Pathophysiology of Cardiac disease and congestive heart failure Flashcards
Define a heart failure.
- A clinical syndrome caused by heart diseases resulting in systolic and / or diastolic function severe enough to overwhelm the normal compensatory mechanisms, resulting in:
Poor cardiac output and reduced peripheral perfusion (FORWARDS
failure)
and / or
Elevated filling pressures, resulting in oedema and effusions
(BACKWARDS, CONGESTIVE failure).
What are the 4 major consequences of CHF?
- Oedema and Effusions
- Peripheral vasoconstriction
- Tachycardia / Arrhythmias
- Remodelling and Fibrosis of the Myocardium
What are endogenous counteractions to the RAAS system?
Natriuretic peptides
* Atrial natriuretic peptide, ANP.
released due to atrial stretch
* Brain natriuretic peptide, BNP
released from ventricles, due to increased ventricular pressure
* Other natriuretic peptides:
CNP, Urodilatin, Adrenomedullin
How does oedema and effusions occur?
*Excessive Na+ and H2O retention
-try to increase preload to increase CO
Why does peripheral vasoconstriction occur?
- Homeostatic priority of the body, to maintain blood
pressure, even at expense of increased filling pressures. - Arterioconstriction maintains blood pressure.
- Venoconstriction increases pre-load, so venous return to
heart, and utilisation of the Frank-Starling mechanism.
What are the mediators of peripheral vasoconstriction?
- Sympathetic nervous system: 1 receptors (noradrenaline).
- Angiotensin II
- Reduced bradykinin levels (ACE = Kininase II)
- Vasopressin (ADH)
- Endothelin
What is the effect of angiotensin ii on the kidney?
*Causes greater efferent arteriole constriction than afferent arteriole constriction
= increased glomerular capillary pressure
ACE inhibitors counteract adverse effects of angiotensin ii. What does ACE inhibitors do?
- Balanced vasodilators
- Reduce aldosterone release, so reduced Na+ & H2O retention
- Reduce glomerular capillary pressure
- Prevent Angiotensin II mediated myocardial fibrosis and remodelling
- Permissive anti-adrenergic effects
- Reduce vasopressin release
- Reduce endothelin release
What does increased aldosterone result in?
*Increased Na+ & H2O retention
*Myocardial remodelling and fibrosis
What is an aldosterone antagonist?
Spironlactone
What hormones can cause remodelling of myocardium and vascular smooth muscle cells?
- Angiotensin II
- Aldosterone
- Endothelin
- Catecholamines
What is eccentric hypertrophy, what is it caused by, what happens, and what is an example where is occurs?
*Dilation of the ventricle
*Caused by volume overload
*E.g Mitral regurgitation
What is concentric hypertrophy, what is it caused by, what happens, and what is an example where is occurs?
*Increased thickness of ventricular wall
*Caused by pressure overload
*E.g Aortic stenosis
What can cause volume overload?
*Exercise - isotonic (marathon)
*Anaemia
*Valvular incompetence
What can cause pressure overload?
*Exercise - isometric (Sprint/weightlifting)
*Aortic/pulmonary stenosis
*systemic hypertension (LV)
*Pulmonic hypertension (RV)
