What Is Isolated Systolic Hypertension?

The function of the heart is to pump blood in the body. This pumping occurs in a sequence called the cardiac cycle. A cardiac cycle consists of two phases: a diastolic phase, during which the ventricles (lower chambers of the heart) relax and fill with blood, and a systolic phase, during which the ventricles contract and eject this blood to the rest of the body. The blood pressures in the systolic and diastolic phases represent the highest and lowest circulatory pressures during the cardiac cycle, respectively.

Blood pressure values are obtained by measuring the pressure during the diastolic phase against the systolic phase. Hypertension (high blood pressure) is when the systolic pressure exceeds 139mmHg and the diastolic pressure exceeds 89mmHg. 

Isolated systolic hypertension (ISH) is a condition where the systolic blood pressure (SBP) is elevated while the diastolic blood pressure (DBP) remains within the normal range.

The 2020 International Society of Hypertension (ISH) guidelines define isolated systolic hypertension as “elevated SBP (≥140 mmHg) and low DBP (<90 mmHg) This condition is common in elderly people and in young individuals, including children, adolescents and young adults.¹

The prevalence of isolated systolic hypertension has risen in the past two decades in both the young and elderly population.⁶ In young individuals, it is the most common form of hypertension, and in the elderly, it arises as a result of the stiffening of the large arteries along with the widening of the pulse pressure.¹

The pulse pressure is the difference between the systolic blood pressure and diastolic blood pressure. There is a progressive widening of the pulse pressure beyond age 60, with isolated systolic hypertension being responsible for close to 65% of hypertension cases in elderly patients.⁷

Overview

In the last decade, research in the area of isolated systolic blood pressure has gained more traction due to its impact on coronary heart disease, stroke, heart failure and kidney failure.¹

Evidence from published research such as the Systolic Hypertension in the Elderly Program (SHEP) and the Systolic Hypertension in Europe (Syst‐Eur) trials shows the benefits of lowering blood pressure in patients with isolated systolic hypertension.⁴

Among older individuals, systolic blood pressure and pulse pressure are more powerful predictors of cardiovascular disease than diastolic blood pressure.”³

Causes of isolated systolic hypertension

Just like hypertension, the causes of isolated systolic hypertension can be classified into primary and secondary causes.

• Primary causes include: arteriosclerosis
• Secondary causes include: anaemia, hyperthyroidism, aortic insufficiency, Paget’s disease, beriberi, aortic regurgitation, thyrotoxicosis, hyperkinetic heart syndrome, fever, arteriovenous fistula, patent ductus arteriosus, hypertensive heart disease, renal artery stenosis, certain substances such as nitric oxide, endothelin^3,4

Arteriosclerosis: arterial stiffness (hardening of the arteries) and reduced arterial compliance. Arterial compliance refers to the ability of blood vessels to expand and contract with each heartbeat. When arterial compliance decreases, the arteries become less efficient in absorbing the pressure generated by the heart's contraction, resulting in higher systolic blood pressure.

Hyperthyroidism: This is a common cause of isolated systolic hypertension. In hyperthyroidism, an abundance of the thyroid hormone T3 results in increased heart rate and pulse pressure.⁴

Hypertensive heart disease: Long-standing hypertension can cause changes in the heart's structure and function, leading to hypertensive heart disease. This condition can contribute to ISH by increasing the resistance to blood flow from the heart and elevating the systolic blood pressure.

Renal artery stenosis: Narrowing of the renal arteries, which supply blood to the kidneys, can result in ISH. The kidneys play a vital role in blood pressure regulation, and any impairment to their function can lead to hypertension.

Medications or substances: Some medications, such as nonsteroidal anti-inflammatory drugs (NSAIDs), decongestants, and certain antidepressants, as well as substances like alcohol and stimulants, may contribute to elevated systolic blood pressure through their harmful effects on organs such as the kidneys.

Nitric oxide and endothelin are substances that regulate arterial stiffness. It has been shown that dysfunction of the endothelium (the inner lining of blood vessels) increases arterial stiffness and potentially leads to the development of ISH. This is mediated by nitric oxide and endothelin, both of which are produced by the endothelium.⁸

Signs and symptoms of isolated systolic hypertension

Hypertension is mainly asymptomatic, with specific symptoms signifying secondary hypertension or arising due to complications.¹

Possible symptoms and signs include: 

• Chest pain
• Dyspnea (shortness of breath) 
• Heart palpitations 
• Claudication
• Peripheral oedema
• Headaches
• Blurred vision
• Frequent urination at night (nocturia)
• Blood in urine (hematuria)
• Dizziness

There are also symptoms suggestive of secondary hypertension such as:

• Muscle weakness, muscle cramps, irregular heartbeat, flash pulmonary oedema  suggestive of renal artery stenosis
• Sweating, palpitations, frequent headaches associated with pheochromocytoma  
• Snoring, daytime sleepiness associated with obstructive sleep apnea
• Weight loss, sweating, palpitations, irritability symptoms suggestive of thyroid disease

Management and treatment for isolated systolic hypertension

Lifestyle modification is advised in pre-hypertensive patients and those at increased risk of developing hypertension.^2,10

These lifestyle modifications include: 

• Daily aerobic exercises
• Low salt diet
• Low-fat and cholesterol diets
• Limiting alcohol intake
• Limiting all forms of smoking
• Adequate stress management
• Weight control for obese individuals
• Avoidance of illicit drug abuse 
• Adequate intake of minerals such as potassium, calcium and magnesium¹⁰

The JNC 7 suggests that all people with hypertension (stages 1 and 2) be treated with the goal of lowering blood pressure values to below 140/90mmHg.²

Lowering of systolic blood pressure may be accompanied by further lowering of diastolic blood pressure. In older patients with isolated systolic hypertension, this has been found to be of no consequence. However, more research is needed to determine the balance of risks and benefits of antihypertensive (blood pressure-lowering) therapy in older patients, particularly those above the age of 80.³

There are four major classes of antihypertensive agents found to be effective in the control of ISH. These include: 

• Thiazide diuretics such as chlorthalidone and indapamide
• Dihydropyridine calcium channel blockers (CCBs) such as amlodipine, nifedipine, nitrendipine
• Angiotensin-converting enzyme inhibitors (ACEi) such as lisinopril, ramipril
• Angiotensin receptor blockers (ARBs) such losartan, telmisartan valsartan¹⁰

Oral nitrates have been shown to reduce pulse pressure and arterial stiffness when taken by patients with isolated systolic hypertension for over 3 months. Improving nitric oxide bioavailability could lead to a reduction in arterial stiffness, and consequently a reduction in cardiovascular risk.⁸

The benefits of drug treatment for ISH among the elderly have been shown, but such evidence does not exist for younger and middle-aged adults.⁶

Diagnosis

Current clinical criteria for diagnosing hypertension are based on the average of two or more seated blood pressure readings during two or more outpatient visits. This diagnosis might be achieved at a single reading if your blood pressure is 180/110 mmHg or higher and there is evidence of cardiovascular disease (CVD).^1,2

Diagnosis of ISH will involve the following steps:

1. History taking – a thorough medical and family history
2. Physical examination – a thorough examination of the heart and circulatory system and other organs/systems such as the kidneys, thyroid etc. ^[1]
3. Laboratory tests – blood tests such as electrolytes, serum creatinine, urea and estimated glomerular filtration rate (eGFR), fasting lipid profile and fasting glucose. A dipstick urine test may be performed¹
4. A 12-lead ECG to check heart rhythm and find any structural abnormalities of the heart
5. Imaging techniques – Chest X-ray, echocardiography, computed tomography (CT) angiography, magnetic resonance (MR) angiography, carotid ultrasound, ultrasound/renal artery duplex, fundoscopy, brain CT/MRI¹
6. Additional investigations – Ankle-brachial index, aldosterone-renin ratio, metanephrines, salivary cortisol, thyroid stimulating hormone, urinary albumin/creatinine ratio, serum uric acid (s-UA) levels, haemoglobin A1c, liver function tests, applanation tonometry^1.9   

Risk factors

ISH becomes more common as people age, mainly because of the increased stiffening and narrowing of arteries that occurs with age. This leads to increased resistance to blood flow and higher systolic blood pressure readings.

People assigned female at birth (AFAB) may be more predisposed to ISH, according to current studies.^1,10 In general, people AFAB have higher central blood pressure, reflecting the pressure experienced by internal organs (e.g., brain, heart, and kidneys), and have shown greater risk for CVD complications.⁶ Isolated systolic hypertension is present in more than 30% of people AFAB over 60 years old.¹

A history of cardiovascular disease (CVD) such as heart attacks, heart failure, stroke, transient ischemic attacks (TIA), diabetes, dyslipidemia (high blood fat), and chronic kidney disease (CKD) can increase your risk of isolated systolic hypertension. 

Other factors can also play a role, such as smoking, poor diet, alcohol intake, physical activity, higher BMI, and psychosocial aspects such as less education and a history of depression.^1,6

A family history of hypertension, premature cardiovascular disease, high cholesterol and diabetes is also a risk factor.¹

Complications

Complications that may arise from isolated systolic hypertension include: 

• Heart attack
• Stroke
• Heart failure
• Peripheral vascular disease (PVD)
• Aneurysm
• Retinopathy
• Chronic kidney disease
• Erectile dysfunction

The greater the number of risk factors in an individual, the higher their chance of cerebrovascular and kidney disease as a complication.¹

The risk of cardiovascular disease is said to double for every 20mmHg increase in systolic blood pressure and every 10mmHg increase in diastolic pressure.³

FAQs

How can I prevent isolated systolic hypertension?

Lifestyle modification can prevent the development of hypertension, and early detection can prevent complications from arising. Whether one has a familial history or not, yearly checkups at the GP should be maintained as this can aid in early detection.

How common is isolated systolic hypertension?

Its prevalence has been steadily rising in both young and elderly populations. More research is needed to ascertain its prevalence on a worldwide scale.

When should I see a doctor?

Should you have any of the associated risk factors mentioned above or a recording of elevated blood pressure, consult your doctor.

Is isolated systolic hypertension hereditary?

While there might be some inherent genetic predisposition, the outcome depends on a combination of modifiable and non-modifiable risk factors, among which ageing is the most predominant factor.

Summary

Isolated systolic hypertension refers to high systolic blood pressure (140mmHg or above) with low diastolic blood pressure (below 90mmHg). It most often causes no symptoms unless it has caused secondary conditions to develop.

Early detection, lifestyle modification and medication can decrease the morbidity and mortality associated with isolated systolic hypertension.