Beta-blockers are prescribed to reduce the frequency of cardiac arrhythmias. They do this by:

Question

BlackTom AI · Accepted Answer

Examining how beta-blockers work to reduce the frequency of cardiac arrhythmias involves understanding their primary pharmacologic effects.
Option a: 'Increasing contractility of the heart ventricles' would be a positive inotropic effect. In fact, beta-blockers produce a negative inotropic effect (decrease contractility) in many settings, so this choice describes the opposite of what these drugs do and is misleading as a mechanism for reducing arrhythmias.
Option b: 'Increasing systemic vasoconstriction' would raise peripheral vascular resistance. Beta-blockers do not act primarily by vasoconstriction; in many cases they can reduce sympathetic drive to the heart without causing significant systemic vasoconstriction, so this option does not explain how they reduce arrhythmias and is not a recognized principal mechanism.
Option c: 'Lowering heart rate' directly reduces the heart’s excitability and slows conduction through the atrioventricular node, which helps prevent and lessen the frequency of arrhythmic events. This aligns with the standard therapeutic effect of beta-blockers in rhythm control and antiarrhythmic strategy.
Option d: 'Increasing cardiac output' would imply an enhancement of the heart’s pumping capacity. Beta-blockers commonly decrease heart rate and can reduce or preserve cardiac output depending on the clinical context; they are not prescribed to increase cardiac output to prevent arrhythmias, so this does not describe the mechanism.
In summary, the statement that matches the primary mechanism by which beta-blockers help reduce arrhythmias is that they lower the heart rate, since this slows cardiac activity and stabilizes electrical conduction, thereby decreasing the frequency of arrhythmic episodes.

Beta-blockers are prescribed to reduce the frequency of cardiac arrhythmias. They do this by:单项选择题

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