Population and survival characteristics of cats with hypertrophic cardiomyopathy: 260 cases (1990-1999)

OBJECTIVE: To determine current population characteristics of, clinical findings in, and survival times for cats with hypertrophic cardiomyopathy (HCM). DESIGN: Retrospective study. ANIMALS: 260 cats with HCM. PROCEDURE: Information was obtained from the medical records. Cats were classified into 1 of 4 clinical groups (congestive heart failure [CHF] group, arterial thromboembolism [ATE] group, syncope group, or cats without clinical signs [subclinical group]) on the basis of the primary clinical signs at the initial examination. RESULTS: 120 cats were classified in the CHF group, 43 in the ATE group, 10 in the syncope group, and 87 in the subclinical group. Antecedent events that may have precipitated CHF included i.v. fluid administration, anesthesia, surgery, and recent corticosteroid administration. Median survival time was 709 days (range, 2 to 4,418 days) for cats that survived > 24 hours. Cats in the subclinical group lived the longest (median survival time, 1,129 days; range, 2 to 3,778 days), followed by cats in the syncope group (654 days; range, 28 to 1,505 days), cats in the CHF group (563 days; range, 2 to 4,418 days), and cats in the ATE group (184 days; range, 2 to 2,278 days). Causes of death included ATE (n = 56), CHF (49), sudden death (13), and noncardiac causes (27). In univariate analyses, survival time was negatively correlated with left atrial size, age, right ventricular enlargement, and thoracentesis. Cats with systolic anterior motion of the mitral valve lived longer than cats without this echocardiographic finding. In multivariate analyses, only age and left atrial size remained significant predictors of survival time. CONCLUSIONS AND CLINICAL RELEVANCE: Although overall survival time for cats with HCM was similar to earlier reports, survival times for cats with CHF or ATE were longer than previously reported.     

Assessment of Left Ventricular Systolic Function by Strain Imaging Echocardiography in Various Stages of Feline Hypertrophic Cardiomyopathy

Background: Diastolic dysfunction occurs in many cats with hypertrophic cardiomyopathy (HCM). Less is known about systolic function in various stages of HCM. Myocardial strain analysis by tissue Doppler imaging (TDI) is a noninvasive echocardiographic method to assess systolic function that has not been reported previously in cats. Objectives: To evaluate systolic function in various stages of feline HCM by measurement of myocardial strain. Animals: Two hundred and sixty‐three cats. Methods: Cats were classified by echocardiography into one of the following groups: clinically healthy (control) group (n = 160), mild HCM (n = 22), moderate HCM (n = 39), and severe HCM (n = 42). Peak myocardial strain, measured by TDI in the basal and midventricular segment of the interventricular septal wall (IVS) and the left ventricular posterior wall (LVPW), was compared among different HCM and control groups. Results: Whereas conventional echocardiography demonstrated an apparently normal or supernormal contractile state based on percentage of fractional shortening, myocardial strain in all HCM groups was significantly decreased compared with the control group (P < .001). There was a significant correlation between strain values and wall thickness (P < .001). Reproducibility of strain analysis was 6.3% in the IVS and 9.7% in the LVPW. Conclusions and Clinical Importance: Myocardial strain analysis is a new, valuable, and reproducible method in cats. This method allows noninvasive detection of abnormal systolic deformation in cats with HCM despite apparently normal left ventricular systolic function as assessed by conventional echocardiography. The abnormal systolic deformation already was present in mild HCM and increased with progressive left ventricular concentric hypertrophy.     

Pulsed tissue Doppler imaging in normal cats and cats with hypertrophic cardiomyopathy

Myocardial motion was quantified in normal cats (n = 25) and cats with hypertrophic cardiomyopathy (HCM) (n = 23) using the pulsed tissue Doppler imaging (TDI) technique. A physiologic nonuniformity was documented in the myocardial motion of normal cats, which was detected as higher early diastolic velocities, acceleration, and deceleration in the interventricular septum compared with the left ventricular free wall (LVFW). HCM cats exhibited lower early diastolic velocities, acceleration, and deceleration and also prolonged isovolumic relaxation time compared with normal cats. These differences were detected mainly along the longitudinal axis of the heart. A cutoff value of E' in the LVFW along the longitudinal axis >7.2 cm/s discriminated normal from HCM cats with a sensitivity of 92% and a specificity of 87%. The physiologic nonuniformity of myocardial motion during diastole was lost in affected cats. Systolic impairment (decreased late-systolic velocities in most segments along the longitudinal axis and decreased early systolic acceleration in both mitral annular sites) was evident in HCM cats irrespective of the presence of left ventricular outflow tract obstruction and congestive heart failure. Postsystolic thickening was recorded in the LVFW along the longitudinal axis only in affected cats (n = 6) and was another finding indicative of systolic impairment in the HCM of this species. This study identified both diastolic and systolic impairment in cats with HCM compared with normal cats. The study also documents the normal physiologic nonhomogeneity in myocardial motion in cats and the subsequent loss of this feature in the HCM diseased state.     

Assessment of left ventricular longitudinal function in cats with subclinical hypertrophic cardiomyopathy using tissue Doppler imaging and speckle tracking echocardiography

Hypertrophic cardiomyopathy (HCM) in cats is characterized by concentric left ventricular (LV) hypertrophy and both diastolic and systolic dysfunction. Although impaired cardiac function detected by tissue Doppler imaging (TDI) in cats with HCM was previously reported, reference ranges of TDI in normal cats and cats with HCM have been reported as widely variable. Two-dimensional speckle tracking echocardiography (STE) was useful for assessment of cardiac function in human patients with HCM, but clinical utility was not known in cats. The aim of this study was to assess global and segmental LV myocardial function using STE in cats with HCM whose TDI variables were within the reference range. A total of 35 cats of different breeds were enrolled in this study. The HCM group (n=22) was cats diagnosed as HCM without left atrial enlargement and with normal TDI measurements. HCM cats were further divided into a segmental hypertrophy (S-HCM) group and a diffuse hypertrophy (D-HCM) group. The control group consisted of 13 clinically healthy cats. No cats in any group showed any clinical symptoms. Conventional echocardiography, TDI, and global and segmental STE indices were evaluated and compared between groups. Only the longitudinal strain rate during early diastole was significantly decreased in both HCM groups, even in all segments including those without hypertrophy in S-HCM group. This study suggests that STE parameters are the more sensitive variables compared with conventional TDI parameters to detect early myocardial diastolic dysfunction in cats with HCM.     

Prognostic value of mitral annular systolic plane excursion and tricuspid annular plane systolic excursion in cats with hypertrophic cardiomyopathy

Introduction

Hypertrophic cardiomyopathy (HCM) has a variable prognosis; left atrial size, presence of clinical signs and left ventricular systolic function have been shown to predict outcomes. Mitral annular plane systolic excursion (MAPSE) and tricuspid annular plane systolic excursion (TAPSE) assess longitudinal ventricular systolic function and are decreased in cats with HCM. The aim of the study was to ascertain whether MAPSE and TAPSE have prognostic value in HCM and if cats with pleural effusion have lower MAPSE and TAPSE than cats with pulmonary oedema.

Quantification of left ventricular diastolic wall motion by Doppler tissue imaging in healthy cats and cats with cardiomyopathy

OBJECTIVE: To assess Doppler tissue imaging (DTI) for evaluating left ventricular diastolic wall motion in healthy cats and cats with cardiomyopathy. ANIMALS: 20 healthy cats, 9 cats with hypertrophic cardiomyopathy (HCM), and 9 cats with unclassified cardiomyopathy (UCM). PROCEDURE: A pulsed wave DTI sample gate was positioned at a subendocardial region of the left ventricular free wall in the short axis view and at the lateral mitral annulus in the apical 4-chamber view. Indices of diastolic wall motion were measured, including peak diastolic velocity (PDV), mean rate of acceleration and deceleration of the maximal diastolic waveform (MDWaccel and MDWdecel, respectively), and isovolumetric relaxation time (IVRT). RESULTS: The PDV of cats with HCM and 6 of 9 cats with UCM was significantly decreased, compared with that of healthy cats. In the 3 cats with UCM that had a PDV that was not different from healthy cats, MDWaccel and MDWdecel were greater, and IVRT was shorter than those of healthy cats. The IVRT in cats with HCM was longer than that of other cats. CONCLUSIONS AND CLINICAL RELEVANCE: Indices of diastolic function in cats with HCM, and in many cats with UCM, differed from those of healthy cats and were similar to those reported in humans with HCM and restrictive cardiomyopathy, respectively. However, the hemodynamic abnormality was not the same for all cats with UCM; some cats with an enlarged left atrium and a normal left ventricle (ie, UCM) had abnormal left ventricular wall motion consistent with restrictive cardiomyopathy while others did not.     

Tissue Doppler imaging and gradient echo cardiac magnetic resonance imaging in normal cats and cats with hypertrophic cardiomyopathy

Cats with hypertrophic cardiomyopathy (HCM) often develop diastolic dysfunction, which can lead to development of left congestive heart failure. Tissue Doppler imaging (TDI) echocardiography has emerged as a useful, noninvasive method for assessing diastolic function in cats. Cardiac magnetic resonance imaging (cMRI) has been performed in cats and accurately quantifies left ventricular (LV) mass in normal cats. However, assessment of cardiac function in cats by cMRI has not been performed. Six normal Domestic Shorthair cats and 7 Maine Coon cats with moderate to severe HCM were sedated, and TDI of the lateral mitral annulus was performed. Peak early diastolic velocity (Em) was measured from 5 nonconsecutive beats. Cats were anesthetized with propofol and electrocardiogram-gated gradient echo cMRI was performed during apnea after hyperventilation. Short-axis images of the LV extending from the mitral annulus to the apex were obtained throughout the cardiac cycle. LV mass at end systole and LV volumes throughout the cardiac cycle were quantified according to Simpson's rule. To assess the possible influence of propofol on diastolic function, TDI was performed on the 7 cats with HCM while sedated and then while anesthetized with propofol. Em was significantly lower in cats with HCM than normal cats (6.7 +/- 1.3 cm/s versus 11.6 +/- 1.9 cm/s, P < .001, respectively). There was no difference in the cMRI indices of diastolic function in normal and HCM cats. Propofol did not reduce diastolic function (Em) in cats with HCM but mildly reduced systolic myocardial velocity (S) in Maine Coon cats with HCM that were anesthetized with propofol (P = .87 and P = .03, respectively).     

Echocardiography, electrocardiography, and radiography of cats with dilatation cardiomyopathy, hypertrophic cardiomyopathy, and hyperthyroidism

The echocardiographic, ECG, and radiographic findings of sequentially examined cats with dilatation cardiomyopathy (DCM, n = 7), hypertrophic cardiomyopathy (HCM, n = 8), and hyperthyroidism (HT, n = 20) were compared with those of healthy control cats (n = 11). Cats with DCM were easily differentiated from healthy cats by echocardiography and from cats with HCM and HT by a dilated left ventricle at end-diastole with a mean +/- SD of 2.20 +/- 0.36 cm, reduced fractional shortening (2.9% +/- 3.7%), reduced aortic amplitude (0.07 +/- 0.05 cm), reduced left ventricular wall amplitude (0.09 +/- 0.09 cm), and increased E-point septal separation (0.83 +/- 0.29 cm). The cats with HCM were most consistently recognized echocardiographically by increased left ventricular wall thickness at end-diastole (0.75 +/- 0.12 cm). Some cats with HT had abnormal echocardiograms with left ventricular wall hypertrophy. These cats could usually be differentiated from the cats with HCM because of normal or increased ventricular wall amplitude, aortic amplitude, or percentage of thickening of the left ventricular wall and interventricular septum. Left atrial enlargement (left atrial diameter greater than 1.57 cm or left atrium/aorta greater than 1.75) was commonly detected by the echocardiogram in cats with DCM, HCM, or HT. The echocardiogram was helpful in differentiating the type of cardiomyopathy (DCM, HCM, or HT) when plain thoracic radiographs indicated that cardiomegaly existed. The ECG may have indicated incorrectly that there was left ventricular enlargement in some cats with HT, and it did not indicate consistently that left ventricular enlargement existed when present in cats with DCM or HCM. The ECG was a poor indicator of left atrial enlargement in all cats.     

Transient Myocardial Thickening in Cats Associated with Heart Failure

Background

Cats with hypertrophic cardiomyopathy (HCM) and congestive heart failure (CHF) can have resolution of both left ventricular hypertrophy and CHF.

Objectives

To describe the clinical characteristics of cats with transient myocardial thickening (TMT) and CHF compared with a control population of cats without resolution of HCM.

Animals

A total of 21 cats with TMT, 21 cats with HCM.

Methods

Retrospective study. Clinical records at 4 veterinary centers were searched for TMT cases and a control group of cats with HCM and CHF. TMT was defined as initial maximal left ventricular wall thickness (LVWT) ≥6 mm with left‐sided CHF, with subsequent resolution of CHF, reduction in left atrium/aorta (LA/Ao), and LVWT<5.5 mm. HCM was defined as persistent LVWT ≥6 mm.

Results

Cats with TMT were younger (2 [0.4–11.4] years) than cats with HCM (8 [1.6–14] years) (P < 0.0001), and antecedent events were more common (15/21 versus 6/21, respectively) (P = 0.01). In cats with TMT, LVWT normalized from 6.8 [6.0–9.7] mm to 4.8 [2.8–5.3] mm and LA/Ao decreased from 1.8 [1.6–2.3] to 1.45 [1.2–1.7] after a mean interval of 3.3 (95% CI: 1.8–4.7) months. CHF recurred in 1 of 21 TMT and 15 of 21 cats with HCM. Cardiac treatment was discontinued in 20 of 21 cats with TMT and 0 of 21 HCM cats. All cats with TMT survived, whereas 8 of 19 cats with HCM died during the study period.

Conclusions and Clinical Importance

TMT occurs in younger cats, and antecedent events are common. The prognosis is better in cats with CHF associated with TMT than HCM.     

The effect of ramipril on left ventricular mass, myocardial fibrosis, diastolic function, and plasma neurohormones in Maine Coon cats with familial hypertrophic cardiomyopathy without heart failure

BACKGROUND: Hypertrophic cardiomyopathy (HCM) is the most common heart disease of cats, resulting in left ventricular (LV) hypertrophy, myocardial fibrosis, and diastolic dysfunction. HYPOTHESIS: Ramipril will reduce LV mass, improve diastolic function, and reduce myocardial fibrosis in cats with HCM without congestive heart failure (CHF). ANIMALS: This prospective, blinded, placebo-controlled study included 26 Maine Coon and Maine Coon cross-bred cats with familial HCM but without CHF. METHODS: Cats were matched for LV mass index (LVMI) and were randomized to receive ramipril (0.5 mg/kg) or placebo q24h for 1 year, with investigators blinded. Plasma brain natriuretic peptide (BNP) concentration, plasma aldosterone concentration, Doppler tissue imaging (DTI), and systolic blood pressure were measured at baseline and every 3 months for 1 year. Cardiac magnetic resonance imaging (cMRI) was performed to quantify LV mass and myocardial fibrosis by delayed enhancement (DE) cMRI at baseline and 6 and 12 months. Plasma angiotensin-converting enzyme (ACE) activity was measured on 16 cats 1 hour after PO administration. RESULTS: Plasma ACE activity was adequately suppressed (97%) in cats treated with ramipril. LV mass, LVMI, DTI, DE, blood pressure, plasma BNP, and plasma aldosterone were not different in cats treated with ramipril compared with placebo (P = .85, P = .94, P = .91, P = .89, P = .28, P = .18, and P = .25, respectively). CONCLUSION: Treatment of Maine Coon cats with HCM without CHF with ramipril did not change LV mass, improve diastolic function, alter DE, or alter plasma BNP or aldosterone concentrations in a relevant manner.     

Effect of spironolactone on diastolic function and left ventricular mass in Maine Coon cats with familial hypertrophic cardiomyopathy

BACKGROUND: Myocardial fibrosis occurs in cats with hypertrophic cardiomyopathy (HCM), and is one factor that leads to diastolic dysfunction. Spironolactone (SPIR) reduces myocardial fibrosis in several models of HCM and in humans with cardiac disease. HYPOTHESIS: SPIR will improve diastolic function and reduce left ventricular (LV) mass in Maine Coon cats with HCM. METHODS: Maine Coon cats with familial HCM were included if there was concentric hypertrophy (> or =6 mm end diastolic wall thickness) and decreased early lateral mitral annular velocity (Em) or summated early and late mitral annular velocity (EAsum) measured by pulsed wave tissue Doppler imaging echocardiography. Cats were paired by Em-EAsum and randomized to receive 2 mg/kg SPIR (n = 13) or placebo (n = 13) PO q12 h for 4 months. Em-EAsum, systolic velocity, LV mass, and the ratio of left atrial to aortic diameter were measured at baseline, 2 months, and 4 months. Statistical analysis included 2-way repeated measures analysis of variance and the Student's t-test. RESULTS: Plasma aldosterone concentration increased in cats treated with SPIR (235 ng/mL, baseline; 935 ng/mL, 2 months; 1,077 ng/mL, 4 months; P < .001 at 2 and 4 months). No significant treatment effect was identified for early or early-late summated diastolic mitral annular velocity or any other variable except plasma aldosterone concentration. Severe facial ulcerative dermatitis developed in 4 of 13 cats treated with SPIR, requiring discontinuation of the drug. CONCLUSION: SPIR did not improve Em or EAsum of the lateral mitral annulus or alter LV mass over 4 months. One third of cats treated with SPIR developed severe ulcerative facial dermatitis.     

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

Background

Maine 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.

Methods

All 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.

Results

Examinations 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.

Conclusion

Depending 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.     

Hypercoagulability in cats with cardiomyopathy

BACKGROUND: Arterial thromboembolism (ATE) is a common complication of feline cardiomyopathy; however, the pathogenesis of ATE is unknown. HYPOTHESIS: Systemic activation of the coagulation cascade (hypercoagulability) and endothelial injury promote ATE in cardiomyopathic cats. ANIMALS: Healthy cats (n = 30) and 3 groups of cardiomyopathic cats: Group (1) left atrial enlargement only (LAE [n = 11]), ie, left atrial to aortic ratio >1.4; Group (2) LAE with spontaneous echocardiographic contrast, atrial thrombi or both (SEC-T [n = 16]); and Group (3) acute ATE with LAE (n = 16). METHODS: Hypercoagulability was defined by 2 or more laboratory abnormalities reflecting coagulation factor excess (high fibrinogen concentration or Factor VIII coagulant activity), inhibitor deficiency (low antithrombin activity), or thrombin generation (high thrombin-antithrombin complex [TAT] and d-dimer concentrations). High von Willebrand factor antigen concentration (vWF : Ag) was considered a marker of endothelial injury. Data were analyzed using nonparametric statistics. RESULTS: The 3 groups of cats with cardiac disease had higher median fibrinogen concentrations than did the healthy cats. Criteria of hypercoagulability were found exclusively in cats with SEC-T (50%) and ATE (56%). Hypercoagulability was not associated with left atrial size or congestive heart failure (CHF). ATE cats had significantly higher median vWF : Ag concentration than did the other groups. CONCLUSION AND CLINICAL IMPORTANCE: Systemic hypercoagulability is evident in many cardiomyopathic cats, often without concurrent CHF or overt ATE. Hypercoagulabilty may represent a risk factor for ATE. High vWF : Ag in ATE cats was attributed to downstream endothelial injury from the occlusive thrombus.     

M-MODE ECHOCARDIOGRAPHY AS A DIAGNOSTIC AID FOR FELINE CARDIOMYOPATHY

Normal cats and cats with congestive cardiomyopathy (CCM) and hypertrophic cardiomyopathy (HCM) were examined using M-mode echocardiography to determine its diagnostic capabilities. Sixteen normal cats were examined to verify previously reported data and to add further echocardiographic inforamtion (left atrial/aortic root ratio, left posterior wall thickness at end systole and end diastole, amplitude of mitral valve excursions, and velocity of valve opening and closure) to aid in differential diagnosis. Significant (p<0.05) changes were detected between the normal cats and those with cardiomyopathy. In each type of cardiomyopathy, alterations in left atrial dimension, left atrial/aortic root ratio, left ventricular dimension, left ventricular wall thickness and percentage of ventricular dimensional change were identified. Altered mitral valve motion was found with HCM. Echocardiography was found to be an accurate technique for definitive diagnosis of feline cardiomyopathy.     

N-terminal atrial natriuretic peptide immunoreactivity in plasma of cats with hypertrophic cardiomyopathy

Atrial natriuretic peptide (ANP) is an important regulator of fluid homeostasis and vascular tone. We sought to compare N-terminal ANP immunoreactivity (ANP-IR) in plasma from cats with and without hypertrophic cardiomyopathy (HCM). Secondarily, we evaluated relationships between ANP-IR and echocardiographical variables in cats with HCM and healthy cats. Venous blood samples were obtained from 17 cats with HCM and from 19 healthy cats. Plasma ANP-IR concentration was determined by an enzyme-linked immunoassay. Two cats with HCM had clinical evidence of congestive heart failure; the remainder had subclinical disease. Plasma ANP-IR concentration was higher in cats with HCM (3,808 +/- 1,406 fmol/L, mean +/- SD) than in control cats (3,079 +/- 1,233 fmol/L), but this difference was not statistically significant (P = .11; 95% confidence interval [CI] = -166 to 1,622). There was a significant, but modest correlation between plasma ANP-IR concentration and left ventricular posterior wall thickness (r = 0.42; P = .01). Additionally, plasma ANP-IR concentration was weakly correlated with left atrial size (r = 0.35; P = .03). A linear regression model was developed to further explore these relationships. Atrial size and wall thickness were included in the model; the 2 explanatory variables had an interactive effect on plasma ANP-IR concentration (R2 = 0.27; P = .02). There was no appreciable correlation between plasma ANP-IR concentration and any other echocardiographical variable. In a population that included cats with subclinical disease, those with HCM did not have significantly higher plasma ANP-IR concentration than did healthy cats. An exploratory multivariable regression analysis suggested a linear relationship between ANP-IR concentration and atrial size, wall thickness, and their interaction.     

Heart rate and arrhythmia frequency of normal cats compared to cats with asymptomatic hypertrophic cardiomyopathy

ObjectivesTo compare heart rate and arrhythmia frequency and complexity in a normal population of cats to a population of cats with hypertrophic cardiomyopathy (HCM).Animals17 cats with HCM and 15 cats with normal echocardiograms.MethodsResults for echocardiography, electrocardiography, Doppler blood pressure, and 24-h Holter monitoring were compared between groups.ResultsThere was no difference in heart rate between HCM cats and normal cats regardless of modality used. All (17/17) HCM cats had ventricular arrhythmias (geometric mean 124 complexes/24 h) with 82% (14/17) exhibiting complex arrhythmias (couplets, triplets, or ventricular tachycardia). Most (14/15) normal cats had ventricular arrhythmias (geometric mean 4 complexes/24 h), but only 20% (3/15) exhibited complexity. HCM cats had significantly more total ventricular complexes, ventricular premature complexes and accelerated idioventricular rhythm than normal cats (P < 0.0001, P < 0.0001, and P = 0.01, respectively). Eighty eight percent (15/17) of HCM cats had supraventricular arrhythmias (geometric mean 9 complexes/24 h) with 23% (4/17) exhibiting complexity. Sixty percent (9/15) of normal cats had supraventricular arrhythmias (geometric mean 1 complex/24 h) with 13% (2/15) exhibiting complexity. Cats with hypertrophic cardiomyopathy had significantly more supraventricular complexes than normal cats (P = 0.0148).ConclusionCats with asymptomatic HCM have more frequent and complex ventricular and supraventricular arrhythmias than normal cats but do not have different overall heart rates compared to normal cats. Further studies are needed to determine if these arrhythmias are associated with an increased risk of sudden cardiac death or influence long-term survival.     

Pulsed Doppler assessment of left ventricular diastolic function in normal and cardiomyopathic cats.

Left ventricular (LV) diastolic function was evaluated in 16 cats with primary hypertrophic cardiomyopathy (HCM) using pulsed Doppler (PD) assessment of transmitral flow and isovolumic relaxation time. Data obtained was compared to data from 12 healthy, adult, research cats. Compared to normal cats, the HCM group showed significantly (p value less than 0.05) reduced early LV inflow velocities (mean +/- standard error [SE], peak velocity of 0.70+/-0.04 m/s versus 0.54+/-0.04 m/s and integrated velocity of 0.48+/-0.08 m/s versus 0.37+/-0.03 m/s); a reduced rate of deceleration of early inflow (mean+/-SE, -12.0+/-1.0 m/s2 versus -5.1+/-1.1 m/s2); prolonged isovolumic relaxation time (mean +/- SE, 45.7+/-3.3 ms versus 76.0+/-3.1 ms); and increased atrial systolic flow velocities (mean +/- SE, peak velocity of 0.29+/-0.04 m/s versus 0.48+/-0.04 m/s and integrated velocity of 0.21+/-0.03 m/s versus 0.34+/-0.03 m/s). The results suggest that PD provides a noninvasive method of identifying and quantifying functional diastolic impairment in cats with HCM.     

Systolic and diastolic myocardial dysfunction in cats with hypertrophic cardiomyopathy or systemic hypertension

BACKGROUND: Hypertrophic cardiomyopathy (HCM) and chronic systemic hypertension (SHT) can both lead to left-ventricular hypertrophy (LVH) in cats. Assessment of LVH-associated myocardial dysfunction could provide new insights in the understanding of the pathophysiology of these diseases. HYPOTHESIS: Quantification of left-ventricular free-wall (LVFW) motion using tissue Doppler imaging (TDI) could permit differentiation of feline HCM from SHT-related LVH (LVH-SHT). ANIMALS: A total of 108 cats of different breeds were enrolled in this study: 35 cats with HCM, 17 with concentric LVH and SHT, and 56 healthy cats as a control group. METHODS: All cats were examined by conventional echocardiography and 2-dimensional color TDI. RESULTS: Radial and longitudinal diastolic LVFW velocities were similarly altered in cats with HCM and LVH-SHT, compared to controls. Systolic velocities were also lower in the groups with hypertrophy than in the controls, for longitudinal but not radial motion. To determine whether these diastolic and systolic alterations could also be observed in cats without LVFW hypertrophy, we performed a subgroup analysis in cats with a normal M-mode examination, that is, with only a localized subaortic interventricular septum hypertrophy. A significant radial and longitudinal diastolic dysfunction was still observed in both the HCM and LVH-SHT groups compared to controls, and systolic dysfunction was detected in the longitudinal motion. CONCLUSIONS: LVFW motion is similarly altered in cats with HCM and LVH-SHT. This dysfunction occurs independently of the presence of myocardial hypertrophy, demonstrating that TDI is capable of detecting systolic and diastolic segmental functional changes in nonhypertrophied wall segments in cats with HCM and SHT.     

The effect of atenolol on NT-proBNP and troponin in asymptomatic cats with severe left ventricular hypertrophy because of hypertrophic cardiomyopathy: a pilot study

Background: Atenolol often is used empirically in cats with hypertrophic cardiomyopathy (HCM) before the onset of heart failure, although evidence of efficacy is lacking. Cardiac biomarkers play a critical role in the early detection of subclinical cardiac disease, in the prediction of long‐term prognosis, and in monitoring the response to therapy in humans. Hypothesis: Circulating concentrations of the biomarkers N‐terminal pro‐B type natriuretic peptide (NT‐proBNP) and cardiac troponin I (cTnI) will decrease after chronic administration of atenolol PO to cats with severe HCM but no signs of heart failure. Animals: Six Maine Coon or Maine Coon cross cats with severe HCM. Methods: Cats were treated with atenolol (12.5 mg PO q12 h) for 30 days. No cat had left ventricular dynamic outflow tract obstruction caused by systolic anterior motion of the mitral valve. The concentrations of NT‐proBNP and cTnI were assayed before and on the last day of drug administration. Results: There was no statistically significant change in NT‐proBNP (median before, 394 pmol/L; range, 71–1,500 pmol/L; median after, 439 pmol/L; range, 24–1,500 pmol/L; P = .63) or in cTnI (median before, 0.24 ng/mL; range, 0.10–0.97 ng/mL; median after, 0.28 ng/mL; range, 0.09–1.0 ng/mL; P = .69) after administration of atenolol. Conclusions: Atenolol administration did not decrease NT‐proBNP or cTnI concentrations in cats with severe left ventricular hypertrophy caused by hypertrophic cardiomyopathy. These results suggest that atenolol did not decrease myocardial ischemia and myocyte death in these cats. A larger clinical trial is warranted to verify these findings.     

Myocardial collagen deposition and inflammatory cell infiltration in cats with pre-clinical hypertrophic cardiomyopathy

The histological features of feline hypertrophic cardiomyopathy (HCM) have been well documented, but there are no reports describing the histological features in mild pre-clinical disease, since cats are rarely screened for the disease in the early stages before clinical signs are apparent. Histological changes at the early stage of the disease in pre-clinical cats could contribute to an improved understanding of disease aetiology or progression. The aim of this study was to evaluate the histological features of HCM in the left ventricular (LV) myocardium of cats diagnosed with pre-clinical HCM. Clinically healthy cats with normal (n = 11) and pre-clinical HCM (n = 6) were identified on the basis of echocardiography; LV free wall dimensions (LVFWd) and/or interventricular septal wall (IVSd) dimensions during diastole of 6–7 mm were defined as HCM, while equivalent dimensions <5.5 mm were defined as normal. LV myocardial sections were assessed and collagen content and inflammatory cell infiltrates were quantified objectively. Multifocal areas of inflammatory cell infiltration, predominantly lymphocytes, were observed frequently in the left myocardium of cats with pre-clinical HCM. Tissue from cats with pre-clinical HCM also had a higher number of neutrophils and a greater collagen content than the myocardium of normal cats. The myocardium variably demonstrated other features characteristic of HCM, including arteriolar mural hypertrophy and interstitial fibrosis and, to a lesser extent, myocardial fibre disarray and cardiomyocyte hypertrophy. These results suggest that an inflammatory process could contribute to increased collagen content and the myocardial fibrosis known to be associated with HCM.