7 - Pathophysiology of Hypertension Flashcards
Define hypertension
A condition of chronically elevated blood pressure
How do you diagnose hypertension?
Hypertension can be only be diagnosed based on 2 or more recordings taken in the seated position at 2 or more office visits
What is the range of blood pressure to diagnose hypertension
Systolic = >140 mmHg Diastolic = >90 mmHg
Describe white coat hypertension
“White coat hypertension” is a relatively recently defined phenomenon of high blood pressure only in the clinical setting; despite the episodic nature of this elevation in blood pressure, these patients are also at a higher risk for some of the cardiovascular-related events seen in overtly hypertensive patients
What is one of the main concerns in the treatment of hypertension?
The number of patients not achieving blood pressure control despite being treated
What comorbidities are often seen in patients with hypertension?
- Ischemic heart disease
- Heart failure
- Atrial fibrillation
- Stroke
The pathogenesis of these conditions overlaps with hypertension and can create a vicious cycle, as hypertension increases the risk of these conditions and these conditions increase the risk of hypertension
Describe the relationship between increased blood pressure and the risk for MI, stroke and HF
The risk for MI, stroke, and HF doubles with a 20 mmHg increase in systolic or 10 mmHg increase in diastolic pressure
What is an uncontrollable risk factor for hypertension?
Aging
There is a 90% lifetime risk of developing hypertension in normotensive middle-aged individuals
Describe the general trend of systolic and diastolic pressure before and after the age of 50
Systolic and diastolic blood pressure increase together until about age 50, then diastolic pressure decreases while systolic pressure continues the upward trend
This means that older individuals are more likely to have isolated systolic hypertension than systolic and diastolic hypertension and younger individuals are more likely to have isolated diastolic hypertension
How does aging contribute to hypertension?
The aging process impairs cardiac function, reducing diastolic pressure, and alters vascular function, increasing systolic pressure
What is a controllable risk factor for hypertension?
Obesity
As BMI increases, the prevalence of hypertension also increases
What factors underlie the pathogenesis of obesity-related hypertension?
Many factors have been proposed to underlie the pathogenesis of obesity-related hypertension…
- enhanced sympathetic activity/ responsiveness
- activation of the renin-angiotensin-aldosterone system (RAAS)
- metabolic disturbances
These factors ultimately change vascular and renal function to increase blood pressure
Describe the organ damage that hypertension can lead to
Hypertension initiates damage to organs, including vasculopathy, cerebrovascular damage, heart disease, and nephropathy
In addition, secondary processes are activated to exacerbate damage
Describe cardiac remodeling which can result from chronically elevated blood pressure
- Ventricular hypertrophy occurs as the heart responds to the high afterload
- Hypertrophy increases the risk of cardiovascular incidents including MI, HF and sudden cardiac death from a fatal arrhythmia or embolism
- Treating hypertension can decrease risks
Where else can remodeling occur due to hypertension?
In he vasculature
What is atherosclerosis?
Vascular remodeling and plaque formation
What two factors can induce remodeling in the vasculature?
- Sheer stress on the vessels
- Hormonal factors such as Angiotensin II
How does Angiotensin II mediate vascular remodeling?
Angiotensin II mediates vascular remodeling through activation of intracellular signaling cascades to alter vascular tone directly and gene expression
What is another process involved in the pathogenesis of hypertension?
Inflammation
How is inflammation activated by hypertension?
Hypertension can activate a T cell-mediated response and further exacerbate end-organ damage
How does inflammation contribute to organ damage?
Inflammation alters the oxidative capacity in the immune cells and reactive oxygen stress can influence vascular tone and protein expression
What does RAAS contribute to hypertension?
The renin-angiotensin-aldosterone system (RAAS) also contributes to immune activation in hypertension.
What are the two components of regulating short-term blood pressure?
1 - neural reflex arcs
2 - total peripheral resistance
What is the purpose of neural reflex arcs?
To modulate heart rate
What are the two major neural reflex arcs?
- baroreflexes
- chemoreflexes
Where do baroreceptors exist? What do they detect?
- Carotid sinus
- Atria
- Pulmonary arteries
Baroreceptors detect blood pressure throughout the vascular tree
Where do baroreceptors send their signals regarding current blood pressure?
Into the CNS (medulla of brain)
What is the purpose of sending this information to the CNS?
Modulation of sympathetic and parasympathetic outflow
What can sympathetics and parasympathetics do with the information they receive regarding blood pressure?
Project to areas of the periphery including the heart and vasculature in order to modulate heart rate and total peripheral resistance
What are the key steps and components of a reflex arc?
- Stimulus to be detected by a sensory receptor (“detector”)
- Sensory info is transmitted to an integration center
- Integration center compares afferent information from several sites to determine the appropriate effector response
- Effector response serves to modulate the initial stimulus, changing the activity of the sensory receptor (“detector”)
How does the reflex arc and feedback loop work for the arterial baroreflex?
Activation of the reflex results in a reduction of the sensed stimulus, meaning that an increase in BP will cause a decrease in BP and vise versa
What type of receptors are baroreceptors? What are they activated by?
baroreceptors are mechanosensitive sensory receptors, activated by the distending pressure in the carotid or atria (stretch receptors)
Increased stretch of the wall generates an action potential in the nerve ending