Definition of Tachyarrhythmias

In this article, we will discuss the Definition of Tachyarrhythmias. So, let’s get started.

Definition

Any arrhythmia with heart rate more than 150/min is defined as tachyarrhytmia. They occur more often in diseased rather than normal hearts. Those tachycardias that are initiated by an APC (atrial premature complexes) or a VPC (ventricular premature complexes) are considered to be due to an re-entry mechanism except digitalis induced arrhythmias which are due to triggered activity. In a hemodynamically stable patient, an attempt should be made to find out the mechanism and origin of tachycardia by examining the patient clinically and by recording a 12 lead surface ECG. This is important for appropriate therapeutic decision.

The ECG will give information regarding:

  • The presence or absence of P-wave, frequency, morphology and regularity of P-waves as well as QRS complexes
  • Relationship of P-wave to QRS complexes
  • A comparison of QRS morphology can be made during sinus rhythm and during an episode of tachycardia. It is useful to summon the ECG before tachycardia, i.e. recorded during sinus rhythm
  • If necessary, an esophageal lead may be used to define supraventricular tachycardia by recording the atrial activity (P-waves)
  • The response to carotid sinus massage or other vagomimetic maneuvers such as Valsalva maneuver, immersion of face in cold water and administration of 5-10 mg edrophonium

Clinical Observations

1. Examination of jugular venous pulse is important because ‘a’ wave will be absent in atrial fibrillation

2. Arterial pulse will reveal regularly irregular pulse in ventricular ectopy and irregularly irregular pulse in atrial fibrillation. The pulse deficit is <10 beats/min in frequent VPCs but is >10/min in atrial fibrillation

3. Cannon ‘a’ wave suggests AV dissociation, complete AV block and nodal rhythm

4. Variable intensity of first heart sound during an arrhythmia suggests AV dissociation or heart block or atrial fibrillation.

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