What are the causes of high systolic and low diastolic blood pressure?

High Systolic (170 mmHg) with Low Diastolic (50 mmHg) Blood Pressure: Causes

This blood pressure pattern represents isolated systolic hypertension with a widened pulse pressure (120 mmHg), most commonly caused by age-related arterial stiffening, though secondary causes must be excluded in younger patients or those with rapid onset.

Primary Mechanism: Arterial Stiffness

The combination of high systolic and low diastolic pressure is fundamentally a consequence of decreased arterial elasticity 1, 2:

• Age-related aortic stiffening is the predominant cause, where the aorta loses its ability to distend during systolic ejection 1
• When arteries are stiff, the pressure pulse wave travels faster and reflects back from peripheral resistance sites during systole rather than diastole 1
• This reflected wave augments systolic pressure while simultaneously reducing diastolic pressure, creating the characteristic wide pulse pressure 1, 2
• The widened pulse pressure (systolic minus diastolic) serves as a marker of severe arterial damage and predicts cardiovascular risk better than either component alone 2, 3

Common Underlying Causes

Age-Related Changes

• Progressive arterial stiffening occurs naturally with aging, making isolated systolic hypertension the most common form of hypertension in elderly populations 4, 3
• Systolic pressure increases progressively with age while diastolic pressure tends to fall after age 50-60 years 4

Modifiable Risk Factors (Primary Hypertension Contributors)

• Obesity accounts for up to 78% of hypertension in men and 65% in women 5
• Excessive sodium intake is independently associated with increased blood pressure and stroke risk 5
• Physical inactivity, poor diet, and excess alcohol consumption contribute substantially to hypertension development 5
• Insufficient intake of potassium, calcium, magnesium, protein, fiber, and fish fats are associated with elevated blood pressure 5

Secondary Causes to Exclude

Endocrine disorders 5:

• Primary aldosteronism (presents with hypokalemia, muscle cramps, weakness)
• Pheochromocytoma (causes blood pressure lability, episodic pallor, dizziness)
• Cushing's syndrome (central obesity, facial rounding, easy bruising)
• Hyperthyroidism (weight loss, palpitations, heat intolerance)

Renal disease 5:

• Chronic kidney disease and renal parenchymal disease are common secondary causes

Obstructive sleep apnea 5:

• Presents with snoring and hypersomnolence

Drug-induced hypertension 5:

• NSAIDs, cocaine, amphetamines, corticosteroids, and calcineurin inhibitors can elevate blood pressure

Clinical Significance and Risks

• Widened pulse pressure (>70 mmHg in this case) indicates severe vascular damage and substantially increases cardiovascular risk 2, 3
• The low diastolic pressure (<70 mmHg) creates a treatment dilemma, as it falls below the safety margin recommended by guidelines while the systolic pressure clearly requires treatment 4, 6
• Low diastolic pressure may compromise coronary perfusion, particularly in patients with existing coronary heart disease 4, 1
• The European Society of Cardiology/European Society of Hypertension recommends maintaining diastolic pressure ≥70 mmHg during treatment to prevent tissue hypoperfusion 6

Distinguishing Features

Historical features suggesting primary (essential) hypertension 5:

• Gradual blood pressure increase with slow rate of rise
• Lifestyle factors favoring higher blood pressure (obesity, high sodium intake, physical inactivity)
• Strong family history of hypertension

Historical features suggesting secondary hypertension 5:

• Absence of family history of hypertension
• Sudden onset or rapid progression of hypertension
• Specific symptoms pointing to underlying endocrine or renal causes
• Young age at presentation

Critical Pitfall

The "J-curve" phenomenon: Further lowering diastolic pressure with aggressive antihypertensive therapy may worsen outcomes, especially in patients with coronary heart disease, as coronary perfusion depends on diastolic pressure 4, 1. The 2018 ESC/ESH guidelines recognize diastolic pressure <70 mmHg as a relative contraindication to aggressive treatment, creating a therapeutic challenge when systolic pressure remains severely elevated 6.