Biomedical subjects

D Euler

Publications and source records attributed to D Euler.

7 recordsLinked to original sources

PubMed1997

Autonomic influences in atrial ischemia: vagally mediated atrial conduction improvement.

To investigate the effects of autonomic nerve activation on electrophysiological properties of ischemic atrial myocardium, experiments were performed in 10 open chest adult dogs anesthetized with xylazine and alpha-chloralose. Ischemia was created in the right atrial free wall by ligation of one or more branches of the right coronary artery. Bipolar electrograms were recorded from multiple sites in the ischemic and non-ischemic zones. The atria were paced at 400 ms and 180 ms to assess conduction properties. One hour after ligation, delayed activation, electrogram fractionation, and electrogram alternans were observed in the ischemic zone. All local conduction abnormalities were heart rate dependent in that they were only observed at a pacing cycle length of 180 ms. The average duration of ischemic zone electrograms was significantly prolonged from 17.7+/-1.6 ms to 26.4+/-1.6 ms (P<0.001). Right and left vagal stimulation significantly shortened the electrogram duration in the ischemic zone from 26.4+/-1.6 ms to 19.7+/-1.1 ms (P<0.01) and 20.0+/-1.1 ms (P<0.01), respectively. Ischemia-induced electrogram alternans was eliminated completely. During right and left stellate stimulation, electrogram duration was not altered and alternans was still present. In conclusion, vagal stimulation in this canine model improves local conduction in ischemic myocardium in the right atrium. This effect may be mediated by a reversal of the ischemia-induced membrane depolarization and a shortening of refractoriness in the atrium during vagal activation.

Animals↗

PubMed1995

Assessment of outcome of bifurcation lesions and non-bifurcation lesions treated in the CAVEAT trial. CAVEAT investigator group.

Registry data suggests that bifurcation lesions are associated with reduced success during percutaneous revascularization. We studied 1012 CAVEAT patients to compare procedural outcomes in patients with and without bifurcation lesions whose target vessel was treated with either atherectomy or angioplasty. Bifurcation lesions have increased angiographic complexity and interventions on them are associated with lower acute procedural success rates compared to non-bifurcation lesions. Subgroup analysis suggests that atherectomy treatment of bifurcation lesions improves acute procedural success rates and lowers restenosis rates compared to angioplasty treatment of bifurcation lesions but atherectomy of bifurcation lesions is associated with higher acute complication rates than angioplasty of bifurcation lesions.

Adult↗

PubMed1993

Regional changes in blood flow, extracellular potassium and conduction during myocardial ischemia and reperfusion.

OBJECTIVES: We postulated that ventricular arrhythmias may arise from the heterogeneous washout of ischemic metabolites. Our objective was to investigate the distribution of extracellular potassium concentration ([K+]o) during myocardial ischemia and reperfusion and to correlate this distribution with regional differences in myocardial blood flow. BACKGROUND: Our previous study showed that reperfusion after a brief period of ischemia resulted in heterogeneous reflow of the ischemic myocardium. METHODS: The changes in regional myocardial blood flow, midmyocardial [K+]o and electrogram duration were quantitated in 14 dogs undergoing 20 min of left anterior descending coronary artery occlusion and 1 min of reperfusion. Regional myocardial blood flow was measured by using 15-microns radioactive microspheres in 1- to 1.5-g full thickness myocardial samples. The [K+]o was measured with intramyocardial K(+)-sensitive electrodes. RESULTS: During coronary occlusion, the ischemic zone exhibited a reduction in regional blood flow to 0.13 +/- 0.06 ml/g per min and increases in [K+]o to 9.3 +/- 2.6 mmol/liter and electrogram duration to 131.8 +/- 38.6% of control. Heterogeneous reduction in regional blood flow at various sites in the ischemic zone had fair correlations with variable increases in [K+]o (r = -0.70) and electrogram duration (r = -0.75). During min 1 of reperfusion, regional blood flow ranged from two to more than seven times baseline, resulting in a disorganized spatial distribution of perfusion with islands of high and low blood flows. Associated with the heterogeneous early reperfusion regional myocardial blood flow, [K+]o and electrogram duration changed at different rates toward normal. Whereas correlation between regional blood flow and [K+]o or standardized electrogram duration was fair during ischemia, this correlation was poor during early reperfusion. CONCLUSIONS: Spatial heterogeneity in regional myocardial blood flow during myocardial ischemia and early reperfusion is associated with heterogeneity in [K+]o and electrophysiologic characteristics, which in turn may play an important role in the genesis of arrhythmias arising from the ischemic and reperfused myocardium.

Animals↗

PubMed1981

Detection of delayed ventricular activation on the body surface in dogs.

This study describes a noninvasive method for detecting delayed ventricular activation, caused by ischemia, on the body surface. Signal averaging and a newly developed high-pass digital filter were used. The filter has the property that it does not create an artifact or ring after the QRS complex ends, thereby allowing the detection of microvolt-level potentials that occur immediately after the QRS complex. Eleven dogs were studied before and during acute ischemia induced by coronary artery ligation and latex embolization. The ischemic region was mapped with bipolar electrodes and, after the chest was rapidly closed, signal-averaged recordings were made from the body surface. Repeated cycles of ventricular mapping and signal averaging were performed. In each dog, delayed and fractionated electrograms were recorded directly from the ischemic epicardium that lasted a maximum of 118 +/- 18 ms after QRS onset. The duration of the ventricular electrograms varied with time. Whenever delayed epicardial electrograms were recorded, filtered signal-averaged leads showed microvolt-level potentials early in the S-T segment that were continuous with the QRS complex. The duration of ventricular activation, as measured from the bipolar electrograms and from the filtered signal-averaged leads, correlated well (r = 0.93, P less than 0.001). Because of the absence of filter ringing, low-level potentials could be detected less than 40 ms after the QRS complex ended. This study demonstrates that microvolt-level potentials arising from delayed ventricular activation can be reliably detected on the body surface, even when they occur just after the QRS complex.

Animals↗

PubMed1978

Sinus node dysfunction. An overview with emphasis on autonomic and pharmacologic consideration.

Sinus node dysfunction is a disorder of impulse generation and impulse conduction. Previous works have emphasized that the dysfunction occurs not only within the sinus node but also within the escape pacemaker. Adrenergic and cholinergic mechanisms, as well as pulsations and pressure within the sinus node artery, play an important role in normal sinus node activity. Although perinodal fibers act as a buffer zone for sinoatrial conduction, their role in man is yet to be clarified. During normal sinus node activity, pacemaker shifts from the sinus node to the crista terminalis have been shown to occur. Following sinus node destruction, similar shifts do occur. Clinical methods of determining sinus node function, such as the sinus node recovery time and sinus atrial conduction time, are useful but have limitations. Dynamic electrocardiographic monitoring provides the best clinical method available for detecting sinus node dysfunction. Digitalis appears to improve the parameters of sinus node function by increasing the automaticity of latent atrial pacemakers. The atrial arrhythmia of sinus node dysfunction appears to be related to the characteristics of latent atrial pacemaker and "enhanced" cholinergic tone.

Arrhythmias, Cardiac↗

PubMed1978

Cardiac pacemakers in absence of the SA node: responses to exercise and autonomic blockade.

Surgical excision of the sinoatrial node, verified histologically, is followed by a supraventricular (atrial) rhythm in both resting and exercising dog whether anesthetized or conscious. The ECG is characterized by a definitive P wave and associated atrial electrograms. Waxing and waning in heart rate, generally referred to as sinus arrhythmia continues in the awake animal after complete excision of the SA node. This arrhythmia is responsive to both adrenergic and cholinergic interventions, thus indicating the presence of both sympathetic and parasympathetic regulation of subsidiary atrial pacemaking tissues.

Adrenergic beta-Antagonists↗

PubMed1977

Refractory ventricular arrhythmia: the role of intraoperative electrophysiological study.

Thirty patients with drug refractory ventricular tachycardia (RVT) were studied between 1 week and 5 years after myocardial infarction with coronary agniography and left ventriculography. They were divided into four groups: (1) inoperable, five patients; (2, a) operated, with primary left ventricular failure, five patients; (2, b) operated with primary RVT, not mapped, 15 patients; (2, c) operated, with mapping, five patients. The mortality rate in group 1 was 100%, and in group 2, a it was 80%. In group 2, b, despite aggressive drug therapy and operation, including aneurysmectomy, coronary revascularization, and intra-aortic balloon pumping when appropriate, the mortality rate wad intraoperative mapping in group 2, c. Arrhythmogenic foci were identified and removed in four. There was one operative death (20%) and four patients are alive from 12 to 27 months after operation, three of whom are asymptomatic. Intraoperative epicardial mapping is an important adjunct to surgery for RVT.

Aged↗