Long-term incidence and risk of noncardiovascular and all-cause mortality in apparently healthy cats and cats with preclinical hypertrophic cardiomyopathy.

BACKGROUND: Epidemiologic knowledge regarding noncardiovascular and all-cause mortality in apparently healthy cats (AH) and cats with preclinical hypertrophic cardiomyopathy (pHCM) is limited, hindering development of evidence-based healthcare guidelines. OBJECTIVES: To characterize/compare incidence rates, risk, and survival associated with noncardiovascular and all-cause mortality in AH and pHCM cats. ANIMALS: A total of 1730 client-owned cats (722 AH, 1008 pHCM) from 21 countries. METHODS: Retrospective, multicenter, longitudinal, cohort study. Long-term health data were extracted by medical record review and owner/referring veterinarian interviews. RESULTS: Noncardiovascular death occurred in 534 (30.9%) of 1730 cats observed up to 15.2 years. Proportion of noncardiovascular death did not differ significantly between cats that at study enrollment were AH or had pHCM (P = .48). Cancer, chronic kidney disease, and conditions characterized by chronic weight-loss-vomiting-diarrhea-anorexia were the most frequently recorded noncardiovascular causes of death. Incidence rates/risk of noncardiac death increased with age in AH and pHCM. All-cause death proportions were greater in pHCM than AH (65% versus 40%, respectively; P < .001) because of higher cardiovascular mortality in pHCM cats. Comparing AH with pHCM, median survival (study entry to noncardiovascular death) did not differ (AH, 9.8 years; pHCM, 8.6 years; P = .10), but all-cause survival was significantly shorter in pHCM (P = .0001). CONCLUSIONS AND CLINICAL IMPORTANCE: All-cause mortality was significantly greater in pHCM cats due to disease burden contributed by increased cardiovascular death superimposed upon noncardiovascular death.

Comparison of metabolomics and platelet aggregometry between Plavix and generic clopidogrel in cats: a pilot study.

OBJECTIVES: This pilot study sought to assess the metabolism of Plavix (Bristol-Myers Squibb/Sanofi) and generic clopidogrel in cats, using a novel assay for the measurement of clopidogrel, clopidogrel carboxylic acid (CCA) and clopidogrel active metabolite (CAM-D). METHODS: This was a prospective, randomized, double-blind study. Four healthy, skeletally mature cats were enrolled into the study. There were two treatment phases during which cats received either Plavix or generic clopidogrel at a dosage of 18.75 mg PO q24h for 7 days with a 2 week washout between phases. During each phase, plasma concentrations of parent drug and active and inactive metabolites were measured along with impedance platelet aggregometry in response to adenosine diphosphate (ADP). RESULTS: The ratio of CAM-D between generic clopidogrel and Plavix was 0.83 (equivalence reference 1.00, 90% confidence interval 0.80-1.25). Inhibition of ADP-induced platelet aggregation was variable, with two cats classified as non-responders in both treatment phases. The concentrations of CAM-D were not predictive of aggregometry-based responsiveness to either formulation of clopidogrel. CONCLUSIONS AND RELEVANCE: This is the first study comparing Plavix and generic clopidogrel in cats. Administration of the generic formulation resulted in comparable plasma concentrations of clopidogrel active metabolite when compared with Plavix.

International collaborative study to assess cardiovascular risk and evaluate long-term health in cats with preclinical hypertrophic cardiomyopathy and apparently healthy cats: The REVEAL Study.

BACKGROUND: Hypertrophic cardiomyopathy is the most prevalent heart disorder in cats and principal cause of cardiovascular morbidity and mortality. Yet, the impact of preclinical disease is unresolved. HYPOTHESIS/OBJECTIVES: Observational study to characterize cardiovascular morbidity and survival in cats with preclinical nonobstructive (HCM) and obstructive (HOCM) hypertrophic cardiomyopathy and in apparently healthy cats (AH). ANIMALS: One thousand seven hundred and thirty client-owned cats (430 preclinical HCM; 578 preclinical HOCM; 722 AH). METHODS: Retrospective multicenter, longitudinal, cohort study. Cats from 21 countries were followed through medical record review and owner or referring veterinarian interviews. Data were analyzed to compare long-term outcomes, incidence, and risk for congestive heart failure (CHF), arterial thromboembolism (ATE), and cardiovascular death. RESULTS: During the study period, CHF, ATE, or both occurred in 30.5% and cardiovascular death in 27.9% of 1008 HCM/HOCM cats. Risk assessed at 1, 5, and 10 years after study entry was 7.0%/3.5%, 19.9%/9.7%, and 23.9%/11.3% for CHF/ATE, and 6.7%, 22.8%, and 28.3% for cardiovascular death, respectively. There were no statistically significant differences between HOCM compared with HCM for cardiovascular morbidity or mortality, time from diagnosis to development of morbidity, or cardiovascular survival. Cats that developed cardiovascular morbidity had short survival (mean ± standard deviation, 1.3 ± 1.7 years). Overall, prolonged longevity was recorded in a minority of preclinical HCM/HOCM cats with 10% reaching 9-15 years. CONCLUSIONS AND CLINICAL IMPORTANCE: Preclinical HCM/HOCM is a global health problem of cats that carries substantial risk for CHF, ATE, and cardiovascular death. This finding underscores the need to identify therapies and monitoring strategies that decrease morbidity and mortality.

Feline Cardiogenic Arterial Thromboembolism: Prevention and Therapy.

Feline cardiogenic arterial thromboembolism (CATE) is a devastating disease whereby 33% of cats survive their initial event, although approximately 50% of mortality is from euthanasia. Short-term management focuses on inducing a hypocoagulable state, improving blood flow, and providing supportive care. Ideally, all cats should be given 72 hours of treatment to determine the acute clinical course. Preventive protocols include antiplatelet and/or anticoagulant drugs, with the only prospective clinical trial demonstrating that clopidogrel is superior to aspirin with a lower CATE recurrence rate and longer time to recurrent CATE. Newer anticoagulant drugs hold great promise in the future of managing this disease.

Cardiogenic embolism in the cat.

Cardiogenic embolism (CE) in the cat, which has also been referred to as arterial thromboembolism, feline arterial thromboembolism, and saddle thrombus has been identified clinically in cats for decades and is an important clinical development and cause of death in cats with underlying heart disease. While a better understanding of this condition has been developed over the decades it is extremely frustrating to clinicians that there have not been dramatic changes in prevention or outcome. Only recently has the first prospective thromboprophylactic study on CE in cats been completed. While new antithrombotic drugs are developed for humans on a regular basis, it has been challenging to get pharmaceutical companies to focus on the feline species. Additionally, there remains an absence of clinical data to identify cats at risk for developing CE aside from the simple fact that they have underlying heart disease. This review will attempt to present a summary of where we stand in 2015 with regards to clinical presentation, survival, thrombotic risk, and prevention.

Secondary prevention of cardiogenic arterial thromboembolism in the cat: The double-blind, randomized, positive-controlled feline arterial thromboembolism; clopidogrel vs. aspirin trial (FAT CAT).

OBJECTIVES: To determine if clopidogrel administration is associated with a reduced likelihood of recurrent cardiogenic arterial thromboembolism (CATE) in cats compared to aspirin administration. Secondary aims were to determine if clopidogrel administration had an effect on the composite endpoint of recurrent CATE and cardiac death and to identify adverse effects of chronic clopidogrel or aspirin therapy. ANIMALS: Seventy-five cats that survived a CATE event. METHODS: Multicenter, double-blind, randomized, positive-controlled study. Cats were assigned to clopidogrel (18.75 mg/cat PO q 24 h) or aspirin (81 mg/cat PO q 72 h). Kaplan-Meier survival curves were created for each endpoint and the log rank test performed to compare treatment groups with respect to time to event and the likelihood of the event occurring. RESULTS: The mean age of all cats was 8.0 ± 3.5 yr and 57/75 (76%) were male (p < 0.001); 62/75 (83%) were mixed breed with the remainder including Persian, Abyssinian, American Shorthair, Bengal, Birman, Himalayan, Maine Coon, Ragdoll, Snowshoe, and Sphynx breeds. Only 15% (11/75) of cats had a history of heart disease recorded prior to the CATE event. Clopidogrel administration was associated with significantly reduced likelihood of recurrent CATE compared to aspirin (p = 0.024) and had a longer median time to recurrence [443 (95% CI 185-990) days vs. 192 (95% CI 62-364) days, respectively]. Clopidogrel was also associated with a significantly reduced likelihood of the composite endpoint of recurrent CATE or cardiac death (p = 0.033) with a longer median time to event [346 (95% CI 146-495) days vs. 128 (95% CI 58-243) days]. CONCLUSIONS: Clopidogrel administration significantly reduces the likelihood of recurrent CATE compared with aspirin in cats; both drugs were well tolerated.

In vitro effects of the glycoprotein IIb/IIIa receptor antagonists abciximab and eptifibatide on platelet aggregation in healthy cats.

OBJECTIVE: To determine effects of the glycoprotein IIb/IIIa receptor antagonists abciximab and eptifibatide on in vitro inhibition of cat platelets. SAMPLE: Venous blood samples from 10 healthy cats. PROCEDURES: Blood samples were anticoagulated with hirudin. Aliquots of whole blood from each cat were allocated to 5 treatments (baseline, 50 µg of abciximab/mL, abciximab volumetric control treatment, 4 µM eptifibatide, and eptifibatide volumetric control treatment). Impedance platelet aggregometry was performed with 6.5 µM ADP or 32 µM thrombin receptor activator peptide (TRAP). Magnitude of platelet aggregation was determined by measuring the area under the curve 15 minutes after addition of ADP or TRAP. RESULTS: Eptifibatide caused a significant reduction in platelet aggregation, compared with baseline values, for aggregometry with both ADP (median, 50.0; range, 8 to 122 [baseline median, 306.0; baseline range, 130 to 664]) and TRAP (median, 75.5; range, 3 to 148 [baseline median, 219.0; baseline range, 97 to 578]). There was no significant difference in platelet aggregation with abciximab, the abciximab volumetric control treatment, or the eptifibatide volumetric control treatment for aggregometry with ADP or TRAP. CONCLUSIONS AND CLINICAL RELEVANCE: Eptifibatide caused a significant reduction in platelet aggregation in vitro, but there was no identifiable antiplatelet effect for abciximab. Eptifibatide and abciximab have different binding and inhibitory actions; therefore, it can be hypothesized that abciximab would be ineffective in cats because of a lack of receptor binding, reduced binding kinetics, or lack of downstream signaling. Eptifibatide may be useful in identifying hyperreactive platelets in cats in an in vitro platelet inhibitory assay.

In vitro effects of lipid emulsion on platelet function and thromboelastography in canine blood samples.

OBJECTIVE: To determine whether soybean oil emulsion has an in vitro effect on platelet aggregation and thromboelastography in blood samples obtained from healthy dogs. ANIMALS: 12 healthy adult dogs. PROCEDURES: Blood samples were collected from each dog into tubes containing EDTA, hirudin, or sodium citrate for a CBC, collagen- and ADP-induced impedance aggregometry, or thromboelastography, respectively. Whole blood platelet aggregation, determined with ADP or collagen agonists, was measured in blood samples containing hirudin and final lipid concentrations of 0, 1, 10, and 30 mg/mL. The thromboelastographic variables R (reaction time), K (clotting time), α angle, and maximum amplitude were evaluated in blood samples containing sodium citrate and final lipid concentrations equivalent to those used for assessment of platelet aggregation. RESULTS: Median maximum ADP- and collagen-induced platelet aggregation in blood samples containing 1, 10, or 30 mg of lipid/mL did not differ significantly from the value for the respective lipid-free blood sample. Maximum amplitude determined via thromboelastography was significantly reduced in blood samples containing 10 and 30 mg of lipid/mL, compared with findings for lipid-free blood samples. Values of other thromboelastographic variables did not differ, regardless of lipid concentrations. CONCLUSIONS AND CLINICAL RELEVANCE: Maximum amplitude determined via thromboelastography in canine blood samples was significantly affected by the addition of lipid to final concentrations that are several orders of magnitude higher than clinically relevant lipid concentrations in dogs. Lipid treatment appears to have no significant effect on hemostatic variables in dogs, although clinical studies should be performed to confirm these in vitro findings.

In vitro effect of pimobendan on platelet aggregation in dogs.

OBJECTIVE: To determine whether pimobendan has in vitro antithrombotic properties through inhibition of platelets in canine blood samples. ANIMALS: 10 healthy adult dogs. PROCEDURES: Blood samples were collected from each dog into tubes containing hirudin or sodium citrate. Pimobendan was added to blood samples (final concentration, 0.0, 0.01, 0.1, 1.0, or 10.0µM) containing hirudin prior to undergoing collagen- and ADP-induced whole blood impedance aggregometry. Plasma thromboxane concentrations were measured after platelet aggregation. Pimobendan was also added to blood samples (0.0, 0.01, or 10.0µM) containing sodium citrate prior to thromboelastographic evaluation. RESULTS: Compared with findings for 0.0µM pimobendan, composite platelet aggregation (area under the curve [AUC]) and maximal platelet aggregation (aggregation units [AUs]) at 10.0µM pimobendan were significantly decreased for collagen-induced aggregation (AUC, 349.7 ± 58.4 vs 285.1 ± 72.2; maximal platelet aggregation, 196.2 ± 25.8 AUs vs 161.5 ± 38.0 AUs), and the AUC and velocity of aggregation at 10.0µM pimobendan were significantly decreased for ADP-induced aggregation (AUC, 268.5 ± 35.1 vs 213.4 ± 77.2; velocity of aggregation, 15.7 ± 2.9 AUs/min vs 11.8 ± 3.5 AUs/min). Pimobendan had no significant effect on plasma thromboxane concentration or thromboelastographic variables, regardless of concentration. CONCLUSIONS AND CLINICAL RELEVANCE: In vitro, pimobendan had an antiplatelet effect in canine blood samples at a concentration 1,000-fold higher than that clinically achievable. These antiplatelet properties do not appear to contribute to the positive clinical profile of the drug in dogs. Pimobendan administration would not appear to confer a risk for bleeding and does not have to be avoided in dogs with thrombocytopenia or those concurrently receiving antiplatelet drugs.

Dose determination of fondaparinux in healthy cats.

OBJECTIVE: To establish practical doses and administration frequencies of fondaparinux for cats that would approximate human therapeutic peak and trough plasma anti-factor Xa activities for thromboprophylaxis (TP) and thrombosis treatment (TT) protocols. ANIMALS: 6 healthy adult purpose-bred cats. PROCEDURES: Dosage protocols for TP and TT were selected on the basis of a single compartment pharmacokinetic model incorporating data from humans but modified to account for the higher body weight-normalized cardiac output of cats. Fondaparinux was administered at 0.06 mg/kg, SC, every 12 hours (TP) for 7 days in one session, and 0.20 mg/kg, SC, every 12 hours (TT) for 7 days in another, with a minimum of 1 week separating the sessions. Plasma anti-factor Xa activity was measured before fondaparinux administration (day 1) and at 2 (peak) and 12 (trough) hours after drug administration on days 1 and 7. Platelet aggregation and thromobelastographic (TEG) parameters were also measured 2 hours after drug administration on day 7. RESULTS: Peak plasma anti-factor Xa activities on day 7 for TP (median, 0.59 mg/L; range, 0.36 to 0.77 mg/L) and TT (median, 1.66 mg/L; range, 1.52 to 2.00 mg/L) protocols were within therapeutic ranges for humans. However, only the TP protocol achieved trough anti-factor Xa activity considered therapeutic in humans (median, 0.19 mg/L; range, 0.00 to 0.37 mg/L) on day 7. There were significant changes in the TEG parameters at peak for the TT protocol, suggesting a hypocoagulable state. No significant changes in platelet aggregation were evident for either protocol. CONCLUSIONS AND CLINICAL RELEVANCE: A fondaparinux dosage of 0.06 or 0.20 mg/kg, SC, every 12 hours, was sufficient to achieve a peak plasma anti-factor Xa activity in cats that has been deemed therapeutic in humans. This study provided preliminary data necessary to perform fondaparinux dose-determination and clinical efficacy studies.

Use of transesophageal atrial pacing to provide temporary chronotropic support in a dog undergoing permanent pacemaker implantation.

A 14.5-kg, 13-year-old female spayed Cocker spaniel was evaluated because of episodic hind limb weakness. Results of examination were consistent with sick sinus syndrome with intermittent second-degree atrioventricular block. Transesophageal atrial pacing was successful in providing chronotropic support during permanent pacemaker implantation. Transesophageal atrial pacing appears to be a viable option for temporary atrial pacing in dogs with hemodynamically marked bradycardia without significant atrioventricular blockade.

Identification of low and high frequency ranges for heart rate variability and blood pressure variability analyses using pharmacological autonomic blockade with atropine and propranolol in swine.

Understanding autonomic nervous system functioning, which mediates behavioral and physiological responses to stress, offers great potential for assessing farm animal stress and welfare. Evaluation of heart rate variability (HRV) and blood pressure variability (BPV), using time and frequency domain analyses may provide a sensitive and reliable measure of affective states and stress-mediated changes in sympathetic and parasympathetic tones. The aim of this research was to define low (LF) and high frequency (HF) power spectral ranges using pharmacological autonomic blockade, and to examine HRV and BPV parameter changes in response to atropine and propranolol in swine. Ten, 13-week old, barrows (n=6) and gilts (n=4) underwent surgery to place an intra-cardiac electrode and a blood pressure catheter attached to a biotelemetric transmitter; pigs had a 3-week recovery period prior to data collection. Each pig was subjected to administration of 4 intravenous (i.v.) drug treatments: a control treatment, 3 mL of saline, and 3 blockade treatments; 0.1 mg/kg of atropine, 1.0 mg/kg of propranolol, and .1 mg/kg of atropine together with 1.0 mg/kg of propranolol. All treatments were delivered by injection in the jugular vein with a minimum of 48 h between individual treatments. Behavior, ECG and blood pressure data were recorded continuously for a total of 1h, from 30 min pre-injection to 30 min post-injection. For data analyses, two 512-beat intervals were selected for each treatment while the pig was lying and inactive. The first interval was selected from the pre-injection period (baseline), and the second was selected between 10 and 30 min post-injection. Time and frequency domain (power spectral density) analyses were performed on each data interval. Subsequent, LF and HF bands from the power spectral densities were defined based on general linear and regression analyses. The HRV and BPV were computed with a covariate (baseline) factorial analysis of treatment by sex interaction, and day of injection, with mixed models and Tukey's post-hoc tests. The best-fit range for LF was 0.0-0.09 Hz, and HF was 0.09-2.0 Hz (r²: 0.41 and 0.43, respectively). Propranolol and saline injections led to a greater overall total power and overall higher inter-beat interval, HF and LF power. Atropine led to a dominant sympathovagal balance of the cardiac activity in pigs. In addition, atropine led to an increase in LF power of both systolic and diastolic blood pressures in gilts suggesting vagal tone mediation of BPV. The understanding of autonomic regulation of HRV and BPV in domestic swine facilitates our ability to detect and quantify stress responses, and broadens its application in assessing farm animal welfare.

Efficacy of transesophageal and transgastric cardiac pacing in the dog.

OBJECTIVES: Determine if temporary artificial cardiac pacing can be accomplished from transesophageal or transgastric pacing sites. ANIMALS, MATERIALS AND METHODS: Nine purpose bred Beagle dogs had a multipolar electrophysiology pacing catheter inserted transnasally and advanced into the distal esophagus or stomach under general anesthesia. Artificial atrial pacing was attempted using a bipolar configuration from the distal esophagus with the dogs in left lateral recumbency. Artificial ventricular pacing was attempted from the distal esophagus and stomach using unipolar and bipolar configurations with the dogs in multiple positions. RESULTS: Transesophageal atrial pacing was accomplished in all dogs with a mean threshold of 10.5 mA (+ or - 3.9) and a 15 mm polar separation with no skeletal muscle stimulation. All attempts at transgastric and transesophageal ventricular pacing were unsuccessful. CONCLUSIONS: Transesophageal atrial pacing using standard cardiac pacing equipment is simple to perform and is a viable alternative to temporary transvenous or transthoracic pacing for supraventricular bradyarrhythmias without atrioventricular conduction disturbances. Transesophageal and transgastric ventricular pacing does not appear possible using the pacing configurations in this study.

Treatment of acute epistaxis secondary to guttural pouch mycosis with transarterial nitinol vascular occlusion plugs in three equids.

CASE DESCRIPTION: 2 horses and 1 pony were evaluated for right-sided (1 horse and the pony) and left-sided (1 horse) acute epistaxis of 1 day's to 1 month's duration. CLINICAL FINDINGS: Endoscopic examination of the 3 equids revealed that the hemorrhage originated from the right maxillary artery in 2 equids and from the left internal carotid artery in the third. Mycosis of the auditory tube diverticulum (guttural pouch) was detected in all 3 equids. TREATMENT AND OUTCOME: All 3 equids underwent surgery, and transarterial nitinol intravascular plugs were placed to occlude affected blood vessels. All equids survived for a long period (ie, a minimum of 1 to 2 years) and returned to their previous use. All had complete regression of clinical signs of guttural pouch mycosis without additional medical treatment. CLINICAL RELEVANCE: The use of transarterial nitinol intravascular plugs appeared to be an effective alternative to other techniques for the treatment of epistaxis secondary to guttural pouch mycosis, including transarterial occlusion devices such as embolization coils.

Safety of transesophageal pacing for 24 hours in a canine model.

BACKGROUND: Temporary epicardial pacing is often necessary following surgical correction of congenital heart disease. Epicardial pacing wires, while generally effective, can, however, become nonfunctional. Transesophageal atrial pacing (TEAP) can be a useful adjunct in this setting. The potential for esophageal damage with sustained TEAP is unknown. We assessed the safety of continuous (24 hours) TEAP by evaluating gross and histological changes to the esophagus in a canine model. METHODS: Thirteen juvenile beagle dogs were fitted with a 4-Fr multipolar catheter placed transnasally into the esophagus to a level to sustain atrial capture. Pacing was established in nine dogs for 24 hours while four control dogs had catheters but no pacing stimulus applied. Paced dogs were divided into two groups: group A (n = 5) that were euthanized immediately and group B (n = 4) that were euthanized 7 days after the pacing period. Nonpaced dogs (group C, n = 4) were treated similar to group A. Gross and histological examination of the esophageal tissue was completed. RESULTS: Gross and histological evidence of mild esophagitis was noted in dogs from groups A and C but not in dogs from group B. There was no evidence of esophageal stricture or fibrosis in any dog from any group. CONCLUSIONS: TEAP did not result in permanent esophageal changes after 24 hours of stimulation. Microscopic lesions of mild erosive esophagitis, seen after 24 hours of TEAP, were absent 7 days postpacing. Mechanical irritation from the catheter cannot be ruled out as a cause of these changes.

Utility of plasma N-terminal pro-brain natriuretic peptide (NT-proBNP) to distinguish between congestive heart failure and non-cardiac causes of acute dyspnea in cats.

BACKGROUND: Circulating plasma N-terminal pro-brain natriuretic peptide (NT-proBNP) concentration facilitates emergency diagnosis of congestive heart failure (CHF) in people. Its utility to discriminate between dyspneic cats with CHF vs. primary respiratory disease requires further assessment. Our objectives were to determine if NT-proBNP (1) differentiates dyspneic cats with CHF vs. primary respiratory disease; (2) increases with renal insufficiency; (3) correlates with left atrial dimension, radiographic cardiomegaly, and estimated left ventricular filling pressure (E/E(a)). METHODS: NT-proBNP was measured in 167 dyspneic cats (66 primary respiratory disease, 101 CHF) to evaluate (1) relationship with clinical parameters; (2) ability to distinguish CHF from primary respiratory disease; (3) optimal cut-off values using receiver operating characteristic (ROC) curve analysis. RESULTS: NT-proBNP (1) was higher (median and inter-quartile [25th-75th] percentile) in CHF (754 pmol/L; 437, 1035 pmol/L) vs. primary respiratory disease (76.5 pmol/L; 24, 180 pmol/L) cohorts (P<0.001); (2) positively correlated in CHF cats with increased inter-ventricular septal end-diastolic thickness (rho=0.266; P=0.007) and LV free wall thickness (rho=0.218; P=0.027), but not with radiographic heart size, left atrial size, left ventricular dimensions, E/E(a) ratio, BUN, creatinine, or thyroxine; (3) distinguished dyspneic CHF cats from primary respiratory disease at 265 pmol/L cut-off value with 90.2% sensitivity, 87.9% specificity, 92% positive predictive value, and 85.3% negative predictive value (area under ROC curve, 0.94). CONCLUSIONS: NT-proBNP accurately discriminated CHF from respiratory disease causes of dyspnea.

Cranial vena caval syndrome secondary to transvenous pacemaker implantation in two dogs.

Superior vena caval syndrome is a rare, but reported complication of transvenous pacemaker implantation in humans. This syndrome can occur secondary to fibrotic and/or thrombotic obstruction of venous blood flow into the right atrium. The therapeutic approach depends on the suspicion of the presence of an active thrombus and may include antithrombotics, angioplasty and/or surgical venoplasty. We describe two dogs that developed severe pleural effusion secondary to stricture formation in the cranial vena cava 4 years after dual chamber transvenous pacemaker implantation. The stenosis was most likely due to fibrosis secondary to the transvenous pacemaker leads. Balloon angioplasty of the lesion resulted in resolution of the pleural effusion in both patients. Balloon angioplasty appears to be a viable therapeutic approach in dogs with cranial vena caval syndrome caused by focal stenotic lesions.

Transcatheter closure of patent ductus arteriosus in a dog with a peripheral vascular occlusion device.

A 4-month-old, intact female mixed-breed dog presented to the Purdue University Veterinary Teaching Hospital for evaluation of a cardiac murmur. A large left-to-right patent ductus arteriosus (PDA) was diagnosed and interventional correction was achieved with a commercially available peripheral vascular occlusion device (VOD). The VOD is composed of a nitinol wire mesh and is similar in composition and shape to a commercially available human PDA occluder, however, it can be deployed through smaller delivery catheters and is much less expensive. The product and procedural details of the device are described.

Suspected iatrogenic paradoxical embolization in a cat.

A cat was evaluated for a 5-year history of progressive, episodic, exercise-induced cyanosis and panting. Diagnostic testing demonstrated tetralogy of Fallot with predominant right-to-left shunting and right-sided heart failure. Following diagnostic catheterization, the cat developed clinical signs consistent with systemic arterial thromboembolization and was euthanized. Necropsy findings included multiple thrombi within the right atrium and ventricle, and thromboemboli within the terminal aorta and right common carotid artery, a condition most consistent with iatrogenic paradoxical embolization secondary to diagnostic catheterization. Paradoxical embolization and thromboembolic complications of diagnostic catheterization are discussed.

Antiplatelet effects and pharmacodynamics of clopidogrel in cats.

OBJECTIVE: To evaluate antiplatelet effects and pharmacodynamics of clopidogrel in cats. DESIGN: Original study. ANIMALS: 5 purpose-bred domestic cats. PROCEDURE: Clopidogrel was administered at dosages of 75 mg, p.o., every 24 hours for 10 days; 37.5 mg, p.o., every 24 hours for 10 days; and 18.75 mg, p.o., every 24 hours for 7 days. In all cats, treatments were administered in this order, with at least 2 weeks between treatments. Platelet aggregation in response to ADP and collagen and oral mucosal bleeding times (OMBTs) were measured before and 3, 7, and 10 days (75 and 37.5 mg) or 7 days (18.75 mg) after initiation of drug administration. Serotonin concentration in plasma following stimulation of platelets with ADP or collagen was measured before and on the last day of drug administration. Platelet aggregation, OMBT, and serotonin concentration were evaluated at various times after drug administration was discontinued to determine when drug effects were lost. RESULTS: For all 3 dosages, platelet aggregation in response to ADP platelet aggregation in response to collagen, and serotonin concentration were significantly reduced and OMBT was significantly increased at all measurement times during drug administration periods. All values returned to baseline values by 7 days after drug administration was discontinued. No significant differences were identified between doses. None of the cats developed adverse effects associated with drug administration. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that administration of clopidogrel at dosages ranging from 18.75 to 75 mg, p.o., every 24 hours, results in significant antiplatelet effects in cats.