Using Waves and Intervals to Evaluate Cardiac Nerve Conduction and Contraction
The heart is a vital organ that is responsible for pumping blood through the vessels that deliver oxygen and nutrients to cells throughout the body. Damage to the heart can cause severe cardiac complications that compromise the body’s ability to sustain life for more than a few minutes. An increase in the prevalence of heart disease in the United States over the past several years has led to growing concern over the impact of chronic illnesses such as obesity and diabetes on the healthcare system. The number of people who currently require long-term cardiac care is higher than at any other point in history. One procedure that has seen a dramatic spike in use is the electrocardiogram (EKG). An EKG is a non-invasive medical procedure that uses electrodes to create views of the electrical and contractile activity of the heart. An electrocardiogram machine collects data about electrical conduction and translates the information into a series of waves and intervals that medical personnel use to evaluate heart health.
The electrocardiogram is often administered by an EKG technician who has the basic knowledge and skills to perform the exam and conduct an initial evaluation of the results. In order to provide comprehensive care to patients, it is important for the technician to have a basic appreciation for the structure of the heart, electrical conduction within the heart, and the waves and intervals seen on the EKG results. The standard human heart contains four chambers that work together to move blood through the circulatory system. The two chambers located on the right side of the heart are tasked with pumping blood to the lungs while the two chambers on the left side of the heart are tasked with pumping blood through the vessels that lead to the rest of the body. Each side of the heart consists of a small chamber known as an atrium and a large chamber known as a ventricle.
To ensure that blood flows in the proper direction through the body, the smaller atrium must contract before the larger ventricle. Because the atrium is located above the ventricle, it is responsible for filling the ventricle with blood before it contracts. The ventricle is larger than the atrium because it must pump blood against much greater resistance. The coordinated contraction of the atrium before the ventricle is accomplished through the creation of an electrical impulse at the top of the right atrium. This impulse travels along nerve pathways that course through the atria toward the ventricles. Because the impulse must travel through the atria in order to reach the ventricles, contraction occurs in the atria prior to contraction of the ventricles. An EKG captures this electrical activity as it occurs and creates a tracing that is used to evaluate the health of the cardiac cells and nerve conduction pathways.
The standard electrocardiogram consists of three waves (P wave, QRS complex, T wave) that represent different events that occur during each beat of the heart. The P wave demonstrates atrial contraction, the QRS complex shows ventricular contraction, and the T wave represents the return of the ventricles to a resting state between contractions. Waves that appear abnormal, last longer than they should, or are spaced unnaturally are usually indicative of heart disease. Because there are many different types of diseases that can affect the heart, it is important for the EKG technician to have detailed knowledge of the changes that occur in the EKG tracing with each disease.
The distance between waves is referred to as an interval. Intervals are often used to evaluate the elapsed time during and between contractions. The PP and RR intervals show how much time has passed between each atrial and ventricular contraction while the QT and QRS intervals demonstrate ventricular depolarization and repolarization. An understanding of EKG rhythms and intervals is essential to your success as an electrocardiogram technician and will be covered in-depth during the training process.