8 ECG and Resuscitation Case Practice

Assess the patient and ECG together

Interpret the tracing alongside the patient rather than in isolation. First determine responsiveness and whether a definite pulse is present. If there is no pulse, begin CPR and use the cardiac-arrest pathway; if a pulse is present, assess whether the rhythm is causing cardiopulmonary compromise.

For a rhythm strip or $12$-lead ECG, assess the rate, regularity, QRS width, atrial activity, and clinical effect. Determine whether R–R intervals are regular, regularly irregular, or irregularly irregular; whether P waves are present and consistently related to QRS complexes; and, when possible, measure the PR interval. A QRS is narrow when it is less than $0.12$ seconds and wide when it is at least $0.12$ seconds.

Look for hypotension, acutely altered mental status, shock, ischemic chest discomfort, or acute heart failure. These findings help determine whether a tachyarrhythmia is unstable. A monitor rhythm alone does not establish a pulse or prove adequate perfusion.

The first practical classification is pulseless versus pulse present. In cardiac arrest, distinguish shockable from nonshockable rhythms; with a pulse and tachyarrhythmia, distinguish stable from unstable. The patient's pulse, perfusion, and clinical condition guide the pathway.

Manage cardiac arrest

For cardiac arrest, begin CPR and attach a monitor or defibrillator. VF and pulseless VT are shockable; asystole and PEA are nonshockable. Defibrillate shockable arrest promptly, then resume CPR immediately for about $2$ minutes before briefly reassessing the rhythm. For biphasic defibrillation, follow the device manufacturer's energy recommendation; if it is unknown, use the maximum available setting.

Give epinephrine $1$ mg IV/IO every $3$–$5$ minutes during arrest. In VF or pulseless VT, the algorithm introduces epinephrine after initial defibrillation attempts. If VF or pulseless VT persists despite defibrillation, amiodarone or lidocaine may be considered. For asystole or PEA, give epinephrine as soon as feasible, continue CPR, and search for reversible causes; do not defibrillate these rhythms.

CPR delivery

Use compressions at $100$–$120$ per minute, at least $5$ cm deep, with full recoil and minimal interruptions. Avoid excessive ventilation. Without an advanced airway, use a compression-to-ventilation ratio of $30:2$. With an advanced airway, provide continuous compressions and one breath every $6$ seconds. Change compressors about every $2$ minutes or sooner if fatigued.

Reversible causes

For PEA or asystole, consider hypovolemia, hypoxia, hydrogen ion (acidosis), hypo- or hyperkalemia, hypothermia, tension pneumothorax, cardiac tamponade, toxins, pulmonary thrombosis, and coronary thrombosis. Treat suspected causes while maintaining CPR, and do not interrupt compressions for prolonged diagnostic procedures.

Treat tachyarrhythmia with a pulse

Assess whether the tachyarrhythmia is causing hypotension, acutely altered mental status, shock, ischemic chest discomfort, or acute heart failure. If it is, prepare for synchronized cardioversion. Sedate when feasible, but do not delay urgent treatment. Use synchronization when the patient has a pulse and the unstable rhythm can be synchronized. Polymorphic VT cannot be reliably synchronized; treat it as a shockable rhythm with an unsynchronized shock. Follow current device instructions and local protocol.

If the patient is stable, assess QRS width and regularity. A regular narrow-complex rhythm may be treated with vagal maneuvers and adenosine. The described algorithm lists adenosine $6$ mg as a rapid IV push followed by a flush, then $12$ mg if needed. For stable wide-complex tachycardia, use expert judgment, consider an antiarrhythmic infusion, and seek consultation. Adenosine is considered only for a regular, monomorphic wide-complex rhythm.

Case: unstable, regular narrow-complex tachycardia

A patient with a regular narrow-complex tachycardia at about $190$ per minute is diaphoretic and confused, with marked hypotension. This is an unstable tachyarrhythmia with a pulse. The regular narrow QRS may suggest supraventricular tachycardia, but instability guides immediate treatment.

Support airway and breathing, monitor, and obtain IV access if doing so does not delay treatment. Prepare synchronized cardioversion; sedate if feasible and safe, but do not delay cardioversion in a deteriorating patient. Adenosine may be considered in an appropriate setting for a regular, narrow rhythm, but it should not replace urgent cardioversion if instability persists. Confirm synchronization before delivering the shock.

Case: stable, regular wide-complex tachycardia

An alert patient has a palpable pulse and currently maintained blood pressure. The ECG shows regular, monomorphic wide-complex tachycardia at $160$ per minute. Ventricular tachycardia is an important possibility; do not assume a wide rhythm is benign or that it is supraventricular with aberrancy.

Continue close monitoring, obtain a $12$-lead ECG if available, establish IV access, and seek expert consultation. Follow the stable wide-QRS pathway and consider an antiarrhythmic infusion. Adenosine is an option only if the rhythm is regular and monomorphic. Recheck stability while preparing treatment; if the patient becomes unstable, use synchronized cardioversion for a pulse-present rhythm.

Respond to symptomatic bradycardia

Treat the patient's perfusion, not a rate threshold alone. Bradycardia is commonly below $50$ per minute, but the key question is whether it is causing cardiopulmonary compromise. Support airway and breathing, monitor, obtain a $12$-lead ECG when feasible, and address reversible causes.

For persistent symptomatic bradycardia, the described algorithm lists atropine $1$ mg IV, repeated every $3$–$5$ minutes to a maximum total of $3$ mg. If it is ineffective, use transcutaneous pacing and/or a dopamine or epinephrine infusion; consider expert consultation and transvenous pacing. Do not let medication attempts delay preparation for pacing when the patient is deteriorating or high-grade block is suspected.

Case: symptomatic bradycardia with suspected high-grade block

A patient with dizziness and chest discomfort has a heart rate of $34$ per minute, hypotension, and P waves that are not consistently conducted to QRS complexes. This is symptomatic bradycardia with suspected high-grade AV block and cardiopulmonary compromise.

Support airway and breathing, attach a monitor, and obtain IV access and a $12$-lead ECG if feasible. Prepare transcutaneous pacing promptly. Atropine is included in the bradycardia pathway; if the patient does not respond or is deteriorating, proceed to pacing and/or an epinephrine or dopamine infusion while arranging expert support and considering transvenous pacing. Consider reversible contributors such as ischemia, hypoxia, medications, or electrolyte abnormalities. Prepare pacing equipment early and avoid allowing serial medication attempts to delay support for a worsening patient.

Continue care after ROSC

After CPR and defibrillation, a patient regains a pulse and begins moving but does not follow commands. ROSC changes the immediate priorities; it does not end resuscitation care.

Manage airway, oxygenation, ventilation, and hemodynamics. Obtain a $12$-lead ECG as soon as feasible, evaluate the cause of arrest and complications of resuscitation, and arrange ongoing critical care. Evaluate for cardiac or other emergency interventions as indicated.

For adults after ROSC, the described targets are SpO₂ of $90\%$–$98\%$ or PaO₂ of $60$–$105$ mm Hg, PaCO₂ of $35$–$45$ mm Hg, and a minimum MAP of $65$ mm Hg. If the patient remains unresponsive to verbal commands, use a deliberate, protocolized temperature-control strategy and maintain it for at least $36$ hours.

Announce ROSC, transition team roles, and begin post-arrest stabilization. Investigate the likely cause rather than treating the return of a pulse as the endpoint.

Debrief to improve team practice

A brief, structured debrief helps convert an event into safer future practice. Begin with a shared timeline covering recognition, first compressions, rhythm checks, shocks, medications, and ROSC or a termination decision.

Discuss what went well and which actions should be repeated. Identify what was difficult or delayed, focusing on observable system or communication issues rather than personal blame. Check whether roles and closed-loop communication were clear: requests should be acknowledged, performed, and reported back.

Review whether clinical decisions matched the rhythm and patient, including pulse status, shockability or stability, CPR timing, and treatment of reversible causes. Choose one specific improvement and assign an action, owner, and follow-up when appropriate. Use approved cognitive aids and local protocols during real resuscitations; cognitive aids are recommended for healthcare professionals during resuscitation events.

• High-quality CPR