Accelerated idioventricular rhythm

Accelerated Idioventricular Rhythm (AIVR) is a type of cardiac rhythm that is characterized by three or more consecutive ventricular beats at a rate of between 50 and 120 beats per minute. It is often associated with reperfusion therapy in the context of myocardial infarction (MI), but can also occur in other conditions such as digoxin toxicity and congenital heart disease.

Etiology

AIVR is most commonly seen in the setting of reperfusion following an acute MI, particularly after thrombolytic therapy or percutaneous coronary intervention (PCI). It can also occur in patients with digoxin toxicity, congenital heart disease, myocarditis, and cardiomyopathy. In addition, it can be seen in healthy individuals, particularly during periods of high sympathetic activity such as exercise or stress.

Pathophysiology

The exact mechanism of AIVR is not fully understood. It is thought to be due to enhanced automaticity of ventricular myocytes, possibly related to reperfusion injury or electrolyte abnormalities. The rhythm originates from the Purkinje fibers or ventricular myocardium, and is therefore characterized by wide and bizarre QRS complexes.

Clinical Features

AIVR is usually asymptomatic and is often discovered incidentally on electrocardiogram (ECG). However, in some cases, it can cause symptoms such as palpitations, dizziness, or syncope due to reduced cardiac output. In rare cases, it can degenerate into ventricular tachycardia or ventricular fibrillation, leading to cardiac arrest.

Management

The management of AIVR is primarily supportive, as the rhythm is usually self-limiting and does not require specific treatment. However, in cases where AIVR is causing symptoms or is associated with hemodynamic instability, treatment may be required. This can include antiarrhythmic drugs, cardioversion, or in some cases, implantable cardioverter-defibrillator (ICD) implantation.

Prognosis

The prognosis of AIVR is generally good, as it is often a transient and self-limiting condition. However, the underlying cause of the AIVR can significantly impact the patient's prognosis. For example, in the context of an acute MI, the presence of AIVR can be a sign of successful reperfusion, but the overall prognosis will depend on the extent of the MI and the patient's overall cardiac function.