Chemotactic activity of serum obtained from patients with idiopathic dilated cardiomyopathy

Elevated circulating levels of alpha- and beta-chemokines in heart failure have been reported. The objective of this study was to investigate the interrelation of chemotactic activity of serum and circulating chemokine levels in patients suffering from idiopathic dilated cardiomyopathy (IDCM). Chemokine serum levels (MCP-1, MIP1-alpha, RANTES, IL-8 and TNF-alpha) were determined in patients with IDCM (n = 10), patients with coronary artery disease with normal (CAD-1; n = 10) or depressed (CAD-2; n = 10) left ventricular function and healthy controls (n = 10). The chemotactic effect of sera obtained from these groups was measured using an in vitro chemotaxis assay. Sera obtained from IDCM (5475 +/- 681 cells) showed the highest chemotactic activity when compared to controls (1850 +/- 215 cells), CAD-1 (3325 +/- 275 cells) and CAD-2 (2800 +/- 275 cells, P < 0.05) associated with significantly higher circulating MCP-1 levels. Sera obtained from IDCM patients show a high chemotactic activity associated with significantly elevated circulating MCP-1.

Differences in inducibility and prognosis of in-hospital versus out-of-hospital identified nonsustained ventricular tachycardia in patients with coronary artery disease: clinical and trial design implications

OBJECTIVES

The goal of this study was to describe the influence of the clinical setting (in-hospital vs. out-of-hospital) in which nonsustained ventricular tachycardia (NSVT) is discovered on the rate of inducibility of sustained ventricular tachycardia (VT), arrhythmic events and survival in patients with coronary artery disease (CAD) and left ventricular (LV) dysfunction.

BACKGROUND

In-hospital presentation of sustained VT is independently associated with lower long-term overall survival. The impact of the clinical setting in which NSVT is documented is unknown.

METHODS

In the Multicenter Unsustained Tachycardia Trial (MUSTT), designed to assess the benefit of randomized antiarrhythmic therapy guided by electrophysiologic testing in patients with asymptomatic NSVT, CAD and LV dysfunction, eligible patients were enrolled irrespective of the setting in which the index arrhythmia was discovered. In this retrospective analysis, we compared the rate of VT inducibility and outcome of MUSTT-enrolled patients with in-hospital versus out-of-hospital presentation of NSVT.

RESULTS

Monomorphic sustained VT was induced in 35% and 28% of the patients whose index NSVT occurred in-hospital and out-of-hospital, respectively (adjusted p = 0.006). Cardiac arrest or death due to arrhythmia at two- and five-year follow-ups were 14% and 28% for untreated patients with in-hospital-identified NSVT and 11% and 21% for the out-of-hospital group (adjusted p = 0.10). Overall mortality rates at two- and five-year follow-ups were 24% and 48% for inpatients and 18% and 38% for outpatients (adjusted p = 0.018). In patients randomized to antiarrhythmic therapy, there was no significant interaction between patient status (in-hospital vs. out-of-hospital) and treatment impact on the rates of total mortality (p = 0.98) and arrhythmic events (p = 0.08).

CONCLUSIONS

In patients with CAD and impaired LV function, asymptomatic NSVT identified in-hospital, compared with that identified out-of-hospital, is associated with a higher rate of induction of sustained VT and overall mortality. Therefore, in similar patients, the clinical setting in which NSVT is discovered should be taken into account when formulating patient risk, treatment and clinical trial design.

Sexual dimorphism in the electrocardiographic dynamics of human ventricular repolarization: characterization in true time domain

BACKGROUND

Previous characterizations of sex differences in ST-T waveform voltages have largely focused on amplitudes at selected time points during repolarization, subject to potential distortions from variations in heart rate (HR) or reliance on a JT-normalized time scale.

METHODS AND RESULTS

Using digitized 12-lead ECGs from 553 normal adults (426 males) with HRs confined to 60+/-1, 70+/-1, or 80+/-1 bpm, we derived X, Y, and Z lead voltages and then generated, for each HR category by sex, summary (population mean) resultant spatial vector amplitudes (ST-T(XYZ)) and instantaneous slopes (dV/dt(XYZ)) at successive 4-ms intervals following the J point. Within each HR category, there was an early intersex divergence of ST-T(XYZ) trajectories (95% CIs nonoverlapping), with men exhibiting 2- to 3-fold greater dV/dt(XYZ) values during the ST segment and achieving greater maximum T(XYZ) and dV/dt(XYZ) values than women; descending T(XYZ) limbs were relatively more concordant between sexes but still steeper in men. The early sex differences in repolarization dynamics persisted in multiple regression analyses that took into account age and a morphometric index of left ventricular mass. In men, absolute values of extrema of T(XYZ) and dV/dt(XYZ) varied inversely with HR.

CONCLUSIONS

At physiological resting HRs, the spatial ST-T vector voltage time trajectory is steeper in men than in women, beginning virtually from the J point. In addition to its mechanistic implications, the demonstration of marked sensitivity of ST-T(XYZ) and especially dV/dt(XYZ) to sex raises the possibility that these time-based, ECG-derived parameters might be informative in pathophysiological studies of ventricular repolarization.

Genotype-phenotype correlation in the long-QT syndrome: gene-specific triggers for life-threatening arrhythmias

BACKGROUND

The congenital long-QT syndrome (LQTS) is caused by mutations on several genes, all of which encode cardiac ion channels. The progressive understanding of the electrophysiological consequences of these mutations opens unforeseen possibilities for genotype-phenotype correlation studies. Preliminary observations suggested that the conditions ("triggers") associated with cardiac events may in large part be gene specific.

METHODS AND RESULTS

We identified 670 LQTS patients of known genotype (LQT1, n=371; LQT2, n=234; LQT3, n=65) who had symptoms (syncope, cardiac arrest, sudden death) and examined whether 3 specific triggers (exercise, emotion, and sleep/rest without arousal) differed according to genotype. LQT1 patients experienced the majority of their events (62%) during exercise, and only 3% occurred during rest/sleep. These percentages were almost reversed among LQT2 and LQT3 patients, who were less likely to have events during exercise (13%) and more likely to have events during rest/sleep (29% and 39%). Lethal and nonlethal events followed the same pattern. Corrected QT interval did not differ among LQT1, LQT2, and LQT3 patients (498, 497, and 506 ms, respectively). The percent of patients who were free of recurrence with ss-blocker therapy was higher and the death rate was lower among LQT1 patients (81% and 4%, respectively) than among LQT2 (59% and 4%, respectively) and LQT3 (50% and 17%, respectively) patients.

CONCLUSIONS

Life-threatening arrhythmias in LQTS patients tend to occur under specific circumstances in a gene-specific manner. These data allow new insights into the mechanisms that relate the electrophysiological consequences of mutations on specific genes to clinical manifestations and offer the possibility of complementing traditional therapy with gene-specific approaches.

Spectrum of ST-T-wave patterns and repolarization parameters in congenital long-QT syndrome: ECG findings identify genotypes

BACKGROUND

Congenital long-QT syndrome (LQTS) is caused by mutations of genes encoding the slow component of the delayed rectifier current (LQT1, LQT5), the rapid component of the delayed rectifier current (LQT2, LQT6), or the Na(+) current (LQT3), resulting in ST-T-wave abnormalities on the ECG. This study evaluated the spectrum of ST-T-wave patterns and repolarization parameters by genotype and determined whether genotype could be identified by ECG.

METHODS AND RESULTS

ECGs of 284 gene carriers were studied to determine ST-T-wave patterns, and repolarization parameters were quantified. Genotypes were identified by individual ECG versus family-grouped ECG analysis in separate studies using ECGs of 146 gene carriers from 29 families and 233 members of 127 families undergoing molecular genotyping, respectively. Ten typical ST-T patterns (4 LQT1, 4 LQT2, and 2 LQT3) were present in 88% of LQT1 and LQT2 carriers and in 65% of LQT3 carriers. Repolarization parameters also differed by genotype. A combination of quantified repolarization parameters identified genotype with sensitivity/specificity of 85%/70% for LQT1, 83%/94% for LQT2, and 47%/63% for LQT3. Typical patterns in family-grouped ECGs best identified the genotype, being correct in 56 of 56 (21 LQT1, 33 LQT2, and 2 LQT3) families with mutation results.

CONCLUSIONS

Typical ST-T-wave patterns are present in the majority of genotyped LQTS patients and can be used to identify LQT1, LQT2, and possibly LQT3 genotypes. Family-grouped ECG analysis improves genotype identification accuracy. This approach can simplify genetic screening by targeting the gene for initial study. The multiple ST-T patterns in each genotype raise questions regarding the pathophysiology and regulation of repolarization in LQTS.

Spectrum of mutations in long-QT syndrome genes. KVLQT1, HERG, SCN5A, KCNE1, and KCNE2

BACKGROUND

Long-QT Syndrome (LQTS) is a cardiovascular disorder characterized by prolongation of the QT interval on ECG and presence of syncope, seizures, and sudden death. Five genes have been implicated in Romano-Ward syndrome, the autosomal dominant form of LQTS: KVLQT1, HERG, SCN5A, KCNE1, and KCNE2. Mutations in KVLQT1 and KCNE1 also cause the Jervell and Lange-Nielsen syndrome, a form of LQTS associated with deafness, a phenotypic abnormality inherited in an autosomal recessive fashion.

METHODS AND RESULTS

We used mutational analyses to screen a pool of 262 unrelated individuals with LQTS for mutations in the 5 defined genes. We identified 134 mutations in addition to the 43 that we previously reported. Eighty of the mutations were novel. The total number of mutations in this population is now 177 (68% of individuals).

CONCLUSIONS

KVLQT1 (42%) and HERG (45%) accounted for 87% of identified mutations, and SCN5A (8%), KCNE1 (3%), and KCNE2 (2%) accounted for the other 13%. Missense mutations were most common (72%), followed by frameshift mutations (10%), in-frame deletions, and nonsense and splice-site mutations (5% to 7% each). Most mutations resided in intracellular (52%) and transmembrane (30%) domains; 12% were found in pore and 6% in extracellular segments. In most cases (78%), a mutation was found in a single family or an individual.

Tumour necrosis factor-alpha expression in idiopathic dilated cardiomyopathy: correlation to myocardial inflammatory activity

High numbers of inflammatory cells are found in a subgroup of patients with idiopathic dilated cardiomyopathy (IDCM). We hypothesized that the extent of inflammation is linked to myocardial TNF-alpha expression in human IDCM. Fourteen patients who consecutively underwent endomyocardial biopsy (EMB) were stratified into two groups-a group with low and a group with high myocardial inflammatory index (MII)-based on immunohistochemical analysis of cellular infiltration and HLA I and II expression. Myocardial TNF-alpha messenger RNA (mRNA) expression was determined by reverse transcriptase polymerase chain reaction, TNF-alpha protein was localized by immunohistochemistry and TNF-alpha serum levels were measured by EIA. IDCM patients with a high MII (n=6) showed a 1. 9-fold higher TNF-alpha mRNA expression when compared to IDCM patients with low MII (n=8, P=0.020). TNF-alpha protein was detected at perinuclear regions of cardiac myocytes and the endothelium. TNF-alpha serum levels were 3.0 (0.55) pg/ml in patients with high MII compared to 1.35 (0.20) pg/ml in patients with low MII (P=0.017). According to immunolocalization cardiac myocytes and the endothelium seem to be the major source of TNF-alpha production. Whether the elevated systemic level of TNF-alpha found in patients with high MII are elaborated by the myocardium or are produced by other tissues representing a general immune activation is not clear.

Lack of association between 27-bp repeat polymorphism in intron 4 of the endothelial nitric oxide synthase gene and the risk of coronary artery disease

The gene encoding endothelial nitric oxide synthase (ecNOS) is a candidate gene for the mediation of initial endothelial cell damage seen in arteriosclerosis. Although the association of ecNOS polymorphisms with hypertension has been studied extensively, there is little information regarding its association with coronary artery disease (CAD). We decided to study a 27 base-pair tandem repeat polymorphism in intron 4 of the ecNOS gene in 1043 individuals (413 controls, 630 patients with CAD) who consecutively underwent coronary angiography at our institution. The frequencies of the genotypes drawn from 1038 individuals were 0.69, 0.28 and 0.03 in the controls and 0.73, 0.25 and 0.02 in individulas with CAD for the ecNOS4b/b, ecNOS4b/a and ecNOS4a/a genotypes, respectively (p = n.s). There was no shift of the genotype frequencies from the expected distribution based on the Hardy-Weinberg equilibrium. Neither the rare ecNOS4a allele nor the ecNOS4a/a genotype conferred an independent risk factor for CAD in subgroups, e.g. smokers, diabetic individuals, hypertensive individuals and individuals with a low conventional risk for CAD. In five individuals we identified an additional 27-bp repeat in the ecNOS gene (ecNOS4c), which occurred heterozygous with the ecNOS4b allele (ecNOS4b/c genotype). In conclusion, the ecNOS4a allele as well as the ecNOS4a/a genotype did not show a general association with CAD in the studied European population. Even in high-risk subgroups the ecNOS4a/4a genotype did not represent an independent risk factor for CAD. In addition, the severity of CAD was not associated with the ecNOS4a allele/ecNOS4a/a genotype.

Analysis of point mutation in exon 2 of CYP2E1 gene in renal cell/urothelial cancer patients in comparison with control population

OBJECTIVE

Genetic polymorphisms of human cytochrome P450s have been implicated to be of importance for susceptibility to different cancers. Recently, a point mutation was found in the exon 2 of the CYP2E1 gene (CYP2E1*2) [Hu et al. 1997]. In order to evaluate a possible link between the point mutation in exon 2 of the CYP2E1 gene and the susceptibility to renal cell/urothelial cancer, we developed a screening method based on the polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP).

MATERIAL

DNA of peripheral white blood cells was isolated from 158 renal cell/urothelial cancer patients as well as from 150 controls.

METHOD

Primers for PCR were designed by the Primer 3 release 0.1 program. The PCR yield a product of 215 base pairs (bp), which was digested with the restriction enzyme Hha I. The DNA fragments were separated on a 3% agarose gel stained with ethidium bromide. Restriction enzyme digestion of the PCR product obtained from the wild-type DNA resulted in the appearance of a 66 bp, a 43 bp, a 40 bp, a 39 bp and a 28 bp DNA fragment. In contrast to the wild-type, the digestion of the PCR product from DNA carrying the point mutation resulted in the loss of the 39 bp and 40 bp fragments and the appearance of an additional 79 bp fragment. Therefore, the loss of one Hha I restriction site caused by a single nucleotide exchange is suitable for the identification of the point mutation in exon 2 of CYP2E1 gene.

RESULTS

However, we could not detect any point mutation in any of the 158 renal cell/urothelial cancer patients or the 150 controls. The distribution of the point mutation in exon 2 of CYP2E1 gene did not show any difference in renal cell/urothelial cancer patients and controls.

CONCLUSION

This might indicate a lack of association between this CYP2E polymorphism (CYP2E1*2) and renal cell/urothelial cancer.

Cyclic adenosine monophosphate-responsive elements are involved in the transcriptional activation of the human IL-10 gene in monocytic cells

IL-10 plays an important role in the regulation of immune responses. We and others have demonstrated recently that cyclic adenosine monophosphate (cAMP)-elevating substances up-regulate monocytic IL-10 expression in vitro and in vivo. Computer analysis of the IL-10 promoter/enhancer region localized four putative cAMP-responsive elements (CRE1- 4) with homology to the CRE consensus motif. In electrophoretic mobility shift assays CRE1 and CRE4 bound protein complexes consisting of transcription factors CREB-1 and ATF-1, while CRE3 bound only marginal amounts of CREB-1/ATF-1 in combination with unknown protein(s). CRE2 showed no protein binding activity. In vitro mutation of CRE1 and CRE4 reduced the level of cAMP-stimulated transactivation in reporter gene assays in comparison to the wild-type promoter by 20 % and 50 %, respectively, while mutation of CRE3 had no effect. The main action of CRE4 on cAMP-dependent stimulation is probably based on its adjacent localization to the TATA box and its sequence comprising a perfect half site. Experiments with double and triple mutants and with deleted promoter fragments indicated the participation of additional elements beside the CRE motifs in the cAMP-dependent stimulation. Our data suggest that intracellular cAMP may directly affect expression of the immunoregulatory cytokine IL-10 in monocytic cells via activation of the eukaryotic transcription factors CREB-1 and ATF-1 and their binding to CRE1 and CRE4 in the upstream enhancer of the IL-10 promoter.

MiRP1 forms IKr potassium channels with HERG and is associated with cardiac arrhythmia

A novel potassium channel gene has been cloned, characterized, and associated with cardiac arrhythmia. The gene encodes MinK-related peptide 1 (MiRP1), a small integral membrane subunit that assembles with HERG, a pore-forming protein, to alter its function. Unlike channels formed only with HERG, mixed complexes resemble native cardiac IKr channels in their gating, unitary conductance, regulation by potassium, and distinctive biphasic inhibition by the class III antiarrhythmic E-4031. Three missense mutations associated with long QT syndrome and ventricular fibrillation are identified in the gene for MiRP1. Mutants form channels that open slowly and close rapidly, thereby diminishing potassium currents. One variant, associated with clarithromycin-induced arrhythmia, increases channel blockade by the antibiotic. A mechanism for acquired arrhythmia is revealed: genetically based reduction in potassium currents that remains clinically silent until combined with additional stressors.

Prediction of sustained ventricular tachycardia inducible by programmed stimulation in patients with coronary artery disease. Utility of clinical variables

BACKGROUND

Cardiologists often use clinical variables to determine the need for electrophysiological studies to stratify patients for risk of sudden death. It is not clear whether this is rational in patients with coronary artery disease, left ventricular dysfunction, and nonsustained ventricular tachycardia.

METHODS AND RESULTS

We analyzed the first 1721 patients enrolled in the Multicenter UnSustained Tachycardia Trial to determine whether clinical variables could predict which patients would have inducible sustained monomorphic ventricular tachycardia. The rate of inducibility of sustained ventricular tachycardia was significantly higher in patients with a history of myocardial infarction and in men compared with women. There was a progressively increased rate of inducibility with increasing numbers of diseased coronary arteries. There was a significantly lower rate of inducibility in patients with prior coronary artery bypass surgery and in patients who also had noncoronary cardiac disease. The rate of inducibility was higher in patients of white race, patients with recent (</=6 weeks) angina, left ventricular dyskinesis, and in patients with greater numbers of fixed thallium defects. Inducibility was more likely in patients who had a prior myocardial infarction complicated by congestive heart failure, ventricular tachycardia, or fibrillation </=48 hours after the onset of infarction. Although these associations are statistically significant, the accuracy of the clinical variables in discriminating between patients with and those without inducible ventricular tachycardia is only modest (receiver operator characteristic area <0.70).

CONCLUSIONS

Multiple clinical variables are independently associated with inducible sustained ventricular tachycardia. However, they have limited utility to guide clinical decisions regarding the use of electrophysiological testing for risk stratification in this patient population.

JTc prolongation with d,l-sotalol in women versus men

Women are at increased risk for torsades de pointes associated with a variety of drugs that prolong ventricular repolarization, but few data exist regarding possible sex differences in extent of repolarization changes with these medications. We sought to compare JTc interval responses in women and men during treatment with d,l-sotalol. The study cohort consisted of 1,897 patients (26% women) with available baseline and > or =1 on-drug electrocardiogram from a database involving patients exposed to oral d,l-sotalol without developing torsades de pointes. The mean lowest and highest daily d,l-sotalol dose, normalized for weight, was not significantly different between sexes. At each dosing extreme, on-drug JTc was significantly longer in women (p < or =0.0002). Statistically independent predictors of on-drug JTc included gender (p = 0.003), baseline JTc (p = 0.0001), dose (p = 0.0001), serum creatinine (p < or =0.03), and history of sustained ventricular tachyarrhythmias (p = 0.01). In both men and women, as baseline JTc increased, the drug-induced increment in JTc became progressively smaller. Thus, in response to d,l-sotalol, JTc intervals become longer in women than in men. This sex difference is independent of dose and not solely attributable to the known gender disparity in baseline JTc. The greater propensity of women to drug-induced torsades de pointes may represent the most extreme expression of a basic sex difference in the response to medications that prolong ventricular repolarization.

Sudden death in implantable cardioverter-defibrillator recipients: clinical context, arrhythmic events and device responses

OBJECTIVES

We sought to investigate the nature of terminal events and potential contributory clinical and nonclinical (e.g., device-related) factors associated with sudden death (SD) in recipients of an implantable cardioverter-defibrillator (ICD).

BACKGROUND

The ICD is very effective in terminating ventricular tachycardia (VT) or ventricular fibrillation (VF), but protection against SD is not absolute. Little is known about the nature and potential causes of SD in patients with ICDs.

METHODS

We analyzed 25 cases of out-of-hospital SD among patients enrolled in the clinical investigation of the Cadence Tiered-Therapy Defibrillator System.

RESULTS

All patients (24 men and 1 woman, mean age 62+/-10 years) received epicardial lead systems. The majority (92%) had coronary artery disease and a previous myocardial infarction (MI), with a mean left ventricular ejection fraction 0.25+/-0.07. At device implantation, the mean defibrillation threshold was 13+/-5 J. Sudden death occurred 13+/-11 months later. Twenty patients (80%) had received appropriate ICD therapies before death, and 18 (72%) were receiving > or = 1 antiarrhythmic drugs at the time of death. Sudden death was tachyarrhythmia-associated in 16 patients (64%), non-tachyarrhythmia-associated in 7 (28%) and indeterminate in 2 (8%). In the 16 patients with tachyarrhythmia-associated SD, the overall first therapy success rate in tachycardia and fibrillation zones was 60% and 67%, respectively. However, despite protracted therapies (> or = 2 shocks) in 7 (66%) of 12 patients who received fibrillation therapies, the final tachyarrhythmic episode was ultimately terminated by the ICD in 15 (94%) of the 16 patients, whereas 1 patient died after multiple (initially successful) internal and external shocks for intractable VT/VF during exercise. In 10 patients (40%) one or more, primarily clinical, factors potentially contributory to SD were identified: heart failure (n=8), angina (n=2), hypokalemia (n=1), adverse antiarrhythmic drug treatment (n=1) and acute MI (n=1). An additional 10 patients (40%) had experienced an increase in frequency of ICD shocks within 3 months of SD. Appropriate battery voltages and normal circuitry function were found in all devices interrogated and analyzed after death.

CONCLUSIONS

In this select group of patients receiving a third-generation ICD, SD was associated with VT or VF events in nearly two-thirds of patients, and death occurred despite ultimately successful, although often protracted, device therapies. These observations, along with evidence of recent worsening clinical status, suggest acute cardiac mechanical dysfunction as a frequent terminal factor. In recipients with ICDs, SD directly attributable to device failure seems to be rare.

Monocyte chemoattractant protein 1 (MCP-1) gene expression in dilated cardiomyopathy

The cytotoxic action of leukocytes may be a most probable cause of cardiac myocyte damage seen in chronic myocarditis and dilated cardiomyopathy (DCM). The migration and tissue infiltration of leukocytes is regulated by chemotactic cytokines. Recently, the presence of monocyte chemoattractant protein 1 (MCP-1) messenger RNA has been demonstrated in endomyocardial biopsy tissue obtained from patients with DCM. This chemokine could contribute to enhanced leukocyte recruitment and activation resulting in chronic damage of cardiomyocytes. Accordingly, we sought to determine whether the severity of left ventricular dysfunction in DCM is associated with quantitative alterations of MCP-1 messenger RNA and MCP-1 protein in endomyocardial biopsy tissue. A group of DCM patients with low to moderate impairment of left ventricular function (ejection fraction 45.3+/-2.3%, n=7) was compared to patients with severe left ventricular dysfunction (ejection fraction 25.5+/-3.1%, n=7). MCP-1 messenger RNA expression was determined by quantitative polymerase chain reaction. MCP-1 protein and the presence of infiltrating inflammatory cells were detected by immunohistochemistry. DCM patients with severe left ventricular dysfunction showed a 2.35 fold higher MCP-1 messenger RNA expression when compared to DCM patients with less severe dysfunction (P=0.0229). Positive immunohistochemical staining for MCP-1 was found in all seven patients with severe left ventricular dysfunction and was particularly distinct within the cardiac interstitum. In five of seven patients with less severe systolic dysfunction, MCP-1 protein was found, but was less pronounced and distributed in patchy interstitial areas, close to intramyocardial vessels. Furthermore, there was a consistent trend toward a higher infiltration of inflammatory cells in DCM patients with lower ejection fraction. In conclusion, MCP-1 is dynamically regulated in DCM related deterioration of left ventricular function. This mechanism might contribute to myocyte damage via infiltrated and activated monocytes.

Influence of the genotype on the clinical course of the long-QT syndrome. International Long-QT Syndrome Registry Research Group

BACKGROUND

The congenital long-QT syndrome, caused by mutations in cardiac potassium-channel genes (KVLQT1 at the LQT1 locus and HERG at the LQT2 locus) and the sodium-channel gene (SCN5A at the LQT3 locus), has distinct repolarization patterns on electrocardiography, but it is not known whether the genotype influences the clinical course of the disease.

METHODS

We determined the genotypes of 541 of 1378 members of 38 families enrolled in the International Long-QT Syndrome Registry: 112 had mutations at the LQT1 locus, 72 had mutations at the LQT2 locus, and 62 had mutations at the LQT3 locus. We determined the cumulative probability and lethality of cardiac events (syncope, aborted cardiac arrest, or sudden death) occurring from birth through the age of 40 years according to genotype in the 246 gene carriers and in all 1378 members of the families studied.

RESULTS

The frequency of cardiac events was higher among subjects with mutations at the LQT1 locus (63 percent) or the LQT2 locus (46 percent) than among subjects with mutations at the LQT3 locus (18 percent) (P<0.001 for the comparison of all three groups). In a multivariate Cox analysis, the genotype and the QT interval corrected for heart rate were significant independent predictors of a first cardiac event. The cumulative mortality through the age of 40 among members of the three groups of families studied was similar; however, the likelihood of dying during a cardiac event was significantly higher (P<0.001) among families with mutations at the LQT3 locus (20 percent) than among those with mutations at the LQT1 locus (4 percent) or the LQT2 locus (4 percent).

CONCLUSIONS

The genotype of the long-QT syndrome influences the clinical course. The risk of cardiac events is significantly higher among subjects with mutations at the LQT1 or LQT2 locus than among those with mutations at the LQT3 locus. Although cumulative mortality is similar regardless of the genotype, the percentage of cardiac events that are lethal is significantly higher in families with mutations at the LQT3 locus.

CYP2E1 genotyping in renal cell/urothelial cancer patients in comparison with control populations

OBJECTIVE

Genetic polymorphisms in enzymes involved in carcinogen metabolism have been found to influence susceptibility to cancer. Ethanol-inducible CYP2E1 is an enzyme of major toxicological interest because it metabolizes several drugs, precarcinogens, and solvents to reactive metabolites. In the present investigation, we studied the cytochrome P450 2E1 genetic polymorphism in renal cell/urothelial cancer patients in comparison with healthy control populations in the regions of Jena and Halle in Germany.

PATIENTS AND MATERIAL

DNA of peripheral white blood cells was isolated both from 273 renal cell/urothelial cancer patients and 298 controls from the regions of Jena and Halle.

METHOD

We focused on polymorphisms in the promoter region and intron 6 of the CYP2E1 gene. The polymorphims were identified as restriction fragment length polymorphisms (RFLPs) by polymerase chain reaction (PCR) and subsequently applying the restriction enzymes PstI/RsaI and DraI.

RESULTS

In the region of Jena as well as of Halle, the frequency distributions of the PstI/RsaI, DraI, and combined DraI + PstI/RsaI genotypes showed no significant differences between controls and renal cell/urothelial cancer patients. We did not find significant differences between Jena and Halle. 86.7% of all subjects with a homozygote PstI/RsaI genotype also carried a homozygote DraI genotype, whereas 5.2% of all subjects with a heterozygote PstI/RsaI genotype also carried a heterozygote DraI genotype. The heterozygote genotype of PstI/RsaI polymorphism always determines the heterozygote genotype of DraI polymorphism. Our results failed to demonstrate any differences in the distribution of CYP2E1 polymorphisms between renal cell/urothelial cancer patients and controls.

CONCLUSION

Summing up, our results show that CYP2E1 genotype cannot predict risk for renal cell/urothelial cancer in the population from 2 different regions in Germany. The results demonstrate a lack of association between CYP2E1 genetic polymorphism and renal cell cancer/urothelial cancer.

Impact of CYP2E1 genotype in renal cell and urothelial cancer patients

Genetic polymorphisms of enzymes involved in carcinogen metabolism have been found to influence susceptibility to cancer. Ethanol-inducible CYP2E1 is an enzyme of major toxicological interest because it metabolizes several drugs, precarcinogens and solvents to reactive metabolites. In the present study, we investigated the cytochrome P450 2E1 genetic polymorphism in renal cell/urothelial cancer patients from two German regions, Jena and Halle, different with respect to their environmental pollution degree in comparison with healthy controls from the same regions. DNA of peripheral white blood cells was isolated both from 224 renal cell/urothelial cancer patients and 304 controls. We focussed on polymorphisms in the promoter region and intron 6 of the CYP2E1 gene. The polymorphisms were identified as RFLP's by amplification of the appropriate DNA fragment and subsequent digestion with the restriction enzymes PstI, RsaI and DraI. In Jena as well as in Halle, the frequency distributions of the PstI/RsaI, DraI and combined DraI + PstI/RsaI genotypes showed no significant differences between controls and renal cell/urothelial cancer patients. We did not find significant differences between Jena and Halle. 86.2% of all subjects with a homozygote PstI/RsaI genotype also carried a heterozygote DraI genotype, whereas 5.1% of the subjects with a heterozygote PstI/RsaI genotype also carried a heterozygote DraI genotype. Renal cell cancer as well as urothelial cancer risk was not elevated in patients with heterozygote DraI, PstI/RsaI and combined DraI + PstI/RsaI genotypes (odds ratios slightly insignificantly increased). Interestingly enough, an association between these polymorphisms and renal cell cancer risk was found in the female subgroup but not in the male subgroup. The basis of these sex-specifically increased risks are different frequencies concerning heterozygote and homozygote genotypes in controls and cancer patients. In controls, the heterozygote genotype frequency was lower in females than in males. In renal cell cancer patients, the results were quite the contrary. Summing up, our results demonstrate an lack between CYP2E1 genetic polymorphism and renal cell/urothelial cancer risk.

Androgen receptors mediate hypertrophy in cardiac myocytes

BACKGROUND

The role of androgens in producing cardiac hypertrophy by direct action on cardiac myocytes is uncertain. Accordingly, we tested the hypothesis that cardiac myocytes in adult men and women express an androgen receptor gene and that myocytes respond to androgens by a hypertrophic response.

METHODS AND RESULTS

We used reverse transcription-polymerase chain reaction methods to demonstrate androgen receptor transcripts in multiple tissues and [3H]phenylalanine incorporation and atrial natriuretic peptide secretion as markers of hypertrophy in cultured rat myocytes. Messenger RNA encoding androgen receptors was detected in myocytes of male and female adult rats, neonatal rat myocytes, rat heart, dog heart, and infant and adult human heart. Both testosterone and dihydrotestosterone produced a robust receptor-specific hypertrophic response in myocytes, determined by indices of protein synthesis and atrial natriuretic peptide secretion.

CONCLUSIONS

Androgen receptors are present in cardiac myocytes from multiple species, including normal men and women, in a context that permits androgens to modulate the cardiac phenotype and produce hypertrophy by direct, receptor-specific mechanisms. There are clinical implications for therapeutic or illicit use of androgens in humans.

Genomic structure of three long QT syndrome genes: KVLQT1, HERG, and KCNE1

Long QT syndrome (LQT) is a cardiac disorder causing syncope and sudden death from arrhythmias. LQT is characterized by prolongation of the QT interval on electrocardiogram, an indicationof abnormal cardiac repolarization. Mutations in KVLQT1, HERG, SCN5A, and KCNE1, genes encoding cardiac ion channels, cause LQT. Here, we define thecomplete genomic structure of three LQT genesand use this information to identify disease-associated mutations. KVLQT1 is composed of 16 exonsand encompasses approximately 400 kb. HERG consists of 16 exons and spans 55 kb. Three exons make up KCNE1. Each intron of these genes contains the invariant GT and AG at the donor and acceptor splice sites, respectively. Intron sequences were used to design primer pairs for the amplification of all exons. Familial and sporadic cases affected bymutations in KVLQT1, HERG, and KCNE1 can nowbe genetically screened to identify individuals at risk of developing this disorder. This work has clinical implications for presymptomatic diagnosis and therapy.

Age- and sex-related differences in clinical manifestations in patients with congenital long-QT syndrome: findings from the International LQTS Registry

BACKGROUND

Unexplained female predominance is observed in long-QT syndrome (LQTS), a congenital autosomal disorder with prolonged repolarization and syncope or sudden death due to ventricular tachyarrhythmias. Our objectives were to evaluate age- and sex-related differences in events among LQTS patients referred to the LQTS International Registry.

METHODS AND RESULTS

Age- and sex-related occurrence of events was analyzed in 479 probands (70% females) and 1041 affected family members (QTc >440 ms, 58% females). LQTS-gene mutations were identified in 162 patients: 69 LQT1 carriers (KVLQT1 on 11p15.5), 62 LQT2 carriers (HERG on 7q35-36), and 31 LQT3 carriers (SCN5A on 3p21-24). Females predominated among 366 probands (71% females) and 230 symptomatic family members (62% females). Male probands were younger than females at first event (8+/-7 versus 14+/-10 years, P<0.0001) and had higher event rates by age 15 years than females (74% versus 51%, P<0.0001). Affected family members had similar findings. By Cox analysis adjusting for QTc duration, the hazard ratio for female probands of experiencing events by age 15 years was 0.48 (P<0.001), and it was 1.87 (P=0.09) by age 15 to 40 years. In female family members, the hazard ratio was 0.58 (P<0.001) by age 15 years, and it was 3.25 (P<0.001) by age 15 to 40 years. The event rate was higher in male than female LQT1 carriers (69% versus 32%, P=0.001). No age-sex difference in event rate was detected in LQT2 and LQT3 carriers.

CONCLUSIONS

Among LQTS patients, the risk of cardiac events was higher in males until puberty and higher in females during adulthood. The same pattern was evident among LQT1 gene carriers. Unknown sex factors modulate QT duration and arrhythmic events, with preliminary evidence of gene-specific differences in age-sex modulation.

Recombinant human granulocyte-macrophage colony-stimulating factor triggers interleukin-10 expression in the monocytic cell line U937

GM-CSF is a cytokine with pleiotropic biological activities and is increasingly used in clinical trials. The present study demonstrates the ability of recombinant human granulocyte-macrophage colony-stimulating factor (rGM-CSF) to induce elevation of interleukin-10 (IL-10) mRNA and protein production in the monocytic cell line U937. As shown by a semiquantitative reverse transcriptase-polymerase chain reaction (RT-PCR), IL-10 mRNA increases up to 10 times when stimulated with rGM-CSF (100 U/ml) compared to nonstimulated control cells. Maximal IL-10 mRNA expression occurs at 6 h and remains high for 2 h. Thereafter IL-10 mRNA is downregulated and reaches basal level at approximately 24 h. IL-10 protein was measured by ELISA. The protein yield is dose-dependent on the rGM-CSF concentration. Combined stimulation of U937 cells with both GM-CSF and TNF-alpha results in an additive elevation of the IL-10 protein yield. Application of a neutralising antibody against TNF-alpha revealed that GM-CSF induces IL-10 expression independently from TNF-alpha. By using a luciferase reporter gene it was shown that rGM-CSF enhances IL-10 promoter activity 2-3-fold in a transient transfection assay.

Interleukin-10 expression is induced by increase of intracellular calcium levels in the monocytic cell line U937

The regulation of interleukin-10 (IL-10) expression after treatment with a high, exponential, electric pulse was investigated in the monocytic cell line U937. Recently, we showed IL-10 protein production in the monocytic cell lines U937 and THP-1 after exposure to a single, high exponential electric pulse [Lehmann MH, Höffken K, Berg H (1996) Bioelectrochem. Bioenerg. 41: 227-229]. In the present study, the specificity of this process was proven by semiquantitative reverse-transcriptase polymerase chain reaction. It was found that the presence of calcium in the culture medium during the pulse is essential for IL-10 protein production. Only a small amount of IL-10 protein was produced in calcium free medium. The calcium specific chelator EGTA prevented IL-10 protein production induced by the electric pulse in a dose-dependent manner. Additionally, IL-10 mRNA transcription could be induced in U937 cells without pulse application by means of the calcium ionophore ionomycin. No IL-10 protein could be detected by ELISA. However, down-regulation of TNF-alpha mRNA levels after ionomycin stimulation provided an indirect proof that IL-10 protein production occurred.

New mutations in the KVLQT1 potassium channel that cause long-QT syndrome

BACKGROUND

Long-QT syndrome (LQTS) is an inherited cardiac arrhythmia that causes sudden death in young, otherwise healthy people. Four genes for LQTS have been mapped to chromosome 11p15.5 (LQT1), 7q35-36 (LQT2), 3p21-24 (LQT3), and 4q25-27 (LQT4). Genes responsible for LQT1, LQT2, and LQT3 have been identified as cardiac potassium channel genes (KVLQT1, HERG) and the cardiac sodium channel gene (SCN5A).

METHODS AND RESULTS

After studying 115 families with LQTS, we used single-strand conformation polymorphism (SSCP) and DNA sequence analysis to identify mutations in the cardiac potassium channel gene, KVLQT1. Affected members of seven LQTS families were found to have new, previously unidentified mutations, including two identical missense mutations, four identical splicing mutations, and one 3-bp deletion. An identical splicing mutation was identified in affected members of four unrelated families (one Italian, one Irish, and two American), leading to an alternatively spliced form of KVLQT1. The 3-bp deletion arose de novo and occurs at an exon-intron boundary. This results in a single base deletion in the KVLQT1 cDNA sequence and alters splicing, leading to the truncation of KVLQT1 protein.

CONCLUSIONS

We have identified LQTS-causing mutations of KVLQT1 in seven families. Five KVLQT1 mutations cause the truncation of KVLQT1 protein. These data further confirm that KVLQT1 mutations cause LQTS. The location and character of these mutations expand the types of mutation, confirm a mutational hot spot, and suggest that they act through a loss-of-function mechanism or a dominant-negative mechanism.

Mutations in the hminK gene cause long QT syndrome and suppress IKs function

Ion-channel beta-subunits are ancillary proteins that co-assemble with alpha-subunits to modulate the gating kinetics and enhance stability of multimeric channel complexes. Despite their functional importance, dysfunction of potassium-channel beta-subunits has not been associated with disease. Recent physiological studies suggest that KCNE1 encodes beta-subunits (hminK) that co-assemble with KvLQT1 alpha-subunits to form the slowly activating delayed rectifier K+ (IKs) channel. Because KVLQT1 mutations cause arrhythmia susceptibility in the long QT syndrome (LQT), we hypothesized that mutations in KCNE1 also cause this disorder. Here, we define KCNE1 missense mutations in affected members of two LQT families. Both mutations (S74L, D76N) reduced IKs by shifting the voltage dependence of activation and accelerating channel deactivation. D76N hminK also had a strong dominant-negative effect. The functional consequences of these mutations would be delayed cardiac repolarization and an increased risk of arrhythmia. This is the first description of KCNE1 as an LQT gene and confirms that hminK is an integral protein of the IKs channel.

Implantable cardioverter defibrillator utilization among device recipients presenting exclusively with syncope or near-syncope

INTRODUCTION

Implantable cardioverter defibrillators (ICDs) are occasionally used in presumed high-risk patients with electrocardiographically undocumented syncope, although the incidence of ventricular tachyarrhythmias in this population is not well defined.

METHODS AND RESULTS

We studied 33 consecutive patients receiving an ICD (67% nonthoracotomy and 70% tiered therapy) after electrophysiologic testing for unmonitored "syncope" (n = 29) or "near-syncope" (n = 4). Atherosclerotic heart disease was present in 24 (73%); mean left ventricular ejection fraction (LVEF) was 0.39 +/- 0.15; and sustained monomorphic ventricular tachycardia (SMVT) was inducible in 18 (55%). Over a median follow-up of 17 months (range 4 to 61), 12 patients (36%) received > or = 1 appropriate ICD discharge triggered by SMVT (cycle length 230 to 375 msec) in 10 and ventricular flutter or fibrillation in 2--without concomitant antiarrhythmic medication in 8 of 12 cases. Inducible SMVT and LVEF < or = 0.35 were statistically significant, independent predictors of an appropriate ICD discharge (P < 0.02 and P < 0.03, respectively). Estimated 1-year cumulative survival free of appropriate discharge was 34% versus 87%, respectively, in patients with versus without inducible SMVT (P < 0.02), and 18% versus 56%, respectively, in patients with LVEF < or = 0.35 versus LVEF > 0.35 (P < 0.03).

CONCLUSION

In this highly select, multicenter population of ICD recipients with electrocardiographically undocumented syncope, a substantial incidence of appropriate device discharges was observed, particularly in patients with inducible SMVT and LVEF < or = 0.35. These findings support the notion that, in patients with LV dysfunction and inducible SMVT, ventricular tachyarrhythmias are likely to account for episodes of syncope or near-syncope.

Maximal ascending and descending slopes of the T wave in men and women

To investigate possible sex differences in the dynamics of T wave generation, the maximum instantaneous slope of the ascending and descending limbs of the T wave (max dV/dt and min dV/dt, respectively), were calculated. These rate of repolarization parameters, as well as more traditional repolarization duration parameters (QT, JT, Q to T wave peak [QTm] and J to T wave peak [JTm]), were measured by computer using digitized electrocardiograms (ECGs) from the V5 lead in 562 normal subjects (443 men and 119 women; mean age 37 years), whose heart rates (HRs) were confined to one of three narrow ranges, namely 60 +/- 1, 70 +/- 1, or 80 +/- 1 beats/min. In both men and women, for each HR range absolute values of min dV/dt exceeded those of max dV/dt (P < .0001). However, absolute values of both max dV/dt and min dV/dt were consistently greater in men than in women for each HR range (P < .0001 at HR 60 +/- 1; P < .02 at HR 70 +/- 1, or 80 +/- 1). By using correlation analysis, max dV/dt and min dV/dt were shown to be independent of the repolarization duration variables (r < .30). Thus, whereas in both men and women the descending limb of the T wave is steeper than the ascending limb, the maximum slope of each limb of the T wave is steeper in men than in women. These findings add to a growing body of data indicating fundamental sex differences in the physiology of cardiac repolarization and propensity to torsade de pointes.

Ventriculoatrial conduction capability and prevalence of 1:1 retrograde conduction during inducible sustained monomorphic ventricular tachycardia in 305 implantable cardioverter defibrillator recipients

Despite the advent of dual chamber ICDs, differentiation of VT (SMVT) with 1:1 VA conduction will remain a challenge. In this study, VA conduction capability and prevalence of inducible sustained monomorphic (SM) VT with 1:1 VA conduction was assessed in 305 ICD recipients. SMVT with a mean cycle length (CL) of 304 +/- 61 ms was induced in 161 (53%) patients. Twenty-six percent of the patients maintained 1:1 VA conduction to CL < or = 400 ms during incremental ventricular pacing, regardless of presenting tachyarrhythmia or presence of inducible SMVT. Among ten patients who had inducible SMVT with possible 1:1 VA conduction (based on SMVT CL comparable to the shortest CL associated with 1:1 retrograde conduction during ventricular pacing), all seven with available intracardiac tracings had documented 1:1 VA conduction during the induced SMVT--representing 4.4% of the patients with inducible SMVT (95% CI 1.2%-7.6%), and 2.3% of the entire ICD cohort (95% CI 0.6%-4.0%). We conclude that about one-fifth of ICD recipients possess 1:1 VA conduction to CL < or = 400 ms and that inducible SMVT with 1:1 VA conduction can be demonstrated in a small but nonnegligible proportion of ICD recipients. These data are relevant to the design of tachyarrhythmia-discrimination algorithms for dual chamber ICDs.

Does subclinical hypothyroidism explain the increased susceptibility of women to torsades de pointes?

Among 20 consecutive patients (65% women) with drug-associated torsades de pointes, chemical evidence for hypothyroidism was found in only 10% of both women and men. Subclinical hypothyroidism is therefore unlikely to account for the consistently observed sex difference in the propensity to torsades de pointes.

Unrecognized paroxysmal supraventricular tachycardia. Potential for misdiagnosis as panic disorder

BACKGROUND

The diagnostic criteria for panic disorder include symptoms commonly experienced by patients with paroxysmal supraventricular tachycardia (PSVT). Since electrocardiographic documentation of PSVT can be elusive, symptoms may be ascribed to other conditions.

OBJECTIVE

To systematically evaluate the potential for PSVT to simulate panic disorder.

METHODS

A retrospective survey of 107 consecutive patients with reentrant PSVT was conducted. Objective and subjective assessments of PSVT symptomatology were made, including the application of the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV), panic disorder criteria.

RESULTS

The criteria for panic disorder according to DSM-IV were fulfilled by 67% of patients. Paroxysmal supraventricular tachycardia was unrecognized after initial medical evaluation in 59 patients (55%), including 13 (41%) of 32 patients with ventricular preexcitation by electrocardiogram, and remained unrecognized for a median of 3.3 years. Prior to eventual identification of PSVT, physicians (nonpsychiatrists) attributed symptoms to panic, anxiety, or stress in 32 (54%) of the 59 patients. When PSVT was unrecognized, women were more likely than men to have symptoms ascribed to psychiatric origins (65% vs 32%, respectively; P < .04). Paroxysmal supraventricular tachycardia was detected in only 6 (9%) of 64 patients undergoing Holter monitoring vs 8 (47%) of 17 patients who wore an event monitor (P < .001). During a 20-month median follow-up, electrophysiologically guided therapy (ablation in 81% of patients) resolved symptoms in 86% of patients; only 4% continued to meet DSM-IV panic disorder criteria without evidence of PSVT recurrence.

CONCLUSIONS

The clinical characteristics of patients with PSVT referred for electrophysiologically guided therapy can mimic panic disorder. Diagnosis of PSVT is often delayed by inappropriate rhythm detection techniques (Holter instead of event monitoring) and failure to recognize ventricular preexcitation on the sinus electrocardiogram; symptoms due to unrecognized PSVT are often ascribed to psychiatric conditions.

Age-gender influence on the rate-corrected QT interval and the QT-heart rate relation in families with genotypically characterized long QT syndrome

OBJECTIVES

We sought to analyze age-gender differences in the rate-corrected QT (QTc) interval in the presence of a QT-prolonging gene.

BACKGROUND

Compared with men, women exhibit a longer QTc interval and an increased propensity toward torsade de pointes. In normal subjects, the QTc gender difference reflects QTc interval shortening in men during adolescence.

METHODS

QTc intervals were analyzed according to age (< 16 or > or = 16 years) and gender in 460 genotyped blood relatives from families with long QT syndrome linked to chromosome 11p (KVLQT1; n = 199), 7q (HERG; n = 208) or 3p (SCN5A; n = 53).

RESULTS

The mean QTc interval in genotype-negative blood relatives (n = 240) was shortest in men, but similar among women, boys and girls. For genotype-positive blood relatives, men exhibited the shortest mean QTc interval in chromosome 7q- and 11p-linked blood relatives (n = 194), but not in the smaller 3p-linked group (n = 26). Among pooled 7q- and 11p-linked blood relatives, multiple regression analysis identified both genotype (p < 0.001) and age-gender group (men vs. women/children; p < 0.001) as significant predictors of the QTc interval; and heart rate (p < 0.001), genotype (p < 0.001) and age-gender group (p = 0.01) as significant predictors of the absolute QT interval. A shorter mean QT interval in men was most evident for heart rates < 60 beats/min.

CONCLUSIONS

In familial long QT syndrome linked to either chromosome 7q or 11p, men exhibit shorter mean QTc values than both women and children, for both genotype-positive and -negative blood relatives. Thus, adult gender differences in propensity toward torsade de pointes may reflect the relatively greater presence in men of a factor that blunts QT prolongation responses, especially at slow heart rates.

Torsade de pointes as a complication of subarachnoid hemorrhage: a critical reappraisal

Subarachnoid hemorrhage is widely accepted as a potential cause of torsade de pointes (TdP), yet this putative etiologic relationship has never been systematically evaluated. We therefore undertook a MEDLINE search from 1966 through 1993, with relevant back referencing, and identified 20 cases of TdP in the setting of subarachnoid hemorrhage. It was impossible in any of these cases (usually because of insufficient data) to completely exclude one or more alternative explanations for TdP, including congenital long QT syndrome, hypokalemia, hypomagnesemia, or drug-induced QT prolongation. Furthermore, of a total of 1,139 patients in 16 prospective series of subarachnoid hemorrhage with electrographic analyses, there were only five reported cases of TdP, all in patients with hypokalemia. Thus, extremely limited scientific data exist to support the notion that subarachnoid hemorrhage can be a distinct cause of TdP. Until more definitive evidence is available, the development of TdP in patients with subarachnoid hemorrhage is probably better characterized as a multifactorial phenomenon occurring in an acute, typically intensive care, setting.

Sex difference in risk of torsade de pointes with d,l-sotalol

BACKGROUND

The present study was undertaken to test the hypothesis that women are more prone than men to develop torsade de pointes (TdP) in a defined cohort of patients exposed to the QT-prolonging antiarrhythmic drug d,l-sotalol.

METHODS AND RESULTS

In a database derived from 22 clinical trials involving 3135 adult patients who received oral d,l-sotalol (median follow-up, 164 days), TdP developed in 44 (1.9%) of 2336 men and in 33 (4.1%) of 799 women (P < .001). Logistic regression analysis identified female sex (P < .0001), presenting arrhythmia of sustained ventricular tachycardia or fibrillation (P < .0001), history of congestive heart failure (P < .001), and d,l-sotalol dose > 320 mg/d (P < .001) as factors most predictive of TdP; in addition to these, a serum creatinine > 1.4 mg/dL in women and > 1.6 mg/dL in men was weakly predictive (P < .05). After adjustment for these risk factors, women had threefold greater odds of developing TdP than men. The sex difference in TdP risk was age independent and could not be explained by differential dose-related bradycardic responses in women versus men.

CONCLUSIONS

Women are at increased risk of developing TdP during-administration of d,l-sotalol. This finding needs to be taken into account, together with other TdP risk factors, when patients are treated with this antiarrhythmic agent. Given the consistency between the present and other recent observations, greater caution in women regarding use of QT-prolonging drugs, in general, is advisable.

Probucol-associated tachyarrhythmic events and QT prolongation: importance of gender

From published articles and adverse reactions reports filed with the FDA (available through the Freedom of Information Act), we analyzed occurrences of tachyarrhythmias and the magnitude of QTc prolongation associated with probucol therapy. Of 16 cases of tachyarrhythmic events reported in association with probucol, 15 (94%) occurred in women (p < 0.01 vs expected value of 58%). Tachyarrhythmias were specifically described as TdP in 11 (63%) cases, all women; additional potential contributory QT-prolonging factors (besides probucol) were not identifiable in 2 of the 11 cases. We also analyzed QTc responses in 359 probucol-treated patients, all having baseline QTc < or = 0.44 sec1/2. At doses of 500 to 1000 mg/day, probucol-associated prolongation of QTc to values > or = 0.45 sec1/2 was observed in 22% of women versus 7% of men (p < 0.001) and to values > or = 0.47 sec1/2 in 8% of women versus 2% of men (p < 0.03). Multivariate analysis identified baseline QTc (p < 0.0001) and female gender (p < 0.03), but neither age nor dose, as significant independent predictors of QTc prolongation to > or = 0.45 sec1/2 with probucol. These findings have relevance to the clinical use of probucol, provide further evidence that women have a relatively greater predisposition to development of acquired long QT syndrome, and carry implications for the design of trials involving QT-prolonging drugs.

ECG T-wave patterns in genetically distinct forms of the hereditary long QT syndrome

BACKGROUND

The long QT syndrome is an inherited disorder with prolonged ventricular repolarization and a propensity to ventricular tachyarrhythmias and sudden arrhythmic death. Recent linkage studies have demonstrated three separate loci for this disorder on chromosomes 3, 7, and 11, and specific mutated genes for long QT syndrome have been identified on two of these chromosomes. We investigated ECG T-wave patterns (phenotypes) in members of families linked to three genetically distinct forms of the long QT syndrome.

METHODS AND RESULTS

Five quantitative ECG repolarization parameters, ie, four Bazett-corrected time intervals (QTonset-c, QTpeak-c, QTc, and Tduration-c, in milliseconds) and the absolute height of the T wave (Tamplitude, in millivolts), were measured in 153 members of six families with long QT syndrome linked to markers on chromosomes 3 (n = 47), 7 (n = 30), and 11 (n = 76). Genotypic data were used to define each family member as being affected or unaffected with long QT syndrome. Affected members of all six families had longer QT intervals (QTonset-c, QTpeak-c, or QTc) than unaffected family members (P < .01). Each of the three long QT syndrome genotypes was associated with somewhat distinctive ECG repolarization features. Among affected individuals, the QTonset-c was unusually prolonged in those individuals with mutations involving the cardiac sodium channel gene SCN5A on chromosome 3 (lead II QTonset-c [mean +/- SD]: chromosome 3, 341 +/- 42 ms; chromosome 7, 290 +/- 56 ms; chromosome 11, 243 +/- 73 ms; P < .001); Tamplitude was generally quite small in the chromosome 7 genotype (lead II Tamplitude, mV: chromosome 3, 0.36 +/- 0.14; chromosome 7, 0.13 +/- 0.07; chromosome 11, 0.37 +/- 0.17; P < .001); and Tduration was particularly long in the chromosome 11 genotype (lead II Tduration-c: chromosome 3, 187 +/- 33 ms; chromosome 7, 191 +/- 51 ms; chromosome 11, 262 +/- 65 ms; P < .001). Similar ECG findings were observed in leads aVF and V5. A considerable variability exists in the quantitative repolarization parameters associated with each genotype, with overlap in the T-wave patterns among the three genotypes.

CONCLUSIONS

Three separate genetic loci for the long QT syndrome including mutations in two cardiac ionic channel genes were associated with different phenotypic T-wave patterns on the ECG. This study provides insight into the influence of genetic factors on ECG manifestations of ventricular repolarization.

Increased propensity of women to develop torsades de pointes during complete heart block

INTRODUCTION

To determine whether an increased female gender susceptibility to torsades de pointes (TdP) may exist in a clinical model of bradycardia-induced long QT syndrome, we investigated reported cases of TdP associated with acquired complete heart block.

METHODS AND RESULTS

Seventy-two cases reported in the medical literature dating from 1941 through 1993 were identified, all describing TdP or "transient ventricular tachycardia/fibrillation" (to include those cases reported prior to the use of TdP terminology) in the setting of acquired complete heart block unassociated with QT prolonging drugs. Expected female prevalence in complete heart block was estimated at 52%, based on projections derived from 206,016 hospital discharges in the National Inpatient Profile (Commission on Professional and Hospital Activities, Ann Arbor, MI), over the years 1985 through 1992. During complete heart block, mean heart rate was 37 beats/min in both sexes (combined n = 43), and absolute QT interval ranged from 0.52 to 0.88 seconds, with a mean of 0.68 seconds (n = 25). Female prevalence among patients with TdP during complete heart block was greater than expected: 72% for all studied cases (P < 0.001); 70% (P < 0.04) and 74% (P < 0.02) among those reported prior to (n = 35) and during or after (n = 37) 1980, respectively; 73% (P < 0.03) among those with documented normokalemia (n = 26); and 68% (P = 0.2) among those with a prolonged QT interval and known polymorphic VT (i.e., unequivocal TdP; n = 25).

CONCLUSION

Despite inherent limitations of this retrospective study, the data are consistent in suggesting a greater than expected female prevalence among patients with TdP related to complete heart block. This finding lends support to a broadening concept of increased susceptibility of women to the development of TdP in various settings of QT prolongation.

Evidence of genetic heterogeneity in Romano-Ward long QT syndrome. Analysis of 23 families

BACKGROUND

The Romano-Ward long-QT Syndrome (LQTS) is an autosomal dominant inherited trait characterized by prolonged QT interval on ECG, life-threatening arrhythmias, syncope, and sudden death in affected individuals. A gene responsible for this disorder has been shown to be linked to the Harvey ras-1 locus (H-ras-1) DNA marker on the short arm of chromosome 11 (11p) in 7 families. The purpose of this study was to determine, by analyzing 23 families with LQTS for linkage to chromosome 11p, whether evidence exists for more than one gene causing LQTS (ie, locus heterogeneity).

METHODS AND RESULTS

Twenty-three families (262 family members) were clinically evaluated using medical histories, ECGs, and Holter recordings. Each corrected QT interval (QTc) were determined using Bazett's formula. Blood for DNA extraction and cell line immortalization was obtained after informed consent. Southern blotting and polymerase chain reaction were performed, and linkage analysis carried out using the LINKAGE computer program (v 5.03). Genetic heterogeneity was determined using the HOMOG 2 (v 2.51) computer program. Twenty-three families were studied for evidence of linkage to chromosome 11p using the H-ras-1 locus probe pTBB-2 and multiple flanking markers, including tyrosine hydroxylase (TH). Two-point linkage analysis using pTBB-2 and TH markers was consistent with linkage in 15 of 23 families, with the maximum single-family LOD score of +3.038 occurring at theta = 0. However, 8 of 23 families had negative LOD scores, with the values in 4 families being less than -2 at theta = 0, consistent with exclusion of linkage. Analysis with the HOMOG program was consistent with genetic heterogeneity (P < .0001). Multipoint linkage data using pTBB-2 and TH were also examined for evidence of heterogeneity. HOMOG analysis of multipoint LOD scores from 100 cM surrounding the H-ras-1 locus also supported heterogeneity (P < .001).

CONCLUSIONS

In the 23 families with LQTS analyzed for linkage to the H-ras-1 locus on chromosome 11p15.5, 15 of 23 families had LOD scores consistent with linkage. The remaining 8 of 23 families had negative LOD scores, 4 of which were definitively excluded from linkage. Thus, genetic heterogeneity is definitively (P < .001) demonstrated for this disorder.

Differentiation of sinus tachycardia from ventricular tachycardia with 1:1 ventriculoatrial conduction in dual chamber implantable cardioverter defibrillators: feasibility of a criterion based on the atrioventricular interval

Tachycardia discrimination in future implantable cardioverter defibrillators (ICDs) is likely to be enhanced by the addition of an atrial sensing/pacing lead. However, differentiation of sinus tachycardia (ST) from ventricular tachycardia (VT) with 1:1 VA conduction will remain problematic. We assessed the use of the AV interval as a potential criterion for correctly differentiating ST from VT. Incremental V pacing at the right ventricular (RV) apex served as a "VT" model in each of 41 patients with 1:1 VA conduction to pacing cycle lengths < or = 450 msec. High right atrial and RV apical electrograms during normal sinus rhythm (NSR) and during incremental V pacing were digitized (simulating ICD sensing). From these signals, AV interval versus pacing cycle length plots were computer generated to identify crossover cycle lengths, each defined as the cycle length at which the AV interval during V pacing equals the AV interval during NSR. At cycle lengths longer than the crossover value, the AV interval during "VT" exceeds the AV interval during NSR. In contrast, the AV interval during ST is physiologically shorter than the AV interval during NSR. Thus, ST can be readily differentiated from "VT" over a range of cycle lengths greater than the crossover value. The overall mean calculated crossover cycle length was 371 +/- 52 msec. In 11 patients paced multiple times, each crossover cycle length was reproducible (mean coefficient of variation was 1.2% +/- 0.9% per patient). AV intervals measured at the RV apex were also analyzed with incremental V pacing during catecholamine stimulation (isoproterenol, n = 5) and during alternate site "VT" (RV outflow tract [n = 8] and left ventricle [n = 2]). In all these cases, the new "VT" plots of AV interval versus pacing cycle length coincided with or fell to the left of those obtained during control RV apical pacing and recording (i.e., these AV interval values crossed the NSR baseline at cycle lengths < or = the crossover cycle length). Thus, the cycle length range for recognizable differentiation of ST from "VT" remained valid. The data suggest that the described AV interval criterion relying on the crossover cycle length: (1) is a promising approach to improve differentiation of ST from relatively slow VTs with 1:1 VA conduction, and (2) can readily be automated in future dual chamber ICDs, given its computational simplicity.

Two long QT syndrome loci map to chromosomes 3 and 7 with evidence for further heterogeneity

Cardiac arrhythmias cause sudden death in 300,000 United States citizens every year. In this study, we describe two new loci for an inherited cardiac arrhythmia, long QT syndrome (LQT). In 1991 we reported linkage of LQT to chromosome 11p15.5. In this study we demonstrate further linkage to D7S483 in nine families with a combined lod score of 19.41 and to D3S1100 in three families with a combined score of 6.72. These findings localize major LQT genes to chromosomes 7q35-36 and 3p21-24, respectively. Linkage to any known locus was excluded in three families indicating that additional heterogeneity exists. Proteins encoded by different LQT genes may interact to modulate cardiac repolarization and arrhythmia risk.

Sudden death in recipients of first-generation implantable cardioverter defibrillators: analysis of terminal events. Participating investigators

Clinical factors and terminal events associated with sudden death in 51 patients were analyzed from among a multicenter experience of 864 recipients of first generation automatic implantable cardioverter defibrillator (AICD) devices (single zone, committed, monophasic pulse with > or = 1 epicardial patch electrode) during the period May 1982-February 1988. For these 51 patients, mean age was 58 years and atherosclerotic heart disease was present in 84%, with a history of ventricular fibrillation (VF) in 61%, and inducible sustained ventricular tachycardia (VT) in 84%; mean left ventricular ejection fraction was 0.26. Nearly 80% experienced one or more appropriate AICD shocks during the median 9 month (range 0-46 months) period prior to death. Of 30 monitored deaths, the first documented terminal rhythm was VF in 12 (40%), VT in 8 (27%), and asystole or electromechanical dissociation in the remaining 10 (33%). Shocks were documented during terminal events in 21 (66%) of 32 witnessed cases of sudden death with activated devices. The proportion of monitored or witnessed sudden deaths that were known or presumed to be tachyarrhythmic (based on terminal VT, VF, or shocks) ranged from 69% (11/16 cases with activated/nondepleted devices and a defibrillation threshold [DFT] < or = 20 J) to 81% (29/36 cases on intention-to-treat basis). Of 27 patients with known or presumed sudden tachyarrhythmic death, the AICD had been deactivated prior to death in 4 (15%); activated, but depleted in 4 (15%); activated/nondepleted, but with DFT of 25 J in 4 (15%); and activated/nondepleted, but without DFT testing in 4 (15%). The remaining 11 (41%) known or presumed sudden tachyarrhythmic deaths occurred in patients with activated/nondepleted devices and DFT < or = 20 J; however, definite or suspected contributory factors (e.g., hematoma under epicardial patch, generator component failure, or drug-induced DFT rise) could be identified in 6 (55%) of 11 cases. Thus, in this first-generation AICD experience: 1) most sudden deaths occurred on the basis of a known or presumed tachyarrhythmia; and 2) an understanding of apparent "failure" of ICD therapy could often be gained through an integrated analysis of associated clinical factors and management practices, as well as device "hardware" function. These observations are likely to remain relevant, even with respect to newer generation ICDs.

T wave "humps" as a potential electrocardiographic marker of the long QT syndrome

OBJECTIVES

This study attempted to determine the prevalence and electrocardiographic (ECG) lead distribution of T wave "humps" (T2, after an initial T wave peak, T1) among families with long QT syndrome and control subjects.

BACKGROUND

T wave abnormalities have been suggested as another facet of familial long QT syndrome, in addition to prolongation of the rate-corrected QT interval (QTc), that might aid in the diagnosis of affected subjects.

METHODS

The ECGs from 254 members of 13 families with long QT syndrome (each with two to four generations of affected members) and from 2,948 healthy control subjects (age > or = 16 years, QTc interval 0.39 to 0.46 s) were collected and analyzed. Tracings from families with long QT syndrome were read without knowledge of QTc interval or family member status (210 blood relatives and 44 spouses).

RESULTS

We found that T2 was present in 53%, 27% and 5% of blood relatives with a "prolonged" (> or = 0.47 s, "borderline" (0.42 to 0.46 s) and "normal" (< or = 0.41 s) QTc interval, respectively (p < 0.0001), but in only 5% and 0% of spouses with a borderline and normal QTc interval, respectively (p = 0.06 vs. blood relatives). Among blood relatives with T2, the mean [+/- SD] maximal T1T2 interval was 0.10 +/- 0.03 s and correlated with the QTc interval (p < 0.01); a completely distinct U wave was seen in 23%. T2 was confined to leads V2 and V3 in 10%, whereas V4, V5, V6 or a limb lead was involved in 90% of blood relatives with T2. Among blood relatives with a borderline QTc interval, 50% of those with versus 20% of those without major symptoms manifested T2 in at least one left precordial or limb lead (p = 0.05). A T2 amplitude > 1 mm (grade III) was observed, respectively, in 19%, 6% and 0% of blood relatives with a prolonged, borderline and normal QTc interval with T2 in at least one left precordial or limb lead. Among the 2,948 control subjects, 0.6% exhibited T2 confined to leads V2 and V3, and 0.9% had T2 involving one or more left precordial lead (but none of the limb leads). Among 37 asymptomatic adult blood relatives with QTc intervals 0.42 to 0.46 s, T2 was found in left precordial or limb leads in 9 (24%; 5 with limb lead involvement) versus only 1.9% of control subjects with a borderline QTc interval (p < 0.0001).

CONCLUSIONS

These findings are consistent with the hypothesis that in families with long QT syndrome, T wave humps involving left precordial or (especially) limb leads, even among asymptomatic blood relatives with a borderline QTc interval, suggest the presence of the long QT syndrome trait.

Implantable cardioverter-defibrillator therapy in 300 patients with coronary artery disease presenting exclusively with ventricular fibrillation

To determine outcomes of implantable cardioverter-defibrillator (ICD) therapy in a uniform population of survivors of sudden cardiac death, we used epicardial defibrillation lead systems to study 300 patients with coronary artery disease (CAD) presenting exclusively with ventricular fibrillation (VF) unassociated with acute myocardial infarction. Operative (30-day) mortality, 2.7% overall, was lower (0.6%) in patients with ejection fractions (EF) > or = 0.30. Over a median follow-up of 1.9 years, cumulative actuarial shock incidence was similar in patients who underwent concomitant coronary artery bypass graft (CABG) surgery (38%) and in those who did not. The 2-year cumulative actuarial incidences of any or appropriate shocks were 65% and 38%, respectively. Sudden death survival at 2 years was 92.5% and 99.3% for patients with EFs < or = 0.30 and > 0.30, respectively. The total mortality rate was similar in shocked and in unshocked patients. Multivariate analysis identified EF and female gender as significant predictors of any and appropriate shock occurrence (all p values < or = 0.05) and EF as a significant predictor of sudden, cardiac, and total mortality (all p values < 0.03). We conclude that in CAD patients presenting exclusively with VF unassociated with acute myocardial infarction and treated with thoracotomy-requiring ICD therapy: (1) operative (30-day) mortality is minimal for patients with an EF > or = 0.30; (2) device use is high and sudden death rates low regardless of concomitant CABG; (3) low EF is a significant predictor of cumulative shock occurrence and mortality (sudden, cardiac, and total); (4) female gender may be a predictor of shock occurrence; and (5) similar mortalities and low sudden-death rates in shocked and nonshocked ICD patients imply that ICD therapy improves survival in shocked patients to a level observed in comparable patients in whom ventricular tachyarrhythmia does not recur.

Female gender as a risk factor for torsades de pointes associated with cardiovascular drugs

OBJECTIVE

To test the hypothesis that female prevalence is greater than expected among reported cases of torsades de pointes associated with cardiovascular drugs that prolong cardiac repolarization.

DATA SOURCES

A MEDLINE search of the English-language literature for the period of 1980 through 1992, using the terms torsade de pointes, polymorphic ventricular tachycardia, atypical ventricular tachycardia, proarrhythmia, and drug-induced ventricular tachycardia, supplemented by pertinent references (dating back to 1964) from the reviewed articles and by personal communications with researchers involved in this field.

STUDY SELECTION

Ninety-three articles were identified describing at least one case of polymorphic ventricular tachycardia (with gender specified) associated with quinidine, procainamide hydrochloride, disopyramide, amiodarone, sotalol hydrochloride, bepridil hydrochloride, or prenylamine. A total of 332 patients were included in the analysis following application of prospectively defined criteria (eg, corrected QT [QTc] interval of 0.45 second or greater while receiving drug).

DATA EXTRACTION

Clinical and electrocardiographic descriptors were extracted for analysis. Expected female prevalence for torsades de pointes associated with quinidine, procainamide, disopyramide, and aminodarone was conservatively estimated from gender-specific data reported for antiarrhythmic drug prescriptions in 1986, as derived from the National Disease and Therapeutic Index, a large pharmaceutical database; expected female prevalence for torsades de pointes associated with sotalol, bepridil, and prenylamine was assumed to be 50% or less since these agents are prescribed for male-predominant cardiovascular conditions.

RESULTS

Women made up 70% (95% confidence interval, 64% to 75%) of the 332 reported cases of cardiovascular-drug-related torsades de pointes, and a female prevalence exceeding 50% was observed in 20 (83%) of 24 studies having at least four included cases. When analyzed according to various descriptors, women still constituted the majority (range, 51% to 94% of torsades de pointes cases), irrespective of the presence or absence of underlying coronary artery or rheumatic heart disease, left ventricular dysfunction, type of underlying arrhythmia, hypokalemia, hypomagnesemia, bradycardia, concomitant digoxin treatment, or level of QTc at baseline or while receiving drug. When cases of torsades de pointes were analyzed by individual drug, observed female prevalence was always greater than expected, representing a statistically significant difference (P < .05) for all agents except procainamide.

CONCLUSIONS

These findings strongly suggest that women are more prone than men to develop torsades de pointes during administration of cardiovascular drugs that prolong cardiac repolarization. The pathophysiological basis for, and therapeutic implications of, this gender disparity should be further investigated.