The key difference between AV block 1 and 2 is that AV block 1 is due to a delay in the conduction of atrial impulses to the ventricles, while AV block 2 is due to a blocking of the conduction of some of the atrial impulses to the ventricles.
Heart block is also known as AV block. It occurs when the electrical signal that controls the heartbeat is partially or fully blocked. It is categorized into three types; they are AV blocks 1, 2, and 3. AV block 1 is due to the slowing down of the conduction of electrical impulses. AV block 2 is due to the blocking of the conduction of some electrical impulses, while AV block 3 is due to the full blocking of the conduction of electrical impulses or a complete loss of communication between the atria and the ventricles.
CONTENTS
1. Overview and Key Difference
2. What is AV Block 1
3. What is AV Block 2
4. Similarities – AV Block 1 and 2
5. AV Block 1 vs. 2 in Tabular Form
6. Summary – AV Block 1 vs. 2
What is AV Block 1?
AV block 1 is defined as a delay in the conduction of electrical impulses from the atria to the ventricle without interruption. On ECG, it is detected by the presence of PR interval > 200ms. The symptoms of this condition may include dyspnea, malaise, lightheadedness, chest pain, and syncope due to poor synchronization of atrial and ventricular contractions. AV block 1 can be caused by increased vagal tone, athletic training, inferior myocardial infarction, mitral valve surgery, myocarditis, electrolyte disturbances, and AV nodal-blocking drugs such as beta-blockers, calcium channel blockers, digoxin, and amiodarone.
AV block 1 can be diagnosed through medical history, physical examination, and ECG. Furthermore, treatment options for AV block 1 may include removing provoking medications and monitoring patients on an outpatient basis.
What is AV Block 2?
AV block 2 is also known as a hay heart block. AV block 2 is diagnosed when some atrial impulses (but not all) fail to conduct to the ventricles due to impaired conduction. Therefore, it is a partial conduction block between the atria and ventricles. The sign and symptoms of this condition may include lightheadedness, dizziness, syncope or fainting, chest pain, shortness of breath, feeling tired, nausea, rapid breathing, and heart palpitation. On ECG, AV block 2 is detected by the presence of consecutively conducted beats with the same PR interval, which is followed by a blocked sinus P wave. The causes of AV block 2 are anterior myocardial infarction, idiopathic fibrosis of the conducting system, cardiac surgery, inflammatory conditions such as rheumatic fever, myocarditis, Lyme disease, autoimmune conditions such as SLE, systemic sclerosis, infiltrative myocardial disease, hyperkalemia, and certain drugs like beta-blockers, calcium channel blockers, digoxin, and amiodarone.
AV block 2 can be diagnosed through medical history, physical examination, blood test, ECG, an implantable loop recorder, and an electrophysiology study. Individuals with AV block 2 may receive treatment in the form of pacemaker implantation, a small device designed to ensure the heart beats in its proper rhythm.
What are the Similarities Between AV Block 1 and 2?
- AV blocks 1 and 2 are two types of heart blocks.
- Both are conduction disorders.
- They are not serious as third-degree heart block or AV block 3.
- Both types can be easily managed by immediate medical intervention.
What is the Difference Between AV Block 1 and 2?
AV block 1 is due to a delay in the conduction of atrial impulses to the ventricles, while AV block 2 is due to a blocking of conduction of some of the atrial impulses to the ventricles. Thus, this is the key difference between AV block 1 and 2. Furthermore, on ECG, AV block 1 is detected by the presence of PR interval > 200ms. On the other hand, on ECG, AV block 2 is detected by the presence of consecutively conducted beats with the same PR interval, which is followed by a blocked sinus P wave.
The infographic below presents the differences between AV block 1 and 2 in tabular form for side-by-side comparison.
Summary – AV Block 1 vs. 2
A heart block occurs when there is a disruption in the conduction of electrical impulses that control the beating of the heart muscle. The most serious type of heart block is complete heart block or third-degree (AV block 1). The first-degree (AV block 1) and second-degree (AV block 2) can be managed easily with medical intervention. However, AV blocks 1 and 2 have different aetiologies. AV block 1 is the delay in the conduction of electrical impulses from the atria to the ventricle without interruption, whereas AV block 2 is the blocking of conduction of one or more but not all of the atrial impulses to the ventricles. So, this summarizes the difference between AV block 1 and 2.
Reference:
1. “First-Degree Heart Block.” – Statpearls – NCBI Bookshelf.
2. Ali A Sovari, MD. “Second-Degree Atrioventricular Block.” Practice Essentials, Background, Pathophysiology.
Image Courtesy:
1. “FirstAVBlock” By James Heilman, MD – Own work (CC BY-SA 4.0) via Commons Wikimedia
2. “Heart block” By Npatchett – Own work (CC BY-SA 4.0) via Commons Wikimedia