgical Protocol for Partial Heart Transplantation in Growing Piglets.

Partial heart transplantation is a new approach to deliver growing heart valve implants. Partial heart transplants differ from heart transplants because only the part of the heart containing the necessary heart valve is transplanted. This allows partial heart transplants to grow, similar to the valves in heart transplants. However, the transplant biology of partial heart transplantation remains unexplored. This is a critical barrier to progress of the field. Without knowledge about the specific transplant biology of partial heart transplantation, children with partial heart transplants are empirically treated like children with heart transplants because the valves in heart transplants are known to grow. In order to progress the field, an animal model for partial heart transplantation is necessary. Here, we contribute our surgical protocol for partial heart transplantation in growing piglets. All aspects of partial heart transplantation, including the donor procedure, the recipient procedure, and recipient perioperative care are described in detail. There are important nuances in the conduct of virtually all aspects of open heart surgery that differs in piglets from humans. Our surgical protocol, which is based on our experience with 34 piglets, will allow other investigators to leverage our experience to seek fundamental knowledge about the nature of partial heart transplants. This is significant because the partial heart transplant model in piglets is complex and very resource intensive.

Semilunar valve growth and function 10 years after infant heart transplantation: Predicting long-term outcomes of partial heart transplants.

INTRODUCTION: Partial heart transplants are a new type of pediatric transplant that replace defective heart valves with the parts of matched donor hearts containing the necessary valves. Short-term outcomes of partial heart transplants are excellent, but long-term outcomes are unknown. In order to predict the long-term outcomes of partial heart transplants, we evaluated long-term growth and function of semilunar heart valves transplanted in infancy as part of a heart transplant. METHODS: All children who underwent infant heart transplantation at a single center from 1997 to 2014 were included in this study. Children in whom echocardiograms after heart transplantation and after 10 years were not available for review were excluded. The echocardiograms were reviewed by two authors to analyze semilunar valve annulus diameters, Z-scores, peak valve gradients, and valve regurgitation. Statistical difference was determined using two-tailed, paired sample t-tests with Bonferroni correction for multiple comparisons. RESULTS: Data from 15 patients were analyzed. The aortic valve annulus averaged 1.3 cm (range 0.7-1.8 cm) immediately after transplantation and grew to an average of 1.7 cm (range 1.4-2.3 cm) after 10 years (p < .001). After 10 years, the aortic valve peak gradient avereraged 5.1 mmHg (range 2.1-15.5 mmHg) and none of the valves had more than trivial regurgitation. The pulmonary valve annulus averaged 1.5 cm (range 1.1-2.5 cm) immediately after transplantation and grew to an average of 2.1 cm (range 1.0-2.9 cm) after 10 years (p < .001). After 10 years, the pulmonary valve peak gradient averaged 4.3 mmHg (range 1.1-13.8 mmHg), and 7% of valves had moderate regurgitation. DISCUSSION: Semilunar heart valves transplanted in infancy as part of a heart transplant demonstrate statistically significant growth and excellent function after 10 years. This predicts excellent long-term outcomes of partial heart transplants.

Pre-operative Imaging of Critical Coarctation of the Aorta: Impact on Surgical Approach and Outcomes.

Computed tomographic angiography (CTA) has been increasingly used for the evaluation of infants with aortic arch hypoplasia and coarctation of the aorta. The goals of this study were to compare echocardiographic and CTA findings in critical coarctation of the aorta, to evaluate each modality's influence on surgical approach for repair and determine if pre-operative measurements or surgical approach are associated with residual lesions/re-interventions. This was a single-center retrospective cohort study that included 85 neonates and infants who underwent repair of coarctation/arch hypoplasia by three months of age. Two groups were compared: patients with pre-operative echocardiograms only and patients with both echocardiogram and CTA evaluations. 44 (52%) patients received an echocardiogram and CTA, and 41 (48%) patients received an echocardiogram only. Patients in the CTA + echo group had smaller mitral valve and ascending aorta measurements (p = 0.01). When comparing CTA to echocardiogram measurements, the aortic valve annulus, ascending aorta, proximal and distal transverse arch, and isthmus were smaller on echo (p < 0.01). A smaller aortic valve annulus and aortic root as well as thoracotomy approach were associated with residual gradients/re-intervention (p < 0.01). Our study found that patients who underwent CTA preoperatively had smaller left-sided structures. Aortic measurements were smaller on echocardiogram when compared to CTA. Smaller left-sided structures proximal to the aortic arch and thoracotomy predicted the development of residual lesions/re-intervention. CTA is useful in the surgical planning for neonates with arch hypoplasia/coarctation and may help risk stratify for residual lesions/re-intervention.

Effect of cardiac graft rejection on semilunar valve function: implications for heart valve transplantation.

BACKGROUND: The treatment of neonates with unrepairable heart valve dysfunction remains an unsolved problem because there are no growing heart valve replacements. Heart valve transplantation is a potential approach to deliver growing heart valve replacements. Therefore, we retrospectively analysed the semilunar valve function of orthotopic heart transplants during rejection episodes. METHODS: We included children who underwent orthotopic heart transplantation at our institution and experienced at least one episode of rejection between 1/1/2010 and 1/1/2020. Semilunar valve function was analysed using echocardiography at baseline, during rejection and approximately 3 months after rejection. RESULTS: Included were a total of 31 episodes of rejection. All patients had either no (27) or trivial (4) aortic insufficiency prior to rejection. One patient developed mild aortic insufficiency during a rejection episode (P = 0.73), and all patients had either no (21) or trivial (7) aortic insufficiency at follow-up (P = 0.40). All patients had mild or less pulmonary insufficiency prior to rejection, which did not significantly change during (P = 0.40) or following rejection (P = 0.35). Similarly, compared to maximum pressure gradients across the valves at baseline, which were trivial, there was no appreciable change in the gradient across the aortic valve during (P = 0.50) or following rejection (P = 0.42), nor was there any meaningful change in the gradient across the pulmonary valve during (P = 0.55) or following rejection (P = 0.91). CONCLUSIONS: This study demonstrated that there was no echocardiographic evidence of change in semilunar valve function during episodes of rejection in patient with heart transplants. These findings indicate that heart valve transplants require lower levels of immune suppression than orthotopic heart transplants and provide partial foundational evidence to justify future research that will determine whether heart valve transplantation may deliver growing heart valve replacements for children.

Prematurity and Congenital Heart Disease: A Contemporary Review.

Congenital heart disease (CHD) is the most commonly reported birth defect in newborns. Neonates with CHD are more likely to be born prematurely, and a higher proportion of preterm neonates have CHD than their term counterparts. The implications of preterm birth on the cardiac and noncardiac organ systems are vast and require special management considerations. The feasibility of surgical interventions in preterm neonates is frequently limited by patient size and delicacy of immature cardiac tissues. Thus, special care must be taken when considering the appropriate timing and type of cardiac intervention. Despite improvements in neonatal cardiac surgical outcomes, preterm and early term gestational ages and low birthweight remain important risk factors for in-hospital mortality. Understanding the risks of early delivery of neonates with prenatally diagnosed CHD may help guide perioperative management in neonates who are born preterm. In this review, we will describe the risks and benefits of early delivery, postnatal cardiac and noncardiac evaluation and management, surgical considerations, overall outcomes, and future directions regarding optimization of perinatal evaluation and management of fetuses and preterm and early term neonates with CHD.

A late diagnosis of Pseudohypoaldosteronism type I in an infant with hypoplastic left heart syndrome presenting with failure to thrive.

Pseudohypoaldosteronism type I is caused by a peripheral resistance to aldosterone and can present with electrolyte abnormalities, poor growth, or dehydration. Although a rare disease, several case reports have been published regarding Pseudohypoaldosteronism type I in neonates and infants. We report a case of failure to thrive and hyponatremia in an infant with hypoplastic left heart syndrome who was subsequently found to have Pseudohypoaldosteronism type I.

Isolated Left Subclavian Artery From the Pulmonary Artery Masked by Pulmonary Hypertension.

Isolated subclavian artery arising from the pulmonary artery is exceedingly rare. Most cases are associated with other forms of congenital heart disease and typically present with subclavian or pulmonary steal syndromes. We report the case of a patient with pulmonary hypertension which masked the isolated subclavian artery, allowing it to masquerade as another common congenital heart lesion.