First-degree heart block is a conduction delay of the electrical impulse through the atria to the ventricles. Normally an electrical impulse travels from atria to ventricle in 0.2 seconds. A first-degree block occurs when the interval is prolonged, but each impulse reaches the ventricles, so there are no skipped beats. First-degree heart block usually causes no symptoms and requires no specific treatment, according to The Merck Manuals Online Medical Library. Discovery of the condition usually occurs during routine electrocardiogram testing.
Diagnosis
Although first-degree heart block rarely requires treatment, diagnosis of the possible underlying cause ensures that no significant heart disease has been missed. First-degree heart block most commonly occurs in athletes, teens and young adults. Certain diseases, such as Lyme disease, systemic lupus erythematosus and rheumatic fever can also cause first-degree heart block. Certain medications such as beta-blockers, which includes amiodarone, digoxin, verapamil or diltiazem can also result in first-degree heart block. Rarely an electrolyte imbalance causes the condition, the Heart Rhythm Society reports.
Treating the Cause
Most causes of first-degree heart block require no treatment. Medications causing the block can be adjusted if the prescribing physician feels it's necessary to do so. Disease like Lyme disease and autoimmune diseases require treatment in and of themselves, which may cure the problem. Patients with severe heart failure and first-degree heart block may have improved cardiac function after pacemaker implantation, the Heart Rhythm Society states. Correcting an existing electrolyte imbalance may also help cure a first-degree heart block.
Observation
While first-degree heart block itself causes no symptoms and generally needs no treatment, it may be a forerunner of atrial fibrillation, a quivering rather than forceful beating of the atria. In the September 2009 issue of the "Journal of the American Medical Association", Dr. Susan Cheng of Massachusetts General Hospital reports results from the Framingham Heart Study of over 75,000 individuals with first- degree heart block. Atrial fibrillation occurred twice as often in the group with first-degree heart block as those without, and the need for pacemaker implantation was three times higher. This indicates a need for close cardiac follow-up for people with first-degree heart block.
References
- "Journal of the American Medical Association" : Long-term Outcomes in Individuals With Prolonged PR Interval or First-Degree Atrioventricular Block; Dr. Susan Cheng; June 2009
- Heart Rhythm Society: Heart block Treatment Options
- The Merck Manuals Online Medical Library: Heart Block
- American Heart Association: Heart Block
