ACLS Provider: Course

Tachycardia Recognition and Management

Tachycardia is defined as a heart rate greater than 100 bpm. The management of tachycardia depends on the patient's clinical stability (stable or unstable) and the width of the QRS complex (narrow or wide) on the ECG. These factors help determine the underlying cause and guide appropriate treatment.

Key ECG Rhythms Associated with Tachycardia

Several different ECG rhythms can present with tachycardia:

  • Sinus Tachycardia: A sinus rhythm with a heart rate greater than 100 bpm. P waves are present and normal in morphology. Sinus tachycardia is a normal physiological response to exercise, stress, fever, or other conditions that increase metabolic demand.
  • Supraventricular Tachycardia (SVT): A rapid rhythm originating above the ventricles (in the atria or AV node). SVT is characterized by a narrow QRS complex (typically <0.12 seconds) and a rapid heart rate (often >150 bpm). P waves may be difficult to see or may be hidden within the T waves.
  • Ventricular Tachycardia (VT) (with a pulse): A rapid ventricular rhythm with wide QRS complexes (≥0.12 seconds). VT can be monomorphic (consistent QRS shape) or polymorphic (varying QRS shapes). In this section, we are discussing VT with a pulse. Pulseless VT is treated as a shockable rhythm (as covered earlier).
  • Atrial Fibrillation/Flutter: These atrial arrhythmias can result in a rapid ventricular response, leading to tachycardia. Atrial fibrillation is characterized by irregular atrial activity and irregular ventricular rhythm. Atrial flutter is characterized by a rapid, regular atrial rhythm with a sawtooth pattern on the ECG.

Management of Tachycardia

The management strategy depends on the patient's clinical stability and the QRS complex width:

  • Stable Tachycardia: A patient with stable tachycardia does not exhibit signs of hemodynamic instability (e.g., hypotension, altered mental status, shock).
  • Narrow QRS Complex (SVT):
    • Vagal Maneuvers: Vagal maneuvers (e.g., carotid sinus massage, Valsalva maneuver) can be attempted initially to slow the heart rate. These maneuvers stimulate the vagus nerve, which can slow AV nodal conduction and terminate some SVTs.
    • Adenosine: If vagal maneuvers are unsuccessful, adenosine is the first-line medication for stable, regular, narrow-complex tachycardias (SVT). Adenosine is a very short-acting AV nodal blocking agent that can transiently interrupt the re-entry circuit causing the SVT. It is given as a rapid IV push (6 mg initially, may repeat with 12 mg) followed by a saline flush.
  • Wide QRS Complex Tachycardia: If the patient is stable with a wide QRS complex tachycardia, antiarrhythmic medications such as amiodarone or procainamide may be considered. Expert consultation with a cardiologist is recommended in these cases to help guide medication selection and dosing.
  • Unstable Tachycardia: Unstable tachycardia is defined by the presence of signs and symptoms such as hypotension, altered mental status, chest pain, or acute heart failure. In these cases, synchronized cardioversion is the immediate treatment of choice. The energy level for cardioversion depends on the specific rhythm and the type of defibrillator being used.