HEART BLOCKS

The heart’s rhythm is coordinated by its own electrical system. With each heartbeat, the electrical impulse begins at the sinus (or sinoatrial, SA) node, also called the heart’s natural pacemaker. The SA node is a cluster of specialized cells, located in the right atrium. The SA node produces the electrical impulses that set the rate and rhythm of your heartbeat. The impulse spreads through the walls of the right and left atria, causing them to contract, forcing blood into the ventricles. The impulse then reaches the atrioventricular (AV) node, which acts as an electrical bridge allowing impulses to travel from the atria to the ventricles. There is a short delay before the impulse travels on to the ventricles. From the AV node, the impulse travels through a pathway of fibers called the HIS-Purkinje system. This network sends the impulse into the muscular walls of the ventricles and causes them to contract. This contraction forces blood out of the heart to the lungs and body.

You can tell how fast your heart is beating by feeling your pulse. You can feel your pulse on your wrist or neck. Place the tips of your index and middle fingers on the inner wrist of your other arm, just below the base of your thumb. Or, place the tips of your index and middle fingers on your lower neck, on either side of your windpipe. Press lightly with your fingers until you feel the blood pulsing beneath your fingers. You may need to move your fingers around slightly up or down until you feel the pulsing. Your heart rate, or pulse, is the number of beats felt in one minute. You can count the number of beats in 10 seconds and multiply by 6 to determine your heart rate in beats per minute. A normal heart rate, at rest, is 50 to 100 beats per minute. The normal heart rhythm (also called normal sinus rhythm) shows the electrical activity in the heart is following the normal pathway, the rhythm is regular and the node is normal (about 50 to 100 beats per minute).

Premature ventricular contractions (PVCs) - are early, extra beats beginning in the lower chambers of the heart (ventricles). PVCs are common. Most of the time they cause no symptoms and require no treatment. In some people, they can be related to stress, too much caffeine or nicotine, or exercise. But sometimes, PVCs can be caused by heart disease or an electrolyte imbalance. If you have a lot of PVCs and/or arrhythmia symptoms associated with them (see the symptoms listed on page 8), you should be evaluated by a cardiologist. Ventricular tachycardia (V-tach) - a rapid rhythm originating from the lower chambers of the heart. This rapid rate prevents the heart from filling adequately with blood, and less blood is pumped through the body. This can be a more serious arrhythmia, especially in people with heart disease, and may be associated with more symptoms. A cardiologist should evaluate this arrhythmia condition.

Long QT - the QT interval is the area on the electrocardiogram (ECG or EKG) that represents the time it takes for the heart muscle to contract and then recover, or for the electrical impulse to fire and then recharge. When the QT interval is longer than normal, it increases the risk for “torsades de pointes,” a life-threatening form of ventricular tachycardia. Arrhythmias may have many causes, including coronary artery disease, changes in the heart muscle (heart failure or cardiomyopathy), valve disease, electrolyte imbalances in your blood (such as sodium or potassium), injury from a heart attack or the healing process after heart surgery. A fast or slow heart rate does not always mean your heart rhythm is abnormal. Fast or slow heart rates are also related to anxiety, activity, medications or other normal causes.