Advances in echocardiography.

Echocardiography is an exceptionally useful technique for diagnosing cardiovascular disease in small animals. It is noninvasive and provides a wealth of data concerning cardiac morphology and function. For many patients, echocardiography is the definitive diagnostic tool. A well-performed study coalesces the findings of the physical examination, electrocardiogram, and radiographs into a clearly defined diagnosis on which treatment decisions can be based. More so than other diagnostic techniques, echocardiography is highly operator dependent and relies on the proper acquisition and interpretation of results by an examiner who is familiar with the principles, capabilities, and limitations of ultrasound imaging.This article reviews the basics of echocardiography, measurement of cardiac dimensions, and assessment of cardiac function. Within these sections, emerging technologies that expand the capabilities of the echocardiographic examination are introduced.     

Retrospective Evaluation of the Effect of Heart Rate on Survival in Dogs with Atrial Fibrillation

Background

Atrial fibrillation (AF) usually is associated with a rapid ventricular rate. The optimal heart rate (HR) during AF is unknown.

Hypothesis/Objectives

Heart rate affects survival in dogs with chronic AF.

Animals

Forty‐six dogs with AF and 24‐hour ambulatory recordings were evaluated.

Methods

Retrospective study. Holter‐derived HR variables were analyzed as follows: mean HR (meanHR, 24‐hour average), minimum HR (minHR, 1‐minute average), maximum HR (maxHR, 1‐minute average). Survival times were recorded from the time of presumed adequate rate control. The primary endpoint was all‐cause mortality. Cox proportional hazards analysis identified variables independently associated with survival; Kaplan‐Meier survival analysis estimated the median survival time of dogs with meanHR <125 bpm versus ≥125 bpm.

Results

All 46 dogs had structural heart disease; 31 of 46 had congestive heart failure (CHF), 44 of 46 received antiarrhythmic drugs. Of 15 dogs with cardiac death, 14 had CHF. Median time to all‐cause death was 524 days (Interquartile range (IQR), 76–1,037 days). MeanHR was 125 bpm (range, 62–203 bpm), minHR was 82 bpm (range, 37–163 bpm), maxHR was 217 bpm (range, 126–307 bpm). These were significantly correlated with all‐cause and cardiac‐related mortality. For every 10 bpm increase in meanHR, the risk of all‐cause mortality increased by 35% (hazard ratio, 1.35; 95% CI, 1.17–1.55; P < 0.001). Median survival time of dogs with meanHR<125 bpm (n = 23) was significantly longer (1,037 days; range, 524‐open) than meanHR ≥125 bpm (n = 23; 105 days; range, 67–267 days; P = 0.0012). Mean HR was independently associated with all‐cause and cardiovascular mortality (P < 0.003).

Conclusions and Clinical Importance

Holter‐derived meanHR affects survival in dogs with AF. Dogs with meanHR <125 bpm lived longer than those with meanHR ≥ 125 bpm.     

Carvedilol in dogs with dilated cardiomyopathy

BACKGROUND: Dilated cardiomyopathy (DCM) is characterized by reduced systolic function, heightened sympathetic tone, and high morbidity and mortality. Little is known regarding the safety and efficacy of beta-blocker treatment in dogs with DCM. HYPOTHESIS: Carvedilol improves echocardiographic and neurohormonal variables in dogs with DCM over a 4-month treatment period. METHODS: Prospective, placebo-controlled, double-blinded randomized study. Dogs with DCM underwent echocardiography, ECG, thoracic radiographs, and neurohormonal profiling, followed by titration onto carvedilol (0.3 mg/kg q12h) or placebo over a 4-week period and subsequently received 3 months of therapy. Primary study endpoints included left ventricular volume and function. RESULTS: Sixteen dogs received carvedilol and 7 received placebo. At study end, 13 carvedilol dogs and 5 placebo dogs were alive. There was no difference in the mean percentage change in left ventricular volume at end-diastole (LVVd), left ventricular end-systolic volume (LVVs), and ejection fraction (EF) between treatment groups, suggesting that both groups experienced similar amounts of disease progression. Carvedilol treatment did not result in significant changes in neurohormonal activation, radiographic heart size, heart rate, or owner perceived quality-of-life. Baseline B-type natriuretic peptide (BNP) predicted dogs in the carvedilol-treated group that maintained or improved their EF over the study duration. CONCLUSIONS AND CLINICAL IMPORTANCE: Carvedilol administration did not improve echocardiographic or neurohormonal indicators of heart function. The lack of effect may be related to severity of disease, carvedilol dose, or brevity of follow-up time. Statistical power of the present study was adversely affected by a high fatality rate in study dogs and small sample size.     

Study of the Structure–Activity Relationship of an Anti-Dormant Mycobacterial Substance 3-(Phenethylamino)Demethyl(oxy)aaptamine to Create a Probe Molecule for Detecting Its Target Protein

The current tuberculosis treatment regimen is long and complex, and its failure leads to relapse and emergence of drug resistance. One of the major reasons underlying the extended chemotherapeutic regimen is the ability of Mycobacterium tuberculosis to attain a dormant state. Therefore, the identification of new lead compounds with chemical structures different from those of conventional anti-tuberculosis drugs is essential. The compound 3-(phenethylamino)demethyl(oxy)aaptamine (PDOA, 1), isolated from marine sponge of Aaptos sp., is known as an anti-dormant mycobacterial substance, and has been reported to be effective against the drug resistant strains of M. tuberculosis. However, its target protein still remains unclear. This study aims to clarify the structure–activity relationship of 1 using 15 synthetic analogues, in order to prepare a probe molecule for detecting the target protein of 1. We succeeded in creating the compound 15 with a photoaffinity group that retained antimicrobial activity, which proved to be a suitable probe molecule for identifying the target protein of 1.     

Practices and outcome of artificial cardiac pacing in 154 dogs

Artificial pacing (AP) is a treatment for symptomatic bradyarrhythmias unresponsive to medical therapy. This retrospective study was designed to define the practices and outcome of AP in dogs at 7 referral institutions participating in the Companion Animal Pacemaker Registry and Repository (CANPACERS). The indications, implantation techniques, complications, long-term outcome, and owner satisfaction were examined. One hundred fifty-four dogs were identified as undergoing AP from January 1, 1991, to January 1, 1996. Third-degree atrioventricular (AV) block (n = 91; 59%) and sinus node dysfunction (n = 45; 29%) were the most common indications for AP Transvenous endocardial AP systems were implanted in 136 dogs (88%), and epicardial systems were implanted in 18 (12%). Complications associated with AP were reported in 84 dogs (55%). Major complications occurred in 51 dogs (33%), including dislodgement of the pacing lead (n = 15; 10%), generator failure (n = 10; 6%), cardiac arrest during implantation (n = 9; 6%), and infection (n = 7; 5%). Minor complications occurred in 47 dogs (31%), including seroma formation (n = 18; 12%), muscle twitch (n = 17; 11%), and inconsequential arrhythmias (n = 15; 10%). Fourteen dogs (9%) experienced both major and minor complications. Survival analysis revealed 1-, 2-, and 3-year survival rates of 70, 57, and 45%, respectively. Age and presence of preexisting congestive heart failure (CHF) had a negative effect on survival (P = .001). Sixty percent of dogs with preexisting CHF died within 1 year of implantation, whereas 25% of dogs without heart failure died during the same period. Owners rated their satisfaction with the procedure as high in 80% of the dogs.     

Erythrocyte-replaced mouse model for Haemoparasite studies: comparison of NOD/shi-scid and C.B-17/Jcl-scid mouse upon acceptability of human erythrocytes

The erythrocyte-exchanged chimera mouse model has become to be a significant tool for studying animal and human (hu) protozoan haemoparasites, though the usefulness of this model varies depending primarily on the acceptability of xenogeneic red blood cells (RBC). To find a superior recipient in comparison with C.B-17/Jcl mouse with severe combined immuno-deficiency (scid) mutation, we examined in this report the non-obese diabetes (NOD)/shi-scid mouse, a recently available strain of SCID. When 2.5 x 10(8) of fluorescent dye-labeled hu-RBCs were transfused, C.B-17scid mouse eliminated them logarithmically by a simple linear regression, while NOD-scid mouse eradicated hu-RBCs by a unique two-step fashion, i.e., a potent but only briefly functioning RBC eradication followed by a weak steadily functioning step. The means of regression line constance +/- their standard deviations (SD) of 205 C.B-17scid and of 213 NOD-scid mice for their short- and long-lasting steps were -0.73 +/- 0.63, -0.53 +/- 0.25 and -0.16 +/- 0.10, respectively. Hu-RBC half-lives determined from these means of C.B-17scid mice and of NOD-scid mice for the short- and long-living steps were 3.6, 4.9 and 16.3 hr, respectively. Higher hu-RBC acceptability of NOD-scid mouse, especially at their long-lasting step, was also demonstrated under at an activated state of mouse innate immunity. Treatment with 1.0 mg heat-killed Candida cells caused an acceleration of hu-RBC elimination in both mouse strains but the magnitudes for the short- and long-living steps of NOD-scid mice evaluated by "stimulation index" were only 1/2.6 and 1/7.6 of C.B-17scid mice, respectively.     

Identification of Petunia hybrida cultivars that diurnally emit floral fragrances

In order to identify genetic resources for breeding fragrant petunias for use as bedding plants, volatile compounds released by day from the flowers of 40 commercial Petunia hybrida cultivars were analyzed using a solid-phase micro-extraction technique coupled with GC–MS. The three cultivars with solid deep-blue flowers that accumulate malvidin in corollas with high tissue pH were found to emit abundant iso-eugenol as the principal floral fragrance. Several other cultivars that emitted considerable amounts of methylbenzoate and/or benzylbenzoate from the flower were also identified. Association between the floral fragrance and the other floral traits such as floral anthocyanin composition and corolla-tissue pH was discussed.