Why is procainamide (Pronestyl) recommended in refractory wide complex tachycardia? A It prolongs the QT interval B It prolongs the PR interval C It shortens the QT interval D It shortens the PR interval
Added by Theresa B.
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Procainamide is a Class IA antiarrhythmic drug that works by blocking sodium channels, which slows conduction velocity and prolongs the action potential duration. Show more…
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A patient has tachycardia. Would you recommend a drug that prolongs or shortens the plateau of cardiac muscle cell action potentials?
Sri K.
Q1) The electrical events of the atria and ventricles are isolated from each other. a) So that the ventricles do not excite the atria. b) To prevent the backflow of blood between the chambers. c) So that the left and right sides of the heart have the same cardiac output. d) So that atrial contraction can finish before a ventricular contraction begins. e) So that the ventricular contraction terminates during the refractory period of the Na+ channel. Q2) What will happen if the parasympathetic nervous system secretes acetylcholine onto the sinoatrial node of the heart? a) The Na+ channels inactivate. b) There will be an increase in K+ permeability across the plasma membrane of the sinoatrial node. c) The action potential frequency will increase. d) Blood will stop flowing through the chambers of the heart. e) The funny current begins moving ions in the opposite direction. Q3) The transverse (t-) tubule system of skeletal muscle is an important structure that a) Allows a high frequency of action potentials to excite the muscle. b) Allows the fiber to be highly elongated. c) Allows action potentials to propagate rapidly into all areas of the fiber. d) Is an important source of Ca2+ ions. e) Allows action potentials to be brief in skeletal muscle. Q4) An important role of the Na+-Ca2+ exchanger in cardiomyocytes is to a) Allow influx of K+ ions during the diastolic phase. b) Directly move Ca2+ ions into the sarcoplasmic reticulum. c) Translocate Ca2+ ions from the cytoplasm to outside the cell in the diastolic phase. d) Repolarize the cell. e) Activate release of Ca2+ ions through the ryanodine receptor.
Caryl A.
Select the correct statement from the following: (a) ECG is of great clinical insignificance. (b) By counting the number of QRS complexes (in given time period), we can the find pulse rate. (c) The contraction of atria starts with starting of $\mathrm{Q}$ wave. (d) T-wave represent repolarization of atria.
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