miscellaneous antiarrhythmics

Question 1

MoA of ADENOSINE

Answer 1

• Activates Adenosine 1 recetpors in SA and AV nodes
• activates cAMP-independent, Ach/Ado-sensitive K+ channels

–> SA node hyperpolarization and Decreased firing rate

–> shortening of AP duration of atrial cells

–> depression of A-V conduction velocitiy

• Activates Adensoine 2 Receptors in vasculature
• actiavtion of K+ channels

–> increased endothelial Ca2+ = Increased NO

–> smooth muscle hyperpolarization = VASODILATION

Question 2

describe clinical application of adenosine

Answer 2

• Very effective for ACUTE conversion of paroxysmal supraventricular tachycardia caused by reentry involving accessory bypass pathways

–> must use as IV bolus to a central vein (brachial, antecubital) because half life = 10-15 seconds

–> enzymatic metabolism in erythrocytes and vascualr endothelium

• ADVERSE EFFECTS:

–> hypotension, flushing, complete heart block, CNS effects, Dyspnea (very short lived)

Question 3

describe the management of bradycardia

Answer 3

• atropine = produces a vagal block to increase HR
• Isoproterenol = Beta1-stimulated increase in HR
• Pacemaker

Question 4

describe the management of sinus tachycardia (PSVT_

Answer 4

• vagal stimualtion t hrough carotid sinus massage or valsalva maneuver