Differential diagnoses for T wave inversions
- Coronary artery disease (ischemia, reperfusion, Wellens waves)
- Pulmonary causes (PE, pneumothorax, pulmonary HTN, pneumonia, hyperventilation, etc.)
- Neurological causes (elevated intracranial pressure, hemorrhage, etc.)
- Post-tachycardia, post-shock, post-pacing (“cardiac memory”)
- Arrhythmogenic right ventricular dysplasia/cardiomyopathy (V1-V3)
- Brugada syndrome (V1-V2)
- Wide QRS complexes (BBB’s, PVC’s, Paced rhythms, WPW)
- High left ventricular voltage, LVH with strain pattern
- Pericarditis, myocarditis
- Vasospasm (cocaine, amphetamines, etc.)
- Hyperkalemia, hypokalemia
- Juvenile T-wave pattern, normal finding in pediatric ECGs (V1-V3)
- Mitral valve prolapse
- Normal finding in V1, aVR, and lead III
Differential diagnosis for T-wave inversions in V1-V3
- Anteroseptal ischemia
- Pulmonary causes (PE, pneumothorax, pulmonary HTN, pneumonia, hyperventilation, etc.)
- Arrhythmogenic right ventricular dysplasia/cardiomyopathy (V1-V3)
- Brugada pattern
- Right bundle branch block
- Juvenile T-wave pattern
Differential Dx for long QT interval (greatest concern when QTc > 500ms)
- Electrolytes
- Hypokalemia
- Hypomagnesemia
- Hypocalcemia
- Hypothermia
- ACS / cardiac ischemia
- Elevated intracranial pressures
- Medications (i.e., sodium channel blocking drugs)
- Congenital
Causes of prolonged QT-interval summary
Prolonged QT due to abnormal/prolonged T –waves
- Hypokalemia
- Hypomagnesemia
- Medications (i.e., sodium channel blocking drugs)
- Misc: Elevated ICP, Cardiac ischemia, Congenital
Prolonged QT due to prolonged ST-segment
Differential for non-conducted P-waves (P:QRS > 1, “electrocardiographic polyuria”)
Blocked Premature Atrial Complexes
- P waves are irregular in rhythm, and an ectopic P wave is present (different morphology, with abnormal P wave axis)
- The non-conducted ectopic P wave comes early and there is a compensatory atrial pause before the next normal sinus beat
- Commonly misdiagnosed as Mobitz II (which is distinguished by a constant P-P interval)
2nd degree AV Block: Mobitz I (Wenckebach)
- P waves are regular (P-P interval is constant)
- Progressive PR interval lengthening prior to a non-conducted P wave
- At least 2 consecutive P-QRS complexes that demonstrate the gradually increasing PR interval before the single non-conducted P wave (two consecutive non-conducted P waves rules out Mobitz I)
- QRS complexes are usually narrow (block at level of AV node) unless there is also a bundle branch or fascicular block
- Results in clumped or grouped beats and a regularly irregular ventricular rhythm when conduction is fixed (variable conduction ratios also possible)
- Commonly misdiagnosed as atrial fibrillation
2nd degree AV Block: Mobitz II
- P waves are regular (P-P interval is constant)
- Constant PR interval that remains unchanged prior to a non-conducted P wave (e.g., 3:2 conduction, 4:3 conduction, etc.)
- At least 2 consecutive P-QRS complexes that demonstrate the constant PR interval before the non-conducted P-wave
- QRS complexes are usually wide (infranodal block)
- Results in clumped or grouped beats and a regularly irregular ventricular rhythm when conduction is fixed (variable conduction ratios also possible)
- Patients usually need permanent pacemaker
2nd degree AV Block: 2:1 conduction
- P waves are regular (P-P interval is constant)
- Every other P wave is a non-conducted P wave (2:1 conduction), so you do not have 2 consecutive P-QRS complexes before the non-conducted P wave
- Hence, it is difficult to differentiate Mobitz I vs. Mobitz II when 2:1 AV block is present
- With a standard ECG, there is limited opportunity to observe for the constant PR interval characteristic of Mobitz II
- Consider a long rhythm strip or repeat ECGs
2nd degree AV Block: Advanced AV Block or “High-grade AV Block”
- P waves are regular (P-P interval is constant)
- More than 2 consecutive P waves are non-conducted (P:QRS ³ 3:1)
- Type I: block at level of AV node
- Type II: block is infranodal, suspected usually based on width of QRS, ~75-80% are Type II
- Most patients will require a pacemaker regardless of terminology
- In contrast to 3rd degree (complete) heart block, some P waves continue to be conducted to the ventricle
3rd degree AV Block (Complete Heart Block) + AV dissociation
- P-P intervals and QRS complex intervals are regular and constant but occur independently of each other
- PR-interval is randomly changing
- No apparent communication between atrium and ventricle (AV dissociation)
- Narrow QRS = Junctional escape rhythms (ventricular rate ~40-60), usually vagal with better prognosis
- Wide QRS = Ventricular escape rhythms (ventricular rate ~20-40), infranodal, more likely to need a permanent pacemaker
3rd degree AV Block (Complete Heart Block) + Isorhythmic AV dissociation
- CHB where atrial rate and ventricular rate are approximately the same
