Atrioventricular Dissociation: An Overview

Introduction

Four chambers make up the heart, which is divided into two, right and left, that pump blood to the pulmonary and systemic circulations. Through the superior and inferior vena cavae, deoxygenated blood from every part of the body (apart from the lungs) is delivered to the right atrium and oxygenated blood flows from the lungs into the left atrium. The chambers of the heart in the superior position are called the atrium, and the chambers of the heart below are called ventricles.

What Is AV Dissociation?

Atrioventricular dissociation is a defect in the cardiac conduction of the heart. In this condition, both the upper and lower chambers of the heart do not work in synchrony. This is due to an abnormal impulse from the sinoatrial node to the atria causing AV node dissociation. An atrioventricular dissociation ECG (electrocardiograph) finding is necessary to validate the source of the ongoing pathology. Atrioventricular dissociation or AV refers to a group of heart rhythm abnormalities called arrhythmias, where self-sufficient pacemakers take hold of atria and ventricles.

A pacemaker is a miniature machine that helps in controlling arrhythmias. The SA node, or the sinoatrial node, is the primitive location in the atrium that starts a heartbeat. The AV node, or the atrioventricular node, controls the electrical signals of the heart that pass from the atrium to the ventricles. The HPS or the His-Purkinje system is in charge of the electrical impulse conduction in the ventricles. Thus, a typical cardiac circuit is activated and begins the transmission of impulses from the sinoatrial node to the heart's upper chamber, then the atrioventricular node, and finally, the His-Purkinje system that activates the lower chamber of the heart.

Interference in this pathway leads to dissociation of the impulse transmission of the atria and ventricles. When this happens, multiple cardiovascular conditions arise. One of the most severe complications of atrioventricular dissociation is a total blockage of the heart.

What Causes Atrioventricular Dissociation?

Elderly patients with comorbidities and other cardiovascular conditions of degenerative nature are more prone to atrioventricular dissociation.

The causes of AV dissociation are the following -

• Disruptions in the standard atrioventricular pathway include interferences between the atrioventricular node, the sinoatrial node, and His-Purkinje signals.

• Abnormally high pulse rate due to increased activity in the lower chambers of the heart (ventricles) called ventricular tachycardia.

• High vagal tone (quick return to calm state after stressful situations).

• The rate of impulse transmission starting from the sinoatrial node may be slowed down, leading to sinus bradycardia or other antiarrhythmic medications.

• A complete heart block due to interruption of conduction between the sinoatrial nodes and the ventricles.

What Are the Signs and Symptoms of Atrioventricular Dissociation?

Clinical presentation of patients suffering from atrioventricular dissociation varies from case to case. This is chiefly due to the differences in the underlying cardiovascular conditions.

The following are some of the warning signs and symptoms:

• Syncope.

• Difficulty in breathing.

• Chest discomfort or chest pain.

• Lightheadedness.

• Tachycardia.

• Dizziness.

• Bradycardia.

• Abnormal heart murmurs.

What Is the Treatment for Atrioventricular Dissociation?

Finding the underlying cause of cardiovascular disease will directly help in the treatment and planning for atrioventricular dissociation.

• If the atrioventricular dissociation results from ventricular tachycardia, then arresting the arrhythmias will be the solution.

• Digitalis toxicity, the reason for atrioventricular tachycardia, must be treated with a suitable antidote.

• Termination of junctional arrhythmia should be treated with precaution because it is susceptible to ward off the primary source of conduction completely.

• Antibiotics can help if Lyme carditis is the cause, and this is usually self-limiting.

• Potassium replacement therapy is another well-known treatment modality for atrioventricular dissociation.

• Transcutaneous pacemakers are the most immediate way to stabilize cardiac pace.

• Transvenous pacemakers are also a choice if a transcutaneous pacemaker fails in mechanical or electrical capture.

What Are Pacemakers?

A pacemaker is a mini machine implanted or lodged within the patient's chest that helps control the heartbeat. A permanent pacemaker is a good treatment choice for atrioventricular dissociation.

There are currently three types of permanent pacemakers as follows -

• Pacemakers for single chambers with a single lead in the right atrium or the left ventricle.

• Pacemakers for two chambers with two lead lodges in the right ventricle and atrium are called dual-chamber pacemakers.

• Dual-chamber with an additional lead extending to the coronary sinus for left ventricular pacing. This type of pacemaker is called a biventricular pacemaker.

Among the above three types of pacemakers, the dual-chamber or the pacemaker for two chambers is the one that is generally effective in the correction of atrioventricular block. However, recent studies show that heart failure incidents can be drastically reduced by putting into work the third type of pacemaker, the biventricular pacemaker.

What Are the Complications of Atrioventricular Dissociation?

Unless the heart gets blocked, atrioventricular dissociation is generally transient. The diagnosis is made with the aid of an electrocardiogram. Also, understanding the presence of an ongoing cardiovascular disease should be determined because correcting this underlying condition will eventually eliminate the presence of atrioventricular dissociation. Additionally, knowing the patient's underlying history of cardiovascular disease makes the healthcare provider more alert and aware of the risks and complications they may need to face. If atrioventricular dissociation is not treated, it can lead to severe complications such as myocardial dysfunction, malfunctioning cardiac muscles, or even renal failure.

How Can the Patient Be Educated About Atrioventricular Dissociation?

Patients who show symptoms need to undergo rigorous training and understand this condition. This is mainly because most of the patients are aged and of the senile group who lack a sense of responsibility or memory or even due to lack of support. Agents that are offending the patient's life should be removed. Patients must be counseled to report to the healthcare provider about their signs and symptoms. Additionally, the warning signs, dosage limits, and other beneficial keynotes must be educated and taught to the patients.

Conclusion

Atrioventricular dissociation is when the upper and lower chambers of the heart work independently. The patients should be informed about the risks of these conditions so that in case there are any signs or symptoms, they can report them to their doctors. With prompt warning, this condition can be treated with a focus on eradicating the underlying cardiac issues. The diagnosis of atrioventricular dissociation is challenging. Patients may first have vague signs and symptoms or, on rare occasions, may even be asymptomatic. Close cooperation is necessary to stabilize a patient who is experiencing hemodynamic collapse or severe sinus bradycardia. Although the causes of AV dissociation affect the treatment options, a multidisciplinary team approach involving doctors, consulting doctors, nurses with specialized training, and pharmacists is necessary for the best possible patient outcomes.