What determines the mechanism of diastolic blood pressure?

Mechanisms of Diastolic Blood Pressure

Diastolic blood pressure is primarily determined by peripheral vascular resistance, arterial wall elasticity, and ventricular diastolic function, with peripheral resistance being the most significant determinant.

Physiological Determinants of Diastolic Blood Pressure

Peripheral Vascular Resistance

• Diastolic blood pressure is predominantly regulated by the resistance in peripheral arterioles 1
• When systemic vascular resistance increases, diastolic blood pressure rises 1
• The run-off of blood from conductance vessels during ventricular diastole is regulated by peripheral resistance 2

Arterial Wall Properties

• Arterial elastance (stiffness) significantly impacts diastolic blood pressure 1
• As large arteries become stiffer with age or disease:
  • Pulse wave velocity increases
  • Wave reflections return earlier to the central aorta
  • Diastolic pressure tends to decrease 3
• The elasticity of conductance vessels determines how effectively they can store blood during systole and release it during diastole (Windkessel function) 3

Ventricular-Arterial Interaction

• Diastolic blood pressure is affected by:
  • Cardiac output and stroke volume
  • Heart rate (affects diastolic filling time)
  • Ventricular diastolic function 1, 4
• Diastolic ventricular interaction refers to competition for space within the pericardium when the right ventricle dilates 1

Age-Related Changes in Diastolic Blood Pressure

• Unlike systolic pressure, which increases progressively with age, diastolic pressure often decreases in older adults 5
• This occurs due to:
  • Increased arterial stiffness of large vessels
  • Decreased elasticity of the aorta
  • Altered wave reflections 1
• The resulting widened pulse pressure (systolic minus diastolic) is an emerging independent risk factor 5

Pathophysiological Implications

Hypertension Classification

• Isolated systolic hypertension (elevated systolic with normal diastolic) can be divided into:
  • Normal peripheral resistance type (normal mean blood pressure)
  • High peripheral resistance type (elevated mean blood pressure) 2

Clinical Significance

• Very low diastolic pressure (≤60 mmHg) in elderly patients with cardiovascular disease is associated with increased mortality 6
• An "optimal" diastolic pressure of approximately 70 mmHg has been identified in elderly subjects with isolated systolic hypertension 6
• Low diastolic pressure can compromise coronary perfusion, especially in patients with left ventricular hypertrophy or coronary artery disease 3

Measurement Considerations

• Accurate measurement of diastolic blood pressure corresponds to Korotkoff phase V (disappearance of sounds) 1
• Phase IV (muffling) tends to overestimate true intra-arterial diastolic pressure 1
• Pseudohypertension may occur in elderly patients with very rigid peripheral arteries, leading to artificially elevated readings 1

Clinical Implications

• When evaluating blood pressure, all components (systolic, diastolic, and mean) should be considered together 2
• Diastolic blood pressure is inversely related to cardiovascular mortality in some populations, particularly the elderly 3, 6
• Excessive lowering of diastolic pressure during treatment of isolated systolic hypertension may be harmful, especially in elderly patients with cardiovascular disease 6

Understanding the mechanisms of diastolic blood pressure is essential for appropriate assessment and management of hypertension, particularly in older adults where the balance between adequate systolic control and maintaining sufficient diastolic pressure becomes clinically important.