Clinical Briefs

Use of B-Type Natriuretic Peptide in the Evaluation and Management of Acute Dyspnea

By Louis Kuritzky, MD

The etiology of acute dyspnea (DSP) can be diverse, and it is often especially difficult to separate pulmonary from cardiac causes. Recently, brain natriuretic peptide (BNP)—so called because of its original identification in porcine brain—has become recognized as a valuable diagnostic tool because it promptly rises in response to pathologic cardiac ventricular wall stress (eg, heart failure), and its levels are proportional to the degree of cardiac dysfunction. BNP is not affected by pulmonary conditions such as COPD, unless COPD has been of sufficient severity to result in right ventricular failure.

Whether standard clinical evaluation or BNP-based diagnosis provides more effective management for acute DSP was studied in this trial (n = 452) Primary end points were time to discharge and cost, both of which would be presumed to be adversely affected by inaccurate initial diagnosis.

Evaluation for all patients in the emergency department included an initial history and physical, EKG, oximetry, blood chemistry, chest X-ray and (for half of the group) point-of-contact BNP testing (15 minute on-site results). A BNP level > 100 pg/mL was considered sufficiently elevated to be consistent with heart failure.

Use of BNP testing provided an advantage for time-to-discharge from the ED (63 minutes vs 90 minutes), need for hospitalization (75% vs 85%), time to hospital discharge (8 days vs 11 days), and intensive care costs ($874 vs $1516). Use of BNP testing, in concert with traditional diagnostic tools, shortens the time to initiation of specific and appropriate treatment, and hospitalizations. Overall, use of the BNP test reduced total treatment cost by more than 25%.

Mueller C, et al. N Eng J Med. 2004;350:647-654.

Dr. Kuritzky, Clinical Assistant Professor, University of Florida, Gainesville, is Associate Editor of Internal Medicine Alert.

Association Between C-Reactive Protein and Age-Related Macular Degeneration

By Louis Kuritzky, MD

Age-related macular degeneration (AMD) is an important cause of loss of visual acuity, and because there are few effective treatments, enhanced prevention is paramount. The association between some cardiovascular risk factors (eg, smoking, dyslipidemia, obesity) and AMD has not gone unnoticed. Since C-reactive protein (CRP) has been associated with cardiovascular risk, it has become an item of interest whether CRP is similarly associated with AMD.

Study subjects (n = 4757) comprised persons with mild (n = 1063), intermediate (n = 1621), and advanced (n = 956) AMD, and controls (n = 1117). Subjects were followed every 6 months with tests of visual acuity and fundoscopy.

CRP levels were particularly discordant in persons with advanced AMD compared to those with no AMD. Even after statistical adjustment for age, sex, smoking, and obesity, CRP levels maintained a relationship with AMD. Persons in the 90th percentile for CRP had almost a 2-fold increased odds ratio for AMD. Seddon and colleagues suggest that CRP elevation is an independent risk factor for AMD. Since this is the first evidence to implicate inflammation (as manifest by CRP) etiologically in AMD, it remains to be shown whether modulation of CRP might have favorable effects on this end point.

Seddon JM, et al. JAMA. 2004;291: 704-710.

VZV Reactivation in Astronauts

By Carol Kemper, MD, FACP

Stress is a known trigger for reactivation of herpes viruses. Just the physical and psychological trauma of swapping alpha-male mice between 2 mouse colonies and the resultant battle for new alpha-male-dom has been shown to trigger reactivation of HSV in about half the mice. Herpes zoster can also reactivate after stress, including the stress of surgery.

After a 47-year-old healthy astronaut developed herpes zoster 2 days before a space flight, Mehta and associates decided to examine whether the stress of space flight can result in the reactivation of VZV. A total of 312 saliva samples, obtained from 8 astronauts before, during, and after space flight were examined by PCR. Amazingly, 61 of 200 (30%) specimens obtained during and after space flight were positive, compared with 1 of 112 (< 1%) obtained in a 234-265 day period before flying. No VZV was detected in 88 samples from 10 control subjects, who did not fly. Seven of 8 astronauts had at least 1 positive specimen during flight (2-12 days), while all 8 had anywhere from 1-8 positive specimens within 15 days of returning to earth.

Mehta SM, et al. J Med Virol. 2004; 72:174-179.

Dr Kemper is Clinical Associate Professor of Medicine, Stanford University, Palo Alto, Calif.