Heart Essay Research Paper The Normal Cardiac

Heart Essay, Research Paper

The Normal Cardiac Cycle

During each heartbeat, the two upper chambers (right and left atria) contract, followed by contraction of the two lower pumping chambers (right and left ventricles). This action is coordinated by the heart’s electrical system.

Normal electrical activation of the heart occurs in an orderly fashion. With each beat, the electrical impulse starts in the sinus (or sinoatrial) node (in the right atrium). The impulse spreads through the atria, stimulating the atria to contract. The impulse then reaches the atrioventricular node (AV node), an electrical bridge that allows impulses to go from the atria to the ventricles. There is a short delay in conduction before the impulse goes 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. The contraction pumps blood out of the heart to the lungs and throughout the body.

The rate at which the normal heart beats depends on the body’s need for oxygen-rich blood. When at rest, the body needs less oxygen-rich blood,

so the heart rate may be slower. However, during activity or exercise, the body needs more oxygen-rich blood, and the sinus node causes the heart rate to increase. Taking a pulse tells how fast the heart is beating.

Taking Your Pulse

You can feel your pulse on your wrist. Place your index and middle finger on the inner wrist of your other arm, just below the base of your thumb. 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. By feeling your pulse, you can also tell if your heart rhythm is regular or not.

YOUR HEART RATE = PULSE IN 10 SECONDS x 6 = ____ beats per minute

What is an arrhythmia.

An arrhythmia is an irregular or abnormal heart rhythm. Arrhythmias may have many causes, including coronary artery disease, changes in the heart muscle, valvular disorders, electrolyte imbalances, or injury from a heart attack. Irregular heart rhythms can even occur in a healthy “normal” heart.

Common Types of Arrhythmias

Tachycardia – a fast heart rhythm that has a rate of more than 100 beats per minute.

Bradycardia – a slow heart rhythm that has a rate below 60 beats per minute.

Supraventricular arrhythmias – arrhythmias originating above the ventricles, for example in the upper chambers, or atria. (”Supra” means above; “ventricular” refers to the lower chambers of the heart.)

Premature atrial contractions (PACs) – early, extra beats originating in the upper chambers of the heart.

Paroxysmal supraventricular tachycardia (PSVT) – a rapid, usually regular rhythm originating from above the ventricles that begins and ends

suddenly.

Accessory pathway mediated tachycardias (e.g. Wolff-Parkinson-White syndrome) – tachycardias due to an extra, abnormal electrical pathway or connection between the atria and ventricles.

AV nodal reentrant tachycardia – tachycardia due to more than one pathway through the AV node.

Atrial tachycardia – a rapid rhythm originating in the atria.

Atrial fibrillation – an arrhythmia due to rapid impulses coming from the atria that are disorganized and irregular. Mechanically, this pattern of rapid, disordered atrial activation results in loss of coordinated atrial contraction. Irregular electrical inputs to the atrioventricular (AV) node and His-Purkinje system leads to irregular ventricular contractions.

Atrial flutter – an atrial arrhythmia due to one or more rapid circuits in the atrium. This arrhythmia generally is more ordered than atrial fibrillation.

Ventricular arrhythmias – arrhythmias arising from the lower chambers of the heart.

Premature ventricular contractions (PVCs) – early, extra beats originating in the lower chambers of the heart. PVCs are common. Usually they cause no symptoms and require no treatment. In some people, PVCs can be related to stress, caffeine, nicotine or to exercise. But sometimes, PVCs can be caused by heart disease or electrolyte imbalance. People who have a lot of PVCs and/or symptoms associated with them should be evaluated by a cardiologist.

Ventricular tachycardia – a rapid rhythm originating from the lower chambers. This can be a more serious arrhythmia, particularly in people with heart disease, and may be associated with more symptoms. It should be evaluated by a cardiologist.

Ventricular fibrillation – an erratic, disorganized firing of impulses from the ventricles. The ventricles quiver and cannot generate an effective contraction, causing an inability to deliver blood to the body. It is a medical emergency that must be treated with cardiopulmonary resuscitation (CPR) and defibrillation as soon as possible.

Bradyarrhythmias – slow heart rhythms which may arise from disease in the sinus node and other parts of the heart’s conduction system, including the AV node and His-Purkinje system.

Sinus node dysfunction – slow heart rhythms due to abnormalities in the sinus (sinoatrial) node.

Heart block – a delay or complete blocking of the electrical impulse as it travels

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