Atrioventricular block-induced Torsades de Pointes with clinical and molecular backgrounds similar to congenital long QT syndrome.

BACKGROUND: Atrioventricular block (AVB) sometimes complicates QT prolongation and torsades de pointes (TdP). METHODS AND RESULTS: The clinical and genetic background of 14 AVB patients (57±21 years, 13 females) who developed QT prolongation and TdP was analyzed. Electrophysiological characteristics of mutations were analyzed using heterologous expression in Chinese hamster ovary cells, together with computer simulation models. Every patient received a pacemaker or implantable cardioverter defibrillator; 3 patients had recurrence of TdP during follow-up because of pacing failure. Among the ECG parameters, QTc interval was prolonged to 561±76ms in the presence of AVB, but shortened to 495±42ms in the absence of AVB. Genetic screening for KCNQ1, KCNH2, SCN5A, KCNE1, and KCNE2 revealed four heterozygous missense mutations of KCNQ1 or KCNH2 in 4 patients (28.6%). Functional analyses showed that all mutations had loss of functions and various gating dysfunctions of I(Ks) or I(Kr). Finally, action potential simulation based on the Luo-Rudy model demonstrated that most mutant channels induced bradycardia-related early afterdepolarizations. CONCLUSIONS: Incidental AVB, as a trigger of TdP, can manifest as clinical phenotypes of long QT syndrome (LQTS), and that some patients with AVB-induced TdP share a genetic background with those with congenital LQTS.

Genotype-phenotype correlations of KCNJ2 mutations in Japanese patients with Andersen-Tawil syndrome.

Andersen-Tawil syndrome (ATS) is a rare inherited disorder characterized by periodic paralysis, mild dysmorphic features, and QT or QU prolongation with ventricular arrhythmias in electrocardiograms (ECGs). Mutations of KCNJ2, encoding the human inward rectifying potassium channel Kir 2.1, have been identified in patients with ATS. We aimed to clarify the genotype-phenotype correlations in ATS patients. We screened 23 clinically diagnosed ATS patients from 13 unrelated Japanese families. Ten different forms of KCNJ2 mutations were identified in the 23 ATS patients included in this study. Their ECGs showed normal QTc intervals and abnormal U waves with QUc prolongation and a variety of ventricular arrhythmias. Especially, bidirectional ventricular tachycardia (VT) was observed in 13 of 23 patients (57%). Periodic paralysis was seen in 13 of 23 carriers (57%), dysmorphic features in 17 (74%), and seizures during infancy in 4 (17%). Functional assays for the two novel KCNJ2 mutations (c. 200G>A (p. R67Q) and c. 436G>A (p. G146S)) displayed no functional inward rectifying currents in a heterologous expression system and showed strong dominant negative effects when co-expressed with wild-type KCNJ2 channels (91% and 84% reduction at -50 mV respectively compared to wild-type alone). Immunocytochemistry and confocal imaging revealed normal trafficking for mutant channels. In our study, all of the clinically diagnosed ATS patients had KCNJ2 mutations and showed a high penetrance with regard to the typical cardiac phenotypes: predominant U wave and ventricular arrhythmias, typically bidirectional VT.

Autotaxin, Pruritus and Primary Biliary Cholangitis (PBC).

Autotaxin (ATX) is a 125-kD type II ectonucleotide pyrophosphatase/phosphodiesterase (ENPP2 or NPP2) originally discovered as an unknown "autocrine motility factor" in human melanoma cells. In addition to its pyrophosphatase/phosphodiesterase activities ATX has lysophospholipase D (lysoPLD) activity, catalyzing the conversion of lysophosphatidylcholine (LPC) into lysophosphatidic acid (LPA). ATX is the only ENPP family member with lysoPLD activity and it produces most of the LPA in circulation. In support of this, ATX heterozygous mice have 50% of normal LPA plasma levels. The ATX-LPA signaling axis plays an important role in both normal physiology and disease pathogenesis and recently has been linked to pruritus in chronic cholestatic liver diseases, including primary biliary cholangitis (PBC). Several lines of evidence have suggested that a circulating puritogen is responsible, but the identification of the molecule has yet to be definitively identified. In contrast, plasma ATX activity is strongly associated with pruritus in PBC, suggesting a targetable molecule for treatment. We review herein the biochemistry of ATX and the rationale for its role in pruritus.

Diagnosis of B-cell lymphoma. Utility of the polymerase chain reaction for detecting clonality from archival cytologic smears.

OBJECTIVE: To apply the polymerase chain reaction (PCR) to detect clonality for potentially helping to establish a definitive diagnosis of lymphoma in cytologic material. STUDY DESIGN: In this retrospective study, Papanicolaou-stained cytologic smears and formalin-fixed, paraffin-embedded tissues from 17 cases of B-cell lymphoma were examined to investigate their clonality by a PCR technique using three different approaches (FR3, FR3A and FR2) for amplification of immunoglobulin heavy chain genes. Cytologic smears from 10 cases of nonneoplastic lymphoid tissues and T-cell lymphomas served as negative controls. RESULTS: Monoclonality was detected in 9 of 17 cases (53%) of B-cell lymphoma in cytologic smears as compared with 8 of 16 cases (50%) in tissue sections. Semi-nested PCRs (FR3A/FR2) were superior to the single PCR (FR3) in the detection rate (41% vs. 18%). Five of seven cases (71%) of marginal zone B-cell lymphomas showed monoclonality, whereas only 4 of 10 cases (40%) of diffuse large B-cell lymphomas did so. Monoclonality was demonstrated in none of the negative controls. CONCLUSIONS: Clonality detection in B-cell lymphomas by PCR using cytologic smears is specific and equal in sensitivity to that using formalin-fixed, paraffin-embedded tissues. The detection rate is especially excellent in marginal zone B-cell lymphoma, in which the cytologic diagnosis is particularly challenging. Combined seminested PCRs for FR3A and FR2 are advocated for a reliable assessment of clonality.

A novel gain-of-function KCNJ2 mutation associated with short-QT syndrome impairs inward rectification of Kir2.1 currents.

AIMS: Short-QT syndrome (SQTS) is a recently recognized disorder associated with atrial fibrillation (AF) and sudden death due to ventricular arrhythmias. Mutations in several ion channel genes have been linked to SQTS; however, the mechanism remains unclear. This study describes a novel heterozygous gain-of-function mutation in the inward rectifier potassium channel gene, KCNJ2, identified in SQTS. METHODS AND RESULTS: We studied an 8-year-old girl with a markedly short-QT interval (QT = 172 ms, QTc = 194 ms) who suffered from paroxysmal AF. Mutational analysis identified a novel heterozygous KCNJ2 mutation, M301K. Functional assays displayed no Kir2.1 currents when M301K channels were expressed alone. However, co-expression of wild-type (WT) with M301K resulted in larger outward currents than the WT at more than -30 mV. These results suggest a gain-of-function type modulation due to decreased inward rectification. Furthermore, we analysed the functional significance of the amino acid charge at M301 (neutral) by changing the residue. As with M301K, in M301R (positive), the homozygous channels were non-functional, whereas the heterozygous channels demonstrated decreased inward rectification. Meanwhile, the currents recorded in M301A (neutral) showed normal inward rectification under both homo- and heterozygous conditions. Heterozygous overexpression of WT and M301K in neonatal rat ventricular myocytes exhibited markedly shorter action potential durations than the WT alone. CONCLUSION: In this study, we identified a novel KCNJ2 gain-of-function mutation, M301K, associated with SQTS. Functional assays revealed no functional currents in the homozygous channels, whereas impaired inward rectification demonstrated under the heterozygous condition resulted in larger outward currents, which is a novel mechanism predisposing SQTS.

Prognostic utility of T-wave alternans in a real-world population of patients with left ventricular dysfunction: the PREVENT-SCD study.

BACKGROUND: The predictive value of T-wave alternans (TWA) for lethal ventricular tachyarrhythmia in patients with left ventricular (LV) dysfunction is controversial. Also, long-term arrhythmia risk of patients ineligible for the TWA test is unknown. METHODS: This was a multicenter, prospective observational study of patients with LV ejection fraction ≤40% due to ischemic or non-ischemic cardiomyopathies, designed to evaluate the prognostic value of TWA for lethal ventricular tachyarrhythmia. The primary end point was a composite of sudden cardiac death, sustained rapid ventricular tachycardia (VT) or ventricular fibrillation (VF), and appropriate defibrillator therapy for rapid VT or VF. RESULTS: Among 453 patients enrolled in the study, 280 (62%) were eligible for the TWA test. TWA was negative in 82 patients (29%), who accounted for 18% of the total population. The median of follow-up was 36 months. The 3-year event-free rate for the primary end point was significantly higher in TWA-negative patients (97.0%) than in TWA non-negative patients (89.5%, P = 0.037) and those ineligible for the TWA test (84.4%, P = 0.003). Multivariable analysis identified both non-negative TWA [hazard ratio (HR) 4.43; 95% confidence interval (CI) 1.02-19.2; P = 0.047) and ineligibility for the TWA test (HR 6.89; 95% CI 1.59-29.9; P = 0.010) to be independent predictors of the primary end point. CONCLUSIONS: TWA showed high negative predictive ability for lethal ventricular tachyarrhythmia in patients with LV dysfunction, although the TWA-negative patients accounted for only 18% of the entire population. Those ineligible for the TWA test had the highest risk for lethal ventricular tachyarrhythmia.

D85N, a KCNE1 polymorphism, is a disease-causing gene variant in long QT syndrome.

OBJECTIVES: This study aims to address whether D85N, a KCNE1 polymorphism, is a gene variant that causes long QT syndrome (LQTS) phenotype. BACKGROUND: KCNE1 encodes the beta-subunit of cardiac voltage-gated K(+) channels and causes LQTS, which is characterized by the prolongation of the QT interval and torsades de pointes, a lethal arrhythmia. D85N, a KCNE1 polymorphism, is known to be a functional variant associated with drug-induced LQTS. METHODS: In order to elucidate the prevalence and clinical significance of this polymorphism, we performed genetic screening in 317 LQTS probands. For comparison, we examined its presence in 496 healthy control subjects. We also conducted biophysical assays for the D85N variant in mammalian cells. RESULTS: The allele frequency for D85N carriers was 0.81% in healthy people. In contrast, among LQTS probands, there were 1 homozygous and 23 heterozygous carriers (allele frequency 3.9%). Seven of 23 heterozygous carriers had additional mutations in LQTS-related genes, and 3 female subjects had documented factors predisposing to the symptom. After excluding these probands, the D85N prevalence was significantly higher compared with control subjects (allele frequency 2.1%, p < 0.05). In a heterologous expression study with Chinese hamster ovarian cells, KCNE1-D85N was found to exert significant loss-of-function effects on both KCNQ1- and KCNH2-encoded channel currents. CONCLUSIONS: The KCNE1-D85N polymorphism was significantly more frequent in our LQTS probands. The functional variant is a disease-causing gene variant of LQTS phenotype that functions by interacting with KCNH2 and KCNQ1. Since its allele frequency was approximately 1% among control individuals, KCNE1-D85N may be a clinically important genetic variant.

Latent genetic backgrounds and molecular pathogenesis in drug-induced long-QT syndrome.

BACKGROUND: Drugs with I(Kr)-blocking action cause secondary long-QT syndrome. Several cases have been associated with mutations of genes coding cardiac ion channels, but their frequency among patients affected by drug-induced long-QT syndrome (dLQTS) and the resultant molecular effects remain unknown. METHODS AND RESULTS: Genetic testing was carried out for long-QT syndrome-related genes in 20 subjects with dLQTS and 176 subjects with congenital long-QT syndrome (cLQTS); electrophysiological characteristics of dLQTS-associated mutations were analyzed using a heterologous expression system with Chinese hamster ovary cells together with a computer simulation model. The positive mutation rate in dLQTS was similar to cLQTS (dLQTS versus cLQTS, 8 of 20 [40%] versus 91 of 176 [52%] subjects, P=0.32). The incidence of mutations was higher in patients with torsades de pointes induced by nonantiarrhythmic drugs than by antiarrhythmic drugs (antiarrhythmic versus others, 3 of 14 [21%] versus 5 of 6 [83%] subjects, P<0.05). When reconstituted in Chinese hamster ovary cells, KCNQ1 and KCNH2 mutant channels showed complex gating defects without dominant negative effects or a relatively mild decreased current density. Drug sensitivity for mutant channels was similar to that of the wild-type channel. With the Luo-Rudy simulation model of action potentials, action potential durations of most mutant channels were between those of wild-type and cLQTS. CONCLUSIONS: dLQTS had a similar positive mutation rate compared with cLQTS, whereas the functional changes of these mutations identified in dLQTS were mild. When I(Kr)-blocking agents produce excessive QT prolongation (dLQTS), the underlying genetic background of the dLQTS subject should also be taken into consideration, as would be the case with cLQTS; dLQTS can be regarded as a latent form of long-QT syndrome.

Mutation analysis of the glycerol-3 phosphate dehydrogenase-1 like (GPD1L) gene in Japanese patients with Brugada syndrome.

Brugada syndrome is an inherited arrhythmic disorder, and mutations in the SCN5A gene, encoding cardiac sodium channels, are identified in approximately 15% of cases. A novel causative gene (glycerol-3 phosphate dehydrogenase-1 like; GPD1L) has been reported, and in the present study, 80 unrelated Japanese patients were screened for GPD1L mutations: 1 synonymous mutation was identified, as well as 1 intronic variant, both of which were absent in 220 control alleles. Additionally, a single-nucleotide polymorphism was detected in 4 patients. No non-synonymous mutations were found. GPD1L does not appear to be a major cause of Brugada syndrome in the Japanese population.

Malignant link between chronic heart failure and acute cardiac decompensation in patients with persistently increased serum concentrations of cardiac troponin.

During the progression of heart failure (HF), phases of chronic compensation and acute decompensation alternate and the clinical status worsens during the acute phase. At the present time, few studies have focused their attention on the cycles of compensated and decompensated phases from the perspective of myocyte injury. We hypothesize that persistently increased serum cTn concentrations during chronic compensated HF identify patients likely to need multiple admissions to the hospital for management of acute cardiac decompensation, worsening their long-term prognosis by causing further myocyte injury during the acute phase. In patients with acute cardiac decompensation, myocyte injury observed within hours or days has a long-term predictive value, and the acute surge of myocyte injury occurring in the acutely decompensated phase might be an important therapeutic target from the perspective of myocyte preservation. Clinical trials that limit myocyte injury during acutely decompensated as well as during chronic compensated HF are warranted.

A novel SCN5A gain-of-function mutation M1875T associated with familial atrial fibrillation.

OBJECTIVES: This study describes a novel heterozygous gain-of-function mutation in the cardiac sodium (Na+) channel gene, SCN5A, identified in a Japanese family with lone atrial fibrillation (AF). BACKGROUND: SCN5A mutations have been associated with a variety of inherited arrhythmias, but the gain-of-function type modulation in SCN5A is associated with only 1 phenotype, long-QT syndrome type 3 (LQTS3). METHODS: We studied a Japanese family with autosomal dominant hereditary AF, multiple members of which showed an onset of AF or frequent premature atrial contractions at a young age. RESULTS: The 31-year-old proband received radiofrequency catheter ablation, during which time numerous ectopic firings and increased excitability throughout the right atrium were documented. Mutational analysis identified a novel missense mutation, M1875T, in SCN5A. Further investigations revealed the familial aggregation of this mutation in all of the affected individuals. Functional assays of the M1875T Na(+) channels using a whole-cell patch-clamp demonstrated a distinct gain-of-function type modulation; a pronounced depolarized shift (+16.4 mV) in V(1/2) of the voltage dependence of steady-state inactivation; and no persistent Na+ current, which is a defining mechanism of LQTS3. These biophysical features of the mutant channels are potentially associated with increased atrial excitability and normal QT interval in all of the affected individuals. CONCLUSIONS: We identified a novel SCN5A mutation associated with familial AF. The mutant channels displayed a gain-of-function type modulation of cardiac Na+ channels, which is a novel mechanism predisposing to increased atrial excitability and familial AF. This is a new phenotype resulting from the SCN5A gain-of-function mutations and is distinct from LQTS3.

Cardiac troponin T vs other biochemical markers in patients with congestive heart failure.

BACKGROUND: Several pathologic processes can cause myocardial injury, which is followed by cardiac remodeling and congestive heart failure (CHF). Cardiac troponin T (cTnT), a specific and sensitive marker of myocardial injury, has been related to long-term outcome in patients with CHF, so the relationship between cTnT and other biochemical markers associated with the pathophysiology of CHF was investigated in the present study. METHODS AND RESULTS: Between February 2004 and December 2005, 145 consecutive hospitalized patients (mean left ventricular ejection fraction (LVEF) 31.6+/-0.9%) with CHF were divided into low (<0.01 ng/ml) and high (> or =0.01 ng/ml) serum cTnT groups. Correlations with other prognostic biochemical markers, including brain natriuretic peptide (BNP), type I collagen C-terminal telopeptide (ICTP), procollagen type III peptide (PIIIP), renin, norepinephrine (NOREPI), C-reactive protein (CRP), cholesterol, hemoglobin (Hb), uric acid and HbA1c were examined. cTnT was high in 46 (32%) and low in 99 (68%) patients at baseline. Patients with high cTnT had abnormally high blood concentrations of BNP (p<0.0001), ICTP (p<0.0001), PIIIP (p=0.0006), NOREPI (p=0.0119), CRP (p=0.0003), uric acid (p=0.0026) and HbA1c (p=0.0361). In contrast, concentrations of cholesterol and Hb were significantly lower in patients with high cTnT (p=0.0319 and 0.0005, respectively). Death from or rehospitalization for CHF occurred in 41% in the high vs 9% in the low cTnT group (p=0.0002). Univariate analysis showed that high cTnT (p=0.0005), BNP (p=0.0001), renin (p=0.0158), NOREPI (p=0.0094), old age (p=0.0390), low LVEF (p=0.0231) and high New York Heart Association (NYHA) class (p=0.0006) were predictors of death from or rehospitalization for CHF. By multivariate analysis including BNP, NOREPI, age, LVEF and NYHA class, high cTnT and renin remained as significant predictors. CONCLUSIONS: Patients with ongoing myocardial injury and high cTnT had associated findings consistent with activation of the sympathetic system, synthesis of cardiac fibrosis, inflammation and metabolic abnormalities. By multivariate analysis, high cTnT and renin remained significant predictors of death or rehospitalization.

Measurements of baseline and follow-up concentrations of cardiac troponin-T and brain natriuretic peptide in patients with heart failure from various etiologies.

Since chronic heart failure (CHF) is a complex clinical syndrome, a single biomarker may not reflect all of its characteristics. In this study, the clinical significance of combination and serial measurement of biochemical markers of myocyte injury and myocardial load in patients with CHF from various etiologies was examined. Serum concentrations of cardiac troponin-T (cTnT) and plasma concentrations of brain natriuretic peptide (BNP) were measured simultaneously in 190 patients with CHF, including dilated cardiomyopathy (DCM) (n = 41), ischemic heart disease (n = 40), valvular or congenital disease (n = 53), hypertensive heart disease (n = 16), and hypertrophic cardiomyopathy (HCM) (n = 22). Serum cTnT concentrations >or=0.01 ng/ml were found in 46/190 patients (24%) at baseline (20% in DCM, 42% in ischemic heart disease, 21% in valvular or congenital disease, 43% in hypertensive heart disease, and 9% in HCM). Follow-up samples were obtained in 137 patients after a mean treatment period of 31.8 days. Although BNP decreased significantly in each disease category (P < 0.0001: DCM; P < 0.005: ischemic heart disease; P < 0.05: valvular or congenital disease; P < 0.005: hypertensive heart disease; P < 0.05: HCM), cTnT remained high in 36/137 patients (26%) (19% in DCM, 39% in ischemic heart disease, 25% in valvular or congenital disease, 38% in hypertensive heart disease, and 19% in HCM). The rate of adverse cardiac events was significantly higher in patients with high cTnT than in patients with low cTnT concentrations (P < 0.0001) (P < 0.05: DCM; P < 0.05: ischemic heart disease; P < 0.01: valvular or congenital disease). Multivariate analysis showed that both cTnT and BNP are independent prognostic factors, and patients with elevations of both cTnT and BNP had the poorest prognosis (P < 0.0001). In patients with CHF, the evolution and prognostic value of cTnT and BNP are different. The combined measurements of these markers should refine our understanding of the state and evolution of CHF.

Current understanding of biochemical markers in heart failure.

Chronic heart failure (CHF) is a major cause of morbidity and mortality in industrialized countries. As societies are aging, efforts are directed toward early interventions to preserve quality of life as well as lower mortality. However, because of the paucity of specific symptoms, an early diagnosis and management of CHF might be challenging. In contrast, biochemical markers, which can be measured easily and without inter-observer variability, are now being carefully examined. Since CHF is a complex syndrome, a single biochemical marker cannot reflect its multiple manifestations. An ideal biochemical marker should 1) be a prognostic indicator, 2) reflect the therapeutic response, 3) be heart specific 4) be independent from other markers 5) reflect the pathophysiology of CHF, 6) assist in the early diagnosis of CHF, and 7) be reliable throughout the various phases of the syndrome, from before the onset of its clinical manifestations through its end-stage. This review summarizes our current understanding of biochemical markers of CHF based on its pathophysiology.

Silent pulmonary artery dissection in a patient with Eisenmenger syndrome due to ventricular septal defect: a case report.

A 62-year-old woman was admitted to our hospital because of fever in August 2002. She had been treated under a diagnosis of Eisenmenger syndrome with ventricular septal defect since 1988. On admission, echocardiography and color Doppler echocardiography revealed a markedly enlarged pulmonary artery with a mobile flap, and dissection of the pulmonary artery. The origin of the fever could not be identified, and the fever subsided spontaneously without specific treatment. She had no chest pain, but fever might have been a sign of dissection in this patient. Longstanding pulmonary hypertension may cause dissection, which may lead to sudden death or pulmonary hemorrhage often seen in patients with Eisenmenger syndrome. Our patient was a rare survivor without serious bleeding complication.

[Complex myxoma detected by syncope: a case report].

A 23-year-old man was admitted to our hospital for evaluation of syncope and intracardiac masses. Echocardiography revealed three masses in the right ventricle and one in the left ventricle. The largest mass, 4 by 5 cm, occupied the right ventricular outflow tract and prolapsed through the pulmonary valve orifice. Right ventricular systolic pressure was 65 mmHg. A soft mass, 4 by 5 cm, was found on the left subcostal abdominal wall and multiple pigmented spots on the face and trunk. Histological examination of the resected tumors, including the abdominal soft mass, were consistent with myxoma. The combination of multiple cardiac and abdominal wall myxomas and pigmented skin lesions in this young patient is considered to be a diagnostic feature of Carney complex.