6 Cardiac Emergencies

Recognize deterioration and call for help

Cardiac emergencies can progress rapidly to irreversible organ injury or death. Immediate priorities are to recognize cardiac arrest or poor perfusion, activate emergency help, support oxygenation and circulation, and treat the rhythm or underlying cause without delay. These adult response principles follow current American Heart Association guidance; trained responders should follow local protocols and current resuscitation algorithms.

Rapid assessment and escalation

Assess responsiveness, breathing, circulation, and signs of poor perfusion. Warning signs include altered mental status, fainting, hypotension, cool or mottled skin, weak pulses, chest discomfort, and acute shortness of breath.

Call emergency services or activate the facility response team early. For a patient with a pulse, support the airway and breathing, give oxygen when hypoxemic, attach a cardiac monitor and defibrillator, obtain IV or IO access, and acquire a 12-lead ECG when feasible. Evaluate and treat reversible causes while stabilizing the patient.

A heart rate alone does not determine urgency. A rhythm is especially concerning when it causes hypotension, altered mental status, shock, ischemic chest discomfort, or acute heart failure.

Cardiac arrest and CPR

Suspect cardiac arrest when a person is unresponsive and not breathing normally; gasping is not normal breathing. A trained healthcare professional checks for a pulse for no more than 10 seconds. If no definite pulse is felt, start CPR and activate the emergency response system. A lone rescuer should call for help and begin CPR, using an AED as soon as one is available.

Provide high-quality CPR by compressing at 100 to 120 times per minute, allowing full chest recoil, minimizing pauses, and avoiding excessive ventilation. Without an advanced airway, use cycles of 30 compressions and 2 breaths. Follow AED prompts; if a shock is advised, deliver it and immediately resume compressions.

Arrest rhythms and care after ROSC

For trained advanced responders, cardiac-arrest rhythms are divided into shockable and nonshockable groups.

• Shockable rhythms: Ventricular fibrillation (VF) and pulseless ventricular tachycardia (pVT) require prompt defibrillation. Resume CPR immediately for about 2 minutes, then recheck the rhythm. Continue CPR, shocks, and indicated medications according to the algorithm.

• Nonshockable rhythms: Pulseless electrical activity (PEA) and asystole require continued CPR, indicated medications, and a rapid search for reversible causes. Defibrillation is not indicated unless the rhythm changes to VF or pVT.

Minimize interruptions in compressions. After return of spontaneous circulation (ROSC), stabilize airway, oxygenation, ventilation, and blood pressure; investigate the cause and arrange ongoing critical care.

Shock and perfusion

Shock is inadequate tissue perfusion. It may present with hypotension, confusion, cool or clammy skin, weak pulses, delayed capillary refill, or reduced urine output, but hypotension may be absent early. Activate emergency support, maintain a patent airway, support breathing, monitor closely, and establish vascular access. Treat the cause rather than relying on blood pressure alone.

Cardiogenic shock results from cardiac pump failure, often after myocardial infarction, and can coexist with other forms of shock. Seek urgent expert and hospital-level care, identify the cause, and restore perfusion without delaying definitive treatment. Fluids and vasoactive medicines require clinical judgment: large, routine fluid boluses may worsen pulmonary congestion in pump failure.

When shock follows cardiac arrest, the post-ROSC pathway targets a mean arterial pressure (MAP) of at least 65 mm Hg and emphasizes treatment of the underlying cause.

For first-aid responders, keep an alert person with signs of shock lying supine while help is on the way. If the person becomes less alert or is vomiting, protect the airway and use a recovery position if appropriate. Do not delay emergency care.

Unstable tachycardia with a pulse

A persistent tachyarrhythmia causing hypotension, altered mental status, shock, ischemic chest discomfort, or acute heart failure requires urgent treatment. Prepare for synchronized cardioversion; sedate when feasible without delaying treatment. Polymorphic ventricular tachycardia cannot be reliably synchronized and requires immediate unsynchronized defibrillation.

If the patient is stable, assess the rhythm and cause and use the appropriate rhythm-specific pathway. Medication choices depend on the rhythm and clinical context.

Unstable bradycardia with a pulse

Treat bradycardia when it is associated with hemodynamic compromise, not merely because the rate is low. Support airway and breathing, monitor the patient, establish access, and correct reversible causes such as ischemia, hypoxia, electrolyte disturbance, or medication effects.

For adults with bradycardia and hemodynamic compromise, atropine is reasonable. If it is ineffective, use transcutaneous pacing or an intravenous rate-accelerating infusion while preparing for temporary transvenous pacing when needed.