SYSTEMIC CONDITIONS
Systemic Hypertension
This silent killer could be lurking in your exam chair.
by Deepak Gupta, O.D., F.A.A.O.
Hypertension is often referred to as the "silent killer" because patients usually don't notice any symptoms before major damage occurs to organ systems. Left untreated, these patients may suffer stroke, myocardial infarction, renal failure, congestive heart failure and progressive atherosclerosis.
There is a tremendous opportunity to help patients in managing hypertension, provided we understand diagnosis, treatment and follow-up care.
The essentials
What we commonly refer to as blood pressure (BP) is actually broken down into two separate components: systolic pressure and diastolic pressure. The systolic measurement (the top number) represents the pressure of blood against the artery walls when the heart has just finished pumping (contracting). The diastolic measurement (the bottom number) is the pressure of blood against the artery walls between heartbeats, when the heart is relaxed and filling with blood.
The classic definition of normal BP was 120/80mmHg, but a new classification scheme in recent years reflects a more aggressive approach to diagnosing and managing hypertension. Millions whose BP was previously considered borderline-high (130- to 139mmHg/85- to 89mmHg) or normal (120/80mm Hg) now fall into the pre-hypertension range.
Diagnosis
Proper diagnosis and management of a hypertension suspect includes physical and laboratory tests. Lab tests usually include a 12-lead electrocardiogram, urinalysis, complete blood count, blood chemistries (potassium, sodium, creatinine, fasting glucose, lipid profile) and calcium.
Primary-care doctors use this combination approach to assess cardiovascular risk factors that affect prognosis and treatment. This approach also reveals potentially identifiable causes of hypertension and signs of target-organ damage.
We, as optometrists, can play a role in diagnosis by employing a BP cuff as part of our exam routine. Many variables can impact BP, however, so don't base your suspicion of hypertension on an isolated reading. Instead, verify elevated BPs on multiple occasions over time. Obviously, one of the most important factors in this process is the accuracy of the measurement; even seemingly trivial errors can potentially misclassify a patient.
Management
As with glaucoma and intra-ocular pressure (IOP), the trend in managing hypertension in the past several years has been toward more stringent control and further lowering of BP. Management strategies focus on an individual approach that includes the influence of additional comorbidities on the selection of proper anti-hypertensive therapy. For example, a patient who also has diabetes may have lower management goals than a person with only hypertension. In addition, there is an increased awareness for cultural and sociodemographic factors that can impact the success of treatment, such as noncompliance due to poor understanding or costs of therapy.
Most patients who have hypertension are unable to maintain proper BP control with a single agent. Rather than increase the dose of one anti-hypertensive agent to the maximum recommended dosage, use two or more drugs with complementary mechanisms of action at lower doses. Doing so lowers BP without dramatically increasing the risk for adverse effects. The following section outlines the currently available anti-hypertensive classes.
• Angiotensin-converting enzyme (ACE) inhibitors. ACE inhibitors block an enzyme involved in constriction of the blood vessels. As a result, blood vessels relax and widen, making it easier for blood to flow through the vessels. This, in turn, lowers BP. These medications also mildly increase the release of water and sodium to the urine, which also helps lower BP. ACE inhibitors are a good choice for diabetics because they don't affect blood sugar levels and may help protect the kidneys. Side effects include dry cough, rash or itching, allergy-like symptoms and excess potassium (hyperkalemia), especially in people with kidney failure.
• Calcium-channel blockers. These work by reducing the amount of constriction of the blood vessels, making it easier for blood to flow through the vessels, thus lowering BP. They are especially effective in older adults, African Americans and individuals who have a difficult time reducing their sodium intake. They work by limiting the movement of calcium into the cells of the heart and blood-vessel walls, which makes it easier for the heart to pump and dilate blood vessels. Side effects include dizziness, headache, flushing, fluid buildup in legs (peripheral edema) and rapid heart rate.
• Angiotensin II receptor blockers (ARBs). These agents block the action of a hormone that causes vasoconstriction. As a result, blood vessels dilate, making it easier for blood to flow, thus reducing BP. They also increase the release of sodium and water into the urine, which also lowers BP. Side effects include diarrhea, stomach problems, muscle cramps, back and leg pain, dizziness, insomnia, cough, sinus problems and upper respiratory infection.
• Diuretics. These cause the kidneys to remove sodium and water from the body, which helps to relax the blood-vessel walls, thereby lowering BP. The most popular drug in this category is hydrochlorothiazide. This drug class is divided into loop diuretics, which increase urine output quickly for a few hours, and potassium-sparing, which, unlike most diuretics, don't cause potassium levels to drop.
Diuretics are usually recommended as one of at least two medications to control high BP. Diuretics are especially beneficial in older and overweight patients, African Americans and in those who have heart failure.
A recent study (Antihypertensive and Lipid-Lowering Treatment to Prevent Heart Attack Trial) compared a diuretic with an ACE inhibitor and calcium-channel blocker. Results showed that diuretics are as effective as ACE inhibitors and calcium-channel blockers in preventing fatal and nonfatal heart attacks.1
| OCULAR FINDINGS OF HYPERTENSION |
|---|
| Systemic hypertension can affect the retinal, choroidal and optic nerve circulations. Sometimes, we can see changes in the retinal vasculature due to hypertension. Common hypertensive retinal changes are flame-shaped hemorrhages in the superficial layers of the retina and cotton-wool patches due to occlusion of the precapillary arterioles. Patients who've had long-standing hypertension can demonstrate arteriolar sclerotic vascular changes, such as copper or silver wiring of the arterioles. Another frequently encountered sign of chronic hypertension is lipid exudates resulting from abnormal vascular permeability. One rarely encountered ocular sign is the swelling of the optic disc. This situation arises in patients who have severely elevated, uncontrolled hypertension. These patients are at risk of developing heart and renal failure and hypertensive encephalopathy. Obviously, the BP must be lowered, but you and the patient's primary-care doctor must do it in a controlled fashion because a sudden drop in tissue perfusion can result in infarction of the optic disc and subsequent blindness. In the case of a patient with extremely elevated blood pressure, along with a phone call to the patient's primary-care physician, send the patient to the hospital via ambulance, where they can lower the patient's blood pressure gradually. |
• Beta-blockers. Beta-blockers lower BP by decreasing heart rate and the amount of blood the heart pumps out with each beat and relax the blood vessels. Side effects include worsening of asthma, slow heart rate, fatigue, depression, nightmares, confusion, decreased high-density lipoprotein (HDL), ("good" cholesterol), increased blood sugar levels, erectile dysfunction, rapid heart rate and high BP if medication is withdrawn suddenly. In addition, beta-blockers can mask warning signs of low blood sugar in diabetics (relative contraindication) and limit endurance of patients who exercise.
• Diet. Encourage patients to make lifestyle changes, even if they aren't on medical therapy. Specifically, recommend a regular exercise program and dietary changes. An ideal diet consists of fruits, vegetables and low-fat dietary products with a reduced amount of saturated and total fat (Dietary Approaches to Stop Hypertension, or DASH diet; www.nih.gov/news/pr/apr97/Dash.htm). In some patients, these changes have demonstrated BP-lowering effects similar to single-drug therapy.
The vast majority of patients who have hypertension will have it for the rest of their lives. So, a long-term management plan is essential, as is compliance and cooperation. OM
1. The Antihypertensive and lipid-lowering treatment to prevent Heart Attack Trial Allhat. National Institutes of Health.
http://www.nhlbi.nih.gov/health/allhat/in dex.htm. (Accessed 5/15/07.)
Dr. Gupta practices full scope optometry in Stamford, Conn. He's also clinical director of The Center for Keratoconus at Stamford Ophthalmology. E-mail him at Deegup4919@hotmail.com.
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