A wide range of conditions may cause ventricular tachycardia and the ECG is as nuanced as are those conditions. Ventricular tachycardias with ECG waveforms reminding of a left bundle branch block (dominant S-wave in V1) originate in the right ventricle. These characteristics can be used separately or in algorithms (Which are easy to use) to determine whether a tachycardia with wide QRS complexes (often called wide complex tachycardia) is a ventricular tachycardia or an SVT. The rapid ventricular rate, which may be accompanied by already impaired ventricular function, does not allow for adequate filling of the ventricles, which results in reduced stroke volume and reduced cardiac output. Occurs due to early or late after-depolarisations. Polymorphic ventricular tachycardia is typically very fast (100–320 beats per minute) and unstable. This algorithm is accurate, reasonably fast, and easy due to the total elimination of complicated traditional morphologic criteria and the simple requirement to evaluate only lead aVR 3. Join our newsletter and get our free ECG Pocket Guide! Refer to Figure 3. The following characteristics aid in the identification of VT. Positive concordance in the precordial leads (dominant R waves in V1-6). In most cases it alternates between two variants of the QRS complex. Sustained ventricular tachycardia has duration >30 seconds. The rhythm strip is recorded after the other 12 leads rather than simultaneously. increased/abnormal automaticity, re-entry or triggered activity. Prompt recognition and initiation of treatment (e.g. If the QRS complex is net negative in V4–V6, ventricular tachycardia is more likely. Europace . These Purkinje fibers appear to be highly arrhythmogenic in the setting of myocardial ischemia, particularly re-ischemia. qR complex suggests ventricular tachycardia. Presence of capture beats or fusion beats. Transcutaneous or transvenous pacing: Pacing at higher frequency than the ventricular tachycardia may terminate it (but there is a risk of degeneration into ventricular fibrillation). Notching on the initial downstroke of a predominantly negative QRS complex. As you can imagine, the rapid and accurate diagnosis of an electrocardiogram with ventricular tachycardia is vital. Beta-blockers may be administered if the ECG does not show long QT interval. Before dwelling into these characteristics and algorithm it should be noted that 90% of all wide complex tachycardias are ventricular tachycardias! Wellens HJ, Bar FW, Lie KI. Death due to pumping failure (i.e cardiogenic shock) is less common. If there are no signs of ventricular tachycardia, antidromic AVRT should be strongly considered. Otherwise, continue to next criteria. In structural heart disease (coronary heart disease, heart failure, cardiomyopathy, valvular disease etc) monomorphic ventricular tachycardia is typically caused by re-entry. Extreme axis deviation (“northwest axis”) — QRS is positive in aVR and negative in I + aVF. The presence of pre-existing poor ventricular function is strongly associated with cardiovascular compromise. Ventricular tachycardia with rate 100 to 120 beats per minute is referred to as slow ventricular tachycardia. Hence, ventricular tachycardia in coronary artery disease is mostly monomorphic. The algorithm follows: Unconscious patients: start cardiopulmonary resuscitation. On the ECG this manifests as P-waves having no relation to QRS complexes (P-P intervals are different from R-R intervals, PR intervals vary and there is no relation between P and QRS). It was believed that the mere presence of physicians and nurses caused harmful stress. This is seen as the occurrence of a normal beat in the midst of the tachycardia. Because the impulses originate in the right ventricle, the QRS complexes have left bundle branch appearance and the electrical axis is around 90°. Supraventricular tachycardias do not display warm-up phenomenon (with the exception of atrial tachycardia). Sotalol (may cause QT prolongation) and amiodarone may also be considered. If the tachyarrhythmia has a left bundle branch block pattern but the electrical axis is more positive than 90° it suggests ventricular tachycardia. Moreover, if the patient has recently had premature ventricular complexes, and the QRS during tachyarrhythmia resembles that of the premature ventricular complexes, then it is likely to be ventricular tachycardia.
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