High-fidelity 12-lead EKG schematics, animated rhythm strips, and audio mnemonics for every board-tested pattern. Click any mnemonic to hear it aloud. Click Animate to see the rhythm draw live.
7EKG Patterns
7Animated Strips
14+Audio Mnemonics
24Lead Schematics
Rajiv Choudhary, MD, MPH · PA Clinical Bootcamp
Section 1 · STEMI Recognition
STEMI Patterns — Inferior & Anterior
⚑ STEMI · Inferior
Inferior STEMI — STE in II, III, aVF
Culprit: RCA (85%) · Reciprocal ST depression in I, aVL · Always get V4R to rule out RV MI
● LIVE RHYTHM STRIP — Inferior STEMI PatternLead II · 25mm/s
"II, III, aVF light up below — RCA's to blame, don't let the pressure go." Inferior = bottom leads = floor of the heart = RCA feeds there
Reciprocal: I and aVL go DOWN when II/III/aVF go up · V4R = get it every time
⚑ Board Trap
Inferior STEMI + hypotension → NEVER give nitrates until RV MI excluded. Get right-sided leads (V4R). RV MI is preload-dependent — nitrates drop preload → cardiovascular collapse. Give 1L IV NS bolus instead.
STE Location
II, III, aVF (≥1mm)
Reciprocal ↓
I, aVL
Culprit Artery
RCA (85%) / LCx (15%)
Critical Next Step
Get V4R → rule out RV MI
⚑ STEMI · Anterior
Anterior STEMI — STE in V1–V4
Culprit: LAD · Highest mortality STEMI · Reciprocal depression in inferior leads · Risk of cardiogenic shock
"V1 through V4 — the LAD's war. Widowmaker high, the stakes don't lie." Anterior leads V1-V4 = LAD territory = anterior wall of LV = highest mortality
Proximal LAD → huge territory → cardiogenic shock risk · Watch for new LBBB
⚑ Board Trap
New LBBB + chest pain = STEMI equivalent — treat as anterior STEMI. Sgarbossa criteria (concordant STE ≥1mm, discordant STE ≥5mm, or concordant ST depression in V1-V3) confirm occlusion in LBBB. Cath lab now.
STE Location
V1, V2, V3, V4
Reciprocal ↓
II, III, aVF (sometimes)
Culprit Artery
LAD (Left Anterior Descending)
Complication Risk
Cardiogenic shock, VT/VF
Section 2 · STEMI Equivalents
Wellens Syndrome & De Winter T-Waves
⚑ STEMI Equivalent · Wellens B
Wellens Syndrome Type B — Deep Symmetric T Inversion V2–V3
Patient is PAIN-FREE · Critical LAD stenosis · Stress test absolutely contraindicated · Urgent cath
● LIVE STRIP — Wellens Type B Pattern (V3)Lead V3 · 25mm/s
"Wellens warns when the pain has gone — the LAD is teetering on a bomb." Pain-free patient + deep inverted T waves in V2-V3 = reperfused critical LAD stenosis
Type A = biphasic · Type B = deep symmetric inversion (more common, ~75%)
⚑ Deadliest Board Trap
Wellens + stress test = patient infarcted on the treadmill. The "stable-appearing" pain-free patient with deeply inverted T waves in V2-V3 needs the cath lab today — not a stress test, not floor admission, not discharge. This is the most lethal missed EKG pattern on boards.
Key Finding
Deep symmetric T inversion V2–V3
Clinical Context
Pain-FREE patient (reperfused)
Culprit
Critical proximal LAD stenosis
Action
Urgent cath — NO stress test
⚑ STEMI Equivalent · De Winter
De Winter T-Waves — Upsloping ST Depression + Tall Peaked T Waves
V1–V6 · Static pattern — will NEVER develop ST elevation · Proximal LAD occlusion · The pattern IS the MI
● LIVE STRIP — De Winter Pattern (V3)Lead V3 · 25mm/s
"De Winter climbs up, never comes down — the LAD's occluded without a crown." Upsloping ST depression + tall symmetric T waves = static pattern = active proximal LAD occlusion
No ST elevation ever · aVR may show STE · Immediate cath lab activation
⚑ Board Trap
Do NOT wait for ST elevation — it will never come. De Winter is a static pattern. Unlike STEMI which evolves, De Winter stays this way throughout the occlusion. The upsloping ST depression + tall T waves IS the MI. Cath lab immediately.
Key Finding
Upsloping ST ↓ + tall T in V1–V6
aVR
ST elevation (1–2mm)
Culprit
Proximal LAD occlusion
Critical Fact
Static — STE will NEVER appear
Section 3 · Arrhythmias
Atrial Fibrillation
Arrhythmia · AFib
Atrial Fibrillation — Irregularly Irregular, No P Waves
Fibrillatory baseline · No identifiable P waves · Irregularly irregular R-R intervals · Variable ventricular rate
● LIVE STRIP — Atrial FibrillationLead II · irregularly irregular
"Fibrillation: 'Irregularly Irregular' — no two R-R intervals are the same." No P waves + chaotic baseline + variable R-R = AFib every time
Rate control vs rhythm control · CHA₂DS₂-VASc drives anticoagulation · DOAC preferred
⚑ Board Trap
AFib with rapid ventricular response + wide QRS = consider WPW. If AFib is treated with AV nodal blockers (digoxin, diltiazem, verapamil, adenosine) in WPW, all conduction routes via the accessory pathway → extremely rapid rate → VF. Use procainamide or cardioversion instead.
Rhythm
Irregularly irregular
P Waves
Absent — fibrillatory baseline
Rate
Variable (60–170 uncontrolled)
QRS
Narrow (unless BBB or WPW)
Section 4 · Conduction
3rd Degree (Complete) Heart Block
⚑ Complete Heart Block · Pacemaker Required
3rd Degree AV Block — Complete AV Dissociation
P waves march independently of QRS · P rate > QRS rate · Ventricular escape rhythm · Pacemaker required
"P waves march — QRS doesn't follow. Complete divorce between atria and ventricle." Atria beat at ~75 bpm · Ventricles escape at ~30–40 bpm · No relationship between them
Junctional escape = narrow QRS (40–60) · Ventricular escape = wide QRS (20–40, worse prognosis)
⚑ Board Trap
AV dissociation ≠ always 3rd degree block. AV dissociation can occur with isorhythmic dissociation (rates nearly equal) or VT. True 3rd degree: P rate consistently faster than QRS rate, with NO relationship. Varying PR intervals with NO pattern (not progressively longer, not fixed) = complete block.
P Wave Rate
~60–80 bpm (normal SA rate)
QRS Rate
20–40 bpm (escape rhythm)
PR Relationship
None — completely independent
Treatment
Pacemaker — no exceptions
Section 5 · Bundle Branch Blocks
RBBB & LBBB Patterns
Bundle Branch Block · RBBB
Right Bundle Branch Block — RSR' in V1, Wide S in V6
QRS ≥120ms · RSR' ("rabbit ears") in V1 · Wide slurred S wave in I and V6 · May be normal variant
● LIVE STRIP — RBBB PatternLead V1 · RSR' morphology
"WiRRoW: RBBB = Wide QRS, R in right (V1 RSR'), W in left (V6 wide S)" MaRRoW: In RBBB — M-shape in V1, W-shape in V6
New RBBB in anterior STEMI = proximal LAD occlusion, worse prognosis · Isolated RBBB may be normal
V1 Pattern
RSR' ("rabbit ears" / M-shape)
V6 Pattern
Wide, slurred S wave (W-shape)
QRS Duration
≥120ms (complete RBBB)
Clinical Note
Can be normal variant in young
Bundle Branch Block · LBBB
Left Bundle Branch Block — Broad R in V6, QS in V1
QRS ≥120ms · Broad notched R in V5-V6 · QS or rS in V1 · New LBBB + chest pain = STEMI equivalent
● LIVE STRIP — LBBB PatternLead V6 · Broad notched R wave
"WiLLiaM MaRRoW: LBBB = W in V1, M in V6 (left side gets the M)" LBBB: W-shape in V1 (QS pattern), M-shape in V6 (broad notched R) · Always pathologic
Discordant ST changes expected in LBBB — use Sgarbossa criteria to identify superimposed STEMI
⚑ Board Trap
New LBBB + ischemic symptoms = STEMI equivalent — activate cath lab. Sgarbossa criteria: (1) Concordant STE ≥1mm in any lead, (2) Concordant ST depression ≥1mm in V1-V3, (3) Discordant STE ≥5mm (modified: ratio-based). ST changes in LBBB are expected to be discordant (opposite QRS) — concordant ST changes = ischemia.
V1 Pattern
QS complex (W-shape)
V5–V6 Pattern
Broad notched R (M-shape)
Always
Pathologic — find the cause
+ Symptoms
New LBBB = STEMI equivalent
Section 6 · Pericardial Disease
Electrical Alternans — Cardiac Tamponade
⚑ Tamponade · Electrical Alternans
Electrical Alternans — Alternating QRS Amplitude
Heart swings in pericardial effusion · Beat-to-beat axis change · Pathognomonic for tamponade · Sinus tachycardia + alternans = emergency
● LIVE STRIP — Electrical Alternans PatternLead II · alternating QRS height
"The heart swings in its fluid sea — tall, short, tall, short, alternately." Pericardial effusion → heart swings like a pendulum → electrical axis rotates each beat → alternating QRS height
Sinus tachycardia + electrical alternans = tamponade until proven otherwise · Give fluids, call surgery
⚑ Board Trap
NEVER give furosemide in tamponade. Tamponade physiology is entirely preload-dependent. The compressed heart needs maximal filling pressure to maintain output. Diuresis removes the preload → cardiac collapse. Treatment: IV fluid bolus to maintain preload → urgent pericardiocentesis.