Electrical Cardioversion (ECV)

What is external electrical cardioversion?

External electrical cardioversion (ECV) is a procedure that can interrupt cardiac arrhythmias, particularly atrial fibrillation, by performing a sort of “reset” of the heart rhythm. Every normal heartbeat begins in an area of the heart known as a “sinus node,” which is located in the right atrium of the heart. The sinus node contains specialized cells that generate an electrical signal, which is then transmitted to the myocardium through the conduction system. In patients with atrial fibrillation, there is chaotic electrical activity at the level of the atria, which therefore does not generate an effective contraction, and an accelerated and irregular heartbeat occurs.

Atrial fibrillation is often felt by patients as palpitations (sense of fast and irregular heartbeat). While some patients have no symptoms, others may experience shortness of breath, lightheadedness, and fatigue. Depending on the specific clinical history and symptoms, ECV may be recommended to restore normal heartbeat.

When to perform electrical cardioversion?

The ECV can be performed as a scheduled or emergency procedure (for example in the emergency room).

In an emergency, ECV is performed to correct arrhythmias that impair cardiac performance generally associated with fainting, low blood pressure, chest pain, difficulty breathing, or unconsciousness.

Most ECVs are performed electively (not urgently) to treat atrial fibrillation, atrial flutter, and other heart rhythm disorders. The programmed ECV is a procedure that usually requires hospitalization (generally in Day Hospital).

Before performing electrical cardioversion, the cardiologist informs the patient about the procedure and, after signing the informed consent, preparation begins.

It should be noted that in arrhythmias lasting more than 48 hours, thrombus formation can occur in some parts of the atrium (in particular in the auricle); the thrombi, at the resumption of atrial contractility, could fragment and disseminate in the arterial circulation causing strokes or embolisms.

For this reason, if more than 48 hours have elapsed since the onset of symptoms, it is mandatory to first perform anticoagulant therapy (with low molecular weight heparins or oral anticoagulants), after which it is possible to carry out ECV safely, minimizing cardioembolic risks. The use of new direct-acting oral anticoagulants (DOAC, direct thrombin inhibitors), compared to warfarin, exhibit a delayed onset of action, drastically reducing the time required before the ECV is able to be carried out safely.

In our center, if the origin of the arrhythmia is greater than 72 hours or unknown, the execution of the procedure, is always dependent on the outcome of a transesophageal echocardiogram, which is performed after rapid sedation, which serves to exclude the possible presence of thrombus inside the cardiac cavities (an event whose risk appears to be increased in all patients suffering from cardiac arrhythmias).

How is electrical cardioversion performed?

The ECV procedure is always performed in a hospital setting in the equipped Electrophysiology rooms, under the supervision of a team composed of a cardiologist, an anesthesiologist, and a nurse. All vital parameters are checked before, during, and after shock delivery.

In order to avoid painful perceptions due to electrical discharge, the ECV is performed in deep sedation obtained through an intravenous bolus of hypno-inductive and anesthetic drugs. The patient does not feel any discomfort, but is autonomous in vital functions, so it is not a general anesthesia. Given the specific use of hypno-inductive and anesthetic drugs, the presence of the anesthesiologist is necessary in our center.

The execution of the ECV necessitates the delivery (by means of a defibrillator) of a synchronized biphasic electric discharge, through two metal plates positioned on the chest of the patient, in a right subclavicular left-apical or the antero-posterior position.

Once the sedation has been ascertained and the vital parameters, such as BP and oxygen saturation (Spo2), have been verified, the cardiologist, based on the weight of the patient, selects the amount of energy needed (1-2 Joules / Kg) and synchronizes the delivery of the shock with ECG on peak R; the discharge must be synchronized, since if the discharge were to occur on the T wave it could trigger a ventricular arrhythmia.

The passage of electric current resets the anomalous circuits, allowing the restoration of the sinus rhythm (often preceded by a brief sinus pause). If the restoration of sinus rhythm does not occur at the first discharge, up to 3 shocks can be repeated, progressively increasing energy.

Usually the restoration of normal heart rhythm occurs in 75-90% of cases in recent onset atrial fibrillation and in 90-100% in case of flutter. At this point, the patient is woken up and the vital signs are monitored.

WHAT HAPPENS AFTER THE ECV? 

After the procedure, the patient remains in observation for about 6-7 hours, after which he/she can be discharged. Because of the residual effects of the drugs used for sedation, patients are prohibited from driving for 24 hours.

Very often, to decrease the risk of recurrence, the cardiologist prescribes an anti-arrhythmic therapy, even after the restoration of sinus rhythm. Subsequent clinical evaluations and therapeutic strategies are planned on a case-by-case basis.