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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]
A 12 lead ECG showing sinus tachycardia. Sinus tachycardia is usually apparent on an ECG, but if the heart rate is above 140 bpm the P wave may be difficult to distinguish from the previous T wave and one may confuse it with a paroxysmal supraventricular tachycardia or atrial flutter with a 2:1 block.
If at least three different shaped P waves can be seen in a given ECG lead tracing, this implies that even if one of them arises from the SA node, at least two others are arising elsewhere. This is taken as evidence of multiple (i.e. at least two) ectopic foci , and is called multifocal (or more correctly, multiform) atrial rhythm if the rate ...
The rhythmic sequence (or sinus rhythm) of this signaling across the heart is coordinated by two groups of specialized cells, the sinoatrial (SA) node, which is situated in the upper wall of the right atrium, and the atrioventricular (AV) node located in the lower wall of the right heart between the atrium and ventricle.
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:
The diagnosis of WPW occurs with a combination of palpitations and when an electrocardiogram (ECG) show a short PR interval and a delta wave. [3] It is a type of pre-excitation syndrome. [3] WPW syndrome may be monitored or treated with either medications or an ablation (destroying the tissues) such as with radiofrequency catheter ablation. [4]
Sinus arrhythmia characteristically presents with an irregular rate in which the variation in the R-R interval is more than 0.12 seconds (120 milliseconds). Additionally, P waves are typically mono-form and in a pattern consistent with atrial activation originating from the sinus node .
Sinus tachycardia is physiologic when a reasonable stimulus, such as the catecholamine surge associated with fright, stress, or physical activity, provokes the tachycardia. It is identical to a normal sinus rhythm, except for its faster rate (>100 beats per minute in adults). However, sinus tachycardia is considered part of the diagnoses ...