Tachycardias

This presentation is about narrow complex and wide complex tachycardia.

1. بسم الله الرحمن الرحیم

2. tachycardias Narrow-Complex and Wide-Complex T achycardias

3. Tachycardias are defined as a heart rate > 100 / rninute . Tachycardias that utilize atrial or AV nodal tissue as part of their mechanism (i.e. arising above the Bundle of His) are known as supraventricular tachycardia while those below as ventricular tachycardia. Another way to classify tachycardias is narrow-complex (QRS complex <0.12 seconds) and wide-complex ( QRS >0.12 seconds) tachycardias. In general, tachycardias that originate below the AV node produce wide QRS complexes while those originating from or above AV node produce narrow QRS complexes. Common causes of wide complex tachycardias include: Ventricular tachycardia Pacemaker-mediated tachycardia Some cases of supraventricular tachycardia (see below) Toxicity of certain medications (e.g. tricyclic antidepressants, diphenhydramine, cocaine) Post-resuscitation cardiac rhythm

4. Hyperkaliemia (usually produces wide-complexes with bradycardia) Sometimes , supraventricular and nodal tachycardias may produce widened QRS complexes due to: Ante grade conduction from the atria to the ventricles via an accessory pathway (bundle of Kent and others ) underlying pre-existing bundle branch block Rate-related bundle branch block induced by the tachycardia itself wide complex tachycardia (QRS duration >0.12 seconds), thus, may be either supraventricular or ventricular in origin and differentiation between them is important from the therapeutic point of view. Look for any evidence of hemodynamic instability before attempting to differentiate these two types of tachycardia . In evaluating a patient with a regular wide complex tachycardia the operating assumption must be that the tachycardia is of ventricular origin until proved to be otherwise .

5. •Presence of fusion beats Presence of AV dissociation • Presence of capture beats • QRS width >0.14 seconds if RBBB is present or >0.16 seconds if LBBB is present • QRS axis <-90° to ± 180° • Pre-cordial concordance • RBBB pattern with • Rsr ' or RS pattern in lead V1 • R/S <1 or QS pattern in V 6 • LBBB pattern with • Q in V6 • Notched down stroke S wave in V1 • R >0.03 seconds in V1 ECG criteria that suggest a ventricular tachycardia are:

6. Capture beats are QRS complexes resulting from ventricular activation originating in supranodal tissue, using electrical conduction pathways above the ventricle. These are therefore narrow and are similar to a normal QRS complex .

7. Fusion beats are hybrid QRS complexes and result from simultaneous activation of ventricles via normal conduction through AV node and through ventricular rhythm. They are therefore intermediate in morphology and width from either a capture or ventricular beat Pre-cordial concordance means that QRS direction on the ECG in all the pre-cordial leads is consistent, i.e. all are either positive or negative. Positive pre-cordial concordance, however, may also occur during supraventricular tachycardia with aberrant conduction. Negative pre-cordial concordance nearly always indicates ventricular tachycardia. After termination of tachycardia the ECG should be analyzed during sinus rhythm for any evidence of QT prolongation, Brugada phenotype, ischaemic heart disease, pre-excitation or an underlying cardiomyopathy; all of these features increase the probability of life-threatening arrhythmias.