Myopotential Interference Inducing Pacemaker Tachycardia in a DVI Programmed Pacemaker

A 67-year-old male, suffering from ventricular tachycardia unresponsive to drug therapy, received a universal AV sequential pacemaker (DDD,M). Tim pacemaker was programmed in the DVI mode, pacing role 100 bpm, AV interval 250 ms. After implantation, the patient experiences two episodes of tachycardia that proved to be pacemaker tachycardia with a rate of 150 bpm. The first period was self-terminating, and the second had to be stopped by reprogramming the pulse generator. Pacemaker tachycardia could easily be provoked by instructing the patient to contract the pectoral muscle adjacent to the pulse generator. To our knowledge, this is the first report to pacemaker tachycardia provoked by myopotentials in a pulse generator programmed in the DVI mode.     

Enhancement of t lymphocyte functions by Fc fragments of immunoglobulins. I. Augmentation of allogeneic mixed lymphocyte culture reactions requires I-A- or I-B-subregion differences between effector and stimulator cell populations

Fc fragments derived from human Ig were found to be capable of enhancing T cell-mediated, antigen-induced proliferative and mixed lymphocyte culture responses. Maximum enhancement occurred when suboptimal amounts of antigen or suboptimal numbers of stimulator cells were employed. Augmentation of the allogeneic mixed lymphocyte culture reaction requires an I-A and/or I-B subregion difference between effector and stimulator cell populations. Although a significant proliferative response was observed with K- or D- region differences, Fc fragments were unable to enhance the response. The T cell population acted upon by Fc fragments in the potentiation of these responses bears the Lyt-1(+)23(-) phenotype.     

Seroprevalence of human T-lymphotropic virus, hepatitis C virus, and human immunodeficiency virus in Asian American potential bone marrow donors

BACKGROUND: Asian Americans are generally underrepresented both as volunteer blood and bone marrow donors. STUDY DESIGN AND METHODS: To investigate the risk of transfusion transmission of viruses that is associated with increasing participation by Asian American donors, antibodies to human T-lymphotropic virus (HTLV), hepatitis C, and human immunodeficiency virus in Asian American volunteers recruited as potential bone marrow donors were measured. A total of 1354 Asian Americans were enrolled in the study, of whom 54 percent were Chinese, 26 percent Japanese, 9 percent Filipino, 4 percent Korean, 3 percent Indian, and 5 percent of other Asian or mixed Asian and other ethnicity. The majority of the study population was aged 20 through 49 and of high socioeconomic status, as indicated by education and income. Viral antibodies were measured with both screening enzyme-linked immunosorbent assays and supplemental testing, and polymerase chain reaction was used to resolve discrepant HTLV results. RESULTS: Confirmed seroprevalence rates for HTLV were 0.15 percent with one manufacturer's Western blot and 0.3 percent with the other; however, no sample was positive for HTLV types I or II in polymerase chain reaction. Confirmed seroprevalence to hepatitis C virus was 0.5 percent. No subject was seropositive for human immunodeficiency virus. CONCLUSION: On the basis of the moderate size and high education level of this study population, it is concluded that Asian American volunteer bone marrow donors do not pose a greater risk for transmission of HTLV type I or II, human immunodeficiency virus, or hepatitis C virus than does the average American blood donor.     

Fusion or Confusion on Holter Recording

Holter recording of a patient with an implanted dual chamber rate responsive pacemaker revealed an electrocardiogram, where ventricular depolarization seemed to be initiated by the atrial stimulus. In a second patient with a VVI pacemaker, Holter recording showed delay of the pacemaker impulse that was registered after the onset of ventricular depolarization. Misalignment in one of the recorder heads of the display system was responsible for this phenomenon, which in case of dual chamber pacing could have been easily misinterpreted as pacemaker malfunction.     

Cytokine generation in stored platelet concentrates

BACKGROUND: Cytokines, because of the nature of their immunoinflammatory actions, are potential mediators of the symptom complex of nonhemolytic transfusion reactions. One possible source of cytokines in the transfusion setting is the stored blood component itself. STUDY DESIGN AND METHODS: To test this possibility, the plasma portion of stored platelet concentrates (PCs) was assayed for the presence of interleukins 1 beta (IL-1 beta), 6 (IL-6), and 8 (IL-8) and tumor necrosis factor alpha (TNF-alpha). Samples were taken from PCs obtained from the inventory of a regional blood center (n = 120; 30 each of 2-, 3-, 4-, and 5-day-old units). RESULTS: Detectable levels of IL-8 were measured in 59 percent of the PCs sampled, ranging from 30 percent of the 2-day-old units to 83 percent of the 5-day-old units. The median IL-8 concentration ranged from undetectable levels in 2-day- old units up to 1100 pg per mL in 5-day-old units. The mean IL-8 concentration in 5-day-old units, 11,600 pg per mL, was 100 times the mean for 2-day-old units, which was 116 pg per mL (p < 0.0001). The highest levels of IL-8, 50,000 to 200,000 pg per mL, in general were found in units with the longest storage times and highest white cell counts. Sequential sampling of 17 individual PCs over 7 days of storage confirmed that IL-8 increases progressively with increasing storage time. Parallel, but smaller, increases in IL-1 beta were observed in those units with high IL-8 concentrations. TNF-alpha was detected in 3 (10%) of 30 five-day-old PCs, but never exceeded 55 pg per mL in any unit tested. IL-6 at levels of 740 and 508 pg per mL was detected in two 5-day-old units with high white cell counts of 9500 and 14,800 per microL, respectively, but not in 21 additional units tested with white cells < or = 9200 per microL or storage time of < or = 2 days. White cell reduction by third-generation filters on Day 1 of platelet storage prevented the generation of IL-8 and IL-1 beta to Day 5 of storage. CONCLUSION: Although IL-8 achieved levels in some units of PCs that appear capable of causing physiologic changes, the potential adverse effect on transfusion recipients of the infusion of cytokines in PCs remains to be investigated.     

The effect of solvent/detergent-treated plasma on red cells stored in vitro

BACKGROUND: The potential use of solvent/detergent-treated plasma (S/D plasma) in transfusion practice raises concerns about the cytolytic effects that any residual solvent and detergent in the virally inactivated blood component might have on units of red cells in vitro, if the two components are mixed during preparation. STUDY DESIGN AND METHODS: S/D plasma was mixed with variously processed units of stored red cells, in vitro, to evaluate the effect the residual solvent and detergent would have on cell membrane integrity. A paired protocol design was used in which half-units of red cells were exposed to S/D plasma (test), and the matched half-units were exposed to either the supernatant additive solution from the original red cell unit or standard fresh-frozen plasma (FFP) (control). After incubation for up to 5 days, the units were evaluated for evidence of hemolysis or changes in other red cell storage assays. RESULTS: This study showed that, for fresh additive solution red cells (AS-1), the 5-day storage plasma hemoglobin levels were comparable in the red cells exposed to S/D plasma (21 mg/dL) and in the paired half-units stored in the original AS-1 supernatant (31 mg/dL) (p > 0.05). Similar findings were recorded for stored AS-1 red cells (S/D plasma; 111 mg/dL vs. AS-1 supernatant, 147 mg/dL; p > 0.05); stored CPDA-1 red cells (S/D plasma, 133 mg/dL vs. FFP, 103 mg/dL; p > 0.05); frozen red cells (S/D plasma, 28 mg/dL vs. FFP, 18 mg/dL; p > 0.017); and stored irradiated AS-1 red cells (S/D plasma, 608 mg/dL vs. AS-1 supernatant, 726 mg/dL; p > 0.05). Comparable results were found for other assays, including levels of plasma potassium, osmotic fragility, and red cell antigen titer. CONCLUSION: These data show that S/D plasma does not induce red cell lysis even after 5 days of in vitro storage. These results are consistent with previous findings by this laboratory that platelets are not harmed by storage in S/D plasma. Red cells resuspended in S/D plasma and stored for up to 5 days maintain in vitro storage characteristics that are acceptable for the use of the cells in clinical transfusion practice.     

Detection of human anti-HTLV-III antibodies by indirect immunofluorescence using fixed cells

Seropositivity to human T-cell lymphotrophic virus-III (HTLV-III) can have profound implications for the individual in whom it is detected. Simple and reliable tests are needed to confirm positivity by screening assays. In this study, detection of human antibodies by indirect immunofluorescence (IFA) on acetone-fixed HTLV-III infected H9 cells was evaluated in blood donors, patients with infectious or auto-immune diseases, and men with or at high risk for developing acquired immune deficiency syndrome (AIDS). Specific and nonspecific patterns of immunofluorescent reactivity were distinguished easily. None of 98 serums from blood donors was positive, while two of 33 serums from patients attending an infectious disease clinic, both homosexual men, were positive. Ninety-six percent of 24 serums from men with AIDS, 87 percent of 70 serums from men with lymphadenopathy, and 50 percent of 135 serums from healthy gay men were positive. These results paralleled those obtained by Western blotting and membrane immunofluorescence. In contrast, 11 and 4 percent, respectively, of these serums were judged as borderline or not interpretable by an enzyme-linked immunosorbent assay (ELISA). Of these serums, those that were positive by IFA were positive by Western blots, and 16 of the 17 IFA-negative serums were negative by Western blots. These studies indicate that IFA is a sensitive and specific assay for HTLV-III antibodies in human serums.     

Long-Term Results of Hybrid Therapy in Patients with Atrial Fibrillation Who Develop Atrial Flutter During Flecainide Infusion

The flecainide infusion test has been proposed to screen candidates for hybrid pharmacological and ablation therapy. We report the long-term follow-up of 154 consecutive patients with paroxysmal or persistent atrial fibrillation (AF) who developed atrial flutter (AFL) during flecainide infusion (IC AFL), treated with inferior vena cava-tricuspid annulus isthmus catheter ablation and oral flecainide (hybrid therapy). Over a mean of 54.1 ± 13.1 months 82 patients (53%) remained free of AF and AFL. Flecainide was discontinued because of adverse effects in 6 patients (4%). A history of persistent AF, and the documentation of ≥1 spontaneous AFL episode before the flecainide test were independent predictors of successful hybrid therapy. In patients with paroxysmal AF without documented spontaneous AFL, the long-term efficacy of hybrid therapy was 38.5% (P = 0.03). The flecainide infusion test reliably detects candidates for hybrid therapy. The efficacy of this therapy is maintained over the long-term with a high patient compliance.