Miki Shimizu

Efficacy of open patch-grafting under cardiopulmonary bypass for pulmonic stenosis in small dogs

OBJECTIVE To assess the efficacy of an open patch-graft technique under cardiopulmonary bypass (CPB) in small dogs. DESIGN AND METHODS A retrospective analysis of 10 dogs with pulmonic stenosis. Records between 1992 and 2002 were reviewed. The effect of surgical correction was evaluated and perioperative parameters were compared between survivors and non-survivors. RESULTS The postoperative pulmonary pressure gradient was reduced in all seven surviving patients. Mean +/- SE was 21.5 +/- 7.4 mmHg (range 3.0-54.2 mmHg) and 6/7 dogs were < 40 mmHg at 3 months postoperatively. Comparing the data between those patients that survived and those that did not, the preoperative pressure gradient (P = 0.04) and volume of the Glucose-Insulin-Kalium solution used (P = 0.001) were significantly higher in those that did not survive. CONCLUSION Open patch-grafting can be performed in small-breed dogs and decreased the pulmonary pressure gradient in survivors at 3 months postoperatively. However, this technique is more invasive than balloon valvuloplasty and should be used cautiously in severely stenosed patients.

The Effect of Intermittent Administration of Sustained Release Isosorbide Dinitrate (sr-ISDN) in Rats with Volume Overload Heart

Recently, it has been reported that intermittent administration of nitrate, with a nitrate-free interval of 10 to 12 hr eliminated expression of tolerance, and maintained its hypotensive effect. In the present study, we evaluated whether nitrate tolerance developed or not with an intermittent administration of sr-ISDN (5 mg/kg/ once a day) in Wistar rats. The effect of this administration protocol for sr-ISDN on the volume overload heart model, aortovenous fistula, was also examined. Furthermore, blood pressure was monitored by radio telemetry during sr-ISDN (5 mg/kg/once a day) administration. Nitrate tolerance did not develop, and eccentric hypertrophy due to volume overload was moderated by sr-ISDN administration. Sr-ISDN administration maintained blood pressure lower level than the placebo group. In conclusion, prolonged intermittent administration of sr-ISDN maintained its hypotensive effect during the entire experiment period, without developing tolerance, and moderated efferent hypertrophy with attenuated volume overload.

Effects of postural change on transesophageal echocardiography views and parameters in healthy dogs

The purpose of the present study is to investigate the effect of postural change on transesophageal echocardiography (TEE) views and parameters of interest anesthesia monitoring in healthy dogs. Twelve Beagle dogs were anesthetized and randomly positioned in one of four postures: right lateral-recumbency, left lateral-recumbency, supine position and prone position. After examinations in one posture, the same examination was demonstrated in another posture and repeated in all postures. In each posture, several standard TEE views were demonstrated: longitudinal cranial-esophageal aorta long-axis-view, transverse middle-esophageal mitral valve long-axis-view and transgastric middle short-axis-view. Additionally, echocardiographic parameters were attempted to measure, and direct blood pressure monitoring was performed in each view. As a result, oriented views, except for transgastric middle short-axis-view, could be obtained in all postures. Stroke volume and peak early diastolic velocity of mitral inflow were lower in supine position compared with those in right and left lateral-recumbency. Heart rate (HR) and systemic vascular resistance were higher in supine position compared with those in right and left lateral-recumbency. Left ventricular pre-ejection period/left ventricular ejection time corrected and uncorrected by HR were higher in supine position compared with those in right and left lateral-recumbency. In conclusion, longitudinal cranial-esophageal aorta long-axis-view and transverse middle-esophageal mitral valve long-axis-view provide useful information of interest anesthesia monitoring, because of their views enable to certainly obtain TEE parameters in various postures. Furthermore, TEE parameters allow to detect the changes of preload, afterload and HR that occur in supine position dogs.

Transarterial Coil Embolization of an Abdominal Aortocaval Fistula in a Dog

A 3-year-old, 5 kg, male Toy Poodle with a mast cell tumor on the left pelvic limb was referred to Tokyo University of Agriculture and Technology Animal Hospital for an oncologic evaluation. On physical examination, a continuous bruit was auscultated over the left inguinal region with a palpable thrill. Cardiac auscultation identified a grade II/VI systolic and a grade I/VI diastolic murmur over the mitral and the aortic valves, respectively. No signs of peripheral cyanosis or congestion were noted. On thoracic radiographs, moderate, generalized enlargement of the cardiac silhouette was observed without evidence of pulmonary edema or pleural effusion. Color Doppler echocardiography identified mild pulmonic, mitral, and aortic valve regurgitation. Measurements of the left ventricle (LV) indicated an increased internal diameter with normal LV wall and septal thicknesses, normal fractional shortening and mild left atrial (LA) enlargement, with normal sinus rhythm. Normal mean arterial blood pressure was obtained on the thoracic limb using the oscillometric method. Laboratory test results (complete blood count, serum biochemistry profile, electrolytes, coagulation profile) were within the normal reference ranges. Ultrasonography of the caudal abdomen showed a caudal vena cava (CVC) with a diameter of 24.6 mm (dog <10 kg, reference values 0.65 0.12 mm) at the site of shunt. Color Doppler with simultaneous electrocardiogram showed turbulent flow in the CVC during the arterial phase. Continuous-wave Doppler interrogation showed continuous low-velocity flow with a pulsatile pattern and spectral broadening of Doppler waveform and peak flow velocity of 3 m/s across the aortocaval shunt (Fig 1). Contrast-enhanced computed tomography (CT) was performed under general anesthesia for anatomic evaluation of the arteriovenous shunt. The contrast timing bolus method was used to synchronize image acquisition. Iodinated contrast medium (2 mL/kg of iodine) was injected into the cephalic vein at flow rate of 1 mL/s. After a 20-second delay, the entire abdomen was scanned with a dual-slice spiral CT scanner. Reconstruction was carried out using contiguous images with a slice thickness of 1.0 mm (total of 149 slices). Post imaging processing showed an aortocaval connection by an anomalous vessel (shunt) located caudal to the renal arteries and a saccular dilatation of the CVC elongating in the caudal direction. The major dilatation was observed caudal to the fistula, 2.6-fold greater than the dilatation observed cranial to the fistula (Fig 2A,B). Endovascular repair was performed under general anesthesia that was maintained with isoflurane. The dog was positioned in right lateral recumbency for a cervical left lateral approach and a small incision in the skin was made to access the left common carotid artery. A 4-Fr multipurpose catheter was inserted through a puncture in the artery and advanced over a guide wire. The catheter tip was positioned in the abdominal aorta, cranial to the fistula to perform aortography. A 5-mL bolus injection of iodinated contrast medium showed the contrast medium being diverted from the aorta into the CVC (Fig 3A). Blood flow in the renal arteries was preserved as observed by contrast filling of the arteries and renal excretion. The tip of the catheter then was repositioned into the AVF over a guide wire to deliver the embolization coil, because contrast injection showed that adequate coil deployment could be achieved through the aorta. An embolization coil of 6.5 mm diameter, 5 loops, and 10 cm in length was deployed along the fistula lumen under fluoroscopic guidance. Aortography a few minutes after coil deployment identified residual flow through the fistula (Fig 3B). Residual flow was also observed on Doppler ultrasonography, but the shunt flow velocity had decreased to 1.5 m/s. Recovery from the anesthesia was uneventful. Postoperative mean arterial blood pressure ranged from From the Department of Veterinary Medicine, Faculty of Agriculture, Tokyo University of Agriculture and Technology, Tokyo, Japan (Nakata, Tanaka, Hamabe, Yoshiyuki, Kim, Suzuki, Aytemiz, Huai-Che, Shimizu, Fukushima). Corresponding author: Ryou Tanaka, DVM, PhD, Department of Veterinary Surgery, Tokyo University of Agriculture and Technology, Saiwai-cho 3-5-8, Fuchu, Tokyo 183-8509, Japan; e-mail: ryo@vet.ne.jp. Submitted May 17, 2013; Revised November 19, 2013; Accepted December 16, 2013. Copyright

The Relationship between Reactive Oxygen Species and Cardiac Fibrosis in the Dahl Salt-Sensitive Rat under ACEI Administration

Enalapril maleate, the oldest and most widely distributed ACEI, and alacepril, the newest and antioxidant ACEI, were compared in the point of cardioprotective effect for Dahl salt-sensitive rat. In order to evaluate the correlation between the three factors, cardiac fibrosis and blood pressure/oxidative-stress marker (tissue TBARS), index of correlation was calculated. The results showed a significant difference in cardiac fibrosis between high-dose alacepril (30 mg/kg/day, group H) and enalapril maleate (10 mg/kg/day, group E). There was significant correlation between cardiac fibrosis and oxidative-stress marker, although there was no correlation between cardiac fibrosis and blood pressure. Fibrosis was more influenced by oxidative stress not by blood pressure, we should not select ACEI only by blood pressure-lowering effect and should more consider cardioprotective effects of ACEI.

Assessment of T2 Relaxation Times for Normal Canine Knee Articular Cartilage by T2 Mapping Using 1.5-T Magnetic Resonance Imaging

Objectives This study aims to assess and compare the T2 relaxation times for articular cartilage of normal canine stifle joints in four regions by T2 mapping using a 1.5-T magnetic resonance imaging (MRI). Methods In vivo prospective study: 20 hindlimbs (left and right) from 10 normal healthy beagle dogs (n = 20). The region of interest (ROI) was subdivided into medial and lateral condyles of femoral cartilage (MF and LF, respectively) and medial and lateral condyles of tibial cartilage (MT and LT, respectively). The T2 relaxation times were assessed in regions where the cartilage thickness was greater than 0.5 mm. Results The median maximum cartilage thickness (mm) of the four ROI were 0.7 (range: 0.9-0.6), 0.6 (range: 0.7-0.5), 0.7 (range: 0.9-0.5) and 0.6 (range: 0.8-0.5) at MF, LF, MT and LT, respectively. The errors in the measurement (%) of the four ROI were 64.3 (range: 50.0-75.0), 75.0 (range: 64.3-90.0), 64.3 (range: 20.0-90.0) and 75.0 (range: 56.3-90.0) at MF, LF, MT and LT, respectively. The median T2 relaxation times (ms) for the articular cartilage of the four ROI were 70.2 (range: 57.9-87.9), 57.5 (range: 46.8-66.9), 65.0 (range: 52.0-92.0) and 57.0 (range: 49.0-66.2) at MF, LF, MT and LT, respectively. The inter-observer correlation coefficient (ICC, 2.1) for the T2 relaxation times of MF was 0.644. Clinical Significance This study offers useful information on T2 relaxation times for articular cartilage of the stifle joint using a 1.5-T MRI in normal dogs.

Effects of changes in analytic variables and contrast medium on estimation of glomerular filtration rates by computed tomography in healthy dogs

OBJECTIVE To investigate effects of changes in analytic variables and contrast medium osmolality on glomerular filtration rate estimated by CT (CT-GFR) in dogs. ANIMALS 4 healthy anesthetized Beagles. PROCEDURES GFR was estimated by inulin clearance, and dogs underwent CT-GFR with iodinated contrast medium (iohexol or iodixanol) in a crossover-design study. Dynamic renal CT scanning was performed. Patlak plot analysis was used to calculate GFR with the renal cortex or whole kidney selected as the region of interest. The renal cortex was analyzed just prior to time of the second cortical attenuation peak. The whole kidney was analyzed 60, 80, 100, and 120 seconds after the appearance of contrast medium. Automated GFR calculations were performed with preinstalled perfusion software including 2 noise reduction levels (medium and strong). The CT-GFRs were compared with GFR estimated by inulin clearance. RESULTS There was no significant difference in CT-GFR with iohexol versus iodixanol in any analyses. The CT-GFR at the renal cortex, CT-GFR for the whole kidney 60 seconds after appearance of contrast medium, and CT-GFR calculated by perfusion software with medium noise reduction did not differ significantly from GFR estimated by inulin clearance. The CT-GFR was underestimated at ≥ 80 seconds after contrast medium appearance (whole kidney) and when strong noise reduction was used with perfusion CT software. CONCLUSIONS AND CLINICAL RELEVANCE Selection of the renal cortex as region of interest or use of the 60-second time point for whole-kidney evaluation yielded the best CT-GFR results. The perfusion software used produced good results with appropriate noise reduction. IMPACT FOR HUMAN MEDICINE The finding that excessive noise reduction caused underestimation of CT-GFR suggests that this factor should also be considered in CT-GFR examination of human patients.

Use of B-mode ultrasonography for measuring femoral muscle thickness in dogs

Assessment of muscle mass is important for evaluating muscle function and rehabilitation outcomes. Ultrasound has recently been successfully used to estimate muscle mass in humans by measuring muscle thickness. This study attempted to standardize procedures for measuring femoral muscle thickness ultrasonographically, as well as quantify the reliability and validity of ultrasound evaluations of muscle thickness compared to measurements made by magnetic resonance imaging (MRI) in dogs. We evaluated the quadriceps femoris (QF), biceps femoris (BF), semitendinosus (ST) and semimembranosus (SM) muscles of 10 clinically healthy Beagle dogs. Scans were taken in 5 different sections divided equally between the greater trochanter and proximal patella. MRI was performed, followed by T1-weighted and contrast-enhanced T1-weighted imaging. Muscle cross-sectional area (CSA) was measured with MRI, and muscle thickness was measured with MRI and ultrasonography. The thickness of the QF, BF and ST muscles as measured by ultrasound at slices 1–3 (from the proximal end to the middle of the femur), 2–4 (middle of the femur) and 2 (more proximal than the middle of the femur), respectively, was correlated with muscle thickness and CSA as measured by MRI. These sites showed a flat interface between muscle and transducer and were situated over belly muscle. No correlation between measurement types was seen in SM muscle. We must confirm this assessment method for various breeds, sizes, ages and muscle pathologies in dogs, thereby confirming that muscle thickness as measured ultrasonographically can reflect muscle function.

Establishment of a method to measure length of the ulnar nerve and standardize F-wave values in clinically normal beagles.

We designed a new method of measuring the length of the ulnar nerve and determining standard values for F-wave parameters of the ulnar nerve in clinically normal beagles. Nerve length must be precisely measured to determine F-wave latency and conduction velocity. The length of the forelimb has served as the length of the ulnar nerve for F-wave assessments, but report indicates that F-wave latency is proportional to the length of the pathway traveled by nerve impulses. Therefore, we measured the surface distance from a stimulus point to the spinous process of the first thoracic vertebra (nerve length 1) and the anterior horn of the scapula (nerve length 2) as landmarks through the olecranon and the shoulder blade acromion. The correlation coefficients between the shortest F-wave latency and the length of nerves 1, 2 or the forelimb were 0.61, 0.7 and 0.58. Nerve length 2 generated the highest value. Furthermore, the anterior horn of the scapula was easily palpated in any dog regardless of well-fed body. We concluded that nerve length 2 was optimal for measuring the length of the ulnar nerve.