Alterations in heart rhythm and heart rate are common. Fortunately, in many cases, they do not pose any kind of problem.
What is arrhythmia?
First of all, arrhythmia is an alteration with no physiological explanation but affects both the heart frequency and rhythm. Remember, frequency refers to the number of beats per minute and the rhythm can be regular or irregular. So, arrhythmia is a disorder that affects the heart rate or frequency.
If for some reason you become nervous and your heart rate increases, it is not necessarily pathological. In reality, it simply means the frequency increases due to tension caused by nervousness. For example, while feeling threatened.
On the other hand, if “for no reason” alterations occur, i.e. not finding an actual reason for an increase in frequency, then it is considered pathological. In such case, you should go to the doctor for further comprehensive testing. After all, an arrhythmia can either be an increase or decrease in frequency or an alteration in normal heart rhythm.
Arrhythmias derive from:
- Heartbeat rhythm disorders.
- Cardiac conduction alterations.
- A combination of both.
Tachyarrhythmia is a minimum three beat sequence at a frequency greater than 100 beats/min. Depending on their point of origin, they divide into:
- Supraventricular: originates above the bundle of His. Narrow QRS complexes appear (<0.12 sec) on electrocardiogram.
- Ventricular: originates below the bundle of His. Wide QRS complexes (> 0.12 sec) appear on electrocardiogram.
Atrial extrasystole occurs as a result of an ectopic focus in the atrium. An advanced depolarization happens, which in turn produces a “premature” heartbeat. After the ectopic beat, there is, then, a brief pause followed by a normal beat. An impulse at the atrioventricular node level causes atrioventricular extrasystole. Consequently, ventricles activation is normal while atria activate in retrograde.
After the ectopic beat, there is a compensatory pause, followed by a normal beat. Extrasystoles are very common. In fact they are the most frequent type of arrhythmia. They usually do not pose any kind of problem and do not require treatment.
- Sinus tachycardia is a normal response to many situations, such as exercise, anxiety, pain, fever, caffeine consumption, among others. You do not need to specifically treat tachycardia, only its cause. Sinus tachycardia simply increases the frequency at which the beats occur. In this case, the heartbeats originate in the sinus node, our “real pacemaker”, but at a frequency greater than 100 beats/min.
- Atrial tachycardia — also known as a “heating phenomenon” — originates in the atrial ectopic focus, and its triggering frequency is above normal. This causes the normal focus to be inhibited and the ectopic focus to “take over” producing the heartbeat. This is a very peculiar process. The heart rate progressively increases, reaches its maximum, and then decreases. Treatment includes beta-blockers or calcium antagonists.
- Ventricular tachycardia originates from an ectopic focus below the His bundle. The main cause of ventricular tachycardia is an old myocardial infarction.
Atrial fibrillation, the most common type of extrasystolic arrhythmia, consists of ineffective atrial contractions resulting from very fast, disorganized and desynchronized rhythm. Blood stagnates as the atria do not contract normally.
- Blood pooling (stasis) increases the risk of blood clots which increases the risk of embolism. In fact, atrial fibrillation (AF) is the primary cause of embolism (pulmonary embolism, cerebral stroke …)
- When ventricles do not fill up properly, the amount of blood pumped by the heart to the body decreases.
- Finally, as blood builds up, pressure inside the atria increases leading to possible pulmonary edema.
- Re-establish sinus rhythm and slow down the ventricles.
- Prevent embolisms.
- Prevent arrhythmic episodes.
Either electrical or pharmacological cardioversion can re-establish sinus rhythm. Once the rhythm is under control, beta-blockers help control the frequency. Additionally, anticoagulants or antiplatelets drugs can play a role in preventing embolisms. Antiarrhythmic drugs help prevent recurrence.
Ventricular fibrillation usually results from rapid and repeated ventricular tachycardia. Hence, a disorganized, rapid and completely ineffective rhythm appears, which then leads to asystole and death within a few minutes.
Time is of the essence. If there is no defibrillator available, then performing manual CPR is necessary until one is available. In this video, you can see how to perform CPR. That’s why immediate electrical defibrillation is necessary to keep the patient alive.
SINUS BRADYARRHYTHMIA: SICK SINUS SYNDROME
A decrease in heart rate below 60 occurs due to sinus node alteration, the “cardiac pacemaker”. Damage to the sinus node happens due to:
- Pharmacological damage.
- Chagas disease.
- Some systemic diseases, such as hypothyroidism.
This happens where there is a delay in electrical impulse transmission between the atria and ventricles. Arrhythmias are classified according to the degree of severity, from one to three:
- First-degree blockage: decreases the impulse transmission speed without blockage.
- Third-degree blockage: complete blockage of electrical impulses. The atria of the ventricles are “disconnected”. The symptoms will depend on whether an “escape rhythm” is set in motion. It consists of the production of beats below blockage point, which allows the cardiac cycle to continue. A pacemaker will be necessary.
- Second-degree blockage: partial impulse blockage. There are two types, block type 1, Mobitz 1 or Wenckebach, and block type 2 or Mobitz 2.
- TYPE ONE: transmission speed decreases progressively until the transmission blockage of one or more of them takes place. Thus, normal rhythm returns. It is considered benign and asymptomatic.
- TYPE TWO: Sudden blockage appears. It is less frequent, but even more serious since it can result in complete blockage. This blockage can follow a specific sequence or may vary. Normally, a pacemaker needs to be placed.
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