Hypertension

• The relationship between blood pressure and CVD events is continuous, consistent, and independent of other risk factors.
• The higher the blood pressure, the greater the chance of heart attack, heart failure, stroke, and kidney disease.
• Hypertension prevalence varies with sex and ethnicity and increases with age.

Using data from the National Health and Nutrition Examination Survey (NHANES 2013-2016), the age-adjusted prevalence of hypertension among adults (≥20 years of age) in the United States was 46.0% (49.0% for men and 42.8% for women) [2]. Moreover, according to the National Vital Statistics System, there were 90,098 deaths primarily attributable to high BP in 2017 [2]. Hypertension prevalence varies with ethnicity, sex, and age. In the United States, the highest prevalence of hypertension was found in black men and women. Age-adjusted prevalence of hypertension among non-Hispanic black men was 57.6% and 53.2% among non-Hispanic women [2]. In both sexes, the prevalence of hypertension was reported to increase with age and was higher in men than in women up to 64 years of age [2]. Beyond this age, the prevalence of hypertension was found to be greater in women than in men [2]. Several other interesting statistics on high BP can be found in a report from the American College of Cardiology/American Heart Association Task Force on clinical practice guidelines [1] and a report from the American Heart Association [2].

Hypertension is one of the most important modifiable risk factors for coronary heart disease, stroke, congestive heart failure, renal disease, and peripheral vascular disease. Arterial BP is a product of cardiac output and systemic vascular resistance. A number of factors modulate BP for adequate tissue perfusion, including humoral mediators, vascular reactivity, circulating blood volume, vascular calibre, blood viscosity, cardiac output, blood vessel elasticity, and neural stimulation [3]. Although genetics appears to play a role in essential hypertension, the exact mechanism has not been established. Uncontrolled and prolonged elevation of BP can cause adverse changes to cardiac structure and function in two ways: directly by increased afterload and indirectly by associated neurohormonal and vascular changes. Accordingly, hypertension can damage various organs of the cardiovascular and central nervous system and is a frequent cause of renal disease.

Cardiac involvement in hypertension manifests as left ventricular hypertrophy, left atrial enlargement, aortic root dilatation, atrial and ventricular arrhythmias, systolic and diastolic heart failure, and ischemic heart disease (IHD) [3]. Cerebrovascular manifestations include hemorrhagic and atheroembolic stroke or encephalopathy [3]. Nephrosclerosis and microalbuminuria are also some of the possible complications of long-standing hypertension in the kidney [3].

Data on more than one million individuals has shown that death from both IHD and stroke increases progressively and linearly from BP levels as low as 115/75 mmHg [4]. Beginning at 115/75 mmHg, every 20/10 mmHg increase in BP doubles the rate of mortality from both IHD and stroke [4]. In addition, longitudinal observations from the Framingham Heart Study have shown that BP values from 130/85 to 139/89 mmHg increase CVD risk more than twofold when compared to BP levels below 120/80 mmHg [5]. In addition, systolic BP has been reported to be a more important CVD risk factor than diastolic BP. Indeed, higher systolic BP was associated with increased CVD risk after statistical adjustment for diastolic BP while diastolic BP was not consistently associated with CVD risk once adjustment for systolic BP was performed [1].

In the Framingham study, Wilson et al. [6] followed a cohort of 3,323 middle-aged adults for the onset of CVD, CHD, and type 2 diabetes over an 8-year period. They reported that hypertension and HDL cholesterol contributed most to CVD outcomes. In addition, elevated BP was found to enhance the risk of myocardial infarction (MI) in populations with severe hypercholesterolemia [7,8].

Effect of anti-hypertensive therapy on CVD risk

Adopting a healthy lifestyle is crucial to prevent hypertension. However, anti-hypertensive therapy is recommended when BP is over 140/90 mmHg. Data from clinical trials has shown that anti-hypertensive therapy can have a beneficial effect, reducing stroke incidence by 35-40%, MI by 20-25%, and heart failure by over 50% [9]. In patients with hypertension from 140/90 to 159/99 mmHg and additional cardiovascular risk factors, a 12 mmHg reduction in systolic BP over 10 years will prevent 1 death for every 11 patients treated [10]. For more information on anti-hypertensive therapy, please visit the Managing CMR section.

The worldwide obesity epidemic may have helped raise hypertension rates, as overweight individuals have higher rates of hypertension than normal weight individuals [11,12,13]. A weight loss of just 4.5 kg reduces BP and/or prevents hypertension in a large proportion of overweight individuals [14]. High BP is also a common feature of the metabolic syndrome, which increases the risk of developing CVD and type 2 diabetes. The link between hypertension and CVD may therefore be obesity, especially visceral obesity, which has been tied to various atherogenic and diabetogenic abnormalities [15]. For more information on visceral adipose tissue and hypertension, click here.

Hypertension is taking on greater importance as a medical and public health issue. The relationship between hypertension and CVD risk is well documented. An elevated BP increases the risk of MI, heart failure, stroke, as well as kidney and cerebrovascular diseases. Furthermore, hypertension is typically associated with abnormal cholesterol levels, a greater body mass index, and an increased prevalence of diabetes. Various hypertension management strategies are available to patients with elevated BP, including lifestyle modifications and antihypertensive drugs. However, healthcare professionals must not only identify and treat patients with hypertension, they must also promote a healthy lifestyle and emphasize prevention in order to decrease the prevalence of hypertension in the general population.