Adenosine affects the heart by slowing down heart rate and the speed at which electrical impulses travel through the heart muscle. This mechanism is often used to treat supraventricular tachycardia (SVT).
Here's a more detailed breakdown:
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Decreases Heart Rate: Adenosine slows the firing rate of the sinoatrial (SA) node, the heart's natural pacemaker. This results in a slower heart rate.
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Slows Conduction Velocity: Adenosine decreases the speed at which electrical signals pass through the atrioventricular (AV) node, which is responsible for relaying signals from the atria (upper chambers) to the ventricles (lower chambers) of the heart.
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Mechanism of Action: Adenosine works by binding to adenosine receptors, specifically A1 receptors, on heart cells. This activation inhibits the flow of calcium ions into the cells, which are crucial for electrical conduction and muscle contraction. It also increases potassium efflux, hyperpolarizing the cell and making it more difficult to excite.
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Clinical Significance: Due to its effects on heart rate and conduction, adenosine is commonly used to treat supraventricular tachycardia (SVT), a condition characterized by a rapid heart rate originating above the ventricles. By slowing or temporarily blocking the AV node, adenosine can interrupt the abnormal electrical circuit causing the SVT and restore a normal heart rhythm. The effect is very short-lived, usually only lasting seconds.
In summary, adenosine exerts its effects on the heart by slowing heart rate and slowing conduction of electrical impulses, primarily by interacting with A1 receptors on heart cells. This makes it a valuable tool for treating certain types of rapid heart rhythms.
