For the most part, measures of blood pressure obtained in the clinic and those obtained out of the clinic, either from home or ambulatory blood pressure recordings, are intercorrelated. That is to say, individuals who have elevated blood pressures in the clinic typically have higher blood pressures outside of the clinic.
Conversely, individuals with normal blood pressures in the clinic typically exhibit normal pressures during monitoring out of the clinic. There are, however, two categories of patients for whom this is not the case. Some patients have significantly greater blood pressures in the clinic than during daily life (see Figure 2.2).
Although these patients have historically been referred to as ‘white coat’ hypertensive patients, based upon the premise that they were exhibiting a conditioned anxiety response to being evaluated by a medical professional wearing a white coat, a more descriptive term for this condition is isolated clinic hypertension. (Some patients indeed exhibit a ‘white coat’ effect without being hypertensive, as I will discuss in a moment.) In contrast, patients who exhibit elevated blood pressures throughout daily life, but normal blood pressures in the clinic, are referred to as isolated clinic normotensives.
Figure 2.2.Categorization of hypertension, normotension, isolated clinic hypertension, and isolated clinic normotension from clinic and either home or ambulatory blood pressures. Adapted from Pickering et al. (1999), Task Force V: White coat hypertension, Blood Pressure Monitoring, 4, 333???341. Copyright © (1999), with permission from Lippincott, Williams, and Wilkins.
In both cases, one cannot rely solely upon clinic blood pressure determinations to evaluate patients regarding treatment decisions. Either home or ambulatory measures of blood pressure are needed to provide an accurate portrayal of the patient’s current blood pressure status.
Before we discuss each of these conditions, it is important to acknowledge the importance of the considerations regarding appropriate reference values for both home and ambulatory blood pressures. If differential reference values are adopted, a patient with average clinic blood pressures of 144/92 mm Hg and average home blood pressures of 136/86 mm Hg would be diagnosed with essential hypertension using one set of criteria and with isolated clinic hypertension using another set of criteria.
To complicate matters, not all research on patients with isolated clinic hypertension or isolated clinic normotension employs the same reference values for assigning patients to these categories. Keeping this limitation in mind, let’s examine the literature regarding these two interesting clusters of patients.