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Your doctor may use the drug adenosine in a number of different procedures. Here’s what you need to know

Adenosine:
Class V Antiarrhythmic
Pregnancy category C

IT CAUSES HEART BLOCK, temporarily
HOW? the mechanism of action in heart electrophysiology: Causes transient heart block in the AV node, meaning that it prevents conduction of electrical impulses from the pacemakers down the rest of the heart because its a ligand for G-coupled protein receptor A1 which inhibits adenylate cyclase resulting in cell hyperpolarization by K efflux.

IT VASODILATES
Can lead to endothelial-dependent relaxation of smooth muscle via A2 stimulation stimulates adenylate cyclase inside the artery walls. This causes dilation of the “normal” segments of arteries, i.e. where the vessel wall is not separated from the tunica media or the muscle layer of the vessel by atherosclerotic plaque

THUS IT CAN BE USED IN SUPERVENTRICULAR TACHYCARDIA, CARDIAC STRESS TESTS, FRACTIONAL FLOW RESERVE STUDIES, PULMONARY VEIN ISOLATION

STRESS TESTS
Adenosine can test for blockages in the coronary arteries, by exaggerating the difference between the normal and abnormal segments. Therefore the adenosine causes increased blood velocity and flow rate in normal vessels and less of a response in stenotic vessels. This difference in response leads to a temporary steal of flow, and these exaggerated perfusion defects appear in cardiac nuclear scans or as ST-segment change in EKGs.

PULMONARY VEIN ISOLATION
Adenosine is used in pulmonary vein isolation to unmask dormant conduction foci along the pulmonary vein and decreasing the next for additional followup surgeries.

SUPERVENTRICULAR TACHYCARDIA ARRHYTHMIAS
used in SVT cardioversion as it puts the heart into asystole giving the heart a chance to get out of the arrhythmia and restart normal sinus rhythm on it’s own. Other sources say that adenosine slows conduction through the AV node and prevents re-entry pathways and thus allows the heart to re-enter normal sinus rhythm

FFR Measurements
fractional flow reserve: is the ratio between the maximum achievable blood flow in a diseased coronary artery and the theoretical maximum flow in a normal coronary artery. The procedure must be done in the setting of hyperemia with is achieved using adenosine, a vasodilator.

Side effects
Many individuals experience facial flushing, a temporary rash on the chest, lightheadedness, diaphoresis, or nausea after administration of adenosine due to its vasodilatory effects. Metallic taste is a hallmark side-effect of adenosine administration. These symptoms are transitory, usually lasting less than one minute. It is classically associated with a sense of “impending doom”, more prosaically described as apprehension. This lasts a few seconds after administration of a bolus dose, during transient asystole induced by intravenous administration. In some cases, adenosine can make patients’ limbs feel numb for about 2–5 minutes after administration intravenously depending on the dosage (usually above 12 mg).

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