doi: 10.1161/01.CIR.0000079541.75462.AA
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(Circulation. 2003;107:e9045.)
© 2003 American Heart Association, Inc.
Cardiovascular News
Circulation Newswriter
Incremental Benefits Seen for Electron-Beam Tomography
A 37-month study of 5635 asymptomatic adults who had undergone electron-beam tomography (EBT) found that 224 evaluated cardiac events were associated with coronary artery calcium, diabetes, hypertension, and smoking, said researchers from the University of Illinois at Chicago College of Medicine and College of Medicine and Northwestern University Feinberg School of Medicine in a report in this week’s issue of the journal Circulation (Circulation. 2003;107:2571–2576).
Of the study, led by George T. Kondos, MD, Associate Professor of Medicine at the University of Illinois at Chicago College of Medicine, the researchers wrote: "In summary, while office-based risk assessment remains the current recommendation for risk stratification in the general population, the association between EBT CAC [coronary artery calcium] and cardiac events observed in this study of initially asymptomatic, middle-aged, low-to-intermediate cardiac risk individuals presenting for screening (the "worried well") suggests that in this group knowledge of the presence and the extent of EBT CAC provides incremental information above that defined by single or combined conventional CAD [coronary artery disease] risk factor assessment."
In an accompanying editorial titled "Coronary Artery Calcium and Cardiac Events: Is Electron Beam Tomography Ready for Prime Time?," William S. Weintraub, MD, Professor of Medicine at Emory University School of Medicine in Atlanta, Ga, wrote: "The real question now is not whether EBT adds information, but rather whether it adds sufficient information to justify its use, and if so, in which groups of patients" (Circulation. 2003;107:2528–2530).
He wrote, "EBT can only be justified if it can improve outcome. For EBT to successfully do this, it must be shown that the use of this test can help to successfully select appropriate therapy. Unfortunately, an unequivocal answer to this question is probably not possible, as this would require a massive clinical trial, which is extremely unlikely to ever be mounted."
He pointed out that EBT is more expensive than measurements of serum lipids or C-reactive protein, even though it may add more information than the other tests. He noted that no satisfactory cost-effectiveness test of the technology has been published.
He notes that there is no good answer for the question of whether EBT should be used routinely. "Routine EBT for all adults probably cannot be justified. People at low risk should not need EBT, whereas people at high risk of events should have risk factors treated aggressively no matter what the EBT test shows. Thus, EBT would seem to be most useful in people in whom risk is uncertain and where EBT may help guide therapeutic or even further diagnostic options. Hopefully, as more information becomes available about this test, the place of EBT will be increasingly clear," he wrote.
Raising the Ante in Blood Pressure Control
In a move that affected millions of people, the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of Blood Pressure said in its Seventh Report that people who had previously been told they had normal or high normal blood pressure were classified as "prehypertensive" [JAMA. 2003;289:(DOI 10.1001/jama.289.19.2560); available at http://jama.ama-assn.org/cgi/content/full/289.19.2560v1].
The report, which appeared online early in The Journal of the American Medical Association, notes that those with prehypertension have blood pressure of 120 to 139 mm Hg/80 to 89 mm Hg. The report also states: "The risk of CVD [cardiovascular disease], beginning at 115/75 mm Hg, doubles with each increment of 20/10 mm Hg; individuals who are normotensive at 55 years of age have a 90% lifetime risk for developing hypertension."
They recommended that people considered prehypertensive should be encouraged to follow health-promoting lifestyle modifications that reduce their risk of developing cardiovascular disease. They also recommended thiazide-type diuretics as the first-line drug treatment in patients with uncomplicated hypertension, either alone or in combination with other classes of drug.
"Certain high-risk conditions are compelling indications for the initial use of other antihypertensive drug classes," the authors wrote. "Most patients with hypertension will require 2 or more antihypertensive medications to achieve goal BP [blood pressure] (<140/90 mm Hg, or <130/80 mm Hg for patients with diabetes or chronic kidney disease)."
They noted that if blood pressure is more than 20/10 mm Hg above the goal blood pressure, physicians should consider therapy with 2 agents, one of which should be a thiazide diuretic.
They noted that changes in medication work only in patients who are motivated. "Motivation improves when patients have positive experiences with and trust in the clinician. Empathy builds trust and is a potent motivator. Finally, in presenting these guidelines, the committee recognizes that the responsible physician’s judgment remains paramount."
The 6-Month "Fix"?
Two studies in the May 22, 2003, issue of The New England Journal of Medicine, found that patients placed on low-carbohydrate "Atkins-style" diets lost more weight at 6 months than did patients on a low-fat, low-calorie diet. However, in the study that lasted 12 months, the difference in weight loss disappeared.
In a study led by Gary D. Foster, PhD, of the University of Pennsylvania School of Medicine (N Engl J Med. 2003;348:2059–2073), researchers monitored 63 obese men and women for a year. The subjects were randomly assigned to either a low-carbohydrate, high-protein, high-fat diet or a low-calorie, high-carbohydrate, low-fat diet. They noted that professional contact was minimal in order to mimic the usual approach to such diets.
Those on the low-carbohydrate diet lost more weight at 6 months (an average of 7 pounds versus 3.2 pounds for those on the low-fat, low-calorie diet). However, at 12 months, the difference was no longer statistically significant (4.4 pounds for the low-carbohydrate diet versus 2.5 on the more conventional diet).
At 3 months, total and low-density lipoprotein cholesterol levels were essentially the same. However, those on the low-carbohydrate diet had greater decreases in triglycerides and greater increases in high-density lipoprotein cholesterol levels than those on the other diet. Both diets decreased diastolic blood pressure and insulin response to an oral glucose load.
In a second study (N Engl J Med. 2003;348:2074–2081) led by Frederick F. Samaha, MD, from the Philadelphia Veterans Affairs Medical Center and the University of Pennsylvania Medical Center, 132 severely obese subjects with a high prevalence of diabetes or metabolic syndrome were randomly assigned to a low-carbohydrate diet or a conventional one that restricted fats and calories. At the 6-month completion of the study, 79 subjects had remained on the assigned diets.
Those on the low-carbohydrate diet lost more weight than those on the conventional diet (5.8 versus 1.9 kilograms) and had greater decreases in triglycerides and improvements in insulin sensitivity. The authors wrote: "Future studies evaluating long-term cardiovascular outcomes are needed before a carbohydrate-restricted diet can be endorsed."
In an accompanying perspective, Robert Bonow, MD, of Northwestern University Feinberg School of Medicine and the current president of the American Heart Association, and Robert H. Eckel, MD, of the University of Colorado Health Sciences Center in Denver, note the severe problem of overweight that affects nearly two thirds of adult Americans. More than 30% are obese.
They noted that in both groups, adherence to dietary regimens was poor, and that in one study, the difference in weight loss disappeared after a year.
"This finding could reflect the small number of subjects remaining in the study at that time or the possibility that adherence to the diet was low even among those who continued in the study. Any approach to caloric restriction that is not compatible with daily lifestyle patterns is difficult to maintain over the long term," they wrote. "The results of both studies demonstrate that initial weight loss is much easier to achieve than is long-term maintenance of weight loss. Even if long-term adherence is possible, there are concerns related to the long-term use of this diet since its high content of fat (particularly saturated fat) is potentially atherogenic."
They concluded: "For society as a whole, prevention of weight gain is the first step in curbing the increasing epidemic of overweight and obesity. Until further evidence is available regarding the long-term benefits of a low-carbohydrate approach, physicians should continue to recommend a healthy lifestyle that includes regular physical activity and a balanced diet."
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