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.

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.

Comparison of three two-dimensional echocardiographic methods of assessing left ventricular size in Doberman Pinschers.

INTRODUCTION: Compare three methods of obtaining linear left ventricular dimensions within the same Doberman Pinscher (DP). ANIMALS: One hundred and thirty-nine client-owned DP. MATERIALS AND METHODS: Linear left ventricular dimensions were measured using two-dimensional short-axis (Sx-2D), motion-mode short-axis (Sx-MM), and motion-mode long-axis (Lx-MM) methods, then left ventricular volumes were obtained using monoplane Simpson's method of discs (SMOD). A Friedman test with Dunn's multiple comparisons was used to compare differences between methods. Bias and correlation were evaluated via Bland-Altman and Spearman's correlation. Sensitivity and specificity for diagnosing occult dilated cardiomyopathy (DCM) compared to SMOD were determined. Coefficients of variation (CVs) were calculated for intra- and inter-observer measurement variability. RESULTS: There were significant differences between all linear dimensions in diastole and systole. Short-axis 2D measurements had significant bias compared with Sx-MM (diastole +1.19 mm, systole +1.65 mm) and Lx-MM (diastole +4.36 mm, systole +3.87 mm) as did Sx-MM compared with Lx-MM (diastole +3.17 mm, systole +2.22 mm). All linear dimensions had a moderate positive correlation with SMOD. The sensitivity and specificity of linear measurements to detect DCM were: Sx-2D (sensitivity 72.0%, specificity 88.5%), Sx-MM (sensitivity 52.0%, specificity 92.0%), and Lx-MM (sensitivity 37.5%, specificity 99.1%). All methods had acceptably low CV for intra- and inter-observer measurement variability. CONCLUSIONS: Results of this study suggest that linear measurements are repeatable and correlate with reference standard; however, there is a significant bias between measurements, and they should not be used interchangeably.

Palliative combined cutting and high-pressure balloon valvuloplasty in six dogs with severe, symptomatic subaortic stenosis.

INTRODUCTION/OBJECTIVES: Severe subaortic stenosis (SAS) is a congenital heart defect in dogs that often results in clinical signs and reduced survival. The objective of this study was to describe characteristics of dogs with severe, symptomatic SAS who underwent combined cutting and high-pressure balloon valvuloplasty (CB/HPBV). ANIMALS, MATERIALS, AND METHODS: Retrospective description of the clinical characteristics, CB/HPBV procedural deviations from reported methodology and outcomes in a series of six client-owned dogs with severe, symptomatic SAS. RESULTS: Breeds included two each of Newfoundland, Golden retriever, and German shepherd. Median age was 10.1 months (range: 5-72.3 months), and median weight was 25.5 kg (range: 21.8-36.4 kg). Before CB/HPBV, clinical signs were present in all dogs; four were managed for congestive heart failure (CHF). Three dogs had concurrent congenital heart disease. Median Doppler-estimated left ventricular outflow tract pressure gradient was pre-operatively 149.7 mmHg (range: 89.9-254.7 mmHg) and post-operatively 134.1 mmHg (range: 83.9-181.2 mmHg). Median aortoseptal angle was steep at 136° (range: 109-143°). Clinical improvement was documented in all dogs, based on temporary discontinuation of diuretics and/or owner-perceived reduction in clinical signs. At the time of writing, three dogs had died suddenly, one was euthanized because of recurrence of clinical signs, and one died in CHF. Median survival time was 26.4 months after procedure (range: 6.3-45.8 months). One dog remained alive at 44 months after procedure. CONCLUSIONS: Palliative CB/HPBV is a potential therapeutic option for dogs with severe, symptomatic SAS complicated by concurrent congenital heart disease, arrhythmias, or CHF.

Reference intervals and echocardiographic findings in Leonberger dogs.

INTRODUCTION: Leonbergers are large-breed dogs believed to be predisposed to dilated cardiomyopathy, yet the normal echocardiographic measurements of these dogs are unknown. The aim of this study was to describe echocardiographic findings and propose breed-specific reference intervals (RIs) for Leonbergers. ANIMALS: A total of 42 clinically healthy dogs were involved in this study. MATERIALS AND METHODS: This study was designed as a cross-sectional study of 42 Leonberger dogs undergoing complete transthoracic echocardiographic studies at a national show. Reference intervals were determined using robust method with bootstrapping. The effects of age, sex, and body weight (BW) on linear and volumetric dimensions were evaluated by regression analysis. Intra- and interobserver variability were evaluated by coefficient of variation from 10 of the studies. RESULTS: There were significant linear correlations with BW for many of the cardiac variables evaluated. However, despite the statistical significance, most regression equations had small slopes, necessitating large changes in BW for small changes in two-dimensional echocardiographic variables. As such, this study resulted in breed-specific RIs irrespective of BW. Trace mitral insufficiency (n = 18), trace aortic insufficiency (n = 15), or both (n = 1) was identified in 81% of dogs in this population. Coefficients of variation were <9% for all two-dimensional, volumetric, and motion mode measurements. CONCLUSIONS: This study describes echocardiographic findings and provides RIs, which may be useful in echocardiographic evaluations of Leonbergers and may aid in early identification of heart disease within the breed.

Quantitative assessment of two- and three-dimensional transthoracic and two-dimensional transesophageal echocardiography, computed tomography, and magnetic resonance imaging in normal canine hearts.

INTRODUCTION: The objective of the study was to evaluate the accuracy of two- and three-dimensional (2D, 3D) transthoracic echocardiography (TTE), 2D transesophageal echocardiography, and computed tomography angiography (CTA) compared with cardiac magnetic resonance imaging (CMR) in normal dogs and to assess repeatability of 2D and 3D TTE for the assessment of left ventricular (LV) and left atrial (LA) dimensions. ANIMALS: The study was performed on six healthy dogs. MATERIALS AND METHODS: Transthoracic echocardiography, transesophageal echocardiography, CTA, and CMR were performed on each dog. Right ventricular (RV) and LV volumes (in systole and diastole), ejection fraction (EF), and LA and right atrial (RA) volumes were assessed. Repeatability and intrarater and interrater measurements of variability were quantified by average coefficient of variation (CV) for 2D and 3D TTE. RESULTS: No clinically relevant differences in LV volume were detected between CMR and all modalities. Importantly, 3D TTE had the lowest CV (6.45%), correlated with (rs = 0.62, p = 0.01), and had the highest overlap in distribution with CMR (OVL >80%). Left ventricular EF and LA size via CTA compared best with CMR and RV and RA volumes were best estimated by 3D TTE. Assessment of LV and LA volumes via 3D TTE had moderate repeatability (15-21%) compared with LV M-mode measurements and 2D LA-to-aortic ratio (<10%), respectively. For LV size, interrater CV for 3D TTE (19.4%) was lower than 2D TTE (23.1%). CONCLUSIONS: Measurements of LV, RV, and RA volumes via 3D TTE and LA volume and LV EF assessed by CTA compared best with CMR. Three-dimensional echocardiography had lower interrater and intrarater CV compared with 2D TTE.

Development of a perceived exertion scale for dogs using selected physiologic parameters.

OBJECTIVE: To develop a perceived exertion scale for dogs exercising on a treadmill and to assess intra- and inter-observer variability. MATERIALS AND METHODS: Fifteen healthy client-owned dogs participated in paired exercise trials. Measurements of lactate, glucose, heart rate, temperature, respiratory rate and regional tissue oximetry were obtained before, during and after exercise. Perceived exertion scale scores were recorded during exercise and using video recordings to evaluate inter-observer variability. Correlations were evaluated using the Spearman's non-parametric method. RESULTS: Thirteen dogs completed both trials. Dogs walked or trotted on the treadmill with an average perceived exertion score of 2 in both trials. Holter heart rate was positively correlated with perceived exertion scale scores from all observers for both trials. In trial 1, plasma glucose decreased in association with increase in perceived exertion and, in trial 2, cutaneous oximetry decreased, respiratory rate increased and temperature increased with increases on the perceived exertion scale. Inter-observer perceived exertion scale scores were positively correlated in both trials. There was no intra-observer variability between trials. CLINICAL SIGNIFICANCE: The perceived exertion scale correlated with the measured physiologic parameters in dogs exercising at mild to moderate intensity. The perceived exertion scale was consistent and repeatable but larger study numbers and further validation are needed before it can be widely applied.

Designing medical devices for conformance with harmonized standards. The European Community's Medical Devices Directives and their effect on the product development process.

The European Community's Medical Devices Directives represent an ambitious effort to streamline the regulation of medical devices within the European Economic Area, and area comprising more than 380 million people. In this, the first of two special reports, Richard C. Fries and Mark D. Graber describe the Medical Devices Directives and their effect on the product development process. In the second report, appearing on page 294 Jean A. Goggins uses a case study format to demonstrate the process that would be used to gain European approval for a hypothetical medical device.