Two-dimensional echocardiographic estimates of left atrial function in healthy dogs and dogs with myxomatous mitral valve disease

Objectives

To provide reference intervals for 2-dimensional linear and area-based estimates of left atrial (LA) function in healthy dogs and to evaluate the ability of estimates of LA function to differentiate dogs with subclinical myxomatous mitral valve disease (MMVD) and similarly affected dogs with congestive heart failure (CHF).

Quantification of mitral valve regurgitation in dogs with degenerative mitral valve disease by use of the proximal isovelocity surface area method

OBJECTIVE: To determine the within-day and between-day variability of regurgitant fraction (RF) assessed by use of the proximal isovelocity surface area (PISA) method in awake dogs with degenerative mitral valve disease (MVD), measure RF in dogs with MVD, and assess the correlation between RF and several clinical and Doppler echocardiographic variables. DESIGN: Prospective study. ANIMALS: 6 MVD-affected dogs with no clinical signs and 67 dogs with MVD of differing severity (International Small Animal Cardiac Health Council [ISACHC] classification). PROCEDURES: The 6 dogs were used to determine the repeatability and reproducibility of the PISA method, and RF was then assessed in 67 dogs of various ISACHC classes. Mitral valve regurgitation was also assessed from the maximum area of regurgitant jet signal-to-left atrium area (ARJ/LAA) ratio determined via color Doppler echocardiographic mapping. RESULTS: Within- and between-day coefficients of variation of RF were 8% and 11%, respectively. Regurgitation fraction was significantly correlated with ISACHC classification and heart murmur grade and was higher in ISACHC class III dogs (mean +/- SD, 72.8 +/- 9.5%) than class II (57.9 +/- 20.1%) or I (40.7 +/- 19.2%) dogs. Regurgitation fraction and left atriumto-aorta ratio, fractional shortening, systolic pulmonary arterial pressure, and ARJ/LAA ratio were significantly correlated. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggested that RF is a repeatable and reproducible variable for noninvasive quantitative evaluation of mitral valve regurgitation in awake dogs. Regurgitation fraction also correlated well with disease severity. It appears that this Doppler echocardiographic index may be useful in longitudinal studies of MVD in dogs.     

Holter monitoring in 36 dogs with myxomatous mitral valve disease

Objective Describe the presence of arrhythmias in dogs with myxomatous mitral valve disease (MMVD) and the potential association with class of heart failure and left atrial enlargement. Compare the standard electrocardiogram (ECG) with Holter monitoring for assessing heart rate (HR). Experimental procedure The study group of 36 dogs weighing less than 20 kg was divided into MMVD and no clinical signs (preclinical) or MMVD and clinical signs (clinical). A standard echocardiogram, ECG and 24-h Holter recording were obtained in all dogs. Results Minimum and mean Holter HRs were higher in the clinical group than in the preclinical group. Clinical dogs had more ventricular arrhythmias than preclinical dogs. An enlarged left atrium was associated with the presence of more supraventricular arrhythmias. Conclusions Arrhythmias are a common finding in dogs with MMVD and Holter monitoring is a reliable tool for both HR monitoring and diagnosis.     

Left atrial volume and function in dogs with naturally occurring myxomatous mitral valve disease

Objective

Myxomatous mitral valve disease (MMVD) induces progressive left atrial (LA) enlargement. The LA modulates left ventricular filling and performance through its reservoir, conduit, and contractile function. Assessment of LA size and function may provide valuable information on the level of cardiac compensation. Left atrial function in dogs with naturally occurring MMVD remains largely unexplored. The objective of this study was to evaluate LA volume and function in dogs with naturally occurring MMVD.

Survival characteristics and prognostic variables of dogs with mitral regurgitation attributable to myxomatous valve disease

BACKGROUND: There are few studies evaluating the natural history and prognostic variables in chronic mitral valve disease (CMVI) in a heterogeneous population of dogs. OBJECTIVES: To estimate survival and prognostic value of clinical and echocardiographic variables in dogs with CMVI of varying severity. Five hundred and fifty-eight dogs belonging to 36 breeds were studied. METHODS: Dogs were included after clinical examination and echocardiography. Long-term outcome was assessed by telephone interview with the owner. RESULTS: The mean follow-up time was 22.7 +/- 13.6 months, and the median survival time was 19.5 +/- 13.2 months. In univariate analysis, age>8 years, syncope, HR>140 bpm, dyspnea, arrhythmias, class of heart failure (International Small Animal Cardiac Health Council), furosemide therapy, end-systolic volume-index (ESV-I)>30 mL/m(2), left atrial to aortic root ratio (LA/Ao)>1.7, E wave transmitral peak velocity (Emax)>1.2 m/s, and bilateral mitral valve leaflet engagement were associated with survival time when all causes of death were included. For the cardiac-related deaths, all the previous variables except dyspnea and EDV-I>100 mL/m(2) were significantly associated with survival time. Significant variables in multivariate analysis (all causes of death) were syncope, LA/Ao>1.7 m/s, and Emax>1.2 m/s. For cardiac-related death, the only significant variable was LA/Ao>1.7. CONCLUSIONS AND CLINICAL IMPORTANCE: Mild CMVI is a relatively benign condition in dogs. However, some clinical variables can identify dogs at a higher risk of death; these variables might be useful to identify individuals that need more frequent monitoring or therapeutic intervention.     

QT instability,an indicator of augmented arrhythmogenesis,increases with the progression of myxomatous mitral valve disease in dogs

Objectives

To investigate QT instability in dogs with myxomatous mitral valve disease (MMVD) and to determine if this is associated with arrhythmogenesis.

Aldosterone breakthrough in dogs with naturally occurring myxomatous mitral valve disease

Introduction

Aldosterone breakthrough (ABT) is the condition in which angiotensin converting enzyme inhibitors (ACEIs) and/or angiotensin receptor blockers fail to effectively suppress the activity of the renin angiotensin aldosterone system. The objective of this study was to determine if ABT occurs in dogs with naturally occurring myxomatous mitral valve disease receiving an ACEI, using the urine aldosterone to creatinine ratio (UAldo:C) as a measure of renin angiotensin aldosterone system activation.

Plasma and platelet serotonin concentrations in healthy dogs and dogs with myxomatous mitral valve disease

ObjectivesSerotonin has been implicated in canine myxomatous mitral valve disease (MMVD); however, the sources of serotonin have not been fully elucidated. This study compared the concentration of serotonin in plasma and platelets of normal healthy small breed dogs with predisposition to MMVD and dogs with naturally occurring MMVD.Animals43 small-breed client-owned dogs with an approximate weight of <10 kg and age of 6 years or above were divided into 2 groups: a healthy control group (n = 20) and a group with echocardiographic evidence of MMVD (n = 23).Methods5 ml samples of blood were collected. Plasma and platelets were separated by centrifugation and assayed for serotonin measured by enzyme linked immunosorbent assay (ELISA).ResultsMedian plasma serotonin concentration was not significantly different (p = 0.3630) between normal healthy dogs (3.7 ng/ml) and dogs with MMVD (4.3 ng/ml). Males had higher plasma serotonin concentration than females (4.7 and 2.9 ng/ml respectively, p = 0.0043). Platelet serotonin concentration was not different between healthy dogs and dogs with MMVD (128.6 ng/10⁹ platelets and 176.6 ng/10⁹ platelets respectively, p = 0.4575). Age, echocardiographic indices and platelet count showed no correlation with plasma or platelet serotonin concentration.ConclusionsCirculating plasma serotonin is unlikely a major source of serotonin signaling in canine MMVD. Platelets could be a source of serotonin in canine MMVD through platelet adhesion to the mitral valve; however, the amount of serotonin stored in platelets of healthy dogs and dogs with MMVD is not different.     

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.     

Mitral valve morphology assessed by three-dimensional transthoracic echocardiography in healthy dogs and dogs with myxomatous mitral valve disease

Objective

To assess differences in morphology of the mitral valve (MV) between healthy dogs and dogs affected by myxomatous mitral valve disease (MMVD) using real-time transthoracic three-dimensional echocardiography (RT3DE).

ACVIM consensus guidelines for the diagnosis and treatment of myxomatous mitral valve disease in dogs

This report, issued by the ACVIM Specialty of Cardiology consensus panel, revises guidelines for the diagnosis and treatment of myxomatous mitral valve disease (MMVD, also known as endocardiosis and degenerative or chronic valvular heart disease) in dogs, originally published in 2009. Updates were made to diagnostic, as well as medical, surgical, and dietary treatment recommendations. The strength of these recommendations was based on both the quantity and quality of available evidence supporting diagnostic and therapeutic decisions. Management of MMVD before the onset of clinical signs of heart failure has changed substantially compared with the 2009 guidelines, and new strategies to diagnose and treat advanced heart failure and pulmonary hypertension are reviewed.     

Proximal isovelocity surface area variability during systole in dogs with mitral valve prolapse

The proximal isovelocity surface area (PISA) principles and methodology have been described in human and veterinary medicine with special emphasis given to the ease and speed for the quantification of mitral regurgitation. Although limitations have been described in both human and veterinary medicine, in the case of veterinary medicine, clinical examples have not been well defined and in some cases have not been individually presented. The objective of this paper is to illustrate in a qualitative manner the echocardiographic existence of the dynamic behavior and variability of mitral regurgitation in dogs with mitral valve prolapse, a factor to be taken into consideration as a limitation inherent to the PISA technique.     

Anatomic regurgitant orifice area obtained using 3D-echocardiography as an indicator of severity of mitral regurgitation in dogs with myxomatous mitral valve disease

Objectives

To determine feasibility and repeatability of measuring the anatomic regurgitant orifice area (AROA) using real-time three-dimensional transthoracic echocardiography (RT3DE) in dogs with myxomatous mitral valve disease (MMVD), and to investigate differences in the AROA of dogs with different disease severity and in different American College of Veterinary Internal Medicine (ACVIM) stages.

Effect of sampling time on urinary electrolytes following oral furosemide administration in dogs with myxomatous mitral valve disease

Introduction/ObjectivesUrine chemistry has received growing attention to estimate the diuretic response in dogs with cardiac disease.The aim of the study was to evaluate the impact of time elapsed between the oral furosemide administration and sample collection on urine chemistry in dogs with myxomatous mitral valve disease (MMVD) receiving diuretic therapy in American College of Veterinary Internal Medicine (ACVIM) stage C.Materials and methodsSeventy-three dogs with MMVD ACVIM stage C and 106 healthy dogs were prospectively included. Dogs with MMVD were divided, based on the time of sampling, in morning group (MMVD-MG) of one to 6 h and an evening group (MMVD-EG) over 6 h from oral furosemide administration. Analogously, healthy dogs sampled between 9 a.m. and 1 p.m. and between 2 and 7 p.m. were divided in a morning group (H-MG) and an evening group (H-EG), respectively. Urine chemistry, including fractional excretion of electrolytes, was evaluated and compared among groups.ResultsHigher excretion of sodium and chloride and higher urine sodium to urine potassium ratio (uNa⁺:uK⁺) were detected in MMVD-MG than MMVD-EG (P = 0.021, P = 0.038, and P = 0.016, respectively). Natriuresis, chloriuresis, and uNa⁺:uK+ were higher in MMVD-MG than H-MG, while no differences were found in the comparison between H-MG and H-EG and between MMVD-EG and H-EG.ConclusionsUrinary electrolyte excretion is significantly increased within 6 h from furosemide administration in MMVD ACVIM stage C dogs. Time of sampling from furosemide administration significantly affects urine chemistry in MMVD dogs and should be considered in clinical practice and the research field.