It is now very clear that apparently healthy racehorses can have cardiac rhythm disturbances during exercise. Equally, arrhythmias can be a cause of poor performance. The challenge for the clinician is determining whether or not a rhythm disturbance is clinically relevant. Post-exercise cardiac rhythm is readily evaluated with smartphone ECG devices and there are a range of options available for recording the ECG during exercise. Ideally, for diagnostic purposes, exercise ECG should be performed at, or above the workload the horse is expected to perform. If there is a high index of suspicion, then multiple tests may be required. Rhythm disturbances which are likely to be clinically relevant include atrial fibrillation, ventricular bigeminy/trigeminy, polymorphic rhythms, R-on-T and where there are runs. Transient episodes of ventricular rhythms immediately after peak exercise are of uncertain significance, and the clinician should bear in mind that concurrent problems such as dynamic airway obstructions could be contributing to arrhythmiogenesis. Irregular rhythms which are present at both exercise and rest are more likely to relate to structural myocardial pathology than those that are present at exercise alone.
Fetal heart rate (HR) and rhythm can be determined using M mode echocardiography or via ECG monitoring. For the latter, electrodes are placed dorsal and ventral to the fetus and simultaneously cranial and caudal to the mare's heart. Using appropriate software, the fetal signal can be subtracted from the combined mare and fetus trace to generate a fetal ECG. Technical challenges include maintaining electrodes in position, reduced quality in response to fetal movement, and limited ability to separate maternal and fetal traces if HR are similar. The fetal HR should decline from around 120bpm at 7 months, towards around 80 bpm at term. The fetal HR should increase in response to movement. In response to fetal hypoxia, there is a reduction in HR and lack of episodic HR increases. With progressive compromise, there may be persistent tachycardia and finally bradycardia and cardiac arrest. Single spot measurements are not as useful as measuring HR progressively over time. Although the technique has much promise, there is a need to accumulate clinical data to understand fetal HR responses better and to determine how best to intervene when fetal compromise is identified.
This presentation will outline the current challenges with equine parasite control and discuss approaches for parasite control. Global levels of anthelmintic resistance are ever-increasing in strongylid and ascarid parasites, and the pharmaceutical industry has not developed and introduced any new anthelmintic classes since ivermectin 40 years ago. Combination deworming is not a solution for already developed resistance despite often made claims. All active ingredients are losing anthelmintic spectrum and the good old all-round dewormer no longer exists. The consequence of this is an increasing need for diagnostic surveillance and more emphasis on developing better and more refined diagnostic tools.