Comparison of St. Thomas II Cardioplegia and Modified Del Nido Cardioplegia in Dogs Undergoing Mitral Valve Surgery.

Myocardial protection has become an essential adjunctive procedure in veterinary cardiac surgery. Del Nido cardioplegia is a good alternative to the traditional St. Thomas II (ST) cardioplegia in open heart surgery in humans. This study aims to compare intra- and postoperative results between ST cardioplegia and modified del Nido (mDN) cardioplegia in mitral valve surgery in dogs with myxomatous mitral valve disease (MMVD). This retrospective study was conducted using clinical records of 16 MMVD dogs that underwent either ST or mDN cardioplegia. We measured cardiopulmonary bypass (CPB) time, aortic cross-clamp (ACC) time, total operation time, the number of cardioplegia doses, total amount of cardioplegia, required defibrillations, in-hospital mortality and pre- and one-month postoperative echocardiographic variables. CPB (159.4 ± 16.1 vs. 210.1 ± 34.0 min), ACC (101.4 ± 7.0 vs. 136.0 ± 24.8 min) and total operation time (262.3 ± 13.1 vs. 327.0 ± 45.4 min) were significantly shorter in the mDN group (p < 0.05). The number of cardioplegia doses (3.25 ± 0.4 vs. 6.25 ± 1.2) and total amount of cardioplegia (161.3 ± 51.5 vs. 405.0 ± 185.9 mL) in the mDN group were also significantly smaller than the ST group (p < 0.05). No difference was observed in the requirement of defibrillation, in-hospital mortality and pre- and postoperative echocardiographic variables. The utilization of mDN cardioplegia was associated with shorter operative time in mitral valve surgery in dogs.

Surgical treatment for left atrial rupture due to myxomatous mitral valve disease in three dogs: A case report.

INTRODUCTION: Myxomatous mitral valve degeneration (MMVD) is an acquired heart disease which sometimes result in pulmonary oedema and left atrial rupture. In previous reports, left atrial rupture has been non-surgically controlled and its prognosis investigated. There is, however, no report concerning surgically treated left atrial rupture with mitral valvuloplasty and follow-up results. OBJECTIVES: This report aimed to develop a surgical strategy for a case of left atrial rupture caused by MMVD. MATERIALS AND METHODS: Three dogs were presented at a private hospital for surgical treatment of MMVD. All three dogs had a previous history of left atrial rupture due to MMVD. The left atrium rapture was diagnosed from indicating that characteristics of the drained pericardial effusion consistent with blood. Mitral valvuloplasty was performed in all dogs using an extracorporeal circulation machine, and the surgical procedure was modified according to each case. In cases with severe adhesion between the pericardial and left atrial appendage, suturing of the left atrial appendage was performed strategically. Additionally, in cases with severe hypotension caused by left atrial rupture, cardiopulmonary bypass was started as soon as possible during the surgical procedure. DISCUSSION AND CONCLUSION: Since the haemodynamics of all dogs had improved, and the owner reported no cardiac-related clinical signs, all drugs were withdrawn 3 months after surgery. Since left atrial rupture due to MMVD can cause hypotension, cardiopulmonary bypass should be started as soon as possible during the surgical procedure to maintain the blood pressure and suturing of the left atrial appendage should be performed strategically.

Hemodynamic Effects of Protamine Infusion in Dogs with Myxomatous Mitral Valve Disease Undergoing Mitral Valvuloplasty.

Protamine, an antagonizing agent to heparin, is indispensable for dogs undergoing cardiopulmonary bypass. Protamine-induced hypotension (PIH) during cardiac anesthesia has been reported in humans. The purpose of this study was to describe the hemodynamic effect of protamine administration in dogs during cardiac surgery in clinical cases. Study design: Retrospective, clinical, cohort study. A total of 14 client-owned dogs who suffered heart failure due to medically uncontrolled myxomatous mitral valve disease (MMVD) were included in this study. The severity of MMVD was classified according to American College of Veterinary Internal Medicine staging (ACVIM: stage B2, C, D) and dogs undergoing mitral valve surgery. Records with clinical data for dogs treated between July 2019 to August 2020 were examined for age, sex, breed, body weight, concurrent diseases, hospitalization, anesthetic record, and mortality within 3 months after the operation. PIH was defined as mean arterial pressure (MAP) lowered by 20% of that before protamine infusion. To evaluate the effect of protamine on hemodynamic variables, each of the other values was compared with values at the beginning of protamine infusion. MAP decreased by 41.0 and 45.7% in two dogs (14.3%) compared with pressure before protamine infusion. Others did not show obvious alteration in hemodynamic variables. Epinephrine treatment alleviated hypotension in one dog. Another dog with systemic hypotension concomitant with elevated central venous pressure did not respond to epinephrine treatment and a reboot of extracorporeal circulation was required. Reheparinization and reinstitution of cardiopulmonary bypass successfully resuscitate the second dog. In conclusion, clinicians should alert the incidence of severe hypotension even with slow protamine infusion following canine cardiac surgery. This study also provides two effective treatments for catastrophic hypotension during protamine infusion.

Metabolic alkalosis following mitral valvuloplasty in a dog with preoperative acute kidney injury.

CASE DESCRIPTION: An 11-year-old sexually intact male Shih Tzu diagnosed with acute kidney injury and left-sided congestive heart failure that had nonelective mitral valve surgery. CLINICAL FINDINGS: Metabolic alkalosis developed postoperatively, and plasma bicarbonate concentration peaked 2 days after surgery (40.2 mmol/L; pH, 7.550). TREATMENT AND OUTCOME: Acetazolamide administration increased the urinary excretion of bicarbonate and contributed to the improvement of the dog's acid-base status and oxygenation capacity. Metabolic alkalosis persisted for 4 days after surgery, and no treatment was required after resolution. Plasma urea nitrogen and creatinine concentrations normalized 2 days after surgery. CLINICAL RELEVANCE: Severe metabolic alkalosis can occur as a complication following mitral valve surgery. Acetazolamide may be suitable for the treatment of severe metabolic alkalosis.

Comparison of pancreatic and renal blood flow in a canine tachycardia-induced cardiomyopathy model.

The pancreas is believed to be vulnerable to hypoperfusion. In dogs with acute pancreatitis, pancreatic ischemia due to heart failure can worsen the condition. However, changes in pancreatic blood flow associated with decreased cardiac function have not been previously studied in dogs. Therefore, we aimed to identify and compare changes in pancreatic versus renal blood flow as a result of cardiac dysfunction. Seven dogs were subjected to rapid ventricular pacing to create heart failure models. Noninvasive blood pressure measurement, ultrasonic cardiography, contrast-enhanced ultrasonography for pancreatic blood flow measurement, and para-aminohippuric acid clearance for renal blood flow measurement were performed before starting and at 2 and 4 weeks after starting the pacing. Left ventricular cardiac output and mean blood pressure decreased at 2 and 4 weeks after starting the pacing, and pancreatic blood flow decreased at 2 and 4 weeks after starting the pacing. However, renal blood flow did not change at 2 weeks but decreased 4 weeks after starting the pacing. Overall, this study demonstrated that reduced pancreatic blood flow due to cardiac dysfunction occurs, similar to renal blood flow. This suggests that decreased pancreatic blood flow is not unusual and may frequently occur in dogs with heart failure. The results of this study support the speculation that heart failure can exacerbate acute pancreatitis. Additionally, this study provides useful basic information for designing further studies to study this association.

The effect of telmisartan on the ventricular systolic function in dogs with experimental supraventricular tachyarrhythmia.

Maintaining a good ventricular systolic function is important in the long-term therapy of dogs with supraventricular tachyarrhythmia (SVTA). The objective of this study was to evaluate the inhibitory effect of telmisartan on myocardial injury and the resulting ventricular systolic dysfunction in a canine model of SVTA. A total of 14 dogs were randomly assigned to a Telmisartan (oral telmisartan, 1.0 mg/kg daily, n=7) or a Control (no drug administration, n=7) group; the duration of rapid atrial pacing (RAP) was 3 weeks for both groups. The cardiac troponin I (cTnI) concentration in the Control group was significantly increased after 3 weeks compared to that before RAP initiation (baseline), but no significant difference was observed in the Telmisartan group. Moreover, the cTnI concentration at 3 weeks was significantly lower in the Telmisartan group than in the Control group. The left ventricular fractional shortening was significantly decreased at 3 weeks compared to that at baseline in both groups. However, fractional shortening at 3 weeks was significantly higher in the Telmisartan group than in the Control group. The cardiac output values in the Control group were significantly decreased at 3 weeks compared with those at baseline, but no significant difference was observed in the Telmisartan group. This study demonstrates that telmisartan inhibits the reduction in ventricular systolic function and prevents myocardial injury in a canine model of SVTA. Therefore, telmisartan is suggested as a novel treatment for canine SVTA.

Comparison between blood coagulability in the intra-atrial and peripheral regions during the acute phase after rapid atrial pacing.

The changes in intra-atrial blood coagulability of acute phase after development of atrial fibrillation (AF) have not been elucidated in human. In the present study, blood coagulability were examined in the intra-atrial and peripheral regions during the acute phase after development of rapid atrial pacing (RAP) in experimentally created model dog similar to AF, using Total Thrombus-formation Analysis System (T-TAS) that is capable of comprehensively evaluating thrombogenicity in the bloodstream in the microvascular channel. According to the results, both the coagulating function-evaluating time to +10 kPa (T10) and occlusion time (OT) of the AR chip (chip for thrombus analysis mixed with coagulation and platelet) were significantly shortened in the atrial blood as early as 30 min after pacing (T10, 150.5 ± 40.5 s; OT, 212.4 ± 44.3 s) compared to the pre-pacing levels (T10, 194.5 ± 47.5 s; OT, 259.9 ± 49.5 s) (P<0.05). The OT of PL chip (chip for platelet thrombus analysis) was significantly shortened 30 min after pacing (231.8 ± 57.6 s), compared to the pre-pacing level (289.5 ± 96.0 s) (P<0.05). Meanwhile, none of T10 and OT of AR and PL chips showed any significant changes in the peripheral blood. The study demonstrated increase of blood coagulability 30 min after development of RAP. While no significant changes were observed in the peripheral blood in the present study, the outcome suggested that the anti-thrombus treatments are better to be started early after AF even if coagulability of the peripheral blood shows no change.

Comparison of chronological changes in blood characteristics in the atrium and peripheral vessels after the development of non-valvular atrial fibrillation.

INTRODUCTION: Changes in blood characteristics in the atrium and peripheral vessels in patients with non-valvular atrial fibrillation (NVAF) are unclear. We investigated chronological changes in blood characteristics in the atrium and peripheral vessels in a dog model of NVAF by using a total thrombus-formation analysis system (T-TAS). MATERIALS AND METHODS: In NVAF model dogs (n = 8, 390 bpm rapid atrial pacing), atrial and peripheral blood samples were collected. Using this blood, T-TAS was performed before and 1, 2, and 3 weeks after the onset of rapid atrial pacing. RESULTS: Occlusion time (OT: time to +80 and +60 kPa in the AR and PL chips, respectively) and area under the flow pressure curve (AUC) were measured using the AR chip (for mixed white thrombus analysis) and PL chip (for platelet thrombus analysis). OT of the AR chip showed shortening as early as 1 week after NVAF onset, which continued for 3 weeks. OT of the PL chip showed significant shortening in atrium blood only 3 weeks after NVAF onset. By contrast, peripheral blood showed no significant changes in OT or AUC with both AR and PL chips. CONCLUSIONS: In our dog model of NVAF, thrombus formation accelerated in the atrium as early as 1 week after NVAF onset and continued for 3 weeks, but no significant changes were found in peripheral blood. We conclude that antithrombotic therapy should be started early after NVAF onset even if no changes in coagulation activity are observed in peripheral blood.

Effects of cilostazol on the heart rate in healthy dogs.

Appropriate dosages of cilostazol have not been studied in veterinary patients, and the degrees of heart rate (HR) increase have not been studied in dogs administered cilostazol. Therefore, this study aimed to investigate the degrees of HR increase in healthy dogs administered cilostazol. Thirty healthy beagle dogs (15 males and 15 females; age, 5-8 years) were divided into 3 groups of 10 dogs each and orally administered 2.5, 5, or 10 mg/kg cilostazol (twice a day at 8:00 AM and 8:00 PM for 10 days). Higher HR increases were seen in the 5 mg/kg group than in the 2.5 mg/kg group at all time points except 7:00 AM, 9:00 AM, 1:00 PM, and 4:00 PM (P<0.01). Higher HR increases were also observed in the 10 mg/kg group than in the 2.5 mg/kg group at all time points except 4:00 PM (P<0.01). The 10 mg/kg group showed higher HR increases than the 5 mg/kg group at all time points except 6:00 AM, 7:00 AM, 6:00 PM, and 7:00 PM (P<0.05 for 4:00 PM and 5:00 PM; P<0.01 for the other time points). These results together show that the HR of healthy dogs increased in a dose-dependent manner after cilostazol administration twice a day at doses of 5 to 10 mg/kg. These results provide a useful basis for choosing cilostazol in the treatment of bradyarrhythmia in dogs.

Canine case of swallowing syncope that improved after pacemaker implantation.

A 14-year-old intact male West Highland White Terrier weighing 6.9 kg was admitted to the Tokyo University of Agriculture and Technology Animal Medical Center with the complaint of syncope after showing signs of nausea during feeding. Sinus arrest induced by deglutition was confirmed using a Holter electrocardiography test. However, the clinical symptoms significantly improved after implantation of a permanent pacemaker. Seven months after implantation, the dog died from acute pancreatitis, a cause unrelated to the syncope. Immediately after its death, the heart, lungs, gastrointestinal tract, and other organs were dissected and examined histopathologically. The brain was also examined using magnetic resonance imaging. Examination results led to the diagnosis of swallowing-induced situational syncope.