A patient develops sudden palpitation with HR 150/min, regular. What could be the cause aEUR'

PSVT [Ref: Harrison 17/e p. 1431, 1427, 1426, 14351 Sinus tachycardia Sinus tachycardia occurs when SA node discharges at a rate faster than 100 beats/minute. Sinus tachycardia represents a normal or appropriate response to a physiological stress such as that occurs with exercise, anxiety or fever. It is impoant to distinguish sinus tachycardia from other SVT's. - Sinus tachycardia will produce a Pwave contour consistent with its origin from the sinus node. - Sinus tachycardia is in absence of complicating conduction disturbance is characterized by normal P-QRS-T complexes which are recorded in rapid succession. Onset of sinus tachycardia is gradual. - Sinus tachycardia is the normal physiological response to exercise and emotions. A sinus tachycardia that persists at rest is usually an expression of some underlying disorder. Atrial flutter In atrial flutter the impulse originates .from a single .focus in the atria. Classical or typical atrial flutter has an atrial rate of about 300 heats/minute. The ventricular response to this rapid atrial activity depends upon the efficacy of A-V conduction. - Occasionally every atrial impulse is conducted to the ventricle i.e., a 1:1 response resulting in very .fast ventricular rate. - More commonly second degree A-V block is present resulting in a relatively slow ventricular rate. The Atrial flutter commonly present in with a ventricular response that tends to be 2:1 or typically 130-150 beats/minute. - This means that every second atrial beat gets through the A-V node. - Because the ration of P to QRS is usually consistent atrial flutter is often regular. So atrial flutter commonly present as fixed 2:1 A-V block with a regular hea rate that is 150-200 b/rm These are spontaneously occurring and sporadic paroxysmal episodes of regular rapid hea rate of 150-250 beats/minute. Theoretically it refers to any tachycardia that is not ventricular in origin. In the widest sense SVT may include abnormal sinus tachycardia, ectopic atrial tachycardia (that is not from sinoatrial node), Atrial .fibrillation1flutter and junctional tachycardial. Often, however, in clinical setting, it is used practically as a synonym for paroxysmal supraventricular tachycardia. Supraventricular tachycardia develops and ends abruptly and during the episode the hea rate is b/w 150-250 and is regular. - Symptoms in PSVT may sta and stop suddenly often in response to quick movement such as picking up something from the floor. Because physiological sinus tachycardia has a gradual onset and atrial fibrillation is irregular they are excluded from the PSVT category. PSVT are most commonly AV nodal reentrant tachycardia or pa of WPW syndrome. Idioventricular rhvthum In idioventricular tachycardia an ectopic, focus in the ventricle is enhanced and it exceeds or equals the sinus rate. The hea rate in idioventricular rhythm is in the rage of 70- 80b/minute. Sinus tachycardia can be ruled out as it has slow onset. In idioventricular tachycardia the hea rate is usually 70-80 beats/minute. So we are left with I'SVT and Atrial flutter with block. - Atrial flutter has an atrial rate of 250-300 beat/minute and the hea rate is irregular but it is usually associated with fixed 2:1 block so the hea rate drops to 150 b/m and the rate becomes regular. - So both PSVT and Atrial flutter can have regular hea rate of 150 b/m. - Both have sudden onset. There is nothing much to differentiate b/w supraventricular tachycardia and Atrial fibrillation. Supraventicrucular tachycardia seems to be the correct option because it is quite rare .for a normal person to develop atrial fibrillation. Atrial fibrillation usually develops in patients with preexisting cardiac disease. The question does not give any information regarding this, so it can be assumed that he is a normal healthy person. Sudden palpitation in a normal healthy person is most likely due to supraventricular tachycardia.