Pathophysiology of cardiac disease and CHF Flashcards
How can you distinguish between heart disease and heart failure?
Heart disease is an abnormality which may not be causing any haemodynamically significant alteration.
Heart failure shows altered blood flow (CO, congestive = oedema)
Preload
The pressure caused by venous return to the heart
Afterload
The resistance or impedance to ventricular ejection during systole.
What are the major pathological consequences of congestive heart failure?
- Oedema and Effusions
- Peripheral vasoconstriction
- Tachycardia / Arrhythmias
- Remodelling and fibrosis of the myocardium
What neuro-hormonal events occur during congestive heart failure?
What are they stimulated by?
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Fall in blood pressure
- Cardiac beta1 increases heart rate
- JGA beta1 activates RAAS
- Vascular alpha1 leads to vasoconstriction
- Renin = reduced renal perfusion and Na conc
- Angiotensin II = vascoconstriction, myocardial remodelling
- Aldosterone = Na+ and H2O retention
- ADH = H2O retention
- Endothelin = vasoconstriction and myocardial remodelling
- ANP and BNP = oppose AT2 adverse effects
Outline starlings law of the heart.
Stroke volume increases linearly with Left EDVV up to a point where it levels off
With a diseased heart, how does the F-S law differ to that of a normal heart?
With a diseased heart the SV increases linearly, plateus and then decreases with increasing EDVV
Which substances cause vasoconstriction during heart failure?
- Alpha1 adrenoceptors
- Angiotensin 2
- Reduced bradykinin (ACE -> Kininase 2)
- Vasopressin (ADH)
- Endothelin
How does angiotensin 2 cause increased glomerular filtration pressure?
Causes greater vasoconstriction in the efferent vessels than afferent vessels within the glomerulus
Which substances cause remodelling of the myocardium and vascular smooth muscle cells?
- Angiotensin II
- Aldosterone
- Endothelin
- Catecholamines
Outline the signalling mechanism that causes myocardial remodelling.
- Catecholamines, angiotensin II and endothelin
- Activation of PLC
- Release of Ca2+ from the sarcoplasmic reticulum
- Activation of PKC
- Growth of the myocardium
Outline the La Place relationship.
Wall stress = Radius x pressure/ 2x Wall thickness
What is the difference between eccentric and concentric hypertrophy?
Eccentric - wall thickness stays the same, diameter of lumen increases
Concentric - wall thickness increases, lumen diameter decreases accordingly
What is the consequence of volume overload of a chamber of the heart?
In which conditions can this occur?
Eccentric hypertrophy
Conditions - Anaemia, valvular incompetence
What are the consequences of pressure overload on the heart?
In which situations does this occur?
Aortic stenosis and systemic hypertension
Concentric hypertrophy
