Accelerated ventricular rhythm : ( AVR ) * occurs due to enhanced automaticity in ventricular purkinji system . * may occur as a normal variant of cardiac rhythm . * commonly occurs with reperfusion after MI . * also common with digitalis toxicity . * the upper normal limit of purkinji is 50 / min * accelerated rhythm > 50 / min .....if >100 it is tachycardia . * ORS : wide , regular , > 50/min * not preceeded by P waves . * also termed slow ventricular tachycardia . *it is benign arrythmia not affecting blood pressure . * atrial activity in cases of AVR takes many forms : 1- the atrial activity may occurs due to retrograde conduction during or after the antegrade ventricular activation so , the inverted retrograde P waves are hidden by the larger QRS complexes or by the T waves ...... SO , no appearing atrial activity ..... SO , no P waves appear . 2- AVR may be associated with AV dissociation due to either CHB ( non functioning AV node ) or interference ( AV nodal refractoriness ) ...... in these cases , there will be : NORMAL sinus activity BUT with VARIABLE PR intervals . .....SO , there will be normal P waves before the complexes with variable PR intervals . 3- in cases with CHB , the atrial activity may be of fibrillation type ..... so there will be wided regular complexes > 50/mni with fibrillatory waves . this combination ( AF + CHB + AVR ) occurs in cases with atrial fibrillation with digitalis toxicity ......because digitalis has blocking effect on AV node causing its block & has accelerating effect on purkinje system causing its enhanced automaticity . * AVR may start and terminate with one or more of fusion beats ( partly formed by asinus originated impulse & partly by aventricular originated impulse ) .
Posted on: Sat, 26 Jul 2014 23:38:24 +0000
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