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WEEK 20:
System Pathology: Heart Failure:
| Question | Answer |
|---|---|
| most important site for renin release | kideny |
| renin | enzyme acting uppon circulating substrate, angiotensinogen that undergoes proteolytic cleavage to from the decapeptide angiotensin I |
| where can ACE be found | in vascular endothelium (in lungs) which cleaves off 2 amino acids to form octapeptide and angiotensin II (ATII) |
| function of ACE enzyme | cleaves off 2 amino acids to form octapeptide and angiotensin II (ATII) |
| what can stimulate release of renin from kidney from juxtaglomerular apparatus (JGA) (3) | sympathetic stimulation (b-adrenoceptors), renal artery hypotension, and decreased sodium delivery to distal tubules |
| main problems leading to heart failure | fluid congestion (backward failure) and inadequate blood flow to tissues (forward failure) |
| heart failure types | chronic or acute |
| acute heart failure | events take place rapidly and consequence is forward failure (shock) |
| chronic heart failure | compensatory mechanisms may be brought into play and backward failure dominates (congestion) |
| compensatory mechanisms used in left ventricular dysfunction (3) | muscle mass increases, ventricular chamber enlargement, and sympathetic stimulation |
| why does muscle mass increase as a compensation for LVHF | allows heart to eject more blood but requires more oxygen to supply increased muscle mass |
| why does ventricular chamber enlargement occur as a compensation for LVHF | increases amount of blood in ventricle, so ejects more (frank starling law) but at cost of fluid retention |
| sympathetic stimulation occurs as a compensation for LVHF leading to | increased HR, contractility, redistribution and retention of fluid |
| other types of heart failure (3) | LVF, RVF, and congestive cardiac failure |
| most common type of heart failure | left sided heart failure |
| forward failure | inadequate flow of oxygenated blood to tissues |
| backward failure | fluid congestion where blood coming from lungs to heart gets backed up leading to pulmonary oedema |
| explain what left ventricular failure leads to | raised end diastolic pressure -> raised left atrial pressure -> raised pulmonary capillary pressure -> increased diffusion barrier for gas exchange and increased interstitial fluid formation (pulmonary oedema) -> breathlessness |
| appearance of oedema in alveolar spaces | normally contain no stainable material and alveolar walls are congested by this fluid |
| causes of LVF | ischaemic heart failure, longstanding hypertension, valve disease (aortic and mitral - valve not opening ((stenosis)) and valve not closing ((valce incompetence))), cardiomyopathies and congenital heart disease |
| stenosis | valve not opening |
| valve incompetence | valve not closing |
| right ventricular failure | occurs often as a result of lef sided failure |
| explain what right ventricular failure leads to | raised end diastolic pressure -> raised right atrial and jugular venous pressures -> raised central venous pressure -> liver distension (abdominal discomfort) and increased interstitial fluid formation (peripheral oedema) |
| nutmeg liver refers to | seen more in right heart failure - speckled appearance of cut liver in chronic venous congestion due to dilated and congested red central veins surrounded by paler unaffected liver tissue |
| causes of right ventricular failure | as a result of left ventricle failure |
| acute right ventricular failure | due to chronic lung disease and pulmonary hypertension (Cor pulmonale) |
| cor pulmonale due to | pulmonary emphysema (which destroys alveolar walls leading to fewer lung capillaries and worse lung ventilation leading to hypoxia which constricts pulmonary arteries leading to pulmonary hypertension) |
| congestive cardiac failure | combination of both left and right ventricular failure with the most common cause being ischaemic heart disease |
| most common cause of congestive cardiac failure | ischamic heart disease |
| high output cardiac failure | heart muscle essentially normal but output cannot adequately perfuse tissue |
| arteriovenous fistula | short circuits circulation and forces heart to pump more blood overall to deliver usual amount of blood to vital organs |
| anaemia | needs heart to pump more blood each minute to deliver enough oxygen to tissues of body |
| some causes of high output cardiac failure (3) | arteriovenous fistula, anaemia, and thyrotoxicosis |
| thyrotoxicosis | increases body's overall metabolism thus increasing demand for blood flow |
Created by:
kablooey
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