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Biomedical subjects

A Pelleg

Publications and source records attributed to A Pelleg.

At least 73 records · Page 4Linked to original sources
PubMed1985

Effects of dantrolene sodium on occlusion and reperfusion arrhythmias in the canine heart.

The effects of dantrolene sodium on occlusion and reperfusion ventricular arrhythmias (VA) were studied in a canine model. Transient ischemia was induced by a 10 min occlusion period of the left anterior descending coronary artery in 27 control dogs and 32 dogs pretreated with dantrolene sodium (2.5 mg/kg). In the control group, 14 (52%) dogs experienced VA during occlusion. Five of these had ventricular fibrillation, 3 of which were fatal. Eight of 24 control dogs which reached reperfusion experienced ventricular fibrillation during the first 30 sec of reperfusion. Dantrolene sodium did not lower the frequency of VA during occlusion 22/32 (69%). Moreover, the incidence of fatal ventricular fibrillation during occlusion was significantly (p less than 0.025) higher in the drug treated-group (12/32; 37.5%) than in the control group (3/27; 11%). Dantrolene sodium also significantly reduced the time that lasted from the commencement of occlusion to the appearance of ventricular fibrillation (240 +/- 1 sec versus 166 +/- 9 seconds, control and drug group, respectively p less than 0.05) without significantly altering either heart rate or blood pressure (169 +/- 4 b.p.m., and 170 +/- b.p.m.; 101 +/- 10 mmHg and 104 +/- 9 mmHg, before and after dantrolene sodium, respectively). These results indicate that dantrolene sodium might have an arrhythmogenic effect in the ischemic canine heart.

Animals↗
PubMed1984

Electrophysiologic effects of adenosine triphosphate and adenosine on the mammalian heart: clinical and experimental aspects.

Adenosine triphosphate (ATP) and adenosine have strong negative chronotropic and dromotropic effects on the mammalian heart. The sensitivity of the sinus node and the atrioventricular node to ATP and adenosine manifests pronounced variability among species. For more than three decades, ATP has been used routinely in Europe in the acute therapy of paroxysmal supraventricular tachycardia. Preliminary clinical trials with adenosine in the United States suggest that this compound may have a similar therapeutic value. The exact mechanisms of action of ATP and adenosine on the mammalian heart are still not fully known. However, the vast clinical experience indicates that ATP, and probably also adenosine, can be safely and repetitively used in the acute therapy of paroxysmal supraventricular tachycardia.

Adenosine↗
PubMed1984

Non-invasive recording of His bundle activity in patients with Wolff-Parkinson-White syndrome.

Ten patients with Wolff-Parkinson-White syndrome underwent external His bundle recording using an advanced signal-averaging technique. Surface ECG waveforms were recorded and digitized at 1.28 kHz (10 bit resolution) and then averaged with a CDC-6600 computer. A cross-correlation function, operating in the frequency domain (using the Fast Fourier Transform algorithm) was employed to extract fiducial synchronizing marks for the waveform alignment. Using this technique, reliable His bundle activity could be recorded in nine of ten patients. There was a good correlation between the HQ and HV intervals obtained during external and internal His bundle recordings, respectively, in seven patients who underwent both recordings. Administration of ajmaline enabled to obtain the His bundle activity using a digital filter with low frequency cut-off of 30 Hz as compared to the cut-off of 150 Hz which was necessary during control to reduce the electrical activity of the delta wave. We conclude that using a computerized cross-correlation signal-averaging technique enables the external His bundle recording in patients with WPW syndrome.

Adolescent↗
PubMed1984

Simultaneous AV nodal reentrant and ventricular tachycardias.

Simultaneous AV nodal reentrant and ventricular tachycardias were observed during the course of an electrophysiological study in a 51-year-old patient who suffered from recurrent attacks of sustained ventricular tachycardia. Occurrence of simultaneous tachycardias was facilitated by the fact that both tachycardias had a similar cycle length. Ventricular tachycardia was most probably initiated by AV nodal tachycardia previously induced by atrial extrastimulation following the administration of atropine.

Anti-Arrhythmia Agents↗
PubMed1983

Ultrastructural localization of glucose-6-phosphatase in renal glomerulus of the adult dog.

The ultrastructural distribution of glucose-6-phosphatase activity was investigated in renal glomeruli of adult dogs by electron-microscopic cytochemistry. The enzymatic activity was found mainly in the parietal epithelial cells of Bowman's capsule. Weaker activity occurred in visceral epithelial cells. No activity was found in either the endothelial or the mesangial cells. Strong activity of glucose-6-phosphatase was commonly found in the nuclear envelope, and occasionally in the rough endoplasmic reticulum. The distribution of the enzyme and its functional significance are discussed in relation to previously reported data.

Animals↗
PubMed1983

An advanced non-invasive technique for the recording of His bundle potential in man.

A new method for external recording of the His bundle electrical activity is described. Four hundred standard ECG waveforms were recorded and digitized at 1.28 kHz (8 bit resolution) and averaged with the aid of a CDC 6600 computer to reduce the random noise. A cross correlation function, which operates in the frequency domain using the Fast Fourier Transform algorithm, was employed to extract fiducial synchronizing marks for the waveforms alignment (triggering). Waveforms were filtered with a digital bandpass filter (30 Hz and 250 Hz low and high cut off frequencies respectively). The activity of the His bundle which was thus obtained was present on an isoelectric line, with signal amplitude of 4 to 7 microV. A strong correlation (r = 0.95, n = 10) was found between the HV intervals and the HQ intervals obtained from intracardiac electrograms and the new technique. It was concluded that the new method is convenient, reliable and can be successfully applied for the management of patients with various problems in their cardiac conducting system.

Adolescent↗
PubMed1983

Determination of the left bundle branch refractoriness by distal His bundle pacing in patients with left bundle branch block.

Electrophysiological studies were carried out in two patients with an idiopathic left bundle branch block. Consistent distal His bundle pacing resulted in the normalization of the QRS complex in both patients. Extrastimulation during basic distal His pacing at several cycle lengths was carried out successfully. Using this technique, the refractory periods of the left bundle branches were measured and found to be within the normal range. In addition, they decreased with the shortening of the basic cycle length. These results demonstrated the possibility of determining the refractoriness of the left bundle branch by His bundle pacing in patients with left bundle branch block. Hypotheses are postulated about the presumed location of the lesion responsible for the left bundle branch block.

Adult↗
PubMed1981

Conduction disturbances between a pacemaker electrode and the myocardium in right ventricular infarction.

Rate dependent first degree block, which was followed by a complete block, between a pacemaker electrode and the ventricular myocardium, was observed in a patient with inferior myocardial infarction. These conduction disturbances which occurred during pacing at the postero-basal wall of the right ventricle and not during pacing at the apex, suggested that the posterior part of the right ventricle was damaged. This hypothesis was supported by hemodynamic findings which indicated a right ventricular infarction.

Aged↗
PubMed1981

Serial electrophysiological studies in a young patient with recurrent ventricular fibrillation.

A 28-year-old male with recurrent episodes of ventricular fibrillation, which were initiated by very early ventricular premature depolarizations with a normal QT interval, was subjected to three consecutive electrophysiological studies. During the first study, which was carried out to test the efficacy of amiodarone treatment, no ventricular arrhythmias could be induced. While on amiodarone therapy, the patient experienced another syncopal episode and therefore a second electrophysiological study was done. In that study, ventricular fibrillation was induced by ventricular stimulation. During the third study, which was carried out in order to evaluate the effect of the addition of quinidine to the on-going amiodarone therapy, no more than three repetitive ventricular responses could be induced. The patient has been asymptomatic since the third study (fifteen months) with combined therapy of amiodarone and quinidine. The significance of the ability to induce ventricular fibrillation during an electrophysiological study is discussed as well as the value of such studies in determining the long-term efficacy of antiarrhythmic drug therapy.

Adult↗
PubMed1980

Overdrive suppression of automaticity in cultured chick myocardial cells.

Overdrive suppression in automatic cells and postdrive hyperpolarization in quiescent cells were examined in cultured embryonic chick heart cells. Cells were enzymatically separated from 3-day-old whole hearts and from 16-day-old atria and ventricles. The dispersed cells were allowed to reaggregate into small spheres (aneural) and maintained in culture for 1--4 wk. Quiescent reaggregates (all ventricular reaggregates and some of the atrial) demonstrated postdrive transient hyperpolarization of up to 5 mV. The spontaneously beating reaggregates (some of the atrial and all of the 3-day-old hearts) demonstrated overdrive suppression of automaticity. The faster the predrive spontaneous firing rate, the shorter was the overdrive suppression period. Prolongation of the drive period increased the duration of the overdrive suppression. The time courses of recovery from both overdrive suppression and postdrive hyperpolarization were similar. Atropine (10(-5) M) did not affect the phenomena. Ouabain (10(-6) M) reduced the postdrive hyperpolarization and shortened the duration of overdrive suppression. It was concluded that overdrive suppression and postdrive hyperpolarization a) occur in cultured chick ventricular and atrail cells; b) occur in early embryonic stages of development; c) occur independently of cholinergic receptors; d) are dependent on stimulation of an elecrogenic Na-K pump.

Animals↗
PubMed1980

ECG indicators of accessory pathway involvement in paroxysmal supraventricular tachycardia.

Paroxysmal supraventricular tachycardia results from circular movement of the depolarization wave, with or without the involvement of an accessory pathway. Two ECG signs have been proposed as indicators of such accessory pathway involvement in the retrograde limb of the circular movement: a negative retrograde atrial activity in lead I, and a paradoxical tachycardia slowdown with the onset of a functional bundle-branch block ipsilateral to the accessory pathway. Electrophysiological studies were carried out on 17 patients--12 with manifest and five with concealed preexcitation--and the data were analyzed with respect to the two above-mentioned signs. In the 14 patients with a left accessory pathway, there was a negative P wave in lead I during tachycardia. Six of them had functional left bundle-branch block; in four of these six, the tachycardia slowed down with the onset of the block and in one, the rate of the tachycardia did not change. In the sixth patient, the left bundle-branch block pattern appeared in one atrial echo beat and its effect on the rate of tachycardia could not be determined. In 6 of the 14 patients with a left accessory pathway, there was no change in the rate of tachycardia with the onset of a right bundle-branch block. It was concluded that the two ECG signs are reliable indicators of the involvement of an accessory pathway in paroxysmal supraventricular tachycardia.

Adult↗
PubMed1979

Electrophysiological recordings from spontaneously contracting reaggregates of cultured smooth muscle cells from guinea pig vas deferens.

Smooth muscle cells were enzymatically dispersed from vasa deferentia of adult male guinea pigs (250-400 g). These cells reassociated in vitro to form monolayers and small spherical reaggregates (0.05-0.3 mm in Diam). Within 48 h of being placed in culture, cells in both types of preparation began to contract spontaneously. The contractions were rhythmic and slow. Cells in the monolayers stopped contracting after approximately 1 wk in vitro, but the reaggregates continued to contract spontaneously for at least 3 wk. Electron microscopy of the reaggregates revealed the presence of thick and thin myofilaments. Overshooting action potentials were recorded in many of the cells penetrated (primarily in reaggregates), and were accompanied by visible contractions of the aggregate or monolayer. Quiescent cells could often be excited by intracellularly applied depolarizing and hyperpolarizing (anodal-break) current pulses. The resting potentials had a mean value of -58 +/- 2 mV. The action potentials were usually preceded by a spontaneous depolarization. The action potentials had slow rates of rise (1--4 V/s) which were unaffected by tetrodotoxin (TTX, 1 microgram/ml), a known blocker of fast Na+ -channels. Verapamil (1 microgram/ml) blocked the action potentials. The mean value of input resistance was 6.9 +/- 0.5 M omega (n = 12). These electrophysiological properties are similar to those of intact adult vas deferens smooth muscle cells. Thus, the cultured adult vas deferens smooth muscle cells retain their functional properties in vitro even after long periods.

Action Potentials↗