Approach to Difficult to Manage Primary Hypertension

Definition of Hypertension

Hypertension is generally defined as persistent blood pressure readings 140/90 mm Hg or higher, more than 50% of the day obtained under proper measuring conditions. Primary hypertension is persistently elevated blood pressure not found secondary to identifiable causes such as CKD defined as an estimated glomerular filtration rate (eGFR) below 60 mL/min/1.73m ² or endocrine diseases.

Primary hypertension can be diagnosed in a variety of settings with different patterns of pressure variability ( Table 30.1 ). White coat hypertension is defined as a blood pressure measured in a physician’s office persistently 140/90 or greater mm Hg, whereas home blood pressure measurements are generally less than 135/85 mm Hg. A stress or alerting reaction may be responsible for the persistently elevated office blood pressure measurements, although a definitive mechanism is unknown. Masked hypertension is the inverse of white coat hypertension. Individuals with masked hypertension have office blood pressure measurements of less than 140/90 mm Hg but home or work settings demonstrate 24-hour ambulatory blood pressure measurements consistently elevated. Masked hypertension may be as high as 10% of the population and is associated with increased CV risk and CKD progression. Isolated systolic hypertension is defined as a systolic blood pressure consistently 140 mm Hg or higher with a diastolic blood pressure below 90 mm Hg. This pattern of hypertension is relatively common in people over the age of 65 years because of loss of larger artery compliance and is associated with increased CV morbidity. Resistant hypertension is defined as elevated blood pressure despite treatment with three appropriate antihypertensive agents at optimal doses with one of the antihypertensive agents being a diuretic appropriate for kidney function. Many patients with resistant hypertension can be successfully treated with an antihypertensive program combining lifestyle and pharmacologic therapy with an understanding of the underlying pathophysiology most likely driving the blood pressure elevation. The following sections will outline diagnostic and treatment strategies for the spectrum of primary hypertensive patients.

How to Diagnose Hypertension

Note that high blood pressure and hypertension are not necessarily the same thing. An increase in blood pressure is a normal physiologic response to exercise and stress. Systemic arterial hypertension is a condition of a persistent nonphysiologic increase in blood pressure. Regulation of blood pressure is complex with interaction between numerous hormonal, neurologic, and local endothelial systems. Imbalance in any of these regulatory systems may be associated with changes in blood pressure. We can consider a blood pressure measurement to be a biomarker for both hypertension and for CV and renal disease. Blood pressure measurements are both prognostic indicators and treatment targets and many clinical trials have shown that reducing persistently elevated blood pressure reduces morbidity and mortality associated with hypertension. The optimal treatment target goal is continuing to be modified as further clinical studies are completed and will likely vary depending on patient comorbidities.

Before a treatment strategy can be implemented, it is important to properly and accurately diagnose hypertension. Evaluation of a patient with hypertension includes a careful review of CV risk factors and assessment of target organ involvement. Elevated blood pressure readings should be recorded using proper technique on at least three separate occasions to establish a persistent elevation in blood pressure unless the pressure is markedly elevated (generally ≥180/110 mm Hg).

Proper blood pressure measurement technique is crucial to avoid over and under diagnosis of hypertension (see Chapter 4, Chapter 5 for in-depth discussion). Proper blood pressure measurement technique can help eliminate both human error in measuring blood pressure and the reactive component responsible for elevation in blood pressure above the basal blood pressure when an individual is in a relaxed state. If three or more clinic visits document blood pressure readings that are 140/90 or higher mm Hg measured by proper technique, a diagnosis of hypertension can be made. Home blood pressure monitoring or ambulatory monitoring can be used to diagnose hypertension and can be useful for the diagnosis of white coat or masked hypertension.

There are a number of blood pressure measuring devices including the older mercury manometers, aneroid manometers with a dial in the center, and automatic electronic devices. The mercury manometer has been considered the gold standard for blood pressure measurement but because of concerns with mercury toxicity, is largely unavailable. Aneroid manometers are generally accurate but can become inaccurate over time, usually underestimating blood pressure. It has been assumed that automatic electronic blood pressure measurement devices are more accurate by eliminating human error, but are subject to the same inaccuracies in blood pressure measurement if proper technique is not used in obtaining the blood pressure.

How to Measure Blood Pressure

Proper blood pressure measuring technique is crucial for accurate blood pressure readings (see Chapter 4, Chapter 5 for in-depth discussion). Blood pressure is generally measured with a patient sitting comfortably with both feet on the floor and the legs not crossed. As the patient is sitting comfortably, consider factors that may have an impact on the blood pressure measurement such as pain, recent caffeine or tobacco use, recent exercise, or use of certain over-the-counter medications such as nonsteroidal antiinflammatory medications. The clinic setting should be relaxed and quiet (talking can raise blood pressure). The arm wearing the blood pressure cuff should be supported (resting on a table) and relaxed (avoid tensing the muscles). The center of the blood pressure cuff should be at about heart level. Ideally the patient should be relaxed and sitting quietly for a minimum of 5 minutes before a blood pressure check. Multiple blood pressure readings each about 60 seconds between readings should be obtained. The first blood pressure reading is generally discarded. If the next two readings are within 5 mm Hg of each other, the readings can be averaged for the blood pressure measurement. If there is a greater than 5 mm Hg difference, further blood pressure readings are obtained until two readings are within the range. A blood pressure reading should be taken with the cuff over the bare arm and not over clothing. It is recommended to take readings from both arms at least on the first visit to determine if there are significant differences between the two arms. In general, blood pressure is slightly higher in the dominant arm.

Many patients are interested in home blood pressure monitoring. For accurate home blood pressure measurement, proper technique is required the same as in the office. A patient will need to be taught how to properly measure blood pressure and use the home monitoring device. Home blood pressure values tend to be slightly lower than office readings and some recommendations suggest that a persistent blood pressure of more than 135/85 mm Hg at home be considered hypertension. Ambulatory blood pressure monitoring is thought to be accurate and can give information about nocturnal blood pressure and diagnose white coat or masked hypertension. Ambulatory and home blood pressure monitoring correlate well if blood pressure is properly measured.

Hypertension Evaluation

Patients diagnosed with hypertension should have an evaluation for secondary causes, target organ involvement, and a CV risk assessment. Secondary causes of hypertension should be considered in all individuals with signs and symptoms suggesting a secondary cause such as hypokalemia as well as resistant hypertension. An evaluation of target organ involvement can be individualized depending on the age and physical examination of the patient. Screening laboratory evaluation should include electrolytes and kidney function. An evaluation for microalbuminuria can be considered in patients where there is concern about early kidney involvement or in individuals with other comorbidities that can affect the kidney such as insulin resistance. A cardiac evaluation can be considered if there are signs and symptoms suggesting cardiac disease. An echocardiogram can identify left ventricular hypertrophy and may show signs suggesting ischemic disease. An echocardiogram can measure left ventricular mass and evaluate for both systolic and diastolic dysfunctions.

A hypertension evaluation can help determine an overall general strategy for treatment and may implicate certain hormonal systems involved in the hypertension. A careful evaluation may help determine if a patient is salt sensitive, hyperadrenergic (e.g., high resting heart rate usually >84 beats per minute), has overstimulation of the renin-angiotensin system, or has inappropriate levels of aldosterone. These hypertensive subtypes will be further discussed later.