ECG cases

Below are cases using ECG interpretation to guide patient management.

First try to interpret the ECG and apply it in clinical context.

Click on the drop down menu for a hint or related question.

Then see below for the answer.

55 year old with weakness

what's the empiric treatment?

H: junctional bradycardia
E: wide QRS with RBBB morphology
A: left axis from LAFB
R: early R wave from RBBB
T: normal voltages
S: diffuse peaked T waves, coved ST elevation V2 (Brugada pattern)

= severe hypekalemia: K8 from obstructive uropathy

Follow up ECG below after initiation of management showed less bradycardia, narrower QRS, ongoing peaked T waves and Brugada pattern in V2

STEMI: what else does the ECG show?

where's the culprit lesion, and are there any signs of reperfusion?

H: normal sinus rhythm = no tachycardia to indicate cardiogenic shock
E: normal intervals = no ischemic conduction abnormality
A: normal axis = no inferior or lateral Q waves
R: normal R wave progression = no anterior Q waves
T: normal voltages
S: primary ST elevation and hyperacute T waves V1-6 and extending to II/aVF = antero-apical-inferior; terminal T wave inversion V2-5 = small degree of spontaneous reperfusion

= acute, likely wraparound LAD occlusion, with small degree of spontaneous reperfusion

40 year old, history pacemaker, with shortness of breath

what are pacemaker functions?

H: AV pacemaker with sensing (detects presence or absence of P waves), pacing (spikes) and capture (spike followed by depolarization). Most beats are intrinsic sinus beats followed by ventricular pacing, and pauses are caused by lack of sinus beats with atrial sensing/pacing
E: LBBB type morphology (typical of pacemaker in right ventricle)
A: extreme axis (pacer in apex)
R: no R wave progression (pacer in apex)
T: normal voltages
S: discordant and proportional ST changes

= AV pacing with normal sensing/pacing/capture, with LBBB and secondary repolarization abnormalities. No ECG explanation for patient symptoms

70 year old with chest pain and widespread STE

H: sinus brady
E: normal conduction
A: normal axis
R: normal R wave
T: normal voltages
S: primary antero-inferior STE and hyperacute T waves, STD aVR reciprocal to STE II and STD III reciprocal to aVL

= antero-inferior STEMI: rule out distal or wraparound LAD occlusion

25 year old with tachycardia. What's the rhythm?

how do you differentiate regular narrow complex tachycardias?

regular narrow complex tachycardia with sinus P waves (upright in I/II, inverted in aVR, biphasic in V1) = sinus tachycardia

40 year old, CKD, with pleuritic positional chest pain

what is differential for ST elevation, what is distribution of ST elevation and where is there reciprocal change?

H: normal sinus
E: normal intervals
A: normal axis
R: normal R wave
T: tall voltages
S: diffuse concave STE without hyperacute T waves, STE II>III, reciprocal STD in aVR only

= pericarditis. POCUS showed normal LV with minimal pericardial effusion. Troponin was normal. Dx uremic pericarditis, consider TB

70 year old with shortness of breath

look at V1 for the rhythm

H: normal sinus (biphasic P waves in V1) with narrow escape rhythm
E: third degree AV block
A: normal axis
R: late R wave
T: LVH
S: ST/T discordant and proportional to LVH

= sinus with 3rd degree AV block and junctional escape, with chronic LVH --> pacemaker

25 year old, history of CKD, with weakness

how would you describe the T waves?

H: normal sinuss
E: normal intervals
A: left axis from LAFB
R: normal R wave progression
T: normal voltages
D: peaked T waves (tall relative to QRS, narrow base, sharp peak, look pinched)

= hyperkalemia. Potassium was 6.3

Why is there left axis deviation?

look at the P wave direction

sinus rhythm goes directly towards lead II, so lead II should have the biggest P waves. Here the P wave in I is greater than II, and P/QRS/T is inverted in III. This combination suggests left arm/left leg reversal of the ECG leads, and should be repeated with correct placement

65 year old with one day short of breath, Killip 4

are Q waves old, subacute, or acute?

H: sinus
E: normal intervals
A: left axis from old inferior Q
R: no R wave progression from precordial Q waves
T: normal voltages
S: primary convex STE and T wave inversion V2-5

= ROSC after subacute (Q+STE+TWI) anterior MI

60 year old with shortness of breath and BP 220

are the ST/T changes secondary to abnormal depolarization, or primary from ischemia?

H: normal sinis
E: normal interval
A: normal axis
R: delayed R wave (transition V5)
T: LVH (SV2 + RV6>35; and R aVL>11) with strain
S: ST/T changes discordant and proportional to QRS

= LVH with secondary repolarization abnormalities, no signs of ischemia --> treat hypertension

60 year old with dizzy and syncope

what kind of AV block, and where is the escape rhythm coming from?

H: normal sinus rhythm with complete AV block and ventricular escape (wide complex QRS, rate 30)
E: variable PR, wide QRS with RBBB morphology, long QT
A: normal axis
R: early R wave from RBBB
T: normal voltages
S: no ST/T changes

= complete AV block with ventricular escape, and long QT --> temporary epi/pacing and permanent pacing for AV block, magnesium and correct electrolytes for long QT

50 year old, ischemic cardiomyopathy, with shortness of breath

any signs of old or new MI?

H: sinus brady
E: RBBB with preceding Q waves
A: left axis from left anterior fascicular block
R: early R wave from RBBB, persist S from LAFB
T: normal voltages
S: anterior mild convex ST elevation into inverted T wave

= bifasicular block with old anterior MI (Q wave, mild convex STE into inverted T wave), no sign of acute MI: POCUS for CHF

40 year old, ESRD, with soft tissue infection

how would you describe these T waves?

H: normal sinus
E: normal intervals
A: normal axis
R: normal R wave
T: normal voltages
S: diffuse peaked T waves (symmetric with narrow base and sharp peak)

= rule out hyperkalemia

45 year old with vomiting and dehydration

what electrolyte abnormalities can this produce?

H: sinus tach (biphasic P waves in V1)
E: long QT, with overlap of T and P waves
A: normal axis
R: normal R wave
T: normal voltages
S: precordial STD

= volume loss with long QT and STD: rule out hypokalemia, empiric magnesium

35 year old, lung cancer, with shortness of breath

how does POCUS complement the ECG?

H: normal sinus
E: normal conduction
A: normal axis
R: delayed R wave
T: small voltages limb leads (all<5mm) and precordial leads (all<10)
S: non-specific changes

= cancer with shortness of breath and diffuse low voltage: POCUS confirmed pericardial effusion and tamponade

55 year old with chest pain, serial ECGs

compare occlusion and reperfusion

H: sinus brady
E: normal conduction
A: normal axis
R: borderline early R wave V2
T: normal voltages
S: inferior Q in III, hyperacute T waves III/aVF with reciprocal STD I/aVL, and STD/TWI V2-3

= infero-posterior occlusion MI with secondary bradycardia, likely RCA occlusion

H: sinus brady
E: normal intervals
A: normal axis
R: borderline early R wave
T: normal voltages
S: Q wave and reperfusion TWI III/aVF, resolution of reciprocal STD I/aVL and V2-3

= reperfusion

50 year old with syncope

Notice two morphologies of QRS and the relationship of the P waves to them

H: regularly irregular bradycardia, wide complex with AV dissociation and narrow complex arriving earlier with preceding P wave

E: wide QRS complex with RBBB morphology

A: wide QRS complex with left axis from LAFB morphology, narrrow complex with normal axis

R: early R wave from RBBB

T: normal voltages

S: no changes

= high grade AV block, narrow complexes with AV conduction alternating with 3rd degree AV block and ventricular escape from left posterior fascicle (RBBB/LAFB morphology): needs pacemaker

70 year old with short of breath

What are the criteria for LBBB

H: sinus rhythm (P waves upright in II/I, inverted aVR, and biphasic in V1)
E: normal PR, wide QRS with typical LBBB morphology, but wider than normal (one large box = 200ms)
A: normal axis
R: R wave transition V5 (typical of LBBB)
T: normal voltages
S: discordant and proportional ST change, negative modified Sgarbossa

= sinus rhythm, LBBB without signs of ischemia, but wider QRS than normal QRS - find and treat cause for shortness of breath, consider hyperkalemia

60 year old with SOB, weak and dizzy

What are the different types of AV block?

H: regular narrow complex bradycardia with AV dissociation = sinus rhythm and junctional escape
E: 3rd degree AV block (variable PR interval), narrow QRS
A: normal axis
R: normal R wave progression
T: normal voltages
S: no ST/T changes

= 3rd degree AV block with junctional escape: epi infusion if hypotensive, consult CCU for permanent pacemaker

50 year old with chest pain

How acute is the MI, and what complications might you see on POCUS?

H: normal sinus
E normal intervals
A: normal axis
R: loss of R waves with Q waves V2-5
T: normal voltages
S: convex STE into TWI

= subacute anterior MI (Q waves and T wave inversion) with minimal benefit from reperfusion. POCUS for corresponding anterior regional wall motion abnormalities and apical thrombus, anti-platelet/anti-coagulant and admission CCU

80 year old with shortness of breath

What's the axis?

H: regular wide complex tachycardia without P waves
E: atypical RBBB morphology (V1 monophasic R)
A: extreme axis deviation
R: R wave upright in V1 and almost fully negative in V6
T: normal voltages
S: secondary changes

= monomorphic VT until proven otherwise: electrical cardioversion if unstable, amiodarone if stable

65 year old with chest pain/short of breath

What regional wall abnormalities do you expect from this ECG?

H: normal sinus rhythm (P waves upright in I, biphasic in V1)
E: normal PR, QRS, QT
A: right axis from lateral Q waves
R: early R wave in V1 reciprocal to posterior Q wave
T: normal voltages
S: primary ST elevation I/aVL with reciprocal ST depression III/aVL, ST depression V1-3, ST elevation V4-6

= subacute postero-lateral STEMI: POCUS for corresponding regional wall motion abnormalities, clinically assess for and manage cardiogenic shock, dual anti-platelts and heparin, CCU consult

35 year old with dizziness

What's the differential and management for wide complex tachycardia?

H: wide complex tachycardia which is regular (not AF), and not preceded by P waves (not sinus tach) = VT until proven otherwise
E: LBBB-type morphology but slow onset depolarization (rS>100ms V2-4)
A: normal axis
R: late R-wave progression
T: normal voltages
S: secondary discordant changes

= monomorphic VT until proven otherwise. Could be PSVT + LBBB but there are atypical features (wide rS), VT is statistically far more likely especially with a history of cardiac disease, and it is safer to treat as VT. Adenosine is very short acting and could be tried, but otherwise treat as VT: electrical cardioversion if unstable, cardioversion vs amiodarone or procainamide if stable. Patient was cardioverted with amio.

70 year old with palpitations

What's the differential for narrow complex tachycardia?

H: regular narrow complex tachycardia without P wave or flutter waves = SVT
E: normal QRS
A: normal axis
R: normal R wave
T: small voltages
S: no ST/T changes

= SVT -

-> cardiovert if unstable, AV node blockade (eg modified valsalva, adenosine, calcium channel blockers) if stable

20 year old, cardiomyopathy, with CHF and irregular pulse

What's the differential for irregular narrow complex tachycardia?

H: sinus (P waves upright in II, biphasic in V1) with premature complexes, not AF
E: normal intervals
A: normal
R: normal
T: tall voltages (normal for age), no LVH strain pattern
S: no ST/T changes

= sinus with premature complexes, not AF --> treat underlying cause (diuresis for CHF)

60 year old with 2 days of chest pain

How can the ECG reveal the acuity of coronary occlusion despite subacute symptoms?

H: AF with rapid ventricular response
E: normal QRS
A: normal axis
R: late R waves from anterior Q waves
T: low voltages limb leads
S: large ST elevation and hyperacute T waves V2-4, and hyperacute T wave V5

= anterior STEMI with large ST elevation and hyperacute T wave despite a week of symptoms.

--> dual antiplatelet, heparin, CCU consult for emergency PCI

40 year old, history of lupus, with shortness of breath

What's the differential for low voltage?

H: sinus tachycardia
E: normal intervals
A: normal axis
R: normal R-wave
T: low voltages limb leads (all <5mm) and chest leads (all <10)
S: non-specific TWI precordial leads

= shortness of breath with sinus tachycardia and low voltage: rule out pericardial effusion

--> POCUS revealed large pericardial effusion with tamponde, treated with pericardiocentesis

30 year old, post-partum, with shortness of breath

What are ECG features of acute RV strain?

H: sinus tach
E: normal intervals
A: borderline right axis
R: normal
T: normal
S: primary T-wave inversion anterior (V2) and inferior (III)

= features of acute RV strain, with PE risk factor

--> CT chest confirmed PE

30 year old, rheumatic heart disease, short of breath

What are ECG features of rheumatic heart disease

H: typical atrial flutter (inverted inferior leads, upright V1)
E: 2:1 block
A: right axis
R: early R wave V1, persist S wave in V6
T: normal
S: no ST/T change

= rheumatic heart disease with ECG features of chronic RV strain from pulmonary hypertension, and AFL with 2:1 block

--> POCUS revealed valvular heart disease, RV strain and pulmonary edema, treated with diuretics

50 year old, CKD, with dehydration and short of breath

What are ECG features of hyperkalemia?

H: normal sinus
E: long PR, normal QRS
A: borderline right axis
R: normal
T: low limb
S: diffuse peaked T waves

= dehydration with multiple features of hyperkalemia

--> empiric calcium

60 year old with chest pain

What are the Modified Sgarbossa Criteria

H: sinus rhythm (biphasic P waves in V1), borderline tachycardic
E: wide QRS from LBBB
A: normal axis
R: normal R wave
T: normal voltages
S: excess discordant ST elevation V2-3 (ST/S>25%), and concordant ST elevation V5 (likely V4-5 lead reversal)

= LBBB + LAD occlusion

--> dual antiplatelets, heparin, CCU consult for emergent angiography

50 year old, cardiac history, with shortness of breath

What are the types of AV block?

H: normal sinus rhythm with 2:1 conduction, not sinus bradycardia (note second P wave which is not conducted)
E: 2nd degree AV block, RBBB
E: left axis from inferior Q waves (from old MI)
R: early R wave from RBBB
T: normal voltages
S: anterior ST depression/T-wave inversion secondary to RBBB

= previous MI with 2nd degree AV block and RBBB, likely infranodal Mobitz 2 block

--> monitor for progression to third degree AV block, consult CCU

60 year old, COPD and pacermaker, short of breath

What are pacemaker functions and types of failutres

H: normal sinus rhythm with atrial sensing, ventricular pacing and capture
E: LBBB morphology from ventricular pacing
A: left axis from ventricular pacing
R: late R wave from ventricular pacing
T: normal voltages
S: ST/T discordant and proportional to QRS, no Modified Sgarbossa Criteria or features of hyperkalemia

= normal ventricular pacing, no ECG explanation for symptoms

--> assess for other causes of shortness of breath, eg COPD exacerbation

50 year old recent chest pain, now resolved

What are signs of acute coronary occlusion with reperfusion?

H: normal sinus
E: normal intervals
A: left axis from inferior infarct
R: early R wave V2
T: normal voltages
S: T wave inversion inferior and lateral (with reciprocal upright T waves V1-2

= inferior infarct with infero-postero-lateral, likely from right coronary artery --> assess for inferior regional wall motion abnormality on POCUS, dual antiplatelets, heparin, cath lab

50 year old, history of hypertension, with CHF

What are signs of LVH?

H: sinus arrhythmia
E: normal PR, slight wide QRS
A: borderline left axis
R: normal R wave
T: tall voltages with LVH (R in aVL>11 and SV2+RV5>35, with strain pattern
S: secondary, discordant and proportional ST/T

= LVH with secondary repolarization abnormalities. POCUS showed CHF treated with diuresis, no ECG sign of ischemia but troponin sent to rule out ACS

50 year old, history CAD and pacemaker, with chest pain

What are ECG signs and treatment for VT?

H: regular wide complex tachycardia without P waves = monomorphic VT until proven otherwise
E: wide QRS with atypical RBBB morphology (qR in V1, not rsr')
A: left axis
R: abnormal R wave with dominant R in V1 but dominant S in V6
T: normal voltages
S: secondary changes

= monomorphic VT --> synchronized cardioversion, or trial of amiodarone if stable

post-cardioversion ECG shows atrial and ventricular pacing with capture, and no signs of ischemia

50 year old with chest pain

H: sinus bradycardia
E: first degree AV
A: normal
R: early R wave
T: tall voltages in apical distribution
S: discordant and proportional ST/T

=LVH with secondary repolarization abnormalities, rule out apical hypertrophic cardiomyopathy --> echo

40 year old with resolved chest pain

H: normal sinus
E: normal intervals
A: normal axis
R: normal R wave
T: normal voltages
S: biphasic R waves V2-4

= resolved chest pain with reperfusion T wave inversion, concerning for Wellens syndrome (LAD reperfusion) --> antiplatelets, heparin and angiography for critical LAD stenosis

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