Pathophysiology

Question 1

What does HF cause on physiological level?

Answer 1

HF causes drop in MAP (Mean Arterial Pressure) that initially stimulates baroreceptors that feed back into the Medullary Cardiovascular Center(MCVC). MCVC tries to increase and maintain the MAP by reducing vagal tone and increase sympathetic tone leading to increased heart contractility and rate. The sympathetic system also stimulates the contraction of arteries (increasing TPR) and stimulate all of the above actions.

Question 2

The Renin-angiotensis-system (RAS) input in HF

Answer 2

RAS (hormone system that regulates BP, fluid and electrolytes balance) is stimulated in HF due to reduced kidney perfusion caused by reduced MAP & vasoconstriction & direct sympathetic stimulations. When renal blood flow is reduced, renin is secreted. End product of Angiotensin 2 causes vasoconstriction and water and sodium retention (through stimulating the secretion of the hormone Aldosterone causing reabsorption of sodium/excretion of potassium) by kidneys, resulting in high BP.

If the RAS is abnormally active, blood pressure will be too high

Question 3

Side effects of increased TPR

Answer 3

• increased afterload therefore increasing workload and strain on the heart
• tissue underperfusion leading to ischemia
• RAS system stimulation

Question 4

Side effects of increased HR

Answer 4

Increased workload = increased Oxygen demand

Question 5

Side effects of Fluid Retention

Answer 5

• Increase stretching of the heart eventually leads to dilatation of ventricles = reduced contractility
• fluid build up causes fluid transudation causing Peripheral and Pulmonary Oedema.
• Hyponatremia and Hypokalemia