Toshihide Asou

Myocardial Distribution of Retrograde Flow through the Coronary Sinus of the Excised Normal Canine Heart

Myocardial distribution of the retrograde flow through the coronary sinus in the canine heart was evaluated by observing the corrosion casts of the myocardial vessels after coronary sinus injection of a low-viscosity resin, Mercox, a compound that passes through capillaries. The apex and the left ventricular free wall were well perfused at the microvascular level, even in the presence of complete left main coronary artery occlusion, whereas the right ventricular free wall was not perfused effectively at this level in any heart. Although there was considerable variation in the perfusion of the ventricular septum from heart to heart, the entire septum was not perfused in some of the hearts. We considered this poor perfusion of the septum to be due to the presence of well-developed thebesian veins in the septum. Retrograde coronary sinus perfusion of cardioplegic solution may be a valuable alternative to protect the left ventricular free wall, especially in cases of critical coronary artery stenosis or occlusion. However, antegrade perfusion should be used also, whenever possible, for adequate protection of the septum and the right ventricular free wall.

Prostaglandin E2 Inhibits Elastogenesis in the Ductus Arteriosus via EP4 Signaling

Background— Elastic fiber formation begins in mid-gestation and increases dramatically during the last trimester in the great arteries, providing elasticity and thus preventing vascular wall structure collapse. However, the ductus arteriosus (DA), a fetal bypass artery between the aorta and pulmonary artery, exhibits lower levels of elastic fiber formation, which promotes vascular collapse and subsequent closure of the DA after birth. The molecular mechanisms for this inhibited elastogenesis in the DA, which is necessary for the establishment of adult circulation, remain largely unknown. Methods and Results— Stimulation of the prostaglandin E2 (PGE2) receptor EP4 significantly inhibited elastogenesis and decreased lysyl oxidase (LOX) protein, which catalyzes elastin cross-links in DA smooth muscle cells (SMCs), but not in aortic SMCs. Aortic SMCs expressed much less EP4 than DASMCs. Adenovirus-mediated overexpression of LOX restored the EP4-mediated inhibition of elastogenesis in DASMCs. In EP4-knockout mice, electron microscopic examination showed that the DA acquired an elastic phenotype that was similar to the neighboring aorta. More importantly, human DA and aorta tissues from 7 patients showed a negative correlation between elastic fiber formation and EP4 expression, as well as between EP4 and LOX expression. The PGE2-EP4-c-Src-phospholipase C (PLC)&ggr;–signaling pathway most likely promoted the lysosomal degradation of LOX. Conclusions— Our data suggest that PGE2 signaling inhibits elastogenesis in the DA, but not in the aorta, through degrading LOX protein. Elastogenesis is spatially regulated by PGE2-EP4 signaling in the DA.

Comparative study of cell saver and ultrafiltration nontransfusion in cardiac surgery

Hemoconcentration for the establishment of no-donor blood transfusion in open heart surgery was assessed in regard to both the saving of protein and platelets and the exclusion of free hemoglobin. Two different types of hemoconcentrator were compared: the ultrafilter (group I, 6 patients) and the Cell Saver (group II, 6 patients). The total serum protein level, expressed as the percent recovery of the preoperative value, after hemoconcentration was significantly higher in group I (group I versus group II: total serum protein, 118% versus 87% [p less than 0.05]; fibrinogen, 77% versus 50% [p less than 0.01]; immunoglobulin, 83% versus 60% [p less than 0.01]). The platelets also seemed to be well preserved after hemoconcentration in group I. Although the exclusion of free hemoglobin from plasma was inferior in group I compared with group II, the postoperative plasma free hemoglobin level did not increase in group I. We conclude that use of the Cell Saver in nontransfusion cardiopulmonary bypass might cause a severe depletion of various proteins and that the ultrafilter is both safer and more useful if employed routinely.

Surgical Results of Anomalous Origin of the Right Pulmonary Artery From the Ascending Aorta Including Reoperation for Infrequent Complications

BACKGROUND We evaluated the results of surgery for an anomalous origin of the right pulmonary artery from the ascending aorta. METHODS From August 1986 to December 2005, 8 children (6 neonates) aged 7 to 180 days (mean, 35 +/- 59 days) with anomalous origin of the right pulmonary artery from the ascending aorta underwent surgical repair at our institute. All except one child, who had the distal form, had the proximal form. Cardiac catheterization showed that the left pulmonary artery to systemic pressure ratio was 1.0 or more. Surgery was performed by direct anastomosis in 7 patients and by graft interposition in 1. RESULTS There were no operative or late deaths. All patients postoperatively underwent cardiac catheterization that showed decreased left pulmonary artery to systemic pressure ratio ranging from 0.2 to 0.6. Follow-up periods ranged from 2 months to 13 years. We undertook reoperations for two infrequent postoperative causes. One patient exhibited significant supravalvar aortic stenosis and required patch enlargement of the ascending aorta 3 years after operation. The other patient (with the distal form) needed a reoperation after 1 month because of progressive stenosis at the anatomic site. Graft interposition was performed, and histopathologic examination showed that the tissue from the stenotic region looked like that of a ductus. CONCLUSIONS We undertook surgical repair for anomalous origin of the right pulmonary artery from the ascending aorta. Pulmonary hypertension was improved in all patients. Careful follow-up was necessary to detect supravalvar aortic and anastomotic stenosis early and late after operation.

Veno-venous bypass to prevent myocardial ischemia during right heart bypass operation in PA, IVS, and RV dependent coronary circulation

There is a risk of myocardial ischemia in patients with pulmonary atresia and intact ventricular septum associated with right ventricle dependent coronary circulation, especially during open heart operation. Cardiopulmonary bypass unloads the right ventricle, and thereby reduces the coronary perfusion pressure in an area that is wholly or partly dependent on the right ventricle. We present a veno-venous bypass technique to keep the right ventricle beating and ejecting to supply the oxygenated blood into the right ventricle dependent myocardium and consequently to prevent myocardial ischemia during right heart bypass operation.

Pulmonary Artery Banding for Functionally Single Ventricles: Impact of Tighter Banding in Staged Fontan Era

BACKGROUND In this study, we assessed our surgical strategy, tighter pulmonary artery banding (PAB) during the neonatal period, as an initial step followed by early application of bidirectional cavopulmonary shunts (BCPS) in infancy, to treat functionally single ventricles with unobstructed pulmonary blood flow. METHODS On the basis of our surgical strategy, 68 consecutive patients underwent PAB and were divided into two groups, group 1 (January 1990 to June 2003; n = 30) and group 2 (July 2003 to August 2008; n = 38). The median age at PAB was 45 days in group 1 and 9 days in group 2. The circumference of the bands was significantly shorter in group 2 than in group 1, corresponding to the patients weight in kg plus 19.0 +/- 0.6 mm in group 1 or 17.0 +/- 0.3 mm in group 2 (p = 0.003). RESULTS Cardiac catheterization before the right heart bypass operation showed that the pulmonary artery index (group 1, 322 +/- 29; group 2, 283 +/- 27 mm(2)/m(2); p = 0.01), pulmonary resistance index (group 1, 2.4 +/- 0.2; group 2, 1.9 +/- 0.1 U x m(2); p = 0.03), and ventricular end-diastolic volume (group 1, 212 +/- 19%; group 2, 166 +/- 9%; p = 0.04) were significantly different between the two groups. The rates for achievement of right heart bypass at 12 months (group 1, 19%; group 2, 81%; p < 0.01) and survival at 3 years (group 1, 70%; group 2, 87%; p = 0.04) were significantly higher in group 2 than in group 1. CONCLUSIONS Our present strategy could prevent volume overload and improve the achievement and survival rates of right heart bypass operations.

Rapid Two-Stage Starnes Procedure for a Symptomatic Neonate With Ebstein Anomaly

We present a rapid two-stage Starnes procedure for a seriously symptomatic neonate with the prenatal diagnosis of Ebstein anomaly. At 16 hours after birth, we performed an emergency operation consisting of main pulmonary artery ligation, plication of the right atrial and right ventricular wall, modified Blalock-Taussig shunt, and patent ductus arteriosus ligation, without cardiopulmonary bypass. At age 12 days, we then performed the Starnes procedure using a glutaraldehyde-treated autologous pericardial patch with a 4-mm fenestration to close the tricuspid valve orifice. The infants postoperative course was excellent. A rapid two-stage Starnes procedure is useful for treating a seriously symptomatic neonate with Ebstein anomaly.

Extracorporeal life support after cardiac surgery in children: outcomes from a single institution.

Extracorporeal life support (ECLS) is used after congenital heart surgery for several indications, including failure to separate from cardiopulmonary bypass, postoperative low cardiac output syndrome, and extracorporeal cardiopulmonary resuscitation. Here, we assessed the outcomes of ECLS in children after cardiac surgery at our institution. Medical records of all children who required postoperative ECLS at our institution were reviewed. Between 2003 and 2011, 36 (1.4%) of 2541 pediatric cardiac surgical cases required postoperative ECLS. Median age of patients was 64 days (range: 0 days-4.1 years). ECLS was in the form of either extracorporeal membrane oxygenation (ECMO; n = 24) or ventricular assist system (VAS; n = 12). Mean duration of ECLS was 4.9 ± 4.2 days. Overall, 21 patients (58%) were weaned off ECLS, and 17 patients (47%) were successfully discharged from the hospital. Patients with biventricular heart (BVH) had higher survival-to-hospital discharge rates compared with those with univentricular heart (UVH) (P = 0.019). Regarding ECLS type, UVH patients who received VAS showed higher rates of device discontinuation than UVH patients who received ECMO (P = 0.012). However, rates of hospital discharge were not significantly different between UVH patients who received VAS or ECMO. Surgical interventions, such as banding of Blalock-Taussig shunt to reduce pulmonary blood flow or placing bidirectional cavopulmonary shunt to minimize ventricular volume overload, were effective for weaning off ECLS in patients with UVH. ECLS is beneficial to children with low cardiac output after cardiac surgery. Rates of survival-to-hospital discharge were higher in BVH patients than UVH patients. Additional interventions to reduce ventricular volume load may be effective for discontinuing ECLS in patients with UVH.

Surgical management of muscular trabecular ventricular septal defects

Despite recent advances in diagnosis, surgical techniques, and postoperative care of children with congenital cardiac defects, muscular trabecular ventricular septal defects (VSDs) are still a therapeutic challenge. Among these defects, it is more difficult to achieve secure and complete closure of low trabecular or apical VSDs because of the presence of numerous muscular trabeculations overlying the defect. When they are associated with “Swiss cheese”-type of VSDs, it is almost impossible to visualize the true edges of the defect through the transatrial approach. Consequently, there remains an unacceptable incidence of mortality and morbidity when compared to those that occur with closure of the usual perimembranous VSD. Although various techniques for closure of these difficult trabecular VSDs have been attempted, there is still a significant incidence of complications in the surgical management of trabecular VSDs, mostly significant residual shunts, a need for multiple reoperations, and severe left ventricular dysfunction. This article describes the anatomical details and classification of muscular trabecular VSDs. It also reviews several techniques currently utilized and their outcomes.

Decreased serum osmolality promotes ductus arteriosus constriction

AIMS At birth, dynamic changes occur in serum components and haemodynamics, such as closure of the ductus arteriosus (DA). A previous study demonstrated that, in full-term human neonates, serum osmolality decreased transiently after birth, but recovered over the next few days. However, the significance of this transient decrease in osmolality has never been addressed. The objective of the present study was to examine the role of changes in serum osmolality after birth in DA closure. METHODS AND RESULTS We found that rats exhibited a similar transient hypoosmolality after birth. Hypotonic stimulation induced constriction of DA rings and increased Ca(2+) transient in DA smooth muscle cells, but not in the aorta. The hypoosmotic sensor transient receptor potential melastatin 3 (TRPM3) was highly expressed in the rat DA, and TRPM3 silencing abolished the Ca(2+) response to hypoosmolality. Pregnenolone sulfate stimulation of TRPM3 induced rat DA constriction ex vivo and in vivo. Furthermore, hypertonic fluid injection impaired rat DA closure. In humans, neonatal serum hypoosmolality was observed in relatively mature preterm infants (≥28 weeks). In extremely preterm infants (<28 weeks), however, this hypoosmolality was absent. Instead, a rapid increase in osmolality occurred thereafter. Such an increase was greater, in particular, among patent DA (PDA) patients. CONCLUSIONS A transient decrease in serum osmolality may promote DA closure during the first few days of life. Adjusting serum osmolality to proper levels might help to prevent the onset of PDA, improving the therapeutic outcome in extremely preterm infants.