4.1 Cardiovascular Disorders & Cardiac Emergencies

Cardiovascular Disorders & Cardiac Emergencies

Cardiovascular pathology represents one of the leading causes of acute clinical deterioration and hospital admission worldwide. For the professional registered nurse, rapid assessment, accurate interpretation of hemodynamic profiles, prompt recognition of electrocardiographic rhythms, and decisive pharmacological intervention are critical competencies required to preserve myocardial tissue and prevent cardiac arrest.

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Coronary Artery Disease & Acute Coronary Syndromes (ACS)

Coronary artery disease (CAD) develops through progressive atherogenesis, beginning with endothelial injury, subendothelial accumulation of low-density lipoproteins (LDL), foam cell formation, and fibrous cap proliferation. Acute Coronary Syndrome (ACS) represents an umbrella term for a continuum of myocardial ischemia and necrosis triggered by rupture or erosion of an unstable atherosclerotic plaque with secondary platelet aggregation and thrombus formation.

The ACS Spectrum

• Unstable Angina (UA): New-onset chest pain, pain occurring at rest or with minimal exertion, or crescendo pain increasing in frequency, duration, or severity. Electrocardiography (ECG) may show transient ST-segment depression, T-wave inversion, or be completely normal. Cardiac biomarkers (troponins) remain negative, indicating ischemia without measurable myocardial cell death.
• Non-ST-Segment Elevation Myocardial Infarction (NSTEMI): Acute myocardial injury with a rise or fall in troponin and evidence of ischemia, without persistent diagnostic ST elevation. ECG may show ST depression, T-wave inversion or no diagnostic change; ECG category alone does not establish coronary anatomy.
• ST-Segment Elevation Myocardial Infarction (STEMI): Acute coronary occlusion commonly produces persistent ST elevation in at least two contiguous leads. At the J point, use ≥1 mm except in V2–V3: ≥2 mm in men aged ≥40, ≥2.5 mm in younger men, and ≥1.5 mm in women. New LBBB alone is not diagnostic. Activate urgent reperfusion for a compatible presentation and diagnostic ECG; do not wait for troponin results.

Diagnostic Cardiac Biomarkers

Serial measurement of cardiac biomarkers is essential to differentiate unstable angina from myocardial infarction, track infarct progression, and detect reinfarction.

Acute Nursing Interventions: The MONA / OMNA Protocol

When a patient presents with acute ischemic chest pain, obtain a diagnostic 12-lead ECG within 10 minutes of first medical contact and initiate immediate pharmacological and supportive interventions:

1. Oxygen: Administer supplemental oxygen ONLY if SpO2 is < 90%, or if the patient exhibits signs of acute respiratory distress, cyanosis, or shock. Critical Practice Alert: Routine hyperoxia in normoxemic patients causes coronary artery vasoconstriction, increases reactive oxygen species, and paradoxically worsens myocardial infarct size.
2. Aspirin: Administer 162 to 325 mg of non-enteric coated chewable aspirin immediately. Chewing facilitates rapid buccal and gastric mucosal absorption. Aspirin irreversibly inhibits platelet cyclooxygenase-1 (COX-1), blocking thromboxane A2 synthesis for the lifespan of the platelet (7 to 10 days).
3. Nitroglycerin: Administer 0.4 mg sublingually every 5 minutes up to a maximum of 3 doses, provided systolic blood pressure remains >= 90 mmHg and heart rate is 50 to 100 bpm. Nitroglycerin promotes systemic venous vasodilation, decreasing venous return (preload) and reducing myocardial wall tension and oxygen demand, while dilating epicardial coronary collaterals.
   • Strict Contraindications: Concurrent use of phosphodiesterase-5 (PDE-5) inhibitors (e.g., sildenafil or vardenafil within the prior 24 hours, or tadalafil within the prior 48 hours) due to the risk of profound, irreversible, life-threatening hypotension; severe bradycardia (< 50 bpm) or severe tachycardia (> 100 bpm); and suspected right ventricular (RV) infarction.
   • Right Ventricular Infarction Alert: RV infarction occurs in approximately 30% to 50% of inferior wall STEMIs (right coronary artery occlusion; leads II, III, aVF). The RV is preload-dependent; nitrates and morphine decrease venous return and trigger precipitous hemodynamic collapse. RV infarction presents clinically with the triad of hypotension, clear lung fields on auscultation, and elevated jugular venous distention (JVD). Confirmation requires right-sided precordial leads (V4R elevation >= 1 mm). Urgent reperfusion is essential. If hypotensive with low or normal filling pressure and no congestion, give a cautious crystalloid challenge (e.g., 250 mL), reassess perfusion and lung/JVP findings, and avoid excessive volume loading.
4. Morphine Sulfate: Administer 2 to 4 mg IV push every 5 to 15 minutes for refractory chest discomfort unrelieved by nitroglycerin. Morphine provides potent analgesia, reduces sympathetic tone, and causes mild venodilation. Closely monitor respiratory rate, level of consciousness, and blood pressure.
5. P2Y12 Antiplatelet Inhibitor: Administer a loading dose of an oral P2Y12 receptor antagonist (clopidogrel 300 to 600 mg, ticagrelor 180 mg, or prasugrel 60 mg) in coordination with the cardiology team.
6. Anticoagulation: Initiate parenteral anticoagulation (unfractionated heparin [UFH] bolus and titration, or low-molecular-weight heparin [enoxaparin]) to prevent propagation of the intracoronary thrombus.

Reperfusion Standards: Door-to-Balloon & Door-to-Needle

For confirmed STEMI, time to coronary reperfusion directly correlates with myocardial salvage and clinical survival:

• Percutaneous Coronary Intervention (PCI): Preferred reperfusion for STEMI. Target first medical contact-to-device activation <= 90 minutes, or <= 120 minutes when hospital transfer is needed. Persistent ischemia, shock or life-threatening arrhythmias require urgent revascularization assessment even after a late presentation.
• Fibrinolytic Therapy: For STEMI with symptom onset < 12 hours, use fibrinolysis when anticipated first medical contact-to-PCI device time exceeds 120 minutes and contraindications are absent. Screen for active bleeding, prior intracranial hemorrhage, recent ischemic stroke and intracranial lesions. Target door-to-needle <= 30 minutes; agents include alteplase, tenecteplase and reteplase. Arrange immediate transfer to a PCI center after treatment.

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Heart Failure: Hemodynamic Profiles & Clinical Staging

Heart failure (HF) is a complex clinical syndrome resulting from structural or functional impairment of ventricular filling or blood ejection. Using AHA/ACC/HFSA ejection-fraction categories: Heart Failure with Reduced Ejection Fraction (HFrEF; systolic failure with EF <= 40%) and Heart Failure with Preserved Ejection Fraction (HFpEF; diastolic failure with EF >= 50% characterized by stiff, non-compliant ventricles).

Left-Sided vs. Right-Sided Heart Failure

Diagnostic Biomarkers: BNP & NT-proBNP

Ventricular wall stress stimulates release of proBNP, which is cleaved into biologically active BNP and inactive NT-proBNP. BNP promotes natriuresis, diuresis and vasodilation, counteracting RAAS activation. Both BNP and NT-proBNP are useful markers of cardiac wall stress.

• BNP: Normal value is < 100 pg/mL. Levels > 400 pg/mL strongly indicate acute decompensated heart failure as the primary cause of acute dyspnea, distinguishing it from pulmonary conditions such as COPD exacerbation or pneumonia.
• NT-proBNP: Normal value is < 300 pg/mL. Age-stratified diagnostic thresholds for acute heart failure: > 450 pg/mL for age < 50; > 900 pg/mL for age 50 to 75; > 1,800 pg/mL for age > 75.

New York Heart Association (NYHA) Functional Classification

• Class I (Mild): No limitation of physical activity. Ordinary physical activity does not cause undue fatigue, palpitation, or dyspnea.
• Class II (Mild): Slight limitation of physical activity. Comfortable at rest, but ordinary physical activity results in fatigue, palpitation, or dyspnea.
• Class III (Moderate): Marked limitation of physical activity. Comfortable at rest, but less than ordinary activity causes fatigue, palpitation, or dyspnea.
• Class IV (Severe): Inability to carry out any physical activity without discomfort. Symptoms of cardiac insufficiency are present even at rest; any physical exertion increases discomfort.

Pharmacotherapy & Nursing Considerations in Heart Failure

1. ACE Inhibitors (e.g., Lisinopril, Enalapril) & ARBs (e.g., Losartan, Valsartan): Cornerstone neurohormonal blockade that inhibits the renin-angiotensin system, promotes arterial vasodilation, decreases afterload, and reduces ventricular remodeling. Nursing priority: Monitor blood pressure, serum creatinine, and potassium (risk of hyperkalemia). Assess for persistent dry cough (ACE inhibitors) and life-threatening angioedema.
2. Angiotensin Receptor-Neprilysin Inhibitors (ARNI; Sacubitril/Valsartan): Combines neprilysin inhibition (preventing degradation of natriuretic peptides) with angiotensin II receptor blockade. Safety Rule: When transitioning from an ACE inhibitor to an ARNI, enforce a mandatory 36-hour washout period to eliminate the risk of severe angioedema.
3. Beta-Adrenergic Blockers (Carvedilol, Metoprolol Succinate, Bisoprolol): Inhibit chronic sympathetic nervous system toxicity, slow heart rate, reduce ventricular wall stress, and improve long-term survival. Nursing priority: Initiate only when the patient is clinically stable and euvolemic; monitor for initial transient fluid retention, bradycardia (hold for apical HR < 60 bpm), and hypotension (hold for SBP < 90 mmHg).
4. Loop Diuretics (Furosemide, Bumetanide): Primary agents for symptomatic volume overload; act on the thick ascending loop of Henle to inhibit sodium and chloride reabsorption. Nursing priority: Administer IV push slowly (<= 20 mg/min for furosemide) to prevent transient or permanent ototoxicity. Monitor for severe hypokalemia, hypomagnesemia, and prerenal azotemia.
5. Aldosterone Receptor Antagonists (Spironolactone, Eplerenone): Potassium-sparing diuretics that block aldosterone receptors, attenuating myocardial fibrosis. Nursing priority: Monitor serum potassium closely; contraindicated in severe renal impairment (eGFR < 30 mL/min) or hyperkalemia (K+ > 5.0 mEq/L).
6. Cardiac Glycoside (Digoxin): Positive inotropic agent that inhibits myocardial cell membrane Na+/K+-ATPase, increasing intracellular calcium and enhancing myocardial contractility, while exerting negative chronotropic action via vagal stimulation to slow AV nodal conduction.
   • Therapeutic Serum Level: 0.5 to 2.0 ng/mL (target range for heart failure is 0.5 to 0.9 ng/mL to minimize toxicity risk).
   • Clinical Signs of Digoxin Toxicity: Early gastrointestinal symptoms include anorexia, nausea, vomiting, diarrhea, and abdominal pain. Neurological signs include fatigue, headache, confusion, and drowsiness. Visual disturbances include blurred vision, photophobia, and classic yellow-green halos around lights or altered color perception (xanthopsia). Cardiac manifestations include sinus bradycardia, sinoatrial block, premature ventricular contractions (bigeminy/trigeminy), junctional rhythms, and life-threatening ventricular tachycardia or ventricular fibrillation.
   • Nursing Administration Rule: Always auscultate the apical pulse for a full 60 seconds prior to administration. Withhold the dose and immediately notify the prescriber if the apical heart rate is < 60 bpm in an adult (< 70 bpm in an older child, or < 90 to 110 bpm in an infant).
   • Electrolyte Influence: Hypokalemia (< 3.5 mEq/L), hypomagnesemia (< 1.8 mg/dL), and hypercalcemia markedly potentiate digoxin toxicity because potassium and digoxin compete for the same binding site on the Na+/K+-ATPase enzyme. When potassium is low, more digoxin molecules bind to the enzyme, exaggerating pharmacological and toxic effects even at normal serum digoxin levels.
   • Antidote: Digoxin Immune Fab (Digibind / DigiFab) is indicated for severe life-threatening dysrhythmias, severe hyperkalemia (> 5.0 mEq/L) associated with digitalis intoxication, or acute massive ingestion (> 10 mg in adults).

Daily Weight & Discharge Self-Care Teaching

Instruct heart failure patients to record daily body weights each morning immediately after voiding, wearing identical clothing, on the same calibrated scale, prior to eating breakfast. Educate the patient to notify their healthcare provider immediately if they experience a weight gain of > 2 to 3 pounds (0.9 to 1.4 kg) in a single day or > 5 pounds (2.3 kg) in one week, signaling acute fluid retention prior to the onset of overt dyspnea.

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Systemic Hypertension & Hypertensive Crisis

Systemic hypertension is defined by sustained elevation of systemic arterial pressure, leading to progressive microvascular and macrovascular target-organ damage in the brain, heart, kidneys, and eyes.

Blood Pressure Classification (ACC/AHA Guidelines)

• Normal: Systolic < 120 mmHg AND Diastolic < 80 mmHg.
• Elevated: Systolic 120 to 129 mmHg AND Diastolic < 80 mmHg.
• Stage 1 Hypertension: Systolic 130 to 139 mmHg OR Diastolic 80 to 89 mmHg.
• Stage 2 Hypertension: Systolic >= 140 mmHg OR Diastolic >= 90 mmHg.

Hypertensive Crisis: Urgency vs. Emergency

A hypertensive crisis is defined as an acute, severe elevation in blood pressure, typically Systolic BP > 180 mmHg and/or Diastolic BP > 120 mmHg.

The MAP Calculation & Autoregulation Principle

Mean Arterial Pressure (MAP) represents the average perfusion pressure delivered to vital organ capillary beds throughout the cardiac cycle:

$\text{MAP} = \frac{\text{Systolic BP} + 2(\text{Diastolic BP})}{3}$

Critical Pathophysiological Alert: Chronic hypertension shifts cerebral autoregulation, so precipitous BP reduction can cause organ hypoperfusion. Acute aortic dissection requires rapid SBP reduction to <120 mmHg during the first hour with close monitoring. It is not the only condition requiring a specific BP strategy; follow the applicable stroke or obstetric protocol when relevant.

Lifestyle Modifications & The DASH Diet

First-line non-pharmacological interventions for hypertension include:

• DASH (Dietary Approaches to Stop Hypertension) Eating Plan: Diets high in fruits, vegetables, whole grains, and low-fat dairy products, with reduced saturated and total fat.
• Dietary Sodium Restriction: Limit daily sodium intake to < 2,300 mg/day, with an optimal target of < 1,500 mg/day for individuals with established hypertension, older adults, and those of African descent.
• Physical Activity: Engage in at least 150 minutes per week of moderate-intensity aerobic exercise (brisk walking, swimming, cycling).
• Weight Reduction: Maintain a body mass index (BMI) between 18.5 and 24.9 kg/m²; each 1 kg loss yields an expected systolic blood pressure reduction of approximately 1 mmHg.
• Alcohol Moderation: Limit consumption to <= 2 standard drinks daily for men and <= 1 standard drink daily for women.

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Cardiac Dysrhythmias & ACLS Resuscitation Principles

Cardiac dysrhythmias arise from abnormalities in impulse generation (enhanced automaticity, triggered activity) or impulse conduction (reentry circuits, conduction blocks). Nurses must instantly differentiate stable rhythms from unstable rhythms and execute Advanced Cardiovascular Life Support (ACLS) protocols.

Atrial Fibrillation (AFib) & Atrial Flutter

Supraventricular tachydysrhythmias originating in the atria compromise cardiac output by impairing ventricular filling time and eliminating coordinated atrial systole.

Atrial Fibrillation (AFib)

• Pathophysiology: Characterized by rapid, disorganized electrical impulses originating from multiple micro-reentrant circuits and ectopic foci within the atria, predominantly localized around the sleeves of the pulmonary veins. Atrial depolarization rates reach 350 to 600 bpm, causing chaotic atrial quivering, mechanical standstill, and complete loss of the "atrial kick" (which normally contributes 20% to 30% of end-diastolic ventricular filling volume).
• ECG Characteristics: Absence of distinct P waves, replaced by irregular, undulating fibrillatory ('f') waves; an irregularly irregular ventricular rhythm (no discernible pattern to R-R intervals); and typically normal narrow QRS complexes (< 0.12 seconds) unless aberrancy or pre-existing bundle branch block is present. Ventricular rate varies: Controlled AF (ventricular rate < 100 bpm) versus AF with Rapid Ventricular Response (RVR; ventricular rate > 100 bpm).

Atrial Flutter

• Pathophysiology: Caused by a single, continuous macro-reentrant electrical circuit, most commonly rotating in a counterclockwise direction around the tricuspid valve annulus within the right atrium.
• ECG Characteristics: Regular atrial rate typically 250 to 350 bpm (characteristically ~300 bpm); classic, uniform sawtooth flutter ('F') waves seen most prominently in inferior leads (II, III, aVF) and V1; no flat isoelectric baseline between flutter waves; and fixed or variable AV nodal conduction block (most commonly 2:1 block resulting in a regular ventricular rate of ~150 bpm, 3:1 block at ~100 bpm, or 4:1 block at ~75 bpm).

Thromboembolic Risk & Anticoagulation Management

In both AFib and atrial flutter, blood stasis within the fibrillating or fluttering atria—specifically within the trabeculated left atrial appendage (LAA)—rapidly promotes platelet aggregation and fibrin thrombus formation. If sinus rhythm is restored or ventricular contractions fluctuate, fragments of the mural thrombus can dislodge into the systemic arterial circulation, producing ischemic stroke or peripheral arterial occlusion:

• Stroke Risk Stratification (CHA2DS2-VASc): Used to determine long-term systemic anticoagulation indications:
  • Congestive heart failure / LV dysfunction (1 point)
  • Hypertension (1 point)
  • Age >= 75 years (2 points)
  • Diabetes mellitus (1 point)
  • Stroke / TIA / systemic thromboembolism history (2 points)
  • Vascular disease (prior MI, peripheral arterial disease, aortic plaque) (1 point)
  • Age 65 to 74 years (1 point)
  • Sex category female (1 point)
• Anticoagulation Indications: Oral anticoagulation is strongly recommended for patients with a score >= 2 in men or >= 3 in women, and considered for a score of 1 in men or 2 in women.
• Pharmacological Options:
  • Direct Oral Anticoagulants (DOACs; Apixaban, Rivaroxaban, Dabigatran, Edoxaban): First-line agents for non-valvular AFib due to superior safety profiles, lower rates of fatal intracranial hemorrhage, rapid onset/offset, and lack of routine coagulation monitoring.
  • Vitamin K Antagonist (Warfarin): Mandatory for patients with mechanical prosthetic heart valves or moderate-to-severe mitral stenosis. Requires routine INR monitoring, maintaining a target INR of 2.0 to 3.0 (or 2.5 to 3.5 for mechanical mitral valves).

Rate vs. Rhythm Control Strategies

• Ventricular Rate Control: The primary initial strategy for hemodynamically stable patients. Controls the rapid ventricular response to allow adequate diastolic filling time and reduce myocardial oxygen demand:
  • Beta-Adrenergic Blockers: Intravenous or oral metoprolol, atenolol, or esmolol.
  • Non-Dihydropyridine Calcium Channel Blockers: Intravenous or oral diltiazem or verapamil (negative inotropes and dromotropes; avoid in patients with acute decompensated HFrEF).
  • Cardiac Glycosides: Digoxin (useful in sedentary patients or concurrent systolic heart failure; slow onset).
• Rhythm Control: Restoration and maintenance of normal sinus rhythm:
  • Pharmacological Cardioversion: Antiarrhythmic infusions including Amiodarone (Class III), Flecainide or Propafenone (Class IC; contraindicated in structural heart disease/prior MI), or Sotalol.
  • Electrical Cardioversion: Synchronized direct current cardioversion.

Cardioversion Safety Rules: Elective vs. Emergency Protocols

Restoring coordinated atrial contraction in a patient with an existing left atrial thrombus can forcibly eject the clot into the systemic arterial tree, causing immediate embolic stroke. Nurses and clinicians must adhere strictly to evidence-based cardioversion safety protocols based on patient acuity and rhythm duration:

1. Elective Cardioversion in Hemodynamically Stable Patients:

   • Onset < 48 Hours: If atrial fibrillation or flutter is reliably documented to have started less than 48 hours ago in a hemodynamically stable patient, cardioversion may be undertaken early. Therapeutic anticoagulation (e.g., UFH, LMWH, or DOAC) should be initiated prior to conversion and continued for at least 4 weeks post-cardioversion.
   • Onset >= 48 Hours (or Unknown Duration): If the dysrhythmia has persisted for >= 48 hours or if the onset time is uncertain, elective cardioversion carries a high risk of thromboembolism. In stable patients, elective cardioversion is deferred until one of two rigorous safety strategies is fulfilled:
     • Strategy A (Continuous Anticoagulation): Therapeutic anticoagulation is administered continuously and verified for at least 3 consecutive weeks prior to cardioversion, and must be continued for at least 4 weeks post-cardioversion (regardless of baseline CHA2DS2-VASc score) because atrial mechanical function remains "stunned" and sluggish for several weeks after electrical conversion.
     • Strategy B (TEE-Guided Cardioversion): A Transesophageal Echocardiogram (TEE) is performed immediately prior to the planned cardioversion to directly visualize the left atrium and left atrial appendage and definitively rule out intracardiac thrombus. If no thrombus is present, cardioversion may proceed immediately, provided therapeutic anticoagulation is started prior to conversion and maintained for at least 4 weeks post-cardioversion. If a thrombus is identified, cardioversion is cancelled, and therapeutic anticoagulation must be continued for at least 3 to 4 weeks before repeat imaging.

2. CRITICAL UNSTABLE EMERGENCY EXCEPTION (AHA 2025 Adult ALS Guideline 18.1):

   • Hemodynamic Instability Definition: When atrial fibrillation or atrial flutter presents with rapid ventricular rate and produces acute hemodynamic instability, defined by:
     • Hypotension: Systolic blood pressure < 90 mmHg or mean arterial pressure < 65 mmHg with signs of hypoperfusion.
     • Acutely Altered Mental Status: Confusion, lethargy, encephalopathy, agitation.
     • Signs of Shock: Cool, clammy extremities, peripheral cyanosis, delayed capillary refill (> 3 seconds), oliguria.
     • Ischemic Chest Discomfort: Anginal pain or dynamic ST-segment changes indicative of acute myocardial ischemia.
     • Acute Pulmonary Edema / Decompensated Heart Failure: Bilateral pulmonary crackles, severe dyspnea, orthopnea, frothy sputum.
   • MANDATORY EMERGENCY INTERVENTION: IMMEDIATE SYNCHRONIZED ELECTRICAL CARDIOVERSION.
   • Zero-Delay Mandate: The resuscitation team MUST NOT DELAY cardioversion to await 3 weeks of anticoagulation or to obtain a TEE in a hemodynamically unstable patient. Hemodynamic collapse and impending cardiopulmonary arrest constitute an immediate threat to life that supersedes thromboembolic risk.
   • Concurrent Anticoagulation: Systemic parenteral anticoagulation (e.g., intravenous unfractionated heparin bolus) should be initiated as soon as feasible, but obtaining or administering anticoagulation must never delay the delivery of the life-saving electrical shock.
   • Technical Cardioversion Principles:
     • The defibrillator MUST BE IN SYNCHRONIZED (SYNC) MODE. The nurse or clinician must confirm that the monitor displays visible sync markers on each QRS complex (specifically on the peak of the R wave). Delivering an unsynchronized shock during the vulnerable relative refractory period (T wave) can trigger ventricular fibrillation (the R-on-T phenomenon).
     • AHA 2025 recommends initial synchronized biphasic energy of at least 200 J for atrial fibrillation; 200 J for atrial flutter is also reasonable. Increase energy after an unsuccessful shock according to the device and resuscitation protocol.
     • Administer procedural IV sedation and analgesia (e.g., midazolam, propofol, fentanyl) if the patient remains conscious and time permits, but do not withhold shock delivery if the patient is deteriorating precipitously.

Ventricular Dysrhythmias & Resuscitation Protocols

Ventricular dysrhythmias originate below the bifurcation of the bundle of His, producing wide, bizarre QRS complexes (>= 0.12 seconds) that represent inefficient ventricular mechanical contraction.

1. Ventricular Tachycardia (VT)

VT produces a rapid, wide-complex rhythm, typically 100 to 250 bpm. Monomorphic VT has similar QRS complexes and a regular rhythm; polymorphic VT has changing QRS morphology. Management depends on the rhythm, hemodynamic stability and presence of a pulse:

• Stable VT with a Pulse: Patient is conscious, alert, with adequate blood pressure and no chest pain or dyspnea. Management: Obtain a 12-lead ECG, administer oxygen if SpO2 < 90%, establish wide-bore IV access, and administer an antiarrhythmic infusion (e.g., Amiodarone 150 mg IV over 10 minutes, repeatable once, followed by maintenance infusion of 1 mg/min for 6 hours).
• Unstable VT with a Pulse: Hypotension, altered mental status, ischemic chest pain or acute pulmonary edema requires immediate electrical treatment. For monomorphic VT, use synchronized cardioversion (initial biphasic 100 J), confirming SYNC markers on each R wave to avoid an R-on-T shock. Give sedation if feasible without delaying treatment. For polymorphic VT, deliver an immediate high-energy unsynchronized shock because reliable synchronization is not possible.
• Pulseless VT: Patient is unresponsive, apneic, and pulseless. Treated identically to Ventricular Fibrillation.

2. Ventricular Fibrillation (VF)

Chaotic, disorganized electrical activity without coordinated mechanical contraction or cardiac output. The ECG displays coarse or fine undulations without discernible P waves, QRS complexes, or T waves. The patient undergoes immediate clinical collapse and functional cardiac arrest.

• Resuscitation Priorities:
  1. Call for help, activate the hospital resuscitation team / code blue, and initiate high-quality chest compressions immediately.
  2. Defibrillate Immediately: Deliver an unsynchronized high-energy shock (biphasic 120 to 200 J per manufacturer recommendation, or monophasic 360 J).
  3. Resume CPR immediately after the shock for 2 minutes (5 cycles of 30 compressions to 2 breaths) before re-checking rhythm or pulse.
  4. Pharmacotherapy: Administer Epinephrine 1 mg IV/IO every 3 to 5 minutes after the second defibrillation. Administer an antiarrhythmic: Amiodarone 300 mg IV/IO bolus after the third defibrillation, with a second dose of 150 mg IV/IO if VF persists (or Lidocaine 1 to 1.5 mg/kg initial bolus, then 0.5 to 0.75 mg/kg).

3. Asystole & Pulseless Electrical Activity (PEA)

• Asystole: Total absence of ventricular electrical activity (flatline). Must be verified in two contiguous ECG leads to confirm true asystole and rule out fine ventricular fibrillation or disconnected monitoring leads.
• Pulseless Electrical Activity (PEA): Presence of an organized or semi-organized electrical rhythm on the cardiac monitor (sinus rhythm, bradycardia, bundle branch block) in a patient with no palpable central pulse and absent perfusion.
• Absolute Non-Shockable Rule: Asystole and PEA are NON-SHOCKABLE rhythms. Defibrillation is strictly contraindicated because electrical shock causes direct myocardial injury, depletes cellular adenosine triphosphate (ATP), and parasympathetic tone increases without restoring conduction.
• Resuscitation Interventions: Continuous high-quality CPR; establish advanced airway with continuous capnography (target end-tidal CO2 [ETCO2] > 10 to 20 mmHg indicating effective compressions; a sudden sustained spike in ETCO2 >= 35 to 40 mmHg indicates Return of Spontaneous Circulation [ROSC]); administer Epinephrine 1 mg IV/IO every 3 to 5 minutes immediately upon establishing vascular access.

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

Resuscitation success in PEA and asystole requires aggressive identification and treatment of underlying reversible etiologies:

• Hypovolemia: Most common cause of PEA; rapid IV crystalloid infusion.
• Hypoxia: Ensure airway patency, 100% FiO2, effective bag-valve-mask ventilations.
• Hydrogen Ion (Acidosis): Provide high-quality CPR and effective ventilation while treating the cause. Do not routinely give sodium bicarbonate for cardiac-arrest acidosis; reserve it for a specific indication under the applicable resuscitation or toxicology protocol.
• Hypokalemia / Hyperkalemia: Administer IV calcium gluconate/chloride and insulin with 50% dextrose for severe hyperkalemia; administer controlled IV potassium for hypokalemia.
• Hypothermia: Initiate active internal and external rewarming techniques.
• Tension Pneumothorax: Immediate needle decompression (2nd intercostal space midclavicular line or 4th/5th intercostal space anterior axillary line) followed by tube thoracostomy.
• Tamponade (Cardiac): Immediate bedside pericardiocentesis.
• Toxins: Specific antidote administration (e.g., Naloxone for opioids, Flumazenil for benzodiazepines, Calcium/Glucagon for calcium/beta-blocker overdose, Digibind for digitalis).
• Thrombosis (Pulmonary): Emergency systemic thrombolytic therapy or catheter embolectomy.
• Thrombosis (Coronary): Emergent percutaneous coronary intervention following ROSC.