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Causes. Typical heartbeat Enlarge image. In a typical heart rhythm, a tiny cluster of cells at the sinus node sends out an electrical signal. The signal then travels through the atria to the atrioventricular (AV) node and then passes into the ventricles, causing them to contract and pump out blood.
An electrocardiogram (ECG or EKG) is the main test used to diagnose bradycardia. An ECG measures the electrical activity of the heart. Sticky patches (electrodes) are placed on the chest and sometimes the arms and legs. Wires connect the electrodes to a computer, which displays the results.
Slow heartbeat, called bradycardia. A heart rate below 60 beats a minute is considered bradycardia. But a low resting heart rate doesn't always mean there's a problem. If you're physically fit, your heart may be able to pump enough blood to the body with less than 60 beats a minute.
Causes. Tachycardia is an increased heart rate for any reason. If a fast heart rate is caused by exercise or stress, it's called sinus tachycardia. Sinus tachycardia is a symptom, not a condition. Most heart conditions can lead to different forms of tachycardia. Irregular heart rhythms, called arrhythmias, are one cause.
Tachycardia-bradycardia syndrome. The heart rate alternates between unusually slow and fast rhythms, often with a long pause between heartbeats.
The most common cause of hypothyroidism is an autoimmune disease called Hashimoto's disease. Autoimmune diseases happen when the immune system makes antibodies that attack healthy tissues. Sometimes that process involves the thyroid gland and affects its ability to make hormones.
Problems with the heart's structure are the most common cause of atrial fibrillation (AFib). Heart diseases and health problems that can cause AFib include: A heart problem you're born with, called a congenital heart defect. A problem with the heart's natural pacemaker, called sick sinus syndrome.
The vasovagal syncope trigger causes your heart rate and blood pressure to drop suddenly. That leads to reduced blood flow to your brain, causing you to briefly lose consciousness.
Causes. When standing from a sitting or lying position, gravity causes blood to collect in the legs and belly. Blood pressure drops because there's less blood flowing back to the heart. Usually, special cells (baroreceptors) near the heart and neck arteries sense this lower blood pressure.
Causes. To understand the cause of premature ventricular contractions (PVCs), it might help to learn more about how the heart typically beats. The heart is made of four chambers — two upper chambers (atria) and two lower chambers (ventricles). The heart's rhythm is controlled by a natural pacemaker (the sinus node) in the right upper chamber ...