Kazuo Niwaya

Early and late stroke after mitral valve replacement with a mechanical prosthesis: risk factor analysis of a 24-year experience

OBJECTIVE We evaluated risk factors for mortality and stroke after mechanical mitral valve replacement between May 1977 and December 2001. METHODS Early and late mortality and stroke were assessed. Potential predictors of mortality and stroke were entered into a Cox proportional hazards model. Actuarial survival and freedom from stroke were determined by a log-rank test. RESULTS Mitral valve replacement was performed in 812 patients. Concomitant procedures included left atrial appendage closure in 493 (61%) patients, tricuspid annuloplasty-replacement in 348 (43%) patients, maze procedure in 185 (23%) patients, plication of the left atrium in 148 (18%) patients, and other procedures in 151 (19%) patients. Five-year actuarial survival was 91.1% +/- 2.3%. Freedom from stroke at 8 years was significantly better in patients with sinus rhythm versus atrial fibrillation (P <.001). Ninety-nine percent of patients with mitral valve replacement combined with a maze procedure were free from stroke, whereas only 89% of patients with mitral valve replacement alone were free from stroke at 8 years after surgical intervention. Seventy-two patients had late stroke; sixty-five patients (90%) were in atrial fibrillation, and 47 (65%) patients had the left atrial appendage closed. Multivariate analysis showed that late atrial fibrillation (odds ratio, 3.39; 95% confidence interval, 1.72-6.67; P =.0001) and omission of the maze procedure (odds ratio, 3.40; 95% confidence interval, 1.14-10.14; P =.003) were the significant risk factors for late stroke. CONCLUSIONS Persistent atrial fibrillation was the most significant risk factor for late stroke after mechanical mitral valve replacement. Restoration of sinus rhythm with a maze procedure nearly eliminated the risk of late stroke, whereas neither closure of the left atrial appendage nor therapeutic anticoagulation prevented this complication.

The use of high-hydrostatic pressure treatment to decellularize blood vessels.

A decellularization method using high-hydrostatic pressure (HHP) technology (>600MPa) is described. The HHP disrupts the cells inside the tissue. The cell debris can be eliminated with a simple washing process, producing clean, decellularized tissue. In this study, porcine aortic blood vessel was decellularized by HHP. The mechanical properties and in vivo performance of the decellularized tissue were evaluated. Mechanical properties of the decellularized tissue were not altered by the HHP treatment. Reduced inflammation of the decellularized tissue was confirmed by xenogenic transplant experimentation. An allogenic transplantation study showed that decellularized blood vessel endured the arterial blood pressure, and there was no clot formation on the luminal surface. In addition, cellular infiltration into the vessel wall was observed 4 weeks after implantation, suggesting that HHP treatments could be applied widely as a high-quality decellularization method.

Surgical Treatment of Aortic Regurgitation due to Takayasu Arteritis Long-Term Morbidity and Mortality

BACKGROUND The goal of this retrospective study was to determine the late outcome of surgical treatment for aortic valve regurgitation due to Takayasu arteritis and correlate it with evidence of inflammation on pathological examination. METHODS AND RESULTS Ninety consecutive patients who underwent surgery for aortic valve regurgitation due to Takayasu arteritis between 1979 and 2003 were studied. Intraoperative pathological specimens of the aortic wall from 69 patients were retrospectively examined for inflammation. Aortic valve replacement was performed in 63 patients (group A) and composite graft repair in 27 patients (group B). The aortic root diameter was 39.9+/-9.5 mm in group A and 54.4+/-13.6 mm in group B (P<0.0001). Preoperative steroid therapy was performed in 40 patients (44.4%). Hospital mortality was 4.8% (3/63) in group A and 7.4% (2/27) in group B. The overall 15-year survival rate was 76.1%. Detachment of the valve or graft occurred in 11.1% (7/63) of group A and in 3.7% (1/27) of group B patients (P=0.43). Late dilatation (>50 mm) of the residual ascending aorta occurred in 11.1% (7/63) of group A and in 3.7% (1/27) of group B patients (P=0.43). Active inflammation was confirmed in intraoperative pathological specimens of 10 patients, and detachment of the valve or graft occurred in 4 of these patients. Univariate analysis of background variables revealed active inflammation to be a risk factor for detachment (P=0.0001; risk ratio 55). CONCLUSIONS Late dilatation of the ascending aorta after aortic valve replacement is a clinically important finding. Active inflammation could be related to valve or graft detachment.

Effect of warm ischemia and cryopreservation on cell viability of human allograft valves

Fibroblast viability of the allograft valve leaflet has been suggested to affect clinical durability. Warm ischemic time is thought to be one of the critical determinants of cell viability. We assessed cell viability of allograft valves by flow cytometry, using a fluorescein diacetate-propidium iodide stain to characterize the effects of warm ischemia and cryopreservation on viability. Twelve human pulmonary valves with harvest-related warm ischemic times (range, 70 to 520 minutes; mean +/- standard deviation, 225 +/- 157 minutes) were studied by flow cytometry. We assessed cell viability of the allograft valve leaflets before and 30 days after storage. A significant negative correlation was found between warm ischemic time (x minutes) and cell viability (y%) before (y = -0.024x + 96.7; r2 = 0.62; p = 0.002) and after 30 days of storage (y = -0.036x + 94.0; r2 = 0.86; p = 0.001). Cell viability of the cryopreserved allograft valves was well preserved (> 70%) with a warm ischemic time less than 520 minutes (8.7 hours).

The impact of diabetic retinopathy on long-term outcome following coronary artery bypass graft surgery

OBJECTIVES We sought to assess the impact of diabetic retinopathy on long-term outcome among patients with diabetes and multivessel coronary artery disease (MVD) following coronary artery bypass graft surgery (CABG). BACKGROUND For diabetics, CABG is the preferred revascularization strategy. Diabetic retinopathy is a major microvascular complication of diabetes, and its severity is directly related to total glycemic exposure. METHODS We identified 223 consecutive diabetics with MVD whose retinae were evaluated within one year prior to CABG. The most recent ophthalmologic records up until the time of CABG were used to evaluate the severity of retinopathy. The median follow-up after CABG was 11.6 years. RESULTS Diabetic retinopathy was a strong independent predictor of overall mortality (relative risk [RR], 4.0), and repeat revascularization (RR, 3.0). In separate analyses of diabetics with retinopathy and without retinopathy, predictors of mortality differed significantly between the two groups. Among diabetics with retinopathy, the presence of either preoperative renal (RR, 2.5) or ventricular (RR, 2.0) dysfunction had unfavorable effects on mortality, but the survival curves did not differ significantly according to the presence or absence of internal thoracic artery (ITA) grafting. In comparison, among diabetics without retinopathy, ITA grafting (RR, 0.34) had a beneficial effect on mortality, and the survival curves varied somewhat according to the presence or absence of renal or ventricular dysfunction. CONCLUSIONS Diabetics with retinopathy had a distinct post-CABG course with a worse long-term prognosis, as compared with diabetics without retinopathy. Retina evaluation is useful for prediction of long-term prognosis and management of diabetics who need CABG.

Durability and outcome of aortic valve replacement with mitral valve repair versus double valve replacement

BACKGROUND The purpose of this study was to evaluate morbidity and mortality after double valve replacement (DVR) and aortic valve replacement with mitral valve repair (AVR + MVP). METHODS From 1977 to 2000, 379 patients underwent DVR (n = 299) or AVR + MVP (n = 80). Actuarial survival and freedom from reoperation were determined by the Kaplan-Meier method. Potential predictors of mortality and reoperation were entered into a Cox multiple regression model. Propensity score was introduced for the multivariable regression modeling for adjustment of a selection bias. RESULTS Survival 15 years after surgery was similar between the groups (DVR, 81% +/- 3%; AVR + MVP, 79% +/- 7%; p = 0.44). Freedom from thromboembolic event at 15 years was similar between the groups (p = 0.25). Freedom from mitral valve reoperation at 15 years was significantly better for the DVR group (54% +/- 5%) as compared with the AVR + MVP group (15% +/- 6%; p = 0.0006), primarily due to progression of mitral valve pathology and early structural deterioration of bioprosthetic aortic valve used for patients with AVR + MVP. After AVR + MVP, freedom from mitral reoperation at 15 years was 63% +/- 16% for nonrheumatic heart diseases, and 5% +/- 5% for rheumatic disease (p = 0.04). CONCLUSIONS Although both DVR and AVR + MVP provided excellent survival, DVR with mechanical valves should be the procedure of choice for the majority of patients because of lower incidence of valve failure and similar rate of thromboembolic complications compared with AVR + MVP. MVP should not be performed in patients with rheumatic disease because of higher incidence of late failure.

Which factors predict the recovery of natural heart function after insertion of a left ventricular assist system

BACKGROUND Recent reports have demonstrated that use of a left ventricular assist system (LVAS) can initiate recovery of cardiac function, and subsequent weaning from the LVAS has attracted considerable interest. In this study we investigated reliable predictors of LVAS weaning. METHODS Eighty-two patients underwent LVAS implantation between April 1994 and July 2006 at our institution. Cardiac function was restored in 8 patients, who were weaned from LVAS after a mean of 5 months (Group R). Thirty-three patients remained on LVAS support for >1 year (Group N) because natural heart function did not show adequate improvement. We retrospectively evaluated the differences between these two groups. Group R was younger, and had a shorter duration of heart failure than Group N (23.4 vs 36.7 years and 13.3 vs 56.1 months, p < 0.01, respectively). Pathologic findings showed that the interstitial fibrosis score was lower in Group R (p < 0.01). Three months after LVAS insertion, B-type natriuretic peptide (BNP) and fractional shortening (FS) were more favorable (66.6 +/- 46 vs 264.5 +/- 170 pg/ml, p < 0.01, and 23 +/- 17.1 vs 12 +/- 9.1%, p < 0.05, respectively) in Group R. Furthermore, Group R received a higher dose of beta-blocker (15.4 +/- 8.4 vs 5.8 +/- 3.9 mg, p < 0.05). CONCLUSIONS Younger age, shorter history of heart failure, and less interstitial fibrosis were effective predictors of weaning from LVAS. Restoration of natural heart function was more rapid and more persistent in candidates for LVAS explantation, and presence of beta-blocker played a prominent role in improving cardiac function after LVAS implantation.

Long-Term Follow-up of Transvenous Defibrillation Leads

Background As a result of longer follow-up after implantation of cardioverter defibrillators (ICD), fatigue of the leads has become a concern. The aim of this study was to determine the incidence and clinical presentation of ICD lead failures. Methods and Results The study population consisted of 241 patients with 249 ICD leads who underwent implantation of an ICD with a transvenous lead system. After device implantation, the patients were routinely followed up every 4 months. Five lead failures (2.0%) occurred as an oversensing of artifact during the follow-up period (2.6±2.1 years); 4 of those 5 patients received inappropriate shocks and 1 case of lead failure was identified in a patient with frequent episodes of non-sustained ventricular fibrillation. In particular, the right ventricular polyurethane transvenous lead in the Medtronic model 6936 failed in 4 (13%) of 31 cases. Percutaneous lead extraction was not available in all cases, so an additional ICD lead was inserted through the same site of the subclavian vein. Conclusions Lead failures may occur 5 years after ICD implantation and polyurethane leads have an especially high incidence of failure. However, there were no follow-up parameters observed that predicted lead failures. (Circ J 2006; 70: 273 - 277)

Ex vivo gene transfer into myocardium using replication-defective retrovirus

Heart transplantation is the most effective therapy for chronic severe heart failure, but there is an extreme shortage of hearts available. We examined the possibility that cardiomyocytes can be modified genetically prior to being grafted to the heart. We used a replication-defective retrovirus carrying the beta-galactosidase (beta-gal) reporter gene. The beta-gal gene was transduced into murine fetal cardiac myocytes by culturing a recombinant retrovirus-producing cell line in a Transwell plate hung into the primary cardiomyocyte culture. The cultured cells were stained with the di-beta-D-galactopyranoside (FDG) and were sorted by fluorescence-activated cell sorting (FACS). FACS analysis showed that 25.5 +/- 4.3% of the cardiomyocytes in a primary culture were positive for beta-gal activity. These cells were transplanted into the hearts of syngeneic adult mice. Expression of the beta-gal gene in the grafted cells was demonstrated by staining with 5-bromo-4-chloro-3-indoyl-beta-D-galactoside (X-gal). Gene expression was recognized as long as 6 mo after cell transplantation. Histologic analysis showed neither inflammation nor fibrous scar tissue on the host myocardium. This study demonstrated that genetically modified cardiac cells were transplantable to the heart.

Redo off-pump coronary bypass grafting with arterial grafts for Kawasaki disease

Surgical revascularization for coronary artery lesions secondary to Kawasaki disease is relatively uncommon. The late stenosis of the saphenous vein graft is the problem to be solved. We report a case of redo off-pump coronary bypass grafting in a 35-year-old man, 20 years after bypass grafting using a saphenous vein graft. Off-pump total arterial revascularization was performed uneventfully. The procedure comprised grafting of bilateral internal thoracic arteries to left anterior descending branch and obtuse marginal branch, and radial artery to AV branch and posterior descending branch. Off-pump total arterial revascularization is a safe and less invasive procedure at the time of redo operation, even for patients with Kawasaki disease.