ps4_solutions

ps4_solutions - Harvard-MIT Division of Health Sciences and...

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Harvard-MIT Division of Health Sciences and Technology HST.542J: Quantitative Physiology: Organ Transport Systems Instructors: Roger Mark and Jose Venegas MASSACHUSETTS INSTITUTE OF TECHNOLOGY Departments of Electrical Engineering, Mechanical Engineering, and the Harvard-MIT Division of Health Sciences and Technology 6.022J/2.792J/BEH.371J/HST542J: Quantitative Physiology: Organ Transport Systems PROBLEM SET 4 SOLUTIONS March 9, 2004
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Problem 1 You are assigned to the Holter laboratory, and the Holter technician brings several rhythm strips to you, asking for advice. For each strip: Identify the arrhythmia as completely as possible. Draw the appropriate ladder diagram under each strip. A. Sinus arrhythmia. Normal finding. No symptoms expected. Image removed for copyright reasons. B. This is ventricular bigeminy, with three forms of VPBs seen. The VPBs are late-cycle, and do not interrupt the P-wave sequence. Since the cardiac rhythm is almost normal, it is quite probable that this arrhythmia would be asymptomatic. The patient might experience palpi- tations, however. It is considered clinically significant due to the possibility of developing more serious ventricular ectopic rhythm. Image removed for copyright reasons. 6.022j—2004: Solutions to Problem Set 4 2
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C. This is, on first inspection, sinus rhythm with APBs, one of which is conducted aberrantly with a classical RBBB pattern. Closer inspection of the P-wave morphology, however, sug- gests varying P-wave shapes and hence a wandering atrial pacemaker as the underlying rhythm rather than straight NSR. The patient might be aware of some palpitations due to the ectopic beats. (The beat following the pause will be more forceful due to increased filling time.) Image removed for copyright reasons. D. This is supraventricular tachycardia at rates of about 230 bpm. The ladder diagram shows the mechanism to be re-entrant process in the AV junction. (P-waves are not easy to identify without ambiguity.) At such a rapid heart rate, the patient would experience symptoms due to inadequate C.O. (insufficient diastolic filling time). There would be lightheadedness, possibly syncope, possibly CHF, S.O.B., pulmonary edema, chest pain, etc. Image removed for copyright reasons. 6.022j—2004: Solutions to Problem Set 4 3
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This is an agonal rhythm. There is complete heart block, with ventricular escape rhythm of only 15/min. This HR is probably inadequate to maintain BP and perfusion of vital or- gans. Patient would probably be unconscious, in shock, and would die unless rate could be increased by chronotropic drugs (atropine, isuprel) or pacing. Image removed for copyright reasons. F. This is low nodal rhythm. The HR is about 50 bpm, and should maintain adequate C.O. and BP, and would probably cause no symptoms. Image removed for copyright reasons.
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This note was uploaded on 11/11/2011 for the course BIO 2.797j taught by Professor Matthewlang during the Fall '06 term at MIT.

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ps4_solutions - Harvard-MIT Division of Health Sciences and...

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