A typical ECG tracing of the cardiac cycle (heartbeat) consists of
a P wave (atrial depolarization ), a QRS complex (ventricular depolarization), and a T wave (ventricular repolarization)
. An additional wave, the U wave ( Purkinje repolarization), is often visible, but not always.
What do the P QRS and T waves represent?
The P wave in an ECG complex indicates
atrial depolarization. The QRS is responsible for ventricular depolarization and the T wave is ventricular repolarization
.
What represents a cardiac cycle?
The cardiac cycle is
the performance of the human heart from the beginning of one heartbeat to the beginning of the next
. It consists of two periods: one during which the heart muscle relaxes and refills with blood, called diastole, following a period of robust contraction and pumping of blood, called systole.
What does the T wave represent in an ECG?
Introduction. 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 are the 4 stages of cardiac cycle?
- Conducting system of the heart.
- Cardiac cycle phases. Atrial diastole. Atrial systole. Ventricular diastole. Ventricular systole.
- Wiggers Diagram. Aortic pressure. Atrial pressure. Ventricular pressure and volume. …
- Frank-Starling mechanism.
- Disorders affecting the cardiac cycle. Electrolyte imbalance. Heart failure.
- Sources.
What are the 3 stages of cardiac cycle?
- Atrial and Ventricular diastole (chambers are relaxed and filling with blood)
- Atrial systole (atria contract and remaining blood is pushed into ventricles)
- Ventricular systole (ventricles contract and push blood out through aorta and pulmonary artery)
What is not represented on an ECG tracing?
Key Terms.
fibrillation
: A condition in which parts of the ECG do not appear normally, representing irregular, rapid, disorganized, and inefficient contractions of the atria or ventricles.
Why is Q wave negative in ECG?
As septal depolarization moves from left to right, the depolarization vector is directed towards the – electrode of lead II (RA)
, and therefore a negative-going deflection (Q-wave) is produced.
How do you draw a cardiac cycle?
What are the 5 stages of the cardiac cycle?
- Atrial Systole.
- Early Ventricular Systole.
- Ventricular Systole.
- Early Ventricular Diastole.
- Late Ventricular Diastole.
What does ventricular diastole mean?
Ventricular diastole is
the period during which the two ventricles are relaxing from the contortions/wringing of contraction, then dilating and filling
; atrial diastole is the period during which the two atria likewise are relaxing under suction, dilating, and filling.
Which time period does the T wave in an electrocardiogram ECG represent quizlet?
The T wave in the electrocardiogram should be upright, and it represents the time for
ventricular repolarization
. If present, the U wave indicates the repolarization of the Purkinje fibers. Which anatomic feature of the heart directly stimulates ventricular contractions? You just studied 35 terms!
What are the components of a cardiac wave pattern?
There are three main components to an ECG:
the P wave, which represents depolarization of the atria; the QRS complex, which represents depolarization of the ventricles; and the T wave, which represents repolarization of the ventricles
.
What are the 6 phases of the cardiac cycle?
- Phase 1 – Atrial Contraction.
- Phase 2 – Isovolumetric Contraction.
- Phase 3 – Rapid Ejection.
- Phase 4 – Reduced Ejection.
- Phase 5 – Isovolumetric Relaxation.
- Phase 6 – Rapid Filling.
- Phase 7 – Reduced Filling.
What are the 7 phases of the cardiac cycle?
- Atrial diastole.
- Atrial systole.
- Isovolumic contraction.
- Ventricular ejection.
- Isovolumic relaxation.
- Ventricular filling.
How many stages are there in the cardiac cycle?
The cardiac cycle can be divided into
four stages
: Filling phase – the ventricles fill during diastole and atrial systole. Isovolumetric contraction – the ventricles contract, building up pressure ready to pump blood into the aorta/pulmonary trunk.
How do you read ECG traces?
When interpreting the heart rhythm, you should
look for P waves, which is a sign of atrial excitation
. When every P wave is followed by a QRS complex, the ECG shows sinus rhythm. If the P waves are irregular, sinus arrhythmia is likely present.
What part of the ECG tracing is the flat line between the various waves?
The
ST segment
usually appears as a straight, level line between the QRS complex and the T wave.
What does R wave represent?
These waves indicate
the changing direction of the electrical stimulus as it passes through the heart’s conduction system
. The largest wave in the QRS complex is the R wave. As you can see from the diagram, the R wave represents the electrical stimulus as it passes through the main portion of the ventricular walls.
What is polarization in ECG?
Heart muscle cells are polarized when at rest. This means that
the net charge density of the fluid inside and outside of the cells is different, because ion concentrations are different on either side of the cell membranes
.
Why P wave is positive in ECG?
The P wave and PR segment is an integral part of an electrocardiogram (ECG).
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.
