quiz 5 2009

quiz 5 2009 - 1 The antiarrhythmic drugs Sotalol(Betapace...

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Unformatted text preview: 1. The antiarrhythmic drugs Sotalol (Betapace) and Lidocaine (Xylocaine) can both increase refractoriness. A. How would each drug affect the cardiac (His—Purkinje or myocardial) action potential? (2 pts) Sotalol- lengthen AP duration Lidocaine- shorten AP or no effect B. How would each drug affect the EKG ? (2 pts) Sotalol- Lengthen QT interval Lidocaine— no marked effect C. Which drug is most likely to induce an Early Afterdepolarization? (2 pts) Sotalol 2. The rate of automaticity is primarily determined by the rate of phase 4 depolarization. A. Sketch an action potential and indicate which portion corresponds to phase 4 depolarization. (2 Pts) 17 Lit—“Maia aim “flirt” [34.(‘5’iiirK/é‘ :5 //V E: M/ y .___.__—>, 2/ t s WA 3“ B. What channel is responsible for phase 4 depolarization, and what is “unusual” about this channel? (2 pts) l-lyperpolarization activated channei- it is activated at negative inward membrane potentials C. What tissue in the cardiac conduction pathway normally has the GREATEST rate of phase 4 depolarization and give one drug that can DECREASE it. (2 pts) Sinoatrial node— a beta blocker 3. Give a drug that fits each of the descriptions given below: A. Blocks K+, Na+, and Ca2+ channels and markedly increases QT interval. (1 pt) Amiodarone B. Does not DIRECTLY block any channel, but markedly increases PR interval. (2 pts) Adenosine or a beta blocker (Le. propranolol, metoprolol, csmolol) C. Markedly increases QRS duration, but does not increase QT interval. (2 pts) Any class 1C drug (Le. flecainide. propafenone, moricizine) D. Increases action potential duration via modulation of Na+ channel activity. (1 pt) lbutilidc 4. Antiarrhythmic drugs have a large constellation of potential toxic side effects. A. What is a fairly common and life threatening condition that can result from the use of Class III antiarrhythmic drugs? (2 pts) Torsade de Pointes B. What is a Class 1 drug that may also induce the life threatening condition that you gave in answer to A? (1 pt) Qunidine, procainamide, or disopyramide C. What antiarrhythmic drug can induce pulmonary fibrosis, thyroid hormone imbalance, and photosensitivity? (1 pt) Amiodarone D. What antiarrhythmic drug can induce a lupus-like autoimmune condition? (1 pt) Procainamide B. What antiarrhythmic drug can result in hypotension due to ganglion block? (1 pt) Procainamide 5. Calcium channel blockers are used to treat some type of arrhythmias. 1 A. What two specific calcium channel blockers are useful in treating arrhythmias? (2 pts) Diltiazem and Verapamil B. What is the specific component of the cardiac conduction pathway that is most critical in the efficacy of calcium channel blockers in the treatment of arrhythmia, and what effect do calcium channel blockers have on action potentials in this tissue? (2 pt) AV node- verapamil and diltiazem slow AP conduction through the AV node OR— increase refractoriness of the AV node C. Generally, what types of arrhythmias are treated with calcium channel blockers, and what is the effect of these drugs on the EKG? (2 pts) Verapamil and diltiazem can be used to treat atrial arrhythmias— they increase the PQ interval. 6. The cardiac glycoside digoxin can sometimes induce arrhythmias. A. Given what you know about the mechanism of action of digoxin, explain the mechanism whereby this drug induces arrhythmias. Include a sketch of the action potential in the presence of a toxic concentration of digoxin. (4 pts) /. (HQ km 0.1.. ' a I .4 /&‘”LI ‘ Dg‘lela/‘g‘i kw _ I I ’ .. a I A It a die/)tim- ié’t'éa a! U ' “‘7” ’le f/k’l/i/h *' ,t' l’ r ‘ .n thiigth ; I, Z V c], [l 4'4 lulqlx l . a i . i x . "A y k ( h r ‘( V. L' «M I E _i M a,» 71 llr‘limll'u'n J fr‘ifvi’tilci y ‘ u a a ‘3 t " “"6" ’ “W 3 ' ’t 7 k“ w r‘ w} B. Suggest a spec1fic drug that could resolve digoxin-induced arrhythmias, and explain the mechanism for it’s efficacy. NOTE- digibind is not an acceptable answer (2 pts). Beta blocker— this would inhibit the adrenergic up—regulation of calcium channel activity, reduce calcmm influx, and decrease calcium load. Class 11A drug» would inhibit Na+ channels and suppress automaticity. Also acceptable- MgClg ...
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quiz 5 2009 - 1 The antiarrhythmic drugs Sotalol(Betapace...

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