Cardiac Electrophysiology (Exam IV) Flashcards
Differentiate the location of PSNS (specifically vagal) and SNS input throughout the heart.
- Vagal input occurs at the SA & AV node.
- SNS input occurs throughout the heart.
Where are the internodal pathways located?
What is the general structure of these?
How many are there and what are their names?
- Right Atrium
- Purkinje-ish (more primitive)
1. Anterior internodal
2. Middler internodal
3. Posterior internodal
Where does the interatrial pathway originate? Where does it run through & end?
What is an alternative name for this pathway?
- Originates from anterior internodal pathway, runs between aorta & SVC, terminates in the left atrium.
- Bachmann’s bundle
What is the purpose of Bachmann’s bundle?
What is the cellular structure like?
- Electrical coordination between right & left atria
- Akin to muscle cells but less myofibrils
What properties are conferred to Bachmann’s bundle by having less myofibrils than the surrounding tissue?
- ↑ Conductance
- ↓ Resistance Ω
What usually damages Bachmann’s bundle?
What is the result of damage to this structure?
- MI (i.e. scar tissue) & overstretching
- Loss of coordination between atria.
How much of a delay occurs in the AV node?
- 0.09sec
How long does it take for an electrical impulse from the SA node to reach the AV node?
How much of a delay occurs in the AV node?
How much of a delay occurs in the penetrating portion of the AV bundle?
How much of a delay occurs in the distal portion of the AV bundle?
- 0.03s
- 0.09s
- 0.03s
- 0.01s
How much of a total delay occurs from the SA node to the beginning portions of the Purkinje fibers in the septum?
- 0.16s
How long does it take for entirety of the ventricles to depolarize?
How long would it take for the heart to depolarize completely and what would be the very last site to depolarize?
- 0.06s
- 0.22s
- Upper lateral aspect of left ventricle
How much time would have passed from SA node depolarization to 1 on the figure below?
0.03s
How much time would have passed from SA node depolarization to 9 on the figure below?
0.16s
What structure is denoted by 8 on the figure below? How much of a delay from SA depolarization occurs here?
- AV node
- 0.09s delay from AV node
What structure is denoted by 6 on the figure below? How much of a delay from SA depolarization occurs here?
- Penetrating Portion of AV bundle
- 0.03s delay
What structure is denoted by 5 on the figure below? How much of a delay from SA depolarization occurs here?
- Distal Portion of AV bundle
- 0.01s delay
How much of delay has occurred (from SA node depolarization) to the circle marked by 9 below?
What would this correlate with on an EKG?
- 0.16s
- PR interval
What characteristics of the AV node cause the conductance delay it exhibits?
- ↓ gap junctions = ↑ Ω
What characteristics do Purkinje Fibers possess that allow for increased conductance?
- Large diameter
- ↑ Gap Junctions
- No myofibrils
- Overall low Ω
Where would one expect to find Bundles of Kent?
- Where the Atria & Ventricles meet laterally.
How long does it take for the right atrium to depolarize completely?
The left atrium?
- 0.07s
- 0.09s
How does Bachmann’s bundle & the internodal pathways compare to the Purkinje Fibers?
- Atria Conduction Tissue = some myofibrils, less developed. Fast, but not as fast as Purkinjes.
- Ventricular Purkinje Tissue = No myofibrils, well developed. Very fast.
What portions of the Purkinje Fiber system were described to us in lecture? (List each in order of depolarization & where it is found)
- Posterior Fascicles (branch from septum into the left ventricle
- Anterior Fascicle (towards the apex of the heart)
- Lateral Fascicle (lateral myocardium of heart)
What functions as an insulator between the atria & ventricles in the heart?
What is the exception to this? (in a healthy heart)
- Cartilage
- Foramen for bundle of His
Are accessory pathways (Bundles of Kent) genetic?
What classifications are there for this anatomic anomaly?
- Yes, genetic
- Type A = Left
- Type B = Right
What condition can occur from accessory pathways?
What electrophysiologic component of the heart is bypassed through these pathways?
How much of a delay is bypassed due to this condition?
- WPW (Wolff-Parkinson-White) Syndrome
- AV node is bypassed
- 0.13s delay bypassed
What occurs to the PR interval with WPW (Wolff-Parkinson-White) Syndrome?
What about the QRS complex?
- ↓ PR interval or no PR interval
- Prolonged QRS complex.
What can occur arrhythmia-wise with WPW (Wolff-Parkinson-White) Syndrome?
What makes one prone to arrhythmias with this syndrome?
- Early atrial or ventricular depolarization
- Ectopic atrial or ventricular foci have a pathway to potentially cause arrhythmias.
What syndrome is linked to sudden, fatal cardiac death in young people (20-24yo)?
?
- WPW (Wolff-Parkinson-White) Syndrome
A p-wave with increased mV magnitude would be associated with what?
- Enlarged right atrium
A broader than normal p-wave would be associated with what?
- Enlarged left atrium.
A notched p-wave (with only positive deflection in lead II) would be associated with what?
How does this compare to a p-wave that is completely biphasic?
- Atrial enlargement
- Even worse atrial enlargement
needs verification
What is the first positive deflection after the p-wave in lead II? (assume healthy heart tissue)
- R-wave
What would a ventricular depolarization wave be called if no R-wave was present?
- QS-wave
What would the presence of a QS wave indicate if noted on Lead II?
- Dead heart tissue
At what point is a wide QRS complex diagnosed?
> 0.12s
What is the normal mV of a QRS complex in a non-precordial lead?
- 1.5-2 mV
Are precordial leads more or less sensitive than limb leads?
What QRS complex mV magnitude might be seen in a precordial lead?
How would this compare to a limb lead?
- More sensitive.
- 3-4mV
- Precordial leads are about double limb leads in terms of mV.
Can atrial repolarization be seen in Lead II?
No, should be hidden in the QRS complex.
Why is negative deflection seen for the Q wave?
When is this especially pronounced?
What lead would you be unlikely to see a Q wave in?
- Initial left side depolarization propagating to the right.
- Pronounced in Lead I.
- Lead III.
How long is the QT interval?
What does this time correlate with mechanically?
- 0.35s
- Length of time that ventricles are squeezing.
What layer of the heart is more prone to ischemia and lighter MI’s?
Why is this?
- Endocardium
- Endocardium is deeper and further away from coronary artery. Contraction of the heart can squeeze microvasculature leading to less blood supply the deeper into heart tissue that you go.
- Endocardium also uses more energy.
wordy & needs verification
How long is the ST segment?
What does this segment symbolize (in healthy tissue) ?
- 0.16s
- Time period where all ventricular tissue has been depolarized.