Cardiovascular Diseases - Hypertension

Question 1

Blood Pressure (120/80)

Answer 1

• Produced by circulating blood upon the wall of the blood vessels
• Usually measured in left upper arm
• Systolic (120) - Pressure during heart contraction - Maximum arterial blood pressure
• Diastolic (80) - Pressure during the relaxation phase while the heart is filling - Longer duration - Considered “more important”

Question 2

Physiology of Blood Pressure

Answer 2

Arterial blood pressure curve
- Blood pumps from heart to blood vessels along pressure gradients
- Highest in aorta, lowest in right atrium

Mean pressure
- Average arterial pressure during a - Determined by cardiac output, vascular resistance, and central venous pressure
- It is perfusion pressure - pressure that the heart needs to sustain to be perfused
Lower than 60 mmHg = ischemia

Question 3

Systolic and Diastolic BP

Answer 3

• Pressure decreases most rapidly when blood passes through small calibre vessels
• Arterioles -> capillaries -> venules -> veins
• Pressure levels off, slows down -> vena cava
• Total area or total cross-section of all vessels of the same diameter is larger for smaller vessels - more of them
• Resistance increases while being pumped through smaller vessels - levels off through larger vessels
  Highest resistance in arterioles

Question 4

BP regulation

Answer 4

• BP = cardiac output x peripheral vascular resistance
• cardiac output depends on heart rate and stroke volume (volume pumped with each contraction) - single contraction per minute (heart rate)
• peripheral resistance controlled by the balance of constricting and dilating humoral and neural factors on blood vessels (epinephrine, a vasoconstrictor) - resistance of blood circulating and resistance of vessels to circulate blood flow
• kidney and BP regulation - kidney releases renin when BP drops, which activates vasoconstrictor angiotensin - it also controls sodium levels, i.e blood volume

Question 5

Hypertension Risk Factors and Incidence

Answer 5

Risk factors
- stroke (increase in systolic pressure)
- coronary heart disease (increased diastolic BP)
- silent killer (asymptomatic for years, symptomatic after the damage done, treatment required indefinitely, do not feel better after damage)

Incidence
- Poor awareness
- Inadequate treatment
- Inadequate control
- 1/4 people hypertensive - middle-aged
- 75 years old - high BP
- 25% of patients are hypertensive, 50% are aware of the diagnosis, 16% will have adequate treatment and control
- Women have higher awareness and adherence to treatment

Question 6

Renin-Angiotensin Feedback Loop

Answer 6

• One of the ways for the body to regulate constant blood pressure
• Reason to cause low blood pressure - bleeding, septic shock

Positive mechanism - kidney
- Jackson-Glomerular complex - volume receptors special apparatus when blood pressure lowers, it stimulates folding receptors -> produce renin
- Renin will act on angiotensin and promote the conversion of angiotensin 1 to angiotensin 2 through the conversion enzymes
- Angiotensin 2 by itself is an important vasoconstrictor and promotes aldosterone synthesis (adrenal glands), leading to sodium retention (blood volume, preload)
Once blood pressure is at acceptable levels ->, feedback to J-G to stop using renin

Preload
- Amount of blood in the blood vessels
- Excessive sodium, retains more water - increasing preload (blood in vessels)
- Overtime patients will be predisposed to systemic hypertension

Question 7

Primary Hypertension

Answer 7

• Essential or idiopathic HTN
• 90% of cases
• Etiology is idiopathic, multifactorial
• Prevalence increases with age, “hardening of arteries”
• Treatment - weight loss, exercise, salt restriction, medications
• BP 140/90 - systolic or diastolic

Question 8

Secondary Hypertension

Answer 8

• HTN has a specific cause (secondary to another medical condition)
• 10% of cases
• Treatment aimed at eliminating the cause and therefore curable HTN

Causes: Renal
- Important role of the kidney in BP regulation - anything involving the kidney can have secondary HTN
- Renal disease often causes secondary HTN - Polycystic kidney disease - Renovascular disease (renal artery stenosis) - Chronic Kidney disease (e.g. diabetes mellitus)

Endocrine diseases:
- elevated hormone levels, which can increase BP via their vascular constricting influence - epinephrine-secreting tumour on the adrenal gland
- hyperthyroidism can cause HTN - overproduction of steroid hormone, causes tachycardia or increased heart rate

“white-coat” HTN
- Patients might get nervous or stressed out when having their BP measured in a medical environment, checked in relaxed setting they are normal

Question 9

Hypertension - Pathological Effects

Answer 9

Disease due to HTN is mostly attributable to its adverse effects on arteries
- Small arteries (arterioles) - causes hyaline arteriolosclerosis - Hardening of arteries - Fatty plaque formation
- Large arteries - cause accelerated atherosclerosis

Coronary artery with severe atherosclerosis
- Clots that are calcified
- Cholesterol clefts

Question 10

Specific End-organ Disease of HTN

Answer 10

Brain
- Small vessel arteriolosclerosis at the brain base
- Two ways it can cause hemorrhage or small ischemic stroke - b/c rupture
- Small vessels within the brain stem and deep brain structures (basal ganglia) - Sustain hypertension can become dilated and can form aneurysms
- Intraparenchymal hemorrhage (hemorrhagic stroke) - Consequence of arteriolosclerosis
- Lacunar stroke - Consequence of arteriolosclerosis - Ischemic change - small - Occlusion vessels -. Ischemic
- Atherosclerosis causing ischemic stroke - Large vessel disease

Hypertensive retinopathy
- Patient that had hypertension for a long time
- See double vessels, hemorrhages, small infarcts

Heart
- Left ventricular hypertrophy as a physiological response to increased work load - Left ventricle should be less than 1.5 cm - adapts by undergoing hypertrophy (muscle mass), and hypertension is the most common cause - can die suddenly from arrhythmia
- Coronary atherosclerosis causing myocardial infarction - Scarring

Kidney
- HTN results in nephrosclerosis - a major cause of renal failure
- Chronic renal failure as a consequence of arteriolosclerosis - Arterial that brings blood to glomerulus, the main functional unit of kidney is getting blocked - Leads to dead and scarred sclerotic tissue - Kidney becomes smaller over time
- Need renal replacement therapy