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Ventricular contraction occurs between ventricular depolarization and repolarization. During this time, there is no movement of charge, so no deflection is created on the ECG. This results in the flat ST segment after the S wave. [71] Frames 24–28 in the animation depict repolarization of the ventricles.
The action potential passes along the cell membrane causing the cell to contract, therefore the activity of the sinoatrial node results in a resting heart rate of roughly 60–100 beats per minute. All cardiac muscle cells are electrically linked to one another, by intercalated discs which allow the action potential to pass from one cell to the ...
The QRS complex is the combination of three of the graphical deflections seen on a typical electrocardiogram (ECG or EKG). It is usually the central and most visually obvious part of the tracing. It corresponds to the depolarization of the right and left ventricles of the heart and contraction of the large ventricular muscles.
A broad SA results when the heart undergoes pathological changes and is reflected in a discordant ECG. A large SA indicates an altered ventricular repolarization sequence, and may be the result of structural and functional myocardial changes that induce regional shortening in action potential duration and impaired ion channel functioning. [12]
Schematic representation of a normal sinus rhythm EKG wave. In electrocardiography, the PR interval is the period, measured in milliseconds, that extends from the beginning of the P wave (the onset of atrial depolarization) until the beginning of the QRS complex (the onset of ventricular depolarization); it is normally between 120 and 200 ms in duration.
These signals are generated rhythmically, which results in the coordinated rhythmic contraction and relaxation of the heart. On the microscopic level, the wave of depolarization propagates to adjacent cells via gap junctions located on the intercalated disc. The heart is a functional syncytium as opposed to a skeletal muscle syncytium. In a ...
ECG would be abnormal in 75 to 95% of the patients. Characteristic ECG changes would be large QRS complex associated with giant T wave inversion [4] in lateral leads I, aVL, V5, and V6, together with ST segment depression in left ventricular thickening. For right ventricular thickening, T waves are inverted from V2 to V3 leads.
The plateau lasts on the order of 100 ms. At the time that calcium channels are getting activated, channels that mediate the transient outward potassium current open as well. This outward potassium current causes a small dip in membrane potential shortly after depolarization. This current is observed in human and dog action potentials, but not ...