Anna Tidholm

Prevalence of myocardial hypertrophy in a population of asymptomatic Swedish Maine coon cats.

BackgroundMaine coon cats have a familial disposition for developing hypertrophic cardiomyopathy (HCM) with evidence of an autosomal dominant mode of inheritance [1]. The current mode to diagnose HCM is by use of echocardiography. However, definite reference criteria have not been established. The objective of the study was to determine the prevalence of echocardigraphic changes consistent with hypertrophic cardiomyopathy in Swedish Maine coon cats, and to compare echocardiographic measurements with previously published reference values.MethodsAll cats over the age of 8 months owned by breeders living in Stockholm, listed on the website of the Maine Coon breeders in Sweden by February 2001, were invited to participate in the study. Physical examination and M-mode and 2D echocardiographic examinations were performed in all cats.ResultsExaminations of 42 asymptomatic Maine coon cats (10 males and 32 females) were performed. The age of the cats ranged from 0,7 to 9,3 years with a mean of 4,8 ± 2,3 years. Four cats (9,5%) had a diastolic interventricular septal (IVSd) or left ventricular free wall (LVPWd) thickness exceeding 6,0 mm. In 3 of these cats the hypertrophy was segmental. Two cats (4,8%) had systolic anterior motion (SAM) of the mitral valve without concomitant hypertrophy. Five cats (11,9%) had IVSd or LVPWd exceeding 5,0 mm but less than 6,0 mm.ConclusionDepending on the reference values used, the prevalence of HCM in this study varied from 9,5% to 26,2%. Our study suggests that the left ventricular wall thickness of a normal cat is 5,0 mm or less, rather than 6,0 mm, previously used by most cardiologists. Appropriate echocardiographic reference values for Maine coon cats, and diagnostic criteria for HCM need to be further investigated.

Tissue Doppler and Strain Imaging in Dogs with Myxomatous Mitral Valve Disease in Different Stages of Congestive Heart Failure

BACKGROUND Tissue Doppler imaging (TDI) including strain and strain rate (SR) assess systolic and diastolic myocardial function. HYPOTHESIS TDI, strain, and SR variables of the left ventricle (LV) and the interventricular septum (IVS) differ significantly between dogs with myxomatous mitral valve disease (MMVD) with and without congestive heart failure (CHF). ANIMALS Sixty-one dogs with MMVD with and without CHF. Ten healthy control dogs. METHODS Prospective observational study. RESULTS Radial motion: None of the systolic variables were altered and 3 of the diastolic velocities were significantly increased in dogs with CHF compared with dogs without CHF and control dogs. Longitudinal motion: 2 systolic velocities and 3 diastolic velocities were significantly increased in dogs with CHF compared with dogs without CHF and control dogs. Difference in systolic velocity time-to-peak between LV and IVS was significantly increased in dogs with MMVD with and without CHF compared with control dogs. In total, 11 (23%) of 48 TDI and strain variables differed significantly between groups. Left atrial to aortic ratio was positively correlated to early diastolic velocities, percentage increase in left ventricular internal diameter in systole was positively correlated to systolic and diastolic velocities, and mitral E wave to peak early diastolic velocity in the LV basal segment (E/Em) was positively correlated to radial strain and SR. CONCLUSIONS AND CLINICAL IMPORTANCE Few TDI and strain variables were changed in dogs with MMVD with and without CHF. Intraventricular dyssynchrony may be an early sign of MMVD or may be an age-related finding.

Assessment of global and regional left ventricular volume and shape by real-time 3-dimensional echocardiography in dogs with myxomatous mitral valve disease.

BACKGROUND Left ventricular (LV) remodeling occurs in response to chronic volume overload. Real-time 3-dimensional (RT3D) echocardiography offers new modalities for LV assessment. OBJECTIVE To investigate LV changes in shape and volume in response to different severities of naturally acquired myxomatous mitral valve disease (MMVD) in dogs by RT3D echocardiography. ANIMALS Sixty-five client-owned dogs. METHODS Prospectively recruited dogs were classified by standard echocardiography into healthy, mild, moderate, and severe MMVD groups. Endocardial border tracking of LV RT3D dataset was performed, from which global and regional (automatically acquired basal, mid, and apical segments based on LV long-axis length) end-diastolic (EDV) and end-systolic volumes (ESV), LV long-axis length, and sphericity index were obtained. RESULTS Global and regional EDV and ESV (indexed to body weight) were most prominently increased in dogs with severe MMVD. All 3 regional LV segments contributed to increased global EDV and ESV with increasing MMVD severity, but mid-EDV contributed the most to the global EDV increase. Furthermore, LV long-axis length and LV sphericity index increased with increasing MMVD severity. Basal and apical EDV segments displayed the strongest association with sphericity index (P < .0001). CONCLUSIONS AND CLINICAL IMPORTANCE The most prominent LV volume expansion was found in dogs with severe MMVD. Increased EDV, primarily in the mid-segment, leads to rounding of LV apical and basal segments in response to increasing MMVD severity. Assessment of LV volume and shape potentially could allow early detection of dogs at risk for rapid progression into congestive heart failure.

Effect of Pimobendan in Dogs with Preclinical Myxomatous Mitral Valve Disease and Cardiomegaly: The EPIC Study—A Randomized Clinical Trial

Background Pimobendan is effective in treatment of dogs with congestive heart failure (CHF) secondary to myxomatous mitral valve disease (MMVD). Its effect on dogs before the onset of CHF is unknown. Hypothesis/Objectives Administration of pimobendan (0.4–0.6 mg/kg/d in divided doses) to dogs with increased heart size secondary to preclinical MMVD, not receiving other cardiovascular medications, will delay the onset of signs of CHF, cardiac‐related death, or euthanasia. Animals 360 client‐owned dogs with MMVD with left atrial‐to‐aortic ratio ≥1.6, normalized left ventricular internal diameter in diastole ≥1.7, and vertebral heart sum >10.5. Methods Prospective, randomized, placebo‐controlled, blinded, multicenter clinical trial. Primary outcome variable was time to a composite of the onset of CHF, cardiac‐related death, or euthanasia. Results Median time to primary endpoint was 1228 days (95% CI: 856–NA) in the pimobendan group and 766 days (95% CI: 667–875) in the placebo group (P = .0038). Hazard ratio for the pimobendan group was 0.64 (95% CI: 0.47–0.87) compared with the placebo group. The benefit persisted after adjustment for other variables. Adverse events were not different between treatment groups. Dogs in the pimobendan group lived longer (median survival time was 1059 days (95% CI: 952–NA) in the pimobendan group and 902 days (95% CI: 747–1061) in the placebo group) (P = .012). Conclusions and Clinical Importance Administration of pimobendan to dogs with MMVD and echocardiographic and radiographic evidence of cardiomegaly results in prolongation of preclinical period and is safe and well tolerated. Prolongation of preclinical period by approximately 15 months represents substantial clinical benefit.

Blood Pressure, Heart Rate, and Urinary Catecholamines in Healthy Dogs Subjected to Different Clinical Settings

BACKGROUND Correct interpretation of blood pressure (BP) and heart rate (HR) recordings is important in a clinical environment, but little is known about effects of stress on BP and HR responses of dogs to different clinical settings. OBJECTIVE To investigate BP and HR responses in different clinical settings in dogs of 3 breeds, and to relate findings to urinary catecholamine concentrations measured by ELISA assays previously validated for use in human plasma and urine, after validation for use in dogs. ANIMALS Client-owned healthy dogs; 41 Labrador Retrievers, 33 Cavalier King Charles Spaniels (CKCS), and 15 Dachshunds. METHODS Prospective observational study. BP and HR were measured in 4 clinical settings with or without veterinarian and owner present. Urine samples were taken before and after examination. ELISA assays were validated for canine urine, and epinephrine/creatinine and norepinephrine/creatinine ratios were analyzed. RESULTS BP and HR were higher when measured by veterinarian alone than when owner was present (P < .020). Urinary catecholamine/creatinine ratios were higher after examination, compared with before, in all dogs (P < .0001). Labrador Retrievers had lower diastolic BP than Dachshunds in 2 settings (P ≤ .041), lower HR than CKCSs in 3 settings (all P < .0001), and lower catecholamine/creatinine ratios after examination than both other breeds (P ≤ .035). The in-house validation showed mean spiked recovery of 96.5% for epinephrine and 83.8% for norepinephrine. CONCLUSIONS AND CLINICAL IMPORTANCE BP and HR responses were related to breed as well as clinical setting. Breed differences were detected in urinary catecholamine/creatinine ratios. Further studies on breed differences are warranted.

Serum serotonin concentration is associated with severity of myxomatous mitral valve disease in dogs.

BACKGROUND The neurotransmitter serotonin (5-hydroxytryptamine, 5-HT) has recently been suggested to play a role in the development of naturally acquired myxomatous mitral valve disease (MMVD) in dogs. AIM To investigate the association between serum 5-HT concentration and MMVD severity in dogs, and to assess potential associations between serum 5-HT concentrations and dog characteristics, echocardiographic variables, heart rate, systolic blood pressure, presence of macrothrombocytosis, and plateletcrit. ANIMALS A total of 120 client-owned dogs. MATERIAL AND METHODS Dogs were prospectively recruited and were classified by standard echocardiography into healthy (dogs of breeds predisposed to MMVD, but without echocardiographic evidence of the disease), mild, moderate, or severe MMVD groups. Serum 5-HT concentrations were analyzed using an ELISA. RESULTS Dogs with severe MMVD had lower serum 5-HT concentrations than healthy dogs (P = .0025) and dogs with mild MMVD (P = .0011). Unilinear and multiple regression analyses showed that serum 5-HT concentrations decreased with increasing left atrial to aortic root ratio (LA/Ao), were higher in Cavalier King Charles Spaniel (CKCS) dogs compared to dogs of other breeds, and were higher in female dogs than in male dogs. The LA/Ao was the variable most strongly associated with serum 5-HT concentration. CONCLUSIONS AND CLINICAL IMPORTANCE The finding of higher serum 5-HT concentrations in dogs of breeds predisposed to the early onset of MMVD (CKCS) and dogs with mild MMVD suggests that alterations in 5-HT signaling might play a role in progression of early stages of MMVD.

Comparisons of 3‐, 2‐Dimensional, and M‐Mode Echocardiographical Methods for Estimation of Left Chamber Volumes in Dogs with and without Acquired Heart Disease

BACKGROUND Real-time 3-dimensional echocardiography (RT3D) is a recent technique based on volumetric scanning, eliminating the need for geometric modeling of the cardiac chambers and minimizing the errors caused by foreshortened views. HYPOTHESIS Estimations of left ventricular (LV) end-diastolic (EDV) and end-systolic volume (ESV), and left atrial (LA) size, differ depending on the echocardiographic technique of estimation. ANIMALS Fifty-one dogs with acquired heart disease and 34 healthy control dogs. METHODS Prospective observational study by M-mode (Teichholz method), Simpsons modified 2-dimensional (2D) method, and RT3D methods for estimation of LV volumes. LA size was evaluated by 2D and RT3D methods. RESULTS RT3D showed good agreement with 2D for EDV and ESV, whereas Teichholz method overestimated LV volumes in comparison with the other 2 methods by approximately a factor 2. There were no statistically significant differences among the 3 methods in estimating ejection fraction. Comparison between RT3D assessment of LA end-systolic volume per kilogram (LAs/kg) and LA to aortic ratio (LA/Ao) measured by 2D relative to each other showed that the RT3D method underestimated LAs/kg at lower values, and overestimated it at higher values. The difference between methods increased with increasing LA size. CONCLUSIONS AND CLINICAL IMPORTANCE There was good agreement between RT3D and 2D methods of estimating EDV and ESV, whereas the Teichholz method overestimated LV volumes by approximately a factor 2. In comparison with RT3D, LA/Ao underestimated LA size, especially when LA was enlarged.

Longitudinal Analysis of Quality of Life, Clinical, Radiographic, Echocardiographic, and Laboratory Variables in Dogs with Myxomatous Mitral Valve Disease Receiving Pimobendan or Benazepril: The QUEST Study

BACKGROUND Myxomatous mitral valve disease (MMVD) is an important cause of morbidity and mortality in dogs. OBJECTIVES To compare, throughout the period of follow-up of dogs that had not yet reached the primary endpoint, the longitudinal effects of pimobendan versus benazepril hydrochloride treatment on quality-of-life (QoL) variables, concomitant congestive heart failure (CHF) treatment, and other outcome variables in dogs suffering from CHF secondary to MMVD. ANIMALS A total of 260 dogs in CHF because of MMVD. METHODS A prospective single-blinded study with dogs randomized to receive pimobendan (0.4-0.6 mg/kg/day) or benazepril hydrochloride (0.25-1.0 mg/kg/day). Differences in outcome variables and time to intensification of CHF treatment were compared. RESULTS A total of 124 dogs were randomized to pimobendan and 128 to benazepril. No difference was found between groups in QoL variables during the trial. Time from inclusion to 1st intensification of CHF treatment was longer in the pimobendan group (pimobendan 98 days, IQR 30-276 days versus benazepril 59 days, IQR 11-121 days; P = .0005). Postinclusion, dogs in the pimobendan group had smaller heart size based on VHS score (P = .013) and left ventricular diastolic (P = .035) and systolic (P = .0044) dimensions, higher body temperature (P = .030), serum sodium (P = .0027), and total protein (P = .0003) concentrations, and packed cell volume (P = .030). Incidence of arrhythmias was similar in treatment groups. CONCLUSIONS AND CLINICAL IMPORTANCE Pimobendan versus benazepril resulted in similar QoL during the study, but conferred increased time before intensification of CHF treatment. Pimobendan treatment resulted in smaller heart size, higher body temperature, and less retention of free water.

Comparisons of 2- and 3-dimensional echocardiographic methods for estimation of left atrial size in dogs with and without myxomatous mitral valve disease.

BACKGROUND Two-dimensional (2D) and real-time three-dimensional (RT3D) echocardiography can be used to assess left atrial (LA) size, but their correlation in dogs remains unknown. HYPOTHESIS Estimations of LA size differ depending on the echocardiographic technique. ANIMALS Privately owned dogs; 70 with myxomatous mitral valve disease and 32 healthy control dogs. METHODS Prospective observational study comparing RT3D volume at atrial end-diastole (RT3DLAd) with 4 different 2D methods of estimating LA size: LA diameter and area in short-axis (LA(sax) and LA(area)) and LA diameter in long-axis (LA(lax)), both as indexed variables and as predictors of LA volume indexed to body weight (BW) using allometric scaling and geometric assumption of sphericity. Furthermore, agreement between indexed 2D based methods was studied using concordance correlation coefficient (ρ(c)) and Bland-Altman plots. RESULTS None of the indexed 2D methods of estimating LA size showed good correlation with BW-indexed RT3DLAd volumes. Estimates of LA volumes from 2D measurements using allometric scaling showed better correlation with RT3D volumes than corresponding calculated volume approximations. The best correlation was found between RT3DLAd and estimated LA volumes based on allometric scaling of LA(lax) (ρ(c) = 0.89) followed by LA(area) (ρ(c) = 0.86) measurements. Comparing indexed 2D-based measurements of LA size, best agreement was found between LA(sax) to aortic diameter and LA(sax) to expected LA diameter, based on allometric scaling. CONCLUSIONS AND CLINICAL IMPORTANCE Allometric scaling of 2D-based measurements of LA showed good correlation with RT3DLAd, whereas corresponding indexed measurements or calculated volume approximations did not.

Twenty-four hour Holter monitoring of unsedated healthy cats in the home environment.

OBJECTIVE To determine the heart rate, rhythm, number of ventricular premature complexes (VPCs) and atrial premature complexes (APCs) in unsedated cats using Holter monitoring. ANIMALS, MATERIALS AND METHODS Twenty-three healthy client owned cats were used. Clinical examination, blood pressure measurements, echocardiographic examination and serum biochemical analysis were performed. A lightweight Holter was used in the home environment. RESULTS Three-lead electrocardiographic registrations of good quality were obtained from all cats. Normal sinus rhythm was present in all cats. The median heart rate was 165 beats per minute (bpm), range 70-303 bpm. Mean heart rate varied significantly with age and gender. Sinus arrhythmia occurred intermittently in 18 cats (78%). Uncommon ventricular premature complexes occurred in 18 (78%) of the cats. The median number of VPCs per cat was 3 complexes/24 h period, range 0-146. Cats 7-15 years of age had significantly more VPCs than cats 1-6 years of age (median 6 versus 1 per 24 h period, p=0.04). A single APC occurred in one cat (4%). CONCLUSIONS Cats commonly have intermittent sinus arrhythmia. Many healthy cats have rare single VPCs per 24 h period. Old cats have significantly more VPCs than young cats. The heart rate varies significantly with age and gender.