Cardiac Arrhythmias: Causes, Symptoms and Treatment

Arrhythmia is a medical term that refers to a condition where the heart's rhythm is abnormal. This could mean that the heart beats too quickly, a condition known as tachycardia, too slowly, referred to as bradycardia, or irregularly, a condition known as atrial fibrillation. This deviation from the average heart rate can range from harmless to life-threatening, potentially leading to death in a short period.

The Heart and Its Unique Properties

For a comprehensive understanding of arrhythmias, it's crucial to appreciate the unique properties of the heart, particularly its ability for self-contraction. The myocardium, or heart muscle tissue, contains cells that possess two unique properties: automaticity and rhythmicity.

Automaticity refers to the cells' ability to initiate the contraction activity spontaneously and involuntarily, generating the nervous impulse independently. This is a significant departure from how other muscle cells in the body operate, which typically require a signal from the brain to initiate contraction.

Rhythmicity, on the other hand, refers to the regularity and orderly succession of the nervous impulse. This property ensures that the heartbeats occur in a consistent and rhythmic manner.

The myocardial cells responsible for automaticity and rhythmicity are grouped in certain areas of the heart, known as pacemakers or pacemaker centers. The first pacemaker center, known as the sinoatrial node (SA node), is considered the dominant one as it is the primary point of origin of the impulse. The subsequent points, which serve to conduct the contraction signal, are the atrioventricular node (AV node), the bundle of His, and the Purkinje fibers.

Classification of Cardiac Arrhythmias

Cardiac arrhythmias can be classified based on the nature of the alterations in the heart's rhythm.

There are three main types of alterations:

  1. Changes in the frequency and regularity of sinus rhythm: These result in tachycardias (increased heart rate) and bradycardias (decreased heart rate).
  2. Change in the location of the dominant pacemaker center: This occurs when the sinoatrial node loses its automaticity, leading to its replacement with a secondary pacemaker center.
  3. Impulse propagation disorders: These occur due to a slowing down or stopping of the impulse during its journey from the dominant pacemaker center to the secondary centers.

Arrhythmias can also be classified based on the site of origin of the disorder. These include sinus arrhythmias, which affect the impulse coming from the sinoatrial node, and ectopic arrhythmias, which affect a pacemaker other than the sinoatrial node.

Causes of Cardiac Arrhythmias

Arrhythmias can be caused by different pathological processes affecting the heart, such as myocardial infarction, heart failure, pericarditis, and valvular heart disease. However, it's important to note that the presence of arrhythmia does not always indicate a cardiovascular disease. This condition can also be secondary to general diseases of the body, such as iatrogenic intoxications, endocrine dysfunctions, and electrolyte imbalances in the blood, particularly those involving potassium and calcium.

On some occasions, arrhythmia is simply a functional disorder, an expression of alterations in the neurovegetative balance, particularly in anxious and neurotic individuals. Factors like physical exertion and the abuse of stimulants, such as coffee and tobacco, can increase, through the sympathetic system, the excitability of the myocardial cells, causing extrasystoles or sinus tachycardias.

Symptoms of Cardiac Arrhythmias

The clinical picture associated with arrhythmias can manifest in different ways. Some individuals might experience palpitations and an irregular perception of their heartbeat, while others might experience symptoms of ischemic suffering, such as angina pectoris, or low flow rate, including dizziness, hypothymia, and fainting.

Diagnosis of Cardiac Arrhythmias

Diagnosing cardiac arrhythmias typically involves a cardiological examination and an electrocardiogram (ECG) to check the heart's activity. In some cases, a dynamic electrocardiogram according to Holter may be used to monitor the patient for 24-48 hours, particularly if the individual presents sporadic arrhythmic episodes.

Treatment of Cardiac Arrhythmias

The treatment for cardiac arrhythmias depends on the underlying cause. Common therapeutic interventions include the administration of beta-blockers and calcium channel blockers to slow down the heart rate, antiarrhythmics to stabilize the heart rhythm, and anticoagulants to thin the blood and prevent clot formation.

In some cases, surgical interventions may be necessary. These can include electrical cardioversion, radiofrequency ablation, and the implantation of a pacemaker or defibrillator. Lifestyle changes, such as quitting smoking or reducing caffeine intake, may also be beneficial.

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