Once antihypertensive medications are initiated, monitoring should be instituted at approximately monthly intervals to determine blood pressures and to assess side effects. Patients with stage II hypertension or with complicated comorbid illnesses may need more frequent monitoring. The serum creatinine and potassium levels should be monitored 1 to 2 times per year. When blood pressure goals are reached, patients may be seen in the office at 3-to 6-month intervals. Patients capable of home blood pressure monitoring should be encouraged to measure blood pressure at the same time twice weekly (20). If intolerable side effects develop, a different class of medications should be used and the patient’s progress monitored. Patients whose blood pressure is difficult to control with two agents should be considered for referral. Causes of resistance to therapy include diseases missed during the initial evaluation, unrecognized early end-stage disease, and poor compliance. Patients with evidence of target organ disease should be considered for referral to the appropriate specialist for more intensive diagnostic workup and therapy.
Cholesterol The dietary inﬂuence of cholesterol on atherosclerosis and its relationship to hypertension and cardiovascular events (myocardial infarction and stroke) is widely debated in the scientific and lay communities. The controversy centers on the effect of dietary cholesterol in assessing risk and prevention of cardiovascular disease (26,27). Many assume that all cholesterol and fat in the diet have negative health consequences (28). Cholesterol metabolism is complex, and some of our knowledge is extrapolated from animal models. The role of cholesterol testing (who, when, and at what age) is hotly debated among health care professionals, and the test itself is fraught with multiple variables that affect results. Understanding the metabolism of cholesterol will help identify and treat patients at risk of complications from hypercholesterolemia.
Terms and Definitions Cholesterol is usually found in an esterized form with various proteins and glycerides that characterize the stage of metabolism. The following components are important lipid particles in cholesterol metabolism:
Chylomicrons This large lipoprotein particle consists of dietary triglycerides and cholesterol. Chylomicrons are secreted in the intestinal lumen, absorbed in the lymph, and passed into general circulation. In adipose tissue and skeletal muscle, they adhere to binding sites on the capillary wall and are metabolized for energy production.
Lipoprotein Particle Lipoprotein particles are separated into five classes based on physical characteristics. The various cholesterol metabolites are separated by density. As lipoprotein particles are metabolized and lipids are removed for energy production, they become more dense.
Figure 9.3 Metabolic pathways of lipid metabolism. Apo, apoprotein; LP, lipoprotein; FFA, free fatty acid; IDL, intermediate-density lipoprotein; LDL, low-density lipoprotein; VLDL, verylow-density lipoprotein; HDL, high-density lipoprotein; LCAT, lecithin cholesterol acyltransferase.
Attached apoproteins are modified as cholesterol moves from the so-called exogenous pathway (dietary) to the endogenous pathway (postabsorption and metabolization by the liver).
Following are the subdivisions of the lipoprotein classes (Fig. 9.3).
Chylomicrons and remnants are composed of major lipids and apoproteins of the A, B-48, C and E classes. These are large particles made up of dietary cholesterol molecules that are absorbed with triglycerides.
Very low-density lipoproteins (VLDL) are transient remnants found after initial liver metabolism and compose only 10% to 15% of cholesterol particles. They consist of endogenously synthesized triglycerides.