31. Hypertension: Mechanisms and Diagnosis

Hypertension, defined as an arterial blood pressure (BP) of ≥140/90 mmHg, affects one in three US adults and is a major independent risk factor for myocardial infarction, stroke, and renal failure. Only 43 % of the total hypertensive population has their BP controlled to goal (<140/90 mmHg). Pre-hypertension refers to a BP of 120–139/80–89 mmHg and also increases cardiovascular risk, compared with normal BP (<120/80 mmHg). Definitions are provided for the terms essential hypertension, secondary hypertension, refractory (resistant) hypertension, pseudohypertension, white coat hypertension, masked hypertension, and hypertensive crisis. This chapter deals with definitions, measurement of BP, the initial workup of the hypertensive patient, target-organ damage (vascular hypertrophy, left ventricular hypertrophy, myocardial infarction, stroke, encephalopathy, chronic kidney disease, and retinopathy), hypertensive emergency and urgency, and risk factor profiling. The section on the pathogenesis of primary hypertension deals with genetic factors, increased cardiac output, excessive dietary sodium, renal sodium retention, increased activity of the renin–angiotensin system, increased sympathetic activity, increased peripheral resistance, abnormal cell membrane ion transport, endothelial function, and insulin resistance and hyperinsulinemia. Causes of secondary hypertension include renal artery stenosis, renal parenchymal disease, pheochromocytoma, and abnormalities of adrenocortical function.