The third degree atrioventricular block may rarely be asymptomatic, more often having hypoperfusion- related symptoms, such as fatigability, chest pain, dyspnea, dizziness, irritability, apathy, inability to concentrate, forgetfulness, confusion. In severe cases, syncope and sudden death occur.

Facing a patient with associated symptoms like severe chest pain, nausea, dyspnea and diaphoresis, the clinician should consider an acute myocardial infarction as the cause of the complete heart block [1]. On the other hand, chronic cardiac patients undergo different kinds of treatment that have a potential to induce heart block: digitalis, calcium channel blockers, beta blockers and medication that can induce hyperkalemia, like angiotensin-converting enzyme inhibitors and angiotensin receptor blockers.

In addition to symptoms caused by the heart block, patients may have complaints linked to the cause of the block, like ischemia, myocarditis, hypothyroidism, cardiomyopathy, hypothermia and electrolyte disturbances [1]. Children with congenital third degree atrioventricular block may be symptomatic from birth [2].

In a patient with very low heart rate, the stimulus probably originates in the ventricles and is not due to a junctional pacemaker thus having a poor prognosis [3].

The physical examination of third degree atrioventricular block patients will often show signs of decreased perfusion and those of underlying disease.

Inspection may show turgescent jugular veins and cannon " a" waves caused by the contraction of the right atrium against the closed tricuspid valve, peripheral edema or skin rashes if the cause of the block is Lyme disease, endocarditis, or rheumatic fever.

Palpation may reveal hepatomegaly in heart failure patients, while auscultation reveals pulmonary rales, variable first heart sound, murmurs caused by mitral or aortic calcification or cardiomyopathies and a low heart rate. Arterial pressure may be low.

Blood workup should include a complete blood cell count (in order to diagnose infection and anemia), renal function, electrolytes (especially potassium, given that hyperpotassemia is a cause of third degree atrioventricular block by itself), prothrombin time, activated partial thromboplastin time (having in mind that emergency cardiostimulation may be necessary) and digoxin level. If myocarditis is suspected, every effort should be put into determining its cause: human immunodeficiency virus infection, Lyme disease, adenovirus or enterovirus infection.

A chest radiograph may offer clues about the cardiac silhouette and possible associated pneumonia. Transthoracic echocardiography may find aortic and mitral calcification or abscesses, hypertrophic cardiomyopathy and left ventricle systolic function.

The diagnosis is established using a 12 lead electrocardiogram, showing complete atrioventricular dissociation [4], with constant R-R intervals and either narrow (<120 msec) or wide ventricular complexes, depending on the site of the stimulus: atrioventricular junction, His bundle or ventricular myocardium. The atrial rate is faster than the ventricular one, which is usually 30-40 beats per minute. The electrocardiogram may also show ischemia, in which case cardiac enzymes should be measured and coronarography should be performed. Anterior myocardial infarctions complicated with complete atrioventricular block have higher instability risk [2]. A complete atrioventricular block is the most frequent bradyarrhythmia in myocardial infarctions [5].

If symptoms are intermittent and the electrocardiogram shows no abnormalities when the patient presents, an ambulatory monitoring or loop recorder is indicated [6] [7]. Furthermore, an electrophysiological study may be useful in cases where the origin of the stimulus is uncertain or in cases where symptoms seldom occur [8].

Other tests, like tilt table testing and carotid sinus massage, are to be performed in cases where the more plausible diagnosis is reflex syncope, not intermittent third degree atrioventricular block. If a patient only has symptoms after performing an effort, exercise testing is called for.

The primary treatment for Third Degree AV Block is the implantation of a pacemaker. A pacemaker is a small device placed under the skin that helps regulate the heart's rhythm by sending electrical impulses to the heart muscle. In emergency situations, temporary pacing may be required until a permanent pacemaker can be implanted. Medications may also be used to manage symptoms or underlying conditions contributing to the block.

With appropriate treatment, the prognosis for patients with Third Degree AV Block is generally good. A pacemaker can effectively manage the condition, allowing patients to lead normal, active lives. However, if left untreated, the block can lead to serious complications, including heart failure or sudden cardiac arrest.

Third Degree AV Block can result from a variety of causes, including age-related degeneration of the heart's electrical system, heart disease, or damage from a heart attack. Other potential causes include certain medications, infections, or congenital heart defects. In some cases, the exact cause may remain unknown.

Third Degree AV Block is more common in older adults, as the risk of developing heart conduction problems increases with age. It is relatively rare in younger individuals unless associated with congenital heart defects or other underlying conditions. The prevalence of the condition varies globally, influenced by factors such as healthcare access and population demographics.

In Third Degree AV Block, the electrical signals generated by the sinoatrial (SA) node in the atria are unable to reach the ventricles due to a complete block in the AV node or the His-Purkinje system. This results in the atria and ventricles beating independently, with the ventricles often adopting a slower, escape rhythm. This disconnection disrupts the heart's ability to pump blood efficiently.

Preventing Third Degree AV Block involves managing risk factors for heart disease, such as maintaining a healthy lifestyle, controlling blood pressure and cholesterol levels, and avoiding medications that can affect heart conduction. Regular check-ups with a healthcare provider can help detect early signs of conduction problems and prevent progression to complete heart block.

Third Degree AV Block is a serious heart condition characterized by a complete disconnection between the heart's atria and ventricles. It can lead to significant symptoms and complications if untreated. Diagnosis is primarily through ECG, and treatment typically involves pacemaker implantation. With proper management, patients can have a good quality of life.

If you or someone you know is diagnosed with Third Degree AV Block, it's important to understand that this condition affects the heart's ability to beat properly. Symptoms like dizziness or fainting occur because the heart isn't pumping blood effectively. Treatment usually involves a pacemaker, a device that helps keep the heart beating regularly. With a pacemaker, most people can continue their daily activities without major restrictions. Regular follow-ups with a healthcare provider are essential to ensure the pacemaker is functioning correctly and to monitor overall heart health.

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