Bradyarrhythmia:- After everyone has learned normal conductivity It now enters abnormal electrical conduction in those whose heart beats more slowly than normal. Most bradyarrhythmia is the inactivity of the conduction system or the impedance of the conduction. Causing its conduction to be delayed.
Therefore the mechanism of bradyarrhythmia can be divided into 3 main positions. Just the occurrence of the sinoatrial (SA) node, atrioventricular (AV) node, and bundle branches.
Sinoatrial Node Dysfunction
Besides vagal activity which is the main cause of bradyarrhythmia. Cellular abnormalities in the conduction system can also cause bradyarrhythmia. The ECG image of the SA node dysfunction is that the electrocardiogram will remain completely for a while and then return to normal. Still, the missing period is collectively referred to as sinus pause or sinus arrest. Ie disappearing since “P-wave” so we use the term sinus. Can come from the following 3 types
The first is parasympathetic activity. Especially at bedtime Born normally And even in a dog or cat that has a problem. Brachycephalic airway respiratory sinus arrhythmia.
The second type is called the sinus pause. The pause is actually the sinus node stopped. Which may be caused by an abnormal lesion in the SA node itself.
The last type is called the sinoatrial exit block, that is, the SA node still works to produce impulse. But the rhythm will send a signal to other heart muscles to be blocked. Stopping of the ECG is the stopping of all myocardial contractions. The fear is that the blood doesn’t feed the brain, just for a short while it leads to collapse or syncope. A sinus node dysfunction called sick sinus syndrome (SSS).
Atrioventricular Block or AV Block
We actually had the opportunity to know AV block for a long time. Plus I know that there are 3 levels to indicate the severity that there is a chance that problems will follow or not. And should it be treated or not? As for how to interpret results Would like to explain as follows.
First Degree AV Block
This type of P-QRS-T will still be seen in a fairly normal sequence, most have a slower heart rate. But the keyword is having a longer PR interval (dogs greater than 0.13 s, cats). More than 0.09 s), first-degree AV block does not usually cause symptoms. Most often due to the work of excessive parasympathetic.
Second Degree AV Block
This one looks more serious, but we can see the normal P-QRS-T with P-wave that is not followed by QRS-T. The severity in the second degree is divided into 2 levels: Mobitz type 1. And type 2, if the theory is split, it is type 1, we can see the normal P-QRS-T. But the PR interval is longer and longer until the block is formed. There is P but no QRS followed. But in this case, Type 2 has a fixed ratio, which is the ratio of normal beat to block the occurrence of one time. Which is somewhat more severe Because the frequency of block occurrences is more frequent than type 1.
Third-Degree AV Block
Also known as complete block, we can see the P wave and QRS complex dancing separately. Atrium and ventricle, different people dance. This is quite dangerous because it has the potential to easily cause syncope. As there is a chance that the blood flow in the heart is insufficient to squeeze out through the body.
In both cases of second-degree and third-degree AV block. Lesions are often present in myocardial cells and cause syncope. As there may be an unrelated rhythm in the upper and lower atria. Resulting in decreased blood output from the heart. Both cases can suggest the owner on remediation by implanting a pacemaker.
Bundle Branches Block
It is said that the bundle branch continues. That is the conductors that extend from the AV node down the interventricular septum. And pass it on to the Purkinje system and ventricles. If the bundle branch block is interrupted for any reason. The ECG will change in appearance, ie, the heart rate may be reduced (or normal). P-wave (because the SA node is still active and Can send the signal to the AV node) that looks normal. But the timing to continue transmitting signals to the ventricles takes a little longer. Because they go through normal conduction. Little by little gap junction is required from the heart muscle. So the QRS is wider than normal.
In short, to look at the bundle branch block. That is if you see a wide anomalous QRS when reading an ECG. See if before the complex there was a P-wave. If so, then it might not actually be a ventricular origin, but a sinus origin where a bundle branch block has occurred.
As for the appearance of each type of block, I would like everyone to review and understand which block is what happens and what follows, and easily remember which block the MEA would go that way. In the next issue, we will come into the story. Tachyarrhythmia Both in terms of interpreting results and interpreting each other