Understanding Intraventricular Block: A Comprehensive Guide
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Overview
Understanding Intraventricular Block: A Comprehensive Guide
Overview
Intraventricular block, also known as intraventricular阻滞, is a condition characterized by conduction delay or blockage in the His bundle and below. This article provides a comprehensive overview of the condition, including its diagnosis and treatment.
What is Intraventricular Block?
Intraventricular block refers to the conduction delay or blockage in the His bundle and below, which is part of the ventricular conduction system. This system is composed of the right bundle branch, left anterior fascicle, and left posterior fascicle. The condition can affect one, two, or all three branches, with right bundle branch block being the most common type.
Common Causes
Intraventricular block can be caused by various conditions, including:
- Cardiomyopathies
- Congestive heart failure
- Acute myocardial infarction
- Rheumatic heart disease
- Hypertensive heart disease
- Coronary artery disease
- Myocardial infarction
- Congenital cardiovascular disease
- Pulmonary embolism
Diagnosis
The diagnosis of intraventricular block involves clinical evaluation and electrocardiogram (ECG) analysis. Symptoms may include:
- Systolic ejection murmur
- First and second heart sound splitting
- Arrhythmias
ECG findings can include:
- Right bundle branch block (RBBB): QRS duration ≥ 0.12 seconds, with rsR' pattern in V1-V2 and qRS pattern in V5-V6.
- Left bundle branch block (LBBB): QRS duration ≥ 0.12 seconds, with R waves broad in V5-V6 and QS or rS waves in V1-V2.
- Left anterior fascicle block: Leftward deviation of the mean QRS electrical axis between -45° and -90°.
- Left posterior fascicle block: QRS duration < 0.12 seconds with qR pattern in I, aVL and rS pattern in II, III, aVF.
- Bifascicular block: Conduction block in any two branches of the intraventricular conduction system.
- Trifascicular block: Conduction block in all three branches of the intraventricular conduction system.
It is important to differentiate intraventricular block from other conditions that can cause similar ECG changes, such as right ventricular hypertrophy, emphysema, and lateral myocardial infarction.
Treatment
The treatment of intraventricular block depends on the severity of symptoms and the underlying cause. In most cases, chronic unilateral bundle branch block without symptoms does not require treatment. However, patients with double bundle block or incomplete trifascicular block may be at risk for developing complete heart block, and may benefit from preventive pacing therapy.
For patients with acute anterior wall myocardial infarction and conduction blocks, or those with chronic double or trifascicular block associated with syncope or Adams-Stokes syndrome, early pacing therapy is recommended. It is important to note that pacing therapy in intraventricular block is less effective than in atrioventricular block, as the pacing site is below the conduction system, resulting in a slower and less stable pacing rate.
Conclusion
Intraventricular block is a condition that requires careful evaluation and management. Early diagnosis and appropriate treatment can improve outcomes for patients with this condition.