7.8.14 Ventricular fibrillation (VF)
Ventricular fibrillation (VF) is usually a terminal event in which there are no organised ventricular depolarisations or contractions. It is associated with increased myocardial irritability, usually caused by severe systemic or cardiac disease. Auscultation reveals no clear heart sounds. There is no palpable pulse. The ECG shows baseline undulations with no QRS complexes, or P or T waves (Figure 7.14).
Intravenous lignocaine and support is needed immediately, but is seldom successful in the horse. Administration of adrenaline is not sufficient to reverse the arrhythmia. Electrical defibrillation is not practicable usually in the adult horse, although it has been used successfully in small ponies. VF is almost invariably fatal despite treatment.