www.vets-now.com Aims 1.Brief summary of relevant clinical electrophysiology 2.Indications for taking an electrocardiogram (ECG) 3.How to obtain a diagnostic ECG All Covered in Part 1 4.Basic ECG interpretation
www.vets-now.com Premature QRS complexes – wide or narrow QRS morphology Trace 1 Trace 2 Both of these traces show premature QRS complexes. These are complexes with a shorter R-R interval than the preceding sinus beats
www.vets-now.com Trace 1 Trace 1: The first 4 complexes show sinus rhythm. The 5 th QRS complex is a premature beat with no associated P wave and a wide bizarre QRS morphology which suggests that it is not being conducted through the ventricles via the normal conduction system. As this beat originates in the ventricles it is termed a ventricular premature beat or VPC. The remainder of the trace shows sinus rhythm.
www.vets-now.com Trace 2 Trace 2: Shows premature narrow QRS complex beats (the 2 nd, 5 th, 8 th, 11 th and 14 th beats). These are supraventricular premature beats or SPC.
www.vets-now.com Escape beats Sinus rhythm Sinus arrest with ventricular escape rhythm Escape beats are less common than premature beats Escape beats occur after an interval GREATER than the normal R-R interval (cf premature beats occur after an interval LESS than the normal R-R interval) Escape beats have a wide and bizarre complex morphology as they originate from the ventricles. Escape beats maintain cardiac output during sinus arrest.
www.vets-now.com Potentially life threatening ECGs
www.vets-now.com Potentially life threatening ECGs – ventricular tachycardia Sinus rhythm Ventricular tachycardia Characteristics of VT: Rapid (>180bpm) Generally regular More than 6 consecutive wide, bizarre QRS complexes Seen in animals with severe cardiac and/or systemic disease (eg gastric dilation torsion, pancreatitis, splenic disease, IMHA, etc). Of particular concern in Boxers, Dobermanns and Great Danes
www.vets-now.com Potentially life threatening ECGs – coarse ventricular fibrillation Ventricular fibrillation is characterised by very rapid baseline undulations.
www.vets-now.com Potentially life threatening ECGs – fine ventricular fibrillation Usually a terminal rhythm Rapid baseline undulations of lower amplitude to coarse VT. In this cases progresses to complete asystole and death around 11:27.
www.vets-now.com Potentially life threatening ECGs - asystole Flatline as there is no organised atrial or ventricular activity
www.vets-now.com Potentially life threatening ECGs – high grade second degree atrioventricular block P QRS T P PPPPP P P Large number of consecutive unconducted P waves (blocked at atrioventricular node or AVN). Finally a P wave is conducted through the AVN resulting in a normal QRS complex. There are then 13 consecutive unconducted P waves before the next P-QRS-T complex.
www.vets-now.com Potentially life threatening ECGs – sinus arrest with very slow escape rhythm During this 10 second period only a single beat is seen therefore the heart rate is very slow during this recording. The beat seen has a bizarre QRS morphology and is not preceded by a P wave suggesting that it is ventricular in origin.