Causes
Slow rhythms usually reflect wear, damage, or outside influences on the heart's electrical system:- Age-related changes: The most common cause — the heart's natural pacemaker and wiring gradually develop scar tissue over decades.
- Heart disease: Coronary artery disease and prior heart attacks can damage the conduction system.
- Medications: Beta-blockers, certain calcium channel blockers, and digoxin — often prescribed for high blood pressure or atrial fibrillation — can slow the heart too much.
- Underactive thyroid: Low thyroid hormone slows the entire metabolism, including heart rate; see hypothyroidism.
- Other causes: Electrolyte imbalances, untreated sleep apnea, and inflammation or infection involving the heart.
Degrees of Heart Block
Heart block is graded by severity. First-degree block is a simple delay in conduction and is usually harmless. Second-degree block means some beats fail to reach the lower chambers, which can cause a slow or irregular pulse. Third-degree (complete) block means no signals get through at all — the heart relies on a slow backup rhythm, and this form is dangerous and typically requires a pacemaker. Your physician distinguishes these patterns on the electrocardiogram, because they carry very different implications for treatment.Symptoms
Mild bradycardia often causes no symptoms. When the rate is too slow for the body's needs, people may notice:- Fatigue and exercise intolerance: Feeling drained or unable to keep up with usual activities.
- Dizziness or lightheadedness: Especially with standing or exertion.
- Fainting or near-fainting: Brief blackouts that can cause falls and injuries.
- Shortness of breath or confusion: More common in older adults with other heart conditions.
Diagnosis
An electrocardiogram documents the slow rate and identifies the degree of any heart block. Because symptoms often come and go, your physician may order a wearable monitor worn for one to fourteen days to catch intermittent pauses. Blood tests check thyroid function and electrolytes, and a careful medication review is essential, since dose adjustments alone often solve the problem. If you use a smartwatch or home blood pressure cuff, bringing its recorded readings to your visit can be genuinely helpful.Treatment
Treatment depends entirely on the cause and the severity of symptoms:- Treating reversible causes: Adjusting or stopping culprit medications, correcting thyroid or electrolyte problems, and treating sleep apnea may restore a normal rate.
- Observation: Asymptomatic mild bradycardia and first-degree block usually need no treatment beyond periodic monitoring.
- Pacemaker: A small implanted device that keeps the heart from beating too slowly — the standard treatment for symptomatic bradycardia, advanced second-degree block, and complete heart block. Modern pacemakers are implanted under the skin in a brief procedure and reliably last many years.