A report on Atrioventricular block

Representative electrocardiogram recordings of the different degrees of heart block
Electrical conduction pathway of the heart.
Normal ECG tracing for a single contraction of the heart.
ECG tracing in relation to normal depolarization and contraction of the heart. Red tracing indicates pathway of electrical depolarization. Blue tracing indicates resulting ECG tracing.

Type of heart block that occurs when the electrical signal traveling from the atria, or the upper chambers of the heart, to ventricles, or the lower chambers of the heart, is impaired.

- Atrioventricular block
Representative electrocardiogram recordings of the different degrees of heart block

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St. Jude Medical single-lead pacemaker with ruler (released in 2005 )

Artificial cardiac pacemaker

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Medical device that generates electrical impulses delivered by electrodes to the chambers of the heart either the upper atria, or lower ventricles to cause the targeted chambers to contract and pump blood.

Medical device that generates electrical impulses delivered by electrodes to the chambers of the heart either the upper atria, or lower ventricles to cause the targeted chambers to contract and pump blood.

St. Jude Medical single-lead pacemaker with ruler (released in 2005 )
An ECG in a person with an atrial pacemaker. Note the circle around one of the sharp electrical spikes in the position where one would expect the P wave.
An ECG of a person with a dual chamber pacemaker
ECG rhythm strip of a threshold determination in a patient with a temporary (epicardial) ventricular pacemaker. The epicardial pacemaker leads were placed after the patient collapsed during aortic valve surgery. In the first half of the tracing, pacemaker stimuli at 60 beats per minute result in a wide QRS complex with a right bundle branch block pattern. Progressively weaker pacing stimuli are administered, which results in asystole in the second half of the tracing. At the end of the tracing, distortion results from muscle contractions due to a (short) hypoxic seizure. Because decreased pacemaker stimuli do not result in a ventricular escape rhythm, the patient can be said to be pacemaker-dependent and needs a definitive pacemaker.
Right atrial and right ventricular leads as visualized under x-ray during a pacemaker implant procedure. The atrial lead is the curved one making a U shape in the upper left part of the figure.
Single-chamber VVIR/AAIR pacemaker
Dual-chamber DDDR pacemaker
Three leads can be seen in this example of a cardiac resynchronization device: a right atrial lead (solid black arrow), a right ventricular lead (dashed black arrow), and a coronary sinus lead (red arrow). The coronary sinus lead wraps around the outside of the left ventricle, enabling pacing of the left ventricle. Note that the right ventricular lead in this case has two thickened aspects that represent conduction coils and that the generator is larger than typical pacemaker generators, demonstrating that this device is both a pacemaker and a cardioverter-defibrillator, capable of delivering electrical shocks for dangerously fast abnormal ventricular rhythms.
Posteroanterior and lateral chest radiographs of a pacemaker with normally located leads in the right atrium (white arrow) and right ventricle (black arrowhead), respectively.
Two types of remote monitoring devices used by pacemaker patients
In 1958, Arne Larsson (1915–2001) became the first to receive an implantable pacemaker. He had 26 devices during his life and campaigned for other patients needing pacemakers.
Illustration of implanted cardiac pacemaker showing locations of cardiac pacemaker leads
The first lithium-iodide cell-powered pacemaker. Invented by Anthony Adducci and Art Schwalm. Cardiac Pacemakers Inc. 1972

Where the problem is atrioventricular block (AVB) the pacemaker is required to detect (sense) the atrial beat and after a normal delay (0.1–0.2 seconds) trigger a ventricular beat, unless it has already happened – this is VDD mode and can be achieved with a single pacing lead with electrodes in the right atrium (to sense) and ventricle (to sense and pace).

Sinus bradycardia seen in lead II with a heart rate of about 50BPM

Bradycardia

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Slow resting heart rate, commonly under 60 beats per minute (BPM) as determined by an electrocardiogram.

Slow resting heart rate, commonly under 60 beats per minute (BPM) as determined by an electrocardiogram.

Sinus bradycardia seen in lead II with a heart rate of about 50BPM
Illustration comparing the ECGs of a healthy person (top) and a person with bradycardia (bottom): The points on the heart where the ECG signals are measured are also shown.

This dysrhythmia also may occur when the electrical impulses from the SA node fail to reach the AV node because of SA or AV block.

ECG showing types of heart block

Heart block

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Disorder in the heart's rhythm due to a fault in the natural pacemaker.

Disorder in the heart's rhythm due to a fault in the natural pacemaker.

ECG showing types of heart block
Conduction system of the heart
Sinus rhythm with acute inferior infarction complicated by Type I AV block manifest in the form of 5:4 Wenckebach periods; R-P/P-R reciprocity.
Sinus tachycardia with complete AV block and resulting junctional escape

Blockages are therefore classified based on where the blockage occurs - namely the SA node ("Sinoatrial block"), AV node ("AV block" or AVB), and at or below the bundle of His ("Intra-Hisian" or "Infra-Hisian block" respectively).

Skeletal formula of propranolol, the first clinically successful beta blocker

Beta blocker

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Beta blockers, also spelled β-blockers, are a class of medications that are predominantly used to manage abnormal heart rhythms, and to protect the heart from a second heart attack after a first heart attack (secondary prevention).

Beta blockers, also spelled β-blockers, are a class of medications that are predominantly used to manage abnormal heart rhythms, and to protect the heart from a second heart attack after a first heart attack (secondary prevention).

Skeletal formula of propranolol, the first clinically successful beta blocker
Dichloroisoprenaline, the first beta blocker

AV block

Image showing the conduction system of the heart. The AV node is labelled 2.

Atrioventricular node

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Part of the electrical conduction system of the heart.

Part of the electrical conduction system of the heart.

Image showing the conduction system of the heart. The AV node is labelled 2.
Isolated heart conduction system showing atrioventricular node

Atrioventricular conduction disease (AV block) describes impairment of the electrical continuity between the atria and ventricles. It occurs when the atrial depolarization fail to reach the ventricles or is conducted with an abnormally long delay. It can result from an injury or be a genetically inherited disorder.