Paroxysmal tachycardia is a form of tachycardia which begins and ends in an acute (or paroxysmal) manner.Here the ectopic pace-maker is located either in atrium, Avn junction or in the ventricle and rapidly discharges impulses varying from 150 to 250 beats per minute. According to the location of the pace-maker the condition is called paroxysmal atrial (PAT), AV junctional or ventricular tachycardia. In atrial and ventricular type the rate varies from 140-240 per minute; but in paroxysmal AV junctional tachycardia it is same as paroxysmal atrial tachycardia i.e. 140-240 per minute. However in non-paroxysmal AV junctional tachycardia the rate is usually less 60-130 per minute. Multifocal atrial tachycardia is called MAT.
The cause of this condition is not accurately known, though it is probably of nervous origin and can be aggravated by physical wear and tear. The symptoms are sometimes very alarming but it is not considered in itself dangerous.PAT occurs in young individuals without any obvious organic heart disease. Supraventricular type may be seen in association with atrial septal defect, Ebstein’s anomaly, 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
ECG is helpful for final diagnosis. In atrial tachycardia the QRS complexes are normal but ‘P’ waves will have abnormal morphology. In paroxysmal AV junctional tachycardia the QRS complexes are normal but retrograde ‘P’ waves may be present which are not always visualized. His bundle electrogram or High right atrial electrocardiogram may be helpful. In ventricular type QRS is wide, bizarre and P waves are not clearly seen. A monophasic QS or R wave pattern in precordial leads with no transitional point and sometimes fusion beats or atrial capture beats may be seen. Torsade de pointes is a special form of VT where QRS morphology varies with typical twisting of the points, RR interval is irregular, ventricular rate may be 200-300 beats per minute. Sometimes the rate may be 400 beats per minute. The amplitude of the complexes vary and may be alternately above and below the baseline. This usually occurs in presence of a prolonged QT interval. It may occur spontaneously or after use of drugs which prolong QT duration e.g., Quinidine or in hypokalaemia, hypomagnesemia.PAROXYSMAL TACHYCARDIA.
1.Onset is sudden 2.Severe palpitation. 3.Fluttering sensation in the chest. 4.Sometimes dizziness or syncope. 5. Precordial pain. 6.Breathlessness
It can be divided by the origin:
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