Pathophysiology of CVS Disease Flashcards
Define Heart Failure
A complex syndrome initiated by an inability of the heart to maintain a normal CO at normal filling pressures.
What is the difference between Heart Failure and Heart disease?
Heart failure has clinical signs associated with it. Not all heart disease leads to heart failure, but heart failure is caused by many types of heart disease.
What are forward and backward heart failure?
Forward HF is inadequate output at normal pressures, backward HF is adequate output at abnormal pressures.
What are the 5 potential causes of HF? (very broad categories)
Pump failure (systolic dysfunction), Volume overload, pressure overload, diastolic dysfunction, and arrhythmias.
What do all causes of HF have in common?
All have the final common pathway leading to underfilling of arterial circulation, which initiates endocrine and neural adaptations.
What are the nervous effects of heart failure?
Sympathetic dominance as heart tries to increase CO. Beta r on heart increase rate and contractility, a receptors on vasculature cause increased vascular resistance.
What are the endocrine effects of heart failure? (3)
RAAS (to increase volume), ADH (to increase volume), Naturetic peptides (to decrease volume)
How does the RAAS system try to help ‘fix’ heart failure?
Vasoconstriction and aldosterone secretion (sodium retention, and therefore water) try to increase BP, by increasing CO and increasing TPR.
How does ADH release try to help ‘fix’ heart failure?
Free water retention to try increase CO. Stimulus for “non-osmotic” release of ADH is probably decreased BP. May lead to dilutational hyponatremia.
How does Naturetic peptide release try to help ‘fix’ heart failure?
NPs are released by myocardium in response to too much cardiac wall chamber stress. Try to decrease the amount of blood in the chambers. In HF, excess circulating blood volumes, however, this gets overwhelmed by RAAS and ADH.
In the long term, how do the compensations of the nervous system and endocrine system make heart failure worse?
Excessive fluid retention increases cardiac filling pressures. This leads to increased cardiac work, due to increased afterload, HR and contractility.
What causes concentric hypertrophy of the myocardium?
Pressure overload of chambers e.g. hypertension, aortic/pulmonic stenosis.
What causes eccentric hypertrophy of the myocardium?
Volume overload of chambers e.g. mitral regurgitation, shunting.
Why can hypertrophy of the myocardium make the myocardial dysfunction worse?
Increase myocardial mass, increased myocardial oxygen demand. Coronary arteries cannot keep up, and this can lead to ischaemia and regional hypoxia.This leads to more dysfunction = VISCOUS CIRCLE.
Oedema is excess extracellular fluid. In what 4 ways can it form?
1) Increased hydrostatic pressure, 2) increased vascular permeability, 3) decreased plasma oncotic pressure, 4) decreased lymphatic drainage.
