Acute Dapagliflozin Administration Ameliorates Cardiac Surgery-Associated Acute Kidney Injury in a Rabbit Model.

BACKGROUND: Several studies have shown that sodium-glucose cotransporter-2 inhibitors have a renoprotective effect on acute kidney injury (AKI), but their effect on cardiac surgery-associated AKI is unknown.Methods and Results: AKI was induced in 25 rabbits without diabetes mellitus by cardiopulmonary bypass (CPB) for 2 h and they were divided into 5 groups: sham; dapagliflozin-treated sham; CPB; dapagliflozin-treated CPB; and furosemide-treated CPB (n=5 in each group). Dapagliflozin was administered via the femoral vein before initiating CPB. Kidney tissue and urine and blood samples were collected after the surgical procedure. There were no differences in the hemodynamic variables of each group. Dapagliflozin reduced serum creatinine and blood urea nitrogen concentrations, and increased overall urine output (all P<0.05). Hematoxylin and eosin staining showed that the tubular injury score was improved after dapagliflozin administration (P<0.01). Dapagliflozin administration mitigated reactive oxygen species and kidney injury molecule-1 as assessed by immunohistochemistry (both P<0.0001). Protein expression analysis showed improvement of inflammatory cytokines and apoptosis, and antioxidant enzyme expression was elevated (all P<0.05) through activation of the nuclear factor erythroid 2-related factor 2 pathway (P<0.01) by dapagliflozin. CONCLUSIONS: Acute intravenous administration of dapagliflozin protects against CPB-induced AKI. Dapagliflozin may have direct renoprotective effects in renal tubular cells.

Necrostatin-1 Attenuates Delayed Paraplegia after Transient Spinal Cord Ischemia in Rabbits by Inhibiting the Upregulation of Receptor-Interacting Protein Kinase 1 and 3.

BACKGROUND: Delayed-onset paraplegia is a disastrous complication after thoracoabdominal aortic open surgery and thoracic endovascular aortic repair. Studies have revealed that transient spinal cord ischemia caused by temporary occlusion of the aorta induces delayed motor neuron death owing to apoptosis and necroptosis. Recently, necrostatin-1 (Nec-1), a necroptosis inhibitor, has been reported to reduce cerebral and myocardial infarction in rats or pigs. In this study, we investigated the efficacy of Nec-1 in delayed paraplegia after transient spinal cord ischemia in rabbits and assessed the expression of necroptosis- and apoptosis-related proteins in motor neurons. METHODS: This study used rabbit transient spinal cord ischemia models using a balloon catheter. They were divided into a vehicle-treated group (n = 24), Nec-1-treated group (n = 24), and sham-controls (n = 6). In the Nec-1-treated group, 1 mg/kg of Nec-1 was intravascularly administered immediately before ischemia induction. Neurological function was assessed using the modified Tarlov score, and the spinal cord was removed 8 hr and 1, 2, and 7 days after reperfusion. Morphological changes were examined using hematoxylin and eosin staining. The expression levels of necroptosis-related proteins (receptor-interacting protein kinase [RIP] 1 and 3) and apoptosis-related proteins (Bax and caspase-8) were assessed using western blotting and histochemical analysis. We also performed double-fluorescence immunohistochemical studies of RIP1, RIP3, Bax, and caspase-8. RESULTS: Neurological function significantly improved in the Nec-1-treated group compared with that in the vehicle-treated group 7 days after reperfusion (median 3 and 0, P = 0.025). Motor neurons observed 7 days after reperfusion were significantly decreased in both groups compared with the sham group (vehicle-treated, P < 0.001; Nec-1-treated, P < 0.001). However, significantly more motor neurons survived in the Nec-1-treated group than in the vehicle-treated group (P < 0.001). Western blot analysis revealed RIP1, RIP3, Bax, and caspase-8 upregulation 8 hr after reperfusion in the vehicle-treated group (RIP1, P = 0.001; RIP3, P = 0.045; Bax, P = 0.042; caspase-8, P = 0.047). In the Nec-1-treated group, the upregulation of RIP1 and RIP3 was not observed at any time point, whereas that of Bax and caspase-8 was observed 8 hr after reperfusion (Bax, P = 0.029; caspase-8, P = 0.021). Immunohistochemical study revealed the immunoreactivity of these proteins in motor neurons. Double-fluorescence immunohistochemistry revealed the induction of RIP1 and RIP3, and that of Bax and caspase-8, in the same motor neurons. CONCLUSIONS: These data suggest that Nec-1 reduces delayed motor neuron death and attenuates delayed paraplegia after transient spinal cord ischemia in rabbits by selectively inhibiting necroptosis of motor neurons with minimal effect on their apoptosis.

Veno-venous extracorporeal membrane oxygenation support of pulmonary insufficiency using Avalon Elite® cannula in pediatric patients.

The "Avalon Elite®" cannula is a double-lumen cannula used to establish veno-venous extracorporeal membrane oxygenation support. The reported advantages are that extracorporeal circulation can be established by cannulating through the right internal jugular vein only, and there is less re-circulation than with a two-cannula technique. It is available in a wide range of cannula sizes and can be used in a variety of patients, from children to adults. We herein report three pediatric cases in which an Avalon Elite® cannula was useful. The first was a case of acute mitral regurgitation due to idiopathic chordal rupture for postoperative severe lung injury and atelectasis due to cardiogenic pulmonary edema. The second was a case of end-stage radiation pneumonitis for safe transfer to facility of lung transplantation. The third was a convalescent case of fulminant myocarditis with severe atelectasis due to cardiogenic pulmonary edema. In each case, veno-venous extracorporeal membrane oxygenation using an Avalon Elite® cannula was established, the expected sufficient support was secured, and a good clinical course was obtained without major complications associated with an Avalon Elite® cannula.

Evaluation of Ductal Tissue in Coarctation of the Aorta Using X-Ray Phase-Contrast Tomography.

We assessed the histological accuracy of X-ray phase-contrast tomography (XPCT) and investigated three-dimensional (3D) ductal tissue distribution in coarctation of the aorta (CoA) specimens. We used nine CoA samples, including the aortic isthmus, ductus arteriosus (DA), and their confluences. 3D images were obtained using XPCT. After scanning, the samples were histologically evaluated using elastica van Gieson (EVG) staining and transcription factor AP-2 beta (TFAP2B) immunostaining. XPCT sectional images clearly depicted ductal tissue distribution as low-density areas. In comparison with EVG staining, the mass density of the aortic wall positively correlated with elastic fiber formation (R = 0.69, P < 0.001). TFAP2B expression was consistent with low-density area including intimal thickness on XPCT images. On 3D imaging, the distances from the DA insertion to the distal terminal of the ductal media and to the intima on the ductal side were 1.63 ± 0.22 mm and 2.70 ± 0.55 mm, respectively. In the short-axis view, the posterior extension of the ductal tissue into the aortic lumen was 79 ± 18% of the diameter of the descending aorta. In three specimens, the aortic wall was entirely occupied by ductal tissue. The ductal intima spread more distally and laterally than the ductal media. The contrast resolution of XPCT images was comparable to that of histological assessment. Based on the 3D images, we conclude that complete resection of intimal thickness, including the opposite side of the DA insertion, is required to eliminate residual ductal tissue and to prevent postoperative re-coarctation.

[A New-born Case of Total Conus Defect and Single Coronary Artery with Situs Inversus Totalis Suspected Kartagener Syndrome].

We report a new-born case of total conus defect type ventricular septal defect (VSD) and single coronary artery with situs inversus totalis, suspected Kartagener syndrome clinically. After the birth, as the patient had suffered from respiratory distress due to high pulmonary blood flow through the large defect, surgery was planned at age of 14-days after birth. Under median sternotomy and cardiac arrest, patch closure of VSD was performed as ordinary fashion. In spite of the situs inversus totalis and single coronary artery arose from right coronary sinus, operator could have completed all of surgical procedure at the right side of patient as usual. No remarkable respiratory complication was seen postoperatively and she was discharged from hospital 18th day in a good condition.

Intact Imaging of Human Heart Structure Using X-ray Phase-Contrast Tomography.

Structural examination of human heart specimens at the microscopic level is a prerequisite for understanding congenital heart diseases. It is desirable not to destroy or alter the properties of such specimens because of their scarcity. However, many of the currently available imaging techniques either destroy the specimen through sectioning or alter the chemical and mechanical properties of the specimen through staining and contrast agent injection. As a result, subsequent studies may not be possible. X-ray phase-contrast tomography is an imaging modality for biological soft tissues that does not destroy or alter the properties of the specimen. The feasibility of X-ray phase-contrast tomography for the structural examination of heart specimens was tested using infantile and fetal heart specimens without congenital diseases. X-ray phase-contrast tomography was carried out at the SPring-8 synchrotron radiation facility using the Talbot grating interferometer at the bending magnet beamline BL20B2 to visualize the structure of five non-pretreated whole heart specimens obtained by autopsy. High-resolution, three-dimensional images were obtained for all specimens. The images clearly showed the myocardial structure, coronary vessels, and conduction bundle. X-ray phase-contrast tomography allows high-resolution, three-dimensional imaging of human heart specimens. Intact imaging using X-ray phase-contrast tomography can contribute to further structural investigation of heart specimens with congenital heart diseases.

[Hemorrhagic Shock due to an Aortoesophageal Fistula in an Infant with a Double Aortic Arch；Report of a Case].

We experienced a case of a female infant with a double aortic arch (DAA) which formed an aortoesophageal fistula, leading to hemorrhagic shock. The patient had severe dyspnea at birth, and was intubated and tube-feeding was started through a nasogastric tube immediately after birth. A DAA was diagnosed by contrast-enhanced computed tomography. Due to abdominal organ malformation, we proceeded with abdominal surgery. Forty-nine days after birth, she suddenly developed massive hematemesis and went into hemorrhagic shock. The bleeding was stopped using an endoscope and was shown to have originated from the esophagus membrane. Compression of the esophageal wall by both the inserted nasogastric tube and vascular ring led to the development of ulceration, resulting in a fistula associated with massive hematemesis. An operation for a DAA was performed on the 53rd day after birth. The inferior side of the DAA was cut, to decompress the bronchus and esophagus and close the fistula. The patient's postoperative course was good and there was no further bleeding. In severe cases of a DAA who require respiratory intubation and tube feeding from a nasogastric tube it is important to carry out surgery as soon as possible.

[Mid-aortic syndrome in 2-year old boy presenting with severe left ventricular dysfunction; report of a case].

Mid aortic syndrome is uncommon acquired or congenital condition characterized by segmental narrowing of the abdominal or distal descending thoracic aorta. If left untreated, it result in life threatening complications. We described the case of 2-year-old boy admitted to our hospital for hypertension and heart failure. Diagnosis of mid aortic syndrome was made with severe stenosis in distal descending aorta. With consideration of growth, we avoided bypass grafting and implantation with prothesic graft. For severe adhesion, we performed patch aortoplasty with 0.4 mm expanded polytetrafluoroethylene (ePTFE) patch. Postoperative course was unevetful. His blood pressure and left ventricular function was normalized. He was discharged on the 20st day after the surgery.

Biventricular repair using subvalvular techniques for unbalanced atrioventricular septal defect.

We report the case of a 19-month-old girl with a right-dominant unbalanced atrioventricular septal defect and severe right-sided atrioventricular valve regurgitation who underwent biventricular repair using basal chordae resection, artificial chordae reconstruction and a left-sided atrioventricular valvuloplasty. At 14-month postoperative follow-up, the patient had minimal heart failure, gained weight and adapted to biventricular circulation.

Echocardiographic Evaluation of Postoperative Coaptation Geometry of Left AV Valve in Complete Atrioventricular Septal Defect.

Background: We sought to determine the difference in geometric parameters in the left atrioventricular valve (LAVV) postoperative complete atrioventricular septal defect (CAVSD) compared to the normal heart, and the correlation between geometric and functional parameters for detecting the mechanism of LAVV regurgitation (LAVVR) in CAVSD. Methods: LAVV geometric parameters based on complete and acceptable quality echocardiograms of 18 patients with repaired CAVSD compared with 17 normal controls. LAVVR severity was also quantified by indexed vena contracta (I-VC) (mm) and % jet area/left atrium area (% Jet/LA), and the correlation with LAVV parameters in the CAVSD group was investigated. Results: In the CAVSD group, the posterior closing angle (Pc) was nearly the same as the anterior closing angle (Ac), yet in the normal heart, the Pc angle was double the Ac angle. The anterior opening angle (Ao) and posterior-to-anterior leaflet diameter ratio (a/p) in the CAVSD group was also significantly smaller. The CAVSD group also had a shorter indexed coaptation length (I-CL) and indexed tenting height (I-TH). Displacement length (ΔD) differed completely between the CAVSD and Normal groups, and also showed a strong positive correlation to the functional parameters of LAVVR (% Jet/LA: r = .70, P = .02; I-VC: r = .60, P = .02). Conclusions: The parameters in this study were applicable to CAVSD AV valve coaptation characteristics. We introduced 2 novel measures that may provide important insights into the differences in geometry and performance of the LAVV in repaired CAVSD as compared to normal hearts.

Superior restoration of left ventricular performance after prolonged single-dose del Nido cardioplegia in conjunction with terminal warm blood cardioplegic reperfusion.

OBJECTIVES: An incomplete restoration of left ventricular contractility after del Nido cardioplegia was noted in our recent study. This study tested the hypothesis that terminal warm blood cardioplegia promotes a prompt restoration of left ventricular performance after a prolonged single-dose del Nido cardioplegia. METHODS: Fourteen piglets were subjected to 120 minutes of arrest by del Nido cardioplegia without terminal warm blood cardioplegia (del Nido cardioplegia group; n = 7) or with terminal warm blood cardioplegia before reperfusion (terminal warm blood cardioplegia group; n = 7). The other 7 piglets underwent total cardiopulmonary bypass without ischemia/reperfusion for 150 minutes (control group). Left ventricular function was assessed by percent recovery of end-systolic elastance as the contractility and percent end-diastolic pressure-volume relationship as the compliance using a conductance catheter. Troponin T and the mitochondrial score were also measured. RESULTS: Depressed percent recovery of end-systolic elastance was sustained in the del Nido cardioplegia group, and a prompt restoration of end-systolic elastance was achieved using terminal warm blood cardioplegia (57.9 ± 17.8 vs 94.7 ± 13.1, P < .028). Percent end-diastolic pressure-volume relationship at the early phase was better in the terminal warm blood cardioplegia compared with the del Nido group (88.5 ± 24.0 vs 101.4 ± 16.8, P = .050). Troponin T was higher in the terminal warm blood cardioplegia compared with the control group (0.80% ± 0.21% and 1.49% ± 0.31%, respectively, P = .002). The mitochondrial score was equivalent in all groups. Spontaneous restoration to sinus rhythm was more frequent in the terminal warm blood cardioplegia group than in the del Nido cardioplegia group (6/7 vs 1/7, P < .028). CONCLUSIONS: The supplementary use of terminal warm blood cardioplegia achieved prolongation of the safe ischemic time up to 120 minutes for a single-dose application.

Modified Del Nido Cardioplegia and Its Evaluation in a Piglet Model.

Del Nido cardioplegia (DN) is not available worldwide as the required solution is made from a commercial base (PlasmaLyte) that is not approved in all countries. We report our own modified DN solution and confirm its safety and effectiveness. Fourteen piglets were subjected to 90 minutes of global ischemia on cardiopulmonary bypass induced by original DN (n = 7) or NS (normal saline)-based DN (n = 7). Our DN solution begins with a base of NS (800 mL) and distilled water (200 mL), to which are added 15 mL KCl (2 mEq/mL), 17 mL NaHCO3 (1 mEq/mL), 10 mL MgSO4 (0.2 g/mL), 13 mL lidocaine 1%, and 13 mL mannitol 25%. LV function recovery was assessed in end-systolic elastance (EES) as systolic function and end-diastolic pressure-volume relationship (EDPVR) as diastolic function using a conductance catheter. Creatine kinase-MB (CK-MB) and mitochondrial score were also measured. Left ventricular (LV) contractility after ischemia (%EES ± SD) was not significantly different between the group induced by original DN (89.3 ± 20.6%) and the group induced by NS-based DN (99.3 ± 18.4%). LV compliance (%EDPVR ± SD) was likewise not significantly different between these groups (102.7 ± 28.2% vs 94.4 ± 22.8%, PL vs NS, respectively). CK-MB was equivalent between the groups. Mitochondrial scores were not significantly different between the groups, and this difference did not cause severe damage. NS-based DN preserves LV function recovery after prolonged global ischemia as effectively and as safely as original DN does. NS-based modified DN can be substituted for original DN.

Sliding Aortoplasty for Severe Supravalvular Aortic Stenosis After the Lecompte Procedure.

This report describes the case of a 3-year-old boy with supravalvular aortic stenosis after an arterial switch operation in whom the stenosis was successfully repaired using an ascending sliding arch aortoplasty without using a patch. Because patches were avoided, growth of the surgical site is expected. Ascending sliding arch aortoplasty and longitudinal expansion of the pulmonary bifurcation are useful for relieving stenosis and preventing supravalvular aortic stenosis recurrence after an arterial switch operation.

Ascending aortic extension to enlarge the retroaortic space in children after the Norwood procedure.

Left pulmonary artery stenosis is a well-recognized complication following the Norwood procedure. We herein report two cases in which ascending aortic extension was performed to enlarge the retroaortic space in children with left pulmonary artery stenosis after the Norwood procedure. We used graft interposition in the ascending aorta to increase the retroaortic apace and concomitantly performed extended left pulmonary artery reconstruction. This procedure obtains a more balanced distribution of the pulmonary blood flow, which is crucial to achieve good Fontan circulation.

Excellent Restoration of Left Ventricular Compliance After Prolonged Del Nido Single-Dose Cardioplegia in an In Vivo Piglet Model.

Del Nido cardioplegia (DN) is used in congenital heart surgery and recently in adults, a single dose has been administered. However, the tolerable ischemic time has not been established. The objective is to evaluate the left ventricular (LV) function recovery and accompanying biochemical and histologic markers to clarify the tolerable ischemic time in an in vivo cardiopulmonary bypass (CPB) piglet model. Twenty-one piglets were subjected to either 90 minutes (with or without topical cooling; TC) or 120 minutes (with TC) of global ischemia induced by single-dose DN, while the other 7 served as the control group (CPB only). The CPB temperature was established with a perfusion temperature of 30°C. The LV function recovery was assessed by the percent change in end-systolic elastance (Ees) and the end-diastolic pressure-volume relationship (EDPVR). Creatine kinase-MB (CK-MB) levels and the mitochondrial score were also assessed. LV contractility assessed by %Ees after 90 and 120 minutes of ischemia (89.3 ± 20.6% and 57.9 ± 17.8%) was lower compared with the control group (122.6 ± 35.8%, P = 0.001). Conversely, LV compliance assessed by %EDPVR was preserved in both groups (102.7 ± 28.2% and 88.5 ± 24.0%), which was comparable to the control group (105.8 ± 36.9%, P = 0.531). There was no change in LV contractility after 90 minutes of ischemia with or without TC (89.3 ± 20.6% or 84.8 ± 16.2%, P = 0.657), whereas LV compliance was lower but not statistically different without TC (102.7 ± 28.2% vs 78.0 ± 38.9%). CK-MB and the mitochondrial score were equivalent between all groups. The proposed single-dose ischemic time for redosing is 90 minutes using TC.

Effect of Long-term Administration of Prostaglandin E1 on Morphologic Changes in Ductus Arteriosus.

BACKGROUND: To improve survival of patients with hypoplastic left heart syndrome, combination therapy with bilateral pulmonary artery banding and prostaglandin E1 (PGE1)-mediated ductal patency was developed as an alternative for high-risk neonates in Japan. However, the effect of long-term PGE1 administration on ductus arteriosus remains unclear. Synchrotron radiation-based X-ray phase-contrast tomography (XPCT) enables clear visualization of soft tissues at an approximate spatial resolution of 12.5 µm. We aimed to investigate morphologic changes in ductus arteriosus after long-term PGE1 infusion using XPCT. METHODS: Seventeen ductus arteriosus tissue samples from patients with hypoplastic left heart syndrome were obtained during the Norwood procedure. The median duration of lipo-prostaglandin E1 (lipo-PGE1) administration was 48 days (range, 3 to 123). Structural analysis of ductus arteriosus was performed and compared with conventional histologic analysis. RESULTS: The XPCT was successfully applied to quantitative measurements of ductal media. Significant correlation was found between the duration of lipo-PGE1 infusion and mass density of ductal media (R = 0.723, P = .001). The duration of lipo-PGE1 administration was positively correlated with elastic fiber staining (R = 0.799, P < .001) and negatively correlated with smooth muscle formation (R = -0.83, P < .001). No significant increase in intimal cushion formation was found after long-term lipo-PGE1 administration. Expression of ductus arteriosus dominant PGE2-receptor EP4 almost disappeared in specimens when lipo-PGE1 was administered over 3 days. CONCLUSIONS: Disorganized elastogenesis and little intimal cushion formation after long-term lipo-PGE1 administration suggest that ductus arteriosus remodeled to the elastic artery phenotype. Because EP4 was downregulated and ductus arteriosus exhibited elastic characteristics, the dosage of lipo-PGE1 might be decreased after a definite administration period.

A Devised Option of Neonatal Palliation for Compromised Tetralogy of Fallot with Absent Pulmonary Valve Syndrome.

Neonatal primary repair of tetralogy of Fallot (TOF) with absent pulmonary valve (APV) syndrome is associated with high mortality rates. Our plan involves a staged repair that avoids one-stage intracardiac repair (ICR), with a first palliation that closes the main pulmonary orifice using an expanded polytetrafluoroethylene (ePTFE) patch, pulmonary arterioplication, and an adjustable Blalock-Taussig (BT) shunt. This strategy was used for a neonatal case with TOF/APV syndrome with hypoplastic left ventricle (LV). There was evidence of subsequent progressive increase in the LV size, and bronchial compression was relieved and an ICR was performed successfully at 9 months of age.

A 4-year-old girl with giant left atrial diverticulum resulting in severe mitral regurgitation.

Left atrial diverticulum is rare in a pediatric patient. A 4-year-old girl underwent a left atrial plication concomitant with mitral valve replacement, and early postoperative course was uneventful. This patient has remained asymptomatic with no evidence of recurrent diverticular formation after 9 months of follow-up.

Synergistic effects of remote perconditioning with terminal blood cardioplegia in an in vivo piglet model.

OBJECTIVES: This study tested the hypothesis that remote perconditioning offers effective and synergistic cardioprotection to terminal warm blood cardioplegia for prompt ventricular recovery after prolonged cardioplegic arrest in an in vivo piglet model. METHODS: Twenty-four piglets were subjected to 120 min of single-dose cardioplegic arrest and were divided into 4 groups according to the mode of reperfusion: control (simple aortic unclamp), remote perconditioning, terminal warm blood cardioplegia or remote perconditioning + terminal warm blood cardioplegia; remote perconditioning (4 cycles of 5-min ischaemia-reperfusion of the lower limb) was applied prior to aortic unclamping. Left ventricular systolic and diastolic functions were assessed by pressure-volume loop analysis at baseline and after 60 min of reperfusion. Biochemical injury was evaluated by plasma troponin T level. RESULTS: The control group showed decreased end-systolic elastance, preload recruitable stroke work and inverse of end-diastolic pressure-volume relationship of 51.3 ± 14.0%, 46.1 ± 22.5% and 34.8 ± 14.9%, respectively. Percentage recovery of end-systolic elastance and preload recruitable stroke work were significantly better with terminal warm blood cardioplegia (with or without remote perconditioning) (end-systolic elastance: 95% confidence interval, 38.6-84.1; preload recruitable stroke work: 95% confidence interval, 0.4-54.3). Percentage recovery of inverse of end-diastolic pressure-volume relationship was significantly better in the remote perconditioning groups (with or without terminal warm blood cardioplegia) (95% confidence interval, 1.6-41.6). No synergistic effects of remote perconditioning and terminal warm blood cardioplegia on troponin T release were noted. CONCLUSIONS: Remote perconditioning offers promising synergistic cardioprotection to terminal warm blood cardioplegia, implicating potential clinical benefit by contributing to prompt left ventricular functional recovery during paediatric open-heart surgery.

Three Dimensional Visualization of Human Cardiac Conduction Tissue in Whole Heart Specimens by High-Resolution Phase-Contrast CT Imaging Using Synchrotron Radiation.

BACKGROUND: The feasibility of synchrotron radiation-based phase-contrast computed tomography (PCCT) for visualization of the atrioventricular (AV) conduction axis in human whole heart specimens was tested using four postmortem structurally normal newborn hearts obtained at autopsy. METHODS: A PCCT imaging system at the beamline BL20B2 in a SPring-8 synchrotron radiation facility was used. The PCCT imaging of the conduction system was performed with "virtual" slicing of the three-dimensional reconstructed images. For histological verification, specimens were cut into planes similar to the PCCT images, then cut into 5-µm serial sections and stained with Masson's trichrome. RESULTS: In PCCT images of all four of the whole hearts of newborns, the AV conduction axis was distinguished as a low-density structure, which was serially traceable from the compact node to the penetrating bundle within the central fibrous body, and to the branching bundle into the left and right bundle branches. This was verified by histological serial sectioning. CONCLUSION: This is the first demonstration that visualization of the AV conduction axis within human whole heart specimens is feasible with PCCT.