Masashi Mizuno

Open heart surgery with deep hypothermia and cardiopulmonary bypass in small and toy dogs.

OBJECTIVE To evaluate open heart surgery with deep surface-induced hypothermia (sHT) and low-flow cardiopulmonary bypass (CPB) in small and toy-breed dogs. STUDY DESIGN Case series. ANIMALS Small breed dogs (n=8) weighing <5.5 kg with naturally occurring cardiac disease. METHODS Deep sHT under isoflurane anesthesia and low-flow rate CPB with a small-volume prime circuit were used. Ventricular septal defect was closed directly in 2 dogs and severe mitral regurgitation was corrected with mitral valvuloplasty (MVP) in 5 dogs and mitral valve replacement in 1 dog. RESULTS All dogs survived surgery; 1 dog died 6 days and 1 died 2 months after MVP. The other 6 dogs lived (mean follow-up, 32.8 months; range, 12-65 months). Mean body weight at surgery was 3.6 kg (range, 2-5.3 kg). Mean lowest esophageal temperature was 21.4 degrees C (range, 19.8-23.8 degrees C). Mean lowest pump flow volume was 29.2 mL/kg/min (range, 9.4-57.7 mL/kg/min) during aortic cross-clamping (mean, 53.5 minutes; range, 25-79 minutes). Mean hematocrit before CPB was 38.6% (range, 33-47%) and 20.3% (range, 13-24%) during CPB with a small circuit priming volume of 225-260 mL. CONCLUSION Deep sHT with low-flow rate CPB may be used for open heart surgery in small dogs weighing <5.5 kg. CLINICAL RELEVANCE Open heart surgery for selected congenital defects and acquired defects in small and toy-breed dogs may be successfully performed using deep sHT and CPB.

Mitral valve repair under cardiopulmonary bypass in small-breed dogs: 48 cases (2006-2009)

OBJECTIVE To determine whether mitral valve repair (MVR) under cardiopulmonary bypass would be an effective treatment for mitral regurgitation in small-breed dogs. DESIGN Retrospective case series. ANIMALS 48 small-breed dogs (body weight, 1.88 to 4.65 kg [4.11 to 10.25 lb]; age, 5 to 15 years) with mitral regurgitation that underwent surgery between August 2006 and August 2009. PROCEDURES Cardiopulmonary bypass was performed with a cardiopulmonary bypass circuit. After induction of cardiac arrest, a mitral annuloplasty was performed, and the chordae tendineae were replaced with expanded polytetrafluoroethylene chordal prostheses. After closure of the left atrium and declamping to restart the heart, the thorax was closed. RESULTS Preoperatively, cardiac murmur was grade 3 of 6 to 6 of 6, thoracic radiography showed cardiac enlargement (median vertebral heart size, 12.0 vertebrae; range, 9.5 to 14.5 vertebrae), and echocardiography showed severe mitral regurgitation and left atrial enlargement (median left atrium-to-aortic root ratio, 2.6; range, 1.7 to 4.0). 45 of 48 dogs survived to discharge. Three months after surgery, cardiac murmur grade was reduced to 0/6 to 3/6, and the heart shadow was reduced (median vertebral heart size, 11.1 vertebrae, range, 9.2 to 13.0 vertebrae) on thoracic radiographs. Echocardiography confirmed a marked reduction in mitral regurgitation and left atrium-to-aortic root ratio (median, 1.7; range, 1.0 to 3.0). CONCLUSIONS AND CLINICAL RELEVANCE We successfully performed MVR under cardiopulmonary bypass in small-breed dogs, suggesting this may be an effective surgical treatment for dogs with mitral regurgitation. Mitral valve repair with cardiopulmonary bypass can be beneficial for the treatment of mitral regurgitation in small-breed dogs.

Surgical Closure of an Atrial Septal Defect Using Cardiopulmonary Bypass in a Cat

OBJECTIVE To describe surgical repair of a large atrial septal defect (ASD) in a cat. STUDY DESIGN Clinical report. ANIMAL A 3-year-old, 3.3 kg, intact male Japanese domestic short-haired cat. METHODS A 10.2-mm-diameter ASD detected by echocardiography was surgically corrected because pulmonary vascular resistance-to-systemic vascular resistance ratio (Qp /Qs ) was 3.2. Using cardiopulmonary bypass (CPB), open surgical repair was achieved with an expanded polytetrafluoroethylene (e-PTFE) graft. The priming volume of the CPB circuit was minimized by cutting the CPB tubing, and partially replacing the priming fluid with whole cat blood. To prevent hemodilution associated with use of cardioprotective agents, surgery was performed on the beating heart. RESULTS At 1-year echocardiographic evaluation, the repair was intact, and at 3 years, the cat was alive without need of medication. CONCLUSIONS Large ASD in a cat can be repaired using e-PTFE under CPB.

Convergence of the Allen--Cahn Equation with Neumann Boundary Conditions

We study a singular limit problem of the Allen--Cahn equation with Neumann boundary conditions and general initial data of uniformly bounded energy. We prove that the time-parametrized family of limit energy measures is Brakkes mean curvature flow with a generalized right angle condition on the boundary.

Plasma cytokine levels in dogs undergoing cardiopulmonary bypass

UNLABELLED Currently, there are no reports of inflammatory responses to CPB in dogs. We investigated the time course of pro- and anti-inflammatory cytokine levels during and after CPB. ANIMALS The study group included 11 dogs that underwent mitral valve repair with CPB, and the control group included 7 healthy dogs that underwent ovariohysterectomy. METHODS Blood samples from the study group dogs were collected before, during and after surgery and analyzed for plasma levels of interleukin-6 (IL-6), tissue necrosis factor-α (TNF-α), interleukin-10 (IL-10), white blood cells (WBC), and C-reactive protein (CRP). Each inflammatory parameter was also compared with that of the control group dogs. RESULTS After CPB, plasma levels of IL-6, WBC counts, and CRP levels were significantly higher than preoperative levels, and IL-6 levels in the study group were significantly higher than those in the control group. CONCLUSIONS CPB induces a systemic inflammatory response in dogs.

Plasma atrial natriuretic peptide is an early diagnosis and disease severity marker of myxomatous mitral valve disease in dogs

The aim of this study was to retrospectively assess the clinical usefulness of plasma atrial natriuretic peptide (ANP) concentrations for determining the severity of myxomatous mitral valve disease (MMVD) in dogs. Plasma ANP levels were found to be significantly higher in dogs with MMVD compared to healthy dogs, and plasma ANP levels increased significantly in dogs with progressive heart failure. In dogs with MMVD, stepwise regression analysis revealed that the left atrium/aorta ratio and fractional shortening could be used to predict the plasma ANP concentration. These results indicated that plasma ANP rose with an increase in the volume overload of the left side of the heart. Plasma ANP discriminated cardiomegaly from non-cardiomegaly caused by asymptomatic MMVD. We conclude, therefore, that plasma ANP concentrations may be a clinically useful tool for early diagnosis of asymptomatic MMVD in dogs.

Surgical treatment of severe pulmonic stenosis under cardiopulmonary bypass in small dogs

OBJECTIVES The aim of this study was to report the long-term outcome of the surgical palliation of pulmonic stenosis in dogs. METHODS The subjects comprised three female and six male dogs, mean (±sd) age: 23 (±25) months, mean (±sd) weight: 3·4 (±2·1) kg, diagnosed with severe pulmonic stenosis and right ventricular hypertrophy, with an average preoperative pressure gradient of 153 (±43) mmHg on echocardiography. RESULTS The pressure overload with severe pulmonic stenosis was reduced by valvotomy, i.e., open pulmonary valve commissurotomy, with/without biomembrane patch grafting, under cardiopulmonary bypass. The postoperative pressure gradient at 1 to 7 days was significantly decreased to 65 (±39) mmHg (P<0·05). The reduced pressure gradient was maintained at 58 (±38) mmHg at final follow-up. CLINICAL SIGNIFICANCE Open valvotomy, pulmonary valve commissurotomy and biomembrane patch grafting were effective in reducing obstruction in severe pulmonic stenosis in dogs.

Pathologic Manifestations on Surgical Biopsy and Their Correlation with Clinical Indices in Dogs with Degenerative Mitral Valve Disease.

Background Evaluation of myocardial function is clinically challenging in dogs with degenerative mitral valve disease (DMVD). Although myocardial dysfunction is caused by pathologic degeneration, histopathologic progression is poorly understood. Objectives To characterize myocardial and pulmonary pathologic changes according to severity in dogs with naturally occurring DMVD, and to investigate whether or not pathologic degeneration is reflected by traditional clinical indices. Animals One hundred and seventeen dogs with naturally occurring DMVD. Methods Prospective observational study. Biopsied left atrium (LA), left ventricle (LV), and lung were evaluated histologically, and an attempt was made to correlate pathologic findings with clinical indices. Results Severe myocardial changes were observed in all International Small Animal Cardiac Health Council classes. In the lung, heart failure cell levels were significantly increased in class III patients (P < .0001). In a paired comparison, the LA showed significantly more severe degeneration than the LV, including myocardial fatty replacement, immune cell infiltration, and interstitial fibrosis (P < .0001). In contrast, myocardial cells were more hypertrophied in the LV than in the LA (P < .0001). Left ventricular end‐diastolic dimension (LVEDd) was associated with fatty replacement (P = .033, R 2 = 0.584) and myocardial vacuolization (P = .003, R 2 = 0.588) in the LA. Conclusions and Clinical Importance In DMVD, although severe pathologic changes may be evident even in early stages, there may be pathologic discrepancy between the LA and the LV. Myocardial degeneration may be reflected by clinical indices such as LVEDd and EF.

Hölder estimates for solutions of the Cauchy problem for the porous medium equation with external forces

We study the interior Hölder regularity problem for weak solutions of the porous medium equation with external forces. Since the porous medium equation is the typical example of degenerate parabolic equations, Hölder regularity is a delicate matter and does not follow by classical methods. Caffrelli-Friedman, and Caffarelli-Vazquez-Wolansky showed Hölder regularity for the model equation without external forces. DiBenedetto and Friedman showed the Hölder continuity of weak solutions with some integrability conditions of the external forces but they did not obtain the quantitative estimates. The quantitative estimates are important for studying the perturbation problem of the porous medium equation. We obtain the scale invariant Hölder estimates for weak solutions of the porous medium equations with the external forces. As a particular case, we recover the well known Hölder estimates for the linear heat equation.

Post-mortem evaluation of expanded polytetrafluoroethylene (ePTFE) used in mitral valve repair in dogs

Mitral valve repair is one of the treatment options for mitral regurgitation. Expanded polytetrafluoroethylene (ePTFE) is a polymer that has been widely used in cardiovascular surgery. In this case series, we report the autopsy and histological findings in 6 dogs that underwent cardiopulmonary bypass for mitral annuloplasty using ePTFE sheets and chordoplasty using ePTFE sutures. From May 2005 to October 2009, 3 female and 3 male dogs with severe mitral regurgitation underwent mitral valve repair. This case series included 3 Cavalier King Charles spaniels, 2 Maltese, and 1 Shih Tzu. The survival period after surgery was 19-72 (35 ± 19) months. In all the cases, autopsy revealed that the ePTFE sheets and sutures were not damaged and well integrated into the surrounding highly differentiated, connective tissues. Low-power microscopy revealed that in all cases, the tissues surrounding the ePTFE sheet in the mitral valve annulus had almost completely been covered by granulation tissue. No inflammatory infiltrate or thrombogenesis was observed around the ePTFE in any of the cases. There was no evidence of reactive changes in the region surrounding the ePTFE. These results suggest that ePTFE has excellent tissue compatibility and durability and can be effectively used for canine mitral valve repair.