Unit
- Blood pressure regulation: The cardiovascular system maintains perfusion through cardiac output and systemic vascular resistance. Hypertension develops when these mechanisms become dysregulated, often due to increased sympathetic activity or renal sodium handling.
- Primary vs secondary hypertension: Essential (primary) hypertension accounts for 90-95% of cases and has no single identifiable cause, while secondary hypertension results from underlying conditions such as renal artery stenosis or endocrine disorders.
- Systolic and diastolic components: Systolic pressure reflects arterial pressure during heart contraction, while diastolic represents pressure between beats. Isolated systolic hypertension is common in older adults due to arterial stiffening.
- Classification stages: The American Heart Association categorizes blood pressure into normal, elevated, stage 1, and stage 2 hypertension based on consistent readings. Stage 1 is 130-139/80-89 mmHg; stage 2 is 140+/90+ mmHg.
- Organ damage mechanisms: Persistent high pressure damages endothelial lining, leading to atherosclerosis, left ventricular hypertrophy, and microvascular changes in kidneys and brain.
- Public health impact: Hypertension affects nearly half of U.S. adults and is a leading contributor to heart disease, stroke, and kidney failure. Awareness and control rates remain suboptimal.
- Risk factors: Modifiable factors include diet high in sodium, physical inactivity, obesity, and excessive alcohol. Non-modifiable factors include age, family history, and race (higher prevalence in African Americans).
- Hormonal influences: The renin-angiotensin-aldosterone system (RAAS) plays a central role in blood pressure regulation. Overactivity of this system contributes to vasoconstriction and fluid retention.
- Measurement techniques: Accurate blood pressure measurement requires proper technique including appropriate cuff size, patient positioning with back supported and feet flat on the floor, and averaging at least two readings taken one minute apart. Ambulatory monitoring over 24 hours identifies white coat hypertension and nocturnal dipping patterns that influence risk stratification and therapy adjustments.
- White coat and masked hypertension: Some patients have persistently elevated office readings but normal out-of-office pressures, known as white coat hypertension, which may require less aggressive treatment. Conversely, masked hypertension shows normal clinic pressures but elevated ambulatory readings and carries cardiovascular risk similar to sustained hypertension, necessitating confirmatory testing.
- Resistant hypertension: Defined as blood pressure remaining above goal despite concurrent use of three antihypertensive agents from different classes including a diuretic at optimal doses. Common causes include medication nonadherence, secondary hypertension from renal artery stenosis or primary aldosteronism, volume overload from high sodium intake, and interfering substances such as NSAIDs or stimulants.
- Lifestyle modifications: The DASH diet rich in fruits, vegetables, and low-fat dairy can reduce systolic blood pressure by up to 11 mmHg. Additional evidence supports reducing dietary sodium to under 1500 mg daily, engaging in 150 minutes per week of moderate aerobic activity, limiting alcohol to no more than two drinks daily for men and one for women, and maintaining a healthy body weight.
- Pharmacologic therapy: First-line antihypertensive agents include thiazide diuretics, angiotensin-converting enzyme inhibitors, angiotensin receptor blockers, and calcium channel blockers. Treatment selection is guided by patient comorbidities such as diabetes, heart failure, or chronic kidney disease. Many patients, especially those with stage 2 hypertension or evidence of target organ damage such as proteinuria or left ventricular hypertrophy, require combination therapy to achieve blood pressure goals.
Terminology
- Hypertension
- Persistently elevated arterial blood pressure above normal thresholds.
- Essential hypertension
- Hypertension without an identifiable secondary cause, accounting for the majority of cases.
- Secondary hypertension
- Hypertension resulting from another medical condition such as kidney disease or endocrine tumors.
Quick Revision
- Hypertension results from dysregulation of cardiac output and vascular resistance.
- Primary hypertension has no single cause; secondary hypertension has an identifiable underlying condition.
- Classification stages guide treatment decisions based on systolic and diastolic values.
- Chronic hypertension causes end-organ damage through vascular and structural changes.
- Modifiable risk factors are key targets for prevention and management.