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NBME 20 Answers

nbme20/Block 2/Question#49

An 82-year-old woman is brought to the physician ...

Decreased slope of diastolic depolarization

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submitted by dbg(23),

BBs work by decreasing cAMP and Ca2+ thereby slowing SAN & AVN activity. This prolongs phase 4 of depolarization. Therefore, they are known to increase the duration of diastole (predominantly) causing both a rise in heart coronary perfusion and reduction in heart rate.

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submitted by hayayah(399),

Beta blockers as antiarrhythmics suppress abnormal pacemakers by decreasing the slope of phase 4 --> prolonging phase 4.