20 points) A patient with congestive heart failure is suffering from poor cardia
ID: 3523584 • Letter: 2
Question
20 points) A patient with congestive heart failure is suffering from poor cardiac output. Her ejection fraction is 40%. As a result, her organs are poorly perfused with oxygenated blood and she tires easily. a. What is ejection fraction, how is it calculated, and how does her ejection fraction compare to that of a normal, healthy heart? b. Cardiac output may be improved by increasing the strength of ventricular contractility. Explain how contractility could be increased in cardiac muscle cells. Focus on how muscle fibers produce tension and how that tension can be increased during muscle contraction. (Hint: Ca2+ ions are important here).
Explanation / Answer
a. What is ejection fraction, how is it calculated, and how does her ejection fraction compare to that of a normal, healthy heart?
Answer: An ejection fraction (EF) is the volumetric fraction of fluid blood ejected from a chamber of the heart with each contraction.
it is calculated as EF% = SV/ EDV * 100
{ SV= EDV-ESV}
EF- EJECTION FRACTION
SV- STROKE VOLUME
EDV- END DIASTOLIC VOLUME
ESV- END SYSTOLIC VOLUME
Normal value: equal to or >50%. Hence, her EF% is less compared to a normal healthy heart. according to the European Society of Cardiology Guidelines for the diagnosis and treatment of acute and chronic heart failure 40- 49% is considered acute cardiac failure and <40% is considered as chronic heart failure.
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Explain how contractility could be increased in cardiac muscle cells. Focus on how muscle fibers produce tension and how that tension can be increased during muscle contraction. (Hint: Ca2+ ions are important here).
Answer: Increasing contractility is done primarily through increasing the influx of calcium or maintaining calcium at high levels in the cytosol of cardiac myocytes during an action potential. this can be achieved by Sympathetic activation. Increased circulating levels of catecholamines, as well as stimulation by sympathetic nerves, causes the Gs subunit of the receptor to render adenylate cyclase activated, resulting in the increase of cAMP.
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