Cardioversion is a medical procedure that uses quick, low-energy electrical shocks to the chest to restore a normal heart rhythm. It corrects abnormal heart rhythms, known as arrhythmias, allowing the heart to pump blood effectively.
Understanding Synchronized Cardioversion
Synchronized cardioversion uses an electrical current to correct abnormal heart rhythms. It differs from defibrillation through its precise timing, delivering a controlled electrical shock synchronized with the heart’s own electrical activity. The goal is to reset the heart’s electrical system, encouraging a regular rhythm. Unlike defibrillation, which uses higher energy for pulseless rhythms, synchronized cardioversion uses lower energy for patients with a pulse.
The Role of Synchronization
The electrical shock during synchronized cardioversion occurs precisely on the R-wave of the electrocardiogram (ECG). This timing is deliberate to avoid delivering the shock during the T-wave, which represents the heart’s vulnerable repolarization phase. Delivering a shock during this sensitive period, known as the R-on-T phenomenon, could trigger a more dangerous rhythm like ventricular fibrillation, potentially leading to cardiac arrest.
The cardioverter machine detects the R-wave, which signifies ventricular contraction. After identifying the R-wave, it delivers the electrical shock a few milliseconds later. This brief delay ensures the shock avoids the T-wave, acting as a safety mechanism. Healthcare providers activate a “sync” button to engage this feature, allowing precise timing of energy delivery.
Conditions Requiring Synchronized Cardioversion
Synchronized cardioversion is performed for heart rhythm disorders that cause patient instability. These include atrial fibrillation with a rapid ventricular response, atrial flutter, and supraventricular tachycardia (SVT). It is also indicated for stable ventricular tachycardia where the patient still has a pulse. These arrhythmias can cause symptoms like chest discomfort, shortness of breath, dizziness, or altered mental status because the heart is unable to pump blood effectively.
The procedure is considered when medications have not successfully converted the rhythm, or when the patient’s condition is deteriorating. Atrial flutter often responds to lower energy levels for conversion compared to atrial fibrillation. The aim is to restore a normal sinus rhythm, improving the heart’s pumping efficiency and alleviating distressing symptoms.
Patient Preparation and Procedure
Preparing for synchronized cardioversion involves several steps to ensure patient comfort and procedural effectiveness. Patients are typically asked to refrain from eating or drinking for at least six to eight hours before the procedure. Prior to the electrical shock, sedative or anesthetic medications are administered intravenously, as the procedure can cause discomfort. This ensures the patient is relaxed and experiences minimal sensation during the brief electrical discharge.
During the procedure, ECG leads are placed on the patient’s chest to continuously monitor the heart’s electrical activity. Adhesive pads or paddles are also positioned on the chest, either in an anterolateral or anteroposterior configuration, to deliver the electrical energy. The medical team ensures the cardioversion device is set to synchronized mode, visibly confirming that it is detecting and marking each R-wave on the monitor before the shock is delivered. After confirming the area is clear of personnel, the shock is delivered, and the patient’s heart rhythm is immediately reassessed.