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  • 1
    Electronic Resource
    Electronic Resource
    Atrial Natriuretic Peptides During Experimental Atrial Tachycardia: (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: 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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1540-8167.2004.04093.x
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  • 2
    Electronic Resource
    Electronic Resource
    Electrical Remodeling and Atrial Dilation During Atrial Tachycardia are Influenced by Ventricular Rate: Role of Developing Tachycardiomyopathy (2001)
    Oxford, UK : Blackwell Science Inc
    Journal of cardiovascular electrophysiology 12 (2001), S. 0 
    Details
    ISSN: 1540-8167
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Atrial Remodeling in Tachycardiomyopathy. Introduction: Atrial fibrillation (AF) and congestive heart failure (CHF) are two clinical entities that often coincide. Our aim was to establish the influence of concomitant high ventricular rate and consequent development of CHF on electrical remodeling and dilation during atrial tachycardia. Methods and Results: A total of 14 goats was studied. Five goats were subjected to 3:1 AV pacing (A-paced group, atrial rate 240 beats/min, ventricular rate 80 beats/min). Nine goats were subjected to rapid 1:1 AV pacing (AV-paced group, atrial and ventricular rates 240 beats/min). During 4 weeks, right atrial (RA) and left ventricular (LV) diameters were measured during sinus rhythm. Atrial effective refractory periods (AERP) and inducibility of AF were assessed at three basic cycle lengths (BCL). After 4 weeks of rapid AV pacing, RA and LV diameters had increased to 151% and 113% of baseline, whereas after rapid atrial pacing alone, these parameters were unchanged. Right AERP (157 ± 10 msec vs 144 ± 16 msec at baseline with BCL of 400 msec in the A-paced and AV-paced group, respectively) initially decreased in both groups, reaching minimum values within 1 week. Subsequently, AERP partially recovered in AV-paced goats, whereas AERP remained short in A-paced goats (79 ± 7 msec vs 102 ± 12 msec after 4 weeks; P 〈 0.05). Left AERP demonstrated a similar time course. Inducibility of AF increased in both groups and reached a maximum during the first week in both groups, being 20% and 48% in the A-paced and AV-paced group, respectively. Conclusion: Nature and time course of atrial electrical remodeling and dilation during atrial tachycardia are influenced by concurrent high ventricular rate and consequent development of CHF.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1540-8167.2001.01404.x
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  • 3
    Electronic Resource
    Electronic Resource
    Rapid Pacing Results in Changes in Atrial But Not in Ventricular Refractoriness (2002)
    Oxford, UK : Blackwell Futura Publishing, Inc.
    Pacing and clinical electrophysiology 25 (2002), S. 0 
    Details
    ISSN: 1540-8159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: SCHOONDERWOERD, B.A., et al.: Rapid Pacing Results in Changes in Atrial But Not in Ventricular Refractoriness. It is well known that atrial tachycardia causes atrial electrical remodeling, characterized by shortening of atrial effective refractory periods (AERPs) and loss of physiological adaptation of AERP to rate. However, the nature and time course of changes in ventricular effective refractory periods (VERP) caused by rapid rates are to be established. After being instrumented with epicardial electrodes on both atria and both ventricles nine goats were subjected to 1 week of rapid AV pacing with a rate of 240 beats/min and an AV delay of 100 ms. Pacing was only interrupted for measurement of left and right AERPs and VERPs at three basic cycle lengths (BCL) of 400 ms, 300 ms, and 200 ms during sinus rhythm in the conscious animal. Left and right AERPs decreased at all BCLs, reaching minimum values after 3 days (right AERP at BCL of 400 ms, 96 ± 16 ms after 3 days vs 144 ± 16 ms at baseline, P 〈 0.05). In contrast, both left and right VERPs did not change at any BCL. This study demonstrates a difference between the atria and ventricles with respect to tachycardia induced changes in refractoriness.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-9592.2002.00287.x
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  • 4
    Electronic Resource
    Electronic Resource
    Prediction of Lesion Size Through Monitoring the 0°C Isothermic Period Following Transcatheter Cryoablation (1998)
    Springer
    Journal of interventional cardiac electrophysiology 2 (1998), S. 383-389 
    Details
    ISSN: 1572-8595
    Keywords: catheter ablation ; cryotherapy ; isothermic period ; arrhythmia ; lesion size
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract A prototype steerable 8.5F bipolar catheter fitted with a feedback thermocouple was tested in 7 anaesthetized pigs (30 kg) guided by the electrocardiogram in order to modify the AV nodal and His-Purkinje system conductive properties. Thermal energy was delivered by a pressurized N 2O tank (〉650 psi) via a cardiac cryo unit (Spembly, Hampshire, UK) into the catheter wherein gas expands resulting in a tip temperature as low as −70 ± 2°C within 10 seconds. Cryoablation under fluoroscopic and electrocardiographic guidance was applied at distinct sites in both ventricles for 60 or 120 seconds. After a follow-up period of 6 weeks, the ablation lesions found were well demarcated with small margins of hypertrophy of myocardial cells. With respect to lesion volume variability (8–207 mm 3) and geometry, a relationship between the 0°C isothermic period and cryolesion volume was found. Results of an in vitro model corroborated this relationship. Therefore, an isothermic period probably can predict the lesion size and its geometry in terms of lesion depth. This potential therapeutic mode of transcatheter cryoablation deserves further investigation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009777024597
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  • 5
    Electronic Resource
    Electronic Resource
    The effects of oral pretreatment with zofenopril, an angiotensin-converting enzyme inhibitor, on early reperfusion and subsequent electrophysiologic stability in the pig (1990)
    Springer
    Cardiovascular drugs and therapy 4 (1990), S. 695-703 
    Details
    ISSN: 1573-7241
    Keywords: converting enzyme inhibition ; myocardial infarction ; reperfusion ; pig ; signal averaging ; zofenopril
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The effects of oral zofenopril pretreatment were investigated in a chronic closed-chest pig model of ischemia and reperfusion. Pigs (25–35 kg) were pretreated orally with zofenopril (15 mg/day) on the 2 days prior to ischemia, which was evoked by the inflation of a catheter balloon in the left anterior descending coronary artery over 45 minutes. The catheter was then removed and the myocardium was reperfused. After 2 weeks, infarct properties were assessed by signal averaging of the body surface electrocardiogram and the inducibility of malignant ventricular tachyarrhythmias was tested with a programmed electrical stimulation protocol. A significant increase in the pressure-rate product (43±11%, mean±SEM), indicating the oxygen demand of the heart, was prevented by zofenopril (19±8%, p〈0.05). Zofenopril reduced the peak efflux of adrenaline (1302±213 vs. 3201±760 pg/ml; p〈0.05), noradrenaline (402±54 vs. 902±282 pg/ml; p〈0.05), and of the adenosine catabolites inosine and hypoxanthine (56±4 vs. 78±9, pg/ml; p〈0.05) in the coronary venous effluent. The efflux of the cytoplasmatic enzyme creatine phosphokinase was not significantly reduced after zofenopril (p=0.08). No difference in plasma renin levels between the groups were found. After 2 weeks, late potentials were found only in the surviving animals from the untreated group, i.e., the voltage vector magnitude was more reduced, and a prolongation of the QRS duration and of the terminal low-amplitude part of the high-frequency QRS were found. Moreover, zofenopril had caused a significant reduction of the inducibility of sustained ventricular tachyarrhythmias. These findings support the view that catecholamine and purine efflux, and an adverse increase in the oxygen demand during early reperfusion are reduced by zofenopril pretreatment, leading to a higher electrophysiologic stability of the subsequently developed infarct after 2 weeks.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01856557
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