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  • 1
    Electronic Resource
    Electronic Resource
    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 
    ISSN: 1540-8167
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Introduction: Atrial tachycardia and chronic heart failure (CHF) are associated with elevated levels of atrial natriuretic peptide (ANP) and its amino terminal part NT-ANP. Chronic high atrial rates may cause CHF due to a rapid ventricular response. The aim of this study was to establish the contribution of elevated atrial rate and of high ventricular rate, resulting in CHF, on ANP and NT-ANP levels during chronic atrial tachycardia. Methods and Results: Thirteen goats (AV-paced group) were subjected to 4 weeks of rapid AV pacing with an atrial and ventricular rate of 240 beats/min. Another five goats (A-paced group) were subjected to 4 weeks of atrial pacing at 240 beats/min while the ventricular rate was kept low and regular at 80 beats/min. Pacing was interrupted only for measurement of right atrial (RA) and left ventricular (LV) diameter and sampling for ANP, NT-ANP, and renin. In the AV-paced group, RA and LV diameter reached 152% and 109% of baseline values, respectively. Both ANP and NT-ANP (8.3 ± 9.2 pmol/L and 0.5 ± 0.4 nmol/L at baseline, respectively) increased progressively (53.1 ± 37.9 pmol/L and 2.0 ± 0.9 nmol/L, respectively, after 4 weeks). There was a significant correlation between the magnitude of atrial dilation and natriuretic peptide levels after 3 days. In A-paced goats, however, RA and LV diameters did not change. Furthermore, ANP and NT-ANP levels (9.1 ± 6.0 pmol/L and 0.8 ± 0.2 nmol/L at baseline, respectively) were unchanged after 4 weeks (5.3 ± 3.4 pmol/L and 0.6 ± 0.2 nmol/L, respectively). Conclusion: Elevated levels of ANPs during chronic atrial tachycardia are related to a high ventricular rate rather than a high atrial rate alone. Rather than atrial tachycardia, the atrial hemodynamic burden is an important determinant of the sustained ANP response.
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  • 2
    ISSN: 1540-8167
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Natriuretic Peptide System in AF. Introduction: Circulating cardiac natriuretic peptides play an important role in maintaining volume homeostasis, especially during conditions affecting hemodynamics. During atrial fibrillation (AF), levels of plasma atrial natriuretic peptide (ANP) becomes elevated. The aim of this study was to gather information about gene expression of the natriuretic peptide system on the atrial level in patients with AF. Methods and Results: Right atrial appendages of 36 patients with either paroxysmal or persistent AF were compared with 36 case matched controls in sinus rhythm for mRNA expression of pro- atrial natriuretic peptide (pro-ANP), pro-brain natriuretic peptide (pro-BNP), and their natriuretic peptide receptor type-A (NPR-A). We investigated patients without (n = 36) and with (n = 36) valvular disease. Persistent AF was associated with higher mRNA expression of pro-BNP (+66%, P = 0.04, in patients without valvular disease, and +69%, P 〈 0.01, in patients with valvular disease) and lower mRNA expression of NPR-A (-58%, P = 0.02, in patients witbout valvular disease, and -62%, P 〈 0.01, in patients with valvular disease). The mRNA content of pro-ANP was only increased in patients with valvular disease (+12%, P = 0.03). No changes were observed in patients with paroxysmal AF. Conclusion: This study demonstrates that persistent, but not paroxysmal, AF induces alterations in gene expression of pro-BNP and NPR-A on the atrial level. Although AF generally is associated with an increase of plasma ANP level, a change in mRNA content of pro-ANP is only observed in the presence of concomitant valvular disease and is of minor magnitude.
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  • 3
    Electronic Resource
    Electronic Resource
    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 
    ISSN: 1540-8167
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Introduction: Atrial fibrillation (AF) is characterized by an irregularly irregular (“random”) heart beat. However, controversy exists whether the ventricular rhythm in AF is truly random. We investigated randomness by constructing three-dimensional RR interval plots (3D plots), allowing identification of “clustering” of RR intervals. It was hypothesized that electrical cardioversion (ECV) would be more effective in AF patients with clustering, because clustering might reflect a higher degree of organization of atrial fibrillatory activity. Methods and Results: The study group consisted of 66 patients (44 men and 22 women; mean age 68 ± 11 years,) who were referred for ECV because of persistent AF. Twenty-four-hour Holter recordings were used to construct 3D plots by plotting each RR interval (x axis) against the previous RR interval (y axis) and the number of occurrences of each of these x,y combinations (z axis). A clustering index was calculated as the percentage of beats within the peaks in the 3D plot. Based on the 3D plots, clustering of RR intervals was present in 31 (47%) of the 66 patients. ECV was effective in restoring sinus rhythm in 29 (94%) of these 31 patients, whereas sinus rhythm was restored in only 25 (71%) of the remaining 35 patients without clustering (P = 0.020). The clustering index ranged from 〈2% in the 12 patients with failed ECV to 〉8% in the 32 patients with sinus rhythm at the end of the study (4 weeks after the ECV); the clustering index in the 22 patients with a relapse of AF after effective ECV was intermediate (P = 0.034 and P = 0.042, respectively). Conclusion: This study indicates that ECV is more effective in restoring sinus rhythm in AF patients with clustering compared to patients in whom no clustering is apparent on 3D plots. In addition, the degree of clustering appears to be predictive of the overall outcome of ECV; the higher the degree of clustering, the higher the likelihood of sinus rhythm at follow-up.
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Inc
    Journal of cardiovascular electrophysiology 13 (2002), S. 0 
    ISSN: 1540-8167
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
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  • 5
    ISSN: 1540-8167
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Pacemaker Treatment in LQT3 and Brugada Syndrome. Introduction: We recently identified a novel mutation of SCN5A (1795insD) in a large family with features of both long QT syndrome type 3 and the Brugada syndrome. The purpose of this study was to detail the clinical features and efficacy of pacemaker therapy in preventing sudden death in this family. Methods and Results: The study group consisted of 116 adult family members: 60 carriers (29 males) and 56 noncarriers (28 males) of the mutant gene. Investigations included 24-hour Holter monitoring, ergometry, and electrophysiologic studies. Mean, lowest, and highest heart rate were lower in the carriers, but heart rate variability was comparable. In carriers, disproportional QT prolongation was present during bradycardia. No complex ventricular ectopy was recorded, and there were fewer isolated premature beats (both ventricular and atrial) in carriers. All patients were asymptomatic, except for two individuals who experienced syncope; in one of these patients, asystolic episodes (up to 9 sec) were repeatedly recorded. Prolonged HV intervals were present in 5 of 6 patients. Thirty carriers received a prophylactic backup pacemaker. During median follow-up of 4.5 years (range 0.0 to 22.6), their survival rate was 100%. There were five sudden deaths among the remaining 30 carriers without a pacemaker (P = 0.019). Conclusion: This family with a high incidence of nocturnal sudden death is characterized by bradycardia-dependent QT prolongation, intrinsic sinus node dysfunction, and generalized conduction abnormalities. There is a striking absence of complex ventricular ectopy, and pacemaker implantation was effective in preventing sudden death. These findings raise the possibility of a bradycardic rather than tachycardic mode of death.
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  • 6
    Electronic Resource
    Electronic Resource
    350 Main Street , Malden , MA 02148 , USA , and 9600 Garsington Road , Oxford OX4 2DQ , UK . : Blackwell Science Inc
    Annals of noninvasive electrocardiology 8 (2003), S. 0 
    ISSN: 1542-474X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Background: Recently, we identified a novel mutation of SCN5A (1795insD) in a large family with LQTS3. The aim of this study was to assess whether the various proposed corrections of the QT interval to heart rate help to improve the identification of carriers of the mutant gene. Methods: The study group consisted of 101 adult family members: 57 carriers and 44 noncarriers (mean age 44.6 ± 14.6 and 40.3 ± 12.8 years, respectively). In all individuals a 12-lead ECG, exercise ECG, and 24-hour Holter ECG were obtained. Results: Correction for heart rate significantly improved the diagnostic performance of the QT interval. Diagnostic performance of the Bazett formula was similar to that of the newer formulas (Fridericia, Hodges, Framingham, and a logarithmic formula). At a cut-off value of 440 ms, the Bazett corrected QT interval was associated with a sensitivity and specificity of 90% and 91%, respectively. Using the 24-hour Holter ECG, a prolonged QTc at heart rates less than 60 beats/min was almost pathognomonic for genetic mutation (sensitivity and specificity both 99%), whereas the QTc calculated at the lowest heart rate using Bazett's formula provided full discrimination. Conclusion: In the present family, the resting ECG gave a good indication about the presence or absence of genetic mutation but a 24-hour Holter recording was mandatory to ascertain the diagnosis. In the diagnosis of this form of LQTS3, Bazett's formula was at least as good as other proposed corrections of the QT interval to heart rate.
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  • 7
    ISSN: 1540-8159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Atrial fibrillation (AF) shortens the atrial effective refractory period (AERP). To investigate the role of the autonomic nervous system during this so-called electrical remodeling of the atria (ERA) and during recovery from ERA we analyzed heart rate variability (HRV). In 12 goats atrioventricular (300:150 beats/min) pacing was performed for 24 hours, interrupted at 4, 8, 16, and 24 hours for recording of 500 atrial (AA) intervals during sinus rhythm and measurement of the AERP430 ms at 7.4 ± 0.6 sites. After 24 hours, pacing was stopped and the electrophysiological study and recording of the AA intervals was repeated at 4, 8, 16, and 24 hours after cessation of pacing. Time- and frequency-domain parameters were computed from each 500 AA interval recording. After 24 hours of rapid pacing the AERP had shortened significantly (147 ± 5.6 to 102 ± 6.4 ms, P 〈 0.0001). No significant changes in HRV and dispersion of refractoriness (ΔAERP) (47 ± 7.1 to 44 ± 4.2 ms) were observed. After cessation of pacing, the AERP prolonged again (102 ± 6.4 to 135 ± 8.8 ms, P 〈 0.0001) and was paralleled by a significant increase in ΔAERP (44 ± 4.2 to 63 ± 7.1 ms, P = 0.01). Furthermore, HRV increased significantly. At each time point an inverse relation between the logarithmically transformed vagal parameter HF (InHF) and AERP was observed. We calculated the mean InHF for each goat using all time points and used the median value to divide the 12 goats into high and low vagal tone groups. We compared the degree of ERA and recovery from ERA for both groups. The AERP shortened 47.4 ± 6.5 versus 43.0 ± 5.0 ms (NS) for goats with high and low vagal tone, respectively. During recovery from ERA the AERP lengthened 23.6 ± 4.0 versus 42.5 ± 1.7 ms (P = 0.001) for goats with high and low vagal tone, respectively. Multivariate regression analysis indicated a short AERP as the single independent determinant of the inducibility of AF during ERA and recovery from ERA (P 〈 0.0001). During recovery from ERA, the AERP prolonged and vagal tone and ΔAERP increased. A high vagal tone during recovery from ERA was associated with a short AERP and an attenuated recovery of ERA.
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  • 8
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Pacing and clinical electrophysiology 20 (1997), S. 0 
    ISSN: 1540-8159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The factors that determine the individual susceptibility to vasovagal syncope (VVS) are largely unknown, including the role of the autonomic nervous system. We therefore studied common vagal and sympathetic reflexes in 12 patients with WS (mean age 37 (18–75) years, 6 men). The Valsalva maneuver and deep breathing were performed to assess vagal responsiveness and mental arithmetic stress; the cold-pressor test and isometric handgrip were performed to assess sympathetic responsiveness. Standing up was performed to assess the combined responsiveness. With the exception of a subnormal response to deep breathing in one patient, all vagal tests were normal. In contrast, the response to mental stress, the cold-pressor test, and isometric handgrip was subnormal in 4 patients, 6 patients, and 4 patients, respectively. The response to standing up was normal in all patients. It is concluded that many patients with WS are characterized by normal vagal responsiveness, but sympathetic hyporesponsiveness. Sympathetic hy-poresponsiveness might explain the inadequate vasoconstriction, which plays an important, early role in WS.
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  • 9
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Pacing and clinical electrophysiology 22 (1999), S. 0 
    ISSN: 1540-8159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: A 54-year-old man presented with total atrioventricular (AV) block 3 months after dynamic cardiomyoplasty was performed because of heart failure due to idiopathic dilated cardiomyopathy. Though the cardiomyostimulator acted as a back-up pacemaker, a DDDR pacemaker was implanted to optimize hemodynamics. During testing no cross-sensing or cross-stimulation between the pacemaker and the cardiomyostimulator was demonstrable. The synchronization delay, however, had to be adjusted.
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  • 10
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Cardiac conduction disorders slow the heart rhythm and cause disability in millions of people worldwide. Inherited mutations in SCN5A, the gene encoding the human cardiac sodium (Na+) channel, have been associated with rapid heart rhythms that occur suddenly and are ...
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