Cardiovascular strand: Lecture 11 - Cardic haemodynamics/ heart failure Flashcards
How do you calculate cardiac reserve?
Cardiac reserve = maximal cardiac output - cardiac output at rest
What is preload?
The level of stretch that a cardiomyocyte is exposed to before ventricular ejection - measured best by LV end diastolic volume
What is afterload?
Afterload is the pressure the heart must work against to eject blood during systole (ventricular contraction)
Why is reduced CO dangerous?
reduced organ perfusion
What is the baroreceptor reflex to reduce heart rate, stroke volume and cause vasodilation?
- via autonomic nervous system
- arterial stretch sensed
- afferent loop ends in nucleus tractus solitarius and rostral ventrolateral medulla
- reduces sympathetic tone
- augments vagal tone (increases activity of vagus nerve) which reduces HR (beta), reduces SV (beta) and causes vasodilation (alpha)
What is the juxtaglomerular apparatus?
- renal perfusion pressure sensed at glomerulus
- sodium concentration sensed in fluid surrounding distal convoluted tubule
- if either redcued, renin is released
- main function is to regulate blood ressure and the filtration rate of the glomerulus
What is diastolic dysfunction?
- heart dosen’t fill proeprly therefore dosen’t eject properly due to the frank-starling mechanism
- known as heart failure with preserved ejection fraction (HFPEF)
- stiffened ventricle that dosen’t fill properly
What is left ventricular systolic dysfunction?
- heart failure with reduced ejection fraction (HFREF)
- damaged ventricle that can’t pump properly
Whats the relationship between years and mortality for reduced and preserved ejection fraction?
No treatment for patients wit HFPEF but not HFREF
What are 3 symptoms of heart failure?
- oedema
- breathlessness (dyspnoea) e.g during exercise, lying flat (orthopnoea), during night (paroxysmal nocturnal dyspnoea)
- fatigue
How do these “left sided” symptoms of heart failure occur?
- back pressure in LV causes raised pressure in pulmonary circulation
- increased hydrostatic pressure forces fluid outside vascular compartment
- interstitial space in lungs fills with fluid
- oxygen sats drop
What are “right sided” symptoms (when they effect the right ventricle) and how do they occur?
- back pressure transmits to venae cavae
- internal jugular venous pressure rises
- jugular venous pressure raised
- gravity and raised orthostatic pressures force fluid from vascular compartment to peripheral tissue
- ankles swell
- hepatomegaly (swelling of liver)
What are the causes of heart failure?
- Heart attack
- Atrial fibrillation
- Hypertension
- Myocarditis - viruses
- Alcohol (EDOH)
- Genetic factors
If soeone has a heart attack, how can you stop heart failure?
Insert balloon and stent before myocardium dies to open blood vessels - within 2 hours
Where on the heart would anterolateral infarction and posteroinferior infarction occur?
What happens when ejection fraction drops?
- Reduced CO
- Reduced systolic BP
- Reduced aterial stretch
- Reduced renal perfusion
What happens when HR goes too high?
- end of Frank-sterling curve and bowditch effect
- LV stretch eventually exceeds physiological levels - decompensation
- move to the descending limb of the sarcomere tension curve
- small rises in LVEDP (fluid retention) causes large drops in sarcomere tension e.g contractility and SV
- reduces CO, impact on RAAS and ANS
What is adverse remodelling?
- thinning and stretching and LV cavity size increases
- aneurysmal left ventricle because of scar
- rare nowadays
- opposite of Laplace’s law
How do we calculate LVEF% and when do we calculate it?
LVEF%= stroke volume / end diastolic volume
this is a key value calculated on an echo
How do we treat a patient with heart failure?
- giving oxygen
- optimise alveolar ventilation
- may need to increase pressure in airways to oxygenate blood
- non-invasive or invasive ventilation
- relax pulmonary vessels to reduce preload and take strain off LV
- gve morphinr to help breathing and pain
- furosemide (diuretic) to get rid of fluid in chest
What do diuretics do?
they limit reabsorption of fluid
- offloads the ventricles
- moves back along starling curve
- can maximise LV contractility
What are the side effects of diuretics?
- renal dysfunction
- reduces Na, K, Mg
- can induce diabetes (thiazides)
Which drugs are available for prognostic development for heart failure? (make them live longer and better lives)
-ACEi and A2RBs e.g ramipril, candesartan - prevents overactive RAAS
What do ACEi drugs do?
Block conversion of AgI to AGII
- reduces effect of AgI on vasculature
- diminishes release of aldosterone
- can cause bradykinin accumulation - cough
