Effects of age, body weight, and heart rate on transmitral and pulmonary venous flow in clinically normal dogs

Left-to-Left Acquired Cardiac Shunt: Aorto-Left Atrial Fistula Due to Aortic Infective Endocarditis in a Dog

Infective endocarditis is a severe but rarely diagnosed disease, characterized by the presence of bacterial infection at the level of the cardiac valves. Although the incidence of the disease is very low, the consequences are severe and the prognosis is very poor, outlining a high mortality rate among cases. The present report highlights the case of a 7-year-old dog presented with abrupt changes in the respiratory pattern, obtunded and in lateral recumbency. The physical examination of the patient revealed fever and a IV/VI systolic heart murmur, with the point of maximal intensity on the left hemithorax. Echocardiography identified hyperechoic and cavitary changes beneath the aortic valves and a retrograde turbulent jet originating in the left ventricle outflow tract communicating with the left atrium through a rupture in the aortomitral intervalvular wall. Because of very unstable hemodynamic changes, the dog suddenly died despite the initiation of intensive care supportive treatment, and the postmortem evaluation of the heart confirms the suspicion of infective aortic endocarditis with the development of a paravalvular abscess and an aorto-left atrial fistula.

Longitudinal analysis of echocardiographic and cardiac biomarker variables in dogs with atrial fibrillation: The optimal rate control in dogs with atrial fibrillation II study

BACKGROUND

Rate control (RC; meanHRHolter ≤ 125 bpm) increases survival in dogs with atrial fibrillation (AF). The mechanisms remain unclear.

HYPOTHESIS/OBJECTIVES

Investigate echocardiographic and biomarker differences between RC and non-RC (NRC) dogs. Determine if changes post-anti-arrhythmic drugs (AAD) predict successful RC in subsequent Holter monitoring. Evaluate if early vs late RC affects survival.

ANIMALS

Fifty-two dogs with AF.

METHODS

Holter-derived mean heart rate, echocardiographic and biomarker variables from dogs receiving AAD were analyzed prospectively at each re-evaluation and grouped into RC or NRC. The primary endpoint was successful RC. Between group comparisons of absolute values, magnitude of change from admission to re-evaluations and end of study were performed using Mann-Whitney tests or unpaired t-tests. Logistic regression explored variables associated with inability to achieve RC at subsequent visits. Kaplan-Meier survival analysis was used to compare survival time of early vs late RC.

RESULTS

At visit 2, 11/52 dogs were RC; at visit 3, 14/52 were RC; and at visit 4, 4/52 were RC. At the end of study, 25/52 remained NRC. At visit 2, both groups had increased cardiac dimensions, but NRC dogs had larger dimensions; biomarkers did not differ. At the end of study, RC showed decreased cardiac dimensions and end-terminal pro-brain natriuretic peptide (NT-proBNP) compared with NRC. No variables were useful at predicting RC success in subsequent visits. Survival analysis found no differences between early vs late RC.

CONCLUSIONS AND CLINICAL IMPORTANCE

The RC dogs had decreased cardiac dimensions and NT-proBNP, suggesting HR-mediated reverse-remodeling might benefit survival, even with delayed RC achievement. Pursuit of RC is crucial despite initial failures.

Echocardiographic Documentation of Dilated Cardiomyopathy Development in Dogs Naturally Infected with Trypanosoma cruzi

We aimed to characterize the echocardiographic alterations in dogs from an endemic region that were naturally infected with T. cruzi. Dogs (n = 130) seropositive for antibodies against T. cruzi and/or with acute parasitemia were enrolled in the study. Indicators of changes in the structure and systolic and diastolic functions of the left ventricle (LV) and blood flow patterns were evaluated by echocardiography. The frequency and extent of alterations in these indicators were associated with the severity of the disease. Briefly, 15 (11.54%) dogs were diagnosed with dilated cardiomyopathy (DCM), and 115 (88.46%) dogs were diagnosed as being without DCM. Infected dogs with DCM exhibited structural features of LV dysfunction, e.g., a significant (p < 0.05) increase in the LV internal diameter at systole and diastole (LVID-s, LVID-d) and a decline in the LV posterior wall (LVPW-d) thickness at diastole. Despite an increase in stroke volume and cardiac output indicating contraction force, DCM resulted in a decreased ejection fraction, affecting systolic function. Dogs that were diagnosed as DCM-negative but were positive for T. cruzi by PCR exhibited a high frequency of an increase in the thickness of the interventricular septum in systole (IVS-s) and the LV posterior wall in diastole (LVPW-d), a decline in the LV inner diameter (LVID-d, LVID-s), and fractional shortening (FS). The thinning of the LVPW at systole was the most defining feature observed in chronically infected dogs. In summary, this is the first study reporting the echocardiographic changes occurring in dogs naturally infected with T. cruzi and developing DCM. Our data suggest that changes in LVID are a major indicator of risk of cardiac involvement, and the observation of changes in the IVS, LVPW, and FS have predictive value in determining the risk of DCM development in infected dogs.

Echocardiographic findings in apparently healthy Czechoslovakian wolfdogs

INTRODUCTION

To echocardiographically evaluate a large number of apparently healthy Czechoslovakian wolfdogs (CWDs) to identify possible subclinical cardiac abnormalities and to generate reference intervals.

ANIMALS

One-hundred and seventeen apparently healthy client-owned CWDs.

MATERIALS AND METHODS

Standard two-dimensional, M-mode, and Doppler echocardiographic measurements were obtained on non-sedated, manually restrained standing dogs. Animals with no relevant echocardiographic abnormalities were used to generate reference intervals. Echocardiographic variables were compared between males and females and between dogs with and without mitral regurgitation (MR).

RESULTS AND DISCUSSION

Among the 117 CWDs, 103 dogs were used to generate reference intervals. The 14 dogs with abnormalities had more than trivial MR (12 dogs), subaortic stenosis (one dog), and equivocal subaortic stenosis (one dog). The 44 males were heavier than 59 females (P<0.001) and had a larger maximum left atrial dimension (P=0.015), left ventricular internal dimension at end-diastole (P<0.001) and systole (P<0.001), and thicker interventricular septum thickness at end-diastole (P=0.016). A positive linear correlation was identified between bodyweight and aortic root and left atrial diameters and left ventricular dimensions and between age and aortic root and left atrial diameter and peak late transmitral flow velocity. A negative linear correlation was identified between age and peak early transmitral flow velocity and the ratio between peak early and late transmitral flow velocities. No differences in echocardiographic-derived cardiac dimensions were detected between healthy dogs and dogs with more than trivial MR.

CONCLUSIONS

In this population of CWDs, subclinical cardiac abnormalities were uncommon, and they were mainly classified as MR.

Hypertrophic cardiomyopathy in a dog: a systematic diagnostic approach

A seven-year-old female neutered Parson Russel Terrier was referred for syncopal episodes. An electrocardiogram revealed paroxysmal atrial flutter followed by periods of sinus arrest, suggesting sick sinus syndrome. Echocardiography showed severe biventricular wall thickening (hypertrophic cardiomyopathy (HCM) phenotype) with no signs of fixed or dynamic left ventricular outflow tract obstruction. Blood pressure, abdominal ultrasound, serum total thyroxin and thyroid-stimulating hormone, and insulin-like growth factor-1 were all within normal limits. Cardiac troponin I was elevated (1.7 ng/mL, ref<0.07). Serological tests for common infectious diseases were negative. A 24-h Holter confirmed that the syncopal episodes were associated with asystolic pauses (sinus arrest after runs of atrial flutter) ranging between 8.5 and 9.6 s. Right ventricular endomyocardial biopsies (EMB) were performed at the time of pacemaker implantation to assess for storage or infiltrative diseases that mimic HCM in people. Histological analysis of the EMB revealed plurifocal inflammatory infiltrates with macrophages and lymphocytes (CD3+ > 7/mm2) associated with myocyte necrosis, but no evidence of myocyte vacuolisation or infiltrative myocardial disorders. These findings were compatible with myocardial ischaemic injury or acute lymphocytic myocarditis. Molecular analysis of canine cardiotropic viruses were negative. The dog developed refractory congestive heart failure and was euthanised 16 months later. Cardiac post-mortem examination revealed cardiomyocyte hypertrophy and disarray with diffuse interstitial and patchy replacement fibrosis, and small vessel disease, confirming HCM. We described a systemic diagnostic approach to an HCM phenotype in a dog, where a diagnosis of HCM was reached by excluding HCM phenocopies.

A masked, placebo-controlled, randomized clinical trial evaluating safety and the effect on cardiac function of low-dose rapamycin in 17 healthy client-owned dogs

Introduction

Geroscience studies of low-dose rapamycin in laboratory species have identified numerous benefits, including reversing age-related cardiac dysfunction. Cardiovascular benefits have been observed in dogs with 10 weeks of treatment, raising questions about possible benefits and adverse effects of long-term use of low-dose rapamycin. The objectives of this study were to assess the impact of 6 months of low-dose rapamycin on echocardiographic indices of cardiac function in healthy dogs and to document the occurrence of adverse events.

Methods

Seventeen client-owned dogs aged 6-10 years, weighing 18-36 kg, and without significant systemic disease were included in a prospective, randomized, placebo-controlled, masked clinical trial. Low-dose rapamycin (0.025 mg/kg) or placebo was administered three times per week for 6 months. Baseline, 6-month, and 12-month evaluation included physical examination, cardiology examination, and clinicopathology. Three-month evaluation included physical examination and clinicopathology. Owners completed online questionnaires every 2 weeks.

Results

There were no statistically significant differences in echocardiographic parameters between rapamycin and placebo groups at 6 or 12 months. No clinically significant adverse events occurred. In 26.8% of the bi-weekly surveys owners whose dogs received rapamycin reported perceived positive changes in behavior or health, compared to 8.1% in the placebo group (p = 0.04).

Discussion

While no clinically significant change in cardiac function was observed in dogs treated with low-dose rapamycin, the drug was well-tolerated with no significant adverse events.

Echocardiographic values for normal conditioned and unconditioned North American whippets

BACKGROUND

Echocardiographic reference intervals have not been reported for North American whippets, or for whippets that have undergone pet-level athletic training.

OBJECTIVES

To develop normal echocardiographic reference intervals for North American whippets and investigate differences in echocardiographic parameters based on athletic conditioning in pet whippets engaged in competitive sports.

ANIMALS

One-hundred healthy North American whippets.

METHODS

Dogs were examined at national shows between 2005 and 2009. Echocardiographic reference intervals were constructed and the effect of athletic conditioning on parameters of structure and function was assessed.

RESULTS

Two dimensional, M-mode, Doppler and tissue Doppler reference ranges for healthy North American whippets are presented. Measures of left ventricular (LV) chamber diameter were larger in conditioned whippets (N = 25) and remained significantly larger than in unconditioned whippets (N = 16) when normalized for weight using allometric equations. Calculated LV mass was higher in conditioned dogs than in unconditioned dogs, and this difference persisted when LV mass was normalized by weight. Mitral E velocity was higher in conditioned dogs than in unconditioned dogs, whereas E/A and measures related to systolic function were not different.

CONCLUSIONS AND CLINICAL IMPORTANCE

Pet whippets in peak athletic condition have larger hearts than do less conditioned whippets, but measures of systolic function are similar. Whippet pet athletes may show eccentric LV hypertrophy at peak condition. Normal values for cardiac size and function in North American whippets might be considered abnormal if population-specific whippet reference intervals are not used in analysis.

Beraprost Sodium for Pulmonary Hypertension in Dogs: Effect on Hemodynamics and Cardiac Function

Simple Summary

Pulmonary hypertension is a potentially life-threatening disease among dogs that is characterized by increased pulmonary arterial pressure and pulmonary vascular resistance. In veterinary medicine, a phosphodiesterase-5 inhibitor such as sildenafil is the most common drug used to treat pulmonary hypertension. However, the availability of sildenafil is limited because of its high cost, difficulty in obtaining the drug in some areas, and potential inter-individual variability in the response to sildenafil therapy. Beraprost sodium is one of the most common drugs used to treat pulmonary hypertension in humans. However, little is known about its efficacy in dogs with pulmonary hypertension. In this study, beraprost sodium showed significant pulmonary and systemic vasodilation without any adverse effects in sixteen dogs with pulmonary hypertension. Additionally, echocardiographic improvements in cardiac function and pulmonary and systemic circulation were observed. These results emphasize the potential efficacy of beraprost sodium in treating canine pulmonary hypertension.

Abstract

Pulmonary hypertension (PH) is a fatal condition that affects many dogs. In humans, PH is often treated with beraprost sodium (BPS). However, the effectiveness of BPS for canine PH has not been established. This study aimed to evaluate the clinical and cardiovascular response of BPS in canine patients with PH of various causes. Sixteen dogs with PH (post-capillary PH, n = 8; pre-capillary PH, n = 8) were included. BPS was continuously administered twice daily at 15 µg/kg. All dogs underwent echocardiography, including speckle-tracking analysis and blood pressure measurement, before and after BPS administration. Continuous BPS administration (range: 13.2–22.0 µg/kg) significantly decreased the pulmonary and systemic vascular impedance and increased left and right ventricular myocardial strain. In dogs with post-capillary PH, BPS administration caused no significant worsening of the left atrial pressure indicators. No side effects of BPS were observed in any dog. BPS also improved cardiac function and pulmonary circulation through pulmonary vasodilation, suggesting that BPS may be an additional treatment option for canine PH of various causes. Particularly, BPS increased left ventricular function and systemic circulation without worsening the left heart loading condition in dogs with post-capillary PH.

Evaluation of Right Ventricular Function and Dyssynchrony in a Dog Model of Acute Pulmonary Embolism: Diagnostic Utility and Reversibility

Background

The diagnosis of acute pulmonary thromboembolism is challenging in dogs. Little has been reported on changes in echocardiographic indices in dogs with acute pulmonary thromboembolism. The objective of this study was to validate the relationship between echocardiographic indices and right heart catheterization variables in dogs with acute pulmonary embolism and to identify a useful echocardiographic index for diagnosing acute pulmonary embolism.

Materials and Methods

Six healthy laboratory beagles were included in the study. Echocardiography and right heart catheterization were performed in a dog model of acute pulmonary embolism produced by microsphere injection. Echocardiographic indices, including the right ventricular (RV) Tei index, RV longitudinal strain, and the dyssynchrony index using speckle tracking echocardiography, transmitral flow, and eccentricity index, were measured.

Results

The mean pulmonary arterial pressure increased (22.2 ± 1.2 mmHg) and the blood pressure decreased after microsphere injection. Although the mean pulmonary arterial pressure remained elevated, the blood pressure recovered 2 days after the microsphere injection. Most echocardiographic indices of RV function were significantly impaired following microsphere injection and recovered after 2 days. In contrast, the RV Tei index was significantly impaired after microsphere injection and the impairment persisted after 2 days. Multivariable analysis revealed that the RV Tei index was an independent echocardiographic predictor of pulmonary vascular resistance (β = 0.88, P < 0.001), and transmitral early diastolic wave was an independent predictor of the cardiac index (β = −0.86, P = 0.001).

Conclusions

The RV Tei index is a useful echocardiographic index for diagnosing acute pulmonary embolism. Ventricular interdependence may be an important factor causing low cardiac output in dogs with acute pulmonary embolism.

Retrospective evaluation of hypertrophic cardiomyopathy in 68 dogs

BACKGROUND

There is a lack of clinical data on hypertrophic cardiomyopathy (HCM) in dogs.

HYPOTHESIS/OBJECTIVES

To investigate signalment, clinical signs, diagnostic findings, and survival in dogs with HCM.

ANIMALS

Sixty-eight client-owned dogs.

METHODS

Retrospective multicenter study. Medical records were searched between 2003 and 2015. The diagnosis of left ventricular (LV) hypertrophy was made by echocardiographic examination.

RESULTS

Three hundred and forty-five dogs with LV hypertrophy were identified, of which 277 were excluded. The remaining 68 dogs were 0.3 to 14 years old and predominantly <10 kg (85%), and without a sex predilection. Twenty-four % were Shih Tzu and 24% terrier breeds. Most (80%) had a systolic heart murmur. Owner-determined exercise intolerance (37%) and syncope (18%) were most commonly reported signs. The majority (84%) of dogs had symmetrical LV hypertrophy, whereas asymmetrical septal and LV free wall hypertrophy was observed in 9% and 6% of dogs, respectively. Isolated basal interventricular septal hypertrophy was not observed. Commonly recorded were systolic anterior motion of the mitral valve (60%) and LV diastolic dysfunction (89% of dogs where diastolic function was evaluated). Six dogs died unexpectedly, and 3 developed congestive heart failure. Known survival times were between 1 day and 114 months after diagnosis.

CONCLUSIONS AND CLINICAL IMPORTANCE

Hypertrophic cardiomyopathy in dogs should be considered as a differential diagnosis if LV hypertrophy is identified. Small breed dogs are overrepresented, and it is uncommon for dogs with HCM to develop CHF although sudden death can occur.

Conditioning Program Prescribed from the External Training Load Corresponding to the Lactate Threshold Improved Cardiac Function in Healthy Dogs

This research focuses on the adjustments in systolic and diastolic functions that are not fully understood in dogs submitted to athletic training. Beagle dogs carried out an endurance training program (ETP) prescribed from the external training load, corresponding to 70-80% of the lactate threshold (VLT) velocity. Eighteen dogs were randomly assigned to two groups: control (C, n = 8), active dogs that did not perform any forced exercise, and trained (T, n = 10), submitted to the ETP during eight weeks. All dogs were evaluated before and after the ETP period using two-dimensional echocardiography, M-mode, Doppler, and two-dimensional speckle tracking. A principal component analysis (PCA) of the echocardiographic variables was performed. The ETP improved the left ventricular internal dimension at the end of diastole (LVDd), the left ventricular internal dimension at the end of diastole to aorta ratio (LVDd: Ao), and the strain rate indices. PCA was able to capture the dimensionality and qualitative echocardiography changes produced by the ETP. These findings indicated that the training prescribed based on the lactate threshold improved the diastolic and systolic functions. This response may be applied to improve myocardial function, promote health, and mitigate any injuries produced during heart failure.

Echocardiographic parameters and indices in 23 healthy Maltese dogs

BACKGROUND

Echocardiography is a primary tool used by veterinarians to evaluate heart diseases. In recent years, various studies have targeted standard echocardiographic values for different breeds. Reference data are currently lacking in Maltese dogs and it is important to fill this gap as this breed is predisposed to myxomatous mitral valve disease, which is a volume overload disease.

OBJECTIVES

To establish the normal echocardiographic parameters for Maltese dogs.

METHODS

In total, 23 healthy Maltese dogs were involved in this study. Blood pressure measurements, thoracic radiography, and complete transthoracic echocardiography were performed. The effects of body weight, age and sex were evaluated, and the correlations between weight and linear and volumetric dimensions were calculated by regression analysis.

RESULTS

The mean vertebral heart size was 9.1 ± 0.4. Aside from the ejection fraction, fractional shortening, and the left atrial to aorta root ratio, all the other echocardiographic parameters were significantly correlated with weight.

CONCLUSION

This study describes normal echocardiographic parameters that may be useful in the echocardiographic evaluation of Maltese dogs.

The predictive value of clinical, radiographic, echocardiographic variables and cardiac biomarkers for assessing risk of the onset of heart failure or cardiac death in dogs with preclinical myxomatous mitral valve disease enrolled in the DELAY study

OBJECTIVES

To identify the predictive value on time to onset of heart failure (HF) or cardiac death of clinical, radiographic, and echocardiographic variables, as well as cardiac biomarkers N-terminal pro brain natriuretic peptide (NT-proBNP) and cardiac troponin I in dogs with preclinical myxomatous mitral valve disease (MMVD).

ANIMALS

One hundred sixty-eight dogs with preclinical MMVD and left atrium to aortic root ratio ≥1.6 (LA:Ao) and normalized left ventricular end-diastolic diameter ≥1.7 were included.

METHODS

Prospective, randomized, multicenter, single-blinded, placebo-controlled study. Clinical, radiographic, echocardiographic variables and plasma cardiac biomarkers concentrations were compared at different time points. Using receiving operating curves analysis, best cutoff for selected variables was identified and the risk to develop the study endpoint at six-month intervals was calculated.

RESULTS

Left atrial to aortic root ratio >2.1 (hazard ratio [HR] 3.2, 95% confidence interval [95% CI] 1.9-5.6), normalized left ventricular end-diastolic diameter > 1.9 (HR: 6.3; 95% CI: 3.3-11.8), early transmitral peak velocity (E peak) > 1 m/sec (HR: 3.9; 95% CI: 2.3-6.7), and NT-proBNP > 1500 ρmol/L (HR: 5.7; 95% CI: 3.3-9.5) were associated with increased risk of HF or cardiac death. The best fit model to predict the risk to reach the endpoint was represented by the plasma NT-proBNP concentrations adjusted for LA:Ao and E peak.

CONCLUSIONS

Logistic and survival models including echocardiographic variables and NT-proBNP can be used to identify dogs with preclinical MMVD at higher risk to develop HF or cardiac death.

Effect of a Weight Loss Program on Biochemical and Immunological Profile, Serum Leptin Levels, and Cardiovascular Parameters in Obese Dogs

This study aimed to investigate the effects of a weight loss program (WLP) on biochemical and immunological profile, and cardiovascular parameters in a cohort of dogs with naturally occurring obesity. Eleven obese dogs [body condition scoring (BCS), ≥7/9] were enrolled into the study and underwent clinical and cardiovascular examination, and blood testing before (T0) and after 6 months (T1) of WLP. Eleven normal weight (BCS, 4/5) healthy dogs were used as a control (CTR) group. Compared to the CTR group, at T0 obese dogs expressed higher serum leptin concentrations (p < 0.0005) that significantly decreased after weight loss (p < 0.005) but remained higher than the CTR group. Furthermore, obese dogs showed considerably lower levels (p < 0.0005) of regulatory T cell (Treg) compared to the CTR group, but they did not change after weight loss at T1. In obese dogs, tumor necrosis factor (TNF)-α and interleukin (IL)-6 concentrations were substantially reduced at T1 (p < 0.0001 and p < 0.005). Regarding the cardiovascular parameters, only one obese dog was hypertensive at T0, and systolic blood pressure values showed no significant differences at the end of the WLP. The ratio of interventricular septal thickness in diastole to left ventricle internal diameter in diastole (IVSd/LVIDd) was significantly greater in obese dogs at T0 than in the CTR group (p < 0.005). It decreased after weight loss (p < 0.05). In obese dogs, troponin I level significantly reduced with weight loss (p < 0.05), while endothelin-1 level did not differ statistically. The results suggest that the immune dysregulation in the presence of high leptin levels and reduced number of Treg could affect obese dogs as well as humans. Based on our findings, we may speculate that a more complete immune-regulation restore could be obtained by a greater reduction in fat mass and a longer-term WLP. Finally, left ventricular remodeling may occur in some obese dogs. However, in canine species, further studies are needed to investigate the impact of obesity and related WLP on cardiovascular system.

Two-dimensional, M-mode, and Doppler echocardiography in 22 conscious and apparently healthy pet guinea pigs

OBJECTIVES

The objective of this study was to report normal echocardiographic values in healthy guinea pigs.

ANIMALS, MATERIALS, AND METHODS

Twenty-two privately owned, apparently healthy, conscious guinea pigs underwent complete transthoracic echocardiography. Left ventricular (LV), right ventricular, left atrial, and aortic root dimensions were measured, as were forward flow velocities across the mitral, aortic, and pulmonic valves. The effects of age, body weight, sex, and heart rate on these variables were also investigated.

RESULTS

The median age (interquartile range) was 3.0 (1.8-4.0) years with a body weight of 902 (822-998) grams. Echocardiography was feasible in all conscious animals. Early and late diastolic transmitral flow waves were summated in 17 of 22 individuals. In the remaining five animals, the two waves were reversed (E wave-to-A wave velocity less than 1.0). A positive correlation was detected between body weight and LV internal diameter at end-diastole and end-systole and left atrial diameter (P < 0.05). Heart rate was negatively correlated with LV internal diameter at end-systole (r = -0.463, P = 0.035). Age was positively correlated with LV posterior wall thickness at end-diastole and aortic diameter (P < 0.05). LV internal diameter at end-systole was larger in males than in females (P = 0.012), while fractional shortening was lower (P = 0.008).

CONCLUSIONS

Descriptive echocardiography ranges in apparently healthy awake guinea pigs have been provided and can be used for cardiac assessment in these pet animals.

Clinicopathologic, hemodynamic, and echocardiographic effects of short-term oral administration of anti-inflammatory doses of prednisolone to systemically normal cats

OBJECTIVE

To evaluate the clinicopathologic, hemodynamic, and echocardiographic effects of short-term administration of anti-inflammatory dosages of prednisolone to systemically normal cats.

ANIMALS

10 cats with allergic dermatitis and 10 healthy control cats.

PROCEDURES

Cats with allergic dermatitis were randomly allocated to 2 groups and received 2 dosages of prednisolone (1 and 2 mg/kg/d, PO, for 7 days) in a crossover design followed by 9-day tapering and 14-day washout periods. Each prednisolone-treated cat was matched to a healthy control cat on the basis of sex, neuter status, age (± 1 year), and body weight (± 10%). Control cats received no treatment during the 35-day observation period. Clinicopathologic, echocardiographic, and hemodynamic variables were measured at baseline (day 0) and predetermined times during and after prednisolone administration and compared within and between the 2 treatment groups.

RESULTS

Prednisolone-treated cats had expected clinicopathologic alterations (mild increases in neutrophil and monocyte counts and serum concentrations of albumin, cholesterol, and triglycerides) but systolic arterial blood pressure; blood glucose, serum potassium, and cardiac biomarker concentrations; urinary sodium excretion; and echocardiographic variables did not differ significantly from baseline at any time. Statistically significant, albeit clinically irrelevant, increases in blood glucose and N-terminal pro-B-type natriuretic peptide concentrations were observed between baseline and the prednisolone pharmacokinetic steady state (7 days after initiation) only when the 2-mg/kg dosage was administered.

CONCLUSIONS AND CLINICAL RELEVANCE

Results indicated short-term oral administration of anti-inflammatory dosages of prednisolone did not cause relevant hemodynamic, echocardiographic, or diabetogenic effects in systemically normal cats with allergic dermatitis.

Electrocardiographic and echocardiographic evaluation in dogs with hypothyroidism before and after levothyroxine supplementation: A prospective controlled study

Background

Improvement in cardiac function has been demonstrated after thyroxine treatment in humans with hypothyroidism using the myocardial performance index (MPI). Cardiac changes after thyroxine supplementation are poorly documented in dogs with spontaneous hypothyroidism and comparison with clinically healthy dogs is lacking.

Objectives

To evaluate the electrical activity and mechanical function of the heart in dogs with primary hypothyroidism at baseline (T0) and after thyroxine supplementation (T60).

Animals

Forty client‐owned dogs with hypothyroidism and 20 clinically healthy dogs.

Methods

Prospective cohort study. Selected electrocardiographic and echocardiographic variables, including the MPI, were measured in all dogs at T0 and in 30 hypothyroid dogs at T60.

Results

Hypothyroid dogs had significantly decreased median or mean heart rate (HR), P wave amplitude, and R wave amplitude (P = .04, P = .002, and P = .003, respectively) and E‐point‐to‐septal separation normalized to body weight (EPSSn) and trans‐mitral E wave velocity (E max; P < .001 and P = .025, respectively) at T0 compared to control dogs. At T60, significantly increased median or mean HR, P wave amplitude, fractional shortening, and E max (P < .001, P = .004, P = .002, and P = .009, respectively) and significantly decreased left ventricular end‐diastolic volume index, and normalized systolic diameter and EPSSn (P = .03, P = .03, and P = .001, respectively) were found.

Conclusions and Clinical Importance

Hypothyroidism in dogs induces mild and reversible changes of electromechanical cardiac function. The MPI does not have clinical importance in identifying cardiac dysfunction in affected dogs.

Assessment of left atrial function in dogs with myxomatous mitral valve disease by biplane simpson’s method

ABSTRACT The relationship between the diameter of the left atrium (LA) and aorta (Ao) is considered as a prognostic factor in chronic mitral valve disease. As the left atrium is a three-dimensional structure, methods based on measurement of the chamber volume can be more accurate than linear methods.The aim of this study was to assess the feasibility of measuring LA volume with 2D echocardiography using the biplane modified Simpson (SIMP) method in 33 dogs with various classes of myxomatous mitral valve disease (MMVD), as well as to present values of LA function using the atrial diastolic and systolic volume indices (ADVI and ASVI), cardiac index (ACI) and atrial ejection fraction (AEF). We observed agreement among the LA/Ao ratio and the atrial volume indices (ADVI and ASVI) and the ACI, suggesting that the values of the variables increase as the LA/Ao ratio increases due to atrial remodeling that accompanies MMVD progression. The data demonstrated a good assessment of atrial function, allowing a better understanding of LA's role in the pathophysiology of MMVD.

Changes of cardiac function in diabetic dogs

OBJECTIVE

This study aimed to evaluate cardiac function and compare the concentration of cardiac biomarkers including cardiac troponin I (cTnI), galectin-3 (Gal-3), and N-terminal pro B-type natriuretic peptides (NT-proBNP) in diabetic and control dogs.

ANIMALS

Thirty-nine dogs were included. The diabetic and control groups consisted of 19 and 20 dogs, respectively.

METHODS

Plasma cTnI, Gal-3, and NT-proBNP concentrations were measured in the diabetic and control groups. Echocardiography was performed in all dogs to evaluate cardiac structure and function. Echocardiographic values and cardiac biomarker concentrations between the two groups were compared with the Mann-Whitney U test. The p-value < 0.05 was considered statistical significance.

RESULTS

No evidence of cardiac structural changes was detected in diabetic dogs on two-dimensional echocardiography. The echocardiographic values of diabetic and control dogs were within reference intervals. Echocardiographic changes indicating diastolic dysfunction assessed by spectral flow Doppler echocardiography and tissue Doppler imaging were found in diabetic dogs (42.10%) compared with control dogs (10.00%; p = 0.022). Diabetic dogs with durations of diabetes mellitus > 1 year had an increased left ventricular wall thickness and echocardiographic changes suggesting diastolic dysfunction compared with those with duration of diabetes mellitus < 1 year. No evidence of systolic dysfunction was detected in diabetic dogs. No significant difference in plasma cTnI, Gal-3, and NT-proBNP concentrations was found between the two groups.

CONCLUSIONS

Echocardiographic changes suggested that left ventricular diastolic dysfunction was detected in diabetic dogs without changes in the concentration of cardiac biomarkers including cTnI, Gal-3, and NT-proBNP compared with the age- and breed-matched control dogs.

Echocardiographic evaluation of left ventricular diastolic function in cats: Hemodynamic determinants and pattern recognition

Left ventricular (LV) diastolic dysfunction is highly prevalent in cats and is a functional hallmark of feline cardiomyopathy. The majority of cats with hypertrophic, restrictive, and dilated cardiomyopathy have echocardiographic evidence of abnormal LV filling, even during the occult (preclinical) phase. Moderate and severe diastolic dysfunction is an indicator of advanced myocardial disease, is associated with clinical signs including exercise intolerance and congestive heart failure, affects outcome, and influences therapeutic decisions. Therefore, identification and quantification of LV diastolic dysfunction are clinically important. Surrogate measures of diastolic function determined by transthoracic two-dimensional, M-mode, and Doppler echocardiographic (DE) methods have been used widely for such purpose. Major functional characteristics of LV diastole, including global function, relaxation and untwist, chamber compliance, filling volume, and the resultant filling pressures can be semi-quantified by echocardiographic methods, and variables retrieved from transmitral flow, pulmonary vein flow, and tissue Doppler recordings are most frequently used. Although there is still a critical lack of well-designed studies in the field, knowledge has steadily accumulated over the past 20 years, reference ranges of diastolic echocardiographic variables have been determined, epidemiological studies have been conducted, and new treatments of diastolic dysfunction in cats have been evaluated. This report will give the reader a summary of the current status in the field of feline diastology with focus on the noninvasive diagnostic methods and interpretation of echocardiographic surrogate measures of LV diastolic function. Lastly, a grading system using a composite of left atrial size and various DE variables potentially useful in the functional classification of LV diastole in cats is introduced.

Effects of 0.5% Timolol Maleate Ophthalmic Solution on Heart Rate and Selected Echocardiographic Indices in Apparently Healthy Cats

Background

Echocardiographic assessment of diastolic function is challenging in cats, partially because of transmitral flow pattern fusion associated with high heart rates. With heart rate (HR) reduction, transmitral flow waveforms separate, allowing identification of diastolic dysfunction. Timolol, an ophthalmic, nonselective beta‐blocker used in glaucoma is safe and transiently decreases HR in clinical trials.

Hypothesis

Administration of timolol ophthalmic solution decreases HR and facilitates echocardiographic assessment of diastolic function in cats without inducing clinically relevant adverse effects.

Animals

Twenty‐five apparently healthy cats.

Methods

Electrocardiograms and echocardiograms including transmitral flow patterns were evaluated before and 20 minutes after ocular administration of 1 drop of timolol 0.5% solution. Twenty cats underwent treatment with timolol, and 5 different cats served as untreated controls to evaluate the effects of acclimation to the hospital environment on HR.

Results

Acclimation to the hospital had no effect on HR in control cats. After timolol administration, a significant median HR reduction of 25 bpm was observed (P < .0001). Timolol had no effect on E/A ratio in cats without E/A fusion (7/20, P = .44). Of the 13 cats with E and A waves that were fused before timolol application, separation of these waves was identified in 8 cats (62%) after timolol treatment. No bradyarrhythmias were noted after timolol administration, but 2 cats had first‐degree atrioventricular block. Timolol resulted in resolution of dynamic outflow tract obstruction in 6 of 6 cats.

Conclusions and clinical importance

Ocular administration of timolol safely decreases HR in cats and could facilitate assessment of diastolic function.

Echocardiography and conventional Doppler examination in clinically healthy adult Cavalier King Charles Spaniels: effect of body weight, age, and gender, and establishment of reference intervals

OBJECTIVES

The objectives of this study were (1) to assess the potential effect of body weight (BW), age, and gender on the most commonly used echocardiographic and conventional Doppler variables in a large population of healthy Cavalier King Charles Spaniels (CKCS), and (2) to establish the corresponding reference intervals (RI).

ANIMALS

134 healthy adult CKCS.

METHODS

Ultrasound examinations were performed by trained observers in awake dogs. M-mode variables included left ventricular (LV) end-diastolic and end-systolic diameters, LV free wall and interventricular septal thicknesses at end-diastole and end-systole, and LV fractional shortening (FS%). The left atrium (LA) and aortic (Ao) diameters were measured using a 2D method, and the LA/Ao was calculated. Pulsed-wave Doppler variables included peak systolic aortic and pulmonary flow velocities, mitral E and A waves, and E/A ratio. Effects of BW, age, and gender on these 15 variables were tested using a general linear model, and RIs were determined by applying the statistical procedures recommended by the Clinical and Laboratory Standards Institute.

RESULTS

A significant BW effect was observed for all variables, except LA/Ao, FS%, and mitral E/A ratio. A significant but negligible effect of gender and age was also observed for 5/15 and 4/15 of the tested variables, respectively. Only the BW effect on M-mode variables was considered as clinically relevant and the corresponding regression-based RIs were calculated.

CONCLUSIONS

Body weight should be taken into account when interpreting echocardiographic values in CKCS, except for LA/Ao, FS%, and mitral E/A ratio.

Effect of age on myocardial function assessed by two-dimensional speckle-tracking echocardiography in healthy beagle dogs

OBJECTIVES

The objective of this study was to evaluate the effect of age on myocardial function assessed by two-dimensional speckle-tracking echocardiography (2D-STE) in healthy dogs.

ANIMALS

Thirty-two healthy Beagles were used.

METHODS

Myocardial function was assessed in each dog by using 2D-STE, and the results were compared between young and old dogs.

RESULTS

The myocardial deformations in systole, besides the apical rotation rate, were not significantly different between young and old dogs. In contrast, the early diastolic circumferential strain rate, basal rotation rate, and torsion rate were significantly lower in old dogs than in young dogs (P = 0.03, P = 0.033, and P = 0.015, respectively). Late diastolic longitudinal and radial strain rates were significantly higher in old dogs than in young dogs (P = 0.002 and P = 0.018, respectively).

CONCLUSIONS

Young and old dogs showed similar systolic myocardial deformations, but significant differences in the values of some diastolic deformation variables were found between young and old dogs, highlighting the need for using age-matched control subjects in studies of diastolic function.

Effects of vagal maneuvers on heart rate and Doppler variables of left ventricular filling in healthy cats

BACKGROUND

Evaluation of left ventricular (LV) diastole is clinically important in cats with heart disease. Diastolic dysfunction is a main characteristic of feline cardiomyopathy and is associated with clinical signs and poor outcome. Numerous echocardiographic indices characterizing LV diastole exist, of which Doppler variables of transmitral flow and mitral annular motion are used most often. However, rapid heart rate (HR), a common finding in cats examined in the veterinary hospital environment, may cause summation of flow waves limiting interpretation of diastolic function.

OBJECTIVE

To evaluate the effects of vagal maneuvers (gentle eyeball pressure and nasal planum massage) on HR and Doppler variables of LV diastolic filling.

ANIMALS

Twenty-four healthy client-owned cats with summated transmitral flow waves at baseline.

METHODS

Prospective observational study. Transthoracic echocardiography was performed and Doppler transmitral and mitral annular tissue Doppler velocities recorded both before and during vagal maneuvers. Data were compared using a paired t-test.

RESULTS

Application of vagal maneuvers temporarily decreased HR in all cats (mean reduction ± SD; 42 ± 22 bpm). The duration of HR reduction (<5 s, 5-10 s, and >10-15 s) was evenly distributed among groups (8 cats in each). Summated Doppler transmitral flow and mitral annular tissue velocity waves were separated during vagal maneuvers in 71% and 72% of cats, respectively. No adverse effects were observed.

CONCLUSIONS

Vagal maneuvers may be utilized as a simple non-pharmacologic tool in the Doppler evaluation of LV diastolic function in healthy cats.

Echocardiographic assessment of canine degenerative mitral valve disease

Degenerative mitral valve disease (MVD), the most common acquired heart disease in small-sized dogs, is characterized by valvular degeneration resulting in systolic mitral valve regurgitation (MR). Worsening of MR leads to several combined complications including cardiac remodeling, increased left ventricular filling pressure, pulmonary arterial hypertension, and myocardial dysfunction. Conventional two-dimensional, M-mode, and Doppler examination plays a critical role in the initial and longitudinal assessment of dogs affected by MVD, providing information on mitral valve anatomy, MR severity, left ventricular (LV) size and function, as well as cardiac and vascular pressures. Several standard echocardiographic variables have been shown to be related to clinical outcome. Some of these markers (e.g., left atrium to aorta ratio, regurgitation fraction, pulmonary arterial pressure) may also help in identifying asymptomatic MVD dogs at higher risk of early decompensation, which remains a major issue in practice. However, both afterload and preload are altered during the disease course. This represents a limitation of conventional techniques to accurately assess myocardial function, as most corresponding variables are load-dependent. Recent ultrasound techniques including tissue Doppler imaging, strain and strain rate imaging, and speckle tracking echocardiography, provide new parameters to assess regional and global myocardial performance (e.g., myocardial velocities and gradients, deformation and rate of deformation, and mechanical synchrony). As illustration, the authors present new data obtained from a population of 91 dogs (74 MVD dogs, 17 age-matched controls) using strain imaging, and showing a significant longitudinal systolic alteration at the latest MVD heart failure stage.

Echocardiographic values in clinically healthy adult dogue de Bordeaux dogs

OBJECTIVES

To assess the influence of body surface area, age and gender on echocardiographic parameters and to establish echocardiographic reference values for dogue de Bordeaux dogs.

METHODS

Thirty-nine healthy dogue de Bordeaux dogs of both sexes, older than one year, were recruited and 31 of these were included in the study. The classic linear regression model proved to be the best way to analyse the data. The reference limits of the echocardiographic measurements were calculated using the regression equations. The difference between the mean values of body surface area in both gender groups was evaluated by using one-way ANOVA.

RESULTS

A significant correlation was seen between several echocardiographic parameters and body surface area or body surface area and age, and high coefficients of determination (R2) were found. No effect of gender was detected on echocardiographic variables, except for the thickness of the left ventricular posterior wall at end diastole.

CLINICAL SIGNIFICANCE

The echocardiographic parameters related to body surface area, in the absence of correlation with other independent variables (gender and age) should be interpreted with caution because their variation could be significant for the presence of heart disease. The proposed statistical model allows estimation of echocardiographic parameters in dogue de Bordeaux dogs with different body surface areas and ages.

Echocardiographic estimation of left atrial pressure in beagle dogs with experimentally-induced mitral valve regurgitation

Non-invasive and immediate estimation of left atrial pressure (LAP) is very useful for the management of mitral regurgitation (MR), and many reports have assessed echocardiographic estimations of LAP to date. However, it has been unclear of which examination and evaluate article possess the best accuracy for the MR severity. The present research aims to establish the echocardiographic estimation equation of LAP that is well applicable for clinical MR dogs. After the chordae tendineae rupture was experimentally induced via left atriotomy in six healthy beagle dogs (three males and three females, two years old, weighing between 9.8 to 12.8 kg), a radio telemetry transmitter catheter was inserted, which allows the continuous recordings of LAP without the use of sedation. Approximately 5 weeks after the surgery, echocardiographic examination, indirect blood pressure measurement, measurement of plasma atrial natriuretic peptide (ANP) and LAP measurement by way of the radio telemetry system was performed simultaneously. Subsequently, simple linear regression equations between LAP and each variable were obtained, and the equations were evaluated whether to be applicable for clinical MR dogs. As a result, the ratio of early diastolic mitral flow to early diastolic lateral mitral annulus velocity (E/Ea) had the strongest correlation as maximum LAP=7.03*(E/Ea)-54.86 (r=0.74), and as mean LAP=4.94*(E/Ea)-40.37 (r=0.70) among the all variables. Therefore, these two equations associated with E/Ea should bring more precise and instant estimations of maximum and mean LAP in clinical MR dogs.

Detection of congestive heart failure in dogs by Doppler echocardiography

BACKGROUND

Echocardiographic prediction of congestive heart failure (CHF) in dogs has not been prospectively evaluated.

HYPOTHESIS

CHF can be predicted by Doppler echocardiographic (DE) variables of left ventricular (LV) filling in dogs with degenerative mitral valve disease (MVD) and dilated cardiomyopathy (DCM).

ANIMALS

Sixty-three client-owned dogs.

METHODS

Prospective clinical cohort study. Physical examination, thoracic radiography, analysis of natriuretic peptides, and transthoracic echocardiography were performed. Diagnosis of CHF was based upon clinical and radiographic findings. Presence or absence of CHF was predicted using receiver-operating characteristic (ROC) curve, multivariate logistic and stepwise regression, and best subsets analyses.

RESULTS

Presence of CHF secondary to MVD or DCM could best be predicted by E:isovolumic relaxation time (IVRT) (area under the ROC curve [AUC]=0.97, P<.001), respiration rate (AUC=0.94, P<.001), Diastolic Functional Class (AUC=0.93, P<.001), and a combination of Diastolic Functional Class, IVRT, and respiration rate (R2=0.80, P<.001) or Diastolic Functional Class (AUC=1.00, P<.001), respiration rate (AUC=1.00, P<.001), and E:IVRT (AUC=0.99, P<.001), and a combination of Diastolic Functional Class and E:IVRT (R2=0.94, P<.001), respectively, whereas other variables including N-terminal pro-brain natriuretic peptide, E:Ea, and E:Vp were less useful.

CONCLUSION AND CLINICAL IMPORTANCE

Various DE variables can be used to predict CHF in dogs with MVD and DCM. Determination of the clinical benefit of such variables in initiating, modulating, and assessing success of treatments for CHF needs further study.

Evaluation of left ventricular diastolic echocardiographic parameters in healthy dogs by pulsed-wave Doppler

Left ventricular diastolic dysfunction plays an important role on heart failure progression. In order to obtain additional reference values of left ventricular diastolic parameters and investigate influence of common variables, peak E wave (peak E), peak A wave (peak A), E/A ratio (E/A), E wave deceleration time (EDT) and isovolumic relaxation time (IRVT) were studied in 40 clinically healthy dogs, by pulsed wave Doppler. The following values were obtained: peak E = 0.747 ± 0.117 m/s, peak A = 0.487 ± 0.062 m/s, E/A = 1.533 ± 0.198, EDT = 88.7 ± 9.2 ms and IRVT = 0.080 ± 0.009 s. Some parameters were influenced by heart rate (peak E, peak A and IRVT), by age (peak A and E/A) and by body weight (TRIV). Gender influence was absent. Values obtained can be used as reference for canine specimens but its interpretation should consider on the influence of related variables.

Canine dynamic left ventricular outflow tract obstruction: assessment of myocardial function and clinical outcome

OBJECTIVE

The aims of this study were (i) to evaluate echocardiographic findings and myocardial function including pulsed wave tissue Doppler imaging in dogs with naturally occurring dynamic left ventricular outflow tract obstruction and (ii) to investigate the clinical outcome and response to therapy in these dogs.

METHODS

Two cases were retrospectively reviewed and three cases were prospectively evaluated including clinical findings, diagnostic test results (including standard Doppler echocardiography and pulsed wave tissue Doppler imaging), response to treatment and outcome. The two retrospective cases received no treatment. Other cases were treated with a beta-blocker.

RESULTS

All dogs had a variable intensity left apical systolic murmur. Concentric left ventricular hypertrophy, systolic anterior motion of the mitral valve and scimitar-shaped left ventricular outflow tract Doppler flow profile were present in all cases. Pulsed wave tissue Doppler imaging interrogation of the interventricular septum revealed E'/A' reversal in all but one patient. Regression of left ventricular hypertrophy and total resolution of the dynamic left ventricular outflow tract obstruction were observed in all cases.

CLINICAL SIGNIFICANCE

Young dogs are affected with a possible terrier breed predisposition. Dynamic left ventricular outflow tract obstruction may be distinguished from canine hypertrophic cardiomyopathy as progressive resolution of echocardiographic abnormalities was documented. Pulsed wave tissue Doppler imaging abnormalities provide further evidence for significant diastolic dysfunction associated with the hypertrophy.

Cardiovascular dysfunction in dogs associated with critical illnesses

The records of 16 dogs with left ventricular dysfunction associated with severe systemic illness were reviewed. The most common diagnoses in affected dogs were sepsis and cancer. Despite left ventricular dysfunction, no dog presented with signs of congestive heart failure. Fifteen dogs were presented with generalized weakness as a part of their clinical complaint. Twelve (75%) of 16 dogs died or were euthanized within 15 days of admission to the hospital. The average time until death was 3.6 days.

Relationships between velocities of pulmonary venous flow and plasma concentrations of atrial natriuretic peptide in healthy dogs

OBJECTIVE

To investigate the relationship between velocities of pulmonary venous flow (PVF) and plasma concentrations of atrial natriuretic peptide (ANP) in healthy dogs.

ANIMALS

7 healthy Beagles.

PROCEDURES

Dogs were anesthetized, intubated, and positioned in left lateral recumbency. Lactated Ringer's solution was infused (200 mL/kg/h) for 60 minutes via a cephalic vein. Transmitral flow and PVF velocities were measured echocardiographically by use of the apical 4-chamber view. Pulmonary capillary wedge pressure (PCWP) and ANP concentrations were determined.

RESULTS

IV infusion significantly increased heart rate and PCWP. Similarly, the ANP concentration significantly increased from baseline (before infusion of lactated Ringer's solution) values. Transmitral flow velocities were significantly increased, although the ratio of velocity of the flow during early ventricular diastole (E wave) to velocity of the atrial flow (A wave; E:A ratio) was unchanged. Regarding the PVF velocities, forward flow during ventricular systole (S wave) and retrograde flow during atrial contraction were significantly increased, whereas velocity of the forward flow during ventricular diastole (D wave) was unchanged. Ratio of the velocity of the S wave to velocity of the D wave was increased significantly, and this ratio was significantly correlated with PCWP or ANP concentration. However, the E:A ratio was not correlated with PCWP or ANP concentration.

CONCLUSIONS AND CLINICAL RELEVANCE

PVF velocities were strongly correlated with PCWP and plasma ANP concentration in clinically normal dogs. Therefore, PVF velocities may serve as a sensitive indicator and provide additional information for monitoring acute preloading conditions and estimating atrial filling abnormalities in dogs.

Assessing diastolic function with Doppler echocardiography using a novel index: ratio of the transmitral early diastolic velocity to pulmonary diastolic velocity

We developed a novel index to assess left ventricular (LV) relaxation as the ratio of transmitral early diastolic velocity to pulmonary diastolic velocity (E/D ratio). Mixed breed dogs (n=7) were anesthetized and their respiration was controlled. A 3.5-Fr micromanometer-tipped catheter was placed into the left ventricle. Dobutamine (5.0 or 10 microg/kg/min) or esmolol (100 or 500 microg/kg/min) was administered via the cephalic vein. The transmitral flow (TMF) and pulmonary venous flow (PVF) were recorded using transthoracic echocardiography from the apical long-axis view. The heart rate, systolic LV pressure, +dP/dt, and -dP/dt were significantly elevated by dobutamine, but significantly reduced by esmolol. Dobutamine significantly decreased tau, whereas esmolol significantly increased tau. The TMF-derived E and PVF-derived D wave velocities increased significantly with dobutamine, but decreased significantly with esmolol. A significant correlation was detected between the E and D wave velocities (r=0.92). Consequently, the E/D ratio was decreased significantly with dobutamine, and increased significantly with esmolol. Furthermore, the E/D ratio was significantly correlated with -dP/dt (r= -0.64) and tau (r=0.84). Our results suggest that the E/D ratio reflects LV relaxation, and may potentially provide further information on LV relaxation.

Comparison of the myocardial performance index derived by use of pulsed Doppler echocardiography and tissue Doppler imaging in dogs with volume overload

OBJECTIVE

To investigate the relationship between the myocardial performance index (MPI) determined by use of pulsed Doppler (PD) echocardiography and tissue Doppler imaging (TDI) in the response to volume overload-related changes in left ventricle (LV) performance.

ANIMALS

7 male Beagles.

PROCEDURES

Dogs were anesthetized and intubated. A 6-F fluid-filled catheter was placed in the LV to measure LV peak systolic (LVPs) and LV end-diastolic (LVED) pressures. Preload was increased by IV infusion of lactated Ringer's solution (rate of 200 mL/kg/h for 60 minutes) into a cephalic vein. Transmitral flow velocities and aortic outflow were measured, and TDI velocities were obtained from the 4-chamber view.

RESULTS

Acute volume overload induced a significant increase in heart rate, LVPs pressure, and LVED pressure, compared with baseline values. A significant decrease in the PD-MPI and TDI-MPI values and a significant correlation (r = 0.70) between PD-MPI and TDI-MPI were detected. The PD-derived A-wave velocity, ejection time, and isovolumic relaxation time (IRT) and the TDI-derived IRT, MPI, and ratio of the velocity of the E wave to the velocity of the ventricular portion of the E wave during early diastole had equal ability to predict LVED pressure (r(2) = 0.63).

CONCLUSIONS AND CLINICAL RELEVANCE

The TDI-MPI was closely correlated with LV filling pressure and may be helpful in evaluating global cardiac function in dogs.

What parameters affect left ventricular diastolic flow propagation velocity? In vitro studies using color M-mode Doppler echocardiography

BACKGROUND

Insufficient data describe the relationship of hemodynamic parameters to left ventricular (LV) diastolic flow propagation velocity (Vp) measured using color M-mode Doppler echocardiography.

METHODS

An in vitro LV model used to simulate LV diastolic inflow with Vp measured under conditions of varying: 1) Stroke volume, 2) heart rate (HR), 3) LV volume, 4) LV compliance, and 5) transmitral flow (TMF) waveforms (Type 1: constant low diastasis flow and Type 2: no diastasis flow).

RESULTS

Univariate analysis revealed excellent correlations of Vp with stroke volume (r = 0.98), LV compliance (r = 0.94), and HR with Type 1 TMF (r = 0.97). However, with Type 2 TMF, HR was not associated with Vp. LV volume was not related to Vp under low compliance, but inversely related to Vp under high compliance conditions (r = -0.56).

CONCLUSION

These in vitro findings may help elucidate the relationship of hemodynamic parameters to early diastolic LV filling.