Heart Rate ..Part 3 ..Beta blockers as good agents

An important distinction needs to be made between specifically reducing heart rate vs. what is more typically done,which is reduction of heart rate with a Beta-adrenergic blocker.

Besides decreasing heart rate,B-adrenergic blockade also can decrease cardiac contractility, alter metabolism, lead to decreased arterial resistance, and increase venous vascular resistance.The response to Beta-blockade is thus an integration of all these effects.

Because heart rate is such an important determinant of myocardial oxygen demand, reduction of maximum heart rate as well as prevention of surges in heart rate make good sense in patients with fixed coronary obstructions and limitations in the coronary supply of oxygen.

A series of studies showed beneficial effects of Beta-adrenergic antagonists in patients after myocardial infarction.

There is also evident improvement in clinical symptoms and an improvement in work capacity with use of Beta-adrenergic blockers in patients with stable angina.

However, a more complicated picture arose when Beta-adrenergic blockade was used to prevent cardiac
ischemic events in large populations at lower risk.

In the next post post we will discuss the another aspects of Beta Blockers effects.

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The pressure volume loop...

In the pressure-volume loop below, cardiac work is best represented by: the area of the curve the slope of the line from points C to D the distance of the line from points C to D the slope of a line from points A to D .. .. ... .... ... .... .... .... In the pressure-volume loop below, cardiac work is best represented by: the area of the curve Cardiac work is the product of pressure and volume and is linearly related to myocardial oxygen consumption. Cardiac work is best represented by the area of the curve of a pressure-volume loop.

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