First degree AV block
Background
- Also known as first-degree heart block
- Defined as prolongation of the PR interval on an electrocardiogram (ECG) to more than 200 msec (5 small squares on the ECG tracing)
- Considered “marked” when the PR interval exceeds 300 msec (more than 7 small squares on the ECG tracing)
Clinical Features
- Vast majority are asymptomatic and diagnosed by chance
- Exercise may reveal decreased tolerance (especially when there is markedly prolonged PR interval and with left ventricular systolic dysfunction)
Differential Diagnosis
AV blocks
- First degree AV block
- Second degree
- Third degree AV block
- AV dissociation without complete heart block
Evaluation
- ECG
- Consider rare causes:
- Lyme's disease
- Lupus
- Myocarditis
- Myocardial infarction
Management
- Asymptomatic patients do not require any specific management
- Consider a cardiology consult for patients who may have symptoms attributable to the block (rare)
Disposition
- Outpatient