An Overview of the Expanded Definition and Classification of Hypertension Part 1/5

For the medical colleagues out there very aching to know all about the NEW JNC 8, these next few posts in the following days are for you..


Introduction

As epidemiologic and clinical data regarding the relationship between blood pressure (BP) and the risk for cardiovascular disease (CVD) have accumulated, a pronounced shift has taken place in how the disease of hypertension is viewed and defined. Cardiovascular (CV) risk has been found to be elevated at BP levels previously considered normal; in some cases, sporadic elevations in BP levels may be physiologically benign and not associated with additional CVD risk.[1-3] As a consequence, many hypertension experts consider elevated BP at its core a disease marker, rather than a cause of hypertension. Moreover, elevated BP, as 1 marker of CVD, frequently coexists with other equally compelling disease markers.[2] Elevated BP should not, therefore, be viewed or treated in isolation, but considered in the context of whole patient care, which takes into account the presence of other risk factors and disease markers for CVD to achieve a more comprehensive, or global, assessment of CV risk.

With these points in mind, in 2005, the Hypertension Writing Group (HWG), a national group of hypertension specialists, proposed a new definition of hypertension as "a progressive cardiovascular syndrome, the early markers of which may be present even before BP elevations are observed."[4] The stated goal of the new definition was to identify individuals at risk for CVD at an earlier point in the disease process, as well as to avoid labeling persons as hypertensive who are at low risk for CVD.[4] Viewed from this perspective, the HWG believed that threshold-based classification systems of hypertension, such as that endorsed in the Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure (JNC 7),[5] while serving as tools to identify patients across a broad range of CVD risk, may lead to underestimation or overestimation of clinical risk within individual patients. In either case, the presence or absence of other disease markers or risk factors, the coexistence of target-organ damage, or both can be used to risk-stratify patients with hypertension more accurately.

To simplify risk stratification and align it more closely with clinical practice, the HWG proposed classifying all patients as either normal or hypertensive (eliminating the prehypertension category proposed in JNC 7), with hypertension classified into stage 1, stage 2, or stage 3.[4] Because the CV syndrome represented by hypertension may be present even when BP falls within the normal category by conventional standards, the risk categories created by the HWG focus not on BP levels per se, but on the presence of deleterious BP patterns or the presence of CVD. Stages of hypertension are further categorized based on the presence of risk factors for early, advanced, or progressive CVD, as well as by other CVD markers (classified as BP, cardiac, vascular, renal, and retinal changes) and target-organ damage (classified as cardiac, vascular, renal, and cerebrovascular).[4]

Beyond the goal of providing a more clinically relevant assessment of global CV risk in clinical practice, this paradigm shift served to focus attention on the enormous unmet need regarding prevention and optimal treatment of hypertension across a spectrum of fields, from basic research and drug development to patient education and clinical management.[4] Two critical areas of research in particular -- the development of specific and sensitive cost-effective tests that can detect early CVD markers in the clinical setting, and the development of strategies to slow or prevent the onset of target-organ damage or overt CVD by treating early vascular derangements -- may benefit from being examined within the context of the categories for hypertension.

Recently, the HWG further refined and updated the definition and classification of hypertension.[6] This article reviews the revised definition and classification scheme and the implications for clinical practice. As the authors stressed, however, while definitions of disease are useful for detection, management, research, and education, definitions alone do not constitute recommendations for treatment. In the latter case, the initiation of treatment should be individualized and guided by CV risk, rather than BP thresholds.[1]