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  • 1
    Electronic Resource
    Electronic Resource
    Relationship Between Heart Rate Turbulence and Heart Rate, Heart Rate Variability, and Number of Ventricular Premature Beats in Coronary Patients (2004)
    350 Main Street , Malden , MA 02148-5018 , USA , and 9600 Garsington Road , Oxford OX4 2DQ , UK . : Blackwell Science Inc
    Journal of cardiovascular electrophysiology 15 (2004), S. 0 
    Details
    ISSN: 1540-8167
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Introduction: Heart rate variability (HRV) illustrates regulation of the heart by the autonomic nervous system whereas heart rate turbulence (HRT) is believed to reflect baroreflex sensitivity. The aim of this study was to determine the association between HRT and HRV parameters and the relationship between HRT parameters and heart rate and number of ventricular premature beats (VPBs) used to calculate HRT parameters. Methods and Results: In 146 patients (117 males and 29 females; mean age 62 years) with coronary artery disease, a 24-hour ECG Holter monitoring was performed to calculate mean heart rate (RR interval), number of VPBs, time- and frequency-domain HRV parameters and two HRT parameters: turbulence onset (TO) and turbulence slope (TS). Univariate and multivariate regression analyses were performed to evaluate the association between tested parameters. Significant correlation between TS and mean RR interval was observed (r = 0.42; p 〈 0.001), while no association for TO vs. RR interval was found. TS values were significantly higher in patients with less than 10 VPBs/24 hours than in patients with more frequent VPBs. Significant associations between HRT and HRV parameters were found with TS showing stronger correlation with HRV parameters than TO (r value ranging from 0.35 to 0.62 for TS vs. −0.16 to −0.38 for TO). Conclusion: HRT parameters correlate strongly with HRV parameters indicating that HRT should be considered as a reflection of both baroreceptors response and overall autonomic tone. Heart rate dependence of turbulence slope indicates the need to adjust this parameter for heart rate. (J Cardiovasc Electrophysiol, Vol. 15, pp. 731-737, July 2004)
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1540-8167.2004.03613.x
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  • 2
    Electronic Resource
    Electronic Resource
    History of Electrocardiology (1996)
    Oxford, UK : Blackwell Publishing Ltd
    Annals of noninvasive electrocardiology 1 (1996), S. 0 
    Details
    ISSN: 1542-474X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1542-474X.1996.tb00286.x
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  • 3
    Electronic Resource
    Electronic Resource
    Variable Expression of Long QT Syndrome Among Gene Carriers from Families with Five Different HERG Mutations (2001)
    Oxford, UK : Blackwell Publishing Ltd
    Annals of noninvasive electrocardiology 7 (2001), S. 0 
    Details
    ISSN: 1542-474X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Objectives: This study assessed the phenotypic variability of LQTS in carriers with the same and with different mutations in the LQT2 gene.Background: Mutations of ion-channel genes are known to cause the long QT syndrome (LQTS), a disorder associated with distinctive genotypic-specific electrocardiographic patterns and variable clinical expression.Methods: Clinical and electrocardiographic characteristics were assessed in five large LQTS families, each with a different mutation of the HERG gene (LQT2; n = 469, 69% genotyped, 102 carriers). One mutation was located on the N-terminus and the other four on the C-terminus of the HERG channel protein.Results: The QTc duration and the frequency of cardiac events (syncope and LQTS-related cardiac arrest/deatht were similar among carriers with the five HERG mutations. QTc was as variable in carriers of the same mutation as it was among carriers with different HERG mutations (P = 0.19). Qualitative assessment of the electrocardiograms revealed extensive intra-and interfamilial variability in T-vvave morphology. Among carriers with multiple electrocardiograms extending over 2 to 7 years, variation in QTc over time was minimal. A strong association was found between QTc and the occurrence of cardiac events in carriers of all five mutations.Conclusions: The clinical expression of LQTS was equally variable in carriers from families with the same or different HERG mutations. These findings highlight the complexity of the clinical phenotype in this Mendelian dominant disorder and suggest that one or more modifier genes contribute to the variable expression of this syndrome. A.N.E. 2002;7(1):40–46
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1542-474X.2001.tb00137.x
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  • 4
    Electronic Resource
    Electronic Resource
    Heart Rate Variability in Patients with Congenital Long QT Syndrome (2001)
    Oxford, UK : Blackwell Publishing Ltd
    Annals of noninvasive electrocardiology 6 (2001), S. 0 
    Details
    ISSN: 1542-474X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Background: The congenital long QT syndrome (LQTS) affecting myocardial repolarization is caused by mutations in different cardiac potassium or sodium channel genes. Adrenergic triggers are known to initiate life-threatening torsade de pointes ventricular tachycardias in LQTS patients, and anti-adrenergic therapy has been shown to be effective in many cases. Despite this well-documented adrenergic component, the data about autonomic modulation of the heart rate in LQTS, as described by heart rate variability (HRV) analysis, are very limited.Methods: Conventional time- and frequency-domain and newer nonlinear measures of HRV were compared in resting conditions among 27 LQTS patients with gene mutations at the LQT1 (n = 8), LQT2 (n = 10) or LQT3 (n = 9) loci and 34 LQTS noncarrier family members.Results: None of the conventional time- or frequency-domain or newer nonlinear measures of HRV differed significantly between the LQTS carriers and LQTS noncarriers or between the LQT1, LQT2, and LQT3 carriers.Conclusions: These findings suggest that baseline cardiac autonomic modulation of the heart rate measured in resting conditions by traditional or newer nonlinear measures of HRV is not altered in LQTS patients. Furthermore, no differences are observed in HRV parameters between LQTS patients with potassium (KvLQT1, HERG), and sodium (SCN5A) ion channel gene mutations. HRV analysis in resting conditions does not improve phenotypic characterization of LQTS patients. A.N.E. 2001;6(4):298–304
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1542-474X.2001.tb00122.x
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  • 5
    Electronic Resource
    Electronic Resource
    Dispersion of Repolarization: Time to Move Beyond QT Dispersion (2000)
    Oxford, UK : Blackwell Publishing Ltd
    Annals of noninvasive electrocardiology 5 (2000), S. 0 
    Details
    ISSN: 1542-474X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Background: Over the last few years, the concept of dispersion of repolarization, evaluated as interlead variability of QT interval duration in surface ECG, emerged as a possible tool to identify patients at high-risk for cardiac arrhythmias. Despite substantial progress in understanding of the electrophysiological basis for dispersion of repolarization, the question remains whether interlead differences in ECG- recorded T-wave duration and morphology (QT dispersion) indicate heterogeneity in ventricular recovery time and pattern.Methods and Results: Several studies investigated the prognostic significance of QT dispersion for predicting all-cause mortality, sudden cardiac, and arrhythmic deaths. Some of those studies indicated significant and independent predictive value of QT dispersion whereas others negated such an association. Despite these controversial results, there is concern that substantial overlap in QT dispersion values between patients with and without cardiac events limits or even precludes clinical usefulness of QT dispersion for predicting future cardiac events. The methodological and conceptual limitations of QT dispersion measurements further discourage the bedside use of this noninvasive ECG parameter. Ionic channel phenomena determine the voltage and time components of the T-wave, the T-loop, and the QT interval duration. Since the ST-T area is more representative of recovery times than QT interval duration, future efforts should be focused on developing and testing new automatically quantified parameters describing abnormalities of the T-wave configuration and/or T-loop morphology. Electrophysiologic meaning and prognostic significance of these ECG parameters remain to be studied.Conclusion: In light of conceptual and methodological limitations of QT dispersion analysis, bedside use of this method should be discouraged and the time has come to move beyond QT dispersion and focus on evaluating clinical usefulness of repolarization morphology in risk-stratification. studies. A.N.E. 2000;5(4):373-381
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1542-474X.2000.tb00076.x
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  • 6
    Electronic Resource
    Electronic Resource
    What to Expect from Electrocardiology at the Beginning of 2000? (2000)
    Oxford, UK : Blackwell Publishing Ltd
    Annals of noninvasive electrocardiology 5 (2000), S. 0 
    Details
    ISSN: 1542-474X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1542-474X.2000.tb00240.x
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  • 7
    Electronic Resource
    Electronic Resource
    Correlation Method for Detection of Transient T-Wave Alternans in Digital Holter ECG Recordings (1999)
    Oxford, UK : Blackwell Publishing Ltd
    Annals of noninvasive electrocardiology 4 (1999), S. 0 
    Details
    ISSN: 1542-474X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Background:Spectral and complex demodulation methods for detection of microvolt T-wave alternans (TWA) have limited ability to identify transient (nonstationary) TWA episodes. We aimed to develop and test new time-domain technique allowing TWA detection and quantification in as few as 7 consecutive beats from sinus rhythm ECGs. Methods and results:Quantification of TWA during sinus rhythm required preprocessing consisting of: low-pass filtering, RR stability testing, baseline and respiratory modulation removal, and T-wave windowing and synchronization. Our time-domain correlation method (CM) detects TWA by computing, for each consecutive T wave, an alternans correlation index based on a crosscorrelation technique. CM allows quantitative analysis of the amplitude, duration, and overall magnitude of the TWA episode. The technical performance of CM was confirmed in testing with simulated TWA of varying amplitude, duration, and noisy conditions. The clinical performance of CM was demonstrated by analyzing digital Holter recordings of 39 long QT syndrome patients compared to 36 healthy subjects. CM identified TWA in 17 (44%) patients with nonstationary TWA detected in 8. Conclusion:Our computer algorithms consisting of ECG preprocessing and TWA quantification by the correlation method provides the opportunity to detect nonstationary and stationary TWA in sinus rhythm of digital Holter ECG recordings. A.N.E. 1999;4(4):416–424
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1542-474X.1999.tb00232.x
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  • 8
    Electronic Resource
    Electronic Resource
    The Relation of QT Dispersion to Spontaneous Ventricular Arrhythmias During the Acute Phase of Myocardial Infarction (1998)
    Oxford, UK : Blackwell Publishing Ltd
    Annals of noninvasive electrocardiology 3 (1998), S. 0 
    Details
    ISSN: 1542-474X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Background: QT dispersion is associated with ventricular arrhythmias and sudden death among patients with a previous myocardial infarction (Ml). The relationship between QT dispersion and ventricular arrhythmias during the acute phase of Ml is uncertain.Methods: Patients enrolled in the Multicenter Study of Silent Myocardial Ischemia who had first Q wave myocardial infarctions (n = 363) were screened for the presence of ventricular arrhythmias during the initial hospitalization. Twelve patients had ventricular fibrillation, and 18 patients had an episode of monomorphic ventricular tachycardia. Each patient who had ventricular arrhythmias was matched with four controls on the basis of age, peak creatine kinase, thrombolysis, and the presence of congestive heart failure. The final study population consisted of 150 patients: 12 patients with ventricular fibrillation (VF+) who were compared to 48 controls (VF—), and 18 patients with ventricular tachycardia (VT+) who were compared to 72 controls (VT–). The RR, QRS, and QT intervals were measured manually using standard 12-lead ECGs (25 mm/s) obtained after hospital admission. The maximal QT dispersion (maximum — minimum value) was calculated. Multivariate logistic regression analysis was performed to determine if QT dispersion was independently associated with ventricular arrhythmias during the acute phase of Ml.Results: QT dispersion was significantly greater in VF+ patients compared to VF— patients (89 ± 18 ms vs 66 ± 22 ms, P 〉 0.01). QT dispersion was similar in VT+ and VT— patients (68 ± 25 ms vs 68 ± 26 ms, P = NS). QT dispersion was the only variable that was independently associated with ventricular fibrillation (OR 1.7 for each 10-ms increment in QT dispersion; 95% Cl 1.2–2.6; P = 0.008). QT dispersion was not associated with monomorphic ventricular tachycardia (OR 1.0; 95% Cl 0.8–1.2; P = NS).Conclusion: QT dispersion is independently associated with ventricular fibrillation, but not monomorphic ventricular tachycardia, during the acute phase of Ml.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1542-474X.1998.tb00408.x
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  • 9
    Electronic Resource
    Electronic Resource
    Contribution of the Wavelet Analysis to the Noninvasive Electrocardiology (1998)
    Oxford, UK : Blackwell Publishing Ltd
    Annals of noninvasive electrocardiology 3 (1998), S. 0 
    Details
    ISSN: 1542-474X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1542-474X.1998.tb00030.x
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  • 10
    Electronic Resource
    Electronic Resource
    Gene-Specific Therapy for Long QT Syndrome (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Annals of noninvasive electrocardiology 2 (1997), S. 0 
    Details
    ISSN: 1542-474X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Background: One form of the hereditary long QT syndrome (LQT-3) has recently been shown to be caused by the SCN5A mutation of the human cardiac sodium channel. Cellular studies have suggested that type lb antiarrhythmics may be potentially therapeutic via preferential blockade of the resulting abnormal late inward sodium current. To test this hypothesis, we implemented a pilot study to evaluate the potential for long-term, gene-specific therapy in patients with this disease.Methods and Results: The effects of short-term intravenous lidocaine and oral tocainide were studied in three siblings: two carriers of the SCN5A mutation; and one noncarrier. The two carriers had prolonged QT intervals at baseline, 531 ms, and 566 ms, which markedly shortened with intravenous lidocaine to 438 and 482 ms, respectively. Tocainide-induced correction of the QT interval was similar in both carriers. The noncarrier did not have any significant change in the QT with either drug. One carrier was then placed on outpatient therapy with oral tocainide, and has demonstrated persistent normalization of the QT interval and T wave morphology during the past 10 months.Conclusion: This is the first demonstration of long-term outpatient treatment in LQT-3 using oral tocainide during a 10-month period. QT shortening was achieved by both intravenous lidocaine and oral tocainide, with no adverse affects. The predominant effect was a reduction in the QT onset interval, suggesting that blockade of the mutant sodium current allows repolarization to begin at an earlier time during the action potential.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1542-474X.1997.tb00336.x
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