Effect of inflow cannula side-hole number on drainage flow characteristics: flow dynamic analysis using numerical simulation.

BACKGROUND: Venous drainage in cardiopulmonary bypass is a very important factor for safe cardiac surgery. However, the ideal shape of venous drainage cannula has not been determined. In the present study, we evaluated the effect of side-hole number under fixed total area and venous drainage flow to elucidate the effect of increasing the side-hole numbers. METHOD: Computed simulation of venous drainage was performed. Cannulas were divided into six models: an end-hole model (EH) and models containing four (4SH), six (6SH), eight (8SH), 10 (10SH) or 12 side-holes (12SH). Total orifice area of the side-holes was fixed to 120 mm2 on each side-hole cannula. The end-hole orifice area was 36.3 mm2. The total area of the side-holes was kept constant when the number of side-holes was increased. RESULT: The mean venous drainage flow rate of the EH, 4SH, 6SH, 8SH, 10SH and 12SH was 2.57, 2.52, 2.51, 2.50, 2.49, 2.41 L/min, respectively. The mean flow rate decreased in accordance with the increased number of side-holes. CONCLUSION: We speculate that flow separation at the most proximal site of the side-hole induces stagnation of flow and induces energy loss. This flow separation may hamper the main stream from the end-hole inlet, which is most effective with low shear stress. The EH cannula was associated with the best flow rate and flow profile. However, by increasing side-hole numbers, flow separation occurs on each side-hole, resulting in more energy loss than the EH cannula and flow rate reduction.

Numerical simulation of blood flow in femoral perfusion: comparison between side-armed femoral artery perfusion and direct femoral artery perfusion.

Computational numerical analysis was performed to elucidate the flow dynamics of femoral artery perfusion. Numerical simulation of blood flow was performed from the right femoral artery in an aortic model. An incompressible Navier-Stokes equation and continuity equation were solved using computed flow dynamics software. Three different perfusion models were analyzed: a 4.0-mm cannula (outer diameter 15 French size), a 5.2-mm cannula (18 French size) and an 8-mm prosthetic graft. The cannula was inserted parallel to the femoral artery, while the graft was anastomosed perpendicular to the femoral artery. Shear stress was highest with the 4-mm cannula (172 Pa) followed by the graft (127 Pa) and the 5.2-mm cannula (99 Pa). The cannula exit velocity was high, even when the 5.2-mm cannula was used. Although side-armed perfusion with an 8-mm graft generated a high shear stress area near the point of anastomosis, flow velocity at the external iliac artery was decreased. The jet speed decreased due to the Coanda effect caused by the recirculation behind sudden expansion of diameter, and the flow velocity maintains a constant speed after the reattachment length of the flow. This study showed that iliac artery shear stress was lower with the 5.2-mm cannula than with the 4-mm cannula when used for femoral perfusion. Side-armed graft perfusion generates a high shear stress area around the anastomotic site, but flow velocity in the iliac artery is slower in the graft model than in the 5.2-mm cannula model.

Hydrodynamic evaluation of a new dispersive aortic cannula (Stealthflow).

The aim of this study was to evaluate flow from a new dispersive aortic cannula (Stealthflow) in the aortic arch using flow visualization methods. Particle image velocimetry was used to analyze flow dynamics in the mock aortic model. Flow patterns, velocity distribution, and streamlines with different shape cannulas were evaluated in a glass aortic arch model. We compared flow parameters in two different dispersive type cannulas: the Stealthflow and the Soft-flow cannula. A large vortex and regurgitant flow were observed in the aortic arch with both cannulas. With the Stealthflow cannula, a high-velocity area with a maximum velocity of 0.68 m/s appeared on the ostium of the cannula in the longitudinal plane. With the Soft-flow cannula, 'multiple jet streams, each with a velocity less than 0.60 m/s, were observed at the cannula outlet. Regurgitant flow from the cannula to the brachiocephalic artery and to the ascending aorta on the greater curvature was specific to the Soft-flow cannula. The degree of regurgitation on the same site was lower with the Stealthflow cannula than with the Soft-flow cannula. The Stealthflow cannula has similar flow properties to those of the Soft-flow cannula according to glass aortic model analysis. It generates gentle flow in the aortic arch and slow flow around the ostia of the aortic arch vessels. The Stealthflow cannula is as effective as the Soft-flow cannula. Care must be taken when the patient has thick atheromatous plaque or frail atheroma on the lesser curvature of the aortic arch.

Novel Method of Assessing Ascending Aorta with a Stenotic Bicuspid Aortic Valve.

BACKGROUND AND AIM OF THE STUDY: Patients with bicuspid aortic valve (BAV) have an increased risk of serious aortic complications such as aortic dissection, rupture and dilatation of the ascending aorta. Previous findings have suggested that ascending aortic dilatation with a BAV has a typical asymmetric configuration at the right-anterior aspect of the aorta. The study aim was to quantify asymmetric configurations of the aorta using a three-dimensional (3D) reconstruction tool. METHODS: A retrospective review was conducted of 52 patients (27 males, 25 females; mean age 69 ? 9 years) with aortic stenosis who presented with ascending aortic dilatation defined as an aortic diameter >35 mm. Of these patients, 24 (46%) had a BAV and 28 (54%) had a tricuspid aortic valve (TAV). A patient-specific 3D thoracic aortic model was reconstructed from computed tomography (CT) data. Three-dimensional centerlines were automatically calculated. The size of the ascending aorta was determined by calculating the cross-sectional area (in mm2) of the vertical section against the centerline. The symmetry of the dilated aorta was evaluated as the ellipticity of the maximum vertical section of the ascending aorta. The size and symmetry of the ascending aorta, and background factors including pressure gradient, aortic valve area, degree of regurgitation, ejection fraction and cardiovascular risk factors, were compared between the BAV and TAV groups. RESULTS: Only age differed significantly between the groups (p = 0.003). The size and ellipticity of the ascending aorta and the maximum cross-sectional area of the aortic arch were significantly greater in the BAV group (p = 0 .001 and p = 0.004, respectively). CONCLUSION: The ascending aorta assessed using Mimics 3D reconstruction software was frequently asymmetrically dilated in stenotic BAV, and the expansion progressed to the aortic arch. It is believed that calculating the ellipticity of the vertical section against the centerline offers an innovative means of quantifying aortic symmetry in three dimensions.

[Surgery for Infective Endocarditis Involving Valve Annulus].

Surgical treatment for isolated infective endocarditis( IE) has been improving over the last 2 decades. However, surgery for complicated IE such as disruption of paravalvular structure remains a challenge. The aim of this retrospective study is to evaluate our surgical results for IE with paravalvular structural disruption. From January 2002 to March 2015, we performed cardiac surgery for 68 patients who suffered from IE. Thirteen patients had paravalvular abscess and fistula. Valve disruptions were seen in aortic valve in 10 patients [2 fistulas from right coronary cuspid to right atrium or ventricle, 3 abscess formation from right coronary cuspid to interventricular septum, 1 abscess formation from left coronary cuspid to anterior mitral leaflet, 1 left ventricle to right atrium communication from non-coronary cuspid (NCC), 2 abscess formation under NCC and 1 circular annulas infection]. Mitral valve involvement was found in 2 patients [1 posterior mitral leaflet (PML) infection and submitral abscess infiltrating to annula calcification and 1 PML infection with submitral abscess]. One patient who had tricuspid valve involvement had giant vegetation from tricuspid to pulmonary valve through right ventricular outflow tract. Radical debridement of infected tissue and reconstruction using allograft, artificial valve and conduit were performed in all cases.

[Management of Infective Endocarditis with Neurological Complication].

Neurological complications in patients with infective endocarditis are frequent and mortality is higher in those with neurological complications than in those without. The spectrum of neurological complications includes cerebral infarction, intracranial hemorrhage, intracranial infectious aneurysm, transient ischemic attack (TIA), meningitis, encephalopathy and brain abscess. The appropriate timing of valve surgery following a cerebrovascular event remains controversial because cardiopulmonary bypass may exacerbate neurological deficits. Previous studies suggest delaying valve surgery for 2 to 4 weeks following embolic stroke and at least 4 weeks following hemorrhagic stroke however, urgent valve surgery may be needed depending on the hemodynamic state of the patient. In the event of intracranial infectious aneurysm, therapeutic management is not perfectly standardized. We retrospectively reviewed the surgical results of infective endocarditis patients with neurological complications. Current trends in surgical timing and therapeutic decision-making are discussed.

The effect of atmospheric pressure on ventricular assist device output.

The effect of cabin pressure change on the respiratory system during flight is well documented in the literature, but how the change in atmospheric pressure affects ventricular assist device (VAD) output flow has not been studied yet. The purpose of our study was to evaluate the change in VAD output using a mock circulatory system in a low-pressure chamber mimicking high altitude. Changes in output and driving pressure were measured during decompression from 1.0 to 0.7 atm and pressurization from 0.7 to 1.0 atm. Two driving systems were evaluated: the VCT system and the Mobart system. In the VCT system, output and driving pressure remained the same during decompression and pressurization. In the Mobart system, the output decreased as the atmospheric pressure dropped and recovered during pressurization. The lowest output was observed at 0.7 atm, which was 80% of the baseline driven by the Mobart system. Under a practical cabin pressure of 0.8 atm, the output driven by the Mobart system was 90% of the baseline. In the Mobart system, the output decreased as the atmospheric pressure dropped, and recovered during pressurization. However, the decrease in output was slight. In an environment where the atmospheric pressure changes, it is necessary to monitor the diaphragmatic motion of the blood pump and the driving air pressure, and to adjust the systolic:diastolic ratio as well as the positive and negative pressures in a VAD system.

Intimal sarcoma of the pulmonary artery--diagnostic challenge.

Pulmonary artery intimal sarcoma is a rare tumour and the diagnosis is often delayed. We report the case of a woman with a primary pulmonary artery intimal sarcoma who presented with massive pulmonary embolism. The definitive diagnosis was elucidated after the patient's death by autopsy specimen. We discuss the diagnosis and lessons learned from this case.

Inferior Vena Cava Filter-Induced Thrombosis: Filter Insertion Prior to Catheter-Directed Thrombolysis and Successful Double-Filter Retrieval after Prolonged Indwelling Time.

Extended inferior vena cava (IVC) filter implantation time increases the risk of complications in patients. Here we present the case of a 72-year-old woman with IVC filter-induced thrombosis who underwent catheter-directed thrombolysis with prophylactic IVC filter placement. Two IVC filters were successfully retrieved 70 and 1858 days post placement. The decision to insert an IVC filter should be carefully considered with appropriate indications and all filters should be removed after the risk of deep vein thrombosis has resolved.

Reimplantation of a Stenotic Inferior Mesenteric Artery for Chronic Visceral Artery Occlusion after Failed Bypass to the Superior Mesenteric Artery.

The patient was a 71-year-old man complaining of postprandial abdominal pain and weight loss. Computed tomography angiography showed occlusion of the superior mesenteric artery and the celiac axis. The inferior mesenteric artery, supplying the mesenteric circulation, was stenotic at its origin. The patient had portal vein thrombosis and was diagnosed as having antiphospholipid antibody syndrome. The reimplantation of the inferior mesenteric artery was successfully performed after failed bypass grafting to the superior mesenteric artery from the abdominal aorta.

Improved Outcomes for Ruptured Abdominal Aortic Aneurysms Using Integrated Management Involving Endovascular Clamping, Endovascular Replacement, and Open Abdominal Decompression.

Objective: Endovascular repair has become the treatment of choice for ruptured abdominal aortic aneurysms (RAAAs). To improve surgical outcomes, preoperative management is important. In 2011, we introduced integrated management, which involves endovascular aneurysm repair, stabilization of hemodynamics by endovascular clamping, and open abdominal decompression to address abdominal compartment syndrome (ACS). Methods: To evaluate the efficacy of this management strategy, 62 patients who had undergone emergency surgery for an RAAA were analyzed retrospectively: group A (n=39), where an old strategy was used, and group B (n=23), where integrated management was introduced. Patient characteristics and 30-day mortality rates were compared between the two groups. Results: The average patient age was 67.7 years and 74.7 years for groups A and B, respectively (P=0.032). Group B patients required more frequent use of vasopressors (P=0.035). Other patient characteristics did not differ between the two groups. The duration of surgery was significantly shorter in group B than in group A (P=0.001). The total amount of transfused blood did not differ between the two groups. No patients showed symptoms of ACS. Early mortality rates were 12.8% and 8.7% in groups A and B, respectively. The number of wound infections was significantly fewer in group B than in group A. Conclusion: Although group B patients were significantly older and had a higher rate of vasopressor use, early mortality was improved in both groups. Morbidity was significantly better in group B with respect to the duration of surgery and number of wound infections than in group A.

Surgical Management of Mycotic Aortic Aneurysms.

Purpose: A mycotic aneurysm is an uncommon disease associated with a high mortality rate when managed surgically. This study reviewed our experiences in the surgical management of mycotic aortic aneurysms. Methods: In total, 26 patients who underwent surgery for a mycotic aneurysm were retrospectively reviewed. The mycotic aneurysms involved the thoracic aorta in 9 patients, the thoracoabdominal aorta in 4 patients, and the abdominal aorta in 13 patients. An overt aortic rupture in the mediastinum or retroperitoneal space was detected in 4 patients. Patients were classified into one of two groups, febrile or afebrile, and background characteristics, surgical intervention, and early and late mortalities were all compared. Results: There were 19 patients who underwent open surgery, and 7 patients underwent endovascular repair. No significant differences in the clinical characteristics were found between the two groups; however, the incidence of postoperative complications was significantly higher in the febrile group than in the afebrile group (P=0.024). Overall mortality was 15.4% (4/26), and 30-day mortality was 7.7% (2/26). Conclusion: Although febrile patients had a higher incidence of postoperative complications, surgical mortality from a mycotic aneurysm was within an acceptable range. Each patient should be thoroughly evaluated and treated on a case-by-case basis, using conventional open repair, endovascular repair, or a combination of both approaches.

Successful Resuscitation of a Patient with Life-Threatening Metabolic Acidosis by Hemodialysis: A Case of Ethylene Glycol Intoxication.

BACKGROUND: Ethylene glycol intoxication causes severe metabolic acidosis and acute kidney injury. Fomepizole has become available as its antidote. Nevertheless, a prompt diagnosis is not easy because patients are often unconscious. Here we present a case of ethylene glycol intoxication who successfully recovered with prompt hemodialysis. CASE PRESENTATION: A 52-year-old Japanese male was admitted to a local hospital due to suspected food poisoning. The patient presented with nausea and vomiting, but his condition rapidly deteriorated, with worsening conscious level, respiratory distress requiring mechanical ventilation, hypotension, and severe acute kidney injury. He was transferred to the university hospital; hemodialysis was initiated because of hyperkalemia and severe metabolic acidosis. On recovering consciousness, he admitted having ingested antifreeze solution. Thirty-seven days after admission, the patient was discharged without requiring HD. CONCLUSIONS: We reported a case of ethylene glycol intoxication who presented with a life-threatening metabolic acidosis. In a state of severe circulatory shock requiring catecholamines, hemodialysis should be avoided, and continuous hemodiafiltration may be a preferred approach. However, one should be aware of the possibility of intoxication by unknown causes, and hemodialysis could be life-saving with its superior ability to remove toxic materials in such cases.

Management of Pulmonary Thromboembolism Based on Severity and Vulnerability to Thrombolysis.

Background: The incidence of pulmonary thromboembolism has been considered rare in Japan. However, its occurrence has been increasing because of westernized lifestyle and diet, increased diagnostic technique, and recognition of this disease. Method: Between January 2003 and September 2014, 179 patients were treated for pulmonary thromboembolism. We classified these patients into 3 groups; Massive (n=35), Sub-massive (n=29) and Nonmassive (n=115) and retrospectively reviewed the treatment options and the outcome. Results: Percutaneous cardiopulmonary support (PCPS) was applied for patients with hemodynamic instability and IVC filter was inserted if there was proximal DVT. In non-massive group (n=115), 95.7% of the patient underwent anticoagulant therapy and 47.0% of the patients received IVC filter. In submassive group (n=29), 48.3% of the patient received thrombolytic therapy and 93.1% of the patient underwent IVC filter insertion. Surgical pulmonary embolectomy was performed in 3 patients who had high risk of thrombolytic therapy in submassive group. There was no death in this group. In massive group, 4 patients who had cardiogenic shock died in acute phase. PCPS was applied in 5 patients, pulmonary embolectomy was performed in 13 patients, thrombolytic therapy was performed in 4 patients and 13 patients underwent anticoagulant therapy alone. There were 7 deaths (20.0%) in this group. Conclusions: In submassive group, treatment should be decided depending on the bleeding risk. In massive group, pulmonary embolectomy was effective. (This is a translation of Jpn J Phlebol 2016; 27: 53-59.).

Management of deep vein thrombosis and pulmonary embolism (venous thromboembolism) during pregnancy.

PURPOSE: The risk of venous thromboembolism (VTE) is high during pregnancy. Although most patients with VTE are safely treated via medications, the optimal treatment for massive pulmonary embolism remains controversial. To evaluate the safety and efficacy of VTE management during pregnancy, we report our single center experience of treating VTE in pregnant women. METHODS: Case records were retrospectively reviewed from seven patients who underwent treatment for venous thromboembolism between 2002 and 2014. RESULTS: Mean gestational time was 28 ± 6.2 weeks. Four patients with deep vein thrombosis were treated medically, and they all had vaginal delivery at full term without hemorrhagic complication. Three patients with massive pulmonary embolism underwent surgical embolectomy. Two of these three patients underwent cesarean delivery at 28 and 29 weeks respectively. There was no maternal death, but one fetal death occurred during surgical embolectomy. CONCLUSION: VTE during pregnant women is safely managed by anticoagulant therapy. Massive pulmonary embolism during pregnancy can be managed safely by surgical embolectomy using cardiopulmonary bypass, but the rate of fetal loss remains high.

Acute limb ischemia: contemporary approach.

Acute limb ischemia is a critical condition with high mortality and morbidity even after surgical or endovascular intervention. Early recognition is important, but a delayed presentation is not uncommon. Viability of the limb is assessed by motor and sensory function and with interrogating Doppler flow signals in pedal arteries and popliteal veins as categorized by Rutherford. Category IIa indicates mild-to-moderate threat to limb salvage over a time frame without revascularization. Limb ischemia is critical without prompt revascularization in category IIb. Because the risk of reperfusion injury is high in this group of patients, perioperative management is important. In category III, reperfusion is not indicated except for embolism within several hours of onset. Intimal injury should be avoided by careful tactile control of a balloon with a smaller size catheter and under radiographic monitoring. Adjunctive treatment with catheter-directed thrombolysis or bypass surgery is sometimes necessary. Endovascular treatment is a promising option for thrombotic occlusion of an atherosclerotic artery. Ischemia-reperfusion injury is a serious problem. Controlled reperfusion with low-pressure perfusion at a reduced temperature and use of a leukocyte filter should be considered. The initial reperfusate is hyperosmolar, hypocalcemic, slightly alkaline, and contains free radical scavengers such as allopurinol. Immediate hemodialysis is necessary for acute renal injury caused by myoglobinemia. Compartment syndrome should be managed with assessment of intra-compartment pressure and fasciotomy.

Management of infective endocarditis with cerebral complications.

PURPOSE: Management of patients with infective endocarditis complicated by neurological deficits is challenging. No clear management guidelines have been defined, and the timing of surgery remains controversial. The purpose of this study was to evaluate our management algorithm. METHODS: Thirty-eight adult patients with left-sided infective endocarditis undergoing valve surgery were analyzed. Before the operation, enhanced brain computed tomography (CT) was performed to rule out a cerebral complication. Pre and postoperative data were retrospectively reviewed to clarify whether our algorithm was effective. Sixteen patients having neurological complication (CVC group) were compared with 22 patients without neurological complication. RESULTS: Age, sex, New York Heart Association (NYHA) functional class, affected valve and pathogens were not different between two groups. Mean interval from the onset of neurological dysfunction to cardiac operation was 27.8 ± 27.8 days (median 23 days). Of the 16 CVC group patients, 12 experienced cerebral infarction. Mass effects were seen in 3 patients, with 1 of these 3 patients died following aneurysm rupture. Mycotic aneurysm was detected in 4 patients, with 3 undergoing successful staged operations. Mortality and postoperative neurological exacerbation in CVC group was 6.3% (1 patient). Most patients who fulfilled the algorithm showed good outcomes. CONCLUSIONS: Our suggested management algorithm for infective endocarditis appears effective.

Shaggy and calcified aorta: surgical implications.

Atheroembolism is an emerging problem in cardiovascular surgery, especially in elderly patients. Severe atherosclerosis of the thoracic aorta usually reflects systemic atherosclerosis. Aggressive preoperative and intraoperative evaluation of the aorta using enhanced CT, transesophageal echocardiography and epiaortic ultrasound is important in elderly patients as well as those with systemic atherosclerosis. To prevent atheroembolism, it is important to select an adequate arterial perfusion site and to avoid touching the diseased aorta until circulatory arrest. In atherosclerotic aortic arch aneurysm, central cannulation under ultrasound guidance and directing the dispersive cannula toward the aortic root is a simple and effective perfusion strategy. Axillary perfusion is useful as an alternative to central cannulation in atherosclerotic aortic disease, but special care is necessary to avoid complications when the patient has a small axillary artery or flail atheroma around the arch vessels. In femoral artery perfusion, retrograde perfusion may induce paradoxical cerebral embolism, but the incidence of stroke is comparable with axillary perfusion when there is adequate preoperative screening using transesophageal echography. Circulatory arrest with/without cerebral perfusion is another important strategy when the aorta has severe atherosclerosis. Recent literature has shown that mild hypothermia may be safe for anterior cerebral perfusion during circulatory arrest, but optimal flow rates and time limitations are unknown. A simple calcified aorta called "porcelain aorta" may be managed by circulatory arrest, local debridement and the clamp method. Several surgical options are proposed for this clinical entity but their use will diminish in the future because of transcatheter valve replacement.

Screw in the aorta: minimally invasive graft replacement for chronic aortic erosion by spinal instrument.

Intra-and early post-operative aortic injury by pedicle screw is not a rare complication in orthopedic surgery, but aortic penetration by a screw head over a long time period is considered as an uncommon case. There are various surgical management options for thoracic aortic injury caused by malpositioned spinal instruments. We report a case of a patient who underwent minimally invasive graft replacement of the descending thoracic artery for pedicle screw penetration.

Leiomyosarcoma of the external iliac vein.

Leiomyosarcoma of the iliac vein is an uncommon tumor. We report a case of a 63-year-old Japanese woman with leiomyosarcoma of the right external iliac vein. The patient complained of right inguinal pain and swelling. Computed tomography demonstrated a mass surrounding the right external iliac artery and vein. Metastases in the lungs and liver were found. Complete resection of the tumor along with the involved vessels was performed. Polytetrafluoroethylene grafts were used to reconstruct the vessels. Pathological examination revealed leiomyosarcoma of the external iliac vein. Although the prognosis of leiomyosarcoma is poor, en bloc tumor resection is the treatment of choice.