Hypertension Overview

Hypertension

• Two types of hypertension:
  • Essential hypertension (primary): 90% of cases, typically caused by aging, smoking, diabetes, stress, and obesity.
  • Secondary hypertension: Less common (approximately 10% of cases), often refractory to three or more antihypertensive medications.
• Essential hypertension causes:
  • Thickened blood vessel walls:
    • Age, smoking, diabetes, stress, and obesity contribute to thickening, reducing vessel diameter and increasing systemic vascular resistance, thus increasing blood pressure.
  • Vasoconstriction:
    • Increased sympathetic tone or stress causes vasoconstriction which reduces vessel diameter and raises blood pressure.
  • High sodium diet:
    • Leads to sodium and water retention, increasing preload, stroke volume, cardiac output, and blood pressure.
• Essential hypertension generally presents in individuals aged 25 to 55 years old.
• Secondary hypertension causes:
  • Renal (most common cause):
    • Chronic kidney disease (CKD)
    • Renal artery stenosis
    • These conditions increase renin-angiotensin-aldosterone system (RAAS) activity, causing sodium and water retention, vasoconstriction, and elevated blood pressure.
  • Endocrine:
    • Thyroid disorders:
      • Hyperthyroidism (high T3 and T4): Increases cardiac output, leading to systolic hypertension.
      • Hypothyroidism (low T3 and T4): Causes vasoconstriction, leading to diastolic hypertension.
    • Adrenal gland disorders:
      • Hyperaldosteronism (high aldosterone): Increases sodium and water retention.
      • Cushing syndrome/disease (high cortisol): Increases sympathetic activity.
      • Pheochromocytoma (high epinephrine and norepinephrine): Increases sympathetic activity.
    • All these endocrine disorders elevate blood pressure.
  • Neurological:
    • Increased intracranial pressure:
      • Caused by bleeds, edema, tumors, or increased cerebral spinal fluid.
      • Leads to Cushing's Triad: Bradycardia, hypertension, and irregular respirations.
  • Aortic:
    • Coarctation of the aorta:
      • Narrowing of the aorta often after the left subclavian artery causing high upper extremity blood pressure and low lower extremity blood pressure.
  • Preeclampsia/Eclampsia:
    • Pregnancy-related condition with proteinuria, edema, and hypertension.
    • Placental vasoconstriction caused by the release of vasoactive chemicals elevates maternal blood pressure.
    • Eclampsia is preeclampsia with seizures.
  • Substances:
    • Sympathomimetic drugs:
      • Cocaine, amphetamines, PCP.
      • Increase sympathetic nervous system activity, leading to elevated blood pressure.
  • Sleep apnea:
    • Causes periodic low oxygen levels during sleep, activating the sympathetic nervous system, leading to vasoconstriction and hypertension.
• Hypertension blood pressure classification:
  • Normal: Systolic < 120 mm Hg and Diastolic < 80 mm Hg
  • Prehypertension: Systolic 120-139 mm Hg or Diastolic 80-89 mm Hg
  • Stage 1 hypertension: Systolic 130-139 mm Hg or Diastolic 80-89 mm Hg
  • Stage 2 hypertension: Systolic >140 mm Hg or Diastolic >90 mm Hg

High Blood Pressure

• Blood pressure readings of at least 140/90 mmHg for two or more readings are considered hypertension.
• Blood pressure readings greater than 180/120 mmHg are considered hypertensive crisis.

Hypertensive Urgency vs. Emergency

• Hypertensive urgency: High blood pressure but no target organ damage.
• Hypertensive emergency: High blood pressure with target organ damage.

Target Organ Damage

• Target organ damage in hypertensive emergencies often involves the cardiovascular system, nervous system, kidneys, or retinas.

Cardiovascular Disease

• High blood pressure increases afterload, forcing the left ventricle to work harder, resulting in left ventricular hypertrophy.
• Left ventricular hypertrophy can lead to diastolic heart failure (heart failure with preserved ejection fraction), a frequent cause of heart failure.
• In acute cases, high blood pressure hinders blood outflow from the heart, potentially causing acute pulmonary edema.
• Hypertension triggers atherosclerosis, plaque formation, impacting vessel health and function.
• Atherosclerosis in coronary arteries reduces oxygen supply to the myocardium, causing ischemia, coronary artery disease, or myocardial infarction (MI).
• Atherosclerosis in peripheral arteries causes peripheral artery disease, leading to pain, skin lesions, and tissue ischemia.
• High blood pressure's shearing forces can damage the aorta, resulting in aortic dissection (tear allowing blood flow into a false lumen) or aortic aneurysm (ballooning or weakening).

Neurological Disease

• Atherosclerosis in cerebral vessels causes:
  • Carotid stenosis: Narrowing of carotid arteries, causing transient ischemic attack (TIA) or cerebrovascular accident (stroke).
  • Cerebral ischemia: Reduced brain blood flow, leading to stroke.
  • Cerebral hemorrhage: Rupture of brain vessels, resulting in intracerebral or subarachnoid hemorrhage.

Renal Disease

• High blood pressure increases glomerular filtration rate (GFR) but leads to afferent arteriole thickening (sclerosis), reducing blood flow to glomeruli.
• This causes ischemia, renal injury, acute kidney injury (AKI), or chronic kidney disease (CKD).
• Hematuria (blood in the urine) can signify AKI.

Retinal Disease

• Retinal disease associated with hypertension is hypertensive retinopathy, progressing through four grades, grade four being the most severe.
• Damage includes retinal vessel sclerosis, reducing oxygen supply, retinal hemorrhaging, and edema. Severe cases can lead to papilledema (optic disc swelling).

Diagnostic Approach to Hypertension

• Measure blood pressure in both arms.
• Obtain at least two blood pressure readings, spaced at least two office visits.
• Consider ambulatory blood pressure monitoring to rule out white coat hypertension.
• Assess for target organ damage to differentiate between hypertensive urgency and emergency.

Treatment of Hypertension

• Lifestyle modifications (weight loss, healthy diet, exercise, reduced sodium and alcohol) are crucial for all patients.
• Antihypertensives may be necessary for stage 1 hypertension if cardiovascular disease risk is 10% or higher.
• Common antihypertensives: ACE inhibitors, ARBs, thiazide diuretics, and calcium channel blockers (amlodipine or nifedipine).
• Antihypertensives are also needed for stage 2 hypertension.

Lifestyle Modifications and Antihypertensives

• Start antihypertensive medications immediately if blood pressure remains consistently above 140/90 despite lifestyle changes.
• Use ACE inhibitors, ARBs, thiazides, or calcium channel blockers as first-line agents.
• For African-American patients, calcium channel blockers (amlodipine and felodipine) and thiazides are more effective than ACE inhibitors and ARBs due to lower renin levels.

Antihypertensive Medications Based on Comorbidities

• Myocardial Infarction: Beta-blockers, ACE inhibitors, and ARBs to reduce ventricular remodeling and arrhythmia risk.
• Heart Failure: Beta-blockers, ACE inhibitors, ARBs, and aldosterone antagonists.
• Coronary Artery Disease: Beta-blockers, ACE inhibitors, ARBs, and calcium channel blockers. Add nitrates (isosorbide dinitrate and isosorbide mononitrate) for angina.
• Atrial Fibrillation: Beta-blockers and calcium channel blockers.
• Diabetes and CKD: ACE inhibitors and ARBs to reduce proteinuria and kidney disease progression.
• Pregnancy: Hydralazine, methyldopa, labetalol, and nifedipine are safe and effective for pregnancy-related hypertension.

Specific Considerations for Different Antihypertensives

• Beta-blockers: Avoid in reactive airway disease (COPD, asthma) and acute decompensated heart failure.
• Calcium Channel Blockers: Avoid in acute decompensated heart failure.
• ACE inhibitors and ARBs: Avoid in acute kidney injury or hyperkalemia.
• Aldosterone Antagonists: Avoid in acute kidney injury or hyperkalemia.
• Thiazides: Avoid in gout due to hyperuricemia.

Hypertensive Urgency

• Blood pressure greater than 180/120 mmHg without target organ damage.
• Aim for blood pressure reduction to less than 160/100 mmHg within one to two days with oral medications.
• Avoid rapid blood pressure reduction to prevent ischemia.

Hypertensive Emergency

• Blood pressure greater than 180/120 mmHg with target organ damage (neurological deficits, chest pain, acute heart failure, aortic dissection, aneurysm, or acute kidney injury).
• Reduce mean arterial pressure (MAP) approximately 25% within the first one to two hours with IV agents.
• Target blood pressure of less than 160/100 mmHg within two to six hours.
• Gradually normalize blood pressure over the next one to two days. Rapid blood pressure reduction can worsen organ damage by decreasing perfusion.

IV Antihypertensive Agents

• Titratable: Nicardipine, Esmolol, Nitroprusside.
• IV Bolus: Hydralazine, Labetalol.

Summary

• Early antihypertensive therapy is important for managing high blood pressure.
• Different medications, including ACE inhibitors, ARBs, thiazides, calcium channel blockers, beta-blockers, nitrates, and aldosterone antagonists, are beneficial based on comorbidities.
• Hypertensive urgency and emergency are distinguished, with emergency requiring gradual blood pressure reduction using IV agents. IV antihypertensive agents are outlined.