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Bradycardia & Heart Block

Bradycardia is a heart rate below 60 beats per minute; heart block is a delay in the heart's electrical signals. Both can cause fatigue, dizziness, and fainting when severe.

Cardiovascular
Bradycardia is a heart rate slower than 60 beats per minute. Heart block (atrioventricular block) is a related problem in which the electrical signals traveling from the heart's upper chambers to its lower chambers are delayed or partially blocked. A slow heart rate is normal in well-trained athletes and during sleep; it becomes a medical problem when the heart cannot deliver enough blood to the brain and body, causing symptoms. 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.
When to Seek Immediate Care: Call 911 for fainting, chest pain, severe shortness of breath, or a very slow pulse accompanied by confusion or weakness. These can signal high-grade heart block that needs urgent attention. If you or your home blood pressure monitor keep recording an unusually slow pulse, do not ignore it. The internal-medicine team at Zimmer Medical Group can determine whether a slow heart rate is harmless or needs treatment, and coordinates promptly with cardiology when a pacemaker evaluation is warranted.

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