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The atria are at the front of the room, while the ventricles are at the back of the room. The right atrium is at the lower left of the screen - as if you're looking at your patient. Unfortunately, most of the left atrium is cut off on the lower right of the screen. The SA node is in the very front of the right atrium, and the AV node is in the middle of the screen sitting on the steps between the atria and ventricles. Lining the stairs behind the AV node are the branch bundles and purkinje fibers; the ventricular myocytes are between the branch bundles/purkinje fibers and the walls. In the very back of the right ventricle is the ventricular pacemaker - more from him later. Now for some normal sinus rhythm.
Everything is working fine, but SA node is firing too slowly. NOTE: bradycardia is normal in well trained endurance athletes. There is no video - in the interest of time, we skipped this one.
Everything is working fine, but SA node is firing too fast.
In atrial flutter, a re-entrant circuit forms that causes rapid regular atrial depolarization. In the demo, a loop of depolarizing atrial myocytes surrounding a cluster a non-functioning myocytes fire in rapid succession. Unfortunately, the left atrium is cut off, so you can't see half of the circuit.
Random unsynchronized firing of atrial cells have 2 results: 1) no P wave, and 2) irregularly spaced R-R intervals. The biggest problem with A-fib is formation of blood clots in the left atrium that can embolize, causing ischemia anywhere throughout the body.
An atrial myocyte fires more rapidly than the SA node, setting the pace for the heart.
Similar to atrial tachycardia, except the atrial myocyte only fires sporadically, causing an occasional early beat. The patient feels the next beat because the extra filling time gives a more forceful beat.
No video. In the interest of time, we skipped this one.
The SA node doesn't fire, the AV node waits, and waits, and waits - finally firing to keep the heart beating. This results in a slow heart rate with no P wave.
Similar to the junctional escape rhythm, see above, but the AV node has been pacing the heart for a while and increases the pace.
No video - just image the one above going a little faster.
The AV node fires before the SA node, often obscuring the P wave and causing a short beat. The patient feels the next beat because the extra filling time gives a more forceful beat.
Random unsynchronized firing of ventricular myocytes results in complete absence of blood flow. This is a medical emergency that requires immediate correction or the result is death.
The ventricular pacemaker is firing very fast - lead to tachycardia. V-tach will pump blood, but not very efficiently because: 1) the ventricular contraction is very inefficient, and 2) filling time is very short. V-tach is not sustainable, and this rhythm is a medical emergency.
P waves, but nothing else.
No video.
No SA node or AV node activity. The ventricular pacemaker cell, way in the back, is setting the rhythm. The ventricular action potential doesn't follow the usual order, as a result, there is no normal QRS-T.
The ventricular pacemaker cell fires prematurely, resulting in an early beat with an improperly formed QRS-T. The patient notices the next beat due to the increased preload.
Flat line - no activity at all.
No video.
The AV node is slow resulting in a lengthened P-R interval.
The AV node gets more tired with each impulse, resulting in a longer P-R interval, until a beat is dropped. The P-R interval returns to normal and the cycle repeats.
In the video, the AV nodes only picks up every other P wave.