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Epicardial Electrodes (epicardial + electrode)

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Medical Sciences	100%

Selected Abstracts

The anti-diabetic drug miglitol is protective against anginal ischaemia through a mechanism independent of regional myocardial blood flow in the dog

CLINICAL AND EXPERIMENTAL PHARMACOLOGY AND PHYSIOLOGY, Issue 10 2005
Yoshihiro Uno
SUMMARY 1.,In the present study, we attempted to clarify whether the antidiabetic drug miglitol, an ,-glucosidase inhibitor, has a protective effect against anginal ischaemia. We had reported previously that miglitol reduces myocardial infarct size through inhibition of glycogenolysis during ischaemia in rabbits. However, the effect of miglitol on anginal ischaemia remains unknown. 2.,In open-chest beagle dogs with a severely stenosed left anterior descending coronary artery, an epicardial electrode was attached to the surface of the risk area of the left ventricle and a microdialysis probe was implanted into the myocardium to measure ST segment changes and interstitial lactate accumulation. The first episode of anginal ischaemia was induced by atrial pacing and phenylephrine infusion (50,100 µg/min) for 10 min. The second episode of anginal ischaemia was induced 210 min after the first episode. Miglitol (10 mg/kg, i.v.) was administered to the miglitol group (n = 10) 30 min before the second episode of anginal ischaemia, whereas saline was administered to the control group (n = 10). Regional myocardial blood flow was measured using coloured microspheres. 3.,There was no significant difference in regional myocardial blood flow in the risk and non-risk areas between the first and second episodes of anginal ischaemia and between the miglitol and control groups. During the first and second episodes of anginal ischaemia, the ST segment was decreased to a similar extent in the control group. Although ST segment depression during the first episode of anginal ischaemia was similar in both groups, ST segment depression during the second episode of anginal ischaemia was significantly attenuated in the miglitol-treated group compared with the control group (1.3 ± 0.4 vs 2.2 ± 0.4 mV, respectively). Miglitol significantly attenuated myocardial interstitial lactate accumulation in the risk area. 4.,In conclusion, in the present study miglitol improved ST segment depression and attenuated the accumulation of myocardial interstitial lactate during anginal ischaemia without altering regional myocardial blood flow. Miglitol has an anti-anginal ischaemia effect via a mechanism that is independent of regional myocardial blood flow. [source]

Frequency Analysis of Atrial Electrograms Identifies Conduction Pathways from the Left to the Right Atrium During Atrial Fibrillation,Studies in Two Canine Models

JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 6 2009
KYUNGMOO RYU Ph.D.
Studies of atrial fibrillation (AF) have demonstrated that a stable rhythm of very short cycle length in the left atrium (LA) can cause fibrillatory conduction in the rest of the atria. We tested the hypothesis that fast Fourier transform (FFT) analysis of atrial electrograms (AEGs) during this AF will rapidly and reliably identify LA-to-right atrium (RA) conduction pathway(s) generated by the driver. Methods and Results: During induced atrial tachyarrhythmias in the canine sterile pericarditis and rapid ventricular pacing-induced congestive heart failure models, 380,404 AEGs were recorded simultaneously from epicardial electrodes on both atria. FFT analysis of AEGs during AF demonstrated a dominant frequency peak in the LA (driver), and multiple frequency peaks in parts of the LA and the most of the RA. Conduction pathways from the LA driver to the RA varied from study-to-study. They were identified by the presence of multiple frequency peaks with one of the frequency peaks at the same frequency as the driver, and traveled (1) inferior to the inferior vena cava (IVC); (2) between the superior vena cava and the right superior pulmonary vein (RSPV); (3) between the RSPV and the right inferior pulmonary vein (RIPV); (4) between the RIPV and the IVC; and (5) via Bachmann's bundle. Conduction pathways identified by FFT analysis corresponded to the conduction pathways found in classical sequence of activation mapping. Computation time for FFT analysis for each AF episode took less than 5 minutes. Conclusion: FFT analysis allowed rapid and reliable detection of the LA-to-RA conduction pathways in AF generated by a stable and rapid LA driver. [source]

Prednisone Prevents Inducible Atrial Flutter in the Canine Sterile Pericarditis Model

JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 1 2008
ROBERT N. GOLDSTEIN M.D.
Background: Atrial fibrillation (AF) and atrial flutter (AFL) are common following cardiac surgery and are associated with significant morbidity. We tested the hypothesis that suppression of the inflammatory response with steroids would significantly modify the inducibility of postoperative AF/AFL in the canine sterile pericarditis model. Methods: Twenty-three dogs were studied daily from creation of pericarditis to the fourth postoperative day: 11 dogs were treated with oral prednisone (PRED) starting 2 days preoperatively until the end of the study; 12 dogs were controls (CON). EP testing was performed daily using epicardial electrodes placed at initial surgery. High-resolution (404 sites) epicardial mapping was performed during the terminal study. Baseline and daily CRP levels were obtained in all dogs. Results: Sustained AFL was absent in PRED (0%) versus CON dogs (91%; P < 0.001); AF induced in the early postoperative course in PRED dogs was of very short CL (mean 66 ms). Tissue inflammation was significantly attenuated in PRED dogs. Thresholds were lower in PRED versus CON dogs, significantly so on postoperative day (POD) 3. There was a trend toward lower ERPs in the PRED group at all CLs. CRP levels were markedly reduced in PRED versus CON dogs (peak CRP 78 ± 7 mg/L vs 231 ± 21 mg/L, P < 0.001), and returned to baseline in PRED dogs by POD 4, correlating with a virtual absence of sustained arrhythmia. During open chest mapping studies on POD 4, PRED dogs showed only nonsustained AF/AFL. Conclusions: Prednisone eliminated postoperative AFL, affected all EP parameters studied, and attenuated the inflammatory response associated with pericarditis. [source]

Fractionation of Electrograms and Linking of Activation During Pharmacologic Cardioversion of Persistent Atrial Fibrillation in the Goat

JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 5 2004
ZHAOLIANG SHAN M.D.
Introduction: During atrial fibrillation (AF), there is fractionation of extracellular potentials due to head-to-tail interaction and slow conduction of fibrillation waves. We hypothesized that slowing of the rate of AF by infusion of a Class I drug would increase the degree of organization of AF. Methods and Results: Seven goats were instrumented with 83 epicardial electrodes on the left atrium, left atrial appendage, Bachmann's bundle, right atrium, and right atrial appendage. AF was induced and maintained by an automatic atrial fibrillator. After AF had persisted for 4 weeks, the Class IC drug cibenzoline was infused at a rate of 0.1 mg/kg/min. AF cycle length (AFCL), the percentage of fractionated potentials, conduction velocity (CV), and direction of propagation of the fibrillation waves were measured during baseline, after AFCL was increased by 20, 40, 60, and 80 ms, and shortly before cardioversion. Infusion of cibenzoline increased the mean of the median AFCLs from 96 ± 6 ms to 207 ± 43 ms (P < 0.0001). The temporal variation in AFCL in different parts of the atria was 8% to 20% during control and, with the exception of Bachmann's bundle, was not significantly reduced during cibenzoline infusion. CV decreased from 76 ± 14 ms to 52 ± 9 cm/s (P < 0.01). Cibenzoline increased the percentage of single potentials from 81%± 4% to 91%± 4% (P < 0.01) and decreased the incidence of double potentials from 14%± 4% to 7 ± 5% (P < 0.01) and multiple potentials from 5%±% to 1%± 2% (P < 0.001). Whereas during control, linking (consecutive waves propagating in the same direction) during seven or more beats occurred in 9%± 15% of the cycles, after cibenzoline the degree of linking had increased to 40%± 33% (P < 0.05). During the last two beats before cardioversion, there was a sudden prolongation in AFCL from 209 ± 37 ms to 284 ± 92 ms (P < 0.01) and a strong reduction in fractionated potentials (from 22%± 12% to 6%± 5%, P < 0.05). Conclusion: The Class IC drug cibenzoline causes a decrease in fractionation of fibrillation electrograms and an increase in the degree of linking during AF. This supports the observation that Class I drugs widen the excitable gap during AF. (J Cardiovasc Electrophysiol, Vol. 15, pp. 572-580, May 2004) [source]