During a sudden cardiac arrest (SCA) event, healthcare professionals need to make the most of every second in order to maximize a victim's chance of survival. Performing regular rhythm checks — by temporarily pausing compressions — is a standard step when treating SCA victims. This creates a challenging scenario where a rhythm check could ultimately be harmful to the patient.

Recent advances in medical technology have made it possible to perform a rhythm analysis during cardiopulmonary resuscitation (CPR) using See-Thru CPR^®. This technology filters out the compression artifact on the ECG monitor, allowing rescuers to see the underlying heart rhythm during CPR, thereby shortening pause times.

What Is a Rhythm Check?

Rhythm checks during CPR determine if a heart is beating at a shockable or healthy rhythm. When treating a patient with arrhythmia, perform a rhythm check of 10 seconds or less after every two minutes (or five cycles) of CPR. If a shockable rhythm is detected, the care team should defibrillate the patient to correct it. If a healthy rhythm is detected, the care team can perform a pulse check to determine if the patient is experiencing the return of spontaneous circulation (ROSC).

The Importance of Analyzing Cardiac Rhythm During CPR

A key recommendation of the 2020 American Heart Association Guidelines for CPR and ECC is to minimize interruptions in CPR. One of the most common reasons to interrupt the delivery of CPR is to determine whether an organized, shockable rhythm has developed, responders must make these rhythm and pulse checks as brief as possible.

With patented See-Thru CPR technology from ZOLL^®, it's possible to constantly visualize a patient's cardiac rhythm without stopping to perform a manual rhythm check. This technology, available exclusively on ZOLL defibrillators, allows the professional rescuer to analyze the heart rhythm during CPR to determine the appropriate time to stop and check the ECG.

How See-Thru CPR Checks Cardiac Rhythm

In See-Thru CPR, ECG signal processing extracts the CPR artifact from the ECG.

Below is an actual waveform generated during CPR, one of the many collected while validating this technology. The filtered signal shows that there is an underlying, organized rhythm; if a pulse is also present, CPR can cease. ZOLL recommends that rescuers stop CPR to confirm the rhythm is shockable prior to shocking.