Arrhythmia discrimination using hemoglobin spectroscopy in humans.

BACKGROUND: Inappropriate therapies are frequently delivered by implantable cardioverter-defibrillators (ICDs). We have investigated muscle perfusion as a means of augmenting arrhythmia discrimination by using implanted near-infrared spectroscopy. OBJECTIVE: To evaluate hemodynamic stability by monitoring muscle perfusion from within the ICD pocket, in fresh tissue and inside the scar capsule on preexisting ICD generators, during induced cardiac arrhythmias, in humans. METHODS: The sensor was implanted on or under the pectoral muscle, during ICD defibrillation threshold testing. A microvascular oxygenation trend indicator (O2 Index) was computed during 74 induced ventricular fibrillation and 34 normal sinus rhythm episodes in 34 patients and also during 28 atrial and 90 ventricular overdrive pacing episodes as simulations of supraventricular and ventricular tachycardias, respectively. RESULTS: On average, the change in oxygenation, based on the O2 Index, was statistically significant (P <.003) from baseline within 3 seconds following cardiac arrest. An optimized O2 Index, used for detecting the hemodynamic trend, exhibited a decreasing trend during ventricular fibrillation (P <.0001) and was different from that during normal sinus rhythm (P <.0001). The sensitivity for the detection of ventricular fibrillation was 100%, and the specificity for the rejection of normal sinus rhythm was 82% in the presence of scar tissue on the optical sensor. For a 35-mm Hg drop in the mean arterial pressure as the threshold for hemodynamic instability, the specificity for the rejection of hemodynamically stable atrial and ventricular pacing episodes was 93% and 71%, respectively. CONCLUSION: An implantable near-infrared spectroscopic sensor may be useful for hemodynamic monitoring during cardiac arrhythmias to prevent inappropriate therapy.

Methicillin-resistant Staphylococcus aureus in a high school wrestling team and the surrounding community.

OBJECTIVES: To describe a community outbreak of methicillin-resistant Staphylococcus aureus (MRSA) and to investigate risk factors for MRSA transmission and infection in a wrestling team. DESIGN: Case series and retrospective cohort study. SETTING: A high school wrestling team and the surrounding community in southern Vermont, 1993 to 1994. PATIENTS OR OTHER PARTICIPANTS: The case series included persons whose MRSA-positive infections were identified at a hospital laboratory from January 1, 1993, through February 28, 1994, and a health maintenance organization laboratory from July 1, 1993, through February 28, 1994. A wrestling team case-patient was a 1993-1994 team member with an MRSA-positive culture during the period from January 1, 1993, through February 28, 1994. INTERVENTIONS: Visual inspection of wrestlers before matches was instituted. Affected wrestlers were excluded from wrestling and advised to seek appropriate medical care. Heightened attention was given to personal and environmental hygiene. MAIN OUTCOME MEASURES: Colonization or infection with MRSA. RESULTS: Seven of 32 team members were MRSA positive (6 infected, 1 colonized). All lesion-positive wrestlers were tested by pulsed field gel electrophoresis and found to be infected with the same MRSA strain, as were 6 nonwrestlers. No risk factors for MRSA infection were identified. CONCLUSIONS: The MRSA was transmitted among members of a wrestling team. Infection with MRSA should be suspected in outbreaks of boils that are nonresponsive to standard antibiotic therapy among healthy participants of contact sports and their close contacts.

Progress in breast cancer screening: Vermont's efforts.

To impact Vermont's high breast cancer death rate, a statewide survey was conducted to identify barriers to screening. An awareness campaign was implemented that included community meetings, worksite education, television and radio ads, and physician education. A follow-up survey showed a significant increase in women ever having a mammogram and a significant decrease in women who felt that mammograms were not needed, the greatest identified barrier to screening. Despite increased awareness of breast cancer nationwide, it is likely that the education strategy successfully targeted and impacted women's behavior. Continued educational efforts are needed, particularly in women 50 and older.

Prevalence of lead poisoning among two-year-old children in Vermont.

OBJECTIVES: The recent redefinition of childhood lead poisoning by the Centers for Disease Control and Prevention means that many more children are considered lead poisoned than previously. The primary purpose of this study was to determine how many 2-year-old children had lead levels of 10 micrograms/dL or more in a rural state. METHODS: Random samples of 334 children drawn from the birth certificate file and 350 children from Vermont Medicaid rosters submitted capillary blood specimens that were confirmed by venous tests if lead levels were 10 micrograms/dL or more. RESULTS: Participation rates were 63.9% in the birth certificate group and 66.4% in the Medicaid group. In the birth certificate sample, the percentages of children with confirmed lead levels 10 micrograms/dL or more, 15 micrograms/dL or more, and 20 micrograms/dL or more were 9.0 (95% confidence interval [CI], 6.2-12.6), 2.7 (95% CI, 1.2-5.0), and 1.5 (95% CI, 0.5-3.4), respectively. In the Medicaid sample, the corresponding percentages were 14.9 (95% CI, 11.4-19.2), 5.1 (95% CI, 3.1-8.0), and 2.0 (95% CI, 0.8-4.1), respectively. The percentage of children in the state's most urban county with lead levels of 10 micrograms/dL or more was significantly less than that in the rest of the state in both samples. CONCLUSIONS: The prevalence of elevated lead levels in 2-year-old children may be significant in rural states with old housing stock. Medicaid-enrolled children represent a readily identifiable high-risk group.

Inhibition of lymphocyte nucleic acid metabolism and antibody production by trimetrexate.

Trimetrexate is a lipid soluble dihydrofolate reductase inhibitor which, unlike methotrexate, does not depend upon the membrane folate transport system for cell entry. We investigated the possibility that trimetrexate (but not methotrexate) might permeate intermitotic lymphocytes and, following stimulation, impair only the responding cells, rather than all dividing cells, as is the case with methotrexate. Peripheral blood mononuclear cells from normal individuals were incubated for 1 hr in three moderate to high concentrations (1, 10 and 100 microM) of methotrexate or trimetrexate, washed, and incubated with phytohemagglutinin. Intracellular folate activity, as assessed by the deoxyuridine suppression test, was abnormal at all three concentrations of trimetrexate but only at the highest concentration of methotrexate. Similarly, incorporation of [3H]deoxyuridine was depressed profoundly in trimetrexate-treated cells (2% of control) but unaffected by methotrexate. Analysis of cell cycle distribution by flow cytometry confirmed G0 + G1 arrest in trimetrexate but not methotrexate-treated cells. Neither drug altered morphologic transformation, Tac antigen expression, or incorporation of [3H]thymidine by the "salvage" pathway. Therefore, brief exposure to methotrexate has little effect on intermitotic lymphocytes, whereas trimetrexate very specifically inhibits the conversion of deoxyuridine to thymidine in these cells and leads to the arrest of DNA synthesis in the G0 + G1 phase. This metabolic abnormality markedly reduces in vitro antibody synthesis: a 1-hr treatment of lymphocytes with 10 or 100 microM trimetrexate prior to incubation with pokeweed mitogen on four occasions completely inhibited both IgG and IgM secretion. Similar treatment with methotrexate had no effect until the highest concentration (100 microM) was used. We conclude that brief exposure of peripheral blood mononuclear cells to the nonclassical dihydrofolate reductase inhibitor, trimetrexate, results in inhibition of nucleic acid synthesis and impairment of antibody production. This drug effect may permit more incisive modulation of immune responses.