heart failure: tutorial Flashcards
What is congestive heart failure (CHF)?
Congestive heart failure is a progressive condition where damage to one (most commonly the left) or both of the ventricles impairs the ability to maintain cardiac output.
Pulmonary oedema is a cardinal sign of CHF, involving, primarily, the left ventricle. Use your understanding of Starling’s principle of fluid exchange to suggest how left ventricle failure leads to pulmonary oedema.
There will be less blood pumped out of the heart from the pulmonary veins (as they eventually lead into the left ventricle), so there will be less cardiac output.
That means there will be a gathering of fluid in the lung area, increasing the hydrostatic pressure inside the blood vessels This leads to more fluid being let out of the vessels, causing pulmonary oedema
Peripheral oedema (eg. legs, feet) is often present with right or biventricular failure. Explain.
There is not enough blood being oxygenated, as the right ventricle cannot pump efficiently to the lungs.
This means that there is a build-up of blood in the veins/capillaries, causing an increase in the hydrostatic pressure.
This overcomes the osmotic pressure and favors more filtration into the interstitial fluid, causing peripheral oedema.
Hypertension is a risk factor for CHF. Using Laplace’s Law in the context of cardiovascular physiology, explain how long-term hypertension may lead to CHF.
Hypertension increases your blood pressure, so the arterial blood pressure will rise.
With the increased arterial pressure, we need more pressure inside the ventricles to open the aortic valve. The way to increase the pressure to such levels would be to increase the blood volume; this effectively also increased ESV and EDV.
With Laplace’s Law, as there is now more volume in the ventricles, this means that the radius of the ventricles has increased. With an increased radius, there is more wall stress in the chamber. There is an increased afterload, and the heart has to pump harder in order to get the blood out of the chamber. This means that the heart muscle is working more, so ventricular hypertrophy will occur. This means that the heart will spend more time in contraction, which, over time, can lead to heart failure.
