Potassium channels play diverse roles in regulating the behavior of pulmonary artery smooth muscle cells. In 2013, the discovery of KCNK3 (TASK1) as a new predisposing gene for pulmonary arterial hypertension (PAH) led to an update in the Nice Classification regarding the genetic origin of PAH. Decreased current via KCNA5 (Kv1.5) plays a key role in determining pulmonary arterial tone and vascular remodeling. The transformation of smooth muscle cells causes ion channel switching, such as the loss of BKca (Kca1.1) and the gain of IKca (Kca3.1), in immature proliferative smooth muscle cells and also induces cell migration, proliferation, and apoptosis resistance. Pulmonary smooth muscle cells from PAH patients demonstrate many cellular abnormalities linked to potassium channels. This review summarizes the current knowledge regarding the involvement of potassium channels in the development of PAH and discusses potential treatments to be developed in the near feature.

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In-body tissue architecture (IBTA), based on an encapsulation reaction, can produce autologous implantable tissues with desired shape, thickness, and robustness by simply embedding designed molds into subcutaneous pouches for 2 months. Tubular vascular grafts (biotubes), sheet-like patches (biosheets), or valved conduits (biovalves) have been developed for cardiovascular implants. Upon implantation, vascular, myocardial, or valvular tissues were regenerated within several months with high reliability. IBTA first demonstrated evidence of growth potential of biotubes when implanted using a beagle juvenile model. In this review article, we provide an overview of our recent IBTA-based work for pediatric cardiovascular surgery.

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Tracheomalacia is a complex anomaly associated with congenital heart disease. Surgery is required for patients with severe symptomatic tracheomalacia. Reported here is a case of hypoplastic left heart syndrome (HLHS) complicated by tracheomalacia with symptoms that improved after the patient underwent a modified Norwood operation involving a novel pulmonary artery trunk-saving procedure. A 5-month-old girl with HLHS underwent bilateral pulmonary artery banding at 12 days of age. Bronchoscopy was performed owing to respiratory distress, and tracheomalacia was diagnosed at 4 months. At 5 months of age, a Norwood and bidirectional Glenn procedure was scheduled for her cardiac malformation. The procedure consisted of dividing both pulmonary arteries at the base of the main pulmonary artery trunk, closing the branch defect directly, and end-to-end anastomosis of both pulmonary arteries to utilize the main pulmonary artery trunk tissue for aortic reconstruction longitudinally and to make circumstances small for the room of the left pulmonary hilum. Postoperatively, her respiratory distress was resolved and bronchoscopy demonstrated an improved tracheal shape.

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Patients with asplenia syndrome usually have various cardiac malformations. Although most of these patients are Fontan candidates, some cannot achieve Fontan completion because of pulmonary artery and vein problems. We report a case of asplenia syndrome with Fontan completion achieved after pulmonary venous obstruction (PVO) was repaired twice. The patient underwent her first operation (repair of total anomalous venous connection, modified Blalock–Taussig [BT] shunt, patent ductus arteriosus division, and pulmonary artery plasty) at 8 days of age (body weight: 2,097 g). As the pulmonary venous orifice was obstructed postoperatively, we performed surgical PVO release, but left PVO occurred again. We created a left modified BT shunt to increase pulmonary flow to the left pulmonary artery and preserve pulmonary vein flow, and performed consecutive PVO release . Subsequently, Fontan completion was achieved through a bidirectional Glenn operation with additional flow from the systemic to the pulmonary artery. Planned adjustment of pulmonary blood flow can be an effective way to prevent progression of PVO and promote pulmonary artery growth.

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Evaluation of the coronary arterial intima is important in the follow-up of coronary arterial lesions complicated by Kawasaki disease (KD). We evaluated the lesions in four cases of KD using optical coherence tomography (OCT), which can show vessel wall thickness on magnetic resonance imaging (MRI) of the coronary vessel wall using the black blood method (BB). All cases showed intimal thickening on OCT at areas of thickened vessel wall using BB. Although vessel wall thickening was detected as iso-intensity with BB, OCT showed various histological features of the intima at these lesions. We revealed that intimal thickening is evaluable using BB compared with OCT findings. MRI of coronary vessel walls with BB may be useful in screening for intimal thickening of coronary arterial lesions complicated with KD.

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Coronary artery fistula (CAF) is a rare congenital anomaly, and a bilateral coronary artery origin is especially rare. We report the case of a 4-year-old boy who was diagnosed with a heart murmur without symptoms at 7 months of age. He underwent CAF closure via right ventriculotomy. Most cases of CAF are clinically asymptomatic in young patients. The CAF treatment strategy is determined by the symptoms, properties of the aneurysmal vessel, and the size of the fistula. As heart failure and exertional angina gradually appear in adulthood, treatment may be required earlier after diagnosis, depending on the patient’s condition. Various surgical options for closing the fistula have been reported; however, we selected right ventriculotomy in this case because of myocardial bridging of the fistula coronary arteries.

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Lamin A/C gene (LMNA) mutations can cause a variety of clinical phenotypes, including skeletal muscle disease, metabolic disorders, and cardiac abnormalities. The cardiac phenotype associated with LMNA mutation is characterized by atrial fibrillation, conduction disturbances, ventricular arrhythmias, and dilated cardiomyopathy. Although the use of cardiac resynchronization therapy (CRT) is increasing for adult patients with LMNA-related cardiomyopathy, its use in pediatric patients has been limited. We present a case of congenital muscular dystrophy with LMNA mutation. The patient acquired ambulation at 16 months but gradually lost independent ambulation at 4 years of age. Cardiac involvement with reduced systolic function became apparent when she was 8 years old. Electrocardiography revealed complete atrioventricular block and nonsustained ventricular tachycardia. At the age of 13 years, severe bradycardia and atrial fibrillation were observed. The patient was repeatedly hospitalized because of congestive heart failure. As severe bradycardia caused heart failure, a biventricular pacemaker was implanted using a transvenous approach at 14 years of age. The CRT led to alleviation of the clinical symptoms. In summary, we present the outcome of CRT in a 14-year-old girl with LMNA-related cardiomyopathy. This case suggests that CRT initiation is a promising therapeutic strategy not just for adult patients with LMNA-related cardiomyopathy but also for pediatric patients.

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We report a case of a 12-year-old girl who had experienced numerous prior episodes of epistaxis since childhood. Her mother and maternal grandfather also had had similar episodes. She had experienced dyspnea on exertion since the age of nine. She was admitted to our hospital with polycythemia and exhibited a continuous murmur on the back left side. Chest X-ray showed a nodular shadow in the lower left lung field. Contrast-enhanced computed tomography (CT) scan of the chest revealed nodules with blood vessels in the left S1 and S9 segments. As the diagnostic criteria for hereditary hemorrhagic telangiectasia (HHT) were satisfied, the patient was diagnosed as having a pulmonary arteriovenous fistula (PAVF) with HHT. Transcatheter embolization was indicated for the PAVF in the left S9 segment. Coil embolization was performed on the arteries feeding the PAVF. After coil embolization, the PAVF disappeared and the patient’s dyspnea on exertion alleviated. We performed genetic testing on her and her mother, and a de novo mutation IVS2-1G＞C (c.220-1G＞C) was found in endoglin (ENG) in both. We suggested that the mutation was a possible cause of HHT. Further studies are needed to demonstrate the association between the gene mutation and HHT.

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The mTOR inhibitor, everolimus, has been reported to be effective against renal angiomyolipoma and subependymal giant cell astrocytoma, but its use for cardiac rhabdomyoma has been rarely reported. Here we report the case of a 10-month-old male infant who was diagnosed with tuberous sclerosis (TS) during the fetal stage after being identified with subependymal nodules in both the lateral ventricles and multiple cardiac tumors. After birth, the small cardiac tumors regressed, but the larger tumors persisted on the right ventricular septum and on the free wall and apex of the left ventricle. There was no stenosis of inflow or outflow routes. Intractable convulsions occurred 3 months after birth. Subependymal giant cell astrocytoma was found using cranial magnetic resonance imaging. Therefore, everolimus (3.0 mg/m²/day) was initiated 10 months after birth to treat the tumors. This resulted in regression of the subependymal giant cell astrocytoma and controlled the convulsions. The cardiac tumor on the left ventricular free wall disappeared after 1 month of everolimus administration, and the tumor on the apex of the left ventricle disappeared after 7 months. The tumor persisting on the right ventricular septum was 23.4×16.7 mm before everolimus was administered, but decreased to 16.1×4.3 mm after 1 month of its administration. Everolimus may cause rapid regression of cardiac rhabdomyoma that accompanies TS.

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