Clinical Briefs in Primary Care
Long-Term Effects of Bariatric Surgery: Improved CV Outcomes
Source: Sjostrom L, et al. JAMA 2012; 307:56-65.
Increases in body mass index (BMI)above normal are linearly associated with cardiovascular (CV) morbidity and mortality. The increased incidence of hypertension and diabetes in overweight and obese individuals explains some of this association. Since the weight reduction subsequent to bariatric surgery (BARS) is usually accompanied by improvements in blood pressure and metabolic profile, one would hope that this would translate into a reduction of CV events.
The Swedish Obese Subjects study provides data from this prospective controlled study of BARS (n = 2010) vs "usual care" (n = 2037) for adult obese subjects. The minimum BMI for inclusion was 34 kg/m2 in men and 38 kg/m2 in women. Subjects were followed for a median of 14.7 years.
The BARS subjects enjoyed a 53% relative-risk reduction in CV deaths (28/2100 vs 49/2037) and a 33% risk reduction in overall fatal and nonfatal CV events (199/2100 vs 234/2037) over the almost 15 years of follow-up.
Although the degree of excess BMI did not correlate with outcomes — i.e., persons who had higher baseline BMI did not enjoy a greater (or lesser) risk reduction than comparators — there was a correlation with insulin resistance. As manifest by baseline plasma insulin concentration, subjects with the highest degree of insulin resistance had the greatest degree of CV risk reduction. This long-term follow-up of a large surgical population is encouraging that BARS reduces CV risk. Demonstration of risk reduction requires both a large population and enduring follow-up, since most of the participants were much younger than are typically enrolled in CV risk reduction trials.
Long-Term Survival in SHEP Trial Participants
Source: Kostis JB, et al. JAMA 2011;306: 2588-2593.
The systolic hypertension in the elderly (SHEP) trial was a prospective, randomized, controlled trial of diuretic (chlorthalidone) vs placebo in 4736 subjects with isolated systolic hypertension over the age of 60. At the conclusion of the trial (4.5 years mean follow-up), chlorthalidone resulted in a statistically significant reduction in cardiovascular (CV) events, but only a favorable trend (NOT statistically significant) in CV mortality. Because of the favorable initial results, at the conclusion of the trial all SHEP participants were advised to use active treatment.
Kostis et al report on 22 years of follow-up of SHEP trial participants. According to their analysis, there was a beneficial difference noted between persons originally assigned to diuretic vs placebo: a statistically significant 11% reduction in CV death, although total mortality was not significantly different between the two groups. Benefits seen years after a clinical trial intervention has ceased are commonly termed "legacy effects," and suggest that a sustained period of blood pressure control with chlorthalidone may extend CV risk reduction over a much longer interval. Because all trial participants were encouraged to receive active treatment post-trial, the favorable between-group differences seen would likely be an underestimate of true attainable benefits.
Exercise and Weight Loss in Persons with Pre-existing Coronary Heart Disease
Source: Ades PA, et al. Chest 2011;140: 1420-1427.
There is still some debate about the relationship between being overweight and cardiovascular (CV) health, since among overweight individuals there is great diversity in levels of CV fitness as well as CV risk factors (e.g., hypertension, diabetes, dyslipidemia). Much of the insight we have today about the benefit of cardiac rehabilitation programs was gleaned from trial data in the 1970s and 1980s, at which time many fewer study subjects were obese or morbidly obese. Hence, determining the impact of exercise and weight loss in persons more representative of current coronary heart disease (CHD) demographics is pertinent.
Obese adults (mean baseline BMI = 32.3 kg/m2) with established CHD (n = 38) participated in a regimen of weight loss combined with one of two different intensity exercise programs (walking 45-60 minutes vs 25-40 minutes per session) for 4 months.
Endothelial function, as assessed by flow-mediated dilation, was improved in both groups, but improved more in the group with greater intensity of exercise. The authors also comment that the amount of endothelial functional improvement seen with weight loss was similar in magnitude to that attained with statin treatment. Degree of endothelial functional improvement correlated with amount of weight lost, suggesting a dose-response effect. In an era when more than 80% of persons entering cardiac rehabilitation programs are overweight or obese, it is encouraging that participation in rehabilitation programs that result in weight loss and sustained physical activity improve endothelial function.
Predicting Adverse Outcomes in Asthmatics: The Severity of Asthma Score
Source: Eisner MD, et al. Chest 2012; 141:58-65.
In the united states, approximately 5,000 persons die each year from asthma. Several metrics for predicting outcomes in asthmatics are available including the asthma control test, work productivity and impairment index-asthma, FEV1, and severity of asthma score (SOA). The SOA score is a validated questionnaire that incorporates asthma symptom frequency, medication use history, and hospitalizations for asthma among its 13 items. The Evaluating Clinical Effectiveness and Long-term Safety in Patients with Moderate-to-Severe Asthma study is an observational study of omalizumab or placebo in asthmatics with demonstrated inhalant allergen sensitivity. In the placebo arm (n = 2878), the SOA score was compared with the other metrics mentioned above for its ability to predict five asthma-related outcomes: exacerbations, hospitalizations, unscheduled office visits, emergency room visits, and need for systemic steroid treatment.
Of all the metrics chosen, SOA had the best predictive capacity, and was singular in that it had significant positive-predictive value for all five of the adverse asthma-related outcomes, whereas other tools were positively predictive in only a portion of the five outcomes. One of the attractive aspects of the SOA is that no special tools, lab tests, or measurements of pulmonary function are required to score it.
Subclinical Atrial Fibrillation
Source: Healey JS, et al. N Engl J Med 2012;366:120-129.
I have been a student of atrial fibrillation (AF) for some time, but had never come upon the term "subclinical" AF until this New England Journal of Medicine publication. The authors point out that although AF is often brought to our attention by awareness of an arrhythmia, it is often asymptomatic — what they call subclinical. Indeed, it is not uncommon to see patients presenting with ischemic stroke, heart failure, or syncope, only to discover that asymptomatic AF is the underlying etiology.
Healey et al report on a population of hypertensive seniors in whom either a pacemaker or defibrillator had been implanted but who had no prior history of AF (n = 2580). The implanted devices were programmed to report any episode of heart rate 190 beats per minute (bpm) or greater. Subclinical atrial tachyarrhythmia — defined as an asymptomatic occurrence of atrial rate > 190 bpm for more than 6 minutes — was detected in 35% of study subjects over 2.5 years of observation; asymptomatic episodes far outnumbered symptomatic tachyarrhythmia. The risk for ischemic stroke in persons experiencing any atrial tachyarrhythmia was increased by 2.5 fold.
These data may help to explain some of the ischemic stroke cases that have no immediately visible antecedent. On the other hand, the complex terminology that separates AF into persistent, paroxysmal, subclinical, permanent, etc, may not be helpful; the phrase "once a fibber, always a fibber" simplifies the fact that (except for transient AF associated with peri-operative stress), any episode of AF, regardless of duration or extinguishability, elevates thrombotic risk.
Real-life Use of Sunscreen in Ski Areas
Source: Buller DB, et al. J Am Acad Dermatol 2012;66:63-70.
Current recommendations for sunscreen include three fundamental steps: 1) application up to 30 minutes before exposure, 2) use of a sun protection factor (SPF) of at least 15 (higher if ultraviolet [UV] radiation is high), and 3) reapplication every 2-3 hours. Skiing is associated with high UV exposure because of the combination of altitude and snow reflection.
Buller et al interviewed adult skiers in the western United States and Canada (n = 4837). Subjects were interviewed face-to-face while riding on chairlifts and gondolas (I don't ever remember getting offered one of those tough, technical scientific jobs!).
Almost 50% of subjects reported using sunscreen with SPF 15 or higher, and most applied it 30 minutes before sun exposure. Reapplication was only performed by 20%. Only 4% of respondents fulfilled all three components of appropriate sunscreen use. Overall, men were substantially less compliant than women.
Messages about the importance of skin protection appear to be reaching the public, including young athletic adults. Further education about the need for reapplication, coupled with insights about circumstances of increased exposure risk (like skiing), might improve compliance in the future.
Long-Term Effects of Bariatric Surgery: Improved CV Outcomes; Long-Term Survival in SHEP Trial Participants; Exercise and Weight Loss in Persons with Pre-existing Coronary Heart Disease; Predicting Adverse Outcomes in Asthmatics: The Severity of Asthma Score; Subclinical Atrial Fibrillation; Real-life Use of Sunscreen in Ski AreasSubscribe Now for Access
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