Presumptive vagally-mediated atrial flutter in a dog.

An asymptomatic nine-year-old Dobermann Pinscher underwent a screening for dilated cardiomyopathy. Echocardiography revealed left ventricular eccentric hypertrophy and systolic dysfunction; the rest of the echocardiographic parameters were within normal limits. Holter monitoring demonstrated sinus rhythm as the dominant cardiac rhythm during the first hours of the recording. Then, during a period of physiologically enhanced vagal tone (sleep), spontaneous development of atrial flutter (AFL) associated with variable ventricular response was documented. Alternation between AFL and paroxysmal atrial fibrillation was also observed. Subsequently, during a period of physiological increase of sympathetic tone (physical activity/excitement), spontaneous conversion of AFL to sinus rhythm occurred. In light of these findings, a presumptive diagnosis of vagal AFL was made. The images here described allow us to study the onset, behavior and termination of this intriguing electrocardiographic entity.

Preexcitation alternans in a dog.

Preexcitation alternans and orthodromic atrioventricular reciprocating tachycardia were diagnosed in a 3-month-old Boxer. The images described here show how conventional electrocardiographic techniques (12-lead surface electrocardiography, 24-hour Holter monitoring, and ladder diagram) can be interpreted to gain detailed information on presence of canine atrioventricular accessory pathways and their conduction properties.

Holter monitoring demonstrates that ventricular arrhythmias are common in cats with decompensated and compensated hypertrophic cardiomyopathy.

Arrhythmias can complicate cardiac disease in cats and are a potential cause of sudden death. The aim of this study was to evaluate the presence and nature of cardiac arrhythmias, and the potential correlation between plasma serum troponin I (cTnI) concentrations and the presence or severity of arrhythmias in cats with decompensated (dHCM) and compensated hypertrophic cardiomyopathy (cHCM). Forty one client-owned cats were studied: 16 with cHCM, 15 with dHCM and 10 healthy control cats. Physical examination, echocardiography, cTnI and 24-h Holter recordings were obtained in all cats and thoracic radiographs in cats with dHCM. Cats in both HCM groups were followed for 1 year after their initial Holter examination. The median (range) number of ventricular premature complexes (VPCs) over 24h was 867 (1-35,160) in cats with dHCM, 431 (0-18,919) in cats with cHCM and 2 (0-13) in healthy control cats. The median number of episodes of ventricular tachycardia (VTach) was 0 (0-1497) in dHCM and 0.5 (0-91) in cats with cHCM. The number of VPCs, VTach episodes and heart rate was not different between the HCM groups. Plasma serum troponin I was highest in the cats with dHCM, but there was no correlation between cTnI concentration and the number of arrhythmias. Thirteen of 31 cats with HCM died, but an association with the presence and complexity of ventricular arrhythmias was not observed. Compared to healthy cats, ventricular arrhythmias were common in cats with cHCM and dHCM, but neither presence nor complexity of arrhythmias could be linked to prognosis.

Cats with diabetes mellitus have diastolic dysfunction in the absence of structural heart disease.

Diabetes mellitus (DM) can result in cardiovascular dysfunction and heart failure characterized by diastolic dysfunction with or without the presence of systolic dysfunction in people and laboratory animals. The objective of this prospective study was to determine if cats with newly diagnosed DM had myocardial dysfunction and, if present, whether it would progress if appropriate antidiabetic therapy was commenced. Thirty-two diabetic cats were enrolled and received baseline echocardiographic examination; of these, 15 cats were re-examined after 6 months. Ten healthy age- and weight-matched cats served as controls. Diabetic cats at diagnosis showed decreased diastolic, but not systolic function, when compared to healthy controls, with lower mitral inflow E wave (E) and E/E' than controls. After 6 months, E and E/IVRT' decreased further in diabetic cats compared to the baseline evaluation. After excluding cats whose DM was in remission at 6 months, insulin-dependent diabetic cats had lower E, E/A and E' than controls. When classifying diastolic function according to E/A and E'/A', there was shift towards impaired relaxation patterns at 6 months. All insulin-dependent diabetic cats at 6 months had abnormal diastolic function. These results indicate that DM has similar effects on diastolic function in feline and human diabetics. The dysfunction seemed to progress rather than to normalize after 6 months, despite antidiabetic therapy. In cats with pre-existing heart disease, the development of DM could represent an important additional health risk.

Efficacy of pimobendan in the prevention of congestive heart failure or sudden death in Doberman Pinschers with preclinical dilated cardiomyopathy (the PROTECT Study).

BACKGROUND: The benefit of pimobendan in delaying the progression of preclinical dilated cardiomyopathy (DCM) in Dobermans is not reported. HYPOTHESIS: That chronic oral administration of pimobendan to Dobermans with preclinical DCM will delay the onset of CHF or sudden death and improve survival. ANIMALS: Seventy-six client-owned Dobermans recruited at 10 centers in the UK and North America. METHODS: The trial was a randomized, blinded, placebo-controlled, parallel group multicenter study. Dogs were allocated in a 1:1 ratio to receive pimobendan (Vetmedin capsules) or visually identical placebo. The composite primary endpoint was prospectively defined as either onset of CHF or sudden death. Time to death from all causes was a secondary endpoint. RESULTS: The proportion of dogs reaching the primary endpoint was not significantly different between groups (P = .1). The median time to the primary endpoint (onset of CHF or sudden death) was significantly longer in the pimobendan (718 days, IQR 441-1152 days) versus the placebo group (441 days, IQR 151-641 days) (log-rank P = 0.0088). The median survival time was significantly longer in the pimobendan (623 days, IQR 491-1531 days) versus the placebo group (466 days, IQR 236-710 days) (log-rank P = .034). CONCLUSION AND CLINICAL IMPORTANCE: The administration of pimobendan to Dobermans with preclinical DCM prolongs the time to the onset of clinical signs and extends survival. Treatment of dogs in the preclinical phase of this common cardiovascular disorder with pimobendan can lead to improved outcome.

English springer spaniels with significant bradyarrhythmias--presentation, troponin I and follow-up after pacemaker implantation.

OBJECTIVES: English springer spaniels (ESS) are one of the most frequently presented breeds for pacemaker implantation in the UK and may do so at an early age. In comparison to dogs of other breeds (non-ESS) presenting for pacemaker implantation, cardiac troponin I (cTnI), the outcome and survival of ESS were investigated. METHODS: Case records of dogs receiving pacemaker implantation were retrospectively reviewed. RESULTS: Between September 2004 and October 2008, 58 dogs were presented to the Small Animal Teaching Hospital, University of Liverpool for pacemaker implantation. ESS (n=10) was the second most commonly presented breed. ESS were significantly younger than non-ESS (P=0.022). cTnI values were elevated on presentation and a significant reduction was present after pacemaker implantation (P=0.008) in all dogs. No significant difference in initial cTnI was identified comparing ESS and non-ESS (P=0.45) and median survival times were similar (P=0.37). CLINICAL SIGNIFICANCE: ESS may be predisposed to bradyarrhythmias requiring pacemaker implantation. They present at a significantly younger age than non-ESS. Survival times between ESS and non-ESS were similar, despite ESS being paced at a younger age. However, pacemaker implantation is recommended in ESS, as median survival times of 30 months with a good quality of life were achieved.

Balloon valvuloplasty for treatment of pulmonic stenosis in English Bulldogs with an aberrant coronary artery.

BACKGROUND: English Bulldogs (EB) with pulmonic stenosis (PS) sometimes have an aberrant coronary artery (CA) type R2A encircling the pulmonary artery (PA). Balloon valvuloplasty (BV) is treatment of choice for severe PS, but is considered to be contraindicated in dogs with aberrant CA. HYPOTHESIS: Conservative BV in EB with aberrant CA is safe and improves clinical signs and quality of life. ANIMALS: Four client-owned EB with severe PS were retrospectively reviewed/analysed. METHODS: Retrospective study: Case records, echocardiography, BV, and follow-up investigations of EB diagnosed with severe PS and treated with BV were reviewed. The ratios of PA to aortic (Ao) velocity time integral (VTI) were calculated to assess progression/improvement of PS. RESULTS: An aberrant CA was confirmed on angiography in all EB. Conservative BV was performed, using a balloon of the size of the PA annulus or smaller (0.6-1 x PA annulus size). All dogs survived the procedure, but only a mild reduction in pressure gradient was achieved. There was an improvement in PA to Ao VTI in 3 of 4 dogs (P < or = .017), which were free of evidence of congestive heart failure (CHF) 5, 10, and 15 months after BV. One dog that had right-sided CHF when BV was performed died due to progressive right-sided CHF within 3 months. CONCLUSIONS: Conservative BV in EB might be safe and might improve quality and quantity of life.

Implantable loop recorders: a viable diagnostic tool in veterinary medicine.

OBJECTIVE: The purpose of this study was to investigate whether implantable loop recorders could be used in the diagnosis of unexplained collapse in dogs. METHODS: The medical records of six dogs presented to the University of Liverpool Small Animal Teaching Hospital between May 2003 and October 2006 for further evaluation of intermittent syncopal episodes, collapse or episodic weakness, were reviewed. All these dogs underwent standard investigations and had implantable loop recorders placed. RESULTS: A provisional diagnosis of supraventricular tachycardia was made in one dog, and diagnoses of exclusion of arrhythmogenic right ventricular cardiomyopathy and idiopathic epilepsy was made in two dogs. One dog suffered no further syncopal episodes, a diagnosis was not reached in another dog and the final dog was lost to follow-up. CLINICAL SIGNIFICANCE: The implantable loop recorder can be used successfully for the diagnosis of unexplained collapse in dogs.

Use of sodium nitroprusside in the anaesthetic protocol of a patent ductus arteriosus ligation in a dog.

Patent ductus arteriosus (PDA) is one of the most common congenital cardiac abnormalities in the dog. Sodium nitroprusside has been proposed as an infusion during PDA ligation as the resultant nitric oxide production causes hypotension thereby facilitating surgical dissection and decreasing the risk of haemorrhage. This case report details how the method described did not decrease blood pressure and therefore had no beneficial effects. It is speculated that the lack of response may have been due to tachyphylaxis. Other drugs may be preferred to induce deliberate hypotension in the dog.

Unusual vascular ring anomaly associated with a persistent right aortic arch in two dogs.

An unusual vascular ring anomaly consisting of a persistent right aortic arch and a left ligamentum arteriosum extending from the main pulmonary artery to an aberrant left subclavian artery and left aortic arch remnant complex was identified in a German shepherd dog and a great Dane. The left subclavian artery and left aortic arch remnant complex originated at the junction between the right distal aortic arch and the descending aorta and coursed dorsal to the oesophagus in a cranial direction. The attachment of the ligamentum arteriosum to the aberrant left subclavian artery was approximately 5 cm cranial to the point of origin of the aberrant left subclavian artery and left aortic arch remnant complex from the descending aorta in both dogs. This anomaly observed in both dogs is similar to an anomaly reported in humans, in which a persistent right aortic arch is found in conjunction with an aberrant left subclavian artery and a left aortic arch remnant (Kommerell's diverticulum). Surgical ligation and division of the left ligamentum arteriosum in both dogs, along with division of the left subclavian artery in the great Dane, resulted in resolution of clinical signs in both of the dogs in this report.

Investigation of QT-interval dispersion in the electrocardiogram of 81 dogs.

QT-interval dispersion (QT dispersion) is a marker of the inhomogeneity of ventricular repolarisation. In human beings an increase in QT dispersion has been linked to sudden death and arrhythmias in several cardiac diseases. In dogs it has yet to be evaluated, and this study aimed to establish a normal reference range for QT dispersion and to assess the effects of cardiac disease upon it. Ten-lead ECGS were recorded from 81 dogs at two hospitals; satisfactory traces were obtained from 68 dogs, 32 of them normal and 36 with cardiac disease. The mean (sd) QT dispersion was 20.8 (18.2 ms) and the mean heart rate-corrected QT dispersion was 26.1 (23.6 ms). There was no significant effect of cardiac disease. The accuracy of the results may be questioned owing to the identification of several potential errors in the measurements.