From the Guidelines
A PR interval of 274ms in a 35-year-old female is not normal and represents first-degree heart block, which warrants medical evaluation. This finding indicates delayed electrical conduction between the atria and ventricles of the heart, as defined by a PR interval greater than 200ms 1. According to the 2019 ACC/AHA/HRS guideline on the evaluation and management of patients with bradycardia and cardiac conduction delay, first-degree atrioventricular block is characterized by a prolonged PR interval, but each P wave is still conducted to the ventricles 1.
Key Considerations
- The normal PR interval range is 120-200ms, and a PR interval of 274ms is considered prolonged 1.
- First-degree heart block is generally considered benign, but it can be caused by various factors, including certain medications, electrolyte abnormalities, increased vagal tone, or underlying heart conditions 1.
- It is essential to schedule an appointment with a cardiologist for further assessment, including a complete ECG and possibly additional cardiac testing to determine the underlying cause of the prolonged PR interval.
Recommendations
- If symptoms like dizziness, fatigue, or syncope are present, they should be mentioned to the doctor, as these may indicate a more significant underlying issue 1.
- The doctor may recommend monitoring the condition over time, especially if asymptomatic, or addressing any contributing factors if identified 1.
- Identifying any underlying cause of the first-degree heart block is crucial, and the cardiologist will determine the best course of action based on the individual's specific condition and medical history 1.
From the Research
First-Degree Heart Block
- A PR interval of 274ms is considered prolonged, as a normal PR interval is typically between 120-200 milliseconds 2.
- First-degree heart block, also known as first-degree atrioventricular (AV) block, is defined as a PR interval exceeding 200 milliseconds 2, 3.
- Studies have shown that individuals with first-degree AV block have a higher risk of adverse cardiovascular outcomes, including atrial fibrillation, heart failure, and mortality 2, 4.
Clinical Significance
- The clinical significance of a prolonged PR interval is still being researched, but it is believed to be associated with an increased risk of arrhythmic events and death 2, 4.
- A study published in the Journal of the American Medical Association (JAMA) found that individuals with a PR interval longer than 200 milliseconds had a higher incidence of atrial fibrillation, pacemaker implantation, and all-cause mortality compared to those with a normal PR interval 2.
- Another study published in the journal Heart found that prolonged PR interval was associated with an increased risk of mortality, heart failure, and atrial fibrillation 4.
Diagnosis and Management
- First-degree heart block is typically diagnosed using electrocardiography (ECG) 5, 3.
- Management of first-degree heart block usually involves monitoring and may include pacemaker implantation in certain cases 6, 2.
- It is essential to exclude underlying organic heart disease and to consider the individual's overall clinical context when evaluating a prolonged PR interval 3.