J.R. Payne

Population characteristics and survival in 127 referred cats with hypertrophic cardiomyopathy (1997 to 2005)

OBJECTIVES To evaluate the characteristics and survival of a recent population of cats with hypertrophic cardiomyopathy. METHODS Records at the Royal Veterinary College Queen Mother Hospital for Animals were searched for cats diagnosed with hypertrophic cardiomyopathy between 1997 and 2005. Referring veterinarians and owners were contacted to determine survival times. RESULTS Cats with hypertrophic cardiomyopathy were evaluated for population characteristics (n=127) and survival times (n=109). Overall median survival from date of hypertrophic cardiomyopathy diagnosis at the Queen Mother Hospital for Animals was 1276 days. Cats with hypertrophic cardiomyopathy were younger (P=0·009), and more likely to be male (P<0·001) compared to a hospital control group (n=1473), and Ragdolls were over-represented (P<0·05). Characteristics associated with increased survival in univariate analysis included younger age (P=0·007), asymptomatic status (P<0·001), normal left atrial size (P<0·001) and presence of systolic anterior motion of the mitral valve (P=0·003). Systolic anterior motion was associated with asymptomatic status, and did not influence survival in asymptomatic cats or those in congestive heart failure. Age, left atrial size and breed were significantly associated with survival time in a multivariate analysis. CLINICAL SIGNIFICANCE Cats with hypertrophic cardiomyopathy and left atrial enlargement have a poorer prognosis. The positive influence of systolic anterior motion on survival is likely to be linked to its association with asymptomatic status.

Prognostic Indicators in Cats with Hypertrophic Cardiomyopathy

BACKGROUND Left atrial (LA) enlargement, congestive heart failure (CHF), and aortic thromboembolism (ATE) are associated with decreased survival in cats with hypertrophic cardiomyopathy (HCM), but the prognostic value of echocardiographic variables has not been well characterized. HYPOTHESIS/OBJECTIVES We hypothesized that LA echocardiographic variables and assessment of left ventricular (LV) diastolic and systolic function would have prognostic value in cats with HCM. ANIMALS Two hundred eighty-two cats diagnosed with HCM. METHODS Clinical and echocardiographic records of affected cats seen at the Royal Veterinary College from 2004 to 2009 were retrospectively analyzed. Only cats with echocardiographic confirmation of LV diastolic wall thickness ≥ 6 mm were included. Outcomes were obtained from clinical records or referring veterinarians and owners. RESULTS Deaths occurred in 164 cats, of which 107 were believed to have been cardiac deaths. Univariable predictors of an increased risk of cardiac death included older age, absence of a murmur, presence of a gallop sound or arrhythmia, presentation with either CHF or ATE, extreme LV hypertrophy (≥ 9.0 mm), LV fractional shortening (FS%) ≤ 30%, regional wall hypokinesis, increased left atrial size, decreased left atrial function, spontaneous echo-contrast/thrombus or both, absence of left ventricular outflow tract obstruction, and a restrictive diastolic filling pattern. Coxs proportional hazard analysis identified LA dysfunction, low LV systolic function, and extreme LV hypertrophy as independent predictors of decreased cardiac survival time. CONCLUSIONS AND CLINICAL IMPORTANCE Echocardiographic measurement of LA function, extreme LV hypertrophy, and LV systolic function provides important prognostic information in cats with HCM.

Comparison of auscultatory and echocardiographic findings in healthy adult cats.

OBJECTIVES This pilot study was performed to investigate murmur prevalence and to explore the association between auscultatory and echocardiographic findings in apparently healthy cats in order to design a larger study. ANIMALS, MATERIALS AND METHODS Adult cats in 4 rehoming centres were screened by auscultation and echocardiography (echo) over 2 periods of 2 weeks each. In the first period, echo was attempted only in cats with murmurs. In the second period, all cats underwent auscultation by 2 observers and echo. LVH was defined in 5 ways: maximal diastolic left ventricular (LV) wall thickness ≥ 6 mm or ≥ 5.5 mm with 2D (LVH(6 2D), LVH(5.5 2D), respectively) or M-Mode echo (LVH(6 MM) or LVH(5.5 MM) respectively), or LV wall thickness ≥ 6 mm (2D) for >50% of a wall segment (LVH(50%)). RESULTS 67/199 (34%) cats had a murmur. Interobserver agreement on murmur presence was moderate (κ 0.47). 61 cats with a murmur and 31 cats without underwent both auscultation and echo. Depending on the criteria, LVH was present in 31 (LVH(6 2D)), 21 (LVH(50%)) and 11 (LVH(6 MM)) scanned cats. 18-62% of cats with murmurs had LVH, depending on the echo criteria used. Agreement was best between observers in identifying LVH using LVH(6 2D) and LVH(50%) (κ = 1.0). CONCLUSIONS Heart murmurs are common in apparently healthy cats. The prevalence of LVH varies depending on the criteria used.

Cardiomyopathy prevalence in 780 apparently healthy cats in rehoming centres (the CatScan study)

OBJECTIVES Hypertrophic cardiomyopathy (HCM) appears to be common in cats and, based on pilot data, a prevalence of 15% has been hypothesized. The objectives were to screen a large population of apparently healthy adult cats for cardiac disease, and identify factors associated with a diagnosis of HCM. ANIMALS A total of 1007 apparently healthy cats ≥ 6 months of age. METHODS In this prospective, cross-sectional study, the inclusion criteria were: apparently healthy cats, aged ≥ 6 months, available for rehoming over a 17-month period from two rehoming centres. Hypertensive or hyperthyroid cats were excluded. Body weight, body condition score, auscultation, systolic blood pressure and two-dimensional (2-D) echocardiography were evaluated. Cats with left ventricular end-diastolic wall thickness ≥ 6 mm on 2-D echocardiography were considered to have HCM. RESULTS Complete data were obtained in 780 cats. Heart murmur prevalence was 40.8% (95% confidence interval (CI) 37.3-44.3%), 70.4% of which were considered functional. The prevalence of HCM was 14.7% (95% CI 12.3-17.4%), congenital disease 0.5% (95% CI 0.1-1.3%), and other cardiomyopathies 0.1% (95% CI 0.0-0.7%). The HCM prevalence increased with age. The positive predictive value of a heart murmur for indicating HCM was 17.9-42.6% (higher in old cats), and the negative predictive value was 90.2-100% (higher in young cats). The factors associated with a diagnosis of HCM in binary logistic regression models were male sex, increased age, increased body condition score and a heart murmur (particularly grade III/VI or louder). CONCLUSIONS Hypertrophic cardiomyopathy is common in apparently healthy cats, in contrast with other cardiomyopathies. Heart murmurs are also common, and are often functional.

Plasma Cardiac Troponin I Concentration and Cardiac Death in Cats with Hypertrophic Cardiomyopathy

Background The use of cardiac biomarkers to assist in the diagnosis of occult and symptomatic hypertrophic cardiomyopathy (HCM) in cats has been established. There is limited data describing their prognostic utility in cats with HCM. Hypothesis Circulating concentrations of N‐terminal B‐type natriuretic peptide (NTproBNP) and cardiac troponin I (cTnI) predict cardiac death in cats with HCM. Animals Forty‐one cats diagnosed with HCM at a veterinary teaching hospital, between February 2010 and May 2011. Methods Prospective investigational study. Plasma samples were collected from cats diagnosed with HCM and concentrations of NTproBNP and cTnI were analyzed at a commercial laboratory. Echocardiographic measurements from the day of blood sampling were recorded. Long‐term outcome data were obtained. Associations with time to cardiac death were analyzed using Cox proportional hazards models. Results When controlling for the presence/absence of heart failure and echocardiographic measures of left atrial size and function, cTnI > 0.7 ng/mL was independently associated with time to cardiac death. In univariable analysis, NTproBNP > 250 pmol/L was associated with cardiac death (P = .023), but this did not remain significant (P = .951) when controlling for the effect of clinical signs or left atrial size/function. Conclusions and Clinical Importance Plasma concentration of cTnI (cutoff >0.7 ng/mL) is a predictor of cardiac death in cats with HCM that is independent of the presence of heart failure or left atrial dilatation.

Arterial Thromboembolism in 250 Cats in General Practice: 2004–2012

Background Population characteristics and outcome of cats with arterial thromboembolism (ATE) managed in general practice (GP) have been poorly described. Hypothesis Cats with ATE presenting to GP are usually euthanized at presentation, but survival times >1 year are possible. Animals Cats with ATE managed by 3 GP clinics in the United Kingdom. Methods Records of cases presenting to GP over a 98‐month period (2004–2012) were reviewed. Cats with an antemortem diagnosis of limb ATE were included. Outcome information was obtained. Results Over 98 months, 250 cats were identified with ATE. Prevalence was approximately 0.3%. At presentation, 153 cats (61.2%) were euthanized, with 68/97 (70.1%) of the remaining cats (27.2% of the total population) surviving >24 hours after presentation. Of these, 30/68 (44.1%) survived for at least 7 days. Hypothermia (HR, 1.44; 95% CI, 1.002–2.07; P = .049) and management by Clinic 2 (HR, 5.53; 95% CI, 1.23–24.8; P = .026) were independent predictors of 24‐hour euthanasia or death. For cats surviving >24 hours, hypothermia (HR, 2.25; 95% CI, 1.12–4.48; P = .021) and failure to receive aspirin, clopidogrel, or both (HR, 8.26; 95% CI, 1.39–50; P = .001) were independent predictors of euthanasia or death within 7 days. For cats that survived ≥7 days, median survival time was 94 (95% CI, 42–164) days, with 6 cats alive 1 year after presentation. Conclusions Although 153/250 cats were euthanized at presentation, 6 cats survived >12 months. No factors were identified that predicted euthanasia on presentation.

Risk factors associated with sudden death vs. congestive heart failure or arterial thromboembolism in cats with hypertrophic cardiomyopathy.

OBJECTIVES To evaluate risk factors associated with different types of cardiac death in cats with hypertrophic cardiomyopathy (HCM). ANIMALS Two hundred fifty-five cats with HCM referred to a veterinary teaching hospital. METHODS This is a retrospective study. Cats with HCM were identified that had either died within 2 years of diagnosis or were known to be alive 2 years after initial examination. Signalment, physical exam, electrocardiographic and echocardiographic data were analyzed separately for association with death due to congestive heart failure (CHF) vs. aortic thromboembolism (ATE) vs. sudden death. RESULTS Within 2 years of follow-up, 23/255 (9.0%) cats had died with ATE, 44/255 (17.3%) cats had died with CHF and 12/255 (4.7%) cats had experienced a sudden death, with 141/255 (55.3%) cats still alive at the end of 2 years. Presence of CHF at presentation and reduced left ventricular fractional shortening (FS%) were independently associated with a CHF death within 2 years of diagnosis. Presence of ATE and reduced left atrial fractional shortening (LA-FS%) were independently associated with dying with ATE within 2 years. No multivariable models were generated for risks of dying a sudden death owing to the low event rate, but syncope at presentation and arrhythmias on auscultation were associated with sudden death on univariable analysis. CONCLUSIONS Asymptomatic cats have a reduced risk of all three types of death. Reduced FS% and a history of CHF independently predict CHF death, and reduced LA-FS% and history of ATE independently predict ATE death. Sudden death is less commonly reported but is associated with syncope.

Familial cardiomyopathy in Norwegian Forest cats

Norwegian Forest cats (NFCs) are often listed as a breed predisposed to cardiomyopathy, but the characteristics of cardiomyopathy in this breed have not been described. The aim of this preliminary study was to report the features of NFC cardiomyopathy based on prospective echocardiographic screening of affected family groups; necropsy findings; and open-source breed screening databases. Prospective examination of 53 NFCs revealed no murmur or left ventricular (LV) outflow tract obstruction in any screened cat, though mild LV hypertrophy (defined as diastolic LV wall thickness ≥5.5mm) was present in 13/53 cats (25%). Gross pathology results and histopathological sections were analysed in eight NFCs, six of which had died of a cardiac cause. Myocyte hypertrophy, myofibre disarray and interstitial fibrosis typical of hypertrophic cardiomyopathy were present in 7/8 cats, but endomyocardial fibrosis suggestive of restrictive cardiomyopathy was also present in the same cats. Pedigree data analysis from 871 NFCs was supportive of a familial cardiomyopathy in this breed.

Mitral Annular Plane Systolic Excursion and Tricuspid Annular Plane Systolic Excursion in Cats with Hypertrophic Cardiomyopathy

Background Left ventricular (LV) systolic dysfunction is associated with increased risk of death in cats with hypertrophic cardiomyopathy (HCM). Mitral and tricuspid annular plane systolic excursion (MAPSE and TAPSE, respectively) are measures of longitudinal systolic function and are reduced in human patients with HCM. Hypotheses Cats with HCM have lower MAPSE and TAPSE compared to control cats; lower MAPSE and TAPSE are associated with the presence of congestive heart failure (CHF) and reduced survival time. Animals 64 cats with HCM and 27 healthy cats. Forty‐five cats with HCM were not showing clinical signs, and 19 had CHF. Methods Retrospective study. Anatomic M‐mode from the left apical 4‐chamber view was used to record MAPSE from the free wall (MAPSE FW) and septum (MAPSE IVS) and TAPSE. Results Compared to controls, cats with HCM had lower MAPSE IVS (controls 5.2 [4.6–5.6] mm, asymptomatic HCM 4.7 [4.1–5.2] mm, HCM with CHF 2.6 [2.5–3.2] mm, P < .001), MAPSE FW (controls 5.9 [5.3–6.2] mm, asymptomatic HCM 4.7 [4.1–5.1] mm, HCM with CHF 2.8 [2.4–3.2] mm) and TAPSE (controls 8.6 [7.4–10.2] mm, asymptomatic HCM 7.2 [6.3–8.2] mm, HCM with CHF 4.6 [4.1–5.4] mm), with the lowest in the CHF group. Univariate survival analysis showed a shorter survival in cats displaying lower MAPSE IVS, MAPSE FW, and TAPSE. Conclusions and Clinical Importance MAPSE and TAPSE were lower in cats with HCM than in control cats and were lowest in CHF, suggesting that systolic longitudinal dysfunction is present in cats with HCM. MAPSE and TAPSE have potential prognostic significance.

Blood Pressure Measurements in 780 Apparently Healthy Cats.

Background Mean systolic blood pressure in apparently healthy cats has been reported as approximately 125 mmHg using direct assessment, but there is greater variability in reported values using indirect assessment. Increasing age and the white‐coat effect are associated with increased systolic blood pressure. Hypothesis/Objectives To report Doppler‐derived blood pressure measurements from a large population of apparently healthy cats and to assess epidemiologic factors associated with recorded blood pressures. Animals A total of 780 cats in rehoming centers enrolled in a screening program for heart murmurs and cardiac disease. Methods Cats were considered healthy based on history and physical examination. Cats with known hypertension, hyperthyroidism, or clinical signs of systemic disease and pregnant or nursing queens were excluded. After an acclimatization period, systolic blood pressure was measured using the Doppler sphygmomanometry method following the recommendations of the ACVIM Consensus Statement. General linear model analysis was performed to identify factors associated with variation in systolic blood pressure. Results Median (interquartile range, IQR) systolic blood pressure for the group was 120.6 (110.4–132.4) mmHg. Factors significantly associated with higher systolic blood pressure in a general linear model were increased age, increased nervousness, male sex, neutering, or history of being a stray. The model explained 29.2% of the variation in systolic blood pressure. Conclusions and Clinical Importance The age, demeanor, sex, neuter status and history of being a stray should be taken into account when assessing systolic blood pressure in apparently healthy cats.