Approach to Tachyarrhythmias

Approach to Tachyarrhythmias is a topic covered in the Washington Manual of Medical Therapeutics.

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General Principles

  • Tachyarrhythmias are encountered in both the inpatient and outpatient settings.
  • Recognition and analysis of these rhythms in a stepwise manner will facilitate initiation of appropriate therapy.
  • Clinical decision-making is guided by patient symptoms and signs of hemodynamic stability.

Definition

Cardiac rhythms whose ventricular rate exceeds 100 beats per minute (bpm).

Classification

Tachyarrhythmias are broadly classified into the following based on the width of the QRS complex on the ECG.

  • Narrow-complex tachyarrhythmia (QRS <120 ms): Arrhythmia originates within the atria (supraventricular tachycardia [SVT]) and rapidly activates the ventricles via the His-Purkinje system.
  • Wide-complex tachyarrhythmia (QRS ≥120 ms): Arrhythmia originates within the ventricles and does not depend on the His-Purkinje system (ventricular tachycardia [VT]) or originates in the atria and travels to the ventricles either via an abnormal His-Purkinje system (SVT with aberrancy) or through an accessory pathway.

Etiology

Mechanism is divided into disorders of impulse conduction and impulse formation:

  • Disorders of impulse conduction: Reentry is the most common mechanism of tachyarrhythmias. A reentrant mechanism can occur when differential refractory periods and conduction velocities allow for propagation of an activation wavefront in a unidirectional manner around a zone of scar or refractory cardiac tissue. Reentry of the activation wavefront around a myocardial circuit sustains the arrhythmia (e.g., VT).
  • Disorders of impulse formation: Enhanced automaticity (e.g., accelerated junctional and accelerated idioventricular rhythm) and triggered activity (e.g., long QT syndrome [LQTS] and digitalis toxicity) are other less common mechanisms of tachyarrhythmias.

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General Principles

  • Tachyarrhythmias are encountered in both the inpatient and outpatient settings.
  • Recognition and analysis of these rhythms in a stepwise manner will facilitate initiation of appropriate therapy.
  • Clinical decision-making is guided by patient symptoms and signs of hemodynamic stability.

Definition

Cardiac rhythms whose ventricular rate exceeds 100 beats per minute (bpm).

Classification

Tachyarrhythmias are broadly classified into the following based on the width of the QRS complex on the ECG.

  • Narrow-complex tachyarrhythmia (QRS <120 ms): Arrhythmia originates within the atria (supraventricular tachycardia [SVT]) and rapidly activates the ventricles via the His-Purkinje system.
  • Wide-complex tachyarrhythmia (QRS ≥120 ms): Arrhythmia originates within the ventricles and does not depend on the His-Purkinje system (ventricular tachycardia [VT]) or originates in the atria and travels to the ventricles either via an abnormal His-Purkinje system (SVT with aberrancy) or through an accessory pathway.

Etiology

Mechanism is divided into disorders of impulse conduction and impulse formation:

  • Disorders of impulse conduction: Reentry is the most common mechanism of tachyarrhythmias. A reentrant mechanism can occur when differential refractory periods and conduction velocities allow for propagation of an activation wavefront in a unidirectional manner around a zone of scar or refractory cardiac tissue. Reentry of the activation wavefront around a myocardial circuit sustains the arrhythmia (e.g., VT).
  • Disorders of impulse formation: Enhanced automaticity (e.g., accelerated junctional and accelerated idioventricular rhythm) and triggered activity (e.g., long QT syndrome [LQTS] and digitalis toxicity) are other less common mechanisms of tachyarrhythmias.

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