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quiz 5 2008 - MCMP 408 Quiz 5— April 3 2008 1 Give an...

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Unformatted text preview: MCMP 408 Quiz 5— April 3, 2008 1. Give an antiarrhythmic drug that fits the following electrophysiological profiles. There may be more than one correct answer in each case, but you need only give one. However, some drugs may be only partially correct, so choose wisely! It may help to jot down your reasoning as you think about these questions. A. Drug A markedly broadens the QRS complex of the EKG, slows phase 0 of the cardiac action potential in ventricular myocytes, and does not lengthen action potential duration. {Brag A is: Flccaiaifie, 1.1".mricizine, or pmpaibnonc B. Drug B markedly increases the action potential duration in ventricular myocytes, and has no effect on the QRS complex or the PR interval of the EKG. $273242; B is: dofeiilide. ibutiiidc, or bretyiium C. Drug C markedly increases the PR interval of the EKG, decreases SA nodal rates, but is used almost exclusively to treat supraventricular arrhythmias. Drug C is: Verapamii or (iiitiazcm 2. Using the diagram below, left, representing a cross section of a heart, indicate the names of the structures labeled A, B, C, and D. (4 pts) Indicate the normal pathway of action potential conduction by indicating the origin, and using arrows to indicate direction on the diagram to the right (2 pts). or Hf; 'prll-(XSQ éyfivem , Rim, 174d” Qic. 3. Match the toxicity listed on the left with the drug listed on the right. Each answer may be used once, more than once, or not at all. (1 pt each) i Pulmonary fibrosis A. Dofetilide (Tikosyn) _Q_ Hypotension B. Amiodarone (Cordarone) #Q_ Lupus Erythematosis-like syndrome C. Procainamide (Procan) _D__ Anti-muscarinic activity D. Quinidine i Hypothyroidism E. Lidocaine (Xylocaine) _A_ Most severe risk of Torsade de Pointes F. Propranolol (Inderal) 4. Atrial arrhythmias are often not treated if the patient is asymptomatic. A. Give two reasons for this. (2 pts) Atrial arrhythmiaé; uszzally don‘t markediy affect CO Antirarrhythmic drugs can. induce arrhythmias or have other toxicities B. Why are ventricular arrhythmias considered, in general, to be more serious than atrial arrhythmias? (2 pts) "they can, greatly decrease or entirely stop cardiac output. C. What is the proper pattern (or direction) of action potential conduction that must be maintained for optimal ventricular function? (2 pts) if":‘<.>pagation of action potentials spreading; through the al’entricular walls from the imtmm up. 5. Explain the mechanism by which beta adrenergic receptor antagonists may suppress ectopic pacing induced by: A. Early aftcrdepolarizations (2 pts)- lfiAlBs arise from activation eftf’a“ channels; during a prolonged plateau phase. Blockiag tire adrenergic Stimulation. of channel activity can 'i‘tftiitijt‘) the probalaility that {Ta2+ Channels; will open during the prelmlged plateau phage, B. Delayed afterdepolarizations (2 pts)- DAELBS arise as a result of {IIfzi"" ovetload Er; the myocartléum. iiitieelting adrenergie w v t at 2+ . ., . . . N . . , . stmmlatitm of. {a ehamel activity can refiner: the £1“leth at (a daring depeéarzaattens "ta t, w 42 and petetztéally reduce the amaunt of <1. a C. What effect will beta adrenergic receptor antagonists have on: 1. SA nodal rate of automaticity (1 pt) lfieerease rate 2. AV node refractoriness (1 pt) increase refractoriness 6. Lidocaine (Xylocaine) is very effective in suppressing ectopic pacemakers that arise as the result of ischemic damage to cardiac tissue. A. What are two properties of lidocaine block of cardiac sodium channels that allow it to suppress ectopic pacing without markedly affecting the electrical properties of surrounding healthy tissue? (2 pts) Volt:age—-t§epen<lence of sodium channel eéeclt. (E. pt) Frcquencydependeace of Sodium channel, hloeis: t "l pt) Ora l33§31d3 to the inactivated state ofttte sodium ehaaael (1 pt} and aabénds at hyperpolarimd (negative) potentiaia (E pt). B. How can lidocaine increase the refractoriness of cardiac tissue without lengthening the cardiac action potential? In your answer, explain what determines refractoriness, and how lidocaine affects that process. (4 pts) Refractoriness is determined. E33: recovery ofsz eitaméela from éltaeti'vatirm (opei‘iing of %:--f~ga’te$). (lpt‘) Eridoeaéne binds to the inactivated State of the channels { Emiégates shut). and the channels can‘t reetwer fmm i122t£€l¥£ltl0§l until iidoeaine comes {all} M), so the "#03?th at which recovery 'l‘l’t'm‘é inactivatim oecars is more negative than in the absence otdmgl l pt}. it takes leager to reach. tl‘aéa :tzore negative voltage, resulté 13;; in. an increase in the refractory period. t 1 pt} ...
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