Beta-blockers in heart failure
β-blockers decrease the compensatory mechanisms of increased sympathetic activity by blocking the β-receptors on the excitable cells in the myocardium and blood vessels. A blockade of these receptors results in decreased cardiac contractile activity, decreased heart rate and cardiac output, decreased blood pressure, and decreased peripheral circulation.
All these effects reduce the oxygen demand of myocytes. They are therefore considered to inhibit the neurohormonal cascade that leads to progression of heart failure.
β-blockers inhibit the formation of the impulses in the SA node by:
Extra info: As shown in the graph, patients receiving β-blockers are slower in reaching the threshold for initiating a new impulse.
What is NOT true about digoxin toxicity
Extra info: Unfortunately patients do not develop tolerance to the adverse effects of digoxin. Digoxin toxicity corresponds with serum concentration.
The mechanism of β-blocker action does NOT include