Hypertension and Blood Pressure Overview

Study Notes

Persistent elevation in blood pressure is called hypertension. It is the most common cardiovascular disease in the world.

Blood pressure is the force of blood pushing against the walls of blood vessels.
Blood pressure is measured in millimeters of mercury (mmHg).
It is expressed as two numbers: systolic (top number) and diastolic (bottom number).

Measures the pressure in the arteries when the heart rests between beats (relaxes).

Cardiac output: The amount of blood the heart pumps out per minute. It is determined by the heart's stroke volume (amount of blood pumped with each beat) and heart rate.
Total Peripheral Resistance: Opposition to blood flow in the arteries, determined by systemic vascular resistance and blood vessel resistance.

Normal: Systolic less than 120 mmHg and Diastolic less than 80 mmHg.
Elevated (Prehypertension): Systolic 120 to 129 mmHg and Diastolic less than 80 mmHg.
Stage 1: Systolic 130 to 139 mmHg or Diastolic 80 to 89 mmHg.
Stage 2: Systolic 140 mmHg or higher or Diastolic 90 mmHg or higher.
Hypertensive Crisis: Systolic higher than 180 mmHg or Diastolic higher than 120 mmHg.

Sympathetic Nervous System: Increases blood pressure by:
- Direct stimulation of blood vessels, causing vasoconstriction.
- Indirect effects on the heart (increasing heart rate) and kidneys (releasing renin).
- Stimulation of adipose tissue to release angiotensinogen.
Renin-Angiotensin-Aldosterone System: A complex hormonal system that regulates blood pressure.
- Renin is released from the kidneys.
- Angiotensin II, produced from renin, is a potent vasoconstrictor and triggers the release of aldosterone.
- Aldosterone increases sodium reabsorption and water retention in the kidneys, leading to increased blood volume and blood pressure.
Other Factors:
- Antidiuretic Hormone (ADH): Released from the posterior pituitary gland, ADH decreases urine volume and increases blood pressure.
- Nitric Oxide: A gas that dilates blood vessels and decreases blood pressure.
- Smooth Muscle Activation: Reduces vessel diameter and increases blood pressure.

Labile Hypertension: Blood pressure fluctuates between normal and high readings.
White Coat Hypertension: Blood pressure is high only at the doctor's office.
Masked Hypertension: Blood pressure is high during daily life, but normal at the doctor's office.
Malignant Hypertension: A severely high blood pressure (160/110 mmHg or higher) that can rapidly damage organs.

Early stages: Left ventricular hypertrophy, increased force of contraction, and increased heart rate.
Later stages: Increased left ventricular wall thickness, decreased stroke volume, and decreased cardiac output.
Advanced stages: Atrial contraction, atrial fibrillation, pulmonary congestion, and heart failure.

Main goal is to reduce blood pressure to below 140/90 mmHg, ideally below 125/75 mmHg.
Lifestyle modifications: Weight reduction, physical activity, stress management, dietary changes (low sodium, DASH diet).
Pharmacological Therapy:
- Diuretics: Reduce blood volume by increasing urine output.
- Beta-blockers: Reduce heart rate.
- Calcium Channel Blockers: Dilate blood vessels by blocking calcium influx.
- Alpha Blockers: Dilate blood vessels by blocking alpha-adrenergic receptors.
- Angiotensin Converting Enzyme Inhibitors (ACE Inhibitors): Block the conversion of angiotensin I to angiotensin II, leading to vasodilation.
- Angiotensin Receptor Blockers (ARBs): Block the action of angiotensin II at receptor sites.

Benefits of exercise:
- Increase sodium elimination, reduce fluid volume, and lower blood pressure.
- Decreases cardiac output, total peripheral resistance, heart rate, and blood pressure at rest and during exercise.
Physical therapists can provide guidance on exercise prescription and lifestyle modifications.