Bradyarrhythmias
Einstein Health Glossary
ICD 10 - R001
What are bradyarrhythmias?
These are arrhythmias characterized by a low heart rate (slow heartbeats, below 50 bpm), prolonged pauses between heartbeats, or a lack of expected heart rate acceleration during physical exertion. Often, conduction blocks can be identified, where the electrical impulse that should travel from the atria (upper chambers of the heart) to the ventricles (lower chambers) fails to do so.
It’s important to note that not all bradycardias indicate disease. They may be physiological (e.g., in athletes or during sleep), where the heart rhythm is normal and the heart rate is low but does not cause symptoms or clinical consequences.
Causes
Bradyarrhythmias may result from aging of the heart’s electrical conduction system (the heart’s wiring), use of medications with negative chronotropic effects (which lower heart rate), drug toxicity, thyroid dysfunction, electrolyte imbalances such as potassium disturbances, calcification of heart valves, heart attacks, inflammatory/infiltrative heart diseases (myocarditis, Chagas disease, amyloidosis, etc.), post-cardiac surgery (such as valve implants, ablation, correction of congenital heart defects), degenerative neuromuscular diseases, and even congenital blocks (fetal heart malformations, maternal autoimmune disease).
Symptoms
When bradyarrhythmia leads to heart rates low enough to reduce blood flow, symptoms can vary from mild dizziness to fainting (loss of consciousness). Other symptoms may include weakness/excessive drowsiness, shortness of breath, and chest pain during exertion.
Diagnosis
In most cases, clinical history, physical examination, and electrocardiogram are sufficient. A 24-hour Holter monitor is very helpful in assessing heart rate behavior over a full day and identifying intermittent blocks and pauses. An echocardiogram helps in cases involving congenital malformations, valve disease, or progression to heart failure.
A stress test may be necessary to rule out associated ischemic disease and to evaluate chronotropic incompetence (lack of heart rate increase during physical effort). In certain cases with sporadic symptoms, a loop recorder (event monitor) may be used to capture the heart rhythm during symptoms. The event monitor can be external (worn for 7 to 30 days) or implantable (a small device placed under the chest skin that can monitor heart rhythm for up to 3 years).
When the cause of symptoms—especially syncope (fainting)—is not identified through standard tests, an electrophysiological study (a specialized catheterization to investigate arrhythmias) may be used to evaluate the heart’s electrical system.
Treatment
Treatment depends on the severity of the bradyarrhythmia, the presence of associated symptoms, and whether reversible causes are identified. In asymptomatic and non-severe cases, clinical monitoring may be sufficient. In cases with associated risks and no reversible causes, a pacemaker implant may be necessary. This device maintains heartbeats through artificial electrical stimulation.
Prevention
Regular medical check-ups and control of risk factors such as diabetes, obesity, hypertension, and smoking are essential. Extra care should be taken with patients who already have heart conditions (valve disease, heart attacks, heart failure, etc.).