Lisse Vera

Heart rate variability parameters in horses distinguish atrial fibrillation from sinus rhythm before and after successful electrical cardioversion

BACKGROUND Atrial fibrillation (AF) is the most common pathological arrhythmia in horses. After successful treatment, recurrence is common. Heart rate monitors are easily applicable in horses and some devices offer basic heart rate variability (HRV) calculations. If HRV can be used to distinguish between AF and sinus rhythm (SR), this could become a monitoring tool for horses at risk for recurrence of AF. OBJECTIVES The purpose of this study was to assess whether in horses AF (before cardioversion) and SR (after cardioversion) can be differentiated based upon HRV parameters. STUDY DESIGN Cohort study with internal controls. METHODS Six HRV parameters were determined in 20 horses, both in AF and in SR, at rest (2- and 5-min and 1- and 4-h recordings) and during exercise (walk and trot, 2-min recordings). Time-domain (standard deviation of the NN intervals, root mean squared successive differences in NN intervals and triangular index), frequency domain (low/high frequency ratio) and nonlinear parameters (standard deviation of the Poincaré plot [SD]1 and SD2) were used. Statistical analysis was done using paired Wilcoxon signed rank tests and receiver operating characteristic curves. RESULTS HRV was higher during AF compared to SR. Results for the detection of AF were good (area under the receiver operating characteristic curve [AUC] 0.8-1) for most HRV parameters. Root mean squared successive differences in NN intervals and SD1 yielded the best results (AUC 0.9-1). Sensitivity and specificity were high for all parameters at all recordings, but highest during exercise. Although AUCs improved with longer recordings, short recordings were also good (AUC 0.8-1) for the detection of AF. In horses with frequent second degree atrioventricular block, HRV at rest is increased and recordings at walk or trot are recommended. MAIN LIMITATIONS Animals served as their own controls and there was no long-term follow-up to identify AF recurrence. CONCLUSIONS AF (before cardioversion) and SR (after cardioversion) could be distinguished with HRV. This technique has promise as a monitoring tool in horses at risk for AF development.

Pharmacokinetics and electrophysiological effects of sotalol hydrochloride in horses

BACKGROUND Arrhythmias in horses may require long-term anti-arrhythmic therapy. Unfortunately, oral anti-arrhythmic drugs for use in horses are currently scarce. In human patients and small animals, sotalol, a β-blocker with class III anti-arrhythmic properties, is often used for long-term treatment. OBJECTIVES To determine the pharmacokinetics of sotalol at multiple oral dosages in unfasted horses, as well as the effects on electro- and echocardiographic measurements, right atrial and ventricular monophasic action potential (MAP) and effective refractory period (ERP). STUDY DESIGN Placebo controlled, double-blinded experiment. MATERIALS AND METHODS Six healthy, unfasted Warmblood horses were given either 0, 2, 3 or 4 mg/kg bodyweight (bwt) sotalol orally (PO) twice daily (bid) for 9 days in a randomised cross-over design. Echocardiography and surface electrocardiography were performed and plasma concentrations of sotalol and right atrial and right ventricular MAPs and ERPs were determined at steady-state conditions. Statistical analysis was performed using a repeated measures univariate analysis with post hoc Bonferroni corrections. RESULTS Calculated mean steady-state plasma concentrations determined by nonlinear mixed-effect modelling were 287 (range 234-339), 409 (359-458) and 543 (439-646) ng/mL for 2, 3 and 4 mg/kg bwt sotalol PO bid respectively. Sotalol significantly increased the QT interval and ERPs, but, despite increasing plasma concentrations, higher dosages did not result in a progressive increase in QT interval or ERPs. Echocardiographic and other electrocardiographic measurements did not change significantly. MAP durations at 90% repolarisation were not significantly different during sotalol treatment. Besides transient local sweating, no side effects were noted. MAIN LIMITATIONS Study size and ad libitum feeding of hay. CONCLUSIONS Sotalol at a dose of 2, 3 and 4 mg/kg bwt PO bid increases the QT interval and ERP and might be a useful drug for long-term anti-arrhythmic therapy in horses.

A preliminary study of pulmonary vein implant applicability and safety as a potential ablation platform in a follow-up study in pigs

Recurrence of atrial fibrillation after an ablation procedure remains a major problem which emphasizes the need for improved pulmonary vein isolation techniques.

Isolation of pulmonary veins using a thermoreactive implantable device with external energy transfer : evaluation in a porcine model

Pulmonary vein isolation (PVI) is a well‐established method for the treatment of symptomatic paroxysmal atrial fibrillation, but is only partly successful with a high rate of electrical reconnection. We introduce a novel technique in which PVI is accomplished by noninvasive heating of a dedicated thermoresponse implant inserted into the pulmonary veins (PV), demonstrated in a porcine model.

Effect of sotalol on heart rate, QT interval, and atrial fibrillation cycle length in horses with atrial fibrillation

Background Based on its pharmacokinetic profile and electrophysiological effects in healthy horses, sotalol potentially could be used as a long‐term PO antiarrhythmic drug in horses. Objectives To evaluate the effect of sotalol on heart rate (HR), QT interval, atrial fibrillatory rate, and success of cardioversion in horses with naturally occurring chronic atrial fibrillation (AF). Animals Twenty‐eight horses referred for transvenous electrical cardioversion of AF were treated with 2 mg/kg sotalol PO q12h for 3 days before cardioversion, and 13 horses underwent the same protocol without sotalol administration. Methods Retrospective study. Before and after sotalol or no treatment, the HR was measured at rest and during an exercise test. The QT interval and atrial fibrillation cycle length (AFCL) were measured at rest using tissue Doppler velocity imaging. Results In the control group, no significant differences were found between the 2 examinations. In the sotalol group, the HR at rest and during exercise was significantly lower after sotalol treatment, whereas the QT interval and AFCL measured by tissue Doppler increased significantly. Cardioversion to sinus rhythm was achieved in 25/28 horses in the sotalol group and all horses in the control group, but the median number of shocks and energy at cardioversion were significantly lower in the sotalol group. Conclusions and Clinical Importance In horses with AF, sotalol administration results in class III antiarrhythmic effects and β‐blocking activity, with moderate HR reduction during exercise.

Detection of subclinical left ventricular dysfunction by tissue Doppler imaging in horses with aortic regurgitation

BACKGROUND Aortic regurgitation (AR) can have an important clinical impact and in some cases leads to left ventricular (LV) failure. Tissue Doppler imaging (TDI) is an echocardiographic technique that has been used in horses to detect LV dysfunction. OBJECTIVES To examine whether TDI detects changes in radial myocardial wall motion in horses with AR compared with control horses. STUDY DESIGN Case-control study. METHODS Echocardiography was performed in 30 healthy Warmblood horses and 34 Warmblood horses with AR, subdivided in groups with mild, moderate or severe AR. TDI measurements were performed on six segments of the short-axis images of the LV myocardial wall. Myocardial wall motion was evaluated by measuring velocity and deformation during isovolumetric contraction, systole, early and late diastole. Timing of different events was also measured. RESULTS In most segments, a significantly higher systolic myocardial velocity was found in horses with AR compared with controls. Horses with AR also had higher late diastolic velocity, although the difference was not significant in all segments. TDI measurement of timing intervals demonstrated less difference between groups. MAIN LIMITATIONS There was a significant difference in age between the control group and horses with AR, which may confound the results. The assessment of AR severity was based on subjective criteria as there is no gold standard. CONCLUSIONS TDI showed significant differences in radial systolic and late diastolic myocardial velocity in horses with AR. This could indicate an altered LV function in these horses, but further research is needed to investigate the prognostic value of these measurements.

Can heart rate variability parameters derived by a heart rate monitor differentiate between atrial fibrillation and sinus rhythm

BackgroundHeart rate variability (HRV) parameters, and especially RMSSD (root mean squared successive differences in RR interval), could distinguish atrial fibrillation (AF) from sinus rhythm(SR) in horses, as was demonstrated in a previous study. If heart rate monitors (HRM) automatically calculating RMSSD could also distinguish AF from SR, they would be useful for the monitoring of AF recurrence. The objective of the study was to assess whether RMSSD values obtained from a HRM can differentiate AF from SR in horses. Furthermore, the impact of artifact correction algorithms, integrated in the analyses software for HRV analyses was evaluated. Fourteen horses presented for AF treatment were simultaneously equipped with a HRM and an electrocardiogram (ECG). A two-minute recording at rest, walk and trot, before and after cardioversion, was obtained. RR intervals used were those determined automatically by the HRM and by the equine ECG analysis software, and those obtained after manual correction of QRS detection within the ECG software. RMSSD was calculated by the HRM software and by dedicated HRV software, using six different artifact filters. Statistical analysis was performed using the Wilcoxon signed-rank test and receiver operating curves.ResultsThe HRM, which applies a low level filter, produced high area under the curve (AUC) (> 0.9) and cut off values with high sensitivity and specificity. Similar results were obtained for the ECG, when low level artifact filtering was applied. When no artifact correction was used during trotting, an important decrease in AUC (0.75) occurred.ConclusionIn horses treated for AF, HRMs with automatic RMSSD calculations distinguish between AF and SR. Such devices might be a useful aid to monitor for AF recurrence in horses.

Right ventricular function during pharmacological and exercise stress testing in horses

The disproportionate rise of pulmonary artery pressure compared to systemic blood pressure during exercise can lead to detrimental right ventricular remodelling in endurance athletes. Horses may act as an extreme model of these athletic cardiovascular adaptations, as they show a three fold increase in pulmonary pressures during exercise. Right ventricular function was examined in ten healthy horses using post-exercise and pharmacological stress echocardiography in a randomised cross-over design. Exercise testing was performed on a treadmill while pharmacological testing was performed using an atropine-dobutamine infusion. Heart rate, systemic blood pressure and cardiac output during echocardiography were similar post-exercise compared to maximal pharmacological stress. Systolic pulmonary artery pressure was significantly higher during the exercise test (121±15mmHg) and during immediate post-exercise echocardiography (93±10mmHg) compared to maximal pharmacological stress (69±12mmHg). Right ventricular diameters as well as the ratio of systolic right to left ventricular area were higher post-exercise. Right ventricular fractional area change was significantly decreased post-exercise (40.5±6.2%) compared to a significant increase during pharmacological stress echocardiography (72.6±7.3%). Serum cardiac troponin I concentration was significantly higher 2h after the pharmacological test compared to baseline values and post-exercise, although the highest value was found post-exercise in the horse with the highest systolic pulmonary artery pressure and lowest right ventricular fractional area change. Pharmacological stress testing is not recommended in further studies on right ventricular adaptations in athletic horses, as this does not reproduce the effects of exercise.