Myocardial electrical propagation in patients with idiopathic dilated cardiomyopathy.

Myocardial propagation may contribute to fatal arrhythmias in patients with idiopathic dilated cardiomyopathy (IDC). We examined this property in 15 patients with IDC undergoing cardiac transplantation and in 14 control subjects. An 8 x 8 array with electrodes 2 mm apart was used to determine the electrical activation sequence over a small region of the left ventricular surface. Tissue from the area beneath the electrode array was examined in the patients with IDC. The patients with IDC could be divided into three groups. Group I (n = 7) had activation patterns and estimates of longitudinal (theta L = 0.84 +/- 0.09 m/s) and transverse (theta T = 0.23 +/- 0.05 m/s) conduction velocities that were no different from controls (theta L = 0.80 +/- 0.08 m/s, theta T = 0.23 +/- 0.03 m/s). Group II (n = 4) had fractionated electrograms and disturbed transverse conduction with normal longitudinal activation, features characteristic of nonuniform anisotropic properties. Two of the control patients also had this pattern. Group III (n = 4) had fractionated potentials and severely disturbed transverse and longitudinal propagation. The amount of myocardial fibrosis correlated with the severity of abnormal propagation. We conclude that (a) severe contractile dysfunction is not necessarily accompanied by changes in propagation, and (b) nonuniform anisotropic propagation is present in a large proportion of patients with IDC and could underlie ventricular arrhythmias in this disorder.

Alterations in 3,3'5'-triiodothyronine metabolism in response to propylthiouracil, dexamethasone, and thyroxine administration in man.

To elucidate the mechanisms involved in altering serum 3,3',5'-triiodothyronine (rT3) levels with absolute or relative low 3,5,3'-triiodothyronine (T3) states in man, agents capable of lowering circulating T3 levels were sequentially administered to six euthyroid subjects. These agents included propylthiouracil (PTU) (300 mg/6 h X 5 d), dexamethasone (DEX) (2 mg/6 h X 5 d), and thyroxine (T4) (3.0 mg load and 0.3 mg/d X 5 d). [125I] rT3 clearance rates and rT3 production rates were then determined. Increased serum rT3 levels and rT3/T4 values occurred with both PTU and DEX as compared with control, while T4 increased serum rT3 but did so without changing rT3/T4 values. The rT3 clearance rate was significantly decreased by PTU without altering production rate, while DEX increased the rT3 production rate without altering the rT3 clearance rate. T4 administration did not change rT3 clearance but proportionately increased rT3 production. These responses indicate that circulating rT3 predominantly originates from a non-PTU inhibitable deiodinase enzyme system located in extrahepatic tissues. This enzyme system appears to have a high capacity and low affinity for T4 and can be stimulated by DEX administration.

Microinjection of mRNA enhances translational efficiency of human adenovirus fiber message in monkey cells.

In monkey cells abortively infected with human adenovirus serotype 2, the synthesis of the fiber polypeptide of the virion capsid is reduced by at least a factor of 100 when compared with that in monkey cells productively infected with a host range mutant of adenovirus serotype 2 (Ad2hr400). However, the steady-state level of fiber-encoding mRNA present in abortively infected monkey cells is only reduced by a factor of 5 to 10. When mRNA isolated from abortively and productively infected monkey cells was microinjected into the cytoplasms of uninfected or abortively infected monkey cells, no differences in the efficiency of translation of the fiber messages from these two sources were observed. These results suggest that the block to synthesis of the fiber polypeptide in abortively infected monkey cells does not reside in the translational machinery of the abortively infected cells themselves but may involve compartmentalization of the fiber message within the cells or an altered processing of the fiber message which prevents correct presentation to the ribosomes.

Isolation of a gene encoding a functional zinc finger protein homologous to erythroid Krüppel-like factor: identification of a new multigene family.

We have identified and characterized the gene for a novel zinc finger transcription factor which we have termed lung Krüppel-like factor (LKLF). LKLF was isolated through the use of the zinc finger domain of erythroid Krüppel-like factor (ELKF) as a hybridization probe and is closely related to this erythroid cell-specific gene. LKLF is expressed in a limited number of tissues, with the predominant expression seen in the lungs and spleen. The gene is developmentally controlled, with expression noted in the 7-day embryo followed by a down-regulation at 11 days and subsequent reactivation. A high degree of similarity is noted in the zinc finger regions of LKLF and EKLF. Beyond this domain, the sequences diverge significantly, although the putative transactivation domains for both LKLF and EKLF are proline-rich regions. In the DNA-binding domain, the three zinc finger motifs are so closely conserved that the predicted DNA contact sites are identical, suggesting that both proteins may bind to the same core sequence. This was further suggested by transactivation assays in which mouse fibroblasts were transiently transfected with a human beta-globin reporter gene in the absence and presence of an LKLF cDNA construct. Expression of the LKLF gene activates this human beta-globin promoter containing the CACCC sequence previously shown to be a binding site for EKLF. Mutation of this potential binding site results in a significant reduction in the reporter gene expression. LKLF and EKLF can thus be grouped as members of a unique family of transcription factors which have discrete patterns of expression in different tissues and which appear to recognize the same DNA-binding site.

Regulated expression of the human beta globin gene in transgenic mice requires an upstream globin or nonglobin promoter.

Transgenic mice have been used extensively to study elements governing the erythroid-specific developmental switch from human fetal gamma to human adult beta globin. Previous work demonstrated that a small construct composed of hypersensitive site 2 (HS2) of the locus control region (LCR) linked to the gamma and beta globin genes (HS2-gamma-beta) is sufficient for correct tissue and temporal expression of these genes, whereas HS2-beta alone is inappropriately expressed in the embryo. Two models, which are not mutually exclusive, have been proposed to explain these results and those of other constructs in transgenic mice. One model emphasizes the conserved polarity in the globin locus and suggests a distance effect whereby the beta globin gene must be removed from the LCR/HS2 to prevent an early and incorrect activation of this gene in the embryonic compartment. A second hypothesis proposes a competition between the gamma and beta globin gene promoters for interaction with the LCR/HS2. The active gamma globin gene promoter positioned between the LCR/HS2 and the beta globin gene thereby interacts with the HS2 elements early in erythroid development and is expressed until a change in putative stage-specific nuclear factors makes an interaction with the adult beta globin gene more favorable. In an effort to test the competition model, a construct has been prepared in which a small deletion was produced in the promoter region of the gamma globin gene while in the context of the HS2-gamma-beta plasmid. Analysis of this construct in transgenic mice reveals a constitutive unregulated expression of the human beta globin gene during erythroid development. To determine if this competition effect is specific for globin genes, a heterologous reporter gene has been substituted for the gamma globin gene in the construct HS2-gamma-beta. In this case, the beta globin gene exhibits correct developmental expression. This data is consistent with a model in which transcription from a promoter upstream of the beta globin gene in some manner protects this adult gene from activation by the LCR/HS2 during early development.

Multidimensional rhythm disturbances as a precursor of sustained ventricular tachyarrhythmias.

Cardiac cycle dynamics reflect underlying physiological changes that could predict imminent arrhythmias but are obscured by high complexity, nonstationarity, and large interindividual differences. To overcome these problems, we developed an adaptive technique, referred to as the modified Karhunen-Loeve transform (MKLT), that identifies an individual characteristic ("core") pattern of cardiac cycles and then tracks the changes in the pattern by projecting the signal onto characteristic eigenvectors. We hypothesized that disturbances in the core pattern, indicating progressive destabilization of cardiac rhythm, would predict the onset of spontaneous sustained ventricular tachyarrhythmias (VTAs) better than previously reported methods. We analyzed serial ambulatory ECGs recorded in 57 patients at the time of VTA and non-VTA 24-hour periods. The disturbances in the pattern were found in 82% of the recordings before the onset of impending VTA, and their dimensionality, defined as the number of unstable orthogonal projections, increased gradually several hours before the onset. MKLT provided greater sensitivity and specificity (70% and 93%) compared with the best traditional method (68% and 67%, respectively). We present a theoretical analysis of MKLT and describe the effects of ectopy and slow changes in cardiac cycles on the disturbances in the pattern. We conclude that MKLT provides greater predictive accuracy than previously reported methods. The improvement is due to the use of individual patterns as a reference for tracking the changes. Because this approach is independent of the group reference values or the underlying clinical context, it should have substantial potential for predicting other forms of arrhythmic events in other populations.

Spontaneous sustained ventricular tachycardia in the Electrophysiologic Study Versus Electrocardiographic Monitoring (ESVEM) Trial.

OBJECTIVES: We compared the QRS waveforms of the initial and subsequent complexes of spontaneous sustained monomorphic ventricular tachycardia and the rhythm induced at electrophysiologic study to test the theory that premature ventricular complexes "trigger" spontaneous ventricular tachycardia and that a stable substrate exists such that the spontaneous arrhythmia can be reproduced at electrophysiologic study. BACKGROUND: Failure rates have been high in several recent studies in which prevention of ventricular tachyarrhythmias was guided by suppression of premature ventricular complexes or induced ventricular tachycardias. METHODS: Digital waveform analysis was used to distinguish events of ventricular tachycardia initiated by configurationally distinct, possibly triggering, complexes (type 1) from events in which the initial QRS waveforms were identical to subsequent complexes, suggesting no requirement for premature ventricular beats (type 2). RESULTS: Of 1,102 episodes of spontaneous ventricular tachycardia, 73 (6.6%) were type 1; 1,012 were type 2 (91.8%); and 17 (1.5%) were uncertain. Of 59 patients only 14 (24%) had only type 1 episodes (group 1), whereas 37 patients (63%) had predominantly type 2 events (group 2) (p < 0.0001). Sustained ventricular tachycardia was inducible in all group 1 patients, and in most (57%) the induced rhythm was similar to the spontaneous rhythm. Ventricular tachycardia could not be induced in 7 patients from group 2 (19%), and in 18 patients (49%) the induced and spontaneous rhythms were dissimilar. Recurrence of arrhythmia rates differed according to the guidance method in group 2. CONCLUSIONS: Discrepancies between observed and predicted modes of initiation of ventricular tachycardia and between spontaneous and induced rhythms could result in inappropriate guidance and subsequent failure of antiarrhythmic treatment.

Autonomic nervous system activity and the spontaneous initiation of ventricular tachycardia. ESVEM Investigators. Electrophysiologic Study Versus Electrocardiographic Monitoring Trial.

OBJECTIVES: We hypothesized that neurohormonal activity contributes to the initiation of sustained ventricular tachycardia (VT) as reflected in indices of heart rate variability (HRV). BACKGROUND: Autonomic nervous system activity participates in experimental arrhythmias but clinical studies have been inconsistent. METHODS: Holter electrocardiograms from 53 patients with VT were analyzed. Heart rate variability indices were determined over 5 and 15 min and 24 h and examined for changes before the onset of VT. Heart rate variability indices in the frequency domain included ultra low frequency power (FP) (ULFP): 0-0.0033 Hz; very low FP (VLFP): 0.0033-0.04 Hz; low FP (LFP): 0.04-0.15 Hz; high FP (HFP): 0.15-0.4 Hz; total power (TP); normalized LFP (LFPn); normalized HFP (HFPn), and the ratio: LFP/HFP. RESULTS: Heart rate variability indices were severely diminished: TP: 12,009+/-11,076 ms2; ULFP: 10,087+/-9,565 ms2; VLFP: 1,416+/-1,571 ms2; LFP: 544+/-620 ms2; HFP: 161+/-176 ms2, and LFP/HFP: 3.68+/-2.83. Heart rate increased before VT (80.4+/-17.3 to 85.3+/-17.4 bpm, p < 0.001). Several HRV variables declined 30 min before VT compared to 24-h values (VLFP: -5.89+/-17.81%, p = 0.031; LFP: -5.23+/-14.3%, p = 0.003; HFP: -4.35+/-13.7%, p = 0.04). LFPn and the LFP/HFP ratio decreased significantly before the onset of VT (-17.7+/-46.9%, p = 0.035 and -8.24+/-38.8%, p = 0.037, respectively), whereas HFPn increased slightly (4.29+/-29.9%, p = 0.097). CONCLUSIONS: Heart rate rose, whereas LFP, LFPn and LFP/HFP fell before the onset of VT. This pattern of changes could be explained by a rise in sympathetic activity and saturation of the HRV signal resulting in dissociation of the average and rhythmical effects of sympathetic activity. These findings suggest that alterations in autonomic activity contributed to arrhythmogenesis in this group of patients.

A comparison of T-wave alternans, signal averaged electrocardiography and programmed ventricular stimulation for arrhythmia risk stratification.

OBJECTIVES: The goal of this study was to compare T-wave alternans (TWA), signal-averaged electrocardiography (SAECG) and programmed ventricular stimulation (EPS) for arrhythmia risk stratification in patients undergoing electrophysiology study. BACKGROUND: Accurate identification of patients at increased risk for sustained ventricular arrhythmias is critical to prevent sudden cardiac death. T-wave alternans is a heart rate dependent measure of repolarization that correlates with arrhythmia vulnerability in animal and human studies. Signal-averaged electrocardiography and EPS are more established tests used for risk stratification. METHODS: This was a prospective, multicenter trial of 313 patients in sinus rhythm who were undergoing electrophysiologic study. T-wave alternans, assessed with bicycle ergometry, and SAECG were measured before EPS. The primary end point was sudden cardiac death, sustained ventricular tachycardia, ventricular fibrillation or appropriate implantable defibrillator (ICD) therapy, and the secondary end point was any of these arrhythmias or all-cause mortality. RESULTS: Kaplan-Meier survival analysis of the primary end point showed that TWA predicted events with a relative risk of 10.9, EPS had a relative risk of 7.1 and SAECG had a relative risk of 4.5. The relative risks for the secondary end point were 13.9, 4.7 and 3.3, respectively (p < 0.05). Multivariate analysis of 11 clinical parameters identified only TWA and EPS as independent predictors of events. In the prespecified subgroup with known or suspected ventricular arrhythmias, TWA predicted primary end points with a relative risk of 6.1 and secondary end points with a relative risk of 8.0. CONCLUSIONS: T-wave alternans is a strong independent predictor of spontaneous ventricular arrhythmias or death. It performed as well as programmed stimulation and better than SAECG in risk stratifying patients for life-threatening arrhythmias.

Differential regulation of rat T-kininogen by tumor necrosis factor and interleukin-6.

Rat T-kininogen (T-KG), a cysteine protease inhibitor, is an acute phase reactant which is induced to high levels in response to inflammation. Both hormones and cytokines participate in this regulation. To investigate the cis-acting elements responsible for the induction of gene expression, various 5'-fragments of the rat T-KG gene were fused to a chloramphenicol acetyltransferase marker gene. These constructs were transfected into a rat hepatoma cell line which was then treated with tumor necrosis factor or interleukin-6 or both cytokines. Expression of the chloramphenicol acetyltransferase gene was induced with interleukin-6 treatment, but suppressed by tumor necrosis factor. The 5'-region of the T-KG gene responsible for conferring both of these effects was localized between nucleotides -404 to -210 upstream of the transcription start site. Fragments containing this region were found to be effective in either orientation, and could also regulate a heterologous promoter.

Does a hidden pool of reverse triiodothyronine (rT3) production contribute to total thyroxine (T4) disposal in high T4 states in man.

A hidden pool of rT3 production represents a source of rT3 that is minimally reflected in circulating rT3 levels. To test for the existence of such a source of rT3 production in man, varying doses of the generalized deiodinase inhibitor iopanoic acid (IA) were administered to four hyperthyroxinemic subjects. The doses employed included low-IA (0.5-g load, then 0.5 g/day for 5 days), mid-IA (1.0-g load, then 1.0 g/day for 5 days), and high-IA (3.0-g load, then 3.0 g/day for 5 days). Each patient received 25 microCi [125I]rT3, iv, in the high T4 state and on day 3 of each IA dosing regimen. Serial blood and urine samples were obtained to determine serum rT3 clearance rates and the urinary thyronine metabolite patterns. Although total serum rT3 values were increased by all IA dosages (P less than 0.001), rT3 was lower with high-IA administration (P less than 0.02) than with low- or mid-IA regimens. Low-IA decreased rT3 clearance to 33 +/- 2 L/day (P less than 0.005), while increasing the daily rT3 production to 76 +/- 8 nmol/day (P less than 0.04) compared to the control values (150 +/- 10 L/day and 53 +/- 8 nmol/day, respectively). Mid-IA also reduced rT3 clearance (23 +/- 4 L/day; P less than 0.005) without changing rT3 production (50 +/- 10 nmol/day), while high-IA reduced both rT3 clearance (21 +/- 2 L/day; P less than 0.005) and production (39 +/- 9 nmol/day; P less than 0.04). Intravenously administered tracer rT3 could not be detected in the urine in the high T4 state, but rT3 could not be detected in the urine in the high T4 state, but was prominent after IA administration. It is concluded that a hidden pool of rT3 production exists in vivo in man. Further, low dose IA serves as a selective inhibitor of liver and kidney deiodinase systems, allowing reflection of this hidden rT3 pool in the blood and urine. It would appear that hypertrophy of this hidden pool of rT3 production occurs in high T4 states and may account for the majority of the unrecognized deiodinative metabolites of T4 generated in hyperthyroxinemia.

Characteristics of 3,5,3'-triiodothyronine sulfate metabolism in euthyroid man.

The sulfated conjugate of T3 (T3S) has long been recognized as a normal product of peripheral thyroid hormone metabolism. In order to better understand the role that T3S may play in this process, the metabolic handling of T3S was studied in euthyroid man. After the iv administration of [125I]T3S in man, T3S was found to be rapidly metabolized with estimated mean MCR of 135 +/- 15 liters/day (L/D) after a bolus injection and 127 +/- 8 L/D employing a constant infusion. The primary route of T3S disposal was by deiodination with an efficiency of 92%. The administration of propylthiouracil (PTU, 300 mg every 6 h x 5 days) and iopanoic acid (IA, 500 mg every day x 5 days), both inhibitors of deiodination, decreased clearance compared to control (87 +/- 9 L/D, P less than 0.01 and 46 +/- 10 L/D, P less than 0.002, respectively). A 3-day fast also reduced the clearance of T3S (56 +/- 10 L/D, P less than 0.002). All three maneuvers decreased the total urinary deiodination fraction of tracer T3S (control 91 +/- 2%, PTU 70 +/- 9%, P less than 0.04, IA 26 +/- 3%, P less than 0.0001, and fasting 58 +/- 6%, P less than 0.01). A strong correlation between T3S clearance and deiodination was noted for fasting and IA only (r = 0.78, P less than 0.003). However, no relationship between clearance and deiodination was noted with PTU administration presumably as a result of a compensatory increase in biliary losses of T3S. The urinary thyronine excretion pattern demonstrated the presence of small amounts of labeled T3,3,3'-T2, and 3,3'-T2S with the major metabolite being T3S itself. TSH levels were not influenced by the infusion of stable T3S designed to achieve a serum value greater than 50 ng/dL. No absorption of intact T3S was detected after its oral ingestion. In conclusion, T3S is rapidly cleared from the serum, primarily by deiodination, may undergo nondeiodinative disposal when hepatic deiodination is inhibited by PTU but not with IA or fasting, and has no intrinsic biological activity. Thus, T3S may serve as a metabolite of T3 for its rapid deiodinative disposal. Although the precise role T3S plays in human thyroid hormone metabolism has not been defined, the metabolic characteristics of T3S appear similar to that of an unidentified alternate T4 metabolite formed in low T3 states of fasting and nonthyroidal illness.

Primary structure of a gene encoding rat T-kininogen.

A gene encoding the acute-phase reactant, T-kininogen, has been isolated from a rat genomic library. The nucleotide sequence of all exons as well as of a large portion of the introns was determined. The gene, T-KG, is approximately 24 kb in length and contains 11 exons. The promoter appears to be rather unusual in that there are no consensus CCAAT or TATAA boxes or SP1-binding sites. An A-rich region present upstream of the transcription start point may function as a TATAA-equivalent sequence. In addition, several potential glucocorticoid regulatory elements and a sequence similar to the AP-1 binding site are present in the 5' region of the gene. The intron/exon boundaries in this T-KG gene are identical to those seen in the human K-kininogen gene. This is consistent with the inclusion of T-KG in the cystatin supergene family of cysteine protease inhibitors.

Characterization of the lung Krüppel-like transcription factor gene and upstream regulatory elements.

We previously described the isolation and characterization of the cDNA for lung Krüppel-like factor (LKLF), a zinc finger transcription factor that is predominately expressed in the lung of adult mice. In this study, we report the complete structure and nucleotide sequence of the mouse LKLF gene, which is comprised of three exons and two small introns. Moreover, the identification of critical sequence elements required for expression is described using reporter constructs with the LKLF promoter transfected into LA-4 lung cells. Results from these constructs reveal an important region for transcriptional activity that lies between the -490/-72bp upstream sequence. This region contains two canonical Sp1 binding sites that affect expression levels in a non tissue-specific manner. In addition, using a base-pair mutagenesis strategy, a region from -157/-72bp was found to be necessary for upregulating expression. In transfection assays, mutations of the -138/-111bp region resulted in approximately 70-80% loss of promoter activity. This cis-element does not appear to correspond to any known transcription factor consensus sequence. Moreover, mutations within this cis-region disrupt the binding of a protein complex from nuclear extracts of various tissues.

Central nervous system toxoplasmosis in homosexual men.

Many opportunistic infections have been associated with an acquired immunodeficiency state in which cellular immune status has been altered. Two homosexual patients are described who presented with fever, peripheral eosinophilia, and a travel history to Haiti and were found to have central nervous system toxoplasmosis. Despite definitive diagnosis and appropriate therapy, both died. Techniques for diagnosis of central nervous system toxoplasmosis are discussed, and the importance of brain biopsy in this clinical situation is stressed. Eosinophilia may serve as an early diagnostic marker for disseminated toxoplasmosis in homosexual patients.

Inhibition of human cytomegalovirus replication in a human retinal epithelial cell model by antisense oligonucleotides.

PURPOSE: The antiviral activity of first and second generation antisense oligonucleotides on human cytomegalovirus (CMV) replication was evaluated in two cell systems, the traditional system on human fibroblasts and on human retinal pigment epithelial (HRPE) cell culture system. METHODS: To evaluate CMV replication strategies within the retina, an HRPE cell system permissive to CMV replication was developed. In this study, the antiviral activity of the antisense oligonucleotides, ISIS 2922 (Vitraven) and ISIS 13312, was evaluated in the traditional fibroblast antiviral assay and in the HRPE cell system. Antiviral activity was measured by evaluating inhibition of virus induced cytopathic effect, virus plaque formation, and virus gene expression. RESULTS: Both oligonucleotides produced concentration-dependent inhibition of CMV cytopathic effect and CMV plaque formation in both human RPE cells and a human fibroblast cell line, MRC-5. The oligonucleotide, ISIS 2922, demonstrated a mean 50% inhibitory concentration (IC(50)) of 0.04 and 0.24 microM in HRPE and MRC-5 cells, respectively. The second-generation oligonucleotide, ISIS 13312, yielded similar results with IC(50) levels of 0.05 and 0.3 microM in HRPE and MRC-5 cells, respectively. Similar findings were obtained with a CMV clinical isolate. In addition, initiation of effective oligonucleotide treatment could be introduced 6 days after CMV infection in HRPE cells, whereas, in the fibroblast cell line, oligonucleotide treatment was only effective up to 3 days after infection. Semiquantitative RT-PCR analysis demonstrated significant inhibition of CMV intermediate early and late mRNAs by both oligonucleotides. CONCLUSIONS: These studies demonstrate that HRPE cells were significantly more sensitive than fibroblasts to the antiviral actions of ISIS 2922 and ISIS 13312. Moreover, the data indicate that the anti-CMV potency of the two oligonucleotides was similar. The enhanced potency of these oligonucleotides in HRPE cells may be associated with a delay in viral gene transcription and slow viral replication and spread in these cells.

Surgical exclusion of focal paroxysmal atrial tachycardia.

A 37 year old man with no evidence of structural heart disease presented with paroxysmal atrial tachycardia that could not be induced in the electrophysiology laboratory. Epicardial and endocardial mapping of the tachycardia performed in the operating room showed earliest activation at the junction of the right superior pulmonary vein and left atrium. An encircling incision excluded the portion of the left atrium containing the earliest point of activation and both right pulmonary veins from the remainder of the left atrium. The edges of the incision were then reapproximated. The patient is free of arrhythmias 6 months later. This technique should prove useful for the management of arhythmias arising from parts of the atria that are difficult to excise.

Vulnerability of patients with obstructive hypertrophic cardiomyopathy to ventricular arrhythmia induction in the operating room. Analysis of 17 patients.

To evaluate vulnerability to ventricular arrhythmia induction, programmed electrical stimulation was performed in the operating room in 17 consecutive patients undergoing myotomy-myectomy for obstructive hypertrophic cardiomyopathy (HC). A control group of 5 patients undergoing coronary artery bypass grafting with normal left ventricular function and no previous myocardial infarction also was tested. Of the 17 patients with HC, 14 had inducible sustained ventricular tachycardia (VT) or ventricular fibrillation (VF), 1 had inducible unsustained VT and the remaining 2 had less than 6 ventricular beats. In contrast, none of the 5 control patients had an inducible sustained ventricular arrhythmia, 1 had inducible unsustained VT, and the remaining 4 had less than 3 ventricular beats. The difference between the 2 groups with respect to induction of a sustained ventricular arrhythmia, unsustained VT or less than 6 ventricular beats was significant (p less than 0.001). It is concluded that patients with severe obstructive HC are unusually vulnerable to ventricular arrhythmia induction. This suggests that spontaneous ventricular tachyarrhythmias may be an important cause of sudden death in patients with HC.

Reduced mortality in murine cytomegalovirus infected mice following prophylactic murine interferon-gamma treatment.

Efficacy of recombinant DNA-derived murine IFN-gamma was investigated in a murine model of cytomegalovirus infection. Treatment of 3-week-old Swiss Webster mice with murine IFN-gamma prior to infection with murine cytomegalovirus (MCMV) significantly reduced mortality due to MCMV infection. Efficacy was dose-dependent and was observed using either intraperitoneal or intramuscular injection as the route of administration. Two doses, one at 24 h and one at 4 h prior to MCMV infection, were required for optimum efficacy, and doses administered after MCMV infection had no apparent effect. Reduced infectious MCMV titers were observed in critical organs of IFN-gamma treated mice and histopathologic lesions induced by MCMV infection were in general less severe and resolved sooner than lesions in untreated mice. Results in this murine model of cytomegalovirus infection suggest that IFN-gamma treatment may be useful as prophylactic therapy for human cytomegalovirus infections when a high probability of exposure to the virus exists and consequences of infection may be severe.

Effects of tumor necrosis factor-alpha treatment on mortality in murine cytomegalovirus-infected mice.

The effects of treatment with recombinant DNA-derived Tumor Necrosis Factor-alpha (TNF-alpha) in a murine model of cytomegalovirus infection were investigated. Treatment of 3-week-old Swiss Webster mice with murine TNF-alpha prior to infection with murine cytomegalovirus (MCMV) had no demonstrable effect on mortality. However, if mice were treated prior to infection with a combination of murine IFN-gamma and murine TNF-alpha, the dose of IFN-gamma required to achieve significant reduction in mortality was reduced by a factor > 10. In contrast to the beneficial effects of prophylactic TNF-alpha treatment in combination with IFN-gamma, TNF-alpha treatment of mice after MCMV infection resulted in increased mortality. The increased mortality occurred when nonlethal doses of TNF-alpha were used and required virus replication. The effects of TNF-alpha treatment on mortality in MCMV-infected mice were not predicted from cell culture experiments which evaluated the effects of TNF-alpha treatment on MCMV replication in primary mouse embryo fibroblasts.