In a patient with wide-complex tachycardia, the presence of all of the following in the ECG indicates ventricular tachycardia except-
Correct Answer: Typical right bundle branch block
Description: Absence of a "RS complex," Concordance of QRS simply means "all up" or "all down. right bundle branch block (RBBB) is a hea block in the right bundle branch of the electrical conduction system During a right bundle branch block, the right ventricle is not directly activated by impulses travelling through the right bundle branch. The left ventricle however, is still normally activated by the left bundle branch. These impulses are then able to travel through the myocardium of the left ventricle to the right ventricle and depolarize the right ventricle this way. As conduction through the myocardium is slower than conduction through the Bundle of His-Purkinje fibres, the QRS complex is seen to be widened. The QRS complex often shows an extra deflection that reflects the rapid depolarisation of the left ventricle followed by the slower depolarisation of the right ventricle. The criteria to diagnose a right bundle branch block on the electrocardiogram: The hea rhythm must originate above the ventricles (i.e., sinoatrial node, atria or atrioventricular node) to activate the conduction system at the correct point. The QRS duration must be more than 100 ms (incomplete block) or more than 120 ms (complete block). There should be a terminal R wave in lead V1 (often called "R prime," and denoted by R, rR', rsR', rSR', or qR). There must be a prolonged S wave in leads I and V6 (sometimes referred to as a "slurred" S wave). The T wave should be deflected opposite the terminal deflection of the QRS complex. This is known as appropriate T wave discordance with bundle branch block. A concordant T wave may suggest ischemia or myocardial infarction Ref Harrison 20th edition pg 1456
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