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  • 1
    Electronic Resource
    Electronic Resource
    Clinical Characteristics of Patients With Spontaneous or Inducible Ventricular Fibrillation Without Apparent Heart Disease Presenting with J Wave and ST Segment Elevation in Inferior Leads (2000)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of cardiovascular electrophysiology 11 (2000), S. 0 
    Details
    ISSN: 1540-8167
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Ventricular Fibrillation with J Wave in Inferior Leads. Introduction: The clinical characteristics of three patients with spontaneous or inducible ventricular fibrillation (VF) without apparent heart disease, who presented with J wave and ST segment elevation in inferior leads, are described. Methods and Results: All patients were male and experienced syncope. Their symptoms occurred at night or early in the morning. Holter ECG revealed infrequent premature ventricular complexes. Injection with disopyramide 2 mg/kg augmented ST segment elevation. Conclusion: These characteristics were very similar to those of patients with Brugada syndrome. These three patients with these specific features might have a variant of Brugada syndrome.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1540-8167.2000.tb00062.x
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  • 2
    Electronic Resource
    Electronic Resource
    Effect of Sodium Channel Blockers on ST Segment, QRS Duration, and Corrected QT Interval in Patients with Brugada Syndrome (2000)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of cardiovascular electrophysiology 11 (2000), S. 0 
    Details
    ISSN: 1540-8167
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: ST Elevation in Brugada Syndrome. Introduction: Brugada syndrome is characterized by an ST segment elevation in leads V1-V3 and a high incidence of ventricular fibrillation (VF). A mutation in a cardiac Na+ channel gene, SCN5A, has been linked to Brugada syndrome, and sodium channel blockers have been shown to be effective in unmasking the syndrome when concealed. The aim of this study was to examine the effects of Na+ channel blockers on ST segment elevation, QRS, corrected QT (QTc) interval, and ventricular arrhythmias in patients with Brugada syndrome. Methods and Results: We examined the effects of three different Na+ channel blockers (flecainide, disopyramide, and mexiletine) on the amplitude of the ST segment 20 msec after the end of QRS (ST20), QRS duration, QTc interval measured from 12-lead ECG, and ventricular arrhythmias in 12 Brugada and 10 control patients. Maximum ST20 observed in the V2 or V3 leads under baseline conditions was greater in the Brugada patients than in control patients, whereas QRS duration and maximum QTc interval were no different between the two groups. Flecainide and disopyramide, but not mexiletine, significantly increased maximum ST20 and QRS duration in both groups, although these effects were much more pronounced in the Brugada patients. The increases in ST20 and QRS duration with flecainide were significantly larger than those with disopyramide. An increase of 0.15 mV in ST20 with flecainide separated the two groups without overlap. Ventricular premature complexes developed only with flecainide in Brugada patients (3/12) displaying a marked ST elevation but not widening of QRS. Conclusion: Our findings suggest that Na+ channel blockers amplify existing INa and possibly other ion channel defects, with a potency inversely proportional to the rate of dissociation of the drug from the Na+ channel, thus causing a prominent elevation of the ST segment and, in some cases, prolongation of QRS duration in patients with Brugada syndrome.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1540-8167.2000.01320.x
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  • 3
    Electronic Resource
    Electronic Resource
    EFFECT OF EXERCISE ON PLASMA ADRENOMEDULLIN AND NATRIURETIC PEPTIDE LEVELS IN MYOCARDIAL INFARCTION (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Clinical and experimental pharmacology and physiology 24 (1997), S. 0 
    Details
    ISSN: 1440-1681
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: 1. We investigated the effect of exercise on plasma adreno-medullin, atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) concentrations and studied the relationship between these peptides and haemodynamic parameters in nine patients with old myocardial infarction (MI) and in eight normal subjects.2. The exercise protocol consisted of two fixed work loads (40 and 80 W) for 4 min each and venous blood samples were taken at rest, during each exercise stage and after exercise while monitoring the mean arterial pressure (MAP) and heart rate (HR). In MI, pulmonary arterial pressure (PAP), pulmonary capillary wedge pressure (PCWP), left ventricular end-diastolic pressure (LVEDP) and cardiac output (CO) were measured throughout exercise.3. Adrenomedullin levels did not significantly increase with exercise. Adrenomedullin levels correlated with PAP and PCWP at rest (P 〈 0.05). Atrial natriuretic peptide levels correlated with PAP, PCWP and LVEDP throughout exercise (P 〈 0.05) but, on multiple regression analysis, PCWP correlated only with ANP (P 〈 0.01). Brain natriuretic peptide levels correlated with LVEDP throughout exercise (P 〈 0.01) and its increment correlated closely with basal BNP levels at rest (P 〈 0.01).4. These results suggest that adrenomedullin does not respond to the acute haemodynamic changes of exercise, whereas ANP responds to it and PCWP is the major stimulus factor. Brain natriuretic peptide responds to exercise in proportion to the basal synthesis of BNP in patients with left ventricular dysfunction and LVEDP may play a role in increasing BNP during exercise.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1440-1681.1997.tb01194.x
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  • 4
    Electronic Resource
    Electronic Resource
    Early Afterdepolarizationlike Activity in Patients with Class IA Induced Long QT Syndrome and Torsades de Pointes (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Pacing and clinical electrophysiology 20 (1997), S. 0 
    Details
    ISSN: 1540-8159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Early afterdepolarizations (EADs) have been linked to the mechanism of torsades de pointes in long QT syndrome. The purpose of this study was to investigate the role of EADs in Class IA induced torsades de pointes. We studied nine patients with Class IA induced torsades de pointes at the time this arrhythmia was present (acute period, n = 7) and after Class IA therapy was discontinued (chronic period, n = 6). ECCs and monophasic action potentials were recorded in both periods. In the chronic period, electrophysiological studies were performed before and after disopyramide infusion. In the acute period, QTc interval was markedly prolonged (655 ± 32 ms1/2), and EAD-like activity was recorded in all patients. QTc interval returned to normal (428 ± 45 ms1/2) and EAD-like activity disappeared after discontinuation of IA drug. Although, in the chronic period, disopyramide infusion prolonged QTc interval from 428 ± 48 ms1/2 to 479 ± 31 ms1/2 and induced EAD in three of six patients, the degree was not as marked as observed in the acute period. EADs may play an important role in the genesis of long QT and torsades de pointes. Disopyramide infusion in the chronic period could not reproduce marked repolarization ahnormalities and torsades de pointes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1540-8159.1997.tb03888.x
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  • 5
    Electronic Resource
    Electronic Resource
    Development of a servo-controller of heart rate using a cycle ergometer (1999)
    Springer
    Heart and vessels 14 (1999), S. 177-184 
    Details
    ISSN: 1615-2573
    Keywords: Negative feedback ; Transfer function ; Exercise
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In exercise training, precise control of exercise intensity would maximize the training efficacy while minimizing risks. To adjust work rate, heart rate (HR) has been used as a measure of exercise intensity. Thus, we developed a servo-controller of HR using a cycle ergometer. After estimating the transfer function from work rate to HR, we optimized feedback parameters for achieving a quick and stable HR response by means of a computer simulation. We then examined the performance of the servo-controller of HR in 55 healthy volunteers. We set the target HR at 60% and 75% of the age-predicted maximum HR. Times required for HR to reach 90% of the target HR were 136 ± 33 and 137 ± 22s in the respective protocols. Standard deviations of the steady-state difference between the target and measured HRs were 2.5 ± 0.6 and 3.8 ± 1.1 beats/min. We conclude that the developed servo-controller makes it possible to precisely regulate HR and, thereby, exercise intensity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02482304
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  • 6
    Electronic Resource
    Electronic Resource
    Transient oxygen uptake response to exercise characterizes functional capacity of the cardiocirculatory system in patients with chronic heart failure: a random stimulus approach (1998)
    Springer
    European journal of applied physiology 78 (1998), S. 333-339 
    Details
    ISSN: 1439-6327
    Keywords: Key words: Exercise ; Heart failure ; Oxygen uptake ; Transient response
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The transient response of oxygen uptake (V˙O2) to submaximal exercise, known to be abnormal in patients with cardiovascular disorders, can be useful in assessing the functional status of the cardiocirculatory system, however, a method for evaluating it accurately has not yet been established. As an alternative approach to the conventional test at constant exercise intensity, we applied a random stimulus technique that has been shown to provide relatively noise immune responses of system being investigated. In 27 patients with heart failure and 24 age-matched control subjects, we imposed cycle exercise at 50 W intermittently according to a pseudo-random binary (exercise-rest) sequence, while measuring breath-by-breath V˙O2. After determining the transfer function relating exercise intensity (W˙) to V˙O2 and attenuating the high frequency ranges (〉6 exercise-rest cycles · min−1), we computed the high resolution band-limited (0–6 cycles · min−1) V˙O2 response (0–120 s) to a hypothetical step exercise. The V˙O2 response showed a longer time constant in the patients than in the control subjects [47 (SD 37) and 31 (SD 8) s, respectively, P 〈 0.05]. Furthermore, the amplitude of the V˙O2 response after the initial response was shown to be significantly smaller in the patients than in the control subjects [176 (SD 50) and 267 (SD 54) ml · min−1 at 120 s]. The average amplitude over 120 s correlated well with peak V˙O2 (r = 0.73) and ΔV˙O2/ΔW˙ (r = 0.70), both of which are well-established indexes of exercise tolerance. The data indicated that our band-limited V˙O2 step response using random exercise was more markedly attenuated and delayed in the patients with heart failure than in the normal controls and that it could be useful in quantifying the overall functional status of the cardiocirculatory system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004210050428
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