Audible Heart Sounds During PEA Are Normal and Do Not Indicate a Pulse
Yes, it is completely normal to hear heart sounds during pulseless electrical activity (PEA), and these sounds do NOT mean the patient had a true pulse. The presence of organized electrical activity on the monitor can produce audible heart sounds even when there is insufficient mechanical cardiac output to generate a palpable pulse or measurable blood pressure 1.
Understanding PEA and Cardiac Sounds
PEA is defined as organized cardiac electrical activity without a detectable pulse or blood pressure, representing a critical cardiac arrest state 2. The key distinction is:
- Electrical activity (visible on monitor) can exist alongside mechanical activity (heart muscle contracting enough to produce sounds) without generating adequate circulatory output (palpable pulse or blood pressure) 1
- The term "electromechanical dissociation" was historically used to describe this exact phenomenon—coordinated electrical waveforms with absent or undetectable mechanical activity 1
Why Pulse Assessment Is Unreliable
Physical examination findings, including pulse assessment, are frequently interpreted incorrectly during cardiac arrest 2. This is a critical pitfall because:
- Pulse checks should not exceed 10 seconds; if no pulse is definitely felt, CPR must resume immediately 3
- The absence of a palpable pulse is the defining feature of cardiac arrest, not the absence of all cardiac activity 1
The Role of Bedside Ultrasound
Bedside cardiac ultrasound should be performed immediately in PEA to differentiate true PEA from pseudo-PEA 2, 4. This distinction matters because:
- Pseudo-PEA shows organized cardiac wall motion on ultrasound despite no palpable pulse and has significantly better outcomes than true PEA 4
- Pseudo-PEA patients have ROSC and survival rates approaching those of VF/VT, the most favorable arrest rhythms 4
- The ultrasound examination should not interrupt chest compressions for more than 10 seconds 2
Prognostic Implications in Your Case
Given the clinical scenario you described—45 minutes of CPR, 6 mg total epinephrine, and fixed pupils—the prognosis is extremely poor:
- Fixed and dilated pupils during CPR are frequently caused by epinephrine administration and should not be considered an absolute contraindication to resuscitation 2
- However, after 45 minutes of resuscitation without ROSC, the metabolic phase of cardiac arrest has been reached, characterized by severe tissue hypoxia and acidosis 5
- Standard CPR produces only 30-40% of normal cardiac output, with myocardial flow substantially lower at 10-30% 5
Management Priorities
Continue high-quality CPR while aggressively searching for reversible causes (the H's and T's) 2:
- Hypovolemia, Hypoxia, Hydrogen ion (acidosis), Hypo/hyperkalemia, Hypothermia 2
- Toxins, Tamponade, Tension pneumothorax, Thrombosis (coronary/pulmonary), Trauma 2
For the initial shockable VF rhythm that converted to PEA, this represents a particularly poor prognostic sign:
- Secondary VF/VT (developing during resuscitation from PEA/asystole) is associated with lower rates of ROSC and survival compared to initial VF/VT 1
- More frequent epinephrine administration is associated with development of secondary arrhythmias 6
Critical Pitfall to Avoid
Do not mistake audible heart sounds for return of spontaneous circulation. The definitive assessment requires:
- Palpable pulse (carotid or femoral) 1
- Measurable blood pressure 2
- Ideally, confirmation with arterial line monitoring or ultrasound visualization of adequate cardiac contractility 2, 4
The presence of heart sounds in your patient indicated some degree of mechanical cardiac activity but clearly insufficient to generate perfusion, confirming true PEA arrest despite the audible sounds.