Hypertension Flashcards
What is the frequency of SA node depolarization?
70 times per minute (it is the pacemaker of the heart and sets its contraction rate)
What is sick sinus?
It is characterized by a low heart rate due to lower SA depolarization rate. These patients will usually have pacemakers (“artificial pacemakers”)
What is the AV node and what is its function?
The AV node is located between the atria and it is the gateway for electrical impulse into ventricles
The AV node effectively delays ventricular contraction (allowing the ventricles to fill with blood before contraction)
What happens if AV node depolarization rate is reduced?
Some drugs can delay the SA node’s signals for ventricle contraction. This allows for the ventricles to fill with blood before contraction
Before conduction, what is the polarization of the heart muscle cells?
80-90 mV negative compared to outside the cells.
Ion pumps work to maintain this resting membrane potential (pump out cations(+) and bring in more anions(-))
What is the flow of Na+ before contraction (closed channel gates)?
Due to the negative cell interior, Na+ is magnetically attracted to the surface of the polarized cells
How does the muscle cell loose its polarization?
K+ loss diminishes negative charge (gradual depolarization)
An abrupt increase in Na+ permeability will occur when a certain threshold potential is reached (rapid depolarization)
What types of channels are responsible for Na+ channels in muscle cells?
Voltage-gated
What occurs in Phase 0 of contraction?
Increase in muscle cell permeability to Na+
Ca2+ channels open at around -60mV
This effectively reduces depolarization, which in turn causes muscle contraction
What occurs in muscle cells during Phase 1 of contraction?
Brief re-polarization (cells gets a bit more negative) due to K+ loss
What occurs in muscle cells during Phase 2 of contraction?
At this point, contractions cannot occur despite neuronal impulses
Ca+ continues to enter the cell (started in phase 0)
Ca2+ enters the cell via L type calcium channels (Ca2+ movement initiates muscle contraction)
What occurs in muscle cells in Phase 3 during contraction?
Membrane remains permeable
Na+ and K+ ejected to repolarize (get back to 80-90mV)
What occurs in muscle cells during Phase 4 of muscle contraction?
Na+ is cleared from the cell and K+ loss slows
Eventually, an abrupt increase in Na+ permeability will occur when a certain “threshold potential” is reached
Phase 4 preps the cell for Phase 1, this cycle between all 4 phases allows for heart muscle contraction
What ion is the most responsible for muscle contraction?
Calcium entry causes muscle contraction
More Ca2+ =stronger contraction (contractility)
Faster Ca2+ =faster contraction (chronotropy)
What is an ECG?
Graph of electrical activity in heart
Detected by electrodes(leads) attached to the patient (6-12 leads are often used)
Where are the leads generally placed?
6 limb leads
6 precordial leads
What is the P-wave on an ECG reading?
It represents the depolarization of atria (atrial contraction)
Normal duration = 0.12s
What does the Q-T interval on an ECG reading?
It represents depolarization of ventricles (ventricular contraction)
Normal duration is less than 0.12s
Should the Q-T interval be narrow or wide in normal functioning hearts?
Narrow, if it is wide then an aberrant heat rate can develop independent of the heart (arrythmia can occur)
What does the T-wave on an ECG reading?
It represents the repolarization of ventricles (relax)
What are the different BP measurement methods?
Office (attended, OBPM)
Office Automated (unattended, AOBP)
Ambulatory BP monitoring (ABPM)
Home blood pressure monitoring (HBPM)
Pharmacy blood pressure machines
Should readings from pharmacy BP machines be used to make treatment decisions?
It is highly unlikely they can be relied upoon for determineing risk or deciding about treatment (lack the precision and accuracy)
What are some qualities of home BP monitors?
Considered highly accurate
Highly correlated with usual resting BP levels
Whn should BP be measured at home?
Conditions:
Resting, low stimulation/stimulants/irritants
Duplicate measures
Timing:
Before doses of antihypertensives (will show BP that has the lowest effect by drugs)
Morning and night
Duration:
One week blocks during times of interest (after dose changes, drug changes, taking other drugs)
Do not have to measure everyday for extended periods
Are wrist BP monitors used to make therapeutic changes?
No, unless patients have large arm circumference that cannot fit in brachial BP monitor cuffs
How many Canadians have hypertension?
23%
4 million prescriptions every month in Canada
What are some causes of hypertension?
Fluid and electrolyte balance
Sympathetic nervous system/baroreceptor function (Increased SNS activity)
Metabolic syndrome (diabetes, high cholesterol)
Vascular endothilial function (Prostacyclin and NO production)
What is the effect of a single antihypertensive drug on BP?
These regimen often have limited success in control (-10/-5)
What is treatment-resistant hypertension?
a lack of BP control despite a combination of 3 antihypertensive medications, one of which being a diuretic
How do risk factors impact incidence of heart attacks?
90-100% of heart attacks happen in patients that have have at least one of the following:
Hypertension, dyslipidemia, diabetes, and smoking
Are most CV risk factors very obvious when patients have them?
No, most are silent (makes early screening difficult)
What is the benefit of early detection in hypertension?
It can control risk factors before it develops into full-blown hypertension
At what stage can one manage risk factors that can best help reduce the risk for the development of hypertension?
Changes in earlier life stages have the biggest impact
What are some modifiable risk factors fo developing hypertension?
Obesity
Poor dietary habits
High sodium intake
Sedentary lifestyle
High alcohol consumption
High-normal blood pressure
Diabetes or metabolic syndrome
Smoking
What are some non-modifiable risk factors for developing hypertension?
Over 55 years old
Male
Family history of premature cardiovascular disease
What are the goals of therapy for hypertension?
Reduce/prevent myocardial cell dysfunction
Reduce/stabilize atherosclerosis burden and endothelial cell dysfunction
Reduce/prevent weakened vessel walls
Can one be diagnosed with hypertension after a single high blood pressure reading?
No, it is a trend
What does class mean in recommendations for hypertension therapy?
It suggests the strength of reccomendations
What does level mean in recommendations for hypertension therapy?
It suggests the amount and quality of evidence in support of the reccomendation
Can hypertension be diagnosed in a pharmacy?
No
At what BP does a patient get immediately diagnosed for hypertension without any other assessments?
BP>180/110
What is white-coat hypertension?
BP reading taken in a clinic may be higher than resting due to anxiety
What is masked hypertension?
BP reading taken at clinic are lower than normal resting.
What is metabolic syndrome?
Hypertension is often accompanied by metabolic syndrome.
They are a combination of risk factors and include at least three of the following:
Insulin resistance
Low HDL
Abdominal obesity
High triglycerides
High BP
What types of organ damage do people with long-standing hypertension develop?
Cerebrovascular disease
Hypertensive retinopathy (retinal hemorrhaging)
LVD and LVH
Coronary artery disease
CKD
Peripheral artery disease
Is target organ damage reversible?
No