Biomedical subjects

Tomohiro Mizuno

Publications and source records attributed to Tomohiro Mizuno.

9 recordsLinked to original sources

PubMed2004

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.

Cardiac Surgical Procedures↗

PubMed2003

Transaortic stented graft implantation for aortic arch aneurysm. Its benefits and risk.

OBJECTIVES: Despite steady improvements, surgery for aortic arch disease, including the distal arch, continues to result in high rates of morbidity and mortality. We have performed aortic arch repair using a transaortic stented graft implantation into the descending aorta in 8 patients who had true aortic arch aneurysms, and here have reviewed the efficacy and problems from this procedure. METHODS: Six patients underwent transaortic stented graft implantation into the descending aorta with bypass to the arch vessels. The other two underwent stented graft implantation into the descending aorta with replacement of the ascending aorta and aortic arch. One patient had a ruptured aneurysm. RESULTS: Each operation was performed via a median sternotomy without left thoracotomy. There was no new postoperative occurrence of left recurrent laryngeal nerve palsy. All the five patients without perioperative neurological complication could be extubated within 24 h after surgery. In each case, postoperative enhanced computed tomography scans showed successful thromboexclusion of the aneurysm. There was no endoleak and no graft migration. One patient suffered cerebral injury. Spinal cord injury occurred in 2 patients, and this serious complication may have been caused by prolonged ischemia in the lower body and the long stented graft. CONCLUSIONS: This surgical strategy was effective for arch aneurysm and produced less damage than a conventional procedure to the postoperative respiratory function, while the operative technique need to be improved to decrease the frequency of brain and spinal cord injury.

Aged↗

PubMed2003

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 Dor's 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.

Aged↗

PubMed2002

Mural thrombus generation in type 2A and 2B von Willebrand disease under flow conditions.

To explore the mechanisms that underlie the bleeding tendency in type 2A and 2B von Willebrand disease (VWD), we analyzed the mural thrombus generation process on a collagen surface under physiologic blood flow in a perfusion chamber using whole blood from these VWD patients. At a low shear rate (50 s(-1)), thrombus generation in all type 2A and 2B VWD patients was comparable to that of healthy controls. At a high shear rate (1500 s(-1)), thrombus generation was impaired in all type 2A patients, whereas that in type 2B VWD patients varied from normal to significantly defective, as judged by epifluorescence microscopy of thrombus surface coverage. However, in type 2B patients who showed normal thrombus generation at 1500 s(-1), the height and volume of thrombi was significantly reduced, albeit with the normal surface coverage, compared with control thrombi, and von Willebrand factor (VWF) was poorly distributed within the type 2B thrombus mass when analyzed in detail by confocal laser scanning microscopy. Addition of purified VWF to patient blood completely reversed the defective spatial thrombus growth in type 2B VWD. Thus, our results confirm the impaired thrombus generation in type 2B VWD, which has never been demonstrable in previous in vitro soluble-phase platelet aggregation assays, and point to the critical function of larger VWF multimers in the proper spatial growth of mural thrombi under high shear rate conditions.

Blood Coagulation↗

PubMed2002

Distinct and concerted functions of von Willebrand factor and fibrinogen in mural thrombus growth under high shear flow.

Using a perfusion chamber and confocal laser scanning microscopy, we analyzed the interplay of von Willebrand factor (VWF) and fibrinogen during thrombus growth on a collagen surface under physiologic high shear rate conditions. During initial thrombogenesis, platelet thrombi were constructed totally by VWF, not by fibrinogen. Fibrinogen accumulated predominantly inside the growing thrombi as a function of time, whereas the thrombus surfaces directly exposed to flow were occupied constantly by VWF throughout the observation period. In perfusion of afibrinogenemia (AF) blood lacking both plasma and platelet fibrinogen, the final height and volume of thrombi were significantly reduced compared with controls, albeit the area of surface coverage was normal. The impaired thrombus growth in AF was only partially corrected by the addition of purified fibrinogen to AF blood, whereas the addition of purified VWF to blood of severe von Willebrand disease (VWD) completely normalized the defective thrombus growth in this disease. Thus, the initial 2-dimensional thrombus expansion involves only VWF, whereas the time-dependent accumulation of fibrinogen, released from activated platelets, acts as a core adhesive ligand, increasing thrombus strength and height and resulting in 3-dimensional thrombus development against rapid blood flow.

Afibrinogenemia↗

PubMed2002

Platelet shape changes and adhesion under high shear flow.

Recent studies have revealed that the platelet adhesive process under flow is tightly regulated by multiple ligand-receptor interactions. However, platelet morphological changes during this process, particularly its physiological relevance, remain unknown under blood flow conditions. Using epifluorescence and scanning electron microscopy, we evaluated the real-time changes in platelet morphology during a platelet adhesive process on a von Willebrand factor-coated surface under physiological high shear flow in a perfusion chamber. Here, we show that dynamic platelet shape changes occurring during distinct phases of the adhesive process are precisely regulated by "inside-out" and "outside-in" integrin signals and are also a key regulatory element in successful platelet thrombogenesis opposing rapid blood flow in vivo.

Androstadienes↗

PubMed2002

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 + Dor's 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.

Aged↗

PubMed2002

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.

Acute Disease↗

PubMedDate not supplied

One piece ultracompact totally implantable electromechanical total artificial heart for permanent use.

An ultracompact, one piece, totally implantable electromechanical total artificial heart (TAH) has been developed as a permanent replacement for failing hearts. It consists of left and right pusher plate blood pumps (stroke volume 55 ml) made of titanium alloy (Ti-6Al-7Nb) sandwiching a miniaturized electromechanical actuator between them. The diameter of the TAH is 90 mm, with a thickness of 70 mm, yielding an overall volume of 400 ml. It weighs 450 g. Although it is miniaturized, it provided a maximum pump output of 8 L/min against a left afterload of 100 mm Hg. It required approximately 12 watts to provide a pump output of 6.5 L/min with maximum efficiency of 13.5%. To balance left and right flow, the right stroke length was made 10% shorter than the left, and an auxiliary compliance chamber was used to compensate for additional flow differences between them. Motor commutation pulses and a Hall effect pusher plate sensor signal were used in the controller to implement the left master alternate variable rate mode. The calf fitting study revealed excellent anatomic compatibility, and the first successful survivor was obtained in December 2001. Studies of system endurance and biocompatibility are required to ensure long-term reliability. This TAH is promising for permanent replacement of the failing heart as well as for bridge to heart transplantation for the smaller size group of end-stage cardiac patients.

Animals↗