Critical medicine topic-CMT 005

 ACCELERATED IDIOVENTRICULAR RHYTHM (AIVR)

IN ACUTE MYOCARDIAL INFARCTION (AMI)

Definition

·        Accelerated idioventricular rhythm (AIVR) is a ventricular escape rhythm with a heart rate of 60–100 beats/min.

·        It is often referred to as "slow ventricular tachycardia."

Incidence

·        Occurs in up to 20% of patients with acute myocardial infarction (AMI).

·        Most commonly appears during the first 48 hours after AMI.

Association with Reperfusion

·        AIVR is the most common arrhythmia following successful reperfusion of an occluded coronary artery.

·        Frequently seen after fibrinolytic (thrombolytic) therapy and is considered a marker of reperfusion.

Mechanism of Initiation

Episodes of AIVR develop by two principal mechanisms:

·        Approximately 50% are initiated by a premature ventricular beat (PVC).

·        The remaining 50% occur due to:

o   Sinus node slowing, or

o   Gradual acceleration of a ventricular pacemaker, allowing it to emerge as an escape rhythm.

Clinical Characteristics

·        Usually short-lived and self-limiting.

·        The ventricular rate often varies during the episode.

·        Typically causes minimal or no symptoms.

Prognostic Significance

·        Unlike sustained ventricular tachycardia, AIVR generally does not worsen prognosis in patients with AMI.

·        There is no convincing evidence that isolated AIVR increases the risk of:

o   Ventricular fibrillation.

o   Mortality.

Potential Complications

·        Occasionally, AIVR may accelerate into sustained ventricular tachycardia, requiring treatment.

·        Rarely, it may produce hemodynamic instability.

Management

Treatment is usually unnecessary, as AIVR is transient and benign.

Intervention is indicated only if hemodynamic compromise occurs:

·        Increase sinus rate with:

o   Atropine, or

o   Atrial pacing.

·        Suppress ventricular automaticity with:

o   Lidocaine, when appropriate.

Critical Clue

·        Ventricular escape rhythm with rate 60–100 beats/min.

·        Common during the first 2 days of AMI.

·        Most common reperfusion arrhythmia after fibrinolytic therapy.

·        Usually self-limiting and benign.

·        Does not independently increase the risk of ventricular fibrillation or mortality.

·        Treat only if symptomatic or hemodynamically significant.

 DR.C.GANESAN M.D.,

                PROFESSOR OF MEDICINE