Ken-ichi Imasaka

Impacts of pulsatile systemic circulation on endothelium-derived nitric oxide release in anesthetized dogs

BACKGROUND The effects of pulsatile flow on endothelium-derived nitric oxide-mediated vasodilation are not fully elucidated in an in vivo model. METHODS A left ventricular assist device was established in 10 anesthetized dogs with a centrifugal pump and an air-driven pneumatic pump. The systemic circulation was subjected to step changes in the frequency of pulse (0, 30, 60, and 120 bpm with a fixed pulse pressure of 50 mm Hg), and in the amplitude of pulse (0, 20, and 50 mm Hg with a fixed pulse rate of 120 bpm). Hemodynamic variables and calculated total systemic vascular resistance were compared before and after the administration of N(G)-Nitro-L-arginine Methyl Ester (L-NAME) (20 mg/kg). Plasma NO2-/NO3- concentration levels were also measured. RESULTS Total systemic vascular resistance significantly decreased while plasma NO2-/No3- concentration increased in response to the rise in both pulse rate and pulse pressure. However, L-NAME significantly diminished these effects of pulsatile flow. CONCLUSIONS Both the frequency and the amplitude of pulse wave in the systemic circulation are significant independent stimuli for endothelium-derived nitric oxide-mediated vasodilation in vivo.

Obstructive carotid and/or intracranial artery disease rarely affects the incidence of haemodynamic ischaemic stroke during cardiac surgery: a study on brain perfusion single-photon emission computed tomography with acetazolamide

OBJECTIVES Ischaemic stroke is a major complication of cardiac surgery. The optimal strategies for operating on patients with obstructive carotid and/or intracranial artery disease (CIAD) are controversial. We aimed to clarify whether single-photon emission computed tomography (SPECT) with acetazolamide, to quantify the cerebral perfusion reserve, could predict the risk of haemodynamic ischaemic stroke during cardiac surgery. METHODS The incidence of stroke related to obstructive CIAD and the corresponding autoregulatory reserve were prospectively assessed in 514 consecutive patients who underwent elective cardiac surgery with cardiopulmonary bypass (n = 484) and off-pump coronary artery bypass grafting (n = 30) between 2009 and 2013. Preoperative cerebral blood flow and its reactivity to acetazolamide were quantitatively determined in patients (n = 88) with obstructive CIAD, diagnosed by carotid ultrasonography and/or magnetic resonance angiography. RESULTS An impaired cerebral perfusion reserve was identified in 1 (1.1%) of the 88 patients. This patient underwent prophylactic superficial temporal artery to middle cerebral artery anastomosis 1 month before coronary artery bypass surgery. Subsequently, the patient underwent conventional coronary artery bypass surgery, without experiencing perioperative stroke. Seven (1.4%) patients died in-hospital mortality and 5 (1.0%) experienced perioperative stroke. However, no patients experienced perioperative haemodynamic ischaemic stroke. CONCLUSIONS It is unusual for CIAD to affect the incidence of haemodynamic ischaemic stroke during cardiac surgery. Brain perfusion SPECT with acetazolamide is effective for narrowing down patients at high risk of ischaemic stroke during cardiac surgery. Meanwhile, the application of brain perfusion single-photon emission tomography should be confined only to patients with obstructive CIAD because it is an expensive examination tool.

The impact of carotid or intracranial atherosclerosis on perioperative stroke in patients undergoing open aortic arch surgery

Objectives: This study aimed to clarify the impact of carotid or intracranial atherosclerosis on perioperative stroke in patients undergoing open aortic arch surgery. Methods: Between 2008 and 2015, 200 consecutive patients underwent elective aortic arch surgery with selective antegrade cerebral perfusion and moderate hypothermic circulatory arrest. Nonselective screening for carotid or intracranial atherosclerosis was performed using carotid ultrasonography or magnetic resonance angiography. Carotid or intracranial atherosclerosis was classified as below moderate (0%‐49% stenosis), moderate (50%‐69%), or severe (70%‐100%). In patients with moderate or severe stenosis, cerebral hemodynamics were evaluated using single‐photon emission computed tomography with acetazolamide. Results: None of the 37 patients undergoing preoperative single‐photon emission computed tomography with acetazolamide had impaired cerebral hemodynamics. In‐hospital mortality rate was 3.5% (7/200). Postoperative neurologic morbidity included permanent stroke in 8 patients (4.0%) and transient neurologic deficits in 27 patients (14%). Permanent stroke occurred in 3 of 159 patients (1.9%) with below moderate stenosis and 5 of 41 patients (12.2%) with moderate or severe stenosis (P = .008). Seven of 8 patients (87.5%) with stroke experienced multiple atherothrombotic embolizations, and 1 patient experienced a stroke of unknown cause. In multivariate analysis, previous cerebrovascular accident (odds ratio, 5.0; 95% confidence interval, 2.07‐12.42; P = .0004) and shaggy aorta (odds ratio, 4.2; 95% confidence interval, 1.58‐10.98; P = .0045) were significant determinants of neurologic morbidity. Conclusions: Embolism was the major cause of permanent stroke in our patient population. Preoperative craniocervical and aortic screening may aid in modifying the operative strategy to reduce the occurrence of stroke.

Usefulness of 18 F-FDG-PET/CT in aortic graft infection: two cases

Diagnosis of vascular graft prosthesis infection is crucial, but not straightforward. Here we report two cases in which [18 F] fluoro-2-deoxy-D-glucose positron emission tomography/computed tomography (18 F-FDG PET/CT) was very useful in the diagnosis of aortic graft infection. Case 1: A 77-year-old Japanese man, two months status post aortic arch graft surgery, suffered from repeated fevers. Blood cultures revealed bacteremia. 18 F-FDG-PET/CT ruled out graft infection and diagnosed lumbar pyogenic spondylitis, which was treated with antibiotics, sparing the patient a possible reoperation. Case 2: A 53-year-old Japanese man, seven years status post replacement of the aortic root and ascending aorta, had been suffering from an ostensibly aseptic fistula for over a year and a half. Although repeated CT findings had been negative, 18 F-FDG-PET/CT clearly demonstrated communication between the fistula and the ascending aortic graft. He was treated with repeat ascending aortic replacement, omentopexy, and antibiotics. Our experience supports 18 F-FDG-PET/CT as a promising modality in cases of suspected vascular graft infection.

Transaortic Alfieri Edge-to-Edge Repair for Functional Mitral Regurgitation

There is controversy about handling functional mitral regurgitation in patients undergoing aortic valve or proximal aortic operations. We describe a transaortic Alfieri edge-to-edge repair for functional mitral regurgitation that reduces operative excessive invasion and prolonged cardiopulmonary bypass time. Between May 2013 and December 2016, 10 patients underwent transaortic Alfieri edge-to-edge mitral repair. There were no operative deaths. The severity of mitral regurgitation immediately after the operation by transesophageal echocardiography was none or trivial in all patients. A transaortic Alfieri edge-to-edge repair for functional mitral regurgitation is a simple and safe approach.

Midterm Results of Sternal Band Closure in Open Heart Surgery and Risk Analysis of Sternal Band Removal

Sternal dehiscence, which is responsible for the development of mediastinitis, is a serious complication after cardiothoracic surgery. We retrospectively compared the results of two methods for sternal closure after cardiothoracic surgery performed during January 2009 to May 2012. The methods comprised closure with sternal bands and steel wires (group A, n = 92) versus conventional closure using steel wires alone (group B, n = 442). Although not significantly different between the two groups, no patients undergoing sternal band closure experienced dehiscence or mediastinitis. The incidence of having to remove materials used for sternal closure was significantly higher in group A than in group B. In each case of removal in group A, the materials removed were sternal bands whose tips had caused direct cutaneous irritation. Thus, although sternal bands may be effective for rigid sternal closure, they must sometimes be removed because of chest discomfort caused by the tip of the band.

Obstruction of the left ventricular outflow tract due to pannus formation after the implantation of a carbomedics aortic valve

Excessive pannus formation after implantation of a prosthetic valve is an infrequent but serious complication. A 69-year-old woman who had received a 19-mm CarboMedics aortic valve 11 years ago was readmitted to our hospital with dyspnea and chest oppression. Cineradiography did not show the restriction of valve movement. The aortic peak pressure gradient was calculated by Doppler echocardiography to be 104 mmHg. Based on the diagnosis of stenosis of the left ventricular outflow tract, the patient underwent reoperation. At reoperation, the pannus had formed circumferentially without disturbing the movement of the leaflet. A 19-mm St. Jude Medical Regent valve was implanted after enlargement of the aortic annulus. The patients postoperative course was uneventful. We report this characteristic finding of pannus formation after the implantation of a CarboMedics valve in the aortic position.

Preoperative renal function and surgical outcomes in patients with acute type A aortic dissection

OBJECTIVES There are few data concerning the impact of preoperative renal function, assessed using estimated glomerular filtration rate, on surgical outcomes following acute type A aortic dissection. We investigated the accuracy of estimated glomerular filtration rate (in ml/min/1.73 m(2)) in predicting in-hospital mortality and postoperative renal replacement therapy in such cases. METHODS We reviewed 114 consecutive patients with non-dialysis-dependent renal dysfunction who underwent thoracic aortic surgery for acute type A aortic dissection between 1997 and 2012. Preoperative renal function was categorized as normal (estimated glomerular filtration rate >90; n = 15) or as mild (60-89; n = 39), moderate I (45-59; n = 39), moderate II (30-44; n = 14) or severe (15-29; n = 7) renal dysfunction. RESULTS In-hospital mortality was 14.9%. Eighteen (15.8%) of 114 patients required renal replacement therapy. A more severe stage stratified by preoperative estimated glomerular filtration rate levels could effectively predict postoperative renal replacement therapy (area under the receiver operating characteristic curve 0.786). The best cut-off value of estimated glomerular filtration rate for predicting postoperative renal replacement therapy was 60 (sensitivity 95%, specificity 59%). On multiple regression analysis, the independent preoperative and intraoperative risk factors for postoperative renal replacement therapy were estimated glomerular filtration rate (P < 0.0001), coronary ischaemic time (P < 0.01) and total arch replacement (P < 0.01). Cardiopulmonary bypass time was the sole independent risk factor for in-hospital mortality (P < 0.001). On the other hand, among the morbidities, stroke [odds ratio (OR), 8.68; P < 0.01] and postoperative renal replacement therapy (OR, 5.47; P < 0.01) were independent risk factors of in-hospital mortality, according to multiple logistic regression analysis. CONCLUSIONS Preoperative estimated glomerular filtration rate can effectively predict the need for renal replacement therapy after surgery for acute type A aortic dissection. However, it is not an effective diagnostic tool to predict in-hospital mortality. The complexity of the characteristics of patients who undergo surgical procedures may make prediction of surgical outcomes difficult. Risk models to predict hospital mortality and morbidities are needed to assist clinicians in determining the optimal treatment.

Coronary Artery Bypass Grafting on the Beating Heart Evaluated With Integrated Backscatter

BACKGROUND In beating heart coronary artery bypass grafting (CABG) the effect of ischemic insult during coronary occlusion could not be evaluated immediately. Using transesophageal echocardiography, myocardial performance can be evaluated with analysis of integrated backscatter. METHODS In 15 beating heart CABGs, cyclic variation (CV) of integrated backscatter of the anterior wall before, during, and after the left internal thoracic artery to left anterior descending (LAD) branch anastomosis was measured with transesophageal echocardiography. The patients were divided into two groups according to collateral vessels status (good collateral group n = 6, poor collateral group n = 9). RESULTS In all patients, CV increased significantly after revascularization (8.56+/-2.50 to 11.47+/-3.32 dB, p < 0.0001). During LAD occlusion, significant decrease in CV was found in patients who had poor collateral arteries. At 15 minutes of LAD occlusion, CV decreased from the preocclusion value of 7.51+/-2.21 to 3.23+/-4.03 dB (p < 0.01). CONCLUSIONS Measurement of CV can detect the ischemic insult during coronary occlusion and the effect of revascularization in beating heart CABG.

Neurological outcome and efficacy of intensive craniocervical screening for elective cardiac surgery

OBJECTIVES To evaluate the efficacy of intensive craniocervical screening before elective cardiovascular surgery. METHODS A retrospective analysis of 1134 consecutive patients who underwent routine screening before cardiovascular surgery between November 2004 and December 2014 was conducted. The study was divided into 2 distinct cohorts of patients undergoing surgery: before (n = 500) and after (n = 634) the introduction of intensive screening in January 2009. In 2009, preoperative screening underwent a transition from the evaluation of carotid atherosclerosis alone to that of craniocervical atherosclerosis. Additionally, patients with moderate or greater stenosis on intensive screening underwent single-photon emission computed tomography with acetazolamide. Craniocervical atherosclerosis was classified as no or mild [0-49%: n = 836 (before/after: 370/466)], moderate [50-69%: n = 118 (56/62)] or severe [70-100%: n = 141 (36/105)]. One of 166 (0.6%) patients with moderate or greater stenosis undergoing single-photon emission computed tomography with acetazolamide after the introduction of intensive screening was diagnosed as having impaired cerebral autoregulation. RESULTS The occurrences of perioperative stroke were 2.8% before the introduction of intensive screening and 0.9% after that (P = 0.033). Notably, intraoperative stroke significantly decreased from 1.4% to 0.2% (P = 0.034). Specifically, the occurrence of perioperative stroke in patients with no or mild stenosis decreased significantly after the introduction of intensive screening, from 2.7% to 0.4% (P = 0.007). CONCLUSIONS The incidence of perioperative stroke decreased following the introduction of intensive screening. Intensive screening may be able to detect patients with a greater risk of perioperative stroke.