In a 43‑year‑old man who received 45 minutes of CPR after ventricular fibrillation converted to pulseless electrical activity with epinephrine administered and fixed pupils, do audible heart tones indicate return of spontaneous circulation, and what is their significance in true versus pseudo‑PEA?

Heart Tones in Pulseless Electrical Activity (PEA)

Direct Answer: Audible Heart Tones Do NOT Indicate Return of Spontaneous Circulation

Audible heart tones during PEA do not indicate return of spontaneous circulation (ROSC) and should not alter your management—the absence of a palpable pulse remains the defining feature of cardiac arrest, regardless of whether heart sounds are audible or electrical activity is present on the monitor. 1

Understanding the Phenomenon

Why Heart Tones Can Be Heard Without a Pulse

• Organized electrical activity on the cardiac monitor can generate mechanical vibrations that produce audible heart sounds, yet this activity remains insufficient to produce a palpable pulse or measurable arterial pressure. 1
• This represents true electromechanical dissociation—the heart has electrical activity and may even have some mechanical contraction, but cardiac output is inadequate to generate a detectable pulse or blood pressure. 1
• PEA is defined as organized cardiac electrical activity without a detectable pulse or measurable blood pressure. 2, 1

The Critical Distinction: True PEA vs. Pseudo-PEA

• Bedside cardiac ultrasound should be performed immediately (without interrupting compressions for more than 10 seconds) to differentiate true PEA from pseudo-PEA, where actual cardiac wall motion may be present. 1
• Pseudo-PEA refers to situations where there is organized electrical activity with some cardiac contractility that may be detectable on ultrasound, but the pulse is still not palpable due to severe hypotension or poor peripheral perfusion. 1
• Physical examination findings, including pulse assessment, are frequently interpreted incorrectly during cardiac arrest, making ultrasound confirmation valuable. 1

Clinical Significance in Your Patient

Poor Prognostic Context

In your 43-year-old patient who received 45 minutes of CPR after VF converted to PEA:

• The development of secondary PEA after initial VF/VT is associated with lower rates of ROSC and reduced survival compared to maintaining a shockable rhythm. 1
• Fixed and dilated pupils after epinephrine administration are an expected pharmacologic effect and should not be considered an absolute contraindication to continued resuscitation or a definitive sign of irreversible brain injury. 1
• However, 45 minutes of CPR represents a prolonged resuscitation with increasingly poor prognosis, particularly after rhythm deterioration from VF to PEA. 2

Management Implications

• Continue high-quality CPR with minimal interruptions, administer epinephrine 1 mg IV/IO every 3-5 minutes, and aggressively search for reversible causes (the H's and T's). 2, 1
• The presence of audible heart tones should prompt immediate bedside ultrasound to assess for cardiac wall motion and identify potentially reversible causes such as cardiac tamponade, massive pulmonary embolism, or severe hypovolemia. 1
• If pseudo-PEA with cardiac contractility is identified on ultrasound, this may represent a more salvageable situation requiring aggressive treatment of the underlying cause. 1

The H's and T's: Reversible Causes to Address

Systematically evaluate and treat these potentially reversible causes during each 2-minute CPR cycle: 1

• Hypovolemia: Consider empirical IV/IO crystalloid bolus, especially if trauma or sepsis suspected 1
• Hypoxia: Ensure adequate oxygenation and ventilation; advanced airway placement is theoretically more important in PEA than VF 1
• Hydrogen ion (acidosis): Consider sodium bicarbonate 50 mEq if prolonged arrest or known hyperkalemia 2
• Hypo/hyperkalemia: Check point-of-care potassium if available 1
• Hypothermia: Assess core temperature 1
• Toxins: Consider specific antidotes if overdose suspected (e.g., higher epinephrine doses for beta-blocker or calcium channel blocker toxicity) 2, 1
• Tamponade (cardiac): Ultrasound assessment; consider pericardiocentesis if identified 1
• Tension pneumothorax: Immediate needle decompression if clinically suspected 1
• Thrombosis (coronary): Consider thrombolytics if suspected acute MI 1
• Thrombosis (pulmonary): For suspected massive PE, thrombolysis, surgical embolectomy, or mechanical embolectomy are reasonable emergency options, with early systemic thrombolysis associated with improved outcomes 1

Critical Pitfalls to Avoid

• Never assume ROSC based on audible heart tones alone—always confirm with palpable pulse (carotid or femoral) or arterial waveform on invasive monitoring. 2, 1
• Do not delay CPR to perform prolonged pulse checks; if no pulse is palpable within 10 seconds, resume compressions immediately. 2
• Avoid premature termination of resuscitation in PEA, as prolonged efforts may be successful, particularly in younger patients with reversible causes. 1
• Do not interpret fixed, dilated pupils as definitive evidence of brain death during active resuscitation with epinephrine—this is an expected pharmacologic effect. 1

Prognosis and Decision-Making

• PEA has substantially poorer survival outcomes compared to shockable rhythms (VF/VT), with survival to discharge rates of approximately 11% for PEA versus 36% for VF in adults. 2
• After 45 minutes of CPR with conversion from VF to PEA and fixed pupils, the likelihood of meaningful neurologic recovery is extremely low, though not zero. 2, 1
• Consider discussing termination of resuscitation efforts with the team if no reversible causes are identified and no ROSC has been achieved despite optimal CPR and appropriate medications. 2