❤️ NREMT Cardiology Mastery Guide

12-Lead ECG · Dysrhythmias · ACLS Algorithms · Heart Blocks · Cardiac Emergencies | The Firefighter Medic

Key Reference Values

Parameter	Normal	Critical Threshold
Heart Rate	60–100 bpm	<50 symptomatic = treat; >150 with instability = cardiovert
PR Interval	0.12–0.20s (3–5 small boxes)	>0.20 = 1st degree block
QRS Duration	<0.12s (3 small boxes)	>0.12 = bundle branch block or ventricular origin
QTc	<440ms men; <460ms women	>500ms = high torsades risk
ST Elevation (STEMI)	None	≥1mm in ≥2 contiguous limb leads; ≥2mm in ≥2 contiguous precordial leads

Topic 1: 12-Lead ECG Interpretation

Lead Groups & Territories

Leads	Territory	Coronary Artery
II, III, aVF	Inferior wall	RCA (85%) or LCx (15%)
V1–V4	Anterior wall	LAD ("widow maker")
I, aVL, V5–V6	Lateral wall	LCx or LAD diagonal
V7–V9 (posterior)	Posterior wall	RCA or LCx
V1, V4R	Right ventricle	Proximal RCA

STEMI Patterns

Inferior STEMI: Elevation in II, III, aVF + reciprocal depression in I, aVL → ALWAYS get right-sided leads (V4R) to rule out RV infarction
Anterior STEMI: Elevation in V1–V4 (LAD occlusion)
Lateral STEMI: Elevation in I, aVL, V5–V6
Posterior STEMI: ST depression + tall R waves in V1–V3 (mirror image — flip the paper)

⚠️ RV MI: ST elevation in V4R ≥1 mm — DO NOT give nitroglycerin. RV MI is volume-dependent; nitro drops preload and kills these patients.

Bundle Branch Blocks

RBBB: QRS >0.12s · RSR' pattern in V1 ("rabbit ears") · Wide S waves in I, V5–V6. New RBBB with anterior STEMI = proximal LAD occlusion (very high risk).

LBBB: QRS >0.12s · Broad notched "M" in I, aVL, V5–V6 · Broad S or QS in V1–V3. New LBBB in chest pain = STEMI equivalent → activate cath lab. Use Sgarbossa Criteria.

Sgarbossa Criteria (≥3 points = highly specific for STEMI)

ST elevation ≥1 mm concordant with QRS: 5 points
ST depression ≥1 mm in V1–V3: 3 points
ST elevation ≥5 mm discordant with QRS: 2 points

Pericarditis vs. STEMI — ECG Differences

Feature	Pericarditis	STEMI
ST elevation	Diffuse (all leads), concave "saddle-shaped"	Focal (territory-specific), convex "tombstone"
PR segment	Depression (pathognomonic)	Normal
Reciprocal changes	Absent	Present
Q waves	Absent	Develop over hours

STEMI Treatment Protocol

Aspirin 324 mg PO (chew)
12-lead ECG within 10 minutes of contact
IV access ×2, oxygen if SpO2 <94%
Nitroglycerin 0.4 mg SL (if SBP >100, no RV MI, no PDE5 inhibitors in 24–48h)
Cath lab activation (door-to-balloon <90 minutes)

⚠️ Exam Traps: ST elevation in aVR + diffuse depression = left main or proximal LAD occlusion. T-wave inversions are NOT an acute STEMI finding. Posterior STEMI has NO elevation on standard 12-lead — look for depression V1–V3 + tall R waves. Aortic dissection mimicking STEMI: check BP differential between arms BEFORE giving thrombolytics.

Topic 2: Dysrhythmia Recognition & Management

Key Rhythm Characteristics

Rhythm	Rate	Regularity	P Wave	QRS
Normal Sinus	60–100	Regular	Present, upright	Narrow <0.12s
Sinus Bradycardia	<60	Regular	Present	Narrow
Sinus Tachycardia	>100	Regular	Present	Narrow
SVT	150–250	Regular	May be hidden	Narrow
Atrial Flutter	~150 ventricular	Regular (2:1)	Sawtooth waves	Narrow
Atrial Fibrillation	Irregular	Irregularly irregular	None — chaotic	Narrow
Junctional	40–60	Regular	Inverted/absent/retrograde	Narrow
VT	>100	Regular	AV dissociation	Wide >0.12s
VF	Chaotic	Absent	None	Chaotic/absent
Asystole	None	None	Absent	Absent

Management by Rhythm

Symptomatic Bradycardia: Atropine 0.5 mg IV (repeat q3–5 min, max 3 mg) → TCP if atropine fails → Dopamine 2–10 mcg/kg/min or Epinephrine 2–10 mcg/min infusion

Stable SVT: Vagal maneuvers (modified Valsalva) → Adenosine 6 mg rapid IVP + flush → 12 mg ×2 if needed

Unstable SVT: Synchronized cardioversion 50–100 J

Stable Monomorphic VT: Amiodarone 150 mg IV over 10 min; Lidocaine 1–1.5 mg/kg IV alternative

Unstable VT: Synchronized cardioversion 100 J

VF/Pulseless VT: Unsynchronized defibrillation 200 J → CPR 2 min → reassess → Epinephrine 1 mg q3–5 min → Amiodarone 300 mg (2nd dose 150 mg)

⚠️ Exam Traps: Never give adenosine in wide complex tachycardia of unknown origin — risk of VF degeneration in VT. AF is "irregularly irregular." Flutter typically shows 2:1 block → ventricular rate ~150 bpm — always suspect flutter when rate is exactly 150. Confirm V-fib in ≥2 leads before shocking — don't shock artifact.

Topic 3: ACLS Algorithms

Shockable Rhythms: VF / Pulseless VT

VF/pVT Detected ↓ Defibrillate 200 J (biphasic) → CPR 2 min ↓ Rhythm check → VF/pVT still? ↓ Defibrillate → CPR 2 min → Epinephrine 1 mg IV ↓ Rhythm check → VF/pVT still? ↓ Defibrillate → CPR 2 min → Amiodarone 300 mg IV ↓ Continue: Epi q3-5 min, Amiodarone 150 mg second dose ↓ Treat reversible causes (H's and T's)

Non-Shockable: PEA / Asystole

PEA/Asystole Detected ↓ CPR 2 min → Epinephrine 1 mg IV ASAP ↓ Rhythm check q2 min → Search reversible causes H's: Hypovolemia · Hypoxia · H+ (acidosis) · Hypo/Hyperkalemia · Hypothermia T's: Tension pneumo · Tamponade · Toxins · Thrombosis (PE/MI) Continue CPR → Epi q3-5 min

Drug Summary

Drug	VF/pVT	PEA/Asystole	Notes
Epinephrine 1 mg	After 3rd shock	ASAP	q3–5 min
Amiodarone 300 mg	After 3rd shock	No	2nd dose 150 mg
Lidocaine 1–1.5 mg/kg	Alternative to amio	No	—
Sodium Bicarb	Not routine	Not routine	Hyperkalemia, TCA OD, prolonged arrest only
Magnesium 1–2g	Torsades	No	Suspected hypoMg

⚠️ Vasopressin was removed from ACLS guidelines in 2019. Bicarb is NOT routine in cardiac arrest. In witnessed VF, time to first shock is the priority — not epinephrine. Two minutes of CPR between rhythm checks.

Topic 4: Heart Blocks

Classification Summary

Block	PR Interval	Dropped QRS	Location	Risk	Treatment
1st Degree	>0.20s, constant	None — all P's conduct	AV node	None	Monitor only
2nd Degree Mobitz I (Wenckebach)	Progressively lengthens	Predictable (after lengthening)	AV node	Low	Monitor; atropine if symptomatic
2nd Degree Mobitz II	Constant	Sudden, no warning	His-Purkinje (below AV node)	HIGH — may progress to complete block	TCP urgently
3rd Degree (Complete)	No relationship	P's and QRS both regular but independent	Complete AV dissociation	HIGH — syncope, hemodynamic compromise	TCP immediately; transvenous pacing

⚠️ Exam Traps: In 3rd degree block, P waves and QRS are both regular — just unrelated. Atropine has limited effect in Mobitz II and complete block (infranodal) — TCP is the intervention. Never try to suppress the ventricular escape rhythm in complete block — it's a safety mechanism. Wide QRS in complete block = ventricular escape (more unstable than narrow junctional escape).

Topic 5: Chest Pain Differential Diagnosis

Can't-Miss Diagnoses

Diagnosis	Classic Features	Key Finding	Prehospital Action
STEMI	Crushing pressure, radiation, diaphoresis	ST elevation on 12-lead	Aspirin, 12-lead, cath lab activation
Aortic Dissection	Tearing/ripping, sudden, radiates to back	BP differential >20 mmHg between arms	NO thrombolytics, NO aspirin, rapid transport
Pulmonary Embolism	Pleuritic, dyspnea, tachycardia	SpO2 drop, sinus tach, S1Q3T3 on ECG	Oxygen, IV, rapid transport
Tension Pneumothorax	Unilateral pleuritic, dyspnea	Absent breath sounds, JVD, tracheal shift	Needle decompression
Cardiac Tamponade	Pressure, dyspnea, pulsus paradoxus	Beck's triad, electrical alternans	IV fluids, rapid transport

⚠️ Exam Trap: Nitro relieves esophageal spasm too — relief with nitro does NOT rule out non-cardiac cause. Women, diabetics, and elderly often present atypically — epigastric pain, fatigue, or jaw pain. Aortic dissection mimicking STEMI: giving thrombolytics = catastrophic hemorrhage. Always check for BP differential in tearing back pain + chest pain.

Topic 6: Cardiogenic Shock

Cardiogenic shock = inadequate cardiac output → end-organ hypoperfusion despite adequate volume. Pump failure — most commonly from large anterior MI.

Assessment: "Wet and Cold"

Hypotension (SBP <90 mmHg)
Cold, clammy, mottled skin (high SVR)
Tachycardia, altered mental status
Pulmonary edema ("wet lungs, cold extremities")
JVD (elevated preload)

Treatment Protocol (Prehospital)

Oxygen: maintain SpO2 94–99%
CPAP/BiPAP for associated pulmonary edema
Vasopressors: Norepinephrine 0.1–0.5 mcg/kg/min (preferred); Dopamine 5–20 mcg/kg/min (alternative)
Avoid aggressive fluids — 250 mL bolus ONLY if dry presentation
Cath lab activation: emergent PCI is definitive treatment
RV MI: give fluids + NO nitroglycerin

⚠️ Cardiogenic shock has COLD extremities despite pulmonary edema — differentiates from distributive shock. Fluids can worsen cardiogenic shock. Dopamine at high doses increases afterload and can worsen pump failure. RV MI: fluids are life-saving; nitro is lethal.

Topic 7: CHF & Acute Pulmonary Edema

Assessment Findings

Severe dyspnea, orthopnea, paroxysmal nocturnal dyspnea
Diffuse bilateral crackles (rales) — "wet" lungs
Pink frothy sputum (severe APE)
JVD, peripheral edema, tachycardia
Hypoxia (SpO2 <90% common)

Treatment — Hypertensive APE (SBP >140)

Position upright (legs dependent — reduce preload)
CPAP 5–10 cmH2O — first-line intervention
Nitroglycerin 0.4 mg SL q5 min (aggressive nitro is most effective in hypertensive APE)
Furosemide: in-hospital primarily; prehospital use per protocol
Avoid fluids, avoid beta-blockers acutely

⚠️ Morphine for CHF is no longer recommended — associated with increased mortality. CPAP improves SpO2 faster than oxygen alone. Nitroglycerin is the most effective prehospital drug for hypertensive APE — not furosemide. "Cardiac asthma" (CHF with wheeze) — do NOT treat with albuterol alone; treat the CHF.

Topic 8: Hypertensive Emergencies

Hypertensive Urgency: BP >180/120 without end-organ damage — no immediate threat.
Hypertensive Emergency: Severely elevated BP WITH end-organ damage (brain, heart, kidneys).

Special Cases

Hypertensive Encephalopathy: Controlled reduction — drop too fast → cerebral ischemia. Target 10–20% reduction in first hour.
Eclampsia: Magnesium sulfate 4–6g IV over 15–20 min (first-line). Labetalol/hydralazine for BP. Avoid ACE inhibitors, diuretics, nitroprusside in pregnancy.
Aortic Dissection: Target SBP <120 mmHg — aggressive BP control IS indicated. Labetalol preferred.

⚠️ Never aggressively lower BP in hemorrhagic stroke — reduces cerebral perfusion. Eclampsia seizures: magnesium first, NOT diazepam. "Worst headache of my life" + BP 220/130 = hypertensive emergency until proven otherwise.

Topic 9: Pericarditis & Cardiac Tamponade

Pericarditis

Sharp pleuritic pain — worse lying flat, better leaning forward
Pericardial friction rub on auscultation
ECG: diffuse concave ST elevation, PR depression (most specific finding)
Treatment: NSAIDs + colchicine; rest; no steroids for viral

Cardiac Tamponade — Beck's Triad

Hypotension (decreased CO)
JVD (impaired venous return)
Muffled/distant heart sounds

Additional: Pulsus paradoxus >10 mmHg · Electrical alternans (virtually pathognomonic) · Tachycardia · Narrow pulse pressure

Treatment: IV fluids to maintain preload (temporizing) → rapid transport → pericardiocentesis (hospital)

⚠️ Beck's triad is only present in ~30% of tamponade cases. Electrical alternans = virtually pathognomonic for large pericardial effusion. Pulsus paradoxus >10 mmHg is NOT specific to tamponade — also seen in tension pneumo and severe asthma. Muffled heart sounds are nearly impossible to hear in a noisy field environment.

Topic 10: Transcutaneous Pacing (TCP)

Indications

Symptomatic bradycardia not responding to atropine
Mobitz II AV block
Complete (3rd degree) AV block
Bradycardic cardiac arrest (bridge to transvenous pacing)

Procedure

Apply pacing pads (anterior-posterior preferred)
Set initial rate: 70–80 bpm
Start current low (30–40 mA), increase in 5–10 mA increments
Electrical capture: pacer spike followed by wide QRS
Mechanical capture: palpate femoral or carotid pulse (NOT radial — artifact)
Set final current 10–20 mA above capture threshold
Sedate conscious patients: fentanyl, midazolam, or ketamine per protocol

⚠️ Confirm mechanical capture by palpating CENTRAL pulse (femoral/carotid) — NOT radial (muscle contraction artifact). TCP is a bridge, not a fix. In complete AV block, set rate ABOVE the escape rate. TCP is painful for conscious patients — analgesia/sedation is mandatory.

Topic 11: Synchronized Cardioversion

Indications (Unstable Tachycardias WITH Pulse)

Unstable SVT, AF, flutter, or monomorphic VT
Instability: hypotension, altered mentation, acute MI, pulmonary edema

Energy Settings (Biphasic)

Rhythm	Initial Energy
SVT	50–100 J
Atrial Flutter	50–100 J (often converts at low energy)
Atrial Fibrillation	120–200 J
Monomorphic VT	100 J

⚠️ Sync mode MUST be reactivated after each shock — most defibrillators default back to non-sync. If VF develops: turn OFF sync immediately and defibrillate unsynchronized. Polymorphic VT (Torsades): treat with unsynchronized defibrillation + magnesium. Do NOT cardiovert stable AF without anticoagulation if >48 hours duration (clot embolism risk).

Topic 12: Post-ROSC Care

The 10 Post-ROSC Priorities

Airway: Confirm ET tube with waveform capnography
Ventilation: Target EtCO2 35–45 mmHg — avoid hyperventilation
Oxygenation: Titrate FiO2 to SpO2 94–99% — avoid hyperoxia
BP: Target SBP ≥100 mmHg (MAP ≥65 mmHg)
12-lead ECG: STEMI → cath lab immediately (even if comatose)
Glucose: Treat hypoglycemia (<60 mg/dL) and hyperglycemia (>180 mg/dL)
Seizures: Monitor and treat with benzodiazepines
Temperature (TTM): 32–36°C for comatose survivors — 24 hours
IV access: Secure and confirm
Transport: Directly to cardiac arrest center if available

Ventilation Targets

Parameter	Target	Avoid
SpO2	94–99%	>99% (hyperoxia → free radical injury)
EtCO2	35–45 mmHg	<35 (hypocapnia → cerebral vasoconstriction)
RR	10–12/min (adult)	>12 (hyperventilation)

⚠️ Hyperventilation post-ROSC causes cerebral vasoconstriction. Hyperoxia is harmful — titrate O2 down once SpO2 ≥94%. STEMI in comatose post-ROSC patient = still goes to cath lab. TTM is 32–36°C — NOT specifically 32°C. Aggressive glucose control causes harm — target 140–180 mg/dL.

Cardiac Drug Quick Reference

Drug	Indication	Dose	Key Notes
Aspirin	ACS	324 mg PO chewed	Not for aortic dissection; avoid in true allergy
Nitroglycerin	ACS, APE, HTN emergency	0.4 mg SL q5 min	Hold if SBP <100, RV MI, PDE5 inhibitors
Epinephrine 1:10,000	Cardiac arrest	1 mg IV q3–5 min	—
Amiodarone	VF/pVT, VT	300 mg IV (arrest); 150 mg over 10 min (stable VT)	2nd dose 150 mg
Adenosine	SVT	6 mg rapid IVP → 12 mg ×2	Rapid push + flush; NOT in wide complex unknown origin
Atropine	Symptomatic bradycardia	0.5 mg IV q3–5 min, max 3 mg	Limited in Mobitz II/complete block
Norepinephrine	Cardiogenic shock, post-ROSC hypotension	0.1–0.5 mcg/kg/min	Vasopressor of choice in cardiogenic shock
Magnesium Sulfate	Torsades, eclampsia	Torsades: 1–2g IV; Eclampsia: 4–6g IV	Caution in renal failure
Dopamine	Bradycardia, cardiogenic shock	2–20 mcg/kg/min	Low: renal; mid: cardiac; high: vascular/afterload

NREMT Exam Strategy — Cardiology

Always get a 12-lead first — it drives every major cardiac decision
Know your energy levels: synchronized vs. unsynchronized, joules per rhythm
Stability = treatment decision: hypotensive? altered? ischemic? pulmonary edema? = unstable
Wide complex = VT until proven otherwise — never assume SVT with aberrancy in the field
STEMI mimics: aortic dissection (tearing + BP differential), pericarditis (diffuse concave ST), LBBB
Know when NOT to give drugs: Nitro in RV MI, aspirin in aortic dissection, adenosine in WPW-AF, bicarb in routine arrest
Post-ROSC care is testable: TTM, SpO2 94–99%, EtCO2 35–45, SBP ≥100, 12-lead, cath lab activation