The competition for the best congenital paper kicked off with an entry from Bartholomew V. Simon, MD.
Myocyte preservation during neonatal cardiac surgery with cardioplegia remains a challenge, partly due to immature mitochondria that are unable to meet increased metabolic demands, according to Dr. Simon. Within mitochondria, the enzyme ATP synthase can increase the efficiency of ATP production by organizing ATP synthase monomers into multimers. The mitochondrial membrane protein cyclophilin D (CyPD) inhibits multimer assembly, and therefore, ATP production during fetal and neonatal life.
Dr. Simon and his colleagues examined a neonatal lamb cardiac surgery model in order to determine if myocyte arrest using cardioplegia would increase CyPD activity and lower the ATP synthase multimer:monomer ratio, thereby contributing to cellular damage.
Following the initiation of cardiopulmonary bypass in neonatal lambs, the heart was arrested using antegrade cardioplegia for approximately 60 minutes. Dr. Simon and his colleagues measured the left ventricular ejection fraction (LVEF) at baseline and 2 hours following myocyte arrest using transthoracic echocardiography. In addition, right ventricular muscle samples obtained at baseline and after approximately 60 minutes of myocyte arrest were examined to quantify the CyPD’s co-localization with ATP synthase using a two-dimensional immunoblot. The ATP synthase multimer:monomer ratio was quantified using native immunoblot. To determine if there was a comparable response in humans, right ventricular muscle samples were obtained from neonates following myocyte arrest with cardioplegia and similarly examined, said Dr. Simon.
In the eight lambs studied, the LVEF decreased from baseline measurements. In addition, cyclophilin D co-localization with ATP synthase increased significantly following myocyte arrest and the ATP synthase multimer:monomer ratio decreased in the majority of the lambs. Following monocyte arrest, the cumulative ATP synthase multimer:monomer ratio decreased significantly. In comparison to the lamb model, the researchers found that samples from three human neonates demonstrated statistically similar ATP synthase multimer:monomer ratios.
“Our study showed that neonatal myocyte arrest using cardioplegia increases CyPD’s inhibition of ATP synthase, decreasing ATP synthase multimer formation. This suggests that CyPD inhibition may be a novel target for neonatal myocardial protection,” Dr. Simon concluded.
The unique anatomy of the Taussig-Bing anomaly makes it challenging to achieve optimal surgical repair in these patients, including use of an arterial switch operation (ASO) and aortic arch reconstruction, according to Yasuyuki Kobayashi, MD, and his colleagues.
Dr. Kobayashi, of the Okayama University Hospital, Okayama, Japan, reported on their study to evaluate the long-term clinical outcome and to determine the factors related to reintervention, especially for pulmonary artery stenosis (PS) in these patients after an arterial switch operation.
They performed a retrospective review of patients with Taussig-Bing anomaly between 1993 and 2018 who underwent surgical repair incorporating ASO.
Dr. Kobayashi and his colleagues found that the ratio of the native pulmonary artery annulus size to the aortic annulus size ratio in patients having PS-related reintervention was significantly larger than that of the ones without reintervention. In addition, concomitant aortic arch reconstruction with ASO was associated with a significantly higher rate of PS-related reintervention.
“Regardless of complex coronary anatomy and associated anomalies, early and late survival was satisfactory. However reinterventions were frequently required, especially in pulmonary arteries,” Dr. Kobayashi stated. “Postoperative PS was strongly associated with patients having CoA and a larger native pulmonary valve, suggesting an optimal surgical reconstruction to achieve an appropriate aorto-pulmonary anatomic relationship with arch reconstruction is required at the time of ASO,” he concluded.
Double outlet right ventricle (DORV) can be manifested as diverse and heterogeneous features, and it is essential to thoroughly comprehend the intracardiac anatomy before the determination of a treatment strategy, according to Dong-Hee Kim, MD, and his colleagues at the Asan Medical Center, Seoul, Republic of Korea.
Dr. Kim reported on their study to evaluate the influence of anatomical characteristics on the selection of one of two strategies, anatomical repair (AR) or single ventricular palliation (SVP), and to reveal the effectiveness of a three-dimensionally (3D) printed cardiac model in determining surgical strategy in favor of AR.
Out of 294 consecutive patients with DORV from Jan 2008 to June 2018, 100 patients were identified, out of which 50 deemed suitable for AR and 50 regarded as candidates for SVP. Among the 50 patients with initial AR strategy, AR was completed in 43 patients and 7 patients are awaiting staged repair. Among the 50 patients with initial SVP strategy, 15 patients completed entire staged operations for SVP strategy (Fontan operation in 14 patients and Kawashima operation in 1 patient), 6 patients are awaiting staged palliation, and 14 patients were lost (inter-stage mortality in 12 patients and follow-up loss in 2 patients).
In the remaining 15 patients, there was a strategic crossover toward AR strategy during follow-up (AR completed in 13 patients and awaiting AR in 2 patients). On logistic regression analysis, statistically significant determinants for SVP in the entire cohort were left ventricular (LV) hypoplasia (odds ratio 5.16), mitral valve (MV) straddling (OR 11.94), and no use of 3D-printed model (OR 4.35). Among the 50 patients with initial SVP strategy, statistically significant predictors of strategic crossover toward AR were tricuspid valve interposition in the course of intracardiac baffling (OR 4.66) and utilization of the 3D cardiac printed model (OR 8.99).
“In this study, we found that AR can be facilitated with comprehensive preoperative anatomical assessment using the 3D-printed cardiac model in patients with complex DORV. However, AR remains challenging in patients with LV hypoplasia and MV straddling,” concluded Dr. Kim.