T3 - Heart failure Flashcards
what is heart failure the impaired ability of?
ventricular ejection (systolic) and filling (diastolic)
what is the CO equation?
CO = HR x SV
what is stroke volume?
amount of blood pumped out the LV per beat
what is something that would increase preload?
increased blood volume and vasoconstriction
what is something that would decrease preload?
vasodilation and decreased blood volume
what is pre load?
pressure the heart is under before it contracts (volume of blood stretching the cardiomyocytes at the end of diastole)
what is after load
resistance the heart must work against to eject blood
in what situation will there be a decreased CO even though HR is high and why?
arrhythmia
- not enough time for ventricular filling therefore decreased stroke volume and cardiac output
what describes the relationship between preload and CO?
frank starling law
describe how a large increase in preload can decrease cardiac output
cardiomyocytes can be too much which reduces in less contraction and therefore less cardiac output and less stroke volume
what is high output heart failure?
heart function is normal but cant meet high body demands (due to a medical condition)
what can cause high output heart failure?
thyrotoxicosis (lots of thyroid hormones), anaemia, pregnancy, pagers disease, acromegaly, sepsis
what are the two types of low output heart failure?
systolic and diastolic
what is systolic heart failure and what are the three main causes?
progressive deterioration of myocardial function
- caused by ischaemic injury, volume overload and pressure overload
what is diastolic heart failure?
inability of the chamber to relax or expand and fill during diastole to reach an adequate blood volume
what type of heart failure has a normal ejection fraction but cant fill properly?
low output diastolic heart failure
what are four causes of diastolic heart failure?
LV hypertrophy, infiltrative disorders, constrictive pericarditis, restrictive cardiomyopathies
give five broad causes of heart failure
coronary heart disease, hypertensive heart disease, valvular heart disease, myocardial disease/cardiomyopathy or congenital heart disease
what is a cardiomyopathy?
diffuse disease of heart muscle that leads to functional impairment
how is cardiomyopathy characterised?
- heart muscle of stretched, thick or stiff
- dilated hypertrophic or restrictive
what proportion of dilated cardiomyopathies are familial and what does this cause?
50% are familial and this triggers T cell mediated inflammation in the heart
what type of cardiomyopathy can myocarditis cause?
dilated CM
what type of cardiomyopathy is caused by amyloid and what does this result in?
restrictive CM
- results in stiff walls and impaired filling
what are the three compensation mechanisms in HF that maintain arterial pressure and perfusion to organs?
1) frank starling - vasoconstriction to increase venous return therefore increasing preload, stretch and FOC
2) myocardial structure change - hypertrophy
3) neurohumoral system - NA release increases HR and FOC, atrial and B type naturietic peptide increase HR as well as activating RAAS
what stimulates activation of the RAAS?
low CO and therefore low BP
what does activation of the RAAS cause?
- increased sympathetic input
- increased aldosterone which therefore increases Na+ retention and vasoconstriction - not good in HF
what three compensatory mechanisms from a normal healthy heart can worsen HF?
- vasoconstriction - increases resistance heart pumps against therefore increasing after load and decreasing CO
- Na/H20 retention (via aldosterone) - increase in fluid volume increases preload which increases stretch in the heart which decreases FOC and CO
- tachycardia - decreases diastolic filling time therefore decreased ventricular filling therefore reducing SV and CO
what does pressure overload cause?
- concentric left ventricular hypertrophy
- stretched muscle therefore decreased cavity diameter
- thick walls and lower atrial/ventricular volume
what does volume overload cause?
- chamber dilation with increased ventricular pressure
- deposition of new sarcomeres with increased length and width
- very dilated ventricles with thin muscular walls but increased muscle mass in proportion to chamber diameter
what causes pressure overload?
high blood pressure or aortic stenosis
what causes volume overload?
mitral or aortic regurgitation
what three ways can heart failure be categorised?
- which side (L, R or biventricular)
- acute or chronic
- compensated (handle compensation mechanisms with treatment) or decompensated (previously compensated now unwell again)
where does the back up of blood come from that causes LHS HF and where does this cause congestion?
back up of blood from LA which goes back into pulmonary circulation causing congestion in the lungs
what are four causes of LS HF?
iscahemic heart disease, valvular heart disease, hypertension and myocardial disease
what does pulmonary congestion due to LSHF result in (O2 diffusion distance)?
increased O2 diffusion distance, harder to breathe and wet lungs
what are the symptoms of wet lungs due to LSHF?
dyspnoea on exertion, orthopnea (relieved by sitting or standing), paroxysmal nocturnal dyspnoea
what effect does LSHF have on the kidneys?
lower CO means lower renal perfusion which causes activation of RAAS
- increased aldosterone and Na+ retention
- increased blood volume and interstitial fluid
what are the brain symptoms from LSHF?
- less specific
- hypoxic encephalopathy (brain injury due to O2 deprivation)
- irritability/attention loss
- restlessness
- coma
what is the main cause of RSHF?
LSHF (congestive)
what is cor pulmonale and what causes it?
enlargement of the RHS of the heart due to lung disease
- often caused by respiratory disease eg COPD or PE
apart from cor pulmonale, what are two other causes of RSHF?
valvular heart disease and congenital heart disease
what effect does RSHF have on the
i) liver
ii) spleen
iii) abdomen
iv) subcutaneous tissue
v) pleura and pericardium
I) congestive hepatomegaly, lobar necrosis and cardiac cirrhosis ii) congestive splenomegaly iii) ascites iv) oedema v) effusions (anything with lots of fluid)
what are the two causes of biventricular heart failure?
1) same pathological process on each side of the heart
2) as a consequence of LSHF - volume overload in the pulmonary circulation which causes RSHF
what is the clinical presentation of biventricular HF?
- excess fluid accumulation (dyspnoea, orthopnea, oedema, ascites)
- reduced CO causing fatigue and weakness
what are 10 clinical signs of HF
- cool/pale/cyanotic extremities
- tachycardia due to increased sympathetic activity
- elevated JVP
- 3rd heart sound (galloping)
- displaced apex due to LV enlargement
- crackles or decreased breath sounds
- ascities
- peripheral oedema
- hepatomegaly
what can be measured when testing for HF?
NT-pro BMP levels - if normal it probably isn’t HF
