EKG Exam Flashcards
EKG graph
EKG graph
QRS configurations
PR interval
- time from start of atrial depolarization to start of ventricular depolarization
- .12-.2sec
- isoelectric
ST segment
*J point
end of ventricular depolarization and initiation of ventricular repolarization
QT interval
time taken for ventricular depolarization and repolarization
P wave
- atrial depolarization
- less than .12 sec
- 3 small boxes
- amp is less than 2.5 mm in limb leads
- amp is less than 1.5 mm in precordial leads
Left Ventricular Hypertrophy
LVH in AVL
5 basic types of arrhythmias
- Arrhythmias of sinus origin—originate in the SA node, but the rate is too fast, too slow, or irregular
- Ectopic rhythms—originating in a focus other than the SA node
- Re-entrant arrhythmias—an electrical impulse trapped and recirculating somewhere in the heart
- Conduction blocks—a normally originating impulse following a normal track that encounters unexpected delays or blocks
- Pre-excitation syndromes—an impulse following an abnormal or aberrant pathway through the heart, i.e., a shortcut
Arrhythmias of sinus origin
- Sinus tachycardia (fast rate)—above 100 beats per minute
- Sinus bradycardia (slow rate)—below 60 beats per minute
-
Sinus arrhythmia – slightly irregular sinus rhythm in which the variation in heart rate accompanies respiration
- The heart rate accelerates with inspiration and slows with expiration
- Sinus arrest, Asystole, and Escape beats
- In Sinus Arrest, the SA node does not fire normally and so there is a pause between complexes
- If nothing else happens, the EKG would just be a flat line without any electrical activity—prolonged electrical inactivity is called Asystole
- Thankfully, other natural cardiac pacemakers may take over in sinus arrest and spontaneously depolarize, generating a rescue or “escape beat”
Sinus tachycardia
Sinus bradycardia
Respiratory Sinus Arrhythmias
Sinus pause, arrest, escape beat
Ectopic or Nonsinus Pacemakers
¤Atrial pacemakers (other than the SA node, i.e., the P-Wave looks different from a P-wave originating in the SA node)
- AV Nodal or Junctional pacemakers ( usually no P Wave at all- may see a retrograde P wave-, and normal QRS complex)
- Ventricular pacemakers (wide, bizarre QRS complexes)
- Atrial—60-75 beats per minute
- Junctional—40-60 beats per minute
- Ventricular—30-45 beats per minute, generally less than 40
Supraventricular Arrhythmias
- Paroxysmal supraventricular tachycardia (PSVT)
- Atrial Flutter (Flutter)
- Atrial Fibrillation (AF or A Fib)
- Multifocal Atrial Tachycardia (MAT)
- Paroxysmal Atrial Tachycardia (PAT)
Paroxysmal supraventricular tachycardia (PSVT)
Atrial Fibrillation (AF or A Fib)
Atrial Flutter (Flutter)
Multifocal Atrial Tachycardia (MAT)
Wandering Atrial Pacemaker
Paroxysmal Atrial Tachycardia (PAT)
Ventricular Arrhythmias
*rhythm disturbances arising below the AV node*
- Premature Ventricular Contractions (PVCs)
- Ventricular Tachycardia (VT or V tach)
- Ventricular Fibrillation (V fib)
- Accelerated Idioventricular Rhythm
- Torsade de Points (a unique form of VT)
Premature Ventricular Contractions (PVCs)
Ventricular Tachycardia (VT or V tach)
Ventricular Fibrillation (V fib)
Accelerated Idioventricular Rhythm
Torsade de Points (a unique form of VT)
Supraventricular vs. Ventricular Arrhythmias
- The main distinction between supraventricular and ventricular arrhythmias is simply that:
- Supraventricular arrhythmias have a narrow QRS complex
- Ventricular arrhythmias have a wide QRS complex
- You can see a wide complex which is preceded by a P Wave which comes from above the ventricles but it must be conducted aberrantly (and it will usually come with a pulse) due to a block in the conduction system - this is known as “SVT with aberrancy”
Conduction Blocks
¤Any obstruction or delay in the flow of the electrical current through the normal conduction pathways of the heart is considered a Conduction Block, i.e., a blockage in time.
- A conduction block can occur anywhere in the system but typically appears in one of three areas:
- Sinus Node Block—it appears as a delay or pause in the cardiac cycle
- Atrio-ventricular Block—a block anywhere between the SA node and the Purkinje fibers, including the AV node and Bundle of His
- Bundle Branch Block—a block in part or all of the ventricular bundle branches
1st degree AV block
2nd degree AV block (Mobitz 1/Wenckebach)
2nd degree AV block (Mobitz 2)
Mobitz 1 vs. Mobitz 2
3rd degree AV block
RBBB
LBBB
Hemiblocks
- When we talk about hemiblocks, we are talking about the left bundle only and either anterior or posterior fascicle pathology
- Hemiblocks cause axis deviation
- A Left Anterior Hemiblock causes a left axis deviation (Lead 1 is positive and aVF is negative) and it is more common of the two types of blocks
- A Left Posterior Hemiblock causes a right axis deviation (Lead 1 is negative and aVF is positive)
- Hemiblocks do not prolong the QRS complex
- Hemiblocks do not cause any ST segment or T Wave changes
- These axis deviations are NOT due to ventricular hypertrophy
Left Anterior Hemiblock
Left Posterior Hemiblock
Preexcitation Syndromes
- There are two major pre-excitation syndromes:
- Wolff-Parkinson-White (WPW) syndrome
- Lown-Ganong-Levine (LGL) syndrome
- These two conditions are actually the opposite of cardiac blocks, that is the electrical current is conducted to the ventricles more rapidly than usual
- In order for pre-excitation syndromes to exist there must first be accessory pathways in the patient (i.e., congenital abnormalities)
- Less than 1% of individuals possess accessory pathways; males predominate. The accessory pathway may be an isolated finding, or occasionally noted in patients with mitral valve prolapse, hypertrophic cardiomyopathies, and other congenital disorders
Wolff-Parkinson-White (WPW) syndrome
Lown-Ganong-Levine (LGL) syndrome
