Electrophysiological studies with prenalterol.

Electrophysiological studies with prenalterol in 19 patients (6 women, 13 men, 5 with sinus node disease, 4 with AV node disease, 7 with double node disease, 2 with conduction disturbance below His bundle, 1 normal) showed that sinus node function (heart rate, sinus node recovery time) is uniformly improved by this beta-stimulator. Also AV conduction is significantly and uniformly improved (shortening of AH interval and of the functional refractory period of AV conduction). There is no or little influence on intra-atrial conduction and on conduction below the His bundle. However, spontaneous depolarisation in His-Purkinje fibers--as tested in patients with complete AV block and ventricular demand pacemaker--is increased through beta-stimulation with prenalterol as reflected by shorter escape intervals and higher frequency escape rhythm. Prenalterol may be of clinical use in patients with cardiomyopathies who developed bradycardia under digitalisation or patients with severe bradyarrhythmia either with or without digitalis. It might also be useful in rare emergency situations, when complete pacemaker failure develops.

Partial atrial standstill in sick sinus syndrome; intraatrial and AV nodal block with short PR interval.

Standstill and inexcitability (quiescence) of the high right atrium could be demonstrated in a patient with sinus node dysfunction and bradycardia--tachycardia syndrome. The onset of P wave in surface electrocardiogram did not represent the beginning of atrial excitation but followed 130 msec the high right atrial and 50 msec the low right atrial deflection, leading thereby to a short PR interval which gave misinformation on the atrioventricular conduction. A pacemaker implant with right ventricular stimulation freed the patient of his previous complaints. 4 wk after the implantation the demand unit was inhibited for 5 h by external stimulation. Continuous ECG monitoring, esophageal ECG recording and fluoroscopic study could not reveal any atrial activity. The conditions for atrial pacemaker implantation are discussed.

Disappearing His deflection. Electrophysiological evidence for conduction defect within the His bundle.

A change in the voltage and character of the His bundle deflection following premature atrial stimuli was observed and analysed in 5 of 95 patients having intracardiac conduction studies because of AV conduction disturbances. Of these 5 patients, 3 had spontaneous block within the His bundle, 2 of them showing block in other segments of the conduction system. With increasing prematurity of programmed atrial stimuli, there was a progressive decrease in the voltage of the His deflection, followed by a split His deflection, and finally disappearance of the His deflection. The voltage of the His deflection was also reduced in sinus beats following spontaneous His bundle premature beats. Similarly, during atrial stimulation at increasing rates, the His deflection decreased in voltage, split, and finally disappeared, but when Wenckebach periods appeared the His deflection reappeared in the first paced beat after the dropped beat. The preceding H-H interval was the only electrophysiological variable consistently related to the changes in the His deflection. These changes in His deflection can be explained electrophysiologically as the result of a conduction disturbance within the His bundle. The clinical significance of the phenomenon is discussed. The occurrence of this phenomenon during a conduction study makes it difficult or even impossible to localise the AV block precisely.

Hemodynamics at rest and during exercise in 222 patients with coronary heart disease before and after aorto-coronary bypass surgery.

In 222 patients with coronary heart disease hemodynamics at rest and during exercise were measured before and after aortocoronary bypass surgery. A total of 552 grafts were constructed, i.e. an average of 2.47 grafts per patient. Only 10.8% of the patients had a 1-vessel-disease, 59.2% had a 3-vessel-disease. 10.8% of the patients were provided with one graft, 49.7% got 3 or 4 grafts. In 92.8% of the patients the r. desc. ant. was significantly stenosed, and in 94.2% this vessel has been provided with a graft. Preoperatively only 7 patients had no angina pectoris during exercise (bicycle ergometer in supine position, each load lasting 6 min), postoperatively 154 patients have been completely free of angina pectoris. The preoperative angina pectoris-free exercise tolerance was 27.4 +/- 27.4 W (means +/- SD), postoperatively it was 76.5 +/- 33.8 W. The largest increase of exercise tolerance was observed in patients with a 3-vessel-disease (208%). Preoperatively only 10.1% had normal values of pulmonary wedge pressure and cardiac output at rest and during exercise, postooperatively 51.5%. The postoperative normalization of hemodynamics depends on the number of vessels involved (1-vessel-disease 86%, 3-vessel-disease 39.8% normalization) and on the status of the left ventricle (without a previous transmural myocardial infarction 68.4%; with a previous myocardial infarction 41.0%). The effects of revascularization on myocardial ischemia can be evaluated by measurements of pulmonary wedge pressure and cardiac output at rest and during exercise.

Cell contacts in human islets of Langerhans.

The freeze-fracturing technique was applied to fresh human islets of Langerhans. With this technique, the inside of cellular membranes was revealed, and specific membrane differentiations, hitherto unknown, were observed in the plasma membrane of the endocrine cells. The specific membrane differentiations represent two types of intercellular junctions, namely the tight junction, which determines a closure of the extracellular space and the gap junction which allows molecules and ions to diffuse from one cell to another (sharing the gap junction) without leaking in the extracellular space (intercellular coupling). The presence of such junctions may be important for the secretory behavior of the cells within the islet.