Cardioversion is a medical procedure used to reset an irregular heart rhythm (arrhythmia) back to a normal, steady pattern called sinus rhythm. This treatment is often employed for conditions like atrial fibrillation (AFib) or atrial flutter, where the heart’s electrical signals are chaotic or too fast. The goal is to immediately stop the irregular rhythm, using either a controlled electrical shock or specific medications. Cardioversion is a key part of managing the heart’s rhythm and alleviating associated symptoms.
Immediate Duration of the Procedure
The actual procedure is brief, but the overall time commitment is longer due to preparation and monitoring. Electrical cardioversion (DC cardioversion) is an outpatient procedure typically requiring the patient to be at the facility for three to four hours in total. Preparation involves placing an intravenous (IV) line, attaching monitoring electrodes, and administering a short-acting sedative so the patient is asleep during the shock.
The electrical shock itself lasts less than one second. The medical team may deliver multiple shocks if the first attempt does not successfully restore the normal rhythm. The direct procedure time, from sedation to shock delivery, often takes only about five minutes. Afterward, patients are monitored in a recovery area for an hour or more as the sedation wears off and the team confirms the heart maintains the new rhythm.
Pharmacological, or chemical, cardioversion uses anti-arrhythmic medication delivered orally or through an IV to restore the normal rhythm. This method does not require sedation, but it takes longer to work than electrical shock, potentially minutes, hours, or even a few days. Because of the time required for the medication to work and the need for close heart function monitoring, chemical cardioversion is often performed in a hospital setting, sometimes requiring a stay of two to three days.
Understanding Long-Term Efficacy
How long cardioversion “lasts” refers to the sustainability of the normal sinus rhythm after the procedure. Cardioversion is not a permanent cure for the underlying condition, but a way to restart the heart’s electrical system. For patients with atrial fibrillation, immediate success in restoring normal rhythm is high, typically 70% to over 90%.
The challenge lies in maintaining this rhythm over time, as the underlying factors causing the irregular rhythm remain. Recurrence is common, with the highest rate of relapse occurring within the first few weeks or months. Across studies, approximately 50% of patients who had a successful initial cardioversion remain in sinus rhythm after one year. In some groups, the rate of being free from atrial fibrillation at one year can be as low as 15% to 34%.
The outcome is described as a “rhythm control” strategy, focusing on keeping the heart in a regular rhythm, which contrasts with a “rate control” strategy that focuses on keeping the heart rate slow. Cardioversion serves as a way to temporarily restore rhythm and evaluate the symptomatic benefits of being in a normal rhythm. The procedure is typically followed by a long-term plan involving anti-arrhythmic medications to help prolong the duration of the normal rhythm.
Variables That Influence Duration
The duration of the cardioversion effect depends on several patient and disease-specific factors. One primary predictor is the length of time the patient has been in the irregular rhythm before the procedure. A shorter duration of the arrhythmia, such as less than three to six months, is associated with a better chance of maintaining sinus rhythm long-term.
The severity of structural heart disease also plays a role, particularly the size of the left atrium, where atrial fibrillation often originates. Patients without enlargement of the left atrium have an improved likelihood of staying in normal rhythm for a year. The use of anti-arrhythmic drugs following the procedure is important, as these medications are designed to reduce the chance of recurrence.
Other patient characteristics, such as advanced age and the presence of co-morbidities like obesity or hypertension, can negatively affect the long-term outcome. The presence of treated hypertension has also been identified as a factor associated with being free from atrial fibrillation one year after the procedure. The underlying health of the heart muscle dictates its propensity to revert to the irregular rhythm.
Managing Recurrence of Irregular Heart Rhythm
When the irregular rhythm returns following cardioversion, the management strategy shifts to prevent further recurrence and control symptoms. The first step often involves adjusting or changing the patient’s anti-arrhythmic drug regimen. These medications can be effective in reducing the frequency and duration of recurrent episodes.
If the rhythm returns after a successful initial cardioversion, a repeat procedure may be considered. Many patients undergo serial cardioversions; however, while the second attempt often has a good immediate success rate, long-term returns may diminish. For frequent recurrence poorly managed by medication, a more definitive procedure called catheter ablation is recommended. This involves creating scar tissue in the heart to block the abnormal electrical pathways that trigger the irregular rhythm.
In some cases, especially for older patients or those with multiple unsuccessful rhythm control attempts, the treatment focus may shift to a rate control strategy. This approach accepts the presence of the irregular rhythm but uses medications to keep the heart rate slow and controlled, which manages symptoms and reduces the risk of heart failure. The decision to pursue a different strategy is made collaboratively, considering the patient’s symptoms, overall health, and quality of life.