Noriyuki Tabuchi

Stented elephant trunk procedure combined with ascending aorta and arch replacement for acute type A aortic dissection

OBJECTIVES Despite steadily improving outcomes, surgery for acute type A aortic dissection has several unresolved problems such as expansion of the residual false lumen in the descending aorta. We performed transaortic stented graft implantation into the descending aorta combined with the ascending aorta and aortic arch replacement for acute type A aortic dissection. We review the efficacy and outcomes of this procedure with respect to the residual false lumen and postoperative neurologic complications we encountered. METHODS Nine consecutive patients with acute type A aortic dissection underwent this procedure. The stented elephant trunk graft was implanted through the aortic arch under hypothermic circulatory arrest. The stented graft was 15 cm long in six patients, and 10 cm long in three patients. Enhanced computed tomography (CT) was performed 1 month after surgery and once each year after discharge to evaluate the postoperative time course of the residual false lumen. RESULTS Cardiopulmonary bypass (CPB) time was quite long because of slow cooling and re-warming [352+/-92 (mean+/-SD) min], and average lower-body arrest time was 54+/-10min. The intima in one patient was injured at the time of implantation, and a small leak was created. One patient died of multiorgan failure postoperatively. One patient suffered cerebral injury, and two suffered spinal cord injury perioperatively. Average follow-up time was 40.4 months (range, 13-66 months). One patient died of cerebral infarction during follow up, and the other seven survived and remain well. Postoperative enhanced CT scans showed that the dissected descending aortas attached to the stented grafts and the aortas near the stented grafts returned to normal. In one patient with no re-entry, the false lumen completely closed with thrombi and the entire aorta returned to normal. The diameter of the descending aorta decreased or did not change in six of the seven patients (85.8%) and increased by only 2mm in one of them (14.2%) during follow up. CONCLUSIONS Implantation of a stented elephant trunk into the descending aorta combined with replacement of the ascending aorta and total arch for acute type A aortic dissection is effective in closing the residual false lumen of the descending aorta and in preventing expansion of the descending aorta. However, further technical modifications, such as using a short stented elephant trunk, eliminating aortic clamping, shortening CPB and spinal cord ischemic time, and reconstruction of left subclavian artery, are needed to prevent neurologic complications.

Thickened intima of the aortic arch is a risk factor for stroke with coronary artery bypass grafting

BACKGROUND Perioperative stroke is one of the most serious complications of cardiac surgery. METHODS Using transesophageal echocardiography, we estimated the intimal thickness of the thoracic aorta as an index of the severity of aortic atherosclerosis to determine the risk of stroke in coronary artery bypass grafting (CABG) patients. The study population comprised 315 consecutive patients who underwent isolated CABG with cardiopulmonary bypass. RESULTS Five patients (1.6%) had perioperative cerebral stroke or systemic emboli. We compared the mean intimal thicknesses of the ascending aorta, aortic arch, and descending aorta. Mean thicknesses in patients without stroke were 2.07 +/- 0.76, 2.78 +/- 1.15, and 2.32 +/- 1.21 mm, respectively, and mean thicknesses in the stroke patients were 1.94 +/- 0.55, 6.94 +/- 3.79, and 3.39 +/- 1.85 mm, respectively. The patients with an intima of more than 5 mm at the aortic arch had a significantly greater incidence of perioperative stroke (p = 0.007). CONCLUSIONS These results suggest that patients who have an aortic arch intima thickened to more than 5 mm are at a significantly high risk for perioperative stroke, and thus, the CABG procedure should be carefully evaluated to prevent such complications.

HEMOSTATIC FUNCTION OF ASPIRIN-TREATED PLATELETS VULNERABLE TO CARDIOPULMONARY BYPASS - ALTERED SHEAR-INDUCED PATHWAY

The impaired hemostasis of aspirin-treated patients is an annoying problem during and after cardiopulmonary bypass. The hemostatic function of platelets comprises two mechanisms: the shear-induced and the cyclooxygenase pathways. Because the latter is inhibited in aspirin-treated patients, the hemostatic function depends mainly on the former pathway. To investigate the effect of cardiopulmonary bypass on the shear-induced pathway, a double-blind study of preoperative aspirin treatment (325 mg) and placebo was conducted in 40 patients undergoing coronary artery bypass grafting. Postoperative blood loss was higher in the aspirin-treated patients than in the placebo-treated patients (p < 0.05). The shear-induced hemostasis was monitored by the in vitro bleeding test (Thrombostat), which mimics bleeding through an injured arteriole. The shear-induced pathway of aspirin-treated platelets was not affected before cardiopulmonary bypass, but it was impaired more during the operation (p < 0.01) and remained worse afterward (p < 0.05), compared with that of placebo-treated platelets. The inhibitory effects of aspirin on thromboxane production and on collagen-induced platelet aggregation remained throughout the operation. In aspirin-treated platelets, the aggregation capacity induced by adenosine diphosphate was inhibited before the operation (p < 0.05) and showed substantial recovery during the operation (p < 0.05). These results suggest that the shear-induced pathway of aspirin-treated platelets is more vulnerable to cardiopulmonary bypass than the pathway in normal platelets and causes severe impairment of hemostasis afterward.

Double-patch technique for postinfarction ventricular septal perforation

A modified infarct-exclusion technique for postinfarction ventricular septal perforation is presented. The perforation is closed directly by a small patch next to the conventional patch, and biological glue is applied between the patches to induce stable polymerization. The patch stuck to the infarcted septum, and no residual shunt was observed in any patient because the wide adhesion prevents excessive pressure on the suture line. Seven of 9 patients in whom this method was used had good results. This technique appears suited for repair of ventricular septal perforations, especially those with extensive fresh infarction.

Formation of tissue factor-bearing leukocytes during and after cardiopulmonary bypass.

During cardiopulmonary bypass (CPB), the extrinsic coagulation system initiated by tissue factor (TF) is a major procoagulant stimulus. TF is present in surgical wounds and could be expressed on activated monocytes. However, recent studies have suggested that collagen stimulation rapidly induces TF by leukocyte-platelet complex formation. Therefore, the appearance of TF-bearing leukocytes and their effect on promoting coagulation were investigated in 5 patients undergoing coronary bypass surgery. Neutrophils and monocytes positive for CD41a and TF increased abruptly in circulating blood during CPB. Their increase was most prominent in blood pooled in the pericardial cavity. Monocytes, but not neutrophils positive for TF showed a second peak one day after operation, which accords with the increase in TF mRNA levels in leukocytes. Similarly, an increase in leukocytes positive for TF accords with the activated factor X generation assay using isolated leukocytes, and with an increase in thrombin-antithrombin complex in circulating blood. The second increase in TF-positive monocytes seems to be responsible for these coagulation parameters that remained high one day after operation. After 10 min of blood incubation stimulated by collagen in vitro, simulating activation in the pericardial cavity, significant increases in neutrophils and monocytes positive for TF and platelet were observed. Our present study suggested the involvement of two distinct mechanisms for the appearance of TF-bearing leukocytes responsible for promoting coagulation: the quick appearance being partly explained by the formation of leukocyte-platelet complex that occurs mainly in the pericardial cavity, and the slow appearance via transcriptional activation in monocytes.

Temporary and permanent biventricular pacing via left ventricular epicardial leads implanted during primary cardiac surgery

OBJECTIVES Biventricular pacing (BVP) is a new strategy for treating patients with severe congestive heart failure (CHF) and intraventricular conduction delay, but its full potential and technicalities of BVP require further evaluation. We evaluated BVP benefits in 4 patients in whom we implanted a left ventricular lead during primary cardiac surgery. METHODS Four CHF patients treated surgically between October 2000 and August 2001 underwent, at primary surgery, the implantation of leads in the right atrium, right ventricle, and left ventricle (LV) for postsurgical BVP. All patients had severe LV dysfunction and dilatation with intraventricular conduction delay. Surgeries involved CABG alone (n = 1), CABG + Dors operation (n = 2), and tricuspid valve replacement + Maze procedure (n = 1). BVP was begun immediately after surgery in all 4 patients. Hemodynamic variables with BVP were compared to those without BVP for each patient, and the utility and technical aspects of implantation were evaluated. RESULTS BVP increased mean systemic blood pressure by 11% and mean LV stroke work index by 19% in the acute postsurgery period, and reduced mitral regurgitation. Two of the patients were implanted with a generator for permanent BVP, one at 1 month and the other at 6 months after surgery. The threshold of the LV epicardial lead of these 2 patients was below 2 V during follow-up, and BVP was successful. CONCLUSIONS Temporary BVP during the short-term after cardiac surgery improved cardiac function and decreased mitral regurgitation in all 4 of our patients. Epicardial lead implantation may thus be a useful option during surgical treatment of patients with CHF and intraventricular conduction delay if long-term permanent BVP is indicated.

Biventricular pacing with coronary bypass and Dor’s ventriculoplasty

We applied biventricular pacing to a patient with severe ischemic dilated cardiomyopathy (left ventricular [LV] ejection fraction 19%, LV end-diastolic volume 360 mL, and complete left bundle branch block). An epicardial LV lead was surgically implanted concomitant with on-pump beating coronary artery bypass grafting and Dors endoventricular circular patch plasty. Biventricular pacing immediately achieved the resynchronization of the LV contraction, and improved cardiac function as well as reducing mitral regurgitation. Biventricular pacing combined with cardiac surgery for patients with cardiomyopathy and complete left bundle branch block may produce beneficial effects on LV function.

MONITORING OF ANTICOAGULATION IN APROTININ-TREATED PATIENTS DURING HEART OPERATION

Since aprotinin has become extensively used during cardiopulmonary bypass the maintenance of safe anticoagulation is a concern. Aprotinin affects anticoagulation measurement by the activated clotting time. Therefore, a reliable new measurement is needed to monitor anticoagulation during cardiopulmonary bypass. In the present study, we tested the efficacy of two alternative measurements in which whole blood clotting was stimulated by high-dose thromboplastin or by high-dose thrombin. During cardiopulmonary bypass under standardized heparinization, the activated clotting time was twofold longer in the aprotinin group than in control group (p < 0.05), whereas high-dose thromboplastin and high-dose thrombin groups were not significantly affected by aprotinin. In laboratory tests using blood from healthy volunteers, all methods showed linear correlation with heparin concentration in the absence of aprotinin (p < 0.05). However, the activated clotting time measurement was prolonged more by heparin when aprotinin was present (p < 0.05), whereas high-dose thromboplastin and high-dose thrombin measurements were not. Moreover, these measurements were faster and more dependable than the activated clotting time. Therefore, high-dose thromboplastin time and high-dose thrombin time seem to be reliable for monitoring anticoagulation when aprotinin is used during cardiopulmonary bypass.

Verapamil and nitroglycerin improves the patency rate of radial artery grafts.

The best way to prevent spasm of the radial artery is still under investigation. We retrospectively compared the effectiveness of topical verapamil-nitroglycerin with papaverine in preventing graft spasm in 215 patients who underwent isolated conventional coronary artery bypass using a radial artery. Postoperative angiographic data were successfully collected in 116 patients. Perioperative radial artery graft spasm was observed in 2 patients in the papaverine group and 1 in the verapamil-nitroglycerin group; this difference was not considered significant. Complete or functional occlusion was detected by postoperative angiography in 13 grafts (10 in the papaverine group and 3 in the verapamil-nitroglycerin group). Multivariate regression analysis revealed that topical papaverine and grafting to the right coronary artery significantly increased the rate of occlusion of radial artery grafts. Although further studies are needed, our data support the view that topical verapamil-nitroglycerin reduces the incidence of radial artery graft occlusion.

Identification of tissue factor and platelet-derived particles on leukocytes during cardiopulmonary bypass by flow cytometry and immunoelectron microscopy

The extrinsic coagulation system initiated by tissue factor (TF) appears to be a major procoagulant stimulus during cardiopulmonary bypass (CPB), although the precise mechanisms remain to be revealed. We recently reported the appearance of TF-bearing leukocytes during CPB and described their role in promoting coagulation. In this study, we visually identified the in-vivo appearance of TF-bearing leukocytes and platelet-derived particles on leukocytes in the pericardial blood during cardiac surgery with CPB, by flow cytometry and immunoelectron microscopy. Preliminary flow cytometric experiments showed that the proportion of TF-positive or both TF- and platelet antigen CD41a-positive leukocytes was increased markedly in pericardial blood obtained during CPB, compared with the proportions in preoperative circulating blood. Immunoelectron microscopic analysis revealed that both monocytes and polymorphonuclear leukocytes in the pericardial blood express TF. On the surfaces of these cells, CD41a-positive or both CD41a- and TF-positive platelet-derived particles were observed. Platelet-derived particles include not only microparticles, but also platelets themselves. Leukocytes from preoperative circulating blood contained far fewer of these particles. Our results demonstrate the in-vivo appearance of TF-bearing platelet-derived particles on leukocytes during cardiac surgery with CPB. These findings may be important for the development of strategies to control procoagulant activities during and after cardiac surgery.