What happens during ventricular depolarization?
The depolarization spreads from the atrioventricular node to the septum and the walls of both ventricles through the bundle of His and Purkyne fibres. The ventricular depolarization causes the QRS complex in the ECG (fig. 1.3). At the same moment, the atria are repolarized to produce the atrial T (Ta) wave in the ECG.
What does ventricular repolarization mean?
Repolarization in the ventricles of the heart is a process allowing the muscle cells of the ventricles to regain their ability to depolarize again. Repolarization entails movement of the ions, which entered the cell during the depolarization phase of the cycle, to flow out of the cell.
What are ventricular premature depolarizations?
Ventricular premature depolarization (VPD)-induced cardiomyopathy is a condition in which frequent ventricular ectopic impulses result in left ventricular (LV) dysfunction leading to systolic heart failure (HF) [1–3].
What causes ventricular repolarization?
The mechanisms behind the abnormal ventricular repolarization of RV patients are not known. Factors such as hyperactivity of the sympathetic nervous system, and abnormality of intracellular ion currents and couplings may have a role in QT prolongation.
When does ventricular depolarization occur?
The isoelectric period (ST segment) following the QRS and ending at the beginning of the T wave is the time at which both ventricles are completely depolarized. This segment roughly corresponds to the plateau phase of the ventricular action potentials.
Is ventricular depolarization the same as contraction?
Ventricular depolarization will lead to ventricular contraction and the start of systole. Remember that systole is the cardiac phase in which the heart, especially the ventricles, contracts to move blood forward into the pulmonary artery and aorta.
Where does ventricular repolarization occur?
Ventricular repolarization is a complex electrical phenomenon which represents a crucial stage in electrical cardiac activity. It is expressed on the surface electrocardiogram by the interval between the start of the QRS complex and the end of the T wave or U wave (QT).
Which ECG wave represents ventricular repolarization?
T waves represent ventricular repolarization (atrial repolarization is obscured by the large QRS complex).
What is the most common cause of premature ventricular contractions?
Heart disease or scarring that interferes with the heart’s normal electrical impulses can cause PVCs. Certain medications, alcohol, stress, exercise, caffeine or low blood oxygen, which is caused by chronic obstructive pulmonary disease (COPD) or pneumonia, can also trigger them.
During which part of the ECG does ventricular repolarization occur?
Ventricular depolarization (activation) is depicted by the QRS complex, whereas ventricular repolarization is defined by the interval from the beginning of the QRS complex to the end of the T- or U-wave. On the surface ECG, ventricular repolarization components include the J-wave, ST-segment, and T- and U-waves.
Does repolarization mean relaxation?
When the electrical signal of a depolarization reaches the contractile cells, they contract. When the repolarization signal reaches the myocardial cells, they relax.
What wave is ventricular depolarization?
Atrial depolarization is reflected by the P wave, and ventricular depolarization is reflected by the QRS complex, whereas the T wave reflects ventricular repolarization, see Figure 6.10.
What is depolarization vs repolarization?
The main difference between the two is: depolarization is described as the loss of resting membrane potential as a result of the alteration of the polarization of cell membrane. repolarization is described as the restoration of the resting membrane potential after every depolarization event.
What is depolarization and repolarization in ECG?
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. A wave of repolarization traveling away from a positive electrode results in a positive deflection.
What does the P QRS and T wave represent?
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.
Is premature ventricular contractions life threatening?
Some are life-threatening, but others can be quite benign. Ventricular premature complexes are one example of a benign condition that can cause an irregular heartbeat. In fact, most people experience this condition at some point in their lives. This condition can occur at random times or in regular patterns.
Can you live a normal life with PVCs?
In general even those with fairly frequent PVC’s who have had underlying heart disease ruled out can be reassured and likely have a good prognosis.