Bradycardia refers to a condition where the heart beats at an unusually slow rate. For most adults at rest, a normal heart rate falls within a range of 60 to 100 beats per minute (bpm). When an adult’s resting heart rate consistently drops below 60 bpm, it is considered bradycardia. This slow heart rate can hinder the heart’s ability to circulate blood throughout the body.
Spotting the Signs
A slow heartbeat can lead to symptoms because the body’s organs, especially the brain, may not receive enough oxygen. Individuals might experience fatigue or weakness.
Dizziness or lightheadedness are indicators, resulting from reduced blood flow to the brain. In more severe instances, a person might experience fainting spells or feel as though they are about to faint. Shortness of breath can also occur, particularly during physical exertion.
Individuals may report chest pain, or notice confusion and memory problems. These cognitive difficulties stem from the brain’s insufficient oxygen supply due to the heart’s slowed pumping action. Tiring easily during exercise is a complaint.
Why a Slow Heartbeat Occurs
Many factors and medical conditions can contribute to a slow heart rate. The natural aging process is a common contributor, as the heart’s electrical conduction system can degenerate over time. This age-related wear can disrupt the electrical signals that regulate heartbeats.
Several heart conditions are also implicated. These include sick sinus syndrome, where the heart’s natural pacemaker malfunctions, leading to irregular or abnormally slow beats. Heart block involves disruptions in the electrical pathways that prevent signals from traveling between the heart’s upper and lower chambers. Damage from a heart attack, heart disease, or congenital heart defects can also impair the heart’s electrical system.
Beyond cardiac issues, other medical conditions can cause bradycardia. An underactive thyroid gland can slow the heart rate. Imbalances in electrolytes can also affect the heart’s electrical impulses. Sleep apnea and inflammatory conditions like myocarditis or rheumatic fever are also causes.
Certain medications can induce bradycardia as a side effect. These include beta-blockers, calcium channel blockers, digoxin, and some anti-arrhythmic drugs. Adjusting or discontinuing the medication can resolve the slow heart rate. High levels of physical fitness can also result in a naturally slow resting heart rate. Hypothermia and certain neurological conditions can also lead to a slowed heart rate.
Identifying and Managing Bradycardia
Identifying a slow heartbeat begins with a thorough physical examination and a review of the patient’s medical history. A medical professional will listen to the heart with a stethoscope and measure the heart rate and blood pressure. The primary diagnostic tool is an electrocardiogram (ECG), which records the electrical activity of the heart and can pinpoint rhythm abnormalities.
If a standard ECG, which captures a brief snapshot of heart activity, does not reveal the slow heart rate, other diagnostic tests may be used. A Holter monitor, a portable ECG device worn for 24 to 72 hours, continuously records heart activity to detect intermittent episodes of bradycardia. An event recorder is similar but only records when symptoms occur or when manually activated, and can be worn for up to 30 days. Additional tests like an echocardiogram, an ultrasound of the heart that provides images of its structure and function, or a stress exercise test, which monitors heart activity during physical exertion, may also be performed. A tilt table test might be conducted if fainting spells are a symptom, assessing how heart rate and blood pressure respond to changes in body position.
Managing bradycardia often involves addressing the underlying cause first. If medications are responsible for the slow heart rate, adjustments to the dosage or a change in prescription may be made. Treating conditions like hypothyroidism with hormone replacement therapy or managing sleep apnea can also resolve the bradycardia. In acute situations, certain intravenous medications, such as atropine, can temporarily increase the heart rate.
For symptomatic bradycardia not caused by reversible factors, or when the heart’s electrical conduction system is permanently impaired, a pacemaker implantation is frequently the definitive long-term solution. A pacemaker is a small, battery-powered device surgically placed under the skin, usually near the collarbone. It mimics the heart’s natural pacemaker, the sinus node, by continuously monitoring the heart’s rhythm. If it detects a rate that is too slow, it sends tiny, undetectable electrical signals to stimulate the heart and maintain a healthy pace. Leads, which are thin, insulated wires, connect the pacemaker to the heart, delivering electrical impulses and relaying information back to the device. Newer leadless pacemakers, about the size of a large vitamin capsule, can be implanted directly into the heart through a vein in the leg for specific pacing needs. Regular medical check-ups and adherence to a doctor’s advice are important for ongoing management.