Under Pressure
While usually manageable, high blood pressure sometimes defies a quick fix,
rising out of control and presenting serious health consequences.
Having your blood pressure taken at a doctor’s office is usually an uneventful process. In fact, it is so easy that you may opt to take your own blood pressure at an automated machine in a pharmacy. But understanding how the numbers in a pressure reading relate to your health is not always as simple or straight forward.
For one thing, the rules have changed. A panel of American physicians now says that blood pressure of 120/80 mm Hg, once thought of as normal, is not good enough to head off the serious consequences of high blood pressure.
Under new national guidelines issued in the summer of 2003, blood pressure ranging from 120/80 mm Hg to 139/89 mm Hg now signals pre-hypertension, a condition in which patients begin facing rising risk for heart attack and stroke. As a result, some of those who thought they were perfectly healthy abruptly found out they might not be so safe after all.
Though controversial—some physicians say the guidelines create unnecessary anxiety—the new Joint National Committee on Prevention, Detection, Evaluation and Treatment of High Blood Pressure guidelines have succeeded in getting people talking about hypertension, which affects one in four adults, or more than 50 million people in the United States alone. Two-thirds of Americans over age 65 have pressure above 140/90 mm Hg—the watershed for high blood pressure.
“Hypertension is a huge issue,” says Vito M. Campese, M.D., professor of medicine and chief of the division of nephrology at the Keck School of Medicine of USC. “The reality is that in the U.S., approximately 70 percent of people with high blood pressure do not even meet the goal of 140 over 90—and the U.S. is doing the best of all, worldwide, in controlling blood pressure.”
Some patients can drop their blood pressure simply by changing diet, cutting salt or coffee intake, losing weight, exercising and taking medications. But for many others, hypertension is complicated, defies a quick fix or is simply out of control.
Heart of hypertension
Blood pressure is the force that blood exerts against the walls of arteries. When doctors talk about blood pressure, they are referring to the pressure at two different times. Systolic blood pressure (the top or first number in a pressure reading) is taken during a heartbeat, when the heart squeezes and pumps blood through the system. Diastolic blood pressure (the bottom or second number in a pressure reading) is taken while the heart relaxes between beats.
When blood pressure is too high, the heart must work too hard to pump blood throughout the body. It can have other effects, too.
“Hypertension can damage arteries in the brain and cause enlargement of the heart. That can lead to sudden death, heart attack or heart failure or stroke. It is the second most common cause of kidney failure and also is one of the most important factors in atherosclerosis,” says nephrologist Mitra Nadim, M.D., assistant professor of medicine at the Keck School and clinical specialist in hypertension. And hypertension’s effects reach far into every home in the nation: Heart disease and stroke are the first- and third-leading causes of death among Americans.
Yet few people can tell they have high blood pressure. Hypertension rarely announces itself, even among Nadim’s patients, whose systolic blood pressure may regularly reach 200 mm Hg or more.
“That’s why it’s a silent killer,” Nadim says. “Even when physicians detect hypertension and prescribe medication, sometimes patients won’t take it because they just don’t feel bad.”
Stress health
Campese, a clinical specialist in hypertension, directs the new, multi-disciplinary USC Hypertension Center, where experts diagnose and treat problems with blood pressure—whether it is too high or too low. Kidney experts, vascular surgeons, cardiologists and nutritionists at the center all work together to control stubborn hypertension, in particular.
“In patients with substantial hypertension, the lack of ability to control blood pressure can result in significant disease,” says Fred A. Weaver, M.D., professor of surgery, chief of the division of vascular surgery at the Keck School and the center’s vascular expert. Howard N. Hodis, M.D., professor of medicine and preventive medicine, provides the center’s cardiovascular medicine expertise.
As Campese and Weaver explain it, USC physicians have a heritage of handling the toughest cases in hypertension. The late Vincent DeQuattro, M.D., a former colleague at the Keck School, was renowned in the field. Now, they are carrying on his legacy by drawing on their own National Institutes of Health-funded research and providing in-depth testing, careful follow-up, dietary counseling and more.
“There’s no place a patient can go in L.A. today where they can get this type of collaborative treatment,” Weaver says, “and it’s incredibly uncommon on the West Coast.”
Adds Campese: “The keys to halting hypertension are early diagnosis, intervention, proper treatment and counseling. That requires a lot of work, and that’s why a team approach is so important.”
Open up
Part of the challenge of hypertension is finding its source. In about 10 percent of hypertension cases, a separate condition is causing the high blood pressure, and if that problem is treated, hypertension may disappear. Renal artery stenosis is a good example.
The leading cause of secondary hypertension, renal artery stenosis is a narrowing of the main artery supplying blood to the kidney. When the artery walls become so narrow that the kidney is starved of the blood it needs to work, the kidney produces growing amounts of a hormone called renin. That hormone is a strong blood pressure regulator, and increasing levels of it set in motion certain processes that increase blood pressure.
As blood pressure mounts higher, the kidneys themselves begin suffering the effects of hypertension. Kidneys may atrophy or scar, eventually completing a vicious circle by failing.
If patients develop high blood pressure before age 30 or after age 50, unsuccessfully try numerous pressure-lowering medications or have atherosclerosis in other parts of the body, physicians often suspect renal artery stenosis as a possible culprit, says Weaver.
The good news is that the condition is treatable.
At the Hypertension Center, USC University Hospital radiologists can perform highly accurate renal artery duplex ultrasound as well as magnetic resonance angiography scans to create pictures of the kidneys and arteries surrounding them. Duplex scanning usually is only available in select academic medical settings such as the Hypertension Center, Weaver notes.
Once physicians track down the sites of stenosis through imaging, Weaver can clear the clogged arteries through a traditional open operation or endovascular surgical techniques.
Weaver and his colleague Douglas B. Hood, M.D., director of endovascular therapies in the division of vascular surgery, both perform the minimally invasive endovascular technique. In this procedure, surgeons thread a thin wire into an artery through a catheter placed in a small incision in the skin and guide the wire to the site of stenosis. The wire has an uninflated balloon on its tip. When placed in the right spot, the balloon is inflated. That presses fatty plaque against the artery wall and opens the blockage. Surgeons then deflate and remove the balloon; depending on the patient, they may also place a tiny scaffolding sleeve, called a stent, within the artery to keep it open.
Once the narrowing clears, in most cases, so does the hypertension.
Systolic sleuths
Sometimes, physicians find no obvious reason for high blood pressure. In these cases—called primary hypertension—USC physicians must dig a little deeper and work with the patient to get blood pressure under control.
One of the tools at their disposal is 24-hour blood pressure monitoring, in which a patient wears equipment that logs pressure levels throughout the day. USC physicians use the test results to create a therapeutic strategy.
“Usually, blood pressure drops at night. But in some, it doesn’t drop—and that can raise the risk of heart attack. This testing allows us to find this out, so that we can change the times that we dose drugs,” Campese says.
Physicians also want to know how hypertension relates to stress. Patients who experience so-called “white-coat hypertension”—elevated blood pressure at the doctor’s office—also are likely to have blood pressure spikes during other times of stress during the day. Other patients are particularly sensitive to coffee or salt.
Race is also important; African Americans get hypertension more often and at earlier ages than Caucasians, and it tends to be more severe.
Rising risk
Clearly, no two patients are the same, which is why Keck School hypertension specialists believe so strongly in specialized, individualized care.
And that is part of the reason why Campese is concerned about the recent changes in blood pressure guidelines that identify some patients as pre-hypertensive. As many as 46 million Americans may fall into the new pre-hypertensive category. The intention is good, he believes, but patients’ risks vary, so the new definition might alarm patients who actually are not at high risk.
“It’s blood pressure combined with other risk factors, such as high cholesterol or smoking, that raises risk for people in the pre-hypertension group,” says Campese, who served on the previous Joint National Committee on Prevention, Detection, Evaluation and Treatment of High Blood Pressure when it issued its sixth set of guidelines in 1997.
“These new guidelines are a recognition that risk for cardiovascular disease already begins to increase once you go past 120/80,” he says. A blood pressure increase from 115/75 mm Hg to 135/85 mm Hg doubles the chance of a heart attack, stroke or other cardiovascular event.
Campese favors the approach recently recommended by European physicians. They suggest that everyone keep blood pressure below 140/90 mm Hg, with lower blood pressure goals for some patients within the context of their cardiovascular risk as a whole.
The ideal, says Campese, is to make long-lasting lifestyle changes that lower disease risk, not just focus on problems after they appear. “Most people who are hypertensive don’t have symptoms,” he says. “Blood pressure may seem like just a number. But it’s better to increase awareness of it and lower it, before hypertension becomes a problem.
PRESSURE PACT The Joint National Committee on Prevention, Detection, Evaluation and Treatment of High Blood Pressure recommendations included these new guidelines for patients: • Blood pressure below 119/79 mm Hg: The goal for maintaining a low risk of heart disease and related problems. • Blood pressure between 120/80 and 139/89 mm Hg: Pre-hypertension. Indicates the patient is at risk of developing high blood pressure. Physicians recommend lifestyle modifications, such as exercise and healthy diet, to prevent cardiovascular disease in these patients. • Blood pressure above 140/90 mm Hg: High blood pressure. Physicians advise lifestyle modification and generally prescribe one or more medications depending on pressure levels and the patient’s medical history. Vito M. Campese, M.D., chief of the division of nephrology at the Keck School, notes that the presence of other accompanying diseases or risk factors, such as diabetes or kidney disease, can alter guidelines for individual patients. A blood pressure reading of 130/80 mm Hg in a diabetic patient, for example, causes greater concern than the same level in someone without risk factors. Also, in those over age 50, a systolic blood pressure reading greater than 140 mm Hg poses greater cardiovascular risk than a diastolic blood pressure reading greater than 90 mm Hg. For more information on the new guidelines, go to www.nhlbi.nih.gov/guidelines/hypertension. |