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A sinus rhythm is any cardiac rhythm in which depolarisation of the cardiac muscle begins at the sinus node. [1] It is necessary, but not sufficient, for normal electrical activity within the heart. [2] On the electrocardiogram (ECG), a sinus rhythm is characterised by the presence of P waves that are normal in morphology. [2]
When an individual is in normal sinus rhythm, the ECG characteristics of WPW are a short PR interval (less than 120 milliseconds in duration), widened QRS complex (greater than 120 milliseconds in duration) with slurred upstroke of the QRS complex, and secondary repolarization changes (reflected in ST segment-T wave changes). [citation needed]
Sinus tachycardia is a sinus rhythm of the heart, with an increased rate of electrical discharge from the sinoatrial node, resulting in a tachycardia, a heart rate that is higher than the upper limit of normal (90-100 beats per minute for adult humans).
Normal sinus rhythm produces the prototypical pattern of P wave, QRS complex, and T wave. Generally, deviation from normal sinus rhythm is considered a cardiac arrhythmia. Thus, the first question in interpreting an ECG is whether or not there is a sinus rhythm. A criterion for sinus rhythm is that P waves and QRS complexes appear 1-to-1, thus ...
Sinus bradycardia is commonly seen in normal healthy persons and athletes in the absence of pathophysiological diseases or conditions. [1] Different factors or etiologies could lead to the dysfunction of the sinus node, causing a malformation or prolongation of the impulse. In terms of pathophysiological diseases, sinus rhythm may be caused by:
Sinus node dysfunction (SND), also known as sick sinus syndrome (SSS), is a group of abnormal heart rhythms (arrhythmias) usually caused by a malfunction of the sinus node, the heart's primary pacemaker. [1] [2] Tachycardia-bradycardia syndrome is a variant of sick sinus syndrome in which the arrhythmia alternates between fast and slow heart ...
This is known as an escape rhythm. Since this accessory pacemaker also activates independently of the impulse generated at the SA node, two independent rhythms can be noted on the electrocardiogram (ECG). The P waves with a regular P-to-P interval (in other words, a sinus rhythm) represent the first rhythm.
This sinus rhythm is important because it ensures that the heart's atria reliably contract before the ventricles, ensuring as optimal stroke volume and cardiac output. [ 4 ] In junctional rhythm, however, the sinoatrial node does not control the heart's rhythm – this can happen in the case of a block in conduction somewhere along the pathway ...