Here the ectopic pace-maker is located either in atrium, AVjunction or in the ventricle and rapidly discharges impulses
varying from 150 to 250 beats per minuie According to the location of the pace maker the condituon is called paroxysmal
atrial (PAT). AV junctional or venuricular tachycardia In atrial and ventricular type the rate varies from 140 240 per minute
VR ing saw tooth Aurrer waves but in paroxysmal AV junctional tachycardia it is same as paroxysmal atrial tachycardia te. 140-240 per minute lowever in non-paruxysmal AV junctional tachycardia the rate is usually less 60-130 per minute. Multifocal atrial tachycardia is called MAT Mechanism The basic mechanism of this dysrhythmia is re-entry phenomenon. The attack is initated or terminated by a timed atrial or ventricular ectopics. The re-entry circuit involves the SA node, AV node or accessory pathway or bundle of kent (33%). Aetiology Unknown. PAT occurs in young individuals without any obvious organie heart disease. Supraventricular type may be seen in association with atrial septal defect. Ebstein’sanomaly, mitral valve disease, WPW syndrome, Sick sinus syndrome, Floppy mitral valve syndrome and rarely with ischaemic heart disease. Drugs like Digitalis may also cause it as its toxic effect. Ventricular type is usually due to ischaemic heart disease
or Digitalis intoxication and is dangerous. Cardiomyopathy and thyrotoxicosis also cause paroxysmal tachycardia.
Types This is the commonest type and is seen in young adults. This is divided into atrial and junctional (nodal) types depending
on the site of the ectopic focus. Atrial tachycardia may be associated with AV block and is usually seen as a result of
digitalis toxicity (PAT with block) associated with hypokalaemia