Cardioversion is the medical process of electrically shocking the heart to restore it to its normal beating pattern. Synchronized cardioversion is shock delivery that is timed with the QRS complex, also known as the deflections in the tracings of an electrocardiogram (EKG) that depict the heart's ventricular activity.

This synchronization avoids shock delivery during the relative refractory portion of the cardiac cycle, when a shock could produce ventricular fibrillation. The shock dose used for a synchronized shock is lower than that used for defibrillation.

Why Cardioversion Matters

Cardioversion may be necessary when drugs alone have not been able to convert an arrhythmia to a normal heart rhythm. Cardioversion restores the normal heart rate and rhythm, allowing the heart to pump more effectively.

The most common use of cardioversion is to treat atrial fibrillation or atrial flutter. But cardioversion may also be used to treat unstable supraventricular tachycardia, which could lead to ventricular fibrillation.

Who Needs Cardioversion?

Cardioversion therapy is beneficial for those who suffer from atrial flutter or atrial fibrillation, also known as a fast, irregular heartbeat. This condition occurs when the electrical signals that normally make your heart beat at a regular rate don't properly travel to the upper chambers of the heart. This can cause a fast heartbeat, fatigue, or shortness of breath.

How Cardioversion Works with R Series Defibrillators

Our R Series^® defibrillator helps rescuers restore a regular heart rhythm. Here's how to enable cardioversion with the R Series:

1. Press the SYNC soft key. The R Series defibrillator will enter SYNC mode and the synchronizing circuit within the defibrillator will detect the patient's R waves.
2. Press and hold the SHOCK button. The unit will discharge with the next detected R wave, thus avoiding the vulnerable T wave segment of the cardiac cycle.

When in the SYNC mode, the unit displays downward arrow markers above the ECG trace to indicate the points in the cardiac cycle (R waves) where discharge can occur, (see below):

The R Series defibrillator supports two types of synchronized cardioversion:

1. Synchronized Cardioversion — R Series monitors the patient's ECG and synchronizes shock delivery with this ECG source. Synchronized cardioversion provides a low-energy shock using a sensor that detects the highest point of the R-wave, creating a synchronized shock.
2. Remote Synchronized Cardioversion — Remote synchronized cardioversion works similarly to synchronized cardioversion, but it includes an external component. An external device (such as a patient monitor) monitors the patient's ECG and provides a synchronization pulse to the R Series defibrillator's Sync In/Marker Out connector. R Series synchronizes shock delivery with these external pulses.