Lecture 23: Hypertension, Heart Failure And Haemodynamic Disorders Flashcards
Give the formula of blood pressure
BP=COxPVR
What is blood pressure determined by?
Cardiac output
Peripheral vascular resistance
What does cardiac output depend on?
Heart rate, heart contractibility and blood volume
Where is peripheral vascular resistance determined?
At the level of arterioles by a combination of neural and hu oral factors
What are humoral factors of peripheral resistance?
Constrictors like
angiotensinII, catecholamines, thromboxane, leukotrienes, endothelin
And dilators like
Prostaglandins, kinins, nitric oxide
What are local factors of peripheral resistance
Autoregulation
Ionic (incl. pH and hypoxia
What are neural factors of peripheral resistance?
Constrictors
Like α-adrenergic
Dilators
Like β- adrenergic
Define hypertension
Abnormally high blood pressure in a vascular bed
What are some examples of hypertension
Systemic arterial hypertension
Pulmonary hypertension
Portal hypertension
What is portal hypertension?
Raised pressure in the hepatic portal vein and tributaries
How does systemic blood pressure vary?
Diurnally,
Posture,
Exercise
Stress
How can blood pressure be measured in spite of being influenced by so many things?
It is taken on at least 3 occasions over a 3-4 week period.
What is diastolic pressure?
intravascular pressure during left ventricular filling
What is systolic pressure?
Intravascular pressure during left ventricle contraction
What constitutes as systemic arterial hypertension?
Diastolic pressure >90mmHg and systolic pressure >140mmHg
How many people are affected by systemic arterial hypertension?
800million
What are the two categories of systemic hypertension?
Secondary hypertension and primary hypertension
What proportion of hypertension patients have secondary hypertension?
5%
What is secondary hypertension likely to be caused by?
As a result of other diseases like renal disease, endocrine disorders, neurological disorders and vascular disease
What is primary hypertension?
Essential hypertension.
Systemic arterial hypertension from no obvious cause.
What proportion of hypertensive patients have primary hypertension?
95%
Why is there a genetic predisposition to essential hypertension?
It is twice as common in black Americans than in whites
There is an increased risk if a relative has hypertension
What are the candidate genes recognised for essential hypertension?
Genes encoding for angiotensin converting enzyme, renin, nitric oxide synthase
Why are the most interesting findings about the gene for angiotensinogen?
Certain polymorphism s of twins gene is inked with elevated circulating levels of angiotensinogen protein which causes blood pressure to rise
Which environmental factors also play an important role?
High dietary sodium, stress, smoking, and inactivity
What does hypertension increase the risk of?
Atherosclerosis and related complications
Left ventricular hypertrophy
Cardiac failure
Cerebral haemorrhage
Aortic dissection (blood dissects along aortic media with risk of occlusion of major branch of vessels and aortic rupture)
Small blood vessel disease
Renal insufficiency and renal failure
What is heart failure?
The failure of the heart to maintain an output of bloo that is adequate for the demands of the bdy
What can heart failure be like?
Either acute or chronic
Can affect left side of the heart, or the right side, or both sides
What happens in low output heart failure?
Failure to maintain normal cardiac output because of a disease affecting the Heart
What is high output heart failure ?
Heart is unable to meet an increased demand for the pumping of blood.
What happens when inadequate cardiac output occurs?
Adaptive mechanisms are initiated which maintain cardiac output at least temporarily w
List the adaptive mechanisms which are activated when cardiac output is inadequate
Hypertrophy
Dilation of cardiac chambers
Increased circulating volume
Increased catecholamine release
What is hypertrophy?
Slow increase in thickness of myocardial fibres
No longer most efficient state to contract efficiently
Why does dilation of cardiac chambers occur?
To increase the mechanical advantage during pumping
Why does increased circulating volume occur as an adaptive mechanism of inadequate cardiac output?
Due to activation of renin angiotensin aldosterone system
What is the role of increased catecholamine release?
Increased Release of catecholamine from the adrenal medulla and sympathetic nervous system results in increased heart rate and myocardial contractility
When will cardiac decompensation occur?
If cause of heart failure is progressive and/or prolonged and adaptation is no longer adequate to maintain cardiac function
The increased circulating volume may produce a volume overload. What can this lead to?
Coronary blood supply unable to cope with increased metabolic demands of hypertrophied and dilated heart muscle
Excessive cardiac dilation may lead to mechanical disadvantage during pumping
What are the end results of heart failu?
Reduced cardiac output with hypoxic effects on other organs
Damming back of blood in veins with congestive effects on multiple organs
What does normal fluid homeostasis include?
Maintenance of vessel wall integrity and maintenance of intravascular pressure and osmolarity
What is the net movement of substances across blood vessel walls determined by?
The balance if pressure and osmolarity within vessels and pressure and osmolarity outside vessels in the interstitial spaces.
What does this balance result in most healthy tissues?
Small net movement of fluid across vessel walls into interstitial spaces.
What are the small net movements of water into interstitial spaces removed by?
Lymphatics and returned to the circulation via the thoracic duct.
What happens if a large net movement of fluid from vessels into interstitial space occurs?
Capacity of lymphatics to remove fluid may be exceeded resulting in tissue oedema
What is oedema?
An increase of fluid within interstitial tissue spaces.
How can oedema develop
In various conditions, it can occur in dependent tissues like ankles, lungs, bran, or
Fluid can accumulate within body cavities (like in the peritoneal cavity as ascites)
What does local oedema occurring during inflammation caused by?
Increased blood flow and local increases in vs urad permeability
The oedema fluid is a protein rich exudate with a specific gravity > 1.02
How is oedema caused by non-inflammatory causes different?
The oedema fluid is a protein poor transudate with a specific gravity of < 1.02
What are the causes of non inflammatory oedema?
Increased intravascular hydrostatic pressure Reduced plasma osmotic pressure (hypoproteinaemia) Lymphatic obstruction (e.g. Neoplasia, post surgical, post-irradiation) Sodium retention (e.g. Renal hypo perfusion, excess salt intake, rennin-angiotensin system increase)
What is hyperaemia?
Active process with increases in flow to a capillary bed as a result of arteriolar dilatation
E.g. In skeletal Muscle during increased exercise
What is congestion?
Passive process with decreased outflow from a capillary bed
What can cause congestion?
Systemic process (like heart failure) Local process e.g. Isolated venous obstruction or oedema
What is haemorrhage?
Extravasation of blood due to vessel rupture
Usually follows vessel injury due to trauma, atherosclerosis, or erosion (by inflammation or neoplasm)
What are haemorrhagic diatheses?
Disorders which increase the likelihood of haemorrhage
Like
Thrombocytopenia - low platelet counts
Clotting factor defects
Amyloidosis - Increased vessel fragility
What is hematoma?
Haemorrhage enclosed within tissues
What are the multiple, small haemorrhages seen in haemorrhagic diatheses ?
Petechiae: 1-2mm
Purapura: >3mm
Ecchymoses: >10mm
What do the clinical symptoms of haemorrhage depend on?
Volume - rapid loss of 20% of blood volume is tolerated well by most healthy adults.
General health
Site of haemorrhage e.g. Brain….
What is shock?
Cardiovascular collapse
Potentially lethal systematic hypoperfusion due to reduction in cardiac output and/or reduction in effective circulating blood volume.
What does shock result in?
Hypotension, impaired tissue perfusion, cellular hypoxia
Irreversible cell injury occurs if shock persists
What are the causes of shock categorised as ?
Cardiogenic - arise from problem related to inadequate cardiac output
Hypovolaemic - arise from problem related to inadequate effective circulating volume
Septic - arising from problem related to infection
What are some clinical examples of cardiogenic cause of shock?
Myocardial infarction, ventricular rupture, arrhythmia, cardiac tamponade, pulmonary embolism
What are the clinical examples of hypovolaemic causes to shock?
Haemorrhage
Fluid loss e.g. Vomiting, diarrhoea, burns, trauma
What are the clinical examples of septic causes of shock?
Overwhelming microbial infections Endotoxin shock Gram-positive septicaemia Fugal sepsis Super antigens
