Atrial fibrillation (AFib) is a common type of irregular heartbeat, or arrhythmia, where the upper chambers of the heart, the atria, beat rapidly and chaotically. This disorganized electrical activity can lead to inefficient pumping of blood and may increase the risk of complications such as blood clots, stroke, and heart failure. This article will clarify how electrical therapy can be used to manage this condition.
What is a Shockable Heart Rhythm
A “shockable rhythm” refers to specific abnormal heart rhythms that can be corrected by delivering an electrical shock to the heart. This intervention, known as defibrillation, aims to momentarily stop all electrical activity, allowing the heart’s natural pacemaker to reset to a normal rhythm. The two primary shockable rhythms encountered in emergency cardiac arrest situations are ventricular fibrillation (VFib) and pulseless ventricular tachycardia (VT).
In ventricular fibrillation, the heart’s lower chambers, the ventricles, quiver ineffectively instead of pumping blood, leading to immediate loss of consciousness. Pulseless ventricular tachycardia involves a very rapid, but organized, electrical activity in the ventricles that is too fast to produce a palpable pulse or effective blood flow. Non-shockable rhythms like asystole (no electrical activity) and pulseless electrical activity (organized electrical activity without a heartbeat) do not respond to defibrillation. In these cases, cardiopulmonary resuscitation (CPR) and medications are the primary treatments.
Atrial Fibrillation and Electrical Cardioversion
Atrial fibrillation can indeed be treated with an electrical shock, but for AFib, this procedure is specifically termed electrical cardioversion (CPT code 92960), not defibrillation. While both involve delivering an electrical current, electrical cardioversion is a synchronized shock, timed to a specific point in the heart’s electrical cycle (the R-wave on an electrocardiogram). This synchronization prevents the shock from inducing more dangerous arrhythmias.
The goal of electrical cardioversion in AFib is to reset the heart’s erratic electrical activity and restore a normal sinus rhythm. During the procedure, electrode pads are placed on the patient’s chest, and a controlled electric shock is delivered. The shock briefly interrupts abnormal electrical signals, allowing the heart’s natural pacemaker to regain control and establish a regular heartbeat.
Defibrillation, in contrast, delivers an unsynchronized, higher-energy shock for life-threatening emergencies with no organized electrical activity or pulse.
When Electrical Cardioversion is Used
Electrical cardioversion is used for atrial fibrillation in urgent and planned situations. In emergency cases, such as when AFib with a rapid ventricular response causes hemodynamic instability (e.g., low blood pressure, acute heart failure, or chest pain), immediate electrical cardioversion is performed to restore a stable heart rhythm.
For patients with stable AFib, electrical cardioversion is often an elective, planned procedure, particularly for those with persistent or symptomatic AFib that has not responded to medications. Before an elective cardioversion for AFib lasting more than 48 hours or of unknown duration, patients are typically placed on anticoagulant medications for at least three to four weeks to prevent the formation of blood clots in the heart’s upper chambers.
This preparation significantly reduces the risk of stroke if a clot dislodges when the heart’s rhythm returns to normal. Alternatively, a transesophageal echocardiogram (TEE) may be performed immediately before the procedure to rule out existing clots.
Other Treatments for Atrial Fibrillation
Beyond electrical cardioversion, several other treatment approaches are commonly used to manage atrial fibrillation, focusing on either controlling the heart rate or restoring and maintaining a normal rhythm. Rate control strategies aim to slow down the heart’s ventricular response to the chaotic atrial activity, thereby reducing symptoms and improving cardiac efficiency. Medications such as beta-blockers (e.g., metoprolol, bisoprolol) and calcium channel blockers (e.g., diltiazem, verapamil) are frequently prescribed for this purpose. Digoxin is another medication that can be used to slow the electrical signals from the upper to the lower chambers of the heart.
Rhythm control strategies, on the other hand, aim to restore and maintain a normal sinus rhythm. This can involve antiarrhythmic medications like sodium channel blockers (e.g., flecainide, propafenone) or potassium channel blockers (e.g., amiodarone, sotalol, dofetilide, dronedarone). For some patients, catheter ablation (CPT code 93656) is an option, a procedure where small catheters are guided into the heart to deliver energy (radiofrequency or cryoablation) to specific areas of heart tissue responsible for generating or perpetuating the abnormal electrical signals, often focusing on isolating the pulmonary veins.