Hypertension

Perspective

In the United States, people of African descent have higher disease prevalence and poorer BP control. Chronic HTN is appropriately controlled in only 50% of the population.

Definition

According to the JNC7, BP levels

• 120-139/80-89 mm Hg is pre-HTN
  
• 140-159/90-99 mm Hg is stage I HTN
  
• 160/100 mm Hg or higher is stage II HTN
  

Pathophysiology

Contributing factors:

Neurohormonal dysregulation

• SNS, NE
  
• Causes vasoconstriction via peripheral alpha1-adrenergic receptors of vascular smooth muscles. This occurs primarily in small diameter arterioles. Constriction of small diameter as a sum is the primary driver of SVR and thus afterload.
• Beta1-stimulation: increased CO via increasing HR and SV (CO=HRxSV)
• Direct effect on the kidney that promote sodium reabsorption leading to increase circulating blood volume.
• Activation of RAAS ? activation of ANGII ? vasoconstriction
• Vascular modulation
  
• patients with chronic HTN have remodeled vasculature
  
• Large vessels (e.g. aorta and carotid arteries), there is intima-media thickening with minimal luminal narrowing, vs
• small-vessels, remodeling leads to narrower lumen diameter. These changes work to normalize wall stress overall, but there is reduced vasodilatory capacity.
• Sodium intake
  
• The average american has a daily sodium intake of 3500 mg (vs recommended level of 1500 mg).
• RCT show a decrease in 7 mm Hg/1200mg of sodium intake.
• Psychosocial stress
  
• effects via the SNS and hypothalamic pituitary axis
• Obesity
  
• Increased BMI >30 kg/m2 is a known risk factor for HTN
• Obese individuals have high circulating levels of aldosterone and cortisol.
• There is a high association with obesity and DM and OSA, both of which contribute to poor BP control.
• cardiac function
  
• renal function
  

Management

MAP = (CO x SVR) + CVP

• MAP, represents the average arterial pressure during one cardiac cycle
  
• CO, reflects the pumping force of the heart
  
• SVR, reflects vasogenic tone in the arterioles (i.e. afterload)
  
• CVP, represents intravascular volume
  

**All classes of anti-hypertensive medications, with the exception of pure beta-blockers, decrease SVR.

Prognosis

Mortality is known to double with 20/10 mm Hg rise above the idea level of 115/75 mm Hg.