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Interval Duration (interval + duration)

Distribution by Scientific Domains
Medical Sciences87%

Kinds of Interval Duration

  • qt interval duration
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    Selected Abstracts

    Suboptimal Glycemic Control, Independently of QT Interval Duration, Is Associated with Increased Risk of Ventricular Arrhythmias in a High-Risk Population

    PACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 1 2006
    CAROL CHEN-SCARABELLI
    Background: Although cardiovascular disease is the leading cause of mortality in diabetic patients, little is known about the impact of glycemic control on ventricular tachycardia (VT). Objective: To investigate whether hemoglobin A1c (HbA1c) is associated with increased incidence of VT. Methods: A retrospective study of 336 implantable cardioverter-defibrillator patients (both diabetes mellitus (DM) and non-DM) was conducted. Results: HbA1c levels between 8% and 10% had a significant association with spontaneous VT, but not with QT/QTc. Conclusions: Glycemic index is a significant predictor of spontaneous VT, independently of QT interval. Optimal glycemic control may help reduce occurrence of VT and sudden cardiac death in high-risk DM patients. [source]

    Relationship between Genetic Variants in Myocardial Sodium and Potassium Channel Genes and QT Interval Duration in Diabetics: The Diabetes Heart Study

    ANNALS OF NONINVASIVE ELECTROCARDIOLOGY, Issue 1 2009
    Allison B. Lehtinen Ph.D.
    Background: Genetic variants in myocardial sodium and potassium channel genes are associated with prolonged QT interval and increased risk of sudden death. It is unclear whether these genetic variants remain relevant in subjects with underlying conditions such as diabetes that are associated with prolonged QT interval. Methods: We tested single nucleotide polymorphisms (SNPs) in five candidate genes for association with QT interval in a family-based study of subjects with type 2 diabetes mellitus (T2DM). Thirty-six previously reported SNPs were genotyped in KCNQ1, HERG, SCN5A, KCNE1, and KCNE2 in 901 European Americans from 366 families. The heart rate-corrected (QTc) durations were determined using the Marquette 12SL program. Associations between the QTc interval and the genotypes were evaluated using SOLAR adjusting for age, gender, T2DM status, and body mass index. Results: Within KCNQ1 there was weak evidence for association between the minor allele of IVS12 +14T>C and increased QTc (P = 0.02). The minor allele of rs2236609 in KCNE1 trended toward significance with longer QTc (P = 0.06), while the minor allele of rs1805123 in HERG trended toward significance with shorter QTc (P = 0.07). However, no statistically significant associations were observed between the remaining SNPs and QTc variation. Conclusions: We found weak evidence of association between three previously reported SNPs and QTc interval duration. While it appears as though genetic variants in previously identified candidate genes may be associated with QT duration in subjects with diabetes, the clinical implications of these associations in diabetic subjects at high risk for sudden death remain to be determined. [source]

    Maternal memory in adult, nulliparous rats: Effects of testing interval on the retention of maternal behavior

    DEVELOPMENTAL PSYCHOBIOLOGY, Issue 1 2005
    Robert S. Bridges
    Abstract The retention of maternal behavior (i.e., maternal memory) was measured in adult, nulliparous rats induced to respond maternally by continuous exposure to foster pups. Specifically, the effects of the interval duration between the initial induction and the reinduction of maternal behavior were determined. Intact virgin rats were first exposed to foster young to induce maternal behavior. During the initial induction phase, females were required to be fully maternal on 2 consecutive test days. Animals were then assigned to one of three interval groups (10, 20, or 40 days). After being isolated from rat pups for these designated periods, females in each group were tested again for their latencies to induce maternal behavior. Whereas the initial median latencies to display full maternal behavior ranged from 4.5 to 5 days for each group, upon retesting, median latencies for each group declined to 1 to 4 days. The greatest reduction in latency was present in the 10-day group (80%), and the smallest reduction was detected in the 40-day group (20%). A significant negative linear correlation was found between test interval and percentage reduction in behavioral latency. Based upon this relationship and under these test conditions, "maternal memory" in the adult, nulliparous rat would be expected to be nondetectable after about an interval of 50 days between tests. The pattern of maternal memory acquisition and loss appears similar to that reported in parous animals. The present study highlights similarities and possible differences underlying the establishment of the retention of maternal behavior (i.e., maternal memory). © 2004 Wiley Periodicals, Inc. Dev Psychobiol 46: 13,18, 2005. [source]

    Hyperglycaemia induced QT interval duration: a key to the increased risk of sudden death in diabetic patients?

    DIABETIC MEDICINE, Issue 8 2008
    G. Andrássy
    No abstract is available for this article. [source]

    Vocal Discrimination in Mate Guarding Male Australian Sea Lions: Familiarity Breeds Contempt

    ETHOLOGY, Issue 8 2010
    Marie R. G. Attard
    The vocal characteristics of a species can be immensely diverse, and can significantly impact animal social interactions. The social structure of a species may vary with geographical variation in call characteristics. The ability of pinnipeds (true seals, fur seals, sea lions and walrus) to distinguish between conspecifics may assist male reproductive strategies, particularly mate acquisition. We assessed the ability of mate guarding Australian sea lion (Neophoca cinerea) males to discriminate local from foreign males' barks recorded from a geographically distant breeding colony. Bark characteristics were significantly different between colonies, with barks produced by males from the Lewis Island breeding colony higher pitched and longer in both duration and interval duration than barks produced by males on Kangaroo Island. Mate guarding males displayed inter-colony discrimination of barks, with a significantly stronger response to barks from local males than to those of males from a colony approx. 180 km away. Local males' barks were apparently considered a greater threat than barks from unfamiliar males. We propose that discrimination of acoustic characteristics may facilitate reproductive isolation in this species that may lead to an ethological,acoustic barrier between breeding colonies, and subsequent genetic isolation. [source]

    Malignant Ventricular Arrhythmia in a Case of Adult Onset of Spinal Muscular Atrophy (Kugelberg,Welander Disease)

    JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 3 2009
    MARKUS ROOS M.D.
    We present a case of a 43-year-old male patient with adult onset of spinal muscular atrophy (SMA). The patient first came to our attention with atrioventricular (AV) block. A dual-chamber pacemaker (DDD-PM) was implanted. Four years later, the PM data log showed occurrence of frequent episodes of nonsustained ventricular tachycardia (NSVT). The episodes progressed in duration and frequency. An electrophysiological study revealed prolonged His-ventricular (HV) interval duration and induction of sustained ventricular tachycardia. The patient was successfully upgraded to a prophylactic dual-chamber cardioverter defibrillator. Our case is the first description of a patient with adult-onset SMA (Kugelberg,Welander disease [KWD]) and malignant ventricular arrhythmias. [source]

    QT Interval Dispersion and Cardiac Sympathovagal Balance Shift in Rats With Acute Ethanol Withdrawal

    ALCOHOLISM, Issue 2 2010
    Seiko Shirafuji
    Background:, Dysregulation of autonomic nervous system function and impaired homogeneity of myocardial repolarization are 2 important mechanisms for the genesis of ventricular arrhythmias in nonalcoholic subjects. Our previous study suggested that acute ethanol withdrawal promoted the shift of cardiac sympathovagal balance toward sympathetic predominance and reduced the vagal tone, which were related to a higher incidence of ventricular arrhythmia and related death. However, the homogeneity of myocardial repolarization and its relation with the cardiac sympathovagal balance are unknown, especially in alcoholic subjects. The aim of the present study was to clarify these points. Methods:, Male Wistar rats were treated with a continuous ethanol liquid diet for 49 days, and then subjected to 1-day withdrawal and 1-day withdrawal with 7-day carvedilol (can block the sympathetic nervous system completely via ,1, ,2, and , adrenergic receptors) pretreatment. The cardiac sympathovagal balance and homogeneity of myocardial repolarization were evaluated based on the heart rate variability (HRV) and QT interval dispersion (QTd: dynamic changes in QT interval duration). Results:, The increase in QTd was observed only in rats at 1-day withdrawal, but not in nonalcoholic, continuous ethanol intake, and 1-day withdrawal with 7-day carvedilol pretreatment rats. At 1-day withdrawal, the low-frequency power/high-frequency power (LF/HF) ratio in HRV was elevated and correlated with the QTd. The increased QTd and elevated LF/HF ratio were normalized by the 7-day carvedilol pretreatment in rats at 1-day ethanol withdrawal. Conclusions:, In rats with an abrupt termination of the chronic continuous ethanol intake, the homogeneity of myocardial repolarization impaired and correlated with the cardiac sympathovagal balance. Carvedilol pretreatment is associated with a reduction in both the QTd and LF/HF ratio, raising the possibility that the cardiac sympathovagal balance shift may be responsible for the impaired homogeneity of myocardial repolarization, and that ,-blocker pretreatment may decrease the mortality risk during alcoholic withdrawal. [source]

    Genome-wide association studies of cardiovascular risk factors: design, conduct and interpretation

    JOURNAL OF THROMBOSIS AND HAEMOSTASIS, Issue 2009
    J. C. BIS
    Summary., Relying on known biology, candidate-gene studies have been only modestly successful in identifying genetic variants associated with cardiovascular risk factors. Genome-wide association (GWA) studies, in contrast, allow broad scans across millions of loci in search of unsuspected genetic associations with phenotypes. The large numbers of statistical tests in GWA studies and the large sample sizes required to detect modest-sized associations have served as a powerful incentive for the development of large collaborative efforts such as the Cohorts for Heart and Aging Research in Genomic Epidemiology (CHARGE) Consortium [1]. This article uses published data on three phenotypes, fibrinogen, uric acid, and electrocardiographic QT interval duration, from the CHARGE Consortium to describe several methodologic issues in the design, conduct, and interpretation of GWA studies, including the use of imputation and the need for additional genotyping. Even with large studies, novel genetic loci explain only a small proportion of the variance of cardiovascular phenotypes. [source]

    QT Interval Variability and Adaptation to Heart Rate Changes in Patients with Long QT Syndrome

    PACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 1 2009
    JAN N, MEC M.D.
    Background: Increased QT variability (QTV) has been reported in conditions associated with ventricular arrhythmias. Data on QTV in patients with congenital long QT syndrome (LQTS) are limited. Methods: Ambulatory electrocardiogram recordings were analyzed in 23 genotyped LQTS patients and in 16 healthy subjects (C). Short-term QTV was compared between C and LQTS. The dependence of QT duration on heart rate was evaluated with three different linear models, based either on the RR interval preceding the QT interval (RR0), the RR interval preceding RR0 (RR -1), or the average RR interval in the 60-second period before QT interval (mRR). Results: Short-term QTV was significantly higher in LQTS than in C subjects (14.94 ± 9.33 vs 7.31 ± 1.29 ms; P < 0.001). It was also higher in the non-LQT1 than in LQT1 patients (23.00 ± 9.05 vs 8.74 ± 1.56 ms; P < 0.001) and correlated positively with QTc in LQTS (r = 0.623, P < 0.002). In the C subjects, the linear model based on mRR predicted QT duration significantly better than models based on RR0 and RR -1. It also provided better fit than any nonlinear model based on RR0. This was also true for LQT1 patients. For non-LQT1 patients, all models provided poor prediction of QT interval. Conclusions: QTV is elevated in LQTS patients and is correlated with QTc in LQTS. Significant differences with respect to QTV exist among different genotypes. QT interval duration is strongly affected by noninstantaneous heart rate in both C and LQT1 subjects. These findings could improve formulas for QT interval correction and provide insight on cellular mechanisms of QT adaptation. [source]

    The Resting Electrocardiogram in the Management of Patients with Congestive Heart Failure: Established Applications and New Insights

    PACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 1 2007
    JOHN E. MADIAS M.D.
    The resting electrocardiogram (ECG) furnishes essential information for the diagnosis, management, and prognostic evaluation of patients with congestive heart failure (CHF). Almost any ECG diagnostic entity may turn out to be useful in the care of patients with CHF, revealing the non-specificity of the ECG in CHF. Nevertheless a number of CHF/ECG correlates have been proposed and found to be indispensable in clinical practice; they include, among others, the ECG diagnoses of myocardial ischemia and infarction, atrial fibrillation, left ventricular hypertrophy/dilatation, left bundle branch block and intraventricular conduction delays, left atrial abnormality, and QT-interval prolongation. In addition to the above well-known applications of the ECG for patients with CHF, a recently described association of peripheral edema (PERED), sometimes even imperceptible by physical examination, with attenuated ECG potentials, could extend further the diagnostic range of the clinician. These ECG voltage attenuations are of extracardiac mechanism, and impact the amplitude of QRS complexes, P-waves, and T-waves, occasionally resulting also in shortening of the QRS complex and QT interval duration. PERED alleviation, in response to therapy of CHF, reverses all above alterations. These fresh diagnostic insights have potential application in the follow-up of patients with CHF, and in their selection for implantation of cardioverter/defibrillator and/or cardiac resynchronization systems. If sought, PERED-induced ECG changes are abundantly present in the hospital and clinic environments; if their detection and monitoring are incorporated in the clinician's "routine," considerable improvements in the care of patients with CHF may be realized. [source]

    Spatial Distribution of Repolarization Times in Patients with Coronary Artery Disease

    PACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 8 2003
    PETER VAN LEEUWEN
    The potential clinical value of QT dispersion (QTd), a measure of the interlead range of QT interval duration in the surface 12-lead ECG, remains ambiguous. The aim of the study was the temporal and spatial analysis of the QT interval in healthy subjects and in patients with coronary artery disease (CAD) using magnetocardiography (MCG) and surface ECG. Standard 12-lead ECG and 37-channel MCG were performed in 20 healthy subjects, 23 patients with CAD without prior myocardial infarction (MI), 31 MI patients and 11 MI patients with ventricular tachycardia (VT). QTd was increased in CAD without MI compared to normals (ECG46.1 ± 6.0vs42.8 ± 5.0, P < 0.05; MCG66.8 ± 20.3vs49.7 ± 10.8, P < 0.01) and in VT compared to MI (ECG66.8 ± 16.5vs51.9 ± 16.6, P < 0.05; MCG93.6 ± 29.6vs66.8 ± 20.8, P < 0.005). In MCG, spatial distribution of QT intervals in patient groups differed from those in healthy subjects in three ways: (1) greater dispersion, (2) greater local variability, and (3) a change in overall pattern. This was quantified on the basis of smoothness indexes (SI). Normalized SI was higher in CAD without MI compared to normals (3.8 ± 1.1vs2.7 ± 0.6, P < 0.001) and in VT compared to MI (6.4 ± 1.6vs4.2 ± 1.4, P < 0.0005). For the normal-CAD comparison a sensitivity of 74% and a specificity of 80% was obtained, for MI-VT, 100% and 77%, respectively. The results suggest that examining the spatial interlead variability in multichannel MCG may aid in the initial identification of CAD patients with unimpaired left ventricular function and the identification of post-MI patients with augmented risk for VT. (PACE 2003; 26:1706,1714) [source]

    Short QT Interval: A Novel Predictor of Androgen Abuse in Strength Trained Athletes

    ANNALS OF NONINVASIVE ELECTROCARDIOLOGY, Issue 1 2009
    Mohammad Ali Babaee Bigi M.D.
    Objectives: To find the relationship between anabolic androgenic steroids (AAS) using and QT interval in athletes. Methods: Between January 1, 2005 and May 31, 2007, we examined QTc interval duration in 165 consecutive male professional bodybuilders [age: 32.1 ± 4.6 years]. Of these, 79 were AAS users. The control group included 90 sedentary age and gender matched subjects [none of them were AAS users]. Results: The QTc interval of AAS abusing bodybuilders was significantly shorter compared with QTc interval in AAS-free bodybuilders and control group. Short QTc interval (,380 ms) was an independent predictor of AAS abusing in the multivariate analysis. Conclusions: To the best of our knowledge, there is no published report regarding electrocardiographic diagnosis and screening of AAS abusing athletes. In the present study, we present an easy and applicable method to screen and diagnose AAS abusing among professional bodybuilders. In the presence of QTc interval , 380 ms in a bodybuilder, one would predict AAS abusing with 83% sensitivity and 88% specificity. [source]

    Relationship between Genetic Variants in Myocardial Sodium and Potassium Channel Genes and QT Interval Duration in Diabetics: The Diabetes Heart Study

    ANNALS OF NONINVASIVE ELECTROCARDIOLOGY, Issue 1 2009
    Allison B. Lehtinen Ph.D.
    Background: Genetic variants in myocardial sodium and potassium channel genes are associated with prolonged QT interval and increased risk of sudden death. It is unclear whether these genetic variants remain relevant in subjects with underlying conditions such as diabetes that are associated with prolonged QT interval. Methods: We tested single nucleotide polymorphisms (SNPs) in five candidate genes for association with QT interval in a family-based study of subjects with type 2 diabetes mellitus (T2DM). Thirty-six previously reported SNPs were genotyped in KCNQ1, HERG, SCN5A, KCNE1, and KCNE2 in 901 European Americans from 366 families. The heart rate-corrected (QTc) durations were determined using the Marquette 12SL program. Associations between the QTc interval and the genotypes were evaluated using SOLAR adjusting for age, gender, T2DM status, and body mass index. Results: Within KCNQ1 there was weak evidence for association between the minor allele of IVS12 +14T>C and increased QTc (P = 0.02). The minor allele of rs2236609 in KCNE1 trended toward significance with longer QTc (P = 0.06), while the minor allele of rs1805123 in HERG trended toward significance with shorter QTc (P = 0.07). However, no statistically significant associations were observed between the remaining SNPs and QTc variation. Conclusions: We found weak evidence of association between three previously reported SNPs and QTc interval duration. While it appears as though genetic variants in previously identified candidate genes may be associated with QT duration in subjects with diabetes, the clinical implications of these associations in diabetic subjects at high risk for sudden death remain to be determined. [source]

    ECG Evaluation of Ventricular Properties: The Importance of Cardiac Cycle Length

    ANNALS OF NONINVASIVE ELECTROCARDIOLOGY, Issue 2009
    Fabrice Extramiana M.D., Ph.D.
    Ventricular repolarization properties are dependent on cardiac cycle length. The aim of this article is to emphasize the importance of taking into account heart rate influences on QT duration but also on current and future T-wave morphology parameters. The relationship between QT interval duration and RR interval is a fundamental property of the myocardium that is impaired by the presence of channelopathies such as the LQTS or SQTS, but also by the presence of a cardiomyopathy. Assessing this property is also important when the individual QT/RR relationship is used for individual QT correction in the setting of evaluation of drugs' effect on QT duration. T-wave descriptors such as the relative weight of the terminal part of the T-wave, the amplitude of T-wave apex and Principal Component Analysis parameters are also dependent on heart rate. Assessing ventricular repolarisation ECG parameters at different heart rates avoids the need for difficult rate-correction and helps to better understand and characterize ventricular repolarisation properties. [source]

    Changes of QT dispersion in patients with coronary artery disease dependent on different methods of stress induction

    CLINICAL CARDIOLOGY, Issue 3 2000
    B. Hailer M.D.
    Abstract Background: Episodes of stress-induced myocardial ischemia in patients with coronary artery disease (CAD) may cause increases of QT dispersion (QTd). Hypothesis: Aim of this study was to analyze the effect of increasing heart rates on QTd and to compare the effect of different methods of stress induction in patients with varying degrees of CAD when estimating QTd. Methods: We studied 58 patients, 22 with prior myocardial infarction (MI), 25 without MI or wall motion disturbances at rest, and 11 patients without evidence of CAD. Prior to coronary angiography, standard 12-lead ECGs were obtained at rest as well as during dynamic exercise and pharmacologic stress using arbutamine simultaneously with echocardiography. QTd was determined at each stress level by subtracting minimal from maximal QT interval duration. Results: QTd values at rest were not consistently higher in the patients with CAD. At maximal heart rate, QTd was statistically significantly higher in patients with CAD with a better discrimination between groups for pharmacologic stress (p < 0.005 for exercise, p < 0.0001 for arbutamine). Patients after MI had higher QTd values under all conditions than did the groups without MI. As in patients with CAD, the values of this group changed more radically as a result of pharmacologic stress. Conclusion: Patients with CAD can be identified on the basis of QTd under stress. These changes were not as marked in patients with MI as their rest values were already increased. Overall, drug-induced stress produced greater differences than dynamic exercise, suggesting that the ischemic threshold might be lower in the former. [source]

    Steady-State versus Non-Steady-State QT-RR Relationships in 24-hour Holter Recordings

    PACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 3 2000
    GILLES LANDE
    The aim of the present study was to investigate the QT-RR interval relationship in ambulatory ECG recordings with special emphasis on the physiological circumstances under which the QT-RR intervals follow a linear relation. Continuous ECG recordings make it possible to automatically measure QT duration in individual subjects under various physiological circumstances. However, identification of QT prolongation in Holter recordings is hampered by the rate dependence of QT duration. Comparison of QT duration and QT interval rate dependence between different individuals implies that the nature of the QT-RR relationship is defined in ambulatory ECG. Holter recordings were performed in healthy volunteers at baseline and after administration of dofetilide, a Class III antiarrhythmic drug. After dofetilide, beat-to-beat automated QT measurements on Holter tapes were compared with manually measured QT intervals on standard ECGs matched by time. The QT-RR relationship was analyzed at baseline in individual and group data during three different periods: 24-hour, daytime, and nighttime. Data were collected under steady-state or non-steady-state conditions of cycle length and fitted with various correction formulae. Our study demonstrated an excellent agreement between manually and automated measurements. The classic Bazett correction formula did not fit the QT-RR data points in individual or group data. When heart beats were selected for a steady rhythm during the preceding minute, QT-RR intervals fit a linear relationship during the day and night periods, but not during the 24-hour period in both individual and group data. In contrast, in the absence of beat selection, data fit a more complex curvilinear relationship irrespective of the period. Our study provides the basis for comparison of QT interval durations and QT-RR relationships between individuals and between groups of subjects. [source]