The goal of this study is to measure survival rates associated with patients presenting in cardiac arrest based on their electrocardiographic rhythm and their echocardiographic rhythm. Electrocardiographic rhythm is defined as the rhythm on the ECG and echocardiographic rhythm is the rhythm visualized on bedside ultrasound. Specifically, we will categorize patients based on identical rhythms and dichotomous rhythms with an interest in outcomes in the patient group where their echocardiographic and electrographic rhythms do not match. This is important as current ACLS protocols use electrocardiographic rhythms to determine therapy but limited research implies that therapeutic decisions based on echocardiographic rhythm may produce increased survival.

This study will occur during emergency department resuscitation of patients presenting in cardiac arrest. Patients presenting to the emergency department after cardiac arrest will undergo standard resuscitation based on ACLS protocols. Ultrasound imaging will be performed as soon as possible after the patient arrives and digitally recorded, as is currently the standard of care at the institute. Simultaneous recording of the ECG rhythm strip will occur as well. This will be repeated for as many pauses in CPR as is warranted.

Each site will record data based on the Utstein nomenclature including patient demographics, arrest details and survival outcomes. Ultrasound images and ECG recordings will be de-identified and submitted to a central database. Data will be uploaded into a centralized database. Statistical analysis will analyze outcomes based on echocardiographic and sonographic findings. Our aim is to measure the survival benefit of treating out of hospital cardiac arrest using echocardiographic rhythm instead of electrocardiographic rhythm.

This is a multi-center, prospective, observational trial involving sites across the United States and Canada. Patients will be enrolled through the emergency department either presenting in cardiac arrest, or going into cardiac arrest while in the emergency department after having arrested out of hospital. Advanced Cardiac Life Support (ACLS) protocols and institutional policies for resuscitation will be followed, as is the current standard of care. A patient encounter will conclude upon halting of cardiopulmonary resuscitation. Patient outcome will be evaluated by chart review or follow-up.

Programs involved in this study must have already integrated echocardiography into Cardiac Arrest clinically and have established procedures for how imaging is performed in the context of CPR. Echocardiography will not hinder or impair resuscitative efforts in any way, including halting CPR or prolonging pauses in CPR. Sonographic images will be obtained during designated pauses in chest compressions, as is routine care, during CPR for pulse checks, rhythm checks, and necessary resuscitative procedures.

Echocardiography will be performed as appropriate to obtain diagnostic information for each particular patient during resuscitative efforts. Recording of the image loops will be performed during image acquisition according to standard technology availability and clinical protocols at each site. To facilitate image acquisition, the ultrasound probe may be placed in the epigastrium or parasternal region during CPR with the heart centered in the field of view, if it will not interfere with ongoing resuscitation. Recording of the images can begin immediately upon pauses of CPR using whatever means are available at the site. Sonographic images will be obtained by competent personnel with experience in bedside cardiac ultrasound. This information will be made available to the physician taking care of the patient.

Continuous ECG tracings are displayed during cardiac arrest, and for the purpose of this study recordings of these ECG tracings will need to be digitally recorded. These digital ECG 'rhythm strips" will be matched with contemporaneous recordings of the ultrasound images of the heart.

Subject data, with identifiers removed, will be uploaded into the REDcap web-based database. Data will be obtained from initial patient encounter, patient records, and EMS records when available.

Contemporaneous digital recordings of ultrasound images and ECG rhythm strips blinded to patient identifiers will be included in a centralized database. Echocardiographic images will be reviewed and interpreted by the central coordinating site blinded to patient information. ECG images will be reviewed and interpreted by the central coordinating site blinded to patient information.

Patient cohorts will be compared for the electrical activity by ECG and the myocardial activity by echo.

Inclusion Criteria:

• Patients presenting in out-of-hospital, atraumatic cardiac arrest

Exclusion Criteria:

• Resuscitation ended due to end of life decisions
• Documented allergy to ultrasound gel
• Technical malfunction of ultrasound machine during imaging that prevents use Ultrasound machine unable to record images

Patients presenting after out of hospital cardiac arrest to the emergency department.

As a cardiac arrest study, there is not a current plan to share individual data but this may be reconsidered if required