Direct current cardioversion in pregnancy: a multicentre study.

OBJECTIVE: Direct current cardioversion (DCCV) in pregnancy is rarely required and typically only documented in single case reports or case series. A recent UK confidential enquiry reported on several maternal deaths where appropriate DCCV appeared to have been withheld. DESIGN: Retrospective cohort study. SETTING: Seventeen UK and Ireland specialist maternity centres. SAMPLE: Twenty-seven pregnant women requiring DCCV in pregnancy. MAIN OUTCOME MEASURES: Maternal and fetal outcomes following DCCV. RESULTS: Twenty-seven women had a total of 29 DCCVs in pregnancy. Of these, 19 (70%) initial presentations were to Emergency Departments and eight (30%) to maternity settings. There were no maternal deaths. Seventeen of the women (63%) had a prior history of heart disease. Median gestation at DCCV was 28 weeks, median gestation at delivery was 35 weeks, with a live birth in all cases. The abnormal heart rhythms documented at the first cardioversion were atrial fibrillation in 12/27 (44%) cases, atrial flutter in 8/27 (30%), supraventricular tachycardia in 5/27 (19%) and atrial tachycardia in 2/27 (7%). Fetal monitoring was undertaken following DCCV on 14/29 (48%) occasions (10 of 19 (53%) at ≥26 weeks) and on 2/29 (7%) occasions, urgent delivery was required post DCCV. CONCLUSIONS: Direct current cardioversion in pregnancy is rarely required but should be undertaken when clinically indicated according to standard algorithms to optimise maternal wellbeing. Once the woman is stable post DCCV, gestation-relevant fetal monitoring should be undertaken. Maternity units should develop multidisciplinary processes to ensure pregnant women receive the same standard of care as their non-pregnant counterparts.

Implantable cardioverter-defibrillator therapy to reduce sudden cardiac death in adults with congenital heart disease: A registry study.

INTRODUCTION: The adult congenital heart disease (ACHD) population is rapidly expanding. However, a significant proportion of these patients suffer sudden cardiac death. Recommending implantable cardioverter-defibrillator (ICD) insertion requires balancing the need for appropriate therapy in malignant arrhythmia against the consequences of inappropriate therapy and procedural complications. Here we present long-term follow-up data for ICD insertion in patients with ACHD from a large Level 1 congenital cardiac center. METHODS AND RESULTS: All patients with ACHD undergoing ICD insertion over an 18-year period were identified. Data were extracted for baseline characteristics including demographics, initial diagnosis, ventricular function, relevant medication, and indication for ICD insertion. Details regarding device insertion were gathered along with follow-up data including appropriate and inappropriate therapy and complications. A total of 136 ICDs were implanted during this period: 79 for primary and 57 for secondary prevention. The most common congenital cardiac conditions in both groups were tetralogy of Fallot and transposition of the great arteries. Twenty-two individuals in the primary prevention group received appropriate antitachycardia pacing (ATP), 14 underwent appropriate cardioversion, 17 received inappropriate ATP, and 15 received inappropriate cardioversion. In the secondary prevention group, 18 individuals received appropriate ATP, 8 underwent appropriate cardioversion, 8 received inappropriate ATP, and 7 were inappropriately cardioverted. Our data demonstrate low complication rates, particularly with leads without advisories. CONCLUSION: ICD insertion in the ACHD population involves a careful balance of the risks and benefits. Our data show a significant proportion of patients receiving appropriate therapy indicating that ICDs were inserted appropriately.

Partial anomalous pulmonary venous drainage in patients presenting with suspected pulmonary hypertension: A series of 90 patients from the ASPIRE registry.

BACKGROUND AND OBJECTIVE: There are limited data regarding patients with PAPVD with suspected and diagnosed PH. METHODS: Patients with PAPVD presenting to a large PH referral centre during 2007-2017 were identified from the ASPIRE registry. RESULTS: Ninety patients with PAPVD were identified; this was newly diagnosed at our unit in 71 patients (78%), despite 69% of these having previously undergone CT. Sixty-seven percent had a single right superior and 23% a single left superior anomalous vein. Patients with an SV-ASD had a significantly larger RV area, pulmonary artery and L-R shunt and a higher % predicted DLCO (all P < 0.05). Sixty-five patients were diagnosed with PH (defined as mPAP ≥ 25 mm Hg), which was post-capillary in 24 (37%). No additional causes of PH were identified in 28 patients; 17 of these (26% of those patients with PH) had a PVR > 3 WU. Seven of these patients had isolated PAPVD, five of whom (8% of those patients with PH) had anomalous drainage of a single pulmonary vein. CONCLUSION: Undiagnosed PAPVD with or without ASD may be present in patients with suspected PH; cross-sectional imaging should therefore be specifically assessed whenever this diagnosis is considered. Radiological and physiological markers of L-R shunt are higher in patients with an associated SV-ASD. Although many patients with PAPVD and PH may have other potential causes of PH, a proportion of patients diagnosed with PAH have isolated PAPVD in the absence of other causative conditions.

Secundum atrial septal defect closure in adults in the UK.

AIMS: To examine determinants of access to treatment, outcomes and hospital utilization in patients undergoing secundum atrial septal defect (ASD) closure in adulthood in England and Wales. METHODS AND RESULTS: Large retrospective cohort study of all adult patients undergoing secundum ASD closures in England and Wales between 2000/01 and 2016/17. Data were from population-based official data sets covering congenital heart disease procedures, hospital episodes and death registries.Out of 6 541 index closures, 79.4% were transcatheter (median age 47 years, IQR 34-61) and 20.6% were surgical (40 years, 28-52). The study cohort was predominantly female (66%), with socio-ethnic profile similar to the general population.Mortality in hospital was 0.2% and at one year 1.0% (95%CI 0.8%-1.2%). Risk of death was lower for transcatheter repairs, adjusting for age, sex, year of procedure, comorbidities and cardiac risk factors (in-hospital adjusted-OR 0.09, 95%CI 0.02-0.46, one-year adjusted-HR 0.5, 0.3-0.9). There was excess mortality one year after ASD closure compared to matched population data.Median (IQR) peri-procedural length of stay was 1.8 (1.4-2.5) and 7.3 (6.2-9.2) days for transcatheter and surgical closures, respectively. Hospital resource use for cardiac reasons started the year before repair (median 2 inpatient and 2 outpatient-only days) and decreased post-repair (zero inpatient and one outpatient days during the first two years). CONCLUSION: This national study confirms that ASD closure in adults, by surgical or transcatheter methods, is provided independently of ethnic or socioeconomic differences, it is low (but not no) risk and appears to reduce future cardiac hospitalisation even in older ages.

Best practice recommendations for medically assisted reproduction in patients with known cardiovascular disease or at high risk of cardiovascular disease.

Increasing numbers of people are seeking assisted conception. In people with known cardiac disease or risk factors for cardiac disease, assisted conception may carry increased risks during treatment and any subsequent pregnancy. These risks should be assessed, considered and minimized prior to treatment.

Assisted reproduction in patients with cardiac disease: A retrospective review.

OBJECTIVE: To assess risks of assisted reproduction in patients with cardiac disease. STUDY DESIGN: Retrospective case note review of patients with cardiac disease undergoing ART over a 10 year period in the obstetric cardiac services of three UK tertiary centres. Assessment of maternal, obstetric and fetal complications during ART and resultant pregnancies. RESULTS: 34 patients with cardiac disease underwent 51 cycles of assisted reproduction. 24 patients (71%) received pre-pregnancy counselling. Mean age at the start of an assisted reproduction cycle was 32 years. Modified WHO (mWHO) risk category for the 34 patients was mWHO I, n = 3; mWHO II, n = 13; mWHO II- III, n = 10; mWHO III, n = 7; mWHO IV, n = 1. The 51 assisted reproduction cycles resulted in 31 pregnancies in 29 patients, and 31 live births, including two sets of twins. Live birth rate per cycle was 60.8%. Twin pregnancy rate per cycle was 5.8%. Four patients experienced complications during assisted reproduction treatment (7.8% per cycle); one major intra-abdominal haemorrhage following egg collection in a patient with a mechanical aortic valve, one endocarditis, one mild ovarian hyperstimulation syndrome and one vagal syncope during egg collection. Four other patients experienced cardiac complications during resultant pregnancies (12.9%). 43% of mWHO class III patients experienced cardiac, obstetric or neonatal complications. Five babies were delivered pre-term (<37/40). CONCLUSIONS: This small study demonstrates that assisted reproduction carries increased risks of complications in patients with cardiac disease, but can be undertaken without major complication in the majority, as long as appropriate adjustments to treatment pathways are made, and they are managed through a multi-disciplinary team.

Comparative analysis of surgical and percutaneous pulmonary valve implants over a 20-year period.

OBJECTIVES: Since percutaneous pulmonary valve implantation (PPVI) was introduced to prolong the lifetime of surgically placed right ventricular to pulmonary artery conduits, valve technology has evolved and the indications for PPVI expanded to native and larger right ventricular outflow tracts. We explore how indications, patient populations and outcomes compare to surgical pulmonary valve replacement (PVR). METHODS: This is a retrospective cohort study of PPVI and PVR procedures between 1998 and 2020 at a single UK centre. One hundred and twenty-eight patients underwent PPVI and 365 patients PVR. Primary outcome measures were survival, infective endocarditis and reintervention. RESULTS: The most common indication for PVR was replacement of the native pulmonary valve for pulmonary regurgitation whereas PPVI was more commonly used to treat pulmonary stenosis in a previously placed bioprosthetic conduit or valve. Treatment indications for PPVI expanded over the study to include the native right ventricular outflow tract. Survival was similar for PPVI and PVR (92% PPVI and 96.8% PVR at 5 years; 85.8% PPVI and 95.1% PVR at 10 years). Preprocedural New York Heart Association class 3 and 4 was the most important predictor of poor outcome. Annualized infective endocarditis rate was significantly higher for the Melody PPVI (0.024 vs 0.0024/person/year for PVR, P < 0.05). Both groups showed significant symptomatic improvement postprocedure with remodelling of ventricular volumes and improvement in cardiac output. Long-term follow-up for PVR showed half of patients will need replacement at 10-15 years post-index procedure. CONCLUSIONS: An increasing number of patients requiring PVR can now be treated percutaneously. A lifetime strategy for re-valving should be considered at the first valve implant.

Transfer of congenital heart patients from paediatric to adult services in England.

OBJECTIVE: This study assessed the transfer of patients from paediatric cardiac to adult congenital heart disease (ACHD) services in England and the factors impacting on this process. METHODS: This retrospective cohort study used a population-based linked data set (LAUNCHES QI data set: 'Linking Audit and National datasets in Congenital Heart Services for Quality Improvement') including all patients born between 1987 and 2000, recorded as having a congenital heart disease (CHD) procedure in childhood. Hospital Episode Statistics data identified transfer from paediatric to ACHD services between the ages of 16 and 22 years. RESULTS: Overall, 63.8% of a cohort of 10 298 patients transferred by their 22nd birthday. The estimated probability of transfer by age 22 was 96.5% (95% CI 95.3 to 97.7), 86.7% (95% CI 85.6 to 87.9) and 41.0% (95% CI 39.4 to 42.6) for severe, moderate and mild CHD, respectively. 166 patients (1.6%) died between 16 and 22 years; 42 of these (0.4%) died after age 16 but prior to transfer. Multivariable ORs in the moderate and severe CHD groups up to age 20 showed significantly lower likelihood of transfer among female patients (0.87, 95% CI 0.78 to 0.97), those with missing ethnicity data (0.31, 95% CI 0.18 to 0.52), those from deprived areas (0.84, 95% CI 0.72 to 0.98) and those with moderate (compared with severe) CHD (0.30, 95% CI 0.26 to 0.35). The odds of transfer were lower for the horizontal compared with the vertical care model (0.44, 95% CI 0.27 to 0.72). Patients who did not transfer had a lower probability of a further National Congenital Heart Disease Audit procedure between ages 20 and 30 compared with those who did transfer: 12.3% (95% CI 5.1 to 19.6) vs 32.5% (95% CI 28.7 to 36.3). CONCLUSIONS: Majority of patients with moderate or severe CHD in England transfer to adult services. Patients who do not transfer undergo fewer elective CHD procedures over the following decade.

Paraneoplastic hypercalcemia in a dog with benign renal angiomyxoma.

An 11-year-old, male, neutered crossbred Collie dog was presented for a history of polydipsia and polyuria. Diagnostic investigations revealed total and ionized hypercalcemia and an increased concentration of parathyroid hormone-related peptide. Abdominal ultrasonography and contrast-enhanced computed tomography of the abdomen revealed a right-sided, cystic-appearing renal mass. Cytological examination of ultrasound-guided aspirates of the mass revealed high numbers of spindle cells. The mass was removed en bloc via an ureteronephrectomy. Histopathological examination of the mass revealed neoplastic spindle cells in loosely packed and interlacing streams within a myxomatous stroma. Immunohistochemical examination with vimentin, von Willebrand Factor, and alpha-smooth muscle actin confirmed the mass to be a renal angiomyxoma. A minority of the neoplastic spindle cells showed positive cytoplasmic parathyroid hormone-related peptide immunostaining. The hypercalcemia resolved following surgery, and the parathyroid hormone-related peptide concentration returned to within the reference interval. The dog was no longer polydipsic or polyuric 1 year following surgery. The present report describes a previously unreported renal neoplasm causing paraneoplastic hypercalcemia and highlights the possibility of paraneoplastic hypercalcemia being caused by a benign neoplasm.

Implantable cardioverter-defibrillator therapy in adult patients with tetralogy of Fallot.

AIMS: Adults with repaired tetralogy of Fallot (TOF) are at risk of sudden cardiac death (SCD). ESC and AHA guidelines suggest the use of implantable cardioverter defibrillators (ICDs) to protect from this. Few data are available on the benefits of these devices in this population, and there are no randomized studies. METHODS AND RESULTS: We analysed outcomes with respect to death, ICD therapy delivery, and complications for 20 patients with repaired TOF and 39 dilated cardiomyopathy (DCM) patients followed up at a UK teaching hospital. All TOF patients had clinical ventricular tachycardia (VT), electrophysiological study-inducible VT, or previous arrest due to tachyarrhythmia and received dual-chamber devices with individualized atrial detection algorithms. Tetralogy of Fallot patients were younger than DCM patients, but follow-up duration was not different between the groups. Tetralogy of Fallot patients were more likely to have experienced oversensing (45 vs. 13%; P < 0.02), inappropriate anti-tachycardia pacing delivery (20 vs. 2%; P < 0.05), and inappropriate cardioversion (25 vs. 4%; P = 0.06) than DCM patients and less likely to receive appropriate therapies than DCM patients. The death rate in TOF patients was significantly lower than that in DCM patients (5 vs. 21%; P < 0.05). CONCLUSION: Tetralogy of Fallot patients have a higher risk of inappropriate therapies and other complications yet a lower incidence of appropriate therapies from their ICD than DCM patients. Further research into identification of factors predicting SCD in TOF and the benefits of ICD implantation is essential given the potential complications of ICD implantation in young congenital heart disease patients.

EDUCATIONAL SERIES IN CONGENITAL HEART DISEASE: Echocardiographic assessment of left to right shunts: atrial septal defect, ventricular septal defect, atrioventricular septal defect, patent arterial duct.

This review article will guide the reader through the basics of echocardiographic assessment of congenital left to right shunts in both paediatric and adult age groups. After reading this article, the reader will understand the pathology and clinical presentation of atrial septal defects (ASDs), ventricular septal defects (VSDs), atrioventricular septal defects (AVSDs) and patent arterial duct. Echocardiography is the mainstay in diagnosis and follow-up assessment of patients with congenital heart disease. This article will therefore describe the echocardiographic appearances of each lesion, and point the reader towards specific features to look for echocardiographically.

Spontaneous Septic Arthritis of Canine Elbows: Twenty-One Cases.

OBJECTIVE: This study provides information on clinical features, diagnosis, treatment and associated risk factors of spontaneous septic elbow arthritis in the dog. METHODS: Medical records between March 2007 and June 2015 were searched for cases of spontaneous septic elbow arthritis with a diagnosis based on clinical signs, arthrocentesis, cytological and microbiological analysis of elbow joint synovial fluid, radiography and outcome following treatment. RESULTS: Twenty-one cases of septic arthritis were identified. Pre-existing osteoarthritis was present in 14/15 elbows for which diagnostic imaging was available. Although all cases had increased neutrophil count on synovial fluid cytology, culture was only positive in 12/21. Despite initial improvement in lameness scores (pre-treatment 9/10 [range: 1-10] versus post-treatment 3/10 [range: 1-5]), 11/12 had residual long-term lameness. Recurrence of infection was noted in 3/12 elbows for which long-term (>8 weeks) follow-up was available. There was an acute mortality rate of 2/21 associated with severe systemic sepsis. CLINICAL SIGNIFICANCE: Septic arthritis, even in the absence of pyrexia, should be considered as a major differential diagnosis in middle aged, large breed dogs, with pre-existing elbow arthritis, that suffer an acute onset lameness, with elbow joint effusion and discomfort. Antibiotic therapy alone was effective for treatment with high initial response rates. Chronic lameness post-treatment was common, and a high rate of recurrence was seen with 3/12 dogs suffering more than one episode.

Aldosterone-producing adrenocortical carcinoma with myxoid differentiation in a cat.

A 10-year-old male neutered Persian cat was presented with an abdominal mass and history of weakness. Blood smear examination found marked elliptocytosis, and serum biochemical analysis revealed hypokalemia, hypochloremia, increased creatine kinase activity, and a high aldosterone concentration. Cytologic examination of the mass revealed neoplastic endocrine cells with moderate criteria of malignancy, favoring adrenocortical neoplasia. The adrenal mass was surgically excised and histologically characterized by lobules of mildly pleomorphic, polygonal neoplastic cells with moderate to abundant, occasionally granular, eosinophilic cytoplasm. Lobules were separated by fine fibrovascular trabeculae, and numerous cystic cavities containing amorphous eosinophilic material that stained positive with Alcian blue and periodic acid-Schiff were seen. Neoplastic cells were multifocally positive for cytochrome P450 aldosterone synthase. Based on clinicopathologic and immunohistochemical findings the present case was diagnosed as an aldosterone-producing adrenocortical carcinoma with myxoid differentiation. While this entity has not been reported in cats, myxoid differentiation of adrenocortical carcinomas has been found in other species and can pose a major diagnostic challenge on microscopic examination.

Haematology and coagulation profiles in cats with congenital portosystemic shunts.

Objectives The objectives of this study were, first, to report the haematological parameters and coagulation times for cats with a congenital portosystemic shunt (CPSS) and the influence of surgical shunt attenuation on these parameters; and, second, to identify any association between prolongation in coagulation profiles and incidence of perioperative haemorrhage. Methods This was a retrospective clinical study using client-owned cats with a CPSS. Signalment, shunt type (extra- or intrahepatic), degree of shunt attenuation (complete or partial), haematological parameters, prothrombin time (PT) and activated partial thromboplastin time (aPTT) test results, and occurrence of any perioperative clinical bleeding complications were recorded for cats undergoing surgical treatment of a CPSS at the Royal Veterinary College, UK, between 1994 and 2011. Results Forty-two cats were included. Thirty-six (85.7%) had an extrahepatic CPSS and six (14.3%) had an intrahepatic CPSS. Preoperatively, mean cell volume (MCV) and mean cell haemoglobin (MCH) were below the reference interval (RI) in 32 (76.2%) and 31 (73.8%) cats, respectively. Red blood cell count and mean cell haemoglobin concentration (MCHC) were above the RI in 10 (23.8%) and eight (19.1%) cats, respectively. Postoperatively, there were significant increases in haematocrit ( P = 0.044), MCV ( P = 0.008) and MCH ( P = 0.002). Despite the significant increase in MCV postoperatively, the median MCV postoperatively was below the RI, indicating persistence of microcytosis. Preoperatively, PT was above the upper RI in 14 cats (87.5%), and aPTT was above the upper RI in 11 cats (68.8%). No cat demonstrated a perioperative clinical bleeding complication. Conclusions and relevance Cats with a CPSS are likely to present with a microcytosis, but rarely present with anaemia, leukocytosis or thrombocytopenia. Surgical attenuation of the CPSS results in a significant increase in the HCT and MCV. Coagulation profiles in cats with a CPSS are likely to be prolonged, irrespective of shunt type, but do not appear to be associated with an increased risk of clinical bleeding.

Incorporating Comorbidity Within Risk Adjustment for UK Pediatric Cardiac Surgery.

BACKGROUND: When considering early survival rates after pediatric cardiac surgery it is essential to adjust for risk linked to case complexity. An important but previously less well understood component of case mix complexity is comorbidity. METHODS: The National Congenital Heart Disease Audit data representing all pediatric cardiac surgery procedures undertaken in the United Kingdom and Ireland between 2009 and 2014 was used to develop and test groupings for comorbidity and additional non-procedure-based risk factors within a risk adjustment model for 30-day mortality. A mixture of expert consensus based opinion and empiric statistical analyses were used to define and test the new comorbidity groups. RESULTS: The study dataset consisted of 21,838 pediatric cardiac surgical procedure episodes in 18,834 patients with 539 deaths (raw 30-day mortality rate, 2.5%). In addition to surgical procedure type, primary cardiac diagnosis, univentricular status, age, weight, procedure type (bypass, nonbypass, or hybrid), and era, the new risk factor groups of non-Down congenital anomalies, acquired comorbidities, increased severity of illness indicators (eg, preoperative mechanical ventilation or circulatory support) and additional cardiac risk factors (eg, heart muscle conditions and raised pulmonary arterial pressure) all independently increased the risk of operative mortality. CONCLUSIONS: In an era of low mortality rates across a wide range of operations, non-procedure-based risk factors form a vital element of risk adjustment and their presence leads to wide variations in the predicted risk of a given operation.

Improving Risk Adjustment for Mortality After Pediatric Cardiac Surgery: The UK PRAiS2 Model.

BACKGROUND: Partial Risk Adjustment in Surgery (PRAiS), a risk model for 30-day mortality after children's heart surgery, has been used by the UK National Congenital Heart Disease Audit to report expected risk-adjusted survival since 2013. This study aimed to improve the model by incorporating additional comorbidity and diagnostic information. METHODS: The model development dataset was all procedures performed between 2009 and 2014 in all UK and Ireland congenital cardiac centers. The outcome measure was death within each 30-day surgical episode. Model development followed an iterative process of clinical discussion and development and assessment of models using logistic regression under 25 × 5 cross-validation. Performance was measured using Akaike information criterion, the area under the receiver-operating characteristic curve (AUC), and calibration. The final model was assessed in an external 2014 to 2015 validation dataset. RESULTS: The development dataset comprised 21,838 30-day surgical episodes, with 539 deaths (mortality, 2.5%). The validation dataset comprised 4,207 episodes, with 97 deaths (mortality, 2.3%). The updated risk model included 15 procedural, 11 diagnostic, and 4 comorbidity groupings, and nonlinear functions of age and weight. Performance under cross-validation was: median AUC of 0.83 (range, 0.82 to 0.83), median calibration slope and intercept of 0.92 (range, 0.64 to 1.25) and -0.23 (range, -1.08 to 0.85) respectively. In the validation dataset, the AUC was 0.86 (95% confidence interval [CI], 0.82 to 0.89), and the calibration slope and intercept were 1.01 (95% CI, 0.83 to 1.18) and 0.11 (95% CI, -0.45 to 0.67), respectively, showing excellent performance. CONCLUSIONS: A more sophisticated PRAiS2 risk model for UK use was developed with additional comorbidity and diagnostic information, alongside age and weight as nonlinear variables.

Pulmonary cowpox in cats: five cases.

CASE SERIES SUMMARY: This case series documents five cases of pneumonia (with pleural effusion in three cases) caused by cowpox virus (CPxV) in domestic cats. Predisposition to pneumonia may have resulted from mixed infections in two cases (feline herpesvirus and Bordetella bronchiseptica in one cat, and Mycoplasma species in the other). RELEVANCE AND NOVEL INFORMATION: As well as diagnostic confirmation by previously described methods of virus isolation from skin lesions, and demonstration of pox virions in skin samples using electron microscopy and inclusion bodies in histological preparations, this is the first report of diagnosis by virus isolation from bronchoalveolar lavage fluid or pleural fluid, and demonstration of inclusion bodies in cytological preparations. This is also the first series to report treatment with interferon omega (IFN-ω). Two cats survived, both of which had been treated with IFN-ω. As CPxV represents a serious zoonotic risk it is an important differential diagnosis of pneumonia in cats.

Prevalence and risk factors for mast cell tumours in dogs in England.

BACKGROUND: Mast cell tumour (MCT) appears to be a frequent tumour type in dogs, though there is little published in relation to its frequency in dogs in the UK. The current study aimed to investigate prevalence and risk factors for MCTs in dogs attending English primary-care veterinary practices. METHODS: Electronic patient records from practices participating in the VetCompass animal surveillance project between July 2007 and June 2013 were searched for MCT diagnosis. Various search terms and standard diagnostic terms (VeNom codes) identified records containing MCT diagnoses, which were evaluated against clinical criteria for inclusion to the study. MCT prevalence for the entire dataset and specific breed types were calculated. Descriptive statistics characterised MCT cases and multivariable logistic regression methods evaluated risk factors for association with MCT (P < 0.05). RESULTS: Within a population of 168,636 dogs, 453 had MCT, yielding a prevalence of 0.27% (95% confidence interval (CI) 0.24% - 0.29%). The highest breed type specific prevalences were for the Boxer at 1.95% (95% CI 1.40% - 2.51%), Golden Retriever at 1.39% (0.98% - 1.81%) and Weimaraner at 0.85% (95% CI 0.17% to 1.53%). Age, insurance status, neuter status, weight and breed type were associated with MCT diagnosis. Of dogs of specific breed type, the Boxer, Pug and Staffordshire Bull Terrier showed greater odds of MCT diagnosis compared with crossbred dogs. Conversely, the German Shepherd Dog, Border Collie, West Highland White Terrier, Springer Spaniel and Cocker Spaniel had reduced odds of MCT diagnosis compared with crossbred dogs. No association was found between MCT diagnosis and sex. CLINICAL SIGNIFICANCE: This study highlights a clinically significant prevalence of MCT and identifies specific breed types with predisposition to MCT, potentially aiding veterinarian awareness and facilitating diagnosis.