Interstitial macrophages are a focus of viral takeover and inflammation in COVID-19 initiation in human lung

Early stages of deadly respiratory diseases including COVID-19 are challenging to elucidate in humans. Here, we define cellular tropism and transcriptomic effects of SARS-CoV-2 virus by productively infecting healthy human lung tissue and using scRNA-seq to reconstruct the transcriptional program in "infection pseudotime" for individual lung cell types. SARS-CoV-2 predominantly infected activated interstitial macrophages (IMs), which can accumulate thousands of viral RNA molecules, taking over 60% of the cell transcriptome and forming dense viral RNA bodies while inducing host profibrotic (TGFB1, SPP1) and inflammatory (early interferon response, CCL2/7/8/13, CXCL10, and IL6/10) programs and destroying host cell architecture. Infected alveolar macrophages (AMs) showed none of these extreme responses. Spike-dependent viral entry into AMs used ACE2 and Sialoadhesin/CD169, whereas IM entry used DC-SIGN/CD209. These results identify activated IMs as a prominent site of viral takeover, the focus of inflammation and fibrosis, and suggest targeting CD209 to prevent early pathology in COVID-19 pneumonia. This approach can be generalized to any human lung infection and to evaluate therapeutics.

An organism-wide atlas of hormonal signaling based on the mouse lemur single-cell transcriptome

Hormones mediate long-range cell communication and play vital roles in physiology, metabolism, and health. Traditionally, endocrinologists have focused on one hormone or organ system at a time. Yet, hormone signaling by its very nature connects cells of different organs and involves crosstalk of different hormones. Here, we leverage the organism-wide single cell transcriptional atlas of a non-human primate, the mouse lemur (Microcebus murinus), to systematically map source and target cells for 84 classes of hormones. This work uncovers previously-uncharacterized sites of hormone regulation, and shows that the hormonal signaling network is densely connected, decentralized, and rich in feedback loops. Evolutionary comparisons of hormonal genes and their expression patterns show that mouse lemur better models human hormonal signaling than mouse, at both the genomic and transcriptomic levels, and reveal primate-specific rewiring of hormone-producing/target cells. This work complements the scale and resolution of classical endocrine studies and sheds light on primate hormone regulation.

The Tabula Sapiens: A multiple-organ, single-cell transcriptomic atlas of humans

Molecular characterization of cell types using single-cell transcriptome sequencing is revolutionizing cell biology and enabling new insights into the physiology of human organs. We created a human reference atlas comprising nearly 500,000 cells from 24 different tissues and organs, many from the same donor. This atlas enabled molecular characterization of more than 400 cell types, their distribution across tissues, and tissue-specific variation in gene expression. Using multiple tissues from a single donor enabled identification of the clonal distribution of T cells between tissues, identification of the tissue-specific mutation rate in B cells, and analysis of the cell cycle state and proliferative potential of shared cell types across tissues. Cell type-specific RNA splicing was discovered and analyzed across tissues within an individual.

Neuroendocrinology of the lung revealed by single-cell RNA sequencing

Pulmonary neuroendocrine cells (PNECs) are sensory epithelial cells that transmit airway status to the brain via sensory neurons and locally via calcitonin gene-related peptide (CGRP) and γ- aminobutyric acid (GABA). Several other neuropeptides and neurotransmitters have been detected in various species, but the number, targets, functions, and conservation of PNEC signals are largely unknown. We used scRNAseq to profile hundreds of the rare mouse and human PNECs. This revealed over 40 PNEC neuropeptide and peptide hormone genes, most cells expressing unique combinations of 5-18 genes. Peptides are packaged in separate vesicles, their release presumably regulated by the distinct, multimodal combinations of sensors we show are expressed by each PNEC. Expression of the peptide receptors predicts an array of local cell targets, and we show the new PNEC signal angiotensin directly activates one subtype of innervating sensory neuron. Many signals lack lung targets so may have endocrine activity like those of PNEC-derived carcinoid tumors. PNECs are an extraordinarily rich and diverse signaling hub rivaling the enteroendocrine system.

Tissue-specific telomere shortening and degenerative changes in a patient with TINF2 mutation and dyskeratosis congenita

Dyskeratosis congenita is a disease of impaired tissue maintenance downstream of telomere dysfunction. Characteristically, patients present with the clinical triad of nail dystrophy, oral leukoplakia, and skin pigmentation defects, but the disease involves degenerative changes in multiple organs. Mutations in telomere-binding proteins such as TINF2 (TRF1-interacting nuclear factor 2) or in telomerase, the enzyme that counteracts age related telomere shortening, are causative in dyskeratosis congenita. We present a patient who presented with severe hypoxemia at age 13. The patient had a history of myelodysplastic syndrome treated with bone marrow transplant at the age of 5. At age 18 she was hospitalized for an acute pneumonia progressing to respiratory failure, developed renal failure and ultimately, she and her family opted to withdraw support as she was not a candidate for a lung transplant. Sequencing of the patient's TINF2 locus revealed a heterozygous mutation (c.844C > T, Arg282Cys) which has previously been reported in a subset of dyskeratosis congenita patients. Tissue sections from multiple organs showed degenerative changes including disorganized bone remodeling, diffuse alveolar damage and small vessel proliferation in the lung, and hyperkeratosis with hyperpigmentation of the skin. Autopsy samples revealed a bimodal distribution of telomere length, with telomeres from donor hematopoietic tissues being an age-appropriate length and those from patient tissues showing pathogenic shortening, with the shortest telomeres in lung, liver, and kidney. We report for the first time a survey of degenerative changes and telomere lengths in multiple organs in a patient with dyskeratosis congenita.

Cell-autonomous immune gene expression is repressed in pulmonary neuroendocrine cells and small cell lung cancer

Small cell lung cancer (SCLC) is classified as a high-grade neuroendocrine (NE) tumor, but a subset of SCLC has been termed “variant” due to the loss of NE characteristics. In this study, we computed NE scores for patient-derived SCLC cell lines and xenografts, as well as human tumors. We aligned NE properties with transcription factor-defined molecular subtypes. Then we investigated the different immune phenotypes associated with high and low NE scores. We found repression of immune response genes as a shared feature between classic SCLC and pulmonary neuroendocrine cells of the healthy lung. With loss of NE fate, variant SCLC tumors regain cell-autonomous immune gene expression and exhibit higher tumor-immune interactions. Pan-cancer analysis revealed this NE lineage-specific immune phenotype in other cancers. Additionally, we observed MHC I re-expression in SCLC upon development of chemoresistance. These findings may help guide the design of treatment regimens in SCLC.

Ling Cai et al. used transcriptomic profiling data of healthy lung, patient-derived small cell lung cancer cell lines, xenografts, and primary tumors to examine a link between neuroendocrine (NE) signatures and immune gene expression. Their findings suggest that cell-autonomous immune gene repression is a shared feature between healthy and tumor cells of NE lineage and may influence tumor-immune cell interaction and response to immunotherapy.

Single-cell meta-analysis of SARS-CoV-2 entry genes across tissues and demographics

Angiotensin-converting enzyme 2 (ACE2) and accessory proteases (TMPRSS2 and CTSL) are needed for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) cellular entry, and their expression may shed light on viral tropism and impact across the body. We assessed the cell-type-specific expression of ACE2, TMPRSS2 and CTSL across 107 single-cell RNA-sequencing studies from different tissues. ACE2, TMPRSS2 and CTSL are coexpressed in specific subsets of respiratory epithelial cells in the nasal passages, airways and alveoli, and in cells from other organs associated with coronavirus disease 2019 (COVID-19) transmission or pathology. We performed a meta-analysis of 31 lung single-cell RNA-sequencing studies with 1,320,896 cells from 377 nasal, airway and lung parenchyma samples from 228 individuals. This revealed cell-type-specific associations of age, sex and smoking with expression levels of ACE2, TMPRSS2 and CTSL. Expression of entry factors increased with age and in males, including in airway secretory cells and alveolar type 2 cells. Expression programs shared by ACE2+TMPRSS2+ cells in nasal, lung and gut tissues included genes that may mediate viral entry, key immune functions and epithelial-macrophage cross-talk, such as genes involved in the interleukin-6, interleukin-1, tumor necrosis factor and complement pathways. Cell-type-specific expression patterns may contribute to the pathogenesis of COVID-19, and our work highlights putative molecular pathways for therapeutic intervention.

A molecular cell atlas of the human lung from single-cell RNA sequencing

Although single-cell RNA sequencing studies have begun to provide compendia of cell expression profiles1-9, it has been difficult to systematically identify and localize all molecular cell types in individual organs to create a full molecular cell atlas. Here, using droplet- and plate-based single-cell RNA sequencing of approximately 75,000 human cells across all lung tissue compartments and circulating blood, combined with a multi-pronged cell annotation approach, we create an extensive cell atlas of the human lung. We define the gene expression profiles and anatomical locations of 58 cell populations in the human lung, including 41 out of 45 previously known cell types and 14 previously unknown ones. This comprehensive molecular atlas identifies the biochemical functions of lung cells and the transcription factors and markers for making and monitoring them; defines the cell targets of circulating hormones and predicts local signalling interactions and immune cell homing; and identifies cell types that are directly affected by lung disease genes and respiratory viruses. By comparing human and mouse data, we identified 17 molecular cell types that have been gained or lost during lung evolution and others with substantially altered expression profiles, revealing extensive plasticity of cell types and cell-type-specific gene expression during organ evolution including expression switches between cell types. This atlas provides the molecular foundation for investigating how lung cell identities, functions and interactions are achieved in development and tissue engineering and altered in disease and evolution.

Rare Pulmonary Neuroendocrine Cells Are Stem Cells Regulated by Rb, p53, and Notch

Pulmonary neuroendocrine (NE) cells are neurosensory cells sparsely distributed throughout the bronchial epithelium, many in innervated clusters of 20-30 cells. Following lung injury, NE cells proliferate and generate other cell types to promote epithelial repair. Here, we show that only rare NE cells, typically 2-4 per cluster, function as stem cells. These fully differentiated cells display features of classical stem cells. Most proliferate (self-renew) following injury, and some migrate into the injured area. A week later, individual cells, often just one per cluster, lose NE identity (deprogram), transit amplify, and reprogram to other fates, creating large clonal repair patches. Small cell lung cancer (SCLC) tumor suppressors regulate the stem cells: Rb and p53 suppress self-renewal, whereas Notch marks the stem cells and initiates deprogramming and transit amplification. We propose that NE stem cells give rise to SCLC, and transformation results from constitutive activation of stem cell renewal and inhibition of deprogramming.

Axon-like protrusions promote small cell lung cancer migration and metastasis

Metastasis is the main cause of death in cancer patients but remains a poorly understood process. Small cell lung cancer (SCLC) is one of the most lethal and most metastatic cancer types. SCLC cells normally express neuroendocrine and neuronal gene programs but accumulating evidence indicates that these cancer cells become relatively more neuronal and less neuroendocrine as they gain the ability to metastasize. Here we show that mouse and human SCLC cells in culture and in vivo can grow cellular protrusions that resemble axons. The formation of these protrusions is controlled by multiple neuronal factors implicated in axonogenesis, axon guidance, and neuroblast migration. Disruption of these axon-like protrusions impairs cell migration in culture and inhibits metastatic ability in vivo. The co-option of developmental neuronal programs is a novel molecular and cellular mechanism that contributes to the high metastatic ability of SCLC.

P1585Increased circulating galectin 1 level is associated with progression of kidney function decline in patients with suspected coronary artery disease, independent of diabetes

Background

Galectin-1 modulates acute and chronic inflammation, and is associated with glucose homeostasis and chronic renal disease. Whether serum Galectin-1 levels could predict the short-term and long-term renal outcomes after contrast exposure in patients with suspected coronary artery disease remains uncertain.

Purpose

This study aimed to evaluate the relationship between serum Galectin-1 levels and the incidence of contrast-induced nephropathy and to investigate the predictive role of circulating galectin-1 levels in renal function decline in patients undergoing coronary angiography.

Methods

In total, 798 patients who had received coronary angiography were enrolled. Serum galectin-1 levels were determined before administration of contrast media. Contrast-induced nephropathy was defined as a rise in serum creatinine of 0.5 mg/dL or a 25% increase from baseline within 48 h after the procedure. Progressive renal function decline was defined as >30% decrease in estimated glomerular filtration rate after discharge. All patients were followed up for at least one year or until the occurrence of death after coronary angiography.

Results

Overall, contrast-induced nephropathy occurred in 41 (5.1%) patients. During a median follow-up of 1.4±1.1 years, 80 (10.0%) cases had subsequent decline in renal function. After adjustment for demographic characteristics, kidney function, traditional risk factors, and medications, higher galectin-1 level was found to be independently associated with a higher risk for mortality and renal function decline (tertile 2, HR=3.12 95% CI,1.25–7.78; tertile 3, HR=3.25, 95% CI,1.42–7.41) but not for contrast-induced nephropathy, regardless of the presence of diabetes.

Conclusions

Higher baseline serum galectin-1 levels were associated with a higher risk of mortality and renal function decline in patients undergoing coronary angiography. Galectin-1 may play a pivotal role in progressive renal dysfunction, but further studies are needed to verify these results.

Acknowledgement/Funding

Ministry of Science and Technology of Taiwan (MOST 104-2314-B-075-047), Taipei Veterans General Hospital (V105C-0207, V106C-045, V108C-195)

Single-cell transcriptomics of 20 mouse organs creates a Tabula Muris

Here we present a compendium of single-cell transcriptomic data from the model organism Mus musculus that comprises more than 100,000 cells from 20 organs and tissues. These data represent a new resource for cell biology, reveal gene expression in poorly characterized cell populations and enable the direct and controlled comparison of gene expression in cell types that are shared between tissues, such as T lymphocytes and endothelial cells from different anatomical locations. Two distinct technical approaches were used for most organs: one approach, microfluidic droplet-based 3'-end counting, enabled the survey of thousands of cells at relatively low coverage, whereas the other, full-length transcript analysis based on fluorescence-activated cell sorting, enabled the characterization of cell types with high sensitivity and coverage. The cumulative data provide the foundation for an atlas of transcriptomic cell biology.

Formation of a Neurosensory Organ by Epithelial Cell Slithering

Epithelial cells are normally stably anchored, maintaining their relative positions and association with the basement membrane. Developmental rearrangements occur through cell intercalation, and cells can delaminate during epithelial-mesenchymal transitions and metastasis. We mapped the formation of lung neuroepithelial bodies (NEBs), innervated clusters of neuroendocrine/neurosensory cells within the bronchial epithelium, revealing a targeted mode of cell migration that we named "slithering," in which cells transiently lose epithelial character but remain associated with the membrane while traversing neighboring epithelial cells to reach cluster sites. Immunostaining, lineage tracing, clonal analysis, and live imaging showed that NEB progenitors, initially distributed randomly, downregulate adhesion and polarity proteins, crawling over and between neighboring cells to converge at diametrically opposed positions at bronchial branchpoints, where they reestablish epithelial structure and express neuroendocrine genes. There is little accompanying progenitor proliferation or apoptosis. Activation of the slithering program may explain why lung cancers arising from neuroendocrine cells are highly metastatic.

Surrogate estimates of insulin sensitivity in Chinese diabetic patients and their offspring

AIMS

To evaluate the relationship between surrogate measures of insulin sensitivity and results from euglycaemic insulin clamp in Chinese diabetic patients and their offspring.

METHODS

The study included 59 volunteers from 20 diabetic families. Each participant completed a 75-g oral glucose tolerance test (OGTT) and a euglycaemic insulin clamp. We tested the correlation of surrogate measures of insulin sensitivity with M-values and M/I ratios (the amount of glucose infused during 90-120 min of the clamp was defined as M, and the mean values of plasma insulin during 90-120 min as I) from the euglycaemic insulin clamp. These measures included fasting insulin (FPI), insulin at 120 min of OGTT, insulin area under the curve of OGTT, fasting glucose-to-insulin ratio, homeostasis model assessment for insulin sensitivity (HOMA-IR and HOMA %S) and the Matsuda-DeFronzo index from OGTT.

RESULTS

The Matsuda-DeFronzo index closely correlated to M-value and M/I in 21 diabetic, 38 non-diabetic individuals and the 59 participants overall (with M-value, r = 0.68, 0.84 and 0.84; with M/I, r = 0.71, 0.72 and 0.75, respectively, all P < 0.001). Without OGTT, HOMA %S was a good surrogate index for diabetic (correlated to M-value and M/I, r = 0.71 and 0.68, P = 0.001) and for non-diabetic subjects (to M-value, r = 0.73; to M/I, r = 0.55, both P < 0.001). FPI was as good as HOMA %S and Matsuda-DeFronzo index.

CONCLUSIONS

The Matsuda-DeFronzo index, HOMA %S and FPI are good surrogate estimates of insulin sensitivity in Chinese diabetic subjects and their offspring.

Exacerbation of insulin resistance and postprandial triglyceride response in newly diagnosed hypertensive patients with hypertriglyceridaemia

The purpose of the study is to examine the differences in insulin resistance and postprandial triglyceride (TG) response between hypertensive patients with or without hypertriglyceridaemia. The study is a comparative cohort study with matching. Thirty-one newly diagnosed hypertensive patients without any medication were recruited from a health survey. The participants were further divided into two groups: those with fasting TG <2.26 mmol/L, and those with TG between 2.26 and 5.65 mmol/L. Both groups were matched in age, sex, body mass index and waist circumference. Each patient received a 75-g oral glucose tolerance test, an insulin suppression test, and a 1000 kcal high fat mixed meal test. The hypertriglyceridaemic hypertensive patients had significantly higher fasting insulin, 2-h plasma glucose, 2-h insulin, and steady-state plasma glucose (SSPG) (13.16 +/- 1.87 vs 9.76 +/- 3.18 mmol/L). They also had a greater postprandial TG response to the challenge of mixed meal (DeltaAUC 20.76 +/- 10.06 vs 7.97 +/- 3.18 mmol 8 h/L). The postprandial TG response was closely correlated (r = 0.72-0.95, P < 0.0001) with fasting TG in all hypertensive patients. Both fasting TG levels and postprandial TG response were significantly (P < 0.05) correlated with SSPG. In conclusion, the hypertensive patients with hypertriglyceridaemia were more insulin resistant than those without it. Exacerbation of postprandial hypertriglyceridaemia was identified in these patients. The TG response to the challenge of high fat meal was significantly correlated with fasting TG and insulin resistant in them. The results provide a rationale for the alleviation of insulin resistance and hypertriglyceridaemia in these atherosclerosis-prone hypertensive patients.

Waist circumference predicts insulin resistance in offspring of diabetic patients

The purpose of the study was to identify a good abdominal obesity index for insulin resistance in offspring of diabetic patients. A total of 74 non-diabetic subjects (male =36; female =38) were recruited from a diabetic family study. The waist circumference (W), waist-hip ratio (WHR) and conicity index were used as the abdominal obesity indices. The body mass index (BMI) and indices obtained from bioelectric impedance analysis (BIA) (body fat percentage, fat mass and fat mass index) were used as overall obesity indices. Fasting plasma insulin (FPI), homeostasis model assessment for insulin resistance (HOMA-IR) and Matsuda-Defronzo index from oral glucose tolerance test were chosen as the insulin sensitivity indices. We correlated obesity indices with insulin resistance indices with age and family adjusted. W was closely correlated in both sexes of subjects with Matsuda-DeFronzo index (male, r=-0.661,p<0.001; female, r=-0.419,p=0.026), FPI (male, r=0.614,p=0.001; female, r=0.503,p=0.006) and HOMA-IR (male, r=0.609,p=0.001; female, r=0.472,p=0.011). WHR and its log transformation predicted insulin resistance only in males. BMI as an overall obesity index was in good correlation with Matsuda-DeFronzo index (male, r=-0.646,p<0.001; female, r=-0.469,p=0.012), FPI (male, r=0.711,p<0.001; female, r=0.464,p=0.013) and HOMA-IR (male, r=0.708,p<0.001; female, r=0.469,p=0.012). Overall obesity indices from BIA were similar to BMI to predict insulin resistance. In conclusion, W is a good abdominal obesity predictor of insulin resistance in offspring of diabetic patients in Taiwan.

Propylthiouracil-induced hemolytic anemia

Propylthiouracil (PTU)-induced hemolytic anemia is extremely rare. We reported a case of Graves' disease with these unusual clinical manifestations. A 41-year-old female presented with recurrent attacks of severe hemolytic anemia after PTU therapy. Sugar water test and erythrocytes osmotic fragility test revealed no cellular membrane defect of red blood cells. Antinuclear antibody, direct and indirect Coombs' tests were all negative and glucose-6-phosphate dehydrogenase activity was also within normal limits. PTU was not discontinued promptly due to unrecognizableness of such a rare case until two months later with recurrent attacks of severe hemolytic anemia. 1-131 therapy was performed on suspicion of related hemolytic anemia. Unfortunately, challenge of PTU occurred incidentally after discontinuation of PTU followed by severe hemolytic anemia. The diagnosis of PTU-induced hemolytic anemia was established thereafter. A MEDLINE search revealed only one such case reported in English literature. This is the first case report in Taiwan. It should be kept in mind that hemolytic anemia may be a rare complication of PTU therapy.

Antimicrobial resistance and serotype distribution of Streptococcus pneumoniae infections in Kaohsiung from 1996 through 1999

A total of 89 isolates of Streptococcus pneumoniae were obtained from 86 patients during the period from November 1996 through September 1999 at the Kaohsiung Medical University Hospital. The purpose of this study was to determine the antimicrobial susceptibilities and the distribution of serotypes of these isolates, and to correlate these findings with the clinical characteristics of patients. Twenty-one (23.6%) isolates were obtained from patients aged below 5 years, and 38 (42.7%) from patients aged over 65 years. These 86 patients included 53 pneumonia, 13 bacteremia (including 6 with septic shock), 8 urinary tract infection, 8 soft tissue infections, 7 acute exacerbation of chronic bronchitis, 2 ophthalmic infection, and 2 cholecystitis cases. The most frequent serotypes were types 20 (10.1%), 6 (9%), 10 (9%), 11 (9%), and 23 (9%). All isolates were included in the serotypes represented in the 23-valent pneumococcal vaccine. Thirty-four (38.2%) isolates showed reduced penicillin susceptibility by the E-test. The predominant serotypes of penicillin-resistant S. pneumoniae were types 11 (17.6%), 7 (14.7%), 6 (8.8%), 8 (8.8%), and 23 (8.8%). All isolates were susceptible to vancomycin. Resistance rate to erythromycin was 49.4%, chloramphenicol, 20.2%; and trimethoprim/sulfamethoxazole, 61.8%. Multiple resistance (> or = 3 classes of antibiotics) was found in 28 (31.5%) isolates, of which the majority were serotypes 11 (14.3%), 7 (14.3%), 6 (10.7%), 8 (10.7%), and 23 (10.7%).

Low frequency of rearrangement of TRK protooncogene in Chinese thyroid tumors

The TRK protooncogene (NTRK1) encodes a cell-surface transmembrane tyrosine kinase (TK) acting as a receptor for nerve growth factor. Oncogenic potential in thyrocytes results from replacing the 5' portion by regulatory parts of other genes, leading to constitutive TK expression. In Italy, human papillary thyroid carcinoma (PTC) shows a frequent activation (50%) of the TK receptor genes NTRK1 and RET. Both genes undergo oncogenic rearrangements by the same mechanism. We previously reported high frequency (6/11) of rearrangement of the RET protooncogene in Chinese PTCs. Wide differences in the frequency (0-10.9%) of the NTRK1 rearrangement in PTCs have been reported in different populations. To investigate the frequency of TRK protooncogene rearrangement in Chinese thyroid tumors, we performed reverse transcriptase polymerase chain reaction to amplify specific TRK rearrangement transcripts. We examined thyroid tumors of 40 patients, including 14 papillary carcinomas, 4 follicular carcinomas, 1 Hurthle cell carcinoma, 1 insular carcinoma, and 20 nodular goiters. NF874 NIH3T3, NF723 NIH3T3, NF861 NIH3T3, and NF881 NIH3T3 were used as controls for TRK-T3, TRK-T2, TRK-T1, and TRK, respectively. No known TRK protooncogene rearrangements were detected among the 40 thyroid tumors in our studies. We suggest that the TK receptor NTRK1 activation seems less important than RET activation in PTCs in the Chinese population.

Using semi-automated oscillometric blood pressure measurement in diabetic patients and their offspring

To determine whether a semi-automatic oscillometric blood pressure (BP) monitor Dinamap 1846SX (DIN) can replace the standard mercury sphygmomanometer (SMS) for BP measurements in diabetic patients and their offspring, we compared SMS with DIN in 105 diabetic patients and their families. Their mean age was 50.6 (range 24-86) years, of whom 41 had diabetes mellitus (DM), 32 impaired glucose tolerance and 32 non-DM. After resting quietly for 10 min, their right arm BP were measured twice with each device at random and with 1-min intervals between each measurement. Agreement between measurements was tested by plotting the differences between the methods against means and by intraclass correlation coefficient (r(I)). The DIN was also evaluated by the criteria of American Association for the Advancement of Medical Instrumentation (AAMI), the British Hypertension Society (BHS) criteria and clinical criteria of O'Brien. All measurements by DIN [first readings or averaged readings of duplicate measurements of systolic BP (SBP) or diastolic BP (DBP)] satisfied the AAMI criteria and had good agreement with SMS (r(I)=. 951 for SBP and r(I)=.905 for DBP). The first readings of systolic BP measured by DIN vs. SMS failed to satisfy the criteria by O'Brien and reached BHS grade C level. Other measurements passed the limits of O'Brien and reached BHS grade A or B. In conclusion, averaged readings of duplicate BP measurements by DIN are interchangeable with that by SMS in Chinese diabetic patients and their offspring. Only one single DIN measurement is not acceptable for clinical application.

Application of representational difference analysis to cloning a Mycoplasma arthritidis specific DNA fragment

Representation difference analysis (RDA) was applied to isolate a Mycoplasma arthritidis specific DNA fragment. The DNA fragment obtained was verified to be M. arthritidis specific by polymerase chain reaction (PCR) and dot blot hybridization tests. The size of this fragment was 194 bp and the nucleotide sequence was also determined.

Localization, dynamics, and protein interactions reveal distinct roles for ER and Golgi SNAREs

ER-to-Golgi transport, and perhaps intraGolgi transport involves a set of interacting soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) proteins including syntaxin 5, GOS-28, membrin, rsec22b, and rbet1. By immunoelectron microscopy we find that rsec22b and rbet1 are enriched in COPII-coated vesicles that bud from the ER and presumably fuse with nearby vesicular tubular clusters (VTCs). However, all of the SNAREs were found on both COPII- and COPI-coated membranes, indicating that similar SNARE machinery directs both vesicle pathways. rsec22b and rbet1 do not appear beyond the first Golgi cisterna, whereas syntaxin 5 and membrin penetrate deeply into the Golgi stacks. Temperature shifts reveal that membrin, rsec22b, rbet1, and syntaxin 5 are present together on membranes that rapidly recycle between peripheral and Golgi-centric locations. GOS-28, on the other hand, maintains a fixed localization in the Golgi. By immunoprecipitation analysis, syntaxin 5 exists in at least two major subcomplexes: one containing syntaxin 5 (34-kD isoform) and GOS-28, and another containing syntaxin 5 (41- and 34-kD isoforms), membrin, rsec22b, and rbet1. Both subcomplexes appear to involve direct interactions of each SNARE with syntaxin 5. Our results indicate a central role for complexes among rbet1, rsec22b, membrin, and syntaxin 5 (34 and 41 kD) at two membrane fusion interfaces: the fusion of ER-derived vesicles with VTCs, and the assembly of VTCs to form cis-Golgi elements. The 34-kD syntaxin 5 isoform, membrin, and GOS-28 may function in intraGolgi transport.

A novel murine P-450 gene, Cyp4a14, is part of a cluster of Cyp4a and Cyp4b, but not of CYP4F, genes in mouse and humans

Genomic clones for Cyp4a12 and a novel member of the murine Cyp4a gene family were isolated. The novel gene, designated Cyp4a14, has a GC rich sequence immediately 5' of the transcription start site, and is similar to the rat CYP4A2 and CYP4A3 genes. The Cyp4a14 gene spans approximately 13 kb, and contains 12 exons; sequence similarity to the rat CYP4A2 gene sequence falls off 300 bp upstream from the start site. In view of the known sex-specific expression of the rat CYP4A2 gene, the expression and inducibility of Cyp4a14 was examined. The gene was highly inducible in the liver when mice were treated with the peroxisome proliferator, methylclofenapate; induction levels were low in control animals and no sex differences in expression were observed. By contrast, the Cyp4a12 RNA was highly expressed in liver and kidney of control male mice but was expressed at very low levels in liver and kidney of female mice. Testosterone treatment increased the level of this RNA in female liver slightly, and to a greater extent in the kidney of female mice. In agreement with studies on the cognate RNA, expression of Cyp4a12 protein was male-specific in the liver of control mice and extremely high inducibility of Cyp4a10 protein, with no sex differences, was also demonstrated. In view of the overlapping patterns of inducibility of the three Cyp4a genes, we investigated whether the three genes were co-localized in the genome. Two overlapping yeast artificial chromosome (YAC) clones were isolated, and the three Cyp4a genes were shown to be present on a single YAC of 220 kb. The Cyp4a genes are adjacent to the Cyp4b1 gene, with Cyp4a12 most distant from Cyp4b1. The clustering of these two gene subfamilies in the mouse was replicated in the human, where the CYPA411 and CYP4B1 genes were present in a single YAC clone of 440 kb. However, the human CYP4F2 gene was mapped to chromosome 19. Phylogenetic analysis of the CYP4 gene families demonstrated that CYP4A and CYP4B are more closely related than CYP4F.

Protein interactions regulating vesicle transport between the endoplasmic reticulum and Golgi apparatus in mammalian cells

The proposed cis-Golgi vesicle receptor syntaxin 5 was found in a complex with Golgi-associated SNARE of 28 kDa (GOS-28), rbet1, rsly1, and two novel proteins characterized herein: rat sec22b and membrin, both cytoplasmically oriented integral membrane proteins. The complex appears to recapitulate vesicle docking interactions of proteins originating from distinct compartments, since syntaxin 5, rbet1, and GOS-28 localize to Golgi membranes, whereas mouse sec22b and membrin accumulate in the endoplasmic reticulum. Protein interactions in the complex are dramatically rearranged by N-ethylmaleimide-sensitive factor. The complex consists of two or more subcomplexes with some members (rat sec22b and syntaxin 5) in common and others (rbet1 and GOS-28) mutually exclusively associated. We propose that these protein interactions determine vesicle docking/fusion fidelity between the endoplasmic reticulum and Golgi.

The vanishing defibrillator syndrome: incidence, mechanism, and clinical relevance

Intraperitoneal migration of an abdominally implanted cardioverter defibrillator is a complication not yet fully described. In a consecutive series of 195 patients, migration occurred between 1 and 20 months in 5 (8%) of the 63 patients in whom a subrectus abdomini placement of the generator was chosen. It was unrelated to the patients' clinical characteristics or the defibrillator model. Dysuria and inability to interrogate the device were present in every subject, and the diagnosis was confirmed by the characteristic abdominal x-ray appearance and the findings at the time of surgery. Adhesions involving the omentum, and in one case, the small bowels, were present in three patients and seem to be related to the length of intraabdominal permanence of the generator. Because this complication may be due to specific anatomical characteristics of the aponeurosis of the abdominal muscles, it is likely that its incidence will be unchanged by the use of smaller devices. A close follow-up of the generators implanted deep to the rectus fascia is therefore advisable.

Leiomyosarcoma of the left atrium: a case report

Primary malignant cardiac tumors are uncommon, and cardiac leiomyosarcoma is extremely rare. We reported a case of left atrial (LA) leiomyosarcoma with unusual clinical manifestations. A 28-year-old female presented with unknown cause of fever, body weight loss and anemia for two months. Echocardiography and magnetic resonance image study disclosed a 5 x 3 x 3.6 cm3 lobulated mass in the LA with invasion to its posterior wall. Histologic and immuno-histochemical studies of the resected specimen revealed a picture of leiomyosarcoma. The patient improved after surgical resection and post-operative chemotherapy. The literature was reviewed with a discussion of the clinical manifestations, diagnosis and treatment strategy of this rare tumor. Diagnosis of LA leiomyosarcoma is frequently delayed to make a very poor prognosis. Postoperative chemotherapy should be considered because of highly possible incomplete resection. However, an optimal treatment regimen remains unknown.

Aortoscopy: a guidance system for endoluminal aortic surgery

PURPOSE

The aim of this project was to evaluate the feasibility of aortoscopy for guidance of endoluminal aortic procedures and to determine whether aortoscopy has advantages over fluoroscopy in a pig model.

METHODS

To establish feasibility aortoscopic guidance was used for making endoluminal aortic measurements, cannulating small arteries for arteriograpy, and placing intraaortic stents and grafts in 11 pigs. To compare aortoscopy and fluoroscopy measurements were made and stents were placed by a surgeon using only aortoscopic guidance in 10 pigs and by an interventional radiologist using only fluoroscopic guidance in 10 pigs. Postmortem dissections were performed to determine measurement and device placement accuracy.

RESULTS

In the feasibility study aortoscopic measurements differed from postmortem measurements by a mean distance (+/- SD) of 1.2 +/- 0.2 mm. Stents and grafts were placed a mean of 2.3 +/- 1.9 mm distal to the most inferior renal artery with no stent covering an orifice. All attempts at cannulating spinal arteries greater than 2 mm in diameter were successful. In the comparison of aortoscopic and fluoroscopic guidance, fluoroscopic measurements differed from postmortem measurements by 2.6 +/- 2.4 mm (p = 0.223). Stents placed with aortoscopic guidance were 1.1 +/- 1.3 mm distal to the most inferior renal artery, whereas stents placed with fluoroscopic guidance were 3.4 +/- 2.5 mm distal to the most inferior renal artery (p = 0.019).

CONCLUSIONS

These results demonstrate that aortoscopy is a useful guidance system for endoluminal aortic procedures and may have advantages over fluoroscopy alone.

Angioscopic evaluation of an endoluminal aortic graft: the first clinical experience

PURPOSE

Balloon aortoscopy has been described for viewing aortic endoluminal anatomy and guiding aortic stent placement in animals. We report the first clinical use of this technique to visually inspect the proximal portion of a 1-year-old endovascular aortic graft, its proximal fixation stent, and its relationship to the renal arteries.

METHODS

The aortoscope is a modified fiber-optic endoscope that is fitted over the lens with a transparent, saline-filled balloon for blood displacement. Its performance was evaluated in a 62-year-old woman who had a Parodi-type Dacron/modified Palmaz stent endoluminal graft implanted to exclude an infrarenal aortic aneurysm in 1994. One year later, during an angioplasty procedure for symptomatic left subclavian and left common iliac artery stenoses, the 1-year-old endoluminal graft was inspected with the balloon-tipped angioscopic assembly.

RESULTS

Introduced via the left brachial artery, the aortoscope provided a panoramic view of the endoluminal surface through the solution-filled balloon. The endoluminal aortic graft was clearly identified, as were both renal artery orifices proximal to the graft. The surface of the proximal stent was smooth and without exposed metal. No complications occurred with the angioscopy technique.

CONCLUSIONS

Aortic angioscopy can be used to evaluate endoluminal aortic grafts and endoluminal anatomy. It provides clear, magnified views that may be useful for guiding precise placement and assessing the function and healing of endoluminal devices in the aorta.

An angioscopic method for intraluminal aortic evaluation and stent placement

PURPOSE

The purpose of this study was to develop an angioscopic technique to visualize the endoluminal surface of the aorta and to guide vascular stent placement.

METHODS

A fiberoptic angioscope, fitted with a balloon at its tip, was passed via a carotid arteriotomy into the abdominal aorta of seven anesthetized pigs. Saline solution inflation of the balloon allowed for blood displacement and clear visualization of the endoluminal anatomy. After the left renal artery orifice had been identified with angioscopy, a catheter was inserted via a left femoral sheath to cannulate the orifice under direct visualization. The position of the catheter was verified angiographically. A vascular stent was loaded onto an angioplasty balloon, inserted through a right femoral arteriotomy, positioned by use of angioscopic visualization, and deployed immediately below the left renal artery orifice.

RESULTS

The aortic trifurcation and the lumbar and renal artery orifices were clearly visualized in every animal. Vascular stents were placed in seven animals within an average of 3.14 +/- 1.14 mm (mean +/- SEM, range 0 to 8 mm) below the inferior rim of the left renal artery orifice. No stents were positioned above a renal artery orifice or obstructed blood flow.

CONCLUSIONS

This angioscopic technique permitted detailed evaluation of aortic endoluminal anatomy and precise implantation of vascular stents. Direct endovascular visualization may facilitate other endovascular procedures, including endovascular grafting.

[Drug resistance and plasmid analysis in Pseudomonas aeruginosa]

One hundred and ninety seven strains of Pseudomonas aeruginosa were isolated from urine (59 strains), wound pus (60 strains), sputum (30 strains), stool (30 strains) and eye discharge (18 strains) at Kaohsiung medical College Hospital. These strains were serotyped with antisera against O antigens and tested with twelve different antimicrobial agents. The results showed that the most frequently isolated strains were serotype E (41.1%), followed by serotype B (20.3%), serotype F (10.7%) and serotype L (9.1%). In in vitro susceptibility testing, all isolated strains were resistant to chloramphenicol and tetracycline. Otherwise, these isolates were highly susceptible to ceftazidime (95.4%), enoxacin (89.3%) and piperacillin (87.8%). The isolates from urine exhibited more multiple drug resistance patterns than those of other specimens. When plasmid content was analysed from pseudomonas aeruginosa, only 15.2% (30/197) of isolates carried plasmids. By conjugation, transformation and mobilization experiments, it was shown that 13.3% (4/30) of plasmid carrying strains contained R plasmids.

In vivo angioscopic visualization of right heart structure in dogs by means of a balloon-tipped fiberoptic endoscope: potential role in percutaneous ablative procedures

We designed an angioscopic system that consisted of a fiberoptic endoscope enclosed in a polyurethane thin-wall tube with a latex balloon attached to its distal end. In 10 anesthetized closed-chest dogs the angioscope was placed in the right heart via a femoral vein. By inflating the balloon with 5 to 10 ml of normal saline solution to displace the blood, the endocardial structure of the right heart was visualized. Under fluoroscopic guidance and direct vision, an ablation catheter was placed inside the coronary sinus or in its vicinity, and radiofrequency energy was delivered through the catheter tip to create a lesion. The appearance and anatomic location of the lesion and the endocardial structure as seen through the angioscope correlated well with the results of postmortem examination. There were no or minimal changes in heart rate, blood pressure, or cardiac output by inflating the balloon to a volume of 15 ml in the right atrium or right ventricular cavity. An inflated balloon may produce single or repetitive atrial or ventricular arrhythmias, but not sustained tachyarrhythmia. Our study demonstrates that in vivo visualization of the interior of the right heart is feasible and that our angioscope can be used to assist placement of catheter at a specific location in the right atrium and to verify its location with no or minimal hemodynamic effects and without causing significant arrhythmias.

Effect of verapamil on an accessory pathway manifesting as "fatigue phenomenon" in Wolff-Parkinson-White syndrome

Electrophysiologic study was performed in a 52-year-old man with type A ventricular preexcitation. An accessory atrioventricular pathway with no ventriculoatrial conduction was localized to the posteroseptal region. "Fatigue phenomenon," defined as suppression of atrioventricular conduction following rapid pacing, was observed to be provoked by atrial pacing in a rate- and duration-dependent manner. Administration of 5 mg of intravenous verapamil during sinus rhythm abolished the delta waves. These observations may indicate that pathologic changes in the accessory pathway are responsible for these phenomena.

Carbamazepine-induced cardiac dysfunction. Characterization of two distinct clinical syndromes

A patient with sinus bradycardia and atrioventricular block, induced by carbamazepine, prompted an extensive literature review of all previously reported cases. From the analysis of these cases, two distinct forms of carbamazepine-associated cardiac dysfunction emerged. One patient group developed sinus tachycardias in the setting of a massive carbamazepine overdose. The second group consisted almost exclusively of elderly women who developed potentially life-threatening bradyarrhythmias or atrioventricular conduction delay, associated with either therapeutic or modestly elevated carbamazepine serum levels. Because carbamazepine is widely used in the treatment of many neurologic and psychiatric conditions, the recognition of the latter syndrome has important implications for the use of this drug in elderly patients.

Increased risk of death and cardiac arrest from encainide and flecainide in patients after non-Q-wave acute myocardial infarction in the Cardiac Arrhythmia Suppression Trial. CAST Investigators

This report examines whether in the Cardiac Arrhythmia Suppression Trial death and cardiac arrest from encainide, flecainide and moricizine during the titration phase and from encainide and flecainide during the follow-up phase were related to presence (Q-wave acute myocardial infarction [Q-AMI]) or absence (non-Q-AMI) of pathologic Q waves. In all, 2,371 patients (70% with Q-AMI, 26% with non-Q-AMI, and 4% unknown) entered the titration phase, starting 117 +/- 163 days after index AMI and lasting for an average of 21 days. For the titration phase, no significant differences existed between Q-AMI and non-Q-AMI patients for death and cardiac arrest rate, ventricular premature complex suppression rate, and nonrandomization rate. A total of 1,498 patients entered the follow-up phase of an average of 10 months (starting 129 +/- 158 days after the index AMI), and were randomized to encainide or flecainide, or their matching placebos. In the placebo group, non-Q-AMI patients had a significantly lower rate of death and cardiac arrest than Q-AMI patients (1.0 and 4.6%, respectively; p = 0.04). Encainide and flecainide significantly elevated death and cardiac arrest rate in both non-Q-AMI patients (8.7%, p less than 0.01) and Q-AMI patients (7.8%, p = 0.04). The relative risk for encainide or flecainide over placebo in the non-Q-AMI patients was 8.7, which was significantly higher than 1.7 observed for the Q-AMI patients (p = 0.03). None of the baseline characteristics had any significant interaction with encainide or flecainide.(ABSTRACT TRUNCATED AT 250 WORDS)

Pre-excited RR intervals during atrial fibrillation in the Wolff-Parkinson-White syndrome: influence of the atrioventricular node refractory period

The ventricular rate and percent of pre-excited QRS complexes during atrial fibrillation were compared in two groups of patients with the Wolff-Parkinson-White syndrome. Group A consisted of 22 patients whose anterograde effective refractory period of the accessory pathway was longer than that of the atrioventricular (AV) node. Group B consisted of 23 patients in whom this relation was reversed. No patient had organic heart disease. Both groups had a similar effective refractory period of the accessory pathway (288 +/- 37 vs. 280 +/- 26 ms), whereas that of the AV node was shorter in group A than group B (242 +/- 25 vs. 285 +/- 27 ms, p = 0.0001). Patients in group A had a lower percent of pre-excited QRS complexes during atrial fibrillation (39 +/- 43% vs. 93 +/- 20%, p = 0.0001). In the 21 patients whose refractory period was measured, the difference was plotted against the percent of pre-excited QRS complexes; there was a significant correlation between the two (r = -0.83, p less than 0.001). In patients in whom pre-excited RR intervals were present, the pre-excited RR intervals were compared between the two groups. Both groups had similar effective refractory periods of the accessory pathway (265 +/- 22 vs. 280 +/- 27 ms) and ventricle (200 +/- 17 vs. 211 +/- 26 ms). The effective refractory period of the AV node was shorter in group A (248 +/- 22 vs. 285 +/- 28 ms, p = 0.0005). The shortest pre-excited RR interval did not show any difference (244 +/- 37 vs. 265 +/- 41 ms). However, both the average (328 +/- 39 vs. 397 +/- 56 ms, p = 0.001) and longest (495 +/- 109 vs. 666 +/- 205 ms, p = 0.02) pre-excited RR intervals were shorter in group A.(ABSTRACT TRUNCATED AT 250 WORDS)

Relationship between respiratory muscle function and age, sex, and other factors

To investigate the effects of gender and age on respiratory muscle function, 160 healthy volunteers (80 males, 80 females) were divided into four age groups. Twenty-eight of the male subjects were smokers. After the subjects were familiarized with the experimental procedure, respiratory muscle strength, inspiratory muscle endurance, and spirometric function, including forced vital capacity (FVC), forced expiratory volume in 1 s (FEV1), FEV1/FVC, tidal volume, breathing rate, and duty cycle, were measured. The respiratory muscle strength was indicated by the maximal static inspiratory and expiratory pressures (PImmax and PEmmax). Inspiratory muscle endurance was determined by the time the subject was able to sustain breathing against an inspiratory pressure load on a modified Nickerson-Keens device. The results showed that 1) except for inspiratory muscle endurance and FEV1/FVC, men had greater respiratory muscle and pulmonary functions than women, 2) respiratory muscle function and pulmonary function decreased with age, 3) smoking tended to lower duty cycle and FEV1/FVC and to enhance PE,mmax, and 4) inspiratory muscle endurance was greater in men who were physically active than in those who were sedentary. Therefore we conclude that there are sexual and age differences in respiratory muscle strength and pulmonary function and that smoking or physical activity may affect respiratory muscle function.

Fatal amiodarone hepatoxicity

The antiarrhythmic agent amiodarone is associated with numerous adverse effects, but clinically significant liver disease is rare. A patient is described who presented with muscle weakness, hepatomegaly, and ascites following 28 months of amiodarone usage. His condition deteriorated despite discontinuation of amiodarone therapy. A postmortem liver biopsy demonstrated necrosis, fibrosis, hyalin, and phospholipid-laden lysosomal lamellar bodies. Resolution of hepatic dysfunction may not necessarily occur on withdrawal of amiodarone if irreversible damage is already established. We speculate as to the reasons for the reportedly low incidence of overt liver disease, and suggest that hepatic enzyme levels, as well as other indicators of hepatic function, such as the serum albumin concentration, be monitored indefinitely in all patients while taking amiodarone.

Effect of uniformly prolonged, and increased basic dispersion of repolarization on premature dispersion on ventricular surface in dogs: role of action potential duration and activation time differences

Strong experimental evidence links ventricular fibrillation to an increased temporal dispersion of the recovery of excitability. The effect of an overall prolongation of repolarization and an increased basic dispersion of repolarization on premature dispersion was studied on ventricular surface in 10 dogs. Our observations reveal the operation of several fundamental electrophysiologic mechanisms controlling the conduction and the refractoriness in the ventricular myocardium in vivo. Action potential (AP) duration was influenced by the heart rate, the duration of the preceding AP and the proximity to the repolarization of the preceding AP. These effects can both slow, or enhance ventricular conduction, during propagation of premature impulses. This model may be applicable to several clinical situations where APs are prolonged (hypothermia, drug effects, changes in electrolytes) or when dispersion of refractoriness is increased (long QT-time syndrome, neural imbalance of the heart with and without heart disease.

Mechanism of ventricular arrhythmias caused by increased dispersion of repolarization

To explain the mechanism of arrhythmias dependent predominantly on increased dispersion of repolarization, we created a model in which increased dispersion was induced by means of generalized hypothermia (29 degrees C) and regional warm blood (38-43 degrees C) perfusion (RWBP) via a coronary artery branch. In 23 open-chest dogs, hypothermia plus RWBP increased maximum dispersion of repolarization from 13 +/- 10 to 111 +/- 16 ms (P less than 0.001) due predominantly to the increased monophasic action potential duration (MAP) difference of six simultaneously recorded MAP's from the ventricular surface, from 10 +/- 15 to 97 +/- 16 ms (P less than 0.001). The maximal difference between activation times was not significantly changed while QRS duration increased from 47 +/- 6 to 52 +/- 7 ms (P less than 0.01). Ventricular arrhythmia (VA) did not occur spontaneously but was induced by a single ventricular premature stimulus (VPS) in all 23 dogs during hypothermia plus RWBP when dispersion reached a critical magnitude. The requirement of this critical magnitude of dispersion for the induction of VA was documented in 16 dogs by means of stepwise increments or decrements of dispersion. In four dogs an increase in atrial pacing rate by 24 beats/min-1 prevented induction of VA by decreasing dispersion from a critical magnitude of 103 +/- 5 ms to a nonarrhythmogenic value of 86 +/- 9 ms (P less than 0.05). In six dogs, we compared the stimulation-site dependent effects of VPS applied in the region with short and long MAPD. In all dogs VA was inducible only by VPS from the region with short MAPD.(ABSTRACT TRUNCATED AT 250 WORDS)

Dispersion of ventricular repolarization and arrhythmia: study of two consecutive ventricular premature complexes

The effect of two consecutive ventricular premature stimuli (S1S2) during atrial pacing on dispersion of repolarization and inducibility of ventricular arrhythmias was studied in 16 dogs under control conditions and in four dogs in the presence of an increased dispersion of repolarization during atrial pacing induced by general hypothermia and regional warm blood perfusion via selective cannulation of the distal branch of left anterior decending coronary artery. Dispersion of repolarization was measured as the maximal difference between the ends of six simultaneously recorded monophasic action potentials (MAPs) from anterior ventricular surface, and consisted of MAP duration difference and activation time difference. Dispersion of repolarization during atrial pacing at control was 29 +/- 7 msec (activation time difference 4 +/- 6 msec, MAP duration difference 25 +/- 8 msec), that after S1 at paraseptal the site was 81 +/- 8 msec (activation time difference 73 +/- 12 msec, MAP duration difference 8 +/- 5 msec), and that after S1S2 was 148 +/- 27 msec (activation time difference 103 +/- 21, MAP duration difference 44 +/- 26 msec). Neither S1 nor S1S2 induced ventricular arrhythmia. Hypothermia and regional warm blood reperfusion increased dispersion of repolarization during atrial pacing to 70 +/- 22 msec (activation time difference 9 +/- 3 msec, MAP duration difference 61 +/- 19 msec). During hypothermia and regional warm blood reperfusion, S1 produced a dispersion of repolarization of 149 +/- 29 msec (activation time difference 85 +/- 8 msec, MAP duration difference 64 +/- 23 msec) and did not induce ventricular arrhythmia.(ABSTRACT TRUNCATED AT 250 WORDS)

Asystole during treatment with amiodarone in a patient with persistent atrial tachycardia

During treatment with amiodarone, digoxin and nadolol, asystole occurred repeatedly in a patient with chronic persistent automatic atrial tachycardia. Asystole did not occur after discontinuation of drug therapy, and rechallenge with amiodarone alone produced marked overdrive suppression of all pacemakers resulting in asystole. Amiodarone serum level was within therapeutic range. The possible electrophysiologic mechanisms by which amiodarone might suppress both normal and abnormal pacemakers are discussed. The occurrence of asystole at therapeutic serum concentration of amiodarone suggests that this drug should be used with caution.

Effect of amiodarone on electric induction, morphology, and rate of ventricular tachycardia and its relation to clinical efficacy

Using His bundle electrograms and programmed ventricular stimulation, the effects of chronic amiodarone treatment on induction, morphology, and the rate of ventricular tachycardia (VT) were studied in 17 consecutive patients treated with amiodarone for control of recurrent sustained VT or ventricular fibrillation. Studies were done before and after treatment with amiodarone for an average duration of 5.3 (range 2 to 18) months. During the control study, sustained VT could be induced in 16 patients. VT was initiated by single or double right ventricular (RV) extrastimuli in 14 patients, by double left ventricular (LV) extrastimuli in 1 patient, and by RV burst pacing in 1 patient. Only one pattern (morphology) of VT similar to that of spontaneous VT was induced in 12 patients and two patterns of VT in 4 patients. The average cycle length (CL) (mean +/- SD) of induced VT was 325.8 +/- 61.2 ms. After amiodarone, VT could be induced in 7 of 17 patients and was initiated by single RV extrastimuli in 5 patients, double RV extrastimuli in 1 patient, and RV burst pacing in 1 patient. In 3 of 5 patients in whom VT could be initiated by single RV extrastimuli, initiation of VT required double RV or double LV extrastimuli in the control study; in 1 of 5 patients VT could not be induced in the control study. Amiodarone induced nonclinical, polymorphic VT in 4 patients in whom only clinical VT could be induced during the control study. Compared to control, the CL of induced VT was significantly longer (322 +/- 65.7 vs 416 +/- 41.5 ms; P less than 0.001).+

Effect of amiodarone on retrograde conduction and refractoriness of the His-Purkinje system in man

The effects of long term treatment with oral amiodarone on retrograde conduction ( S2H2 interval) and refractoriness of the His-Purkinje system were studied in 11 patients using His bundle electrograms and the ventricular extrastimulus method. Ten patients had ventricular tachycardia and one supraventricular tachycardia. Electrophysiological studies were carried out before and after the patients had been taking their maintenance dose for a mean duration of 84 days. After amiodarone treatment the HV interval was prolonged in seven patients and unchanged in four. At comparable S1S2 intervals, the S2H2 intervals were longer after treatment with amiodarone in all patients than before. Similarly, the longest S2H2 intervals achieved after amiodarone were longer than the control values. Amiodarone significantly increased the relative, effective, and functional refractory periods of the His-Purkinje system. Thus amiodarone exerts important effects on the His-Purkinje system.

Treatment of ventricular tachycardia using an automatic scanning extrastimulus pacemaker

A patient with recurrent sustained ventricular tachycardia that was resistant to both conventional and experimental antiarrhythmic agents was treated with a programmable automatic scanning extrastimulus pacemaker. The antitachycardia pacemaker was implanted only after many episodes of spontaneous and laboratory-induced ventricular tachycardia were reliably and reproducibly terminated with programmed ventricular extrastimuli. In the 6 months since implantation of the automatic scanning pacemaker, all episodes of ventricular tachycardia have been terminated successfully by the pacemaker. Acceleration of rate of ventricular tachycardia or induction of ventricular fibrillation did not occur at any time during attempted termination of ventricular tachycardia by the pacemaker. The advantages of the automatic scanning extrastimulus pacemaker over other antitachycardia pacemakers are discussed.

Characteristics and possible mechanism of ventricular arrhythmia dependent on the dispersion of action potential durations

The arrhythmogenic role of increased dispersion of repolarization (dispersion) was studied in 23 open-chest dogs using six simultaneously recorded monophasic action potentials (MAPs) from the ventricular surface and programmed ventricular premature stimulation (VPS). Increased dispersion was induced by generalized hypothermia (29 degrees C) and regional warm blood (38-43 degrees C) perfusion through a coronary artery branch. Hypothermia and regional warm blood perfusion increased maximum dispersion from 13 +/- 10 to 111 +/- 16 msec (p less than 0.001), predominantly because of the increased MAP duration difference (10 +/- 15 vs 97 +/- 16 msec, p less than 0.001). The maximal difference between activation times was not significantly changed, but the QRS duration increased from 47 +/- 6 to 52 +/- 7 msec (p less than 0.01). Ventricular arrhythmia did not occur spontaneously but was induced by a single VPS in all 23 dogs during hypothermia and regional warm blood perfusion when dispersion reached a critical magnitude. The critical magnitude of dispersion required to induce ventricular arrhythmia was documented in 16 dogs by stepwise increments or decrements of dispersion. In four dogs, an increase in atrial pacing rate of 24 beats/min prevented induction of ventricular arrhythmia by decreasing dispersion from a critical magnitude of 103 +/- 5 msec to a nonarrhythmogenic value of 86 +/- 9 msec (p less than 0.05). In six dogs, we compared the stimulation site-dependent effects of VPS applied in the region with short and long MAPs. In all dogs, ventricular arrhythmia was inducible only by VPS from the region with a short MAP. Premature impulses from this region propagated more slowly than those from the region with a long MAP. Our results show that the large dispersion of repolarization facilitates the development of a conduction delay necessary to induce sustained arrhythmia by an early premature stimulus applied at the site with a short MAP.