Optimal rate control in dogs with atrial fibrillation-ORCA study-Multicenter prospective observational study: Prognostic impact and predictors of rate control

Efficacy and safety of different antiarrhythmic protocols used for rate control in dogs with secondary atrial fibrillation

INTRODUCTION/OBJECTIVES

Studies comparing the effects of antiarrhythmic protocols used for rate control in dogs with secondary atrial fibrillation (AF) are currently limited; therefore, this study aimed to report detailed data on the efficacy and therapy-related side-effects (TRSEs) of different antiarrhythmic protocols in dogs with secondary AF.

ANIMALS, MATERIALS, AND METHODS

Dogs with secondary AF treated with combination therapy with diltiazem and digoxin (CTDilt+Digox), diltiazem monotherapy (MTDilt), digoxin monotherapy (MTDigox), or amiodarone monotherapy (MTAmiod) were retrospectively evaluated. Signalment, clinical, diagnostic, therapeutic, and outcome data were retrieved. Electrocardiographically, antiarrhythmic efficacy was defined by a reduction in the mean heart rate on Holter monitoring ≤125 beats/minutes. Statistical analysis was performed to compare selected data, including the rate of efficacy and TRSEs as well as the median survival time, between dogs treated with different antiarrhythmic protocols.

RESULTS

Fifty-four dogs were included, with 28 receiving the CTDilt+Digox and 26 receiving monotherapies (MTDigox = 16; MTDilt = 5; MTAmiod = 5). The efficacy rate documented in dogs treated with CTDilt+Digox was significantly higher than that observed in dogs from the composite monotherapy group (i.e., MTDilt+MTDigox+MTAmiod) (P=0.048). The rate of TRSEs documented in dogs treated with CTDilt+Digox was similar to that observed in dogs from the composed monotherapy group (P=0.129). The median survival time documented in dogs treated with CTDilt+Digox was significantly longer than that observed in dogs of the MTDigox group (P=0.01).

DISCUSSION

In dogs with secondary AF we included, CTDilt+Digox was well tolerated and provided clinically relevant benefits compared to the use of a single antiarrhythmic drug.

LIMITATIONS

Retrospective design; heterogeneous sample size of categories analyzed; clinicopathological data available for many, but not all, dogs.

CONCLUSIONS

Our findings support the indication to generally consider CTDilt+Digox as a first-line antiarrhythmic treatment in dogs with secondary AF.

Assessment of heart rate measurements obtained from a smart collar compared to 24-h Holter monitoring in healthy dogs

INTRODUCTION/OBJECTIVES

The primary objective was to compare the 24-h mean heart rate (HR) provided by a smart collar with 24-h ambulatory electrocardiography (Holter) in healthy dogs. The secondary objective was to compare the 2-min HR values between the two methods during periods of activity and rest.

ANIMALS, MATERIALS, AND METHODS

Twelve healthy dogs were fitted with both Holter monitors and smart collars. Passing-Bablok regression and Bland-Altman (BA) agreement analysis were used to compare the 24-h mean HR between two methods. The BA analysis for repeated measures and bias plots were used to compare 2-min HR between methods.

RESULTS

The regression analysis showed no significant differential or proportional bias between the methods to estimate 24-h mean HR. The BA analysis showed a mean bias of 2.2 beats per minute (bpm) (95% confidence interval = -0.2, 4.8) with an upper limit of agreement (LOA) of 9.6 bpm (5.1, 14.1) and a lower LOA of -5.1 bpm (-9.5 to -0.6). However, BA analysis of 2-min HR showed poor agreement between methods with wide LOAs at rest and during activity. The smart collar did not provide any HR information for 43% of the total possible recording duration (range = 24%-79%).

STUDY LIMITATIONS AND CONCLUSIONS

The smart collar can provide a potentially clinically useful estimate of 24-h HR in dogs with normal sinus rhythm. The collar did not provide reliable 2-min HR measurements due to inaccuracies in HR estimation during periods of activity and the inability to report any HR during large periods of the recording.

Management of two dogs with post-operative new-onset persistent atrial fibrillation following mitral valve repair

Post-operative new-onset atrial fibrillation (POAF) is a possible complication following cardiac surgery. Digoxin is a drug with positive inotropic and negative chronotropic effects and is listed among antiarrhythmic drugs that can be prescribed in dogs with atrial fibrillation. This report aims at describing the use of digoxin in two dogs with persistent POAF after mitral valve repair. Case 1 was a Toy Poodle, neutered male, 12 years old, weighing 5.0 kg. The patient was diagnosed with the American College of Veterinary Internal Medicine (ACVIM) Stage D myxomatous mitral valve disease without arrhythmia. The day of the surgery was defined as Day 1. Persistent POAF was diagnosed on Day 30 (1-min mean heart rate of 206 bpm by in-clinic electrocardiogram), and treatment with digoxin was started at a dose of 0.0040 mg/kg, p12h. The resolution of atrial fibrillation (AF) was confirmed at the follow-up visit on Day 58 (1-min mean heart rate of 162 bpm by in-clinic electrocardiogram). Case 2 was a mixed-breed dog, neutered male, 12 years old, weighing 7.6 kg. The patient was diagnosed with ACVIM Stage B2 myxomatous mitral valve disease without arrhythmia. After surgery, the patient had a normal sinus rhythm, but a paroxysmal ectopic atrial rhythm was observed on Day 32. Persistent POAF was diagnosed on Day 130 (1-min mean heart rate of 216 bpm by in-clinic electrocardiogram), and treatment with digoxin was started at a dose of 0.0037 mg/kg, p12h. The resolution of AF was confirmed on Day 151 (1-min mean heart rate of 107 bpm by in-clinic electrocardiogram). In this report, the authors suspected that digoxin therapy could have contributed, among other factors, to cardioversion. However, specifically designed studies are needed to confirm this preliminary hypothesis.

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.

Risk Factors for Atrial Fibrillation in the Dog: A Systematic Review

Different risk factors for atrial fibrillation (AF) development have been identified in numerous studies on humans, but this information is less clearly available on the dog. The aim of this systematic review is to determine the risk factors for AF in the dog. Following the PRISMA 2020 guidelines, we conducted a comprehensive search using the Web of Science and Scopus databases for articles reporting on cases of spontaneously occurring AF in dogs. The level of evidence was assessed using the Evidence Quality Grading System of the National Institute of Health. One thousand forty-three studies were initially identified, and twenty of them were included in this systematic review involving 2,359,275 dogs, of which 4807 showed spontaneously occurring AF. Genetics, for the Irish Wolfhound, increased body weight, and left atrial enlargement were the main risk factors for the development of AF in dogs with different cardiac diseases, particularly myxomatous mitral valve disease (MMVD) and dilated cardiomyopathy (DCM). However, some differences were found between these two cardiac diseases regarding additional risk factors. In particular, the presence of congestive heart failure and echocardiographic evidence of increased left atrial pressure or the presence of right atrial enlargement emerged as risk factors in dogs with MMVD or DCM, respectively. Furthermore, significant differences in risk factors were observed between dogs and humans. In particular, advanced age and male sex are not reliable indicators of an increased risk of AF in dogs.