Norihiko Oka

Key success factors for thoracic endovascular aortic repair for non-acute Stanford type B aortic dissection †

OBJECTIVES We aimed to determine the key factors associated with successful early and late outcomes after thoracic endovascular aortic repair (TEVAR) for non-acute Stanford type B aortic dissection at our institution. METHODS Inpatient and outpatient records were retrospectively reviewed. Patients operated on within 14 days after the onset of acute aortic dissection and those with rupture or malperfusion were excluded. RESULTS Forty-five patients (mean age, 55.5 ± 13.1 years; 23-79 years) underwent 53 TEVAR operations for non-acute Stanford type B aortic dissection between 1998 and 2012. Thirty-four patients had a patent false lumen and 19 had an ulcer-like projection (ULP). No early mortality was observed. At late follow-up (7.5 ± 3.9 years) of the 45 patients, survival after the initial TEVAR was 100, 86 and 63%; freedom from aortic reintervention was 87, 73 and 59%; and freedom from open aortic surgery was 89, 84 and 73%, at 1, 5 and 10 years, respectively. Of 15 late deaths, 2 were due to aortic rupture and 2 were operative deaths associated with aortic surgery. Of the 34 patients with patent false lumens before TEVAR, 25 had their descending false lumens thrombosed; of these 25, 16 had remodelling of the descending aorta; and of these 16, 4 had complete obliteration of the false lumen of the entire aorta. By bivariate analysis, the site of the primary entry and age were significantly associated with thrombosis of the descending false lumen, maximum aortic diameter was associated with remodelling of the descending aorta, and absence of abdominal branches arising from the false lumen was associated with complete obliteration of the false lumen of the entire aorta. CONCLUSIONS The early results of TEVAR for non-acute Stanford type B aortic dissection were favourable. However, for cases with patent false lumens, complete obliteration of the false lumen of the entire aorta was difficult to achieve. Absence of the primary entry at the outer curvature of the distal aortic arch, younger age, small aortic diameter and absence of the abdominal aortic branches arising from the false lumen were the key success factors.

Effect of the neutrophil elastase inhibitor sivelestat on perioperative inflammatory response after pediatric heart surgery with cardiopulmonary bypass: a prospective randomized study.

Cardiopulmonary bypass (CPB) elicits a systemic inflammatory response. The neutrophil elastase inhibitor sivelestat is known to suppress this systemic inflammatory response, which can eventually result in acute organ failure. The prophylactic effect of sivelestat on acute lung injury, especially in pediatric cardiac surgery, remains unclear. This prospective double-blind, randomized study evaluated the perioperative prophylactic effect of sivelestat in patients undergoing elective pediatric open heart surgery with CPB. Thirty consecutive patients, weighing 5-10 kg and undergoing open heart surgery with CPB, were assigned to sivelestat (n = 15) or control (n = 15) groups. From CPB initiation to 24 h after surgery, patients in the sivelestat group received a continuous intravenous infusion of 0.2 mg/kg/h sivelestat, whereas patients in the control group received the same volume of 0.9% saline. Blood samples were collected, and levels of interleukin (IL)-6, IL-8, tumor necrosis factor alpha, polymorphonuclear elastase (PMN-E), C-reactive protein (CRP), as well as the white blood cell (WBC) count, platelet count, and neutrophil count (NC) were measured. PMN-E levels, IL-8 levels, WBC count, NC, and CRP levels were significantly lower, and platelet count was significantly higher in the sivelestat group, according to repeated two-way analysis of variance. The activated coagulation time was significantly shorter in the sivelestat group, similarly, blood loss was significantly less in the sivelestat group. In conclusion, Sivelestat attenuates perioperative inflammatory response and clinical outcomes in patients undergoing pediatric heart surgery with CPB.

Impact of the entry site on late outcome in acute Stanford type B aortic dissection

OBJECTIVES This study aimed to investigate whether the entry site of acute type B aortic dissection affects late outcomes. METHODS Inpatient and outpatient records were retrospectively reviewed. RESULTS We identified 224 cases of acute type B aortic dissection between 1998 and 2013. Of these 224 patients, 168 were men and the age was 64.2 ± 12.6 (range 23-94) years, from which 130 presented with the entry at a location downstream of the distal aortic arch, 67 with the entry at the outer curvature of the distal aortic arch and 27 with the entry at the inner curvature. At the initial presentation, 127 patients had descending false lumen thrombosis. The 30-day mortality rate was 2%, and 8% of patients had malperfusion. The entry at the outer curvature was associated with a higher risk of 30-day mortality. Patients with the entry at a location downstream were significantly older, and had a higher chance for primarily thrombosed descending false lumen and a lower risk of malperfusion. At follow-up (6.0 ± 4.1 years), the actuarial survival rates were 97, 83 and 60%, freedoms from open aortic surgery were 96, 91 and 86%, aortic intervention were 73, 66 and 63% and aortic events were 71, 60 and 52% at 1, 5 and 10 years, respectively. Multivariate logistic regression analysis revealed that the outer curvature entry and maximum aortic diameter were correlated with open aortic surgery, aortic intervention and aortic events. Of the 127 patients with primarily thrombosed false lumen, the outer curvature entry was significantly correlated with aortic events. CONCLUSIONS The primary entry at the outer curvature of the distal aortic arch, as well as the large aortic diameter, is associated with a higher risk of late open aortic surgery, aortic intervention and aortic events in acute type B aortic dissection. Thus, the entry site should be taken into consideration in the establishment of an appropriate treatment indication of type B aortic dissection.

Pulmonary Annulus Growth After the Modified Blalock-Taussig Shunt in Tetralogy of Fallot

BACKGROUND In tetralogy of Fallot (TOF), it is well known that postoperative pulmonary regurgitation reduces right ventricular function during long-term follow-up. Complete repair without a transannular patch should help avoid pulmonary regurgitation. Recently, primary complete repair has been preferred to the staged repair with use of a Blalock-Taussig shunt (BTS) even in neonates or small infants; however, little has been reported about the influence of a BTS on pulmonary annular growth. METHODS We examined 40 patients with TOF or double-outlet right ventricle with pulmonary stenosis. Twenty-one patients received a BTS before complete repair, whereas 19 patients underwent primary complete repair. Pulmonary annular size was measured by echocardiography before BTS, complete repair, or both, and ventricular volume was measured by cardiac catheterization. RESULTS There were no significant differences in complete repair age or body size between the groups. Pulmonary annulus sizes in the BTS group were smaller than those in the primary repair group (Z score, -5.1 ± 2.5 vs -3.7 ± 1.8). After the BTS, significant annular growth (Z score, -2.8 ± 2.1) was observed (p = 0.0028), with a significant increase in left ventricular end-diastolic volume (p = 0.015). When patients with severe pulmonary stenosis (Z score > -7.0) were excluded, pulmonary annular preservation at complete repair was achieved in 64.7% (11/17) of the BTS group and 36.8% (7/19) of the primary repair group (p = 0.088). CONCLUSIONS The BTS increased the pulmonary annular size and the left ventricular volume during the 6 months before complete repair, resulting in preservation of the pulmonary valve function.

Contributions of Respiration and Heartbeat to the Pulmonary Blood Flow in the Fontan Circulation

BACKGROUND In the Fontan circulation, driving forces with respiration, heartbeat, and lower limb muscle pump are relevant. However, the mechanics of these forces has not been proven, and their effects on the Fontan circulation remain unclear. METHODS We performed catheter examinations and measured pressure and flow velocity simultaneously in the bilateral pulmonary arteries of 12 Fontan patients 1 year after the operation. The pulmonary pressure and flow velocity data were decomposed into respiratory and heartbeat components by discrete Fourier analysis. We then calculated respiratory and cardiac wave intensity (WI) based on the respiratory and heartbeat components of pressure and flow velocity data. RESULTS Respiratory WI formed 2 negative peaks, a backward expansion wave during the inspiratory phase, and then a backward compression wave during the expiratory phase. In 2 phrenic nerve palsy cases and 1 case of a patient on a respirator, respiratory WI showed disturbed patterns and a negative pattern, respectively. Cardiac WI showed 2 or 4 negative peaks, the time phase of which matched that of the atrial contractions. CONCLUSIONS WI analysis elucidated that inspiration acts as a sucking driving force and increases the pulmonary blood flow in the Fontan circulation. Respiratory complications compromise efficiency in the Fontan circulation. It was also revealed that the pulmonary blood flow was mutually dammed up and sucked in by increases and decreases in atrial pressure.

Effect of Additional Preoperative Administration of the Neutrophil Elastase Inhibitor Sivelestat on Perioperative Inflammatory Response After Pediatric Heart Surgery With Cardiopulmonary Bypass

Cardiopulmonary bypass (CPB) elicits a systemic inflammatory response. Our previous reports revealed that prophylactic sivelestat administration at CPB initiation suppresses the postoperative acute inflammatory response due to CPB in pediatric cardiac surgery. The purpose of this study was to compare the effects of sivelestat administration before CPB and at CPB initiation in patients undergoing pediatric open-heart surgery. Twenty consecutive patients weighing 5-10 kg and undergoing ventricular septal defect closure with CPB were divided into pre-CPB (n = 10) and control (n = 10) groups. Patients in the pre-CPB group received a 24 h continuous intravenous infusion of 0.2 mg/kg/h sivelestat starting at the induction of anesthesia and an additional 0.1 mg/100 mL during CPB priming. Patients in the control group received a 24-h continuous intravenous infusion of 0.2 mg/kg/h sivelestat starting at the commencement of CPB. Blood samples were tested. Clinical variables including blood loss, water balance, systemic vascular resistance index, and the ratio between partial pressure of oxygen and fraction of inspired oxygen (P/F ratio) were assessed. White blood cell count and neutrophil count as well as C-reactive protein levels were significantly lower in the pre-CPB group according to repeated two-way analysis of variance, whereas platelet count was significantly higher. During CPB, mixed venous oxygen saturation remained significantly higher and lactate levels lower in the pre-CPB group. Postoperative alanine aminotransferase and blood urea nitrogen levels were significantly lower in the pre-CPB group than in the control group. The P/F ratio was significantly higher in the pre-CPB group than in the control group. Fluid load requirement was significantly lower in the pre-CPB group.Administration of sivelestat before CPB initiation is more effective than administration at initiation for the suppression of inflammatory responses due to CPB in pediatric open-heart surgery, with this effect being confirmed by clinical evidence.

Exploring energy loss by vector flow mapping in children with ventricular septal defect: Pathophysiologic significance ☆

BACKGROUND Vector flow mapping is a novel echocardiographic flow visualization method, and it has enabled us to quantitatively evaluate the energy loss in the left ventricle (intraventricular energy loss). Although intraventricular energy loss is assumed to be a part of left ventricular workload itself, it is unclear what this parameter actually represents. The aim of the present study was to elucidate the characteristics of intraventricular energy loss. METHODS We enrolled 26 consecutive children with ventricular septal defect (VSD). On echocardiography vector flow mapping, intraventricular energy loss was measured in the apical 3-chamber view. We measured peak energy loss and averaged energy loss in the diastolic and systolic phases, and subsequently compared these parameters with catheterization parameters and serum brain natrium peptide (BNP) level. RESULTS Diastolic, peak, and systolic energy loss were strongly and positively correlated with right ventricular systolic pressure (r=0.76, 0.68, and 0.56, p<0.0001, = 0.0001, and 0.0029, respectively) and right ventricular end diastolic pressure (r=0.55, 0.49, and 0.49, p=0.0038, 0.0120, and 0.0111, respectively). In addition, diastolic, peak, and systolic energy loss were significantly correlated with BNP (r=0.75, 0.69 and 0.49, p<0.0001, < 0.0001, and=0.0116, respectively). CONCLUSIONS In children with VSD, elevated right ventricular pressure is one of the factors that increase energy loss in the left ventricle. The results of the present study encourage further studies in other study populations to elucidate the characteristics of intraventricular energy loss for its possible clinical application.

Synchronization of the Flow and Pressure Waves Obtained With Non-Simultaneous Multipoint Measurements

The use of measured data as boundary conditions renders hemodynamic simulations more patient-specific. However, synchronized acquisition of data at multiple locations is often difficult in clinical practice. This study proposes a method for resynchronizing measured data for use as boundary conditions for flow simulations using frequency analyses, and discusses the optimal cut-off frequency for differentiating cardiac and respiratory variation in hemodynamic data during resynchronization. To demonstrate the utility of the method, a Fontan circulation, which is the final palliative result with single-ventricle physiology, was used. The results suggest that it is optimal to set a cut-off frequency that gives a local minimum in the power spectrum that is slightly lower than the peak frequency of the heartbeat. Additionally, the total energy loss depended on the cut-off frequency, although the overall flow patterns appeared to be similar. The method is applicable to cardiovascular systems other than the Fontan circulation, where hemodynamic data with multifactorial fluctuations are required at various locations but simultaneous measurements are not possible.

Optimal Graft Size of Modified Blalock-Taussig Shunt for Biventricular Circulation in Neonates and Small Infants

The modified Blalock-Taussig shunt (mBTS) is one of the most important palliative procedures in congenital heart surgery. However, in neonates and small infants, operative mortality and morbidity due to excessive pulmonary blood flow or shunt failure remains high. In this study, a small shunt graft (3.0-mm diameter) was estimated to determine the optimal shunt graft size of BTS as an initial palliation for ultimate biventricular circulation. Eighteen patients weighing an average 3.5 kg who underwent mBTS from July 2004 to January 2013 at our institute were reviewed. We divided the study cohort into two groups: group S (n = 10) included patients with 3.0-mm diameter shunt grafts, and group L (n = 8) included patients with 3.5-mm diameter shunt grafts. There were no hospital deaths or shunt occlusion in either group. One group L patient (12.5%) had cardiogenic shock due to excessive pulmonary blood flow. There were no differences in postoperative arterial oxygen saturation (SaO2) between the groups. There were no differences in body weight at intracardiac repair (ICR) between the groups. During the interstage to ICR, body weight gain was significantly greater in group S than in group L (P = 0.008). The small shunt graft (3.0-mm diameter) in BTS was safe, provided adequate pulmonary blood flow, and led to significant weight gain between mBTS and ICR for ultimate biventricular circulation in neonates and small infants with low body weight.

Surgical strategy for aortic arch reconstruction after the Norwood procedure based on numerical flow analysis

OBJECTIVES Inefficient aortic flow after the Norwood procedure is known to lead to the deterioration of ventricular function due to an increased cardiac workload. To prevent the progression of aortic arch obstruction, arch reconstruction concomitant with second-stage surgery is recommended. The aim of this study was to determine the indications for reconstruction based on numerical simulation and to reveal the morphology that affects the haemodynamic parameters. METHODS Fifteen patients who underwent the Norwood procedure or arch repair and Damus-Kaye-Stansel anastomosis were enrolled. The pressure gradient in aortic arch was 1.6 ± 3.9 mmHg (ranged from 0 to 12 mmHg) on catheter examination. Six patients who had prominent turbulent flow accompanied with a large flow energy loss index greater than 40 mW/m2 and high wall shear stress greater than 100 Pa underwent arch reconstruction. RESULTS After arch reconstruction, the energy loss index significantly decreased from 88.5 ± 50.0 mW/m2 to 23.1 ± 10.4 mW/m2 (P = 0.026) and wall shear stress significantly decreased from 194.5 ± 87.4 Pa to 60.3 ± 40.5 Pa (P = 0.0062). There were 3 late deaths due to heart failure caused by progressive atrioventricular valve regurgitation during the follow-up period (60 months). The systemic ventricular function was preserved in the remaining patients without any pressure gradients in the arch. CONCLUSIONS Determining the surgical strategy for arch reconstruction based on numerical flow analysis may effectively reduce the ventricular load even if no stenosis or pressure gradients are observed on catheter examination or echocardiography.