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Junctional bradycardia is a slow heart rate caused by a malfunction of electrical impulses in the upper right chamber of the heart. The sinoartial (SA) node in this chamber serves as the main pacemaker to keep an adult resting heart rate between 60 and 100 beats per minute. When electrical impulses misfire from junctional bradycardia, the atrioventicular (AV) node in the lower chamber takes over as a substitute pacemaker, keeping the heart rate between 40 and 60 beats per minute. Also called third-degree blockage, junctional bradycardia prevents electrical impulses from passing to ventricles, which control normal contractions that pump blood to the lungs and other organs.
Some patients show no symptoms of junctional bradycardia until the heart rate dips below 50 beats per minutes, limiting the amount of oxygen-rich blood sent to the brain and other organs. Athletes and people who exercise regularly might register below 60 beats per minute as normal with no signs of bradycardia. Cardiologists typically perform several tests to determine if junctional bradycardia poses a risk of a heart failure.
Symptoms of the condition include chest pain and fatigue. When insufficient oxygen reaches the brain, some patients become dizzy, may faint, and suffer from confusion and memory loss. Shortness of breath during exercise represents another symptom of junctional bradycardia, which might occur with or without chest pain.
Sinoarterial or atrioventricular nodes might degrade as a person ages, leading to junctional bradycardia. High blood pressure and high cholesterol might also contribute to disruptions in the heart’s electrical system. Too much iron in the blood, or an electrolyte or mineral imbalance, might also cause the disorder, along with thyroid disorders. Some patients who suffer from sleep apnea, a condition where breathing stops several times each night, might also develop a slow heart rate.
Excessive alcohol use and smoking increase the risk of a disruption in electrical signals in the heart. Some medication and illegal drugs might also affect electrical impulses. Stress might also pose a risk of developing a blockage in the AV node that interrupts normal functioning.
Treatment of the condition commonly involves a pacemaker to maintain normal heart rate. Electrodes in a pacemaker connected to the heart create impulses to keep the heart rate steady when these signals become blocked. Some forms of bradycardia might be treated with medication that speeds up the heart. If an underlying condition is suspected, a doctor typically treats that problem.