What are deflections in ECG?
A wave of depolarization traveling toward a positive electrode results in a positive deflection in the ECG trace. A wave of depolarization traveling away from a positive electrode results in a negative deflection. A wave of repolarization traveling toward a positive electrode results in a negative deflection.
What causes deflections on ECG?
The basic pattern of the ECG is logical: electrical activity towards a lead causes an upward deflection. electrical activity away from a lead causes a downward deflection. depolarization and repolarization deflections occur in opposite directions.
Which three of the following are the deflections of a typical ECG?
A typical ECG tracing has 4 recognizable waves, called deflection waves. These waves are labeled alphabetically as the P wave, the QRS complex, the T wave, and the U wave. The first wave is called the P wave.
What does the downslope of the P wave represent?
It represents the electrical depolarization of the atria of the heart. It is typically a small positive deflection from the isoelectric baseline that occurs just before the QRS complex.
What happens during each wave of an ECG?
The sinoatrial node (SA) is the pacemaker of the heart and produces the P wave. The QRS wave is produced by the atrioventricular node (AV). The P wave in an ECG complex indicates atrial depolarization. The QRS is responsible for ventricular depolarization and the T wave is ventricular repolarization.
Why is aVR inverted?
Lead –aVR: the inverted lead aVR As evident in Figure 2 there is 30° distance between each limb lead, except from the gap between lead I and lead II. To eliminate this gap, lead aVR can be inverted into lead –aVR.
What does ST depression indicate?
ST depression in ECG at entry indicates severe coronary lesions and large benefits of an early invasive treatment strategy in unstable coronary artery disease.
When is an 18 lead right sided ECG used?
18-lead synthesized ECG is expected to be useful in detecting right side and posterior infarction. Guidelines such as AHA, ACC or ESC recommend to measure additional lead (V3R-V5R and V7-V9) for the patient with suspected acute coronary syndrome.
What does an extra P wave mean?
The normal P wave is less than 0.12 seconds in duration, and the largest deflection, whether positive or negative, should not exceed 2.5 mm. An abnormal P wave may indicate atrial enlargement. Atrial depolarization follows the discharge of the sinus node.
Why is P wave positive in lead 2?
The normal P wave reflects these activation patterns. Thus, P waves are positive in lead II and usually in leads I, aVL, and aVF, reflecting the leftward and inferior direction of activation during sinus rhythm. This corresponds to a mean frontal plane P wave axis of approximately 60 degrees.
What is happening in the heart during ap wave on an ECG?
The P wave indicates atrial depolarization. The P wave occurs when the sinus node, also known as the sinoatrial node, creates an action potential that depolarizes the atria. The P wave should be upright in lead II if the action potential is originating from the SA node.
What is happening in the heart during the T wave on the ECG?
The T wave on the ECG (T-ECG) represents repolarization of the ventricular myocardium. Its morphology and duration are commonly used to diagnose pathology and assess risk of life-threatening ventricular arrhythmias.
What is a positive and negative deflection on an ECG?
Between cardiac cycles, the monitor or ECG recorder returns to the isoelectric line (baseline), the flat line in the ECG during which electrical activity is absent. Any waveform above the isoelectric line is considered a positive (upright) deflection and any waveform below this line a negative (downward) deflection.
What are the three main waveforms of the ECG?
The heart’s electrical activity is represented on the monitor or ECG tracing by three basic waveforms: the P wave, the QRS complex, and the T wave. A U wave is sometimes present. Between the waveforms are the following segments and intervals: the PR interval, the PR segment, the ST segment, and the QT interval.
What causes the shape of an ECG waveform to change?
The shape of the ECG waveform. Each individual leads ECG recording is slightly different in shape. This is due to each lead recording the electrical activity from different directions. When the electrical activity of the heart travels towards a lead you get a positive deflection.
What does the S wave mean on the ECG?
the S wave signifies the final depolarization of the ventricles, at the base of the heart ST segment The ST segment, which is also known as the ST interval, is the time between the end of the QRS complex and the start of the T wave. It reflects the period of zero potential between ventricular depolarization and repolarization. T wave