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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 ...
The sinoatrial node (SA node) is the primary pacemaker of the heart. It is a region of cardiac muscle on the wall of the upper right atrium near to the superior vena cava entrance. The cells that make up the SA node are specialized cardiomyocytes known as pacemaker cells that can spontaneously generate cardiac action potentials.
The sinoatrial node (also known as the sinuatrial node, SA node or sinus node) is an oval shaped region of special cardiac muscle in the upper back wall of the right atrium made up of cells known as pacemaker cells. The sinus node is approximately 15 mm long, 3 mm wide, and 1 mm thick, located directly below and to the side of the superior vena ...
Junctional rhythm is seen equally in men and women, and can be seen intermittently in young children and athletes, especially during sleep. It occurs commonly in patients with sinus node dysfunction. 1/600 cardiology patients over the age of 65 have sinus node dysfunction. [1]
It is one of the most important ionic currents for regulating pacemaker activity in the sinoatrial (SA) node. Ivabradine selectively inhibits the pacemaker I f current in a dose-dependent manner. Blocking this channel reduces cardiac pacemaker activity, selectively slowing the heart rate and allowing more time for blood to flow to the myocardium.
[18] [20] Since its first discovery, there have been many definitions of pacemaker syndrome, and the understanding of the cause of pacemaker syndrome is still under investigation. In a general sense, pacemaker syndrome can be defined as the symptoms associated with right ventricular pacing relieved with the return of A-V and V-V synchrony. [17]
Conduction is initiated by the sinoatrial node ("sinus node" or "SA node"), and then travels to the atrioventricular node ("AV node") which also contains a secondary "pacemaker" that acts as a backup for the SA nodes, then to the bundle of His and then via the bundle branches to the point of the apex of the fascicular branches.
These conditions can be caused by damage to the native sinus node itself and are frequently accompanied by damaged AV node conduction and reduced backup pacemaker activity. [15] The condition can also be caused by dysfunction of the autonomic nervous system that regulates the node and is commonly exacerbated by medications. [2]