What do deflection waves represent

Ventricular systole begins shortly after the QRS complex appears. The QRS has a complex shape that may consist of up to 3 waves. This is due to the passage of depolarization wave down the interventricular septum, and through the septum from left to right, upward from the apex, and through the lateral walls of the ventricles.

In a typical ECG, the Q wave is the initial downward deflection. The R wave is an upward deflection, while the S wave is the second downward deflection.

The normal duration of a QRS complex is between 70 milliseconds 0. During the formation of the QRS complex, atrial repolarization electrical recovery takes place, which is not usually evident on an ECG due to the large QRS complex that masks it. The T wave reflects ventricular repolarization. Because ventricle repolarization is slower than depolarization, the T wave is more spread out than the QRS complex.

A normal T wave is usually smooth and rounded, and has the same deflection orientation same direction , as the QRS complex. A typical T wave lasts approximately milliseconds 0.

A U Wave indicates that the repolarization of the ventricles has occurred. An abnormally tall U wave may be present in hypokalemia, cardiomyopathy, left ventricle hypertrophy, diabetes, and may follow administration of digitalis and quinidine. The lead EKG will be discussed in greater detail later in this course.

However, at this time we will present an introduction to the EKG leads simply to help explain the basics of EKG interpretation that will follow. Later, the specifics of leads and lead placement will be discussed. An EKG lead consists of two surface electrodes of opposite polarity positive and negative or one positive surface electrode and one reference point.

A lead composed of two electrodes of opposite polarity is called a Bipolar Lead. A lead composed of a single positive electrode and a reference point is called a Unipolar Lead. All leads of the ECG record the same electrical impulses of the heart muscle. Diagnosis of arrhythmias may be made easier by examination of different leads. The lead ECG tracing is standard. Six leads are recorded by placing wires on each limb.

The other six leads are recorded by placing wires on the chest in six specific positions. Chest Leads: , , , , ,. For diagnosis of most arrhythmias, lead II is most commonly used. Lead II and the chest leads most consistently show the most clear P Wave which can be diagnostic of many common arrhythmias.

If changes in the ECG tracing are seen in a group of the above leads, the disease can be localized to a particular area of the heart. If the MD can thus localize the damage to the heart they can also diagnose other possible problems in the heart.

Under normal circumstances, the duration of the QRS complex in an adult patient will be between 0. It can also be thought of as the start of the ST segment. The J-point also known as Junction is important because it can be used to diagnose an ST segment elevation myocardial infarction. A T wave follows the QRS complex and indicates ventricular repolarization. Unlike a P wave, a normal T wave is slightly asymmetric; the peak of the wave is a little closer to its end than to its beginning.

When a T wave occurs in the opposite direction of the QRS complex, it generally reflects some sort of cardiac pathology. If a small wave occurs between the T wave and the P wave, it could be a U wave.

The biological basis for a U wave is unknown. One of the quickest ways is called the sequence method. To use the sequence method, find an R wave that lines up with one of the dark vertical lines on the ECG paper. If the next R wave appears on the next dark vertical line, it corresponds to heart rate of beats a minute. The dark vertical lines correspond to , , , 75, 60, and 50 bpm. There are more accurate ways to determine heart rate from ECG, but in life-saving scenarios, this method provides a quick estimate.