Atrial fibrillation/flutter induced by implantable ventricular defibrillator shocks: difference between epicardial and endocardial energy delivery

INTRODUCTION

We evaluated the incidence and energy dependence of atrial fibrillation/flutter (AF) induced by implantable ventricular defibrillator shocks in 63 patients tested in the operating room or electrophysiology laboratory.

METHODS AND RESULTS

Defibrillator shocks were epicardial monophasic in 32 patients, and through an Endotak lead endocardial monophasic in 19 and biphasic in 12 patients. The epicardial and endocardial patient groups had similar clinical characteristics. A total of 517 defibrillator shocks were given. The epicardial group received 336 total defibrillator shocks and 10 +/- 6 shocks (mean +/- SD) per patient compared with the endocardial group, which received 181 total shocks and 6 +/- 4 defibrillator shocks per patient (P = 0.004). In the epicardial group, AF occurred in 13 (41%) patients and in 17 (5%) of the 336 shocks. No AF was induced with endocardial defibrillator shocks. The epicardial mean energy was 16 +/- 9 J, lower than the endocardial mean energy of 20 +/- 9 J (P < 0.004). In the epicardial monophasic group, energy correlated with AF induction. Each patient received 7 +/- 6 defibrillator shocks < 15 J and 4 +/- 2 shocks > or = 15 J, yet AF occurred in only 2.3% versus 9.6% (P < 0.05) of defibrillator shocks < 15 J and > or = 15 J, respectively. Of note, AF was not induced with energy < 4 J or > 31 J.

CONCLUSIONS

In the epicardial configuration, AF induction is energy dependent, with an apparent lower and upper limit of vulnerability. AF induction by defibrillator shocks delivered through an Endotak lead is very rare, possibly related to an apparent upper limit of vulnerability of less energy, avoidance of thoracotomy, or different energy field distribution.

Differential responses of glycogen synthase to ischaemia and ischaemic contraction in human skeletal muscle

The importance of metabolic changes associated with contraction in the activation of glycogen synthase (GS) during recovery from exercise in human skeletal muscle has been investigated. Subjects underwent two experimental treatments: 15 s of ischaemic isometric contraction at 66% of maximal force, and 40 min circulatory occlusion. Biopsies were taken from the quadriceps femoris muscle at rest, at the end of each treatment, and 5 min post-treatment. The decreases in phosphocreatine (approximately 50%), and increases in glucose 6-phosphate (approximately 3-fold) and lactate (approximately 8-fold) were similar during contraction and occlusion, indicating similar degrees of anaerobic ATP turnover and glycogen breakdown. Glycogen breakdown during each treatment was estimated to correspond to < 5% of the basal muscle glycogen content. GS fractional activity decreased approximately 10% after contraction and approximately 30% after occlusion (P < 0.05 vs. contraction). During recovery from contraction, GS fractional activity increased to 20% above the rest value, whereas no further change occurred during recovery from occlusion (P < 0.001 vs. recovery from contraction). These data demonstrate that the increase in GS fractional activity during recovery from isometric contraction does not require significant glycogen breakdown during the contraction, and is not a consequence of the measured metabolic changes associated with the contraction.

Loss of primitive hematopoietic progenitors in patients with human immunodeficiency virus infection

A number of hematologic abnormalities, including cytopenias, have been observed in patients with human immunodeficiency virus (HIV) infection. To elucidate their mechanisms, primitive cells from bone marrow aspirates of 21 patients with HIV-1 infection were quantitated by flow cytometry. The mean percentage of CD34+ cells is not significantly altered in HIV-1-infected patients in comparison with HIV-1-seronegative controls. In contrast, two- and three-color immunofluorescence analysis showed that in all HIV-1 samples, most CD34+ cells coexpressed the CD38 antigen. The proportion of HIV-1-derived CD34+ cells that did not express the CD38 antigen was significantly lower (HIV-1+: mean, 1.73%; controls: mean, 14%; P < .0005) than in controls. Moreover, of Thy-1+ cells, the proportion of CD34+ cells was twofold lower in HIV-1-infected patients (HIV-1+: mean, 12%; controls, 25%, P < .0005), which suggests that phenotypically primitive cells are depleted in HIV-1 infection. In vitro functional analysis in long-term cultures of sorted CD34+ cells from seven HIV-1 patients showed that CD34+ cells from HIV-1 patients generated much fewer colonies both in the nonadherent and adherent layers than CD34+ cells from controls after 5 weeks of culture (10-fold and four-fold less, respectively). Precise long-term culture initiating cell (LTC-IC) frequency in the CD34+ cell population was determined in three patients by limiting dilution and was markedly decreased in comparison to that of normal controls (from twofold to > sevenfold decreased). To determine if primitive cells were infected by HIV-1, both methylcellulose colonies generated from long-term culture of CD34+ cells and various CD34+ cell fractions purified by flow cytometry were evaluated for the presence of HIV-1 by polymerase chain reaction (PCR). Progeny from long-term culture was HIV-1-negative in three samples. In addition, using a sensitive PCR technique, the HIV-1 genome could not be detected in CD34+, CD34+/CD38-, and CD34+/CD4+ cells. These data show that hematologic disorders in HIV disease may be the consequence of a deficit of primitive cells. However, direct infection of these cells by HIV-1 does not seem to be responsible for this defect.

Aspergillosis in systemic lupus erythematosus

Infection is the major cause of morbidity and mortality in systemic lupus erythematosus (SLE). Although various fungi account for a substantial number of these lethal infections, aspergillosis, an important opportunistic infection in immunosuppressed patients, is described rarely. Only 23 cases have been reported in the English-language medical literature. Risk factors for acquiring aspergillosis in these patients were high grade disease activity, granulocytopenia, use of steroids and other immunosuppressive treatment and presence of bacterial infection. The diagnosis in most patients was delayed and they died. Here, we describe three SLE patients with invasive aspergillosis. Features of our patients' diseases were similar to those reported previously. Aspergillosis appeared while they had active SLE treated with high dose corticosteroids. In 2 patients the fungal infection was systemic and diagnosed post mortem. Both were leukopenic and had concurrent bacterial infection and one received amphotericin B prior to death. In the third, the infection was localized to a transplanted kidney and was cured by nephrectomy. Aspergillosis should be suspected in patients with active SLE, who are immunocompromised and sustain concomitant bacterial infections. The currently poor prognosis may be improved with more aggressive diagnostic investigation and treatment.

Merkel cell carcinoma in Israel

Merkel cell carcinoma is a rare and highly malignant skin tumor. We present the first report on the clinical and epidemiologic characteristics of Merkel cell carcinoma in Israel. Our findings, including average age of 69 years at diagnosis, equal sex distribution, disease location on sun-exposed skin, and an overall 3 year survival of 58%, are consistent with the data reported in the literature. Unique findings in our study were the predominance of Ashkenazic Jews and the excessive rate of second malignancies. This initial report on Merkel cell carcinoma in Israel emphasizes the need for increased awareness of this aggressive and potentially lethal skin malignancy.

Phenotype and function of human hematopoietic cells engrafting immune-deficient CB17-severe combined immunodeficiency mice and nonobese diabetic-severe combined immunodeficiency mice after transplantation of human cord blood mononuclear cells

In an attempt to understand better the regulation of stem cell function in chimeric immunodeficient mice transplanted with human cells, and the filiation between progenitor cells identified in vitro and in vivo, we assessed the different compartments of hematopoietic progenitors found in the marrow of CB17-severe combined immunodeficiency (SCID) mice (34 mice, 9 experiments) after intravenous injection of 2 to 3 x 10(7) cord blood mononuclear cells. On average 6.3 +/- 4 x 10(5) human cells were detected per four long bones 4 to 6 weeks after the transplant predominantly represented by granulomonocytic (CD11b+) and B lymphoid (CD19+) cells. Twenty five percent of these human cells expressed the CD34 antigen, of which 90% coexpressed the CD38 antigen and 50% the CD19 antigen. Functional assessment of progenitor cells (both clonogenic and long-term culture-initiating cells [LTC-IC]) was performed after human CD34+ cells and CD34+/CD38- cells have been sorted from chimeric CB17-SCID marrow 3 to 10 weeks after intravenous (IV) injection of human cells. The frequency of both colony-forming cells and LTC-IC was low (4% and 0.4%, respectively in the CD34+ fraction) when compared with the frequencies of cells with similar function in CD34+ cells from the starting cord blood mononuclear cells (26% +/- 7% and 7.2% +/- 5%, respectively). More surprisingly, the frequency of LTC-IC was also low in the human CD34+ CD38- fraction sorted from chimeric mice. This observation might be partly accounted for by the expansion of the CD34+ CD19+ B-cell precursor compartment. Despite their decreased frequency and absolute numbers, the differentiation capability of these LTC-IC, assessed by their clonogenic progeny output after 5 weeks in coculture with murine stromal cells was intact when compared with that of input LTC-IC. Furthermore the ratio between clonogenic progenitor cells and LTC-IC was similar in severe combined immunodeficiency (SCID) mice studied 4 weeks after transplant and in adult marrow or cord blood suspensions. Results generated in experiments where nonobese diabetic (NOD)-SCID mice were used as recipients indicate a higher level of engraftment but no change in the distribution of clonogenic cells or LTC-IC. These results suggest that the hierarchy of hematopoietic differentiation classically defined in human hematopoietic tissues can be reconstituted in immunodeficient SCID or NOD-SCID mice.

Electronic apex locator: a useful tool for root canal treatment in the primary dentition

The purpose of this study was to test the ability of an electronic apex locator, Root ZX to measure the root canal length in primary teeth with partial resorption. Twenty extracted primary molars were embedded in an alginate model imitating in vivo conditions. Root ZX and radiographic measurements were compared in dry and wet environments to the actual tooth length. Root ZX identified the tooth length at the most coronal portion of the resorption. The content of the root canal did not influence the results. No statistical differences were found between electronic, radiographic and actual tooth length measurements, although the radiographic measurements were longer than the electronic ones. It is suggested that Root ZX is a preferable auxiliary device to measure root canal length in the primary dentition.

Single lead VDD pacing: multicenter study

Optimal treatment for patients with AV block and normal sinoatrial node (SA) function entails atrial sensing and ventricular pacing (VDD mode). Single-lead VDD pacing preserves AV synchrony, precludes the need to insert two leads, and makes the implanter's work simpler and quicker. Our objectives were to verify the performance of the Thera VDD pacing system (medtronic, Inc., Minneapolis, MN, USA), and evaluate the effectiveness of its atrial sensing and its ventricular sensing and pacing. In 165 patients, 150 adults (mean age 62 +/- 18 years) and 15 children (mean age 7 +/- 5 years) with 1 degree-3 degrees AV block and normal SA node function, a Thera VDD system (Models 8948 or 8968) was implanted. Intraoperative ventricular electrical measurements were not significantly different from those of VVI pacemakers. The mean amplitude of the atrial signal during implantation was 4.1 +/- 1.9 mV. Optimal atrial signals during implantation were usually obtained in the mid or lower part of the right atrium by using a special technique. Adequate atrial measurements remained stable throughout 24 months. There was no difference between serial measurements of atrial signal amplitudes at predischarge and during follow-up visits. Reposition of the lead was done in 2 patients (1.4%), and reprogramming to VVI in 7 patients: due to atrial fibrillation in 3 (1.8%) and due to atrial undersensing in 4 patients (2.4%). Thera VDD pacing is reliable and easy to manage with dependable atrial sensing and ventricular pacing. The survival rate of VDD pacing at 2 years was 96%.

[Indapamide--a substitute diuretic for hypertensives with hyperglycemia and/or dyslipidemia]

Diuretics are among the first drugs offered to the hypertensive patient. However, they can induce metabolic changes resulting in cardiovascular insult. Especially noteworthy are increased levels of glucose and lipids. Indapamide is a diuretic and vasodilator that does not raise blood glucose or lipid levels. We therefore investigated its use as a substitute diuretic in patients whose treatment had resulted in hyperglycemia and/or hyperlipidemia. In 24 hypertensives, Indapamide, 2.5 mg daily, replaced the diuretic therapy they were receiving. Blood pressure, blood glucose, hemoglobin A1C and lipid profile were measured before and every month during the 6 months of Indapamide treatment. Replacement of diuretics with Indapamide significantly reduced blood glucose from 148 +/- 53 mg/dl to 127 +/- 37, p = 0.05 HbA1C from 8.42 +/- 0.4 mg/dl to 7.7 +/- 2.0, p = 0.05; total cholesterol from 253 +/- 45 mg/dl to 228 +/- 43, p < 0.05; and triglycerides from 224 +/- 145 mg/dl to 176 +/- 91, p < 0.05. Blood pressure was better controlled with Indapamide than with previous medications. It was reduced from an average of 155 +/- 1 systolic and 89 +/- 8 diastolic (mm Hg), to 142 +/- 13 and 83 +/- 7, respectively, p < 0.05. We conclude that Indapamide is safe and effective in lowering blood pressure and contributes to better control of blood glucose and lipid levels in diabetic and dyslipidemic patients, compared to standard diuretics.

No change in insulin mediators in human skeletal muscle during isometric contraction or recovery

The rapid activation of glycogen synthase in human skeletal muscle during recovery from isometric contraction is dependent on an intact circulation, which suggests the requirement of an activating humoral factor. To determine whether the activating factor is insulin, muscle biopsies were obtained from subjects at rest, at fatigue, 3 min postexercise with an intact circulation, and 3 min postexercise during which circulation to the muscle was occluded. Two inositol phosphoglycan mediators of insulin action were isolated from the biopsies, and bioactivity was measured by determining the effects of the isolated mediators on the activities of purified cyclic AMP-dependent protein kinase, pyruvate dehydrogenase phosphatase and glycogen synthase phosphatase in vitro. Bioactivity was not altered by any condition compared with rest. These data suggest that changes in inositol phosphoglycans are not responsible for the circulation-dependent activation of glycogen synthase during recovery from exercise.

Intact glucose transport in morphologically altered denervated skeletal muscle from quadriplegic patients

The present study was undertaken to investigate the nature of the whole body insulin resistance that characterizes patients with complete cervical spinal cord lesion. Nine patients with C5-C7 lesions and ten age-matched healthy individuals were studied. Whole body insulin-mediated glucose utilization was reduced by 43% in the quadriplegic patients compared with the controls (P < 0.001). In the quadriplegic patients, lean body mass corresponded to 66 +/- 3% of total body mass. Despite whole body insulin resistance, in isolated vastus lateralis muscle, basal and insulin-stimulated 3-O-methylglucose transport, as well as protein expression of the insulin or exercise-regulatable glucose transporter, GLUT-4, and glycogen content were comparable between the patients and controls. Strikingly, muscle fiber area was reduced by 44% (P < 0.05), percentage of type IIb fibers was increased (P < 0.01), and there was a complete loss of type I fibers in the patients. In conclusion, the dissociation between whole body insulin-mediated glucose uptake and skeletal muscle glucose transport in quadriplegic patients primarily reflects the decreased muscle mass. Furthermore, these findings demonstrate a remarkable capacity of skeletal muscle to maintain an intact glucose transport system despite severe morphological alterations.

Felodipine in the treatment of severe refractory hypertension

The efficacy of felodipine and tolerance of this drug was examined in 52 patients, 23 men and 29 women, 18-76 years of age, in whom it either replaced previous therapies of nifedipine and other vasodilators, or was added to a constant dose of beta blockers and diuretics or another previous therapy, which was unchanged. Felodipine significantly reduced blood pressure (BP), from 192.3 +/- 31.9/114.3 +/- 18.0 to 155.7 +/- 19.5/93.8 +/- 11.5 mm Hg, with no change in pulse rate. There were no significant biochemical changes, renal deterioration or blood sugar disequilibrium. Adverse reactions including flushes and leg edema could be tolerated by most of the patients, however six patients dropped out. Orthostasis dictated a decrease in felodipine dosage. Felodipine appears to be a highly potent, well tolerated drug and offers a substitute treatment for severe hypertensives refractory to other vasodilators.

Characterization of a bipotent erythro-megakaryocytic progenitor in human bone marrow

The aim of the present study was to determine if the human erythroid (E) and megakaryocytic (MK) lineages were closely linked to the existence of a bipotent burst-forming unit (BFU) E/MK progenitor. In methylcellulose cultures, BFU-E/MK colonies were observed at day 12 and closely resembled mature BFU-E with the exception that the erythroid component was surrounded by MK. These colonies were quite different from the colony forming unit (CFU)-GEMM-derived colonies, which were composed of a larger number of erythroblasts and which developed later in culture. The existence of these bilineage colonies composed of 100 to 1,000 erythroblasts intermingled with a few MK and without granulocytic cells was confirmed by the plasma clot technique and immunoalkaline phosphatase labeling of the MK. To investigate if this bipotent progenitor belonged to the compartment of primitive progenitors, CD34+ marrow cells were subfractionated according to expression of the CD38 antigen. The bipotent BFU-E/MK progenitor as well as a large fraction of MK progenitors were found in the CD34+ CD38+/- or in the CD34+ CD38- cell fractions. Growth of this bipotent BFU-E/MK progenitor required the combination of stem cell factor (SCF), Interleukin-3 (IL-3), and Epo in serum free conditions. Addition of IL-6 had only a marginal effect, whereas megakaryocyte growth and development factor (MGDF) was not an absolute requirement, but slightly increased the plating efficiency of CFU-MK and of BFU-E/MK progenitors when combined with SCF, IL-3, and Epo. In contrast, when these cultures were performed in the presence of 30% fetal calf serum, no BFU-E/MK colonies were observed irrespective of the combination of growth factors used, including the presence of MGDF; however, inclusion of the MS-5 cell line restored the growth of this bipotent progenitor. In contrast, in cultures performed in the presence of human normal or aplastic plasma, MS-5 had only a slight effect on the cloning efficiency but improved MK cytoplasmic maturation and MK size, suggesting that the main effect of MS-5 is to diminish the inhibitory effect of the fetal calf serum on the MK differentiation. The clonal origin of bipotent BFU-E/MK colonies was demonstrated in liquid culture of single CD34+ CD38low cells by immunophenotyping individual clones. At day 12, 30% of the clones contained erythroblasts (glycophorin A+) and some MK (CD41+) without granulocytes (G) or macrophages (M) (CD14+ and CD15+). At day 20, clones containing erythroblasts and MK were rare (5%). In contrast multilineage clones could be frequently detected at this time without passage from BFU-E/MK clones at day 12 to GEMM at day 20. These results suggest that a bipotent BFU-E/MK progenitor may be a nonrandom step in the hierarchical development of stem cells.

The outcome of patients with acute myocardial infarction ineligible for thrombolytic therapy. Israeli Thrombolytic Survey Group

PURPOSE

The aim of this study was to determine the proportion of patients with acute myocardial infarction (AMI) excluded from thrombolytic therapy on a national basis and to evaluate the prognosis of these patients by reasons of ineligibility and according to the alternative therapies that they received during hospitalization.

PATIENTS AND METHODS

During a national survey, 1,014 consecutive patients with AMI were hospitalized in all the 25 coronary care units operating in Israel.

RESULTS

Three hundred and eighty-three patients (38%) were treated with a thrombolytic agent and included in the GUSTO study. Ineligible patients for GUSTO were treated: (1) without any reperfusion therapy (n = 449), (2) by mechanical revascularization (n = 97), or (3) given 1.5 million units of streptokinase (n = 85) outside of the GUSTO protocol. The inhospital and 1-year post-discharge mortality rates were 6% and 2% in patients included in the GUSTO study; 6% and 5% in those mechanically reperfused; 15% and 10% in those treated with thromoblysis despite ineligibility for the GUSTO trial, and 15% and 13% among patients not treated with any reperfusion therapy.

CONCLUSIONS

Ineligibility for thrombolysis among patients with AMI remains high. Patients ineligible for thrombolysis according to the GUSTO criteria, but nevertheless treated with a thrombolytic agent were exposed to an increased risk.

Gaining a new perspective on life as a consequence of uncertainty in HIV infection

HIV infection affects the lives of hundreds of thousands of North Americans. The experience of those infected is one of enormous upheaval. An HIV diagnosis can disrupt both daily life and the ability to plan for the future. Central to this experience is the uncertainty of a disease with vague symptomatology, changing medical management, and social stigma. This qualitative study explores the experience and consequences of uncertainty in the lives of 10 people with HIV infection. In-depth focused interviews were conducted to explore uncertainty after HIV diagnosis. Findings reveal that individuals living with HIV infection form a new perspective on life, which is maintained through five core experiences: surviving the HIV diagnosis, taking care, living in the present, seeking support, and appreciating the positive. Each core experience is comprised of a number of actions used by the individual to formulate and maintain the new perspective on life.

Cryocrystalglobulinemia mimicking rheumatoid arthritis and vasculitis

We describe a patient with longstanding arthropathy resembling rheumatoid arthritis (RA) and cold induced purpura for many years, concomitant with IgG kappa paraproteinemia. At autopsy, the patient was found to have evidence of widespread vascular occlusions due to precipitated crystals as well as tissue deposition of crystals. Neither vasculitis nor synovitis was observed despite the clinical picture of both. Blood and synovial fluid obtained antemortem were found to spontaneously form crystals when stored at 4 degrees C, and the washed crystals were composed of the same monoclonal IgG kappa previously found in serum. Cryocrystal formation occurred at 33 degrees C and neutral pH. This patient thus had cryocrystalglobulinemia mimicking clinical manifestations of RA and vasculitis.

Focal bacterial nephritis (lobar nephronia) in children

We report 13 patients with 16 episodes of acute lobar nephronia diagnosed in a prospective study that was conducted among 210 hospitalized children with urinary tract infection. In 30 episodes of urinary tract infection, a hypoechogenic or hyperechogenic lesion was found. Twenty patients underwent computed tomography, and in 16 of them acute lobar nephronia was diagnosed. Evolution to renal abscess occurred in 25%. Prolonged intravenous antibiotic treatment was sufficient in all cases.

Augmented force output in skeletal muscle fibres of Xenopus following a preceding bout of activity

1. The effect of a brief period of activity on subsequent isometric tetanic force production was investigated in single muscle fibres of Xenopus laevis. 2. Following a train of ten tetani separated by 4 s intervals, tetanic force was significantly augmented by about 10%. The tetanic force augmentation persisted for at least 15 min and then slowly subsided. A similar potentiation was seen following trains of five and twenty tetani. 3. During the period of tetanic force potentiation, tetanic calcium was reduced by more than 30%, and intracellular pH was reduced from 7.15 +/- 0.07 to 7.03 +/- 0.11 (n = 4). 4. Fibre swelling was greatest at 1 min and then subsided over 15-20 min and possibly accounted for a small part of the observed force potentiation. 5. A reduction in the inorganic phosphate (P1) concentration of more than 40% was found in fibres frozen in liquid nitrogen at the peak of force potentiation compared with resting fibres. 6. It is concluded that the augmentation of tetanic force found after a brief preceding bout of activity is due to a reduction in inorganic phosphate. This mechanism may underlie the improved performance observed in athletes after warm-up.

Mutations in a C. elegans Gqalpha gene disrupt movement, egg laying, and viability

We find that C. elegans egl-30 encodes a heterotrimeric G protein a subunit more than 80% identical to mammalian Gqalpha family proteins, and which can function as a Gqalpha subunit in COS-7 cells. We have identified new egl-30 alleles in a selection for genes involved in the C. elegans acetylcholine response. Two egl-30 alleles specify premature termination of Gqalpha and are essentially lethal in homozygotes. Animals homozygous for six other egl-30 alleles are viable and fertile, but exhibit delayed egg laying and leave flattened tracks. Overexpression of the wild-type egl-30 gene produces the opposite behavior. Analysis of these mutants suggest that their phenotypes reflect defects in the muscle or neuromuscular junction.