By the end of this chapter the student will be able to:
Discuss the pathophysiology of hypertension.
Identify and evaluate primary hypertension vs secondary hypertension.
Recognize the major complications of hypertension.
Understand the basis of antihypertensive therapy.
Discuss novel treatments and trials for hypertension.
Hypertension is the elevated blood pressure (BP) in arterial vessels. Two important determinants of blood pressure are cardiac output and total peripheral resistance which will be discussed in detail later in the chapter. Hypertension is one of the most common conditions, especially in the aging population. It is commonly referred to as the silent killer because it remains asymptomatic until it manifests as one of the life-threatening complications, for example, stroke, myocardial infarction, kidney dysfunction, and so on.
The prevalence of hypertension is approximately 30% in the general adult population according to a study by the National Health and Nutrition Examination Survey (NHANES). This prevalence percentage has significantly increased from previous NHANES reports and translates into 65 million people that are affected by hypertension in the United States.
According to the latest NHANES report, prevalence is higher among the older population, women, and non-Hispanic blacks. The incidence of hypertension has been increasing in industrial countries, which can be attributed to a large extent to dietary habits and an increase in obesity. Furthermore, hypertension is an important worldwide public health challenge—in a pooled data review (Kearney et al., 2005), approximately 972 million people have hypertension worldwide, 333 million in developed countries, and 639 million in developing countries. The number of adults with hypertension is expected to increase by 60% to a total of 1.56 billion people by 2025.
Although control of hypertension has improved significantly over the last 2 decades, it is still not adequate. NHANES reports that approximately 72% of hypertensive individuals are being treated for hypertension, and out of those treated patients only 69% have adequate blood pressure control, defined as blood pressure below 140/90.
Pathophysiology of Hypertension
Normally, the mean arterial pressure (MAP) is the product of cardiac output (CO) and total peripheral resistance (TPR).
TPR is determined by the resistance that is present in the small arteries and arterioles. In order to better comprehend the mechanism of increased blood pressure, it is imperative to have a better understanding of the individual factors that determine hypertension.
Cardiac output is defined as the volume of blood pumped from the right or left ventricle in 1 minute; thus, it is the product of the stroke volume and the heart rate. Factors that increase the heart rate or stroke volume result in changes in blood pressure.
The stroke volume is dependent on cardiac contractility and blood volume, which equates with sodium homeostasis. ...