Clinical Cardiovascular physiology Flashcards
4 clinical conditions that can result from ABP control being disrupted
Hypertension, Cardiac failure, Cardiac arrhythmia and circulatory shock
what is hypertension?
ABP > 140/90 mmHg in humans.
why is hypertension bad?
overwork of the heart, damage to blood vessels.
[leading to cardiac failure, cardiac arrhythmia and ischaemic damage (restriction of blood supply and therefore oxygen) to organs e.g. stroke]
what physiological features does hypertension result from?
raised TPR and/or raised MSFP (failure of homeostasis).[treatment focuses on restoring to normal values]
what is the cause of 90% of hypertension and what is it associated with?
‘essential hypertension’, no clearly defined cause.
Linked to genetic factors and age.
what is the ~10% of hypertension with clear cause defined as?
secondary hypertension.
what is the most common cause of secondary hypertension?
kidney disease. (kidneys important for hormonal control of circulatory volume through controlling angiotensin II levels.)
what can also cause secondary hypertension (but not main cause)
excess adrenaline from pheochromocytoma tumour (activating sympathetic receptors)
what can be used to reduce MSFP to treat secondary hypertension?
reducing circulatory volume (with diuretics) and hormone antagonists blocking renal signalling
example of hormone antagonists that block renal signalling
ACE Inhibitors
what can be used to reduce TPR as treatment for secondary hypertension?
drugs causing arteriolar vasodilatation e.g. Ca2+ channel blockers such as nifedipine
what lifestyle changes can also help treat hypertension ?
exercise; lowers mean resting blood pressure. (even through raises ABP during the exercise)
why is it important to treat secondary hypertension ?
reduces risk of; stroke, heart disease, heart failure, dementia and death
why is it important to make sure patients with hypertension understand why they are being treated?
can be asymptomatic, drugs can cause side effects that make them feel less well. (even tho preventing fatal harm) [also hypotension is symptomatic]
what is it pessary to ensure when doing a trial for new hypertension treatment?
study design does not influence stress levels of participants as this can affect ABP
what is atherosclerosis ?
build up of inflammatory lipid deposits beneath endothelium of blood vessels. Progress to form fibrous and calcific layers
why does atherosclerosis cause problems?
- Narrows blood vessels and resistrics flow
- endothelial damage which promotes clotting (thrombosis, local and distant)
- weakening blood vessel walls, leading to aneurysm.
how is hypertension linked to atherosclerosis ?
hypertension accelerates the development of atherosclerosis by damage to endothelium (other risk factors; obesity, diabetes and smoking)
circulatory effects of hypertension
increase risk of atherosclerosis and abnormal blood vessels might rupture under pressure.
what are coronary arteries?
arteries that supply the HEART with blood
cardiac effects of hypertension
atherosclerosis affects coronary arteries, which can result in cardiac ischaemia (patient feels pain)
what des ischaemia literally mean?
stopping blood. (leads to inadequate oxygen supply)
why is cardiac ischaemia a particular problem in hypertension?
heart has to pump blood into arteries, raised arterial pressure increases work demand for heart
what is hypertrophy?
enlargement of cells and increase in mass
difference between eccentric hypertrophy and concentric hypertrophy in the heart (eccentric and concentric)
eccentric; due to exercise, ventricular volume INCREASES along with the muscle mass.
concentric; muscle expands inwards, DECREASES ventricular volume.
3 major problems due to concentric hypertrophy
- increased myocardial oxygen demand
- Diastolic dysfunction, cardiac filling and stroke volume is impaired
- increased risk of cardiac arrhythmias
what can concentric hypertrophy lead to?
ventricular dilatation - heart can’t empty fully (systolic dysfunction)
diastolic vs systolic dysfunction
diastolic - less compliant to filling
systolic - less contractile
what does diastolic and systolic dysfunction produce?
cardiac failure
what is cardiac failure?
cardiac output that is inadequate for the body’s needs.
CO insufficient to maintain body target arterial blood pressure
how do normal responses to low ABP fair if it is due to heart failure?
Make it worse, responses make heart work harder and can lead to oedema
what do Pharmacological treatments aim to do for low ABP cause by HEART FAILURE
block natural responses low ABP.
what is a myocardial infarction?
heart attack, occurs when blood flow decreases or stops to a part of the heart, causing damage to the heart muscle.
what does cardiac arrhythmia represent?
disorder in cardiac rhythm and/or failed co ordination of individual myocytes within each chamber.
what can be the cause of cardiac arrhythmia?
hypertension, lead to heart failure and produce disordered conduction pathways. (also infarction and ischema)
what is the most common cardiac arrhythmia?
atrial fibrillation
how does atrial fibrillation arise?
irregular heart beat, pacemaker function is lost
how does atrial fibrillation affect cardiac output?
reduces it by impairing ventricular filling
what is the most common terminal event in heart failure and following myocardial infarction?
VENTRICULAR arrthymias.
what is (circulatory)shock ?
if cardiac output is insufficent to supply metabolic substrates for aerobic respiration to all tissues, life-threatening medical emergency
different types of (circulatory) shock
- hypovolaemic shock (loss of circulating volume)
- cardiogenic shock (cardiac pathology)
- distributive shock (fall in vascular tone and leaking of plasma, similar to hypovolaemic)
what can distributive shock be caused by?
septicaemia or anaphylaxis due to failure of sympathetic intervention.
typical signs of shock
hypotension, tachycardia, reduced organ perfusion such as low urine output and loss of consciousness
