Cardiac extracellular volume fraction in cats with preclinical hypertrophic cardiomyopathy

Reversible right-sided congestive heart failure secondary to primary hyperaldosteronism in a cat

A 10-year-old male castrated Somali cat presented with neurologic signs, severe systemic hypertension, and hypokalemia. Abdominal ultrasonography demonstrated a left adrenal mass, and the serum aldosterone concentration was increased. Computed tomography and follow-up diagnostic testing confirmed a left adrenal mass consistent with functional adenocarcinoma; additional findings included chronic airway and parenchymal disease. Transthoracic echocardiography revealed biatrial enlargement, with abdominal and pericardial effusion, consistent with right-sided congestive heart failure. The cat was treated for congestive heart failure and adrenalectomy was performed. Cardiac structure and function returned to normal within 6 months postoperatively. This report highlights a case of reversible congestive heart failure secondary to primary hyperaldosteronism.

Multiparametric myocardial mapping using cardiac magnetic resonance imaging in healthy dogs: Reproducibility, repeatability, and differences across slices, segments, and sequences

Myocardial mapping in humans has been widely studied and applied to understand heart disease, facilitate early diagnosis, and determine therapeutic targets; however, the reproducibility, repeatability, and protocol-dependent differences in myocardial mapping in dogs remain unknown, which limits its application in dogs. This study investigated the reproducibility and test-retest repeatability of myocardial mapping in dogs and evaluated the differences according to slice, segment, and sequence. Precontrast T1 (native T1), T2 (T2), and T2* relaxation time (T2*), and extracellular volume (ECV) were measured at the base, midventricle, and apex of the left ventricle in six healthy beagles. To compare the sequences, the saturation recovery-based (SMART1) and inversion recovery-based (MOLLI) sequences were used for native T1 and ECV mapping. The intraclass correlation coefficient was measured to evaluate reproducibility and repeatability using the coefficient of variation and Bland-Altman analysis. All parameters showed good to excellent intra- and interobserver reproducibility and test-retest repeatability. The apex slice showed the lowest repeatability among the slices, whereas ECV had the lowest repeatability among the parameters. Native T1, ECV, and T2* did not differ according to slice, but T2 significantly increased from the base to the apex. Native T1 was significantly higher in SMART1 than in MOLLI, whereas ECV did not differ between the two sequences. Our results suggest that myocardial mapping is applicable in dogs with high reproducibility and repeatability, although slice and sequence differences should be considered. This study can serve as a guide for myocardial mapping studies in dogs with heart disease.

Importance of T1-Mapping Sequence in Patients with Hypertrophic Cardiomyopathy without Foci of Non-Ischemic Myocardial Injury in Late Gadolinium Enhancement Sequence

BACKGROUND

The aim of this study was to assess the importance of T1-mapping sequences in the diagnosis of hypertrophic cardiomyopathy (HCM) in patients without foci of non-ischemic myocardial injury in classic cardiac magnetic resonance (CMR) sequences.

METHODS

Two groups were compared: 28 patients with HCM, without any foci of myocardial injury in the late gadolinium enhancement (LGE) sequence (HCM group), and 28 patients without cardiomyopathy (CON group). Classic CMR sequences and T1-mapping sequences were performed. The following parameters were assessed: T1 time of the whole left ventricular myocardium, T1 time of myocardium in the basal, middle and apical layers of the left ventricle, and T1 time in individual segments of the left ventricular myocardium. Myocardial extracellular volume (ECV) was assessed similarly.

RESULTS

ECV was significantly higher in the HCM group than in the CON group, for the whole left ventricular myocardium, for the basal and apical layers of the left ventricle, and for segments 1-3, 8, and 13-16 of the left ventricle. Regression analysis showed that a higher left-ventricular mass index (LVMI), a higher body mass index and older age are factors independently associated with a higher ECV of the whole myocardium but only in the group with LVMI ≥ 131.84 g/m2.

CONCLUSION

In patients with HCM without foci of non-ischemic myocardial injury, higher ECV values of the left ventricular myocardium are observed.

Aortic annular plane systolic excursion in cats with hypertrophic cardiomyopathy

BACKGROUND

Impairment of left ventricular (LV) longitudinal function is an early marker of systolic dysfunction in hypertrophic cardiomyopathy (HCM). Aortic annular plane systolic excursion (AAPSE) is a measure of LV longitudinal function in people that has not been evaluated in cats.

HYPOTHESIS

Aortic annular plane systolic excursion is lower in cats with HCM compared to control cats, and cats in stage C have the lowest AAPSE.

ANIMALS

One hundred seventy-five cats: 60 normal, 61 HCM stage B and 54 HCM stage C cats.

MATERIALS

Multicenter retrospective case-control study. Electronic medical records from 4 referral hospitals were reviewed for cats diagnosed with HCM and normal cats. HCM was defined as LV wall thickness ≥6 mm and normal cats ≤5 mm. M-mode bisecting the aorta in right parasternal short-axis view was used to measure AAPSE.

RESULTS

Aortic annular plane systolic excursion was lower in HCM cats compared to normal cats (3.9 ± 0.9 mm versus 4.6 ± 0.9 mm, P < .001) and was lowest in HCM stage C (2.4 ± 0.6 mm, P < .001). An AAPSE <2.9 mm gave a sensitivity of 83% (95% CI 71%-91%) and specificity of 92% (95% CI 82%-97%) to differentiate HCM stage C from stage B. AAPSE correlated with mitral annular plane systolic excursion (r = .6 [.4-.7], P < .001), and atrial fractional shortening (r = .6 [.5-.7], P < .001), but showed no correlation with LV fractional shortening.

CONCLUSIONS AND CLINICAL IMPORTANCE

Aortic annular plane systolic excursion is an easily acquired echocardiographic variable and might be a new measurement of LV systolic performance in cats with HCM.

Current use of cardiac MRI in animals

Cardiovascular magnetic resonance (CMR) imaging has evolved to become an indispensable tool in human cardiology. It is a non-invasive technique that enables objective assessment of myocardial function, size, and tissue composition. Recent innovations in magnetic resonance imaging scanner technology and parallel imaging techniques have facilitated the generation of parametric mapping to explore tissue characteristics, and the emergence of strain imaging has enabled cardiologists to evaluate cardiac function beyond conventional metrics. As veterinary cardiology continues to utilize CMR beyond the reference standard, clinical application of CMR will further expand our capabilities. This article describes the current use of CMR and adoption of more recent advances such as T1/T2 mapping in veterinary cardiology.

Hypertrophic Cardiomyopathy-Advances in Imaging and Diagnostic Strategies

Hypertrophic cardiomyopathy (HCM) is the most important and prevalent cardiac disease in cats. Due to the highly variable nature of HCM, a multimodal approach including physical examination, genetic evaluation, cardiac biomarkers, and imaging are all essential elements to appropriate and timely diagnosis. These foundational elements are advancing rapidly in veterinary medicine. Newer biomarkers such as galectin-3 are currently being researched and advances in tissue speckle-tracking and contrast-enhanced echocardiography are readily available. Advanced imaging techniques, such as cardiac MRI, are providing previously unavailable information about myocardial fibrosis and paving the way for enhanced diagnostic capabilities and risk-stratification in cats with HCM.

Predicting Development of Hypertrophic Cardiomyopathy and Disease Outcomes in Cats

Echocardiography is the gold standard imaging modality to diagnose hypertrophic cardiomyopathy (HCM) in cats. Echocardiographic features can predict both cats at an increased risk of developing HCM and cats with HCM at an increased risk of developing cardiovascular events or experiencing cardiac death. Left atrial dysfunction seems to be an important feature of HCM, as it is an early phenotypic abnormality and is also associated with worse outcome.

Galectin-3 as a novel biomarker in cats with hypertrophic cardiomyopathy

INTRODUCTION/OBJECTIVES

Galectin-3 (Gal-3) is a circulating biomarker of fibrosis. In humans, increased Gal-3 is predictive of myocardial fibrosis and adverse cardiac events. The aim of this study was to evaluate the potential for Gal-3 as a cardiac biomarker in cats with hypertrophic cardiomyopathy (HCM).

MATERIALS AND METHODS

Eighty cats were enrolled (25 healthy cats with normal hearts, 35 with HCM American College of Veterinary Internal Medicine (ACVIM) stage B, and 21 with HCM ACVIM stage C). Each cat received a full echocardiogram, health panel, and total thyroxin level. Galectin-3 levels were measured for each enrolled patient. Troponin I and N-terminal pro-brain natriuretic peptide (NT-proBNP) were obtained for the majority of cats. Additionally, 17 ACVIM stage B cats underwent cardiac-gated magnetic resonance (CMR) imaging to assess myocardial extracellular volume (ECV), a noninvasive measure of myocardial fibrosis.

RESULTS

Galectin-3 levels are increased in cats with HCM ACVIM stage B and C compared to healthy cats; however, no significant differences were detected between ACVIM stage B and ACVIM stage C cats. In HCM-affected cats, Galectin-3 showed statistically significant correlations with left atrial dimensions, left atrial:aorta ratio, and CMR-derived ECV. Quantitative NT-proBNP showed excellent discrimination between all groups and troponin I was able to discriminate between ACVIM stage C and normal cats, but not between other groups.

CONCLUSIONS

Circulating Gal-3 levels are increased in cats with HCM and is positively correlated with left atrial dimensions and ECV in affected cats. Further studies evaluating the relationship between Gal-3, myocardial fibrosis, and clinical outcomes are warranted.

Exploration of Mediators Associated with Myocardial Remodelling in Feline Hypertrophic Cardiomyopathy

Hypertrophic cardiomyopathy (HCM) affects both humans and cats and exhibits considerable interspecies similarities that are exemplified by underlying pathological processes and clinical presentation to the extent that developments in the human field may have direct relevance to the feline disease. Characteristic changes on histological examination include cardiomyocyte hypertrophy and interstitial and replacement fibrosis. Clinically, HCM is characterised by significant diastolic dysfunction due to a reduction in ventricular compliance and relaxation associated with extracellular matrix (ECM) remodelling and the development of ventricular hypertrophy. Studies in rodent models and human HCM patients have identified key protein mediators implicated in these pathological changes, including lumican, lysyl oxidase and TGF-β isoforms. We therefore sought to quantify and describe the cellular location of these mediators in the left ventricular myocardium of cats with HCM and investigate their relationship with the quantity and structural composition of the ECM. We identified increased myocardial content of lumican, LOX and TGF-β2 mainly attributed to their increased expression within cardiomyocytes in HCM cats compared to control cats. Furthermore, we found strong correlations between the expressions of these mediators that is compatible with their role as important components of cellular pathways promoting remodelling of the left ventricular myocardium. Fibrosis and hypertrophy are important pathological changes in feline HCM, and a greater understanding of the mechanisms driving this pathology may facilitate the identification of potential therapies.

Increase in skeletal muscle extracellular volume as an under-recognised change detected at cardiac MRI in hypertrophic cardiomyopathy

AIM

To explore skeletal muscle change and its correlation with the myocardium in hypertrophic cardiomyopathy (HCM) using cardiac magnetic resonance imaging (cMRI) with T1 mapping and late gadolinium enhancement (LGE).

MATERIALS AND METHODS

This retrospective study enrolled 50 HCM patients and 35 healthy controls. The extracellular volume (ECV) of the skeletal muscle and myocardium, the presence and absence of LGE of the myocardium, and cardiac troponin T (cTnT), were assessed. In the HCM group, the elevated ECV_skeletal group was defined as ECV_skeletal >2 standard deviations (SD) above the mean value of the controls. Statistical analyses included Student's t-test, the Mann-Whitney U-test, and linear regression.

RESULTS

ECV_skeletal in the HCM group was higher than in the control group (mean 13.0 versus 10.9%; p<0.001), with 20 (40%) HCM patients having elevated ECV_skeletal (ECV_skeletal ≥13.7%). In the HCM group, ECV_skeletal had a positive linear correlation with global myocardial ECV (r=0.37, p=0.009). In addition, the elevated ECV_skeletal group had a higher cTnT than the non-elevated group (log cTnT, mean 1.55 versus 1.16, p=0.045). Furthermore, segmental myocardial ECV in the elevated ECV_skeletal group was higher than in the non-elevated group, despite the presence or absence of myocardial LGE (median 30.1 versus 27.2%; 26.5 versus 24.6%, both p<0.001) or hypertrophy (median 29.0 versus 26.0%; 26.8 versus 24.8%, both p<0.001).

CONCLUSION

In the HCM patients, ECV_skeletal was higher than in the healthy controls. Furthermore, some ECV_skeletal changes had corresponding changes in the cTnT and myocardium.

Natural history of hypertrophic cardiomyopathy in cats from rehoming centers: The CatScan II study

BACKGROUND

The natural history of hypertrophic cardiomyopathy (HCM) in cats has been mainly studied in cats referred for suspected heart disease, which can skew the results towards cats with clinical signs. Few data are available on factors associated with development of HCM in cats.

HYPOTHESES

(1) Clinical variables can predict which cats will develop HCM; (2) HCM in cats not referred for suspected heart disease is associated with a low rate of cardiovascular events.

ANIMALS

One hundred seven cats from rehoming centers without a history of clinical signs of cardiac or systemic disease at the time of adoption.

METHODS

Prospective longitudinal study. After rehoming, shelter cats were reexamined for serial echocardiograms. Cox regression analysis was used to identify predictors of development of HCM in cats that were normal at baseline. Adverse cardiovascular events including heart failure, thromboembolism, or sudden death were recorded.

RESULTS

Cats were monitored for a median of 5.6 [1.2-9.2] years. At baseline, 68/107 cats were normal, 18/107 were equivocal and 21/107 had HCM. Nineteen cats developed HCM during the study period. The factors at baseline associated with increased hazard of developing HCM were lower left atrial fractional shortening, higher left ventricular fractional shortening, and higher body weight. Cardiovascular events were observed in 21% of cats with HCM.

CONCLUSIONS AND CLINICAL IMPORTANCE

Cardiovascular events were common in cats with HCM from a rehoming center study sample. Lower left atrial systolic function appears to precede overt HCM.

The Feline Cardiomyopathies: 2. Hypertrophic cardiomyopathy

Practical relevance:

Hypertrophic cardiomyopathy (HCM) is the most common form of feline cardiomyopathy observed clinically and may affect up to approximately 15% of the domestic cat population, primarily as a subclinical disease. Fortunately, severe HCM, leading to heart failure or arterial thromboembolism (ATE), only occurs in a small proportion of these cats.

Patient group:

Domestic cats of any age from 3 months upward, of either sex and of any breed, can be affected. A higher prevalence in male and domestic shorthair cats has been reported.

Diagnostics:

Subclinical feline HCM may or may not produce a heart murmur or gallop sound. Substantial left atrial enlargement can often be identified radiographically in cats with severe HCM. Biomarkers should not be relied on solely to diagnose the disease. While severe feline HCM can usually be diagnosed via echocardiography alone, feline HCM with mild to moderate left ventricular (LV) wall thickening is a diagnosis of exclusion, which means there is no definitive test for HCM in these cats and so other disorders that can cause mild to moderate LV wall thickening (eg, hyperthyroidism, systemic hypertension, acromegaly, dehydration) need to be ruled out.

Key findings:

While a genetic cause of HCM has been identified in two breeds and is suspected in another, for most cats the cause is unknown. Systolic anterior motion of the mitral valve (SAM) is the most common cause of dynamic left ventricular outflow tract obstruction (DLVOTO) and, in turn, the most common cause of a heart murmur with feline HCM. While severe DLVOTO is probably clinically significant and so should be treated, lesser degrees probably are not. Furthermore, since SAM can likely be induced in most cats with HCM, the distinction between HCM without obstruction and HCM with obstruction (HOCM) is of limited importance in cats. Diastolic dysfunction, and its consequences of abnormally increased atrial pressure leading to signs of heart failure, and sluggish atrial blood flow leading to ATE, is the primary abnormality that causes clinical signs and death in affected cats. Treatment (eg, loop diuretics) is aimed at controlling heart failure. Preventive treatment (eg, antithrombotic drugs) is aimed at reducing the risk of complications (eg, ATE).

Conclusions:

Most cats with HCM show no overt clinical signs and live a normal or near-normal life despite this disease. However, a substantial minority of cats develop overt clinical signs referable to heart failure or ATE that require treatment. For most cats with clinical signs caused by HCM, the long-term prognosis is poor to grave despite therapy.

Areas of uncertainty:

Genetic mutations (variants) that cause HCM have been identified in a few breeds, but, despite valiant efforts, the cause of HCM in the vast majority of cats remains unknown. No treatment currently exists that reverses or even slows the cardiomyopathic process in HCM, again despite valiant efforts. The search goes on.

Cardiac extracellular volume fraction in cats with preclinical hypertrophic cardiomyopathy

Background

Cardiac magnetic resonance imaging (CMR) allows for detection of fibrosis in hypertrophic cardiomyopathy (HCM) by quantification of the extracellular volume fraction (ECV).

Hypothesis/Objectives

To quantify native T1 mapping and ECV in cats. We hypothesize that native T1 mapping and ECV will be significantly increased in HCM cats compared with healthy cats.

Animals

Seventeen healthy and 12 preclinical HCM, age‐matched, client‐owned cats.

Methods

Prospective observational study. Tests performed included indirect blood pressure, CBC, biochemical analysis including total thyroid, urinalysis, transthoracic echocardiogram, and CMR. Cats were considered healthy if all tests were within normal limits and a diagnosis of HCM was determined by the presence of left ventricular concentric hypertrophy ≥6 mm on echocardiography.

Results

There were statistically significant differences in LV mass (healthy = 5.87 g, HCM = 10.3 g, P < .0001), native T1 mapping (healthy = 1122 ms, HCM = 1209 ms, P = .004), and ECV (healthy = 26.0%, HCM = 32.6%, P < .0001). Variables of diastolic function including deceleration time of early diastolic transmitral flow (DTE), ratio between peak velocity of early diastolic transmitral flow and peak velocity of late diastolic transmitral flow (E : A), and peak velocity of late diastolic transmitral flow (A wave) were significantly correlated with ECV (DTE; r = 0.73 P = .007, E : A; r = −0.75 P = .004, A wave; r = 0.76 P = .004).

Conclusions and Clinical Importance

Quantitative assessment of cardiac ECV is feasible and can provide additional information not available using echocardiography.