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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 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 ...
Sinus arrhythmia is a commonly encountered variation of normal sinus rhythm. 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 ...
ECGs recorded during sinus rhythm and AVRT in a 9-year-old girl with Ebstein's anomaly and a Mahaim accessory pathway. About 50% of individuals with Ebstein's anomaly have an associated shunt between the right and left atria, either an atrial septal defect or a patent foramen ovale .
The AV node is the structure that controls how electrical signals travel between the upper chambers (atria) and lower chambers (ventricles). During normal sinus rhythm, these signals pass through only one pathway, known as the fast pathway. The fast pathway conducts signals quickly but has a longer rest period before it can send another signal.
Individuals with JET have a "short-circuit" in their heart, where the electricity bypasses the AV node, causing the heart to beat faster than normal. The cause of the arrhythmia, the ectopic focus, is usually near the AV node in the triangle of Koch (a rough triangle with points at the coronary sinus, the tendon of Todaro, and the tricuspid valve).
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).
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: