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At least 91 records · Page 5Linked to original sources
PubMed1981

Electrophysiologic effects of ouabain in patients with preexcitation and circus movement tachycardia.

Effects of intravenous ouabain were evaluated in 19 patients with an anomalous conduction pathway (14 with manifest and 5 with concealed preexcitation (utilizing intracardiac stimulation and recording. Anterograde conduction through the anomalous pathway was present in all 14 patients with manifest preexcitation at a maximal atrial paced rate of 140 to 250 beats/min (mean +/- standard error of the mean 214 +/- 7.2) before and at 150 to 240 beats/min (mean 206 +/- 7.1) after ouabain (difference not significant [NS]). The anterograde effective refractory period of the anomalous pathway, measured at an equivalent atrial paced rate in 10 patients, was 250 to 450 ms (mean 309 +/- 19.7) before and 260 to 450 ms (mean 300 +/- 17.2) after ouabain (NS). Retrograde conduction through the anomalous pathway was possible at maximal ventricular paced rates (17 patients) of 160 to 250 beats/min (mean 222 +/- 6.6) before and 190 to 250 beats/min (mean 221 +/- 4.4) after ouabain (NS). Sustained atrioventricular (A-V) reentrant paroxysmal supraventricular tachycardia was inducible in all 19 patients before and in 17 patients (89 percent) after ouabain (tachycardia could not be induced in two patients because of increased A-V nodal refractoriness). The mean cycle length of tachycardia in the 17 patients was 320 +/- 6.7 ms before and 340 +/- 8.1 ms after ouabain (p < 0.01). In conclusion, ouabain has no significant effect on either anterograde or retrograde anomalous pathway refractoriness. Although ouabain slightly increases the cycle length of tachycardia, it does not interfere with induction of tachycardia in most patients with preexcitation. Oral cardiac glycosides alone would appear to be of limited value in patients with preexcitation and recurrent supraventricular tachycardia.

Adolescent↗
PubMed1994

Circus movement atrial flutter in the canine sterile pericarditis model. Relation of characteristics of the surface electrocardiogram and conduction properties of the reentrant pathway.

OBJECTIVES: This study was designed to elucidate the basis for the electrocardiographic (ECG) appearance of atrial flutter in the canine sterile pericarditis model. BACKGROUND: During atrial flutter, the surface ECG may show typical F waves or isolated P waves of any polarity. METHODS: Electrocardiographic leads II, III and aVF and epicardial atrial activation maps constructed from 127 simultaneously recorded bipolar electrograms were compared in 20 dogs with sterile pericarditis and inducible atrial flutter. RESULTS: In 10 dogs with F wave atrial flutter, single loop reentry occurred around combined functional/anatomic obstacles that included one or both caval veins and a vertically oriented arc of functional conduction block. In 10 dogs with P wave atrial flutter, a merely functional (n = 4) or combined (n = 6) obstacle involving any atrial vessel and more vertically (n = 5) or more horizontally (n = 5) oriented arcs of block was present. The isoelectric interval between P waves corresponded to the conduction time within the slow zone of the reentrant circuit (96 +/- 27 vs. 100 +/- 24 ms, mean +/- SD). Slow conduction accounted for 65 +/- 8% of the cycle length in P wave atrial flutter, but for only 29 +/- 7% in F wave atrial flutter (p < 0.05). Slow conduction was usually associated with activation of fewer than five epicardial electrodes per 10-ms isochronal interval, reflecting only a small amount of atrial tissue. The polarity of P or F waves was determined by the direction of the major wave front activating the most electrodes per 10-ms isochronal interval, irrespective of whether the right or the left atrium was activated. CONCLUSIONS: The F waves result from reentrant activation at a relatively constant speed around a vertically oriented functional/anatomic obstacle involving one or both caval veins. The P waves occur when the circuit contains a marked area of slow conduction.

Animals↗
PubMed2004

The molecular complexity of glucocorticoid actions in inflammation - a four-ring circus.

Glucocorticoids have been the mainstay of anti-inflammatory therapy for the past 50 years despite the significant risks associated with their long-term use. Recent research into the molecular mechanisms of action of these compounds can be aggregated into two major themes: first, those that focus on the involvement of the glucocorticoid receptor in regulating the transcription of pro-inflammatory genes; and second, studies that seek to identify alternative pathways of glucocorticoid action either via the induction of anti-inflammatory mediators or through rapid non-genomic mechanisms. Understanding the temporal-spatial patterns of these multiple mechanisms on relevant cell types will be key to explaining the profound effects that these four-ring steroids exert on the inflammatory process.

Animals↗
PubMed1997

A circus flea.

Explore the source record for details and available documents.

Animals↗
PubMed2001

The circus in the pituitary.

Actions and Interactions at the Pituitary was a Satellite Meeting of the 34th Congress of the International Union of Physiological Sciences held in Christchurch, New Zealand from 24-25 August 2001.

Animals↗