Fascicular Blocks, Animation
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- Опубліковано 20 сер 2024
- EKG/ECG reading for Left anterior fascicular block, LAFB, left posterior fascicular block, LPFB, (hemiblocks) bifascicular, and trifascicular blocks.
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Voice by : Marty Henne
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The left bundle branch that delivers electrical signals to the left ventricle has 2 main fascicles: left anterior and left posterior, which conduct impulses to the anterior and posterior walls, respectively. There is also a small septal fascicle that activates the left septal surface.
In normal conduction, the 3 fascicles start to depolarize simultaneously. In the first 10 ms, the anterior and posterior vectors move in nearly opposite directions, cancelling each other, so the initial overall electrical direction is mainly determined by the septal fascicle, which conducts from the left septal surface to the right. The major vector that follows is the combination of activation waves from the anterior and posterior fascicles. The net movement is downward and slightly left. Because this vector is responsible for depolarization of the main mass of the larger left ventricle, it represents the cardiac axis, defined as the net direction of electrical activity during depolarization.
Left anterior fascicular block (LAFB) and left posterior fascicular block (LPFB) refer to an obstruction in the left anterior or left posterior fascicle, respectively. The hallmark of LAFB and LPFB is a deviation in the cardiac axis.
In LAFB, the anterior branch is blocked, and the posterior fascicle must activate the entire left ventricle. At first, the impulses follow the posterior fascicle downward, toward the inferior leads, resulting in a small positive deflection, small r wave, in these leads. The signals then move up and leftward, through the myocardium, to the rest of the ventricle, producing a large negative deflection, large S wave, in inferior leads. The reverse is observed in lateral leads, which show small q, big R patterns. The cardiac axis is skewed left compared to normal conduction. Also, as one fascicle is doing the job of two, it takes slightly more time than usual, resulting in a small widening of the QRS complex, not more than 0.12 secs.
LAFB may occur as an isolated finding, or in association with cardiovascular diseases. Isolated LAFB was thought to be benign but has recently been linked to higher risks for heart diseases.
Left posterior fascicular block, LPFB, is much less common than LAFB, probably due to the fact that it is bigger in diameter, has better blood supply, and runs through a more protected area.
In LPFB, the initial vector follows the intact anterior fascicle, which goes upward and leftward, producing a small positive deflection, small r, in lateral leads; and a small negative deflection, small q, in inferior leads. As impulses spread to the rest of the ventricle, the major vector directs downward and to the right, producing a big R in inferior leads, big S in lateral leads; and a right-ward shift in the cardiac axis. LPFB is almost always associated with coronary artery disease, especially myocardial infarction of the inferior wall.
Bifascicular block is blockage of any 2 of the 3 fascicles: left anterior, left posterior and right bundle branch. The term is usually used to describe right bundle branch block plus LAFB, or LPFB. The ECG patterns reflect both conditions.
The term “trifascicular block” means blockage of all 3 fascicles, which would equal to a complete heart block. In practice, however, it is used to refer to a variety of situations, including: a bifascicular block plus a first-degree or second-degree AV block; a right bundle branch block plus alternating LAFB and LPFB; alternating right and left bundle branch blocks; and bifascicular block plus third-degree AV block.
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I have watched a thousand videos and this is just the best
You are one of the greatest in medical video section🔥❤💐
Thank you for making this video. As an ER Nurse of all the rhythms I studied these have always puzzled me when I read the ekg interpretation. I will now have to breakout fresh Qcards and study the deflections created as you explained them. The video illustration HELPED A LOT!!!!
This is by far the best presentation 👍🏻👍🏻
Thank you, finally good clear explanation which I couldn't find in polish educational videos.
Glad it was helpful!
Wonderful explanation. This topic was a bother but your video helped me understand everything. Thank you!
You're very welcome!
Great video!
I had a PVC ablation at my left coronary cusp resulting in permanent LAFB. Cool to know what’s actually happening electrically.
Is the LPFB life threatening
@@650tonyd yes , you have it?
How have you been doing i just got diagnosed RBBB,left anteriorFB,bificicular block ,and i am freaking out.
@@dinobambino2539 hey buddy how are you doing now?
Great Job!!! Thank you so much for creating such content...Be blessed
amazing explanation!
Nice presentation
Very good and excellent explanation...good job...👍👍
Thank you for this
appreciate your video.. please continue
Great channel
Thanks
Nice... Thanks
Good video
Great ,... Thank you so much ❤️
That was awesome
isn't the anatomy in this video completly wrong? What you're showing as the left posterior branch is in every other anatomy book the left anterior branch and vice versa.
Why is there left axis deviation in lafb? The part of the left branch does not work both in lafc and lpfb should it not be in both right axis deviation? Best regards.
Hello, I have a question about my situation. I was born with a congenital heart defect called partial AV canal and had 2 open heart surgeries when I was a child.
Now I am 33 years old and my ECG shows these electrical conduction defects:
- first degree atrioventricular block (PR max 244 ms)
- complete right branch block (QRS 142 ms)
- left anterior hemiblock.
I also add that on the echocardiogram my ejection fraction is 60%. The cardiologist says that for the moment there is no need to wear a pacemaker because the heart is working well, but I would also like your opinion.
Thank you so much 😊
is this fascicular block harmful/danger? or can cause heart attack?
Me too diagnosed with it 🥲
Please post a animated video of PSVT
It's here: ua-cam.com/video/gYfwk1fO0WQ/v-deo.html
I was told I have right Axis deviation but my ECG report says "diagnosis LPFB" I'm scared
Same here bro
@Phat Pat Fitness from what I understand it's not that common. What they're telling me now is that the abnormal reading was caused by a faulty lead
Great explanation! Though i have one question. In LPFB, why does the initial electrical signal through the intact left anterior fascicle creates a small r in lateral leads but a small q in inferior leads? Where did the q for lateral leads go? Thanks!
...first deflection in the same direction to the cardiac vector is always "r" wave ... ( q wave is always the first direction "opposite" the cardiac vector )...
❤
now I know how septal depolarization vector separate from rest of the ventricular depolarization
This idea might be correct but the drawing of the anterior and posterior fascicles is so disorienting in space that practically this video is actually useless for actual learners
thank you! I'm so confused with the drawing, it doesn't match my anatomy book at all