Chapter 31 — Cardiac Arrest and the Peri-Arrest Period

📚 Guideline basis

2025 AHA Guidelines for CPR and Emergency Cardiovascular Care, Part 9 (Adult Advanced Life Support) and Part 11 (Post–Cardiac Arrest Care); ERC 2021 Adult Advanced Life Support; Gehring et al., Chest 2019 (PMID 31580845); Spiering et al., J Am Soc Echocardiogr 2019 (PMID 31421279).

Guideline position

The 2025 AHA guidelines state that use of point-of-care ultrasonography by experienced professionals during cardiac arrest may be considered to diagnose reversible causes, if it can be done without interrupting resuscitative efforts (i.e. CPR). This is a conditional recommendation, and its conditions are the substance of it: experienced professionals, and without interrupting CPR.

For the post-arrest period, the 2025 guidelines state that it may be reasonable to perform echocardiography or point-of-care cardiac ultrasound for adult patients after ROSC to identify clinically significant diagnoses requiring intervention (Class 2b, LOE C-LD), alongside a 12-lead ECG (Class 1, LOE B-NR) and consideration of head-to-pelvis CT (Class 2b, LOE B-NR).

The ERC 2021 guidelines similarly upgraded focused echocardiography during ALS while specifying that it be performed only by experienced users and that pauses in compressions not exceed the 10 seconds accepted for a pulse check.

The direction of travel across both bodies is identical: ultrasound during arrest is permitted, potentially valuable for identifying reversible causes, and subordinate to compression quality. No guideline recommends it as a routine or mandatory component of ALS, and no trial has demonstrated improved survival from its use.

The compression-interruption problem

Observational data consistently show that ultrasound during cardiac arrest prolongs pulse-check pauses, in several studies to roughly twice the intended duration, and prolonged peri-shock and pulse-check pauses are associated with worse survival. This is the dominant harm and it is a procedural, not a diagnostic, problem.

Mitigations, in order of effectiveness:

1. Pre-position the probe before the pause is called. Subxiphoid or parasternal, probe on the chest, image acquired the instant compressions stop.
2. Nominate a dedicated sonographer who is not part of the compression or airway team, and who is accountable to a timekeeper.
3. Record a 6–10 second loop and stop. Interpret the clip after compressions resume. Never interpret live.
4. Announce the time. The timekeeper counts aloud; the probe leaves the chest at 10 seconds regardless of image quality.
5. Use transesophageal echocardiography where available. TEE is the technical solution: continuous imaging during compressions, with zero interruption.

Pathophysiology & Clinical Synthesis

Pulseless electrical activity: true versus pseudo-PEA

The most consequential distinction ultrasound makes in arrest.

Cardiac standstill on ultrasound during arrest is strongly associated with non-survival across multiple observational cohorts, but it must not be used as the sole criterion for terminating resuscitation. Contributing considerations: image quality is frequently poor during arrest; standstill has been reported in patients who subsequently achieved ROSC; and the finding has never been validated as a stand-alone termination rule.

Reversible causes and their echocardiographic signatures

⚠️ The RV-dilatation caveat

A dilated right ventricle during cardiac arrest is not diagnostic of pulmonary embolism. RV dilatation develops as a consequence of cardiac arrest and of CPR itself, and is present in a large proportion of arrests from any cause within minutes. Using isolated RV dilatation to justify thrombolysis during arrest is an error with major bleeding consequences. Supportive features that raise specificity: RV dilatation documented before arrest, visible thrombus-in-transit, a clinical prodrome consistent with PE, and known risk factors.

Peri-arrest: preventing the arrest

The highest-value application is not during arrest but before it. In a deteriorating patient, focused echocardiography identifies the mechanism while intervention is still possible: the dilating RV of a submassive PE, the accumulating effusion, the collapsing LV of an evolving infarct, the dynamic LVOT obstruction produced by the inotrope that was started an hour ago.

Every ICU patient with unexplained deterioration and rising vasopressor requirement warrants a focused study before, not after, arrest.

Post-ROSC

Sequence in the first hour after ROSC:

1. 12-lead ECG immediately (Class 1) — echocardiography does not replace it and does not delay it.
2. Focused echocardiography to identify: regional wall motion abnormality suggesting an ischaemic cause; global stunning; RV dysfunction; pericardial effusion (including complications of CPR); valvular catastrophe; and to establish a baseline flow state.
3. Quantify flow — LVOT VTI, stroke volume index, and Ea (Chapter 10). Post-arrest shock is characteristically mixed: myocardial stunning (low Ees) plus a systemic inflammatory vasoplegia (low Ea).
4. Serial reassessment. Post-arrest myocardial stunning typically nadirs within hours and recovers over 24–72 hours in survivors. Serial VTI documents the trajectory and informs decisions about mechanical support.
5. Exclude CPR complications — pericardial effusion or haemopericardium, and (with lung ultrasound) pneumothorax and haemothorax.

Regional wall motion abnormality after ROSC has to be interpreted with care: global stunning can produce regional-appearing dysfunction, and stress cardiomyopathy after arrest is common. RWMA supports, but does not establish, an ischaemic aetiology; it should be considered together with the ECG and troponin.

Therapeutic Logic

🛑 Critical pitfall: Interpreting the image live while compressions are held. Acquire a loop, resume compressions, then interpret. Live interpretation is the mechanism by which pauses double in length.

🛑 Critical pitfall: Thrombolysing on isolated intra-arrest RV dilatation. It is a near-universal finding in arrest of any cause.

🛑 Critical pitfall: Terminating resuscitation on cardiac standstill alone. It has not been validated as a stand-alone rule and its image quality during arrest is often poor.

• 💡 Clinical pearl: If TEE is available and an airway is in place, use it. It is the only modality that images continuously during compressions and it additionally allows verification of compression location — the AHA-recommended compression point often lands over the LV outflow tract rather than the ventricle itself, and TEE permits correction.
• 💡 Clinical pearl: Pseudo-PEA is a fundamentally different clinical entity from true PEA and carries a materially better prognosis. Making the distinction changes the energy the team invests in the resuscitation.
• 💡 Clinical pearl: Assign the probe to someone with no other role. A sonographer who is also running the code will prolong the pause.

References

1. Wigginton J, et al. Part 9: Adult Advanced Life Support: 2025 American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care. Circulation 2025. doi:10.1161/CIR.0000000000001376
2. Part 11: Post–Cardiac Arrest Care: 2025 American Heart Association Guidelines for CPR and ECC. Circulation 2025. doi:10.1161/CIR.0000000000001375
3. Soar J, Böttiger BW, Carli P, et al. European Resuscitation Council Guidelines 2021: Adult advanced life support. Resuscitation 2021;161:115–51.
4. Gehring et al. Point-of-care ultrasound in critical care. Chest 2019. PMID 31580845.
5. Spiering et al. Focused cardiac ultrasound. J Am Soc Echocardiogr 2019. PMID 31421279.