Pulse
Harbingers of Heart Disease
University of Minnesota researchers say that preventing cardiovascular events requires identifying heart disease long before patients have symptoms.
The patients who come to the University of Minnesota’s Rasmussen Center for Cardiovascular Disease Prevention don’t look sick. And most say they feel fine. But for one reason or another, they’re concerned they might have cardiovascular disease.
“Either they want to be proactive or they are worried about family history,” says Lynn Hoke, a nurse practitioner who manages the center, which offers a series of 10 tests that predict cardiovascular disease at an early stage. “There isn’t a lot out there to help people without symptoms who look healthy,” she says. “How do they really know what’s going on in their blood vessels?”
That’s a question that Rasmussen Center director and founder Jay N. Cohn, M.D., says he knew needed answering as long as 25 years ago, when he began to note that changes in arterial elasticity were early indicators of atherosclerosis. He would later suggest that endothelial dysfunction in the smallest vessels initiated the progression toward atherosclerosis and cardiovascular events.
In the 1980s, Cohn and electrical engineer Stanley Finkelstein, Ph.D., developed a method for measuring arterial elasticity that involved placing a small sensor on the wrist over the radial artery in order to obtain a blood pressure waveform. Special software analyzes the waveform in order to assess stiffness of the small and large arteries—a measure that provides far more information than pressure alone.
“It was our experience with that device that proved we could detect abnormalities in the arteries long before patients developed hypertension or had strokes or heart attacks. This encouraged us to seek additional methods that could help identify early disease,” Cohn says.
Cohn and his fellow researchers ended up with 10 measurements they felt would provide a comprehensive assessment of the health of the arteries and the heart and developed a scoring system for those tests (see “A Visit to the Center”). Of 1,500 patients screened since the Rasmussen Center opened, more than 60 percent had signs of early disease, despite being symptom-free.
A Visit to the Center
A visit to the Rasmussen Center for Cardiovascular Disease Prevention begins with an interview and exam. Patients then undergo the following 10 tests:
1. small-artery elasticity using pulsewave analysis
2. large-artery elasticity using pulsewave analysis
3. blood pressure at rest
4. blood pressure after three minutes of exercise
5. optic fundus photos taken with a digital camera
6. microalbuminuria
7. carotid artery ultrasound to measure artery wall thickness
8. electrocardiogram
9. left ventricular ultrasound to measure heart size
10. plasma B-type peptide concentration.
Each test result is scored 0 (normal), 1 (borderline), or 2 (abnormal). Patients then receive a composite score known as their Rasmussen score. A score of 6 or higher is considered cause for concern.
Patients also receive a written report that includes a summary of the test results, explanations of what the tests show, and recommendations for therapy or lifestyle changes, if indicated. The report is also sent to the patient’s primary physician.
Rasmussen Center director and founder Jay N. Cohn, M.D., says the testing costs approximately $1,800 but that most insurance companies in Minnesota cover it.—C.P.
Preventing heart disease is hardly a novel idea. What sets the Rasmussen Center’s approach apart from more conventional thinking is its focus on identifying early changes in cardiovascular function and structure rather than evaluating risk factors such as cholesterol, C-reactive protein, or blood sugar levels. “We do measure cholesterol. We do measure inflammatory marker, we do measure blood sugar,” Cohn says, explaining that they view these as contributors to the progression of disease. “But they do not represent disease. The disease is in the artery or the heart.” |
A New Approach to Prevention
When patients with demonstrable early disease are identified, treatment with statins, angiotensin-converting enzyme inhibitors, angiotensin-receptor blockers, and other antihypertensive drugs is recommended. “Prescription of such chronic pharmacopreventive therapy in asymptomatic individuals may seem aggressive,” Cohn and colleagues wrote in a paper published in
Hypertension in 2003, “but it appears potentially more rational than the current approach of antihypertensive and cholesterol-reducing therapy” based on risk factors alone. He notes that the current strategy results in people with no evidence of disease receiving treatment and others who may have early disease not getting the necessary therapies.
“This is completely revolutionary thinking,” says Daniel Duprez, M.D., Ph.D., director of research for the Rasmussen Center. “It’s like in the Middle Ages when Gallilleo started to say that the earth was not a plate anymore but a globe.” Duprez explains that a Framingham score, the standard predictor of risk for heart disease, is a biostatistical estimate that doesn’t enable physicians to identify who has disease. As a result, he explains, 100 people might receive treatment to prevent eight cardiovascular events. That approach, he points out, is inefficient and costly and exposes patients who don’t need medications to the side effects of drugs.
Duprez, Cohn, and others from the center have generated a spate of studies that support their approach, the first ones identifying the high percentage of asymptomatic patients who had heart disease and later ones showing the efficacy of treating them.
One of the most recent, which was published in the August 28, 2007, Journal of the American College of Cardiology, showed that giving the angiotensin blocker valsartan to asymptomatic patients who had early cardiovascular abnormalities slowed the progression of their disease and reversed damage. In the double-blind study of 76 individuals with markers for cardiovascular disease as determined by their Rasmussen score, half took valsartan for six months while the other half received placebo. Those who took the drug significantly reduced their Rasmussen score when they were retested a year later.
A paper submitted for presentation at an upcoming meeting further demonstrates the significance of the Rasmussen score. The scores of patients who had heart attacks or strokes following screening were higher than those of patients who did not experience such events. But there was no difference between the groups with regard to their Framingham risk profiles, which are based primarily on blood pressure and cholesterol levels. “Those were identical between people with events and those without,” Cohn notes.
In addition to confirming the presence of heart disease, Cohn says one of the clinic’s most valuable services is its ability to identify the one-third of patients who have no evidence of abnormality in their blood vessels or heart. “If they have no abnormality, we can tell them with some confidence that they don’t need to do anything to reduce their risk. That probably turns out to be a more valuable service than anything else because everyone who comes into our center is concerned.”—Carmen Peota