BackgroundAlthough atrial fibrillation (AF) can be successfully treated in horses, recurrence occurs frequently. In humans, atrial function after cardioversion can predict recurrence.ObjectivesTo examine the prognostic value of atrial mechanical function at 24 hours after cardioversion and other potential predictor variables for AF recurrence in horses.Animals117 horses treated for AF at 4 referral centers.MethodsRetrospective study. Inclusion criteria were successful cardioversion, echocardiography at 24 hours after cardioversion and ≥4 months follow‐up. To determine factors associated with AF recurrence, a multivariable survival model was built.Results133 AF episodes in 117 horses were included. AF recurred in 36/100 horses with a first AF episode and in 57/133 AF episodes overall. Factors associated with recurrence in horses with a first episode were previous unsuccessful treatment attempt (hazard ratio HR 2.36, 95% confidence interval CI 1.11–4.99, P = .025) and mild or moderate mitral regurgitation (HR 2.70, 95% CI 1.23–5.91, P = .013). When the last AF episode of all horses was included, previous AF (HR 2.53, 1.33–4.82, P = .005) and active left atrial fractional area change ≤9.6% (HR 3.43, 1.22–9.67, P = .020) were significant predictors.Conclusions and Clinical ImportanceThe only echocardiographic variable of left atrial function with significant prognostic value for recurrence was low active left atrial fractional area change. Further research is necessary to evaluate whether echocardiography at a later timepoint could provide more prognostic information.
Summary 10Reasons for performing the study: Atrial fibrillation (AF) is the most important dysrhythmia 11 affecting performance in horses and has been associated with incoordination, collapse and 12 sudden death. Limited information is available on ventricular response during exercise in 13 horses with lone AF. 14 Objectives: To investigate ventricular response in horses with lone AF during a standardised 15 lungeing exercise test. Results: Individual average heart rate during walk ranged from 42 to 175 bpm, during trot 21 from 89 to 207 bpm, during canter from 141 to 269 bpm, and during gallop from 191 to 311 22 bpm. Individual beat-to-beat maximal heart rate ranged from 248 to 492 bpm. Ventricular 23 premature depolarisations were present in 81% of the horses: at rest (16%), during exercise 24 (69%), and during recovery (2%). In 33% of the horses, broad QRS complexes with R-on-T 25 morphology were found. 26Conclusions: Exercising horses with lone AF frequently develop disproportionate tachycardia. 27In addition, QRS broadening and even R-on-T morphology is frequently found. QRS 28 broadening may originate from ventricular ectopic foci or from aberrant intra-ventricular 29 conduction, for example due to bundle branch block. This might explain the high number of 30 complexes currently classified as ventricular premature depolarisations. 31Potential relevance: Prevalence of QRS broadening and especially R-on-T was very high in 32 horses with AF and was found at low levels of exercise. These dysrhythmias are considered 33 risk factors for the development of ventricular tachycardia and fibrillation and they might 34 explain signs of weakness, collapse or sudden death that have been reported in horses with 35 AF. 36Accepted Article 3
BackgroundAtrial fibrillation (AF) cycle length (CL) and atrial size have been used in humans to characterize electrical and structural remodeling to predict outcome of cardioversion of AF and risk for AF recurrence (rAF).HypothesisAtrial fibrillation cycle length can be determined in horses with AF, and AFCL and atrial size are related to risk for rAF.AnimalsEighteen horses with naturally occurring AF that were successfully converted to sinus rhythm (SR) by transvenous electrical cardioversion (TVEC).MethodsProspective study. Horses with severe valvular regurgitation, left atrial enlargement, or that required sedation for catheter placement were excluded. In all horses intra‐atrial electrograms were recorded and estimated AF duration and echocardiographic parameters were determined before TVEC. The follow‐up time was 1 year after TVEC.ResultsAtrial fibrillation cycle length could be determined in all horses. The AFCL and the shortest 5th percentile (p5) AFCL in horses with rAF (n = 6 or 33%) were (mean ± SD) 157 ± 28 and 134 ± 24 milliseconds, respectively, and in those maintaining SR (n = 12 or 67%) 166 ± 13 and 141 ± 13 milliseconds, respectively. Significant parameters to predict rAF were (1) the ratios of the p5AFCL to the left atrium (LA) sizes corrected to the size of aorta (AO) and (2) LA sizes corrected to the size of AO.Conclusions and Clinical ImportanceBefore TVEC, assessment of LA size and atrial electrophysiologic characteristics might help to identify horses at increased risk for AF recurrence.
Background The ISARIC prospective multinational observational study is the largest cohort of hospitalized patients with COVID-19. We present relationships of age, sex, and nationality to presenting symptoms. Methods International, prospective observational study of 60 109 hospitalized symptomatic patients with laboratory-confirmed COVID-19 recruited from 43 countries between 30 January and 3 August 2020. Logistic regression was performed to evaluate relationships of age and sex to published COVID-19 case definitions and the most commonly reported symptoms. Results ‘Typical’ symptoms of fever (69%), cough (68%) and shortness of breath (66%) were the most commonly reported. 92% of patients experienced at least one of these. Prevalence of typical symptoms was greatest in 30- to 60-year-olds (respectively 80, 79, 69%; at least one 95%). They were reported less frequently in children (≤ 18 years: 69, 48, 23; 85%), older adults (≥ 70 years: 61, 62, 65; 90%), and women (66, 66, 64; 90%; vs. men 71, 70, 67; 93%, each P < 0.001). The most common atypical presentations under 60 years of age were nausea and vomiting and abdominal pain, and over 60 years was confusion. Regression models showed significant differences in symptoms with sex, age and country. Interpretation This international collaboration has allowed us to report reliable symptom data from the largest cohort of patients admitted to hospital with COVID-19. Adults over 60 and children admitted to hospital with COVID-19 are less likely to present with typical symptoms. Nausea and vomiting are common atypical presentations under 30 years. Confusion is a frequent atypical presentation of COVID-19 in adults over 60 years. Women are less likely to experience typical symptoms than men.
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