SA node → AV node → Bundle of His → Bundle Branches → Purkinje fibers. If SA fails, each lower site takes over at a slower rate.
Coronary Vessels
| Vessel | Abbreviation | Territory Supplied |
|---|---|---|
| Right Coronary Artery | RCA | RV, inferior LV, SA node (~60%), AV node (~90%) |
| Left Anterior Descending | LAD | Anterior LV, septum (V1–V4), bundle branches, apex |
| Left Circumflex | LCx | Lateral LV (I, aVL, V5–V6), posterior wall |
| Left Main Coronary | LMCA | Supplies BOTH LAD and LCx — occlusion = "widow maker" |
| Posterior Descending | PDA | Inferior wall — from RCA (85%) or LCx (15%) |
NREMT KEY: Inferior MI (II, III, aVF) = RCA until proven otherwise. Always get V4R to check for RV involvement BEFORE giving nitrates.
Conduction System — In Order
| Structure | Normal Rate | Function |
|---|---|---|
| SA Node | 60–100 bpm | Initiates impulse — P wave on EKG |
| AV Node | 40–60 bpm | Delays impulse 0.12–0.20 sec (PR interval); gate between atria & ventricles |
| Bundle of His | — | Relays impulse to bundle branches |
| Bundle Branches (R & L) | — | Carry impulse to ventricles — bundle branch blocks arise here |
| Purkinje Fibers | 20–40 bpm | Final distribution to ventricular myocardium → QRS complex |
EKG Waveform Breakdown
| Waveform | Represents | Normal Value |
|---|---|---|
| P wave | Atrial depolarization | <0.12 sec, upright in II, inverted in aVR |
| PR interval | SA-to-AV conduction time | 0.12–0.20 sec (3–5 small boxes) |
| QRS complex | Ventricular depolarization | <0.12 sec narrow; ≥0.12 = wide (BBB or VT) |
| ST segment | Early ventricular repolarization | Isoelectric; elevation = injury; depression = ischemia |
| T wave | Ventricular repolarization | Upright most leads; inverted = ischemia; peaked = hyperkalemia |
| QT interval | Total ventricular depol + repol | 0.36–0.44 sec; prolonged → Torsades risk |
| U wave | Purkinje repolarization | Small positive after T; prominent = hypokalemia |
A systematic approach prevents missed findings and builds exam confidence. Never skip steps — even when pressed for time.
Step 1 — Rate Methods
| Method | How To Use | Best For |
|---|---|---|
| 1500 Method | Count small boxes between R-R; divide into 1500 | Regular rhythms — most accurate |
| 300 Method | Count large boxes between R-R; divide into 300 | Regular rhythms — quick |
| 6-Second Strip | Count QRS in 6-sec strip × 10 | Irregular rhythms (AF) |
| Quick Ladder | 1 box=300, 2=150, 3=100, 4=75, 5=60, 6=50 | Memorize for rapid reading |
Step 2 — Rhythm Assessment
- Regular or irregular? P before every QRS? QRS after every P?
- Same P wave morphology every beat?
- Regularly irregular = pattern (e.g., Wenckebach 2° AVB Type I)
- Irregularly irregular = no pattern — pathognomonic of atrial fibrillation
Step 3 — QRS Width
WIDE QRS (≥0.12 sec) = VT UNTIL PROVEN OTHERWISE. Treat accordingly. Narrow (<0.12 sec) = supraventricular origin.
Step 4 — Axis (Lead I vs aVF)
| Axis | Lead I | aVF | Clinical Clue |
|---|---|---|---|
| Normal (−30° to +90°) | ↑ Positive | ↑ Positive | Normal conduction |
| Left Axis Deviation (<−30°) | ↑ Positive | ↓ Negative | LVH, LBBB, inferior MI, LAFB |
| Right Axis Deviation (>+90°) | ↓ Negative | ↑ Positive | RVH, lateral MI, RBBB, pulm HTN |
| Extreme/Indeterminate | ↓ Negative | ↓ Negative | VT, severe disease |
Step 5 & 6 — Intervals & ST/T Changes
| Finding | Meaning |
|---|---|
| PR >0.20 sec | 1st degree AV block |
| PR progressively lengthens → dropped QRS | Mobitz I (Wenckebach) — 2nd degree AVB Type I |
| Constant PR → sudden dropped QRS | Mobitz II — dangerous, infranodal |
| P and QRS march independently | 3rd degree (complete) AV block |
| ST elevation ≥1mm limb / ≥2mm precordial | STEMI — acute injury, occlusion |
| ST depression | Ischemia, NSTEMI, RV strain |
| Hyperacute T waves (tall, broad, symmetric) | Very early STEMI — before ST elevates |
| QTc >0.44s (M) / >0.46s (F) | Prolonged QT → Torsades de Pointes risk |
| Peaked "tented" T waves | Hyperkalemia |
| Prominent U waves | Hypokalemia |
Contiguous lead groupings tell you which vessel is occluded and where to look for reciprocal changes.
Territory Reference Table
| Wall / Region | Leads | Artery | Reciprocal In |
|---|---|---|---|
| Inferior | II, III, aVF | RCA (85%) / LCx (15%) | I, aVL |
| High Lateral | I, aVL | LCx or Diagonal (D1) | II, III, aVF |
| Anterior | V3, V4 | LAD | None reliable |
| Septal | V1, V2 | LAD (septal perforators) | None reliable |
| Low Lateral | V5, V6 | LCx or Diagonal | None reliable |
| Right Ventricle | V4R (right-sided) | Proximal RCA | Diagnose with right leads only |
| Posterior | V7–V9 (or reciprocal V1–V3) | RCA or LCx | ST depression + tall R in V1–V3 |
| Anterolateral | V1–V6 + I, aVL | LAD + LCx or LMCA | II, III, aVF |
Critical STEMI Patterns — Do Not Miss
- INFERIOR STEMI (II, III, aVF): ALWAYS get right-sided leads (V4R) before giving nitrates — RV infarct causes severe nitrate-induced hypotension
- RV INFARCT signs: Inferior STEMI + hypotension + clear lungs + JVD (Kussmaul sign) → fluids carefully, NO nitrates, NO preload reducers
- POSTERIOR MI: ST depression V1–V3 + tall wide R waves in V1 (mirror image) → confirm with V7–V9 (posterior leads show elevation)
- LBBB + chest pain: New/presumably new LBBB = STEMI equivalent; activate PCI pathway (Sgarbossa criteria)
- WELLENS SYNDROME: Deeply inverted or biphasic T waves in V2–V3 during PAIN-FREE interval = critical LAD stenosis — DO NOT stress test
- DE WINTER T WAVES: ST depression at J-point + tall symmetric T waves precordial = LAD occlusion equivalent (no elevation but needs PCI)
- HYPERACUTE T WAVES: Earliest STEMI change — tall, broad, asymmetric T waves before ST elevates; easy to miss
- STEMI MIMICS: LBBB, LVH, early repolarization, Brugada, pericarditis (saddle-shaped diffuse elevation + PR depression), hyperkalemia
Every minute of untreated occlusion = more myocardium lost. Transmit 12-lead early and get moving.
Treatment Sequence
- 1ABCs; oxygen ONLY if SpO2 <94% — avoid hyperoxia (worsens outcomes)
- 212-lead ASAP — transmit to receiving hospital + ACTIVATE PCI pathway (door-to-balloon <90 min goal)
- 3Aspirin 324 mg PO chewed — if no allergy, no active GI bleed
- 4Nitroglycerin 0.4 mg SL — ONLY if: SBP >90, no PDE-5 inhibitor use in past 24–48h, no RV infarct
- 5IV access; continuous cardiac monitoring, SpO2
- 6Analgesia per protocol — fentanyl often preferred (morphine may worsen outcomes in STEMI)
- 7Antiemetic if needed (ondansetron per protocol)
- 8MINIMIZE SCENE TIME — rapid transport to PCI-capable facility
NITRO CONTRAINDICATIONS: RV infarct / inferior STEMI + hypotension | PDE-5 inhibitors (sildenafil <24h, tadalafil <48h) | SBP <90 mmHg | Severe aortic stenosis
ATYPICAL PRESENTATIONS: Elderly, women, diabetics may present with nausea, weakness, diaphoresis, jaw/arm pain, or fatigue WITHOUT classic chest pressure. Low threshold for 12-lead.
"Longer, longer, longer, drop — then you have Wenckebach." Mobitz II has no warning and needs pacing immediately.
AV Block Comparison
| Block | EKG Finding | Danger | Treatment |
|---|---|---|---|
| 1st Degree | PR >0.20 sec; all P waves conduct; 1:1 P:QRS | Low — monitor | No treatment; monitor; identify cause (drugs, inferior MI) |
| 2nd Degree Mobitz I (Wenckebach) | PR progressively lengthens → dropped QRS; grouped beats; narrow QRS | Moderate — usually benign | Atropine if symptomatic; treat cause; usually responds to atropine |
| 2nd Degree Mobitz II | Constant PR → sudden dropped QRS without warning; often wide QRS; 2:1, 3:1 ratios | HIGH — can → 3rd degree or arrest | TCP immediately; atropine often DOES NOT work (infranodal); dopamine/epi if TCP unavailable |
| 3rd Degree (Complete) | P waves and QRS march independently; QRS rate depends on escape focus | CRITICAL — low output, shock | TCP immediately; sedate if conscious; epi/dopamine infusion; rapid transport |
ATROPINE in MOBITZ II: Ineffective (and potentially harmful) — the block is BELOW the AV node in the His-Purkinje system. Go directly to PACING.
EXAM TRAP: Wenckebach = lengthening PR then drop (kind warning). Mobitz II = constant PR then sudden drop (no warning, dangerous). Know the difference cold.
Bradycardia Algorithm (Symptomatic)
Symptomatic = bradycardia + hypotension, AMS, ischemic chest pain, acute HF, or signs of shock
- 1Identify and treat reversible causes (hypoxia, hypothermia, inferior MI, drug toxicity, vagal tone)
- 2Atropine 0.5 mg IV — repeat q3–5 min up to 3 mg total (do NOT give <0.5 mg — paradoxical bradycardia)
- 3If atropine ineffective or high-grade block: TCP — confirm BOTH electrical AND mechanical capture; sedate if conscious
- 4If TCP unavailable: Dopamine 2–20 mcg/kg/min OR Epinephrine 2–10 mcg/min infusion per protocol
Four-question algorithm tells you exactly what to do. When in doubt: wide complex = VT. Unstable = cardiovert now.
Decision Algorithm
Unstable → Any Tachycardia
Hypotension, AMS, shock, ischemic pain, HF
→ Synchronized cardioversion NOW
SVT: 50–100J | AF: 120–200J
A-Flutter: 50–100J | VT pulse: 100J
Stable → Follow the Tree
Narrow + Regular → SVT (vagal → adenosine)
Narrow + Irregular → AF/flutter (rate control)
Wide + Regular → VT (amiodarone if stable)
Wide + Irregular → Torsades/AF+aberrancy (Mg for Torsades)
Rhythm-by-Rhythm Treatment Guide
| Rhythm | Key EKG Feature | Stable Tx | Unstable Tx |
|---|---|---|---|
| Sinus Tach | Regular narrow; P waves upright; 100–180 | Treat the CAUSE — not the rate | Treat underlying cause; cardioversion inappropriate |
| SVT (AVNRT/AVRT) | Regular narrow; P hidden in/after QRS; abrupt onset/offset; 150–250 | Vagal → Adenosine 6mg rapid IVP + flush; 12mg × 2 if needed | Synchronized cardioversion 50–100J |
| Atrial Fibrillation | Irregularly irregular; absent P waves; fibrillatory baseline | Rate control per protocol; NEVER adenosine for irregular rhythms | Synchronized cardioversion 120–200J |
| Atrial Flutter | Sawtooth flutter waves ~300 bpm; ventricular rate often 150 (2:1 block) | Rate control; adenosine may unmask flutter waves for diagnosis | Synchronized cardioversion 50–100J |
| Monomorphic VT (pulse) | Regular wide QRS; AV dissociation if seen; 100–250 | Amiodarone 150mg IV over 10 min OR procainamide per protocol | Synchronized cardioversion 100J |
| Torsades de Pointes | Irregular wide twisting QRS around baseline; triggered by long QT | Magnesium sulfate 1–2g IV over 15 min; correct K+; stop offending drugs | Defibrillate if pulseless; magnesium + cardioversion if pulse |
| WPW | Short PR (<0.12), delta wave, wide QRS; can conduct rapidly via accessory pathway | AVOID AV nodal blockers (adenosine, CCBs, beta-blockers, digoxin) | Cardioversion; procainamide per protocol |
NEVER use adenosine, verapamil, diltiazem, or digoxin in wide-complex irregular tachycardia or known WPW with AF — risk of VF and death.
Cardioversion & Defibrillation Energy Guide
| Procedure | Indication | Energy (Biphasic) | Key Rules |
|---|---|---|---|
| Defibrillation (unsync) | VF, pulseless VT, unstable polymorphic VT | 200J (360J monophasic) | Do NOT synchronize — no organized R wave; deliver immediately |
| Synchronized Cardioversion | Tachycardia WITH pulse and organized rhythm | SVT: 50–100J | AF: 120–200J | Flutter: 50–100J | VT pulse: 100J | MUST synchronize — delivers on R wave peak; verify sync mode active before each shock |
| Transcutaneous Pacing | Symptomatic bradycardia (esp. Mobitz II, 3° block) | Start 60–80 mA; increase until electrical capture | Confirm MECHANICAL capture (palpation — do NOT rely on EKG alone); sedate if conscious |
Shock ASAP → resume CPR immediately → epi every 3–5 min → amiodarone after 2nd/3rd shock → treat Hs & Ts.
Shockable Algorithm (VF / Pulseless VT)
- 1CPR immediately → attach pads → analyze
- 2Defibrillate ASAP (200J biphasic / 360J monophasic) → RESUME CPR immediately — do NOT check pulse after shock
- 3After 2 min CPR → rhythm check → shock again if still shockable
- 4IV/IO access → Epinephrine 1mg IV/IO every 3–5 min
- 5After 2nd or 3rd shock: Amiodarone 300mg IV/IO rapid push (repeat 150mg once) OR Lidocaine 1–1.5 mg/kg
- 6Continue CPR cycles; search and treat Hs & Ts
- 7Secure airway (advanced airway); continuous waveform capnography
High-Quality CPR Standards (AHA 2025)
| Parameter | Standard |
|---|---|
| Rate | 100–120 compressions per minute |
| Depth (Adult) | At least 2 inches (5 cm); not more than 2.4 inches (6 cm) |
| Recoil | Full chest recoil — do NOT lean on chest |
| Interruptions | Minimize pauses; pre/post-shock pauses <10 sec |
| Compression Fraction | >80% of arrest time |
| Ventilation (advanced airway) | 1 breath every 6 seconds (10 bpm); avoid hyperventilation |
| Ventilation (no advanced airway) | 30:2 ratio; minimize pauses for breaths |
| EtCO2 Target | ≥10 mmHg during CPR; sudden rise to 35–45 = ROSC → check pulse |
PEA and asystole: CPR + epinephrine + aggressive Hs & Ts search. Do NOT defibrillate — no shock for non-shockable rhythms.
Non-Shockable Algorithm
- 1CPR immediately — do NOT interrupt for shocks
- 2IV/IO → Epinephrine 1mg IV/IO every 3–5 min
- 3PRIORITIZE reversible causes (Hs & Ts) — this is your only treatment lever
- 4Rhythm check every 2 min — if converts to shockable, switch to VF algorithm
- 5Asystole: double-check leads, gain, and connections before calling it
Hs & Ts — Reversible Causes
| Cause | Clues | Treatment |
|---|---|---|
| Hypovolemia | Trauma, blood loss, narrow pulse pressure | IV/IO fluid bolus; hemorrhage control |
| Hypoxia | Cyanosis, airway compromise, undetectable SpO2 | BVM, advanced airway, O2 |
| Hydrogen Ion (Acidosis) | Prolonged arrest, DKA, overdose, renal failure; wide QRS | Hyperventilate slightly; sodium bicarb per protocol |
| Hypo/Hyperkalemia | Dialysis patient; peaked T waves / wide QRS / sine wave | Calcium chloride IV for hyperK; treat arrhythmia |
| Hypothermia | Cold environment, cold/stiff patient | Warm IV fluids, warming; do NOT pronounce until "warm and dead" |
| Tension Pneumothorax | Absent breath sounds + JVD + tracheal deviation + trauma | Needle decompression: 2nd ICS MCL or 4th–5th ICS AAL |
| Tamponade (Cardiac) | Beck's Triad: hypotension + JVD + muffled heart sounds; trauma | Rapid transport; cautious fluids; hospital pericardiocentesis |
| Toxins | Known overdose, medication bottles, tox screen | Specific antidotes (naloxone, atropine, bicarb TCA, glucagon/Ca BB/CCB) |
| Thrombosis (Pulmonary PE) | Sudden arrest with known DVT risk; chest pain before arrest | Systemic thrombolytics per protocol; CPR without delay |
| Thrombosis (Coronary) | STEMI/ACS → arrest; most common cause of VF arrest | High-quality CPR + defibrillation + PCI transport |
Post-ROSC Care
- Avoid hyperoxia: titrate SpO2 to 94–99% — 100% is harmful post-arrest
- Avoid hypotension: maintain SBP ≥90 mmHg; fluids/vasopressors per protocol
- Avoid hyperventilation: target EtCO2 35–45 mmHg (10–12 bpm with advanced airway)
- 12-lead immediately: look for STEMI → activate PCI pathway
- Keep defibrillator ready — high risk of re-arrest
- Glucose check — hypoglycemia can prevent ROSC or cause re-arrest
Know mechanism, indication, dose, and key contraindications cold. NREMT tests clinical reasoning around drug selection.
Cardiac Arrest Drugs
| Drug | Indication | Dose (Adult) | Key Notes |
|---|---|---|---|
| Epinephrine 1:10,000 | ALL cardiac arrest (VF, pVT, PEA, asystole) | 1mg IV/IO q3–5 min | Alpha-1: vasoconstriction → ↑ coronary/cerebral perfusion during CPR. Give ASAP in PEA/asystole. |
| Amiodarone | Refractory VF/pVT after 2nd shock | 300mg IV/IO rapid push; repeat 150mg once | Broad-spectrum (Na, K, Ca blocker + alpha/beta). Causes hypotension/bradycardia. Dilute in D5W. Half-life ~40 days. |
| Lidocaine | Alternative to amiodarone for refractory VF/pVT | 1–1.5 mg/kg IV/IO; repeat 0.5–0.75 mg/kg q5–10 min | Second choice to amiodarone. Toxicity: CNS effects (tremors, seizures, slurred speech). |
| Magnesium Sulfate | Torsades de Pointes; refractory VF with suspected hypoMg | 1–2g IV over 15 min; rapid push if pulseless | Terminates Torsades. Avoid in hyperMg. Can cause hypotension if given too fast. |
| Sodium Bicarbonate | TCA overdose, hyperK, prolonged arrest, severe acidosis ONLY | 1 mEq/kg IV/IO | NOT routine in arrest — ↑ CO2 intracellularly, worsens acidosis without adequate ventilation. Specific uses only. |
| Calcium Chloride | Hyperkalemia (cardiac effects), hypocalcemia, CCB overdose | 500–1000mg (5–10 mL of 10%) slow IV | Stabilizes cardiac membrane in hyperK. Do NOT mix with bicarb (precipitates). |
| Atropine | Symptomatic bradycardia (NOT in cardiac arrest per ACLS) | 0.5mg IV q3–5 min; max 3mg total | Min 0.5mg dose (paradoxical brady with less). NOT effective for Mobitz II or 3rd degree infranodal block. |
Adenosine: fast and specific for regular SVT. Amiodarone: broad-spectrum. Know what each one is contraindicated in.
| Drug | Use Case | Dose | Watch Out |
|---|---|---|---|
| Adenosine | SVT (regular narrow-complex tachycardia) — first-line after vagal maneuvers | 6mg rapid IVP + 20mL NS flush; 12mg × 2 if needed | MUST give FAST (half-life ~10 sec). Use antecubital or large vein. Transient asystole — warn patient. NEVER for irregular, wide-complex, or WPW + AF. |
| Amiodarone (stable) | Stable monomorphic VT; AF/flutter rate control in critically ill | 150mg IV over 10 min; then infusion per protocol | Hypotension, bradycardia common. Extremely long half-life. Dilute in D5W only. |
| Dopamine | Bradycardia (2nd line after atropine); cardiogenic shock (low-dose) | 2–20 mcg/kg/min infusion | Dose-dependent: 2–5=renal/dopaminergic; 5–10=beta (inotrope); 10–20=alpha (vasoconstrict). Tachyarrhythmias at higher doses. |
| Procainamide | Stable monomorphic VT (alternative to amiodarone) | 20–50 mg/min IV until converts, hypotension, or max 17 mg/kg | Prolongs QT; avoid if QT prolonged; hypotension; not for WPW. |
| Diltiazem / Verapamil | Rate control in stable AF/flutter (no WPW, no severe LV dysfunction) | Diltiazem 15–20mg IV over 2 min per protocol | CONTRAINDICATED in WPW, VT, heart failure with systolic dysfunction; causes hypotension. |
Aspirin is always first in ACS. Nitro has critical contraindications. Fentanyl now preferred over morphine in STEMI.
| Drug | Indication | Dose | Key Points |
|---|---|---|---|
| Aspirin | ACS/STEMI (antiplatelet) | 324mg PO chewed | Inhibits thromboxane A2 (platelet aggregation). CI: true ASA allergy or active GI bleed. Give immediately. |
| Nitroglycerin | Angina, STEMI (if no contraindication), hypertensive emergency with chest pain, CHF/pulmonary edema | 0.4mg SL q5 min × 3; IV infusion for refractory | CI: RV infarct, SBP <90, PDE-5 inhibitors, severe aortic stenosis. Headache common. |
| Morphine | ACS pain (use cautiously); pulmonary edema | 2–4mg IV titrated per protocol | May cause hypotension, nausea, respiratory depression. Fentanyl often preferred in STEMI. Reduces preload in CHF. |
| Fentanyl | ACS/chest pain analgesia; intubation premedication | 1–2 mcg/kg IV/IO titrated per protocol | Shorter duration than morphine. Less hypotension. Better tolerated in hemodynamically unstable patients. |
| Furosemide | Acute pulmonary edema / decompensated CHF | 40–80mg IV per protocol | Diuresis (delayed) + immediate venodilation. Use with CPAP and nitrates for maximum benefit. Watch for hypotension and hypokalemia. |
Don't just treat low BP — find the mechanism. Cardiogenic: pump failure. Obstructive: mechanical block. Distributive: vasodilation. Hypovolemic: volume loss.
| Type | Mechanism | Classic Signs | Prehospital Treatment |
|---|---|---|---|
| Cardiogenic | Pump failure (large MI, severe arrhythmia) | Cool/clammy, hypotension, pulmonary edema (wet crackles), JVD, tachy | 12-lead; treat ACS; cautious fluid; vasopressor/inotrope; CPAP for pulm edema; rapid transport to PCI |
| Obstructive — Tension PTX | Lung collapse prevents venous return | Absent breath sounds (affected side), JVD, tracheal deviation (late), hypotension | Needle decompression: 2nd ICS MCL or 4th–5th ICS AAL; reassess |
| Obstructive — Tamponade | Pericardial fluid compresses heart | Beck's Triad: hypotension + JVD + muffled heart sounds; electrical alternans on EKG | Cautious fluid bolus; avoid vasodilators; rapid transport (pericardiocentesis in hospital) |
| Obstructive — Massive PE | Clot obstructs pulmonary outflow | Acute dyspnea, pleuritic chest pain, JVD, hypotension; sudden arrest after surgery/immobility | O2; IV; thrombolytics per protocol for arrest; transport. CPAP may worsen RV failure. |
| Distributive — Septic | Vasodilation from infection | Warm skin (early), fever or hypothermia, tachy, hypotension, altered mentation | O2; large fluid bolus 20–30 mL/kg; vasopressors if hypotension persists; rapid transport |
| Distributive — Anaphylactic | IgE-mediated vasodilation + bronchospasm | Urticaria, angioedema, stridor, wheeze, hypotension, tachycardia | IM Epi 1:1000 first; O2; fluids; neb albuterol; antihistamine + steroids adjunct |
| Hypovolemic | Blood/fluid loss | Tachycardia, hypotension, cool/pale/diaphoretic, delayed cap refill | Hemorrhage control; IV/IO; fluid bolus per protocol; permissive hypotension in trauma (SBP ~80–90 penetrating) |
| Neurogenic | Spinal cord injury → loss of sympathetic tone | Bradycardia + hypotension + warm/dry skin + paralysis/sensory loss | Spinal precautions; IV fluid; atropine for bradycardia; vasopressor per protocol; careful with fluids |
Aortic dissection can mimic STEMI — never give thrombolytics until dissection is ruled out. CHF: CPAP early, sit upright, nitro if BP allows.
Aortic Dissection
Pathophysiology: Intimal tear → blood enters aortic wall. Type A (ascending) = surgical emergency. Type B (descending) = medical management.
- Sudden, severe "tearing" or "ripping" chest/back/interscapular pain — maximal AT onset (not building)
- Pulse and BP differential between arms (>20 mmHg systolic difference)
- Neurological symptoms (stroke-like) from carotid involvement
- 12-lead may appear NORMAL — important to rule OUT ACS (dissection to coronary ostium can mimic inferior STEMI)
- 1ABCs; high-flow O2; IV access; analgesia; gentle handling
- 2Do NOT give ASA or thrombolytics — catastrophic hemorrhage risk if given for mistaken STEMI
- 3Rapid transport to surgical-capable center; notify receiving hospital early
DISSECTION TRAP: Can mimic inferior STEMI if it extends to the right coronary ostium. Clues: bilateral BP differential, tearing pain from the start, absent/asymmetric pulses. DO NOT give thrombolytics.
Acute Heart Failure / Pulmonary Edema
Signs: Severe dyspnea, orthopnea, bilateral crackles, pink frothy sputum, JVD, peripheral edema, diaphoresis. Hypertension is common (vs cardiogenic shock = hypotension).
- 1Sit upright — legs dependent reduces preload
- 2High-flow O2; continuous SpO2, cardiac monitoring, EtCO2
- 3CPAP early if tolerated — PEEP 5–10 cmH2O reduces preload/afterload and recruits alveoli
- 4Nitroglycerin SL or infusion if SBP adequate (powerful preload reducer)
- 5Furosemide IV per protocol (venodilation + delayed diuresis)
- 6If failing: BVM with PEEP → advanced airway
Hypertensive Emergency
BP typically >180/120 mmHg WITH end-organ damage (neuro symptoms, chest pain, pulm edema, renal failure). Do NOT rapidly reduce BP in the field — goal is controlled reduction (rapid drop → ischemia). Rapid transport; early stroke alert if neuro symptoms present.
Last-minute review table. When you open this card, you should already know every entry — this is the confirm, not the learn.
| Rhythm | Rate | Regular? | QRS | Immediate Action |
|---|---|---|---|---|
| Normal Sinus | 60–100 | Yes | Narrow | No treatment; identify clinical context |
| Sinus Bradycardia | <60 | Yes | Narrow | Stable = monitor; Unstable = atropine → TCP → dopamine/epi |
| Sinus Tachycardia | >100 | Yes | Narrow | Treat the CAUSE — not the rate |
| SVT (AVNRT/AVRT) | 150–250 | Yes | Narrow | Stable: vagal → adenosine 6mg. Unstable: cardiovert 50–100J |
| Atrial Fibrillation | Variable | No (irreg-irreg) | Narrow | Stable: rate control. Unstable: cardiovert 120–200J. NEVER adenosine. |
| Atrial Flutter | ~150 (ventricle) | Reg or reg-irreg | Narrow | Rate control or cardiovert 50–100J |
| 1st Degree AVB | 60–100 | Yes | Narrow | Monitor; treat cause |
| 2nd Degree Mobitz I | Slow | Reg-irregular | Narrow | Monitor; atropine if symptomatic |
| 2nd Degree Mobitz II | Slow | Irregular | Wide (often) | TCP immediately; atropine may not work |
| 3rd Degree (Complete) | <60 (wide/slow) | Regular (2 indep.) | Wide (usually) | TCP immediately; sedate; epi/dopamine |
| Monomorphic VT (pulse) | 100–250 | Yes | Wide | Stable: amiodarone 150mg. Unstable: cardiovert 100J |
| VF | Chaotic | No | No QRS | CPR + DEFIBRILLATE 200J immediately; epi + amiodarone |
| Pulseless VT | >100 | Yes | Wide (pulseless) | CPR + DEFIBRILLATE; same as VF algorithm |
| PEA | Any | Any | Any (not VF/pVT) | CPR + Epinephrine + find/treat Hs & Ts. NO shock. |
| Asystole | None | None | None | CPR + Epinephrine + Hs & Ts; confirm in 2 leads. NO shock. |
| Torsades de Pointes | Irregular | No | Wide/twisting | Magnesium 1–2g IV; defibrillate if pulseless; correct QT |
Clinical judgment scenarios with progressive information. Practice sequencing treatment steps — drag-and-drop TEI questions.
Top Exam Traps & Correct Thinking
- O2 in ACS: Give ONLY if SpO2 <94%. Do NOT routinely give high-flow O2 to a STEMI with normal SpO2.
- Nitro contraindications: RV infarct, SBP <90, PDE-5 inhibitors (sildenafil <24h, tadalafil <48h).
- Inferior STEMI: ALWAYS check right-sided lead (V4R) BEFORE giving nitroglycerin.
- Wide-complex tachycardia: Treat as VT until proven otherwise — NEVER give verapamil or diltiazem.
- Adenosine: Only for REGULAR, narrow-complex tachycardia. NEVER for AF, irregular WCT, or WPW.
- Atropine minimum dose: 0.5 mg IV. Less can cause paradoxical bradycardia.
- Atropine + Mobitz II / 3rd degree (infranodal): Does NOT work — go directly to pacing.
- After defibrillation: Resume CPR IMMEDIATELY — do NOT check pulse right after the shock.
- PEA/Asystole: Epinephrine + find/treat Hs & Ts — NO defibrillation.
- Amiodarone for VF/pVT: 300mg rapid IV push (NOT slow infusion). 150mg for stable VT.
- Stable bradycardia: If hemodynamically stable, just MONITOR — do not treat the rate.
- Irregularly irregular rapid rate = uncontrolled AF: Never adenosine.
- Synchronized cardioversion: MUST synchronize before delivering shock for organized rhythms with pulses.
- ROSC sign: Sudden rise in EtCO2 to 35–45 — check pulse BEFORE stopping compressions.
- Post-ROSC: AVOID hyperoxia AND hyperventilation — both worsen neurological outcomes.
- Torsades: Magnesium 1–2g IV. NOT amiodarone (amiodarone prolongs QT, worsens Torsades).
- Aortic dissection: DO NOT give ASA or thrombolytics. Clue = BP differential between arms + tearing pain.
The numbers and rules you need to have memorized cold. If you have to think about these on scene, it's too late.
High-Yield Numbers Reference
| Value | What It Represents |
|---|---|
| 60–100 bpm | Normal adult heart rate (NSR) |
| PR 0.12–0.20 sec | Normal AV conduction; >0.20 = 1st degree AVB |
| QRS <0.12 sec | Normal (narrow = supraventricular) |
| QRS ≥0.12 sec | Wide = BBB or ventricular origin (VT until proven otherwise) |
| QTc >0.44s (M) / 0.46s (F) | Prolonged QT → Torsades risk |
| 100–120 bpm | Target CPR compression rate |
| ≥2 inches (5 cm) | Minimum adult compression depth |
| ≤10 seconds | Maximum allowable pulse check / compression pause |
| 1mg q3–5 min | Epinephrine in cardiac arrest (IV/IO) |
| 300mg rapid IV | Amiodarone first dose for refractory VF/pVT |
| 6mg rapid IV | Adenosine first dose for SVT |
| 0.5mg IV (min dose) | Atropine; 3mg total max |
| <10 mmHg EtCO2 | Poor CPR quality → improve compressions |
| 35–45 mmHg EtCO2 | ROSC indicator when suddenly reached during CPR |
| SBP ≥90 mmHg | Minimum for nitroglycerin / minimum post-ROSC target |
| SpO2 94–99% | Post-ROSC target (avoid 100%) |
ALWAYS: 12-lead for any chest pain/SOB/syncope. Check right-sided leads in inferior STEMI before nitro. Synchronize for organized rhythms with pulses. EtCO2 for every arrest and advanced airway. Treat the PATIENT not just the monitor.
NEVER: Adenosine for irregular or wide-complex tachycardia. Verapamil/diltiazem for wide-complex VT. Defibrillate PEA or asystole. Nitrates with RV infarct, hypotension, or PDE-5 inhibitors. Assume wide QRS = SVT with aberrancy.
WATCH FOR: Posterior MI mimicking V1–V3 ischemia (tall R + ST depression = mirror image). De Winter T waves = LAD occlusion without ST elevation. Wellens syndrome = critical LAD stenosis during pain-free interval. Electrical alternans = tamponade. LBBB + chest pain = STEMI equivalent.