ELECTROCARDIOGRAPHY Flashcards
What are the most commonly used voltage criteria to diagnose left ventricular hypertrophy?
• R wave in V5-V6 plus S wave in V1-V2 > 35 mm (Sokolow criterion)
• R wave in lead I plus S wave in lead III > 25 mm
• R wave in lead aVL plus S wave in V3 > 28 mm in men and > 20 mm in women (Cornell criteria)
These criteria are used in electrocardiographic (ECG) diagnosis of left ventricular hypertrophy (LVH)
What are common nonvoltage ECG findings that suggest LVH?
• Left atrial enlargement
• Widened QRS complex > 90 milliseconds
• Repolarization abnormality (ST-segment and T-wave abnormalities)
• Left axis deviation
• R-wave peak time > 50 milliseconds
These findings are indicative of left ventricular hypertrophy on an ECG
What are the most commonly used criteria to diagnose right ventricular hypertrophy?
• R wave in V1 ≥ 7 mm
• R/S wave ratio in V1 > 1
These criteria assist in diagnosing right ventricular hypertrophy
What criteria are used to diagnose left atrial enlargement?
• P-wave total width > 0.12 seconds in inferior leads (II, III, aVF) with a double-peaked P wave
• Terminal portion of the P wave in lead V1 ≥ 0.04 seconds wide and ≥ 1 mm deep
These measurements help identify left atrial enlargement on an ECG
What ECG finding suggests right atrial enlargement?
P-wave height in the inferior lead ≥ 2.5 mm
This finding is indicative of right atrial enlargement
What is the normal rate of a junctional rhythm?
40 to 60 beats per minute (bpm)
Junctional rhythms can also be categorized as accelerated (61 to 99 bpm) or junctional tachycardia (> 100 bpm)
How can one distinguish a junctional escape rhythm from a ventricular escape rhythm in a patient with complete heart block?
• Junctional escape rhythms occur at a rate of 40 to 60 bpm and are usually narrow complex
• Ventricular escape rhythms occur at a rate of 30 to 40 bpm and are typically wide complex
This distinction is important in diagnosing heart block
Describe the three types of heart blocks.
• First-degree heart block: PR interval is a fixed duration > 0.20 seconds
• Second-degree heart block: Mobitz type I (Wenckebach) - PR interval increases until a P wave is not conducted; Mobitz type II - fixed PR interval with occasional nonconducted P waves
• Third-degree heart block: All P waves are not conducted; atrial rate is faster than ventricular escape rate
Each type of heart block has distinct features critical for diagnosis
What are the causes of ST-segment elevation?
• Acute myocardial infarction (MI)
• Prinzmetal angina
• Cocaine-induced MI
• Takotsubo cardiomyopathy
• Brugada syndrome
• Pericarditis
• Left ventricular aneurysm
• Left bundle branch block (LBBB)
• LVH with repolarization abnormalities
These causes must be considered in patients presenting with ST-segment elevation on an ECG
What are the ECG findings of hyperkalemia?
• Peaked T waves
• Loss of P waves
• QRS widening
• ST-segment elevation
• Preterminal finding: sinusoidal pattern
These changes reflect the effects of elevated potassium levels on cardiac repolarization
What are the ECG findings in pericarditis?
• PR segment depression
• Diffuse ST-segment elevation
• ST depression in lead aVR
• Later T wave inversions
These findings are characteristic of pericarditis on an ECG
What is electrical alternans?
Alteration of the amplitude of the QRS complex in the presence of large pericardial effusions
This finding indicates significant pericardial effusion
What are the main ECG findings in hyper- and hypocalcemia?
• Hypercalcemia: QT interval shortens
• Hypocalcemia: QT interval prolongs due to delayed repolarization
These changes are important for understanding the effects of calcium levels on cardiac function
What ECG findings may be present with a pulmonary embolus?
• Sinus tachycardia
• Right atrial enlargement (P pulmonale)
• T-wave inversions in leads V1-V2
These findings can raise suspicion of pulmonary embolism in patients with chest pain or shortness of breath
How is the QT interval calculated?
Measured from the beginning of the QRS complex to the end of the T wave
The corrected QT interval (QTc) accounts for heart rate variations
What is torsades de pointes?
A ventricular arrhythmia that occurs in the setting of QT prolongation, characterized by twisting QRS axis around the isoelectric line
It is typically unstable and may require prompt defibrillation
What are cerebral T waves?
Strikingly deep and inverted T waves seen with central nervous system diseases, particularly hemorrhages
They are due to prolonged repolarization and should not be confused with cardiac ischemia
What are Osborne waves?
Upward deflections at the J point of the QRS complex occurring in hypothermia
These waves indicate repolarization abnormalities due to low body temperature
What findings help distinguish ventricular tachycardia from supraventricular tachycardia with aberrancy?
• Concordance in precordial leads
• Initiation of R wave to peak of S-wave duration > 100 milliseconds
• AV dissociation
These criteria aid in differentiating between VT and SVT
What are the ECG criteria for left bundle branch block?
• QRS > 120 milliseconds
• Broad R waves in I, V5, V6 with no Q waves
• Broad monomorphic S waves in V1
• ST and T waves opposite in direction to QRS
These criteria are essential for diagnosing left bundle branch block
What are the ECG criteria for right bundle branch block?
• QRS > 120 milliseconds
• RSR’ (M-shaped QRS complex) in V1 and V2
• Broad S wave in lateral leads (V5, V6, I, aVL)
These criteria are crucial for diagnosing right bundle branch block
What ECG finding is associated with central nervous system disease, particularly subarachnoid and intracerebral hemorrhages?
Markedly deep and inverted T waves
This finding is significant in diagnosing central nervous system conditions.
What are Osborne waves associated with?
Hypothermia
Osborne waves are characteristic ECG findings in cases of severe hypothermia.
What does the Sgarbossa criteria help clinicians identify in patients with left bundle branch block?
ST-segment–elevation myocardial infarction (STEMI)
These criteria are essential for accurately diagnosing STEMI despite the presence of LBBB.
List the three components of the Sgarbossa criteria.
- Concordant ST-segment elevations >1 mm in leads with a positive QRS complex
- Concordant ST-segment depressions >1 mm in leads with a negative QRS complex (usually V1-V3)
- Discordant ST-segment elevations >0.5 mm
What is Wellens’ sign an ECG manifestation of?
Proximal left anterior descending stenosis in patients with acute coronary syndrome
Wellens’ sign is a critical indicator in the assessment of coronary artery disease.
Describe the characteristics of Wellens’ sign on ECG.
Deep (>2 mm), symmetric, and often biphasic T-wave inversions in the anterior precordial leads
This specific pattern is indicative of significant coronary artery stenosis.
What does concordance in an ECG refer to?
Both the QRS complex and the ST segment have a positive or a negative axis.
What does discordance in an ECG indicate?
The axis of the QRS differs from that of the ST segment.
What ECG findings help determine if there is an ST-segment–elevation myocardial infarction in the presence of left bundle branch block?
Look for concordant and discordant ST-segment changes
These findings are crucial for accurate diagnosis despite the masking effects of LBBB.
True or False: Left bundle branch block (LBBB) inherently has ST abnormalities.
True
In the context of ECG, what is the significance of deep T-wave inversions?
They are often seen in conditions like Wellens’ sign and indicate severe coronary artery disease.
