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Sinus node dysfunction also known as sick sinus syndrome is a group of irregular heartbeat conditions caused by faulty electrical signals of the heart. When the heart's sinoatrial node is defective, the heart's rhythms become abnormal—typically too slow or exhibiting pauses in its function or a combination, and very rarely faster than normal ...
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]
The atrioventricular node or AV node electrically connects the heart's atria and ventricles to coordinate beating in the top of the heart; it is part of the electrical conduction system of the heart. [1] The AV node lies at the lower back section of the interatrial septum near the opening of the coronary sinus, and conducts the normal ...
Impulses from the sinus node reach the atrioventricular node which acts as the secondary pacemaker. The cells of the AV node normally discharge at about 40–60 beats per minute, and are called the secondary pacemaker. Further down the electrical conducting system of the heart is the Bundle of His.
Often sinus node dysfunction produces no symptoms, especially early in the disease course. Signs and symptoms usually appear in more advanced disease and more than 50% of patients will present with syncope or transient near-fainting spells as well as bradycardias that are accompanied by rapid heart rhythms, referred to as tachycardia-bradycardia syndrome [4] [5] Other presenting signs or ...
A sinoatrial block (also spelled sinuatrial block) [1] is a disorder in the normal rhythm of the heart, known as a heart block, that is initiated in the sinoatrial node.The initial action impulse in a heart is usually formed in the sinoatrial node (SA node) and carried through the atria, down the internodal atrial pathways to the atrioventricular node (AV) node. [2]
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 ...
An impulse (action potential) that originates from the SA node at a relative rate of 60–100 bpm is known as a normal sinus rhythm. If SA nodal impulses occur at a rate less than 60 bpm, the heart rhythm is known as sinus bradycardia. If SA nodal impulses occur at a rate exceeding 100 bpm, the consequent rapid heart rate is sinus tachycardia ...