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Biomedical subjects

B Merkely

Publications and source records attributed to B Merkely.

41 records · Page 3Linked to original sources
PubMed1995

Ventricular tachycardias induced by intracoronary administration of endothelin-1 in dogs.

In 12 anesthetized, open-chest mongrel dogs, endothelin-1 (ET-1) was infused into the left anterior descending coronary artery through an indwelling catheter at a dose of 30 pmol.min-1 for 30 min (n = 8). In four dogs the ET-1 dose was increased to 60 pmol/min for 10 min. Programmed electrical stimulation was used for electrophysiologic studies. Coronary blood flow was reduced by 32% on average without any ischemic ECG signs. QT time (186 +/- 3 ms vs. 218 +/- 6, p < 0.05, and 225 +/- 9, p < 0.05, p < 0.05). Ventricular irritability increased in all cases; ventricular extrasystoles, and nonsustained and sustained tachycardias occurred and, in 11 cases, ventricular fibrillation terminated the experiments. In two dogs, early afterdepolarization was recorded. Therefore, ET-1 is capable of inducing fatal ventricular arrythmias at least partly independent of its vasoconstrictor effect. QT prolongation appears to have a pathophysiologic role in this arrythmogenic effect.

Action Potentials↗
PubMed1993

[Iatrogenic sinus node disease and iatrogenic AV block].

The appearance of long lasting bradycardia due to damage of the sinus node (iatrogen sick sinus syndrome; or the atrioventricular conduction system, iatrogen AV block) is not a rare event after open heart surgery. In the course of 5093 heart operations the development of iatrogen sick sinus syndrome was observed in 234 patients (4.6%) and iatrogen AV block in 91 cases (1.8%). The incidence rate of iatrogen sick sinus syndrome or iatrogen AV block was quite divergent depending mostly on the type of operation. Comparing the data of our earlier (1977-1982) and later (1983-1991) cardiac surgical interventions, the prevalence of iatrogen sinus node disease and iatrogen AV block seems to decrease, mainly due to the progress in techniques of cardiac surgery. With the appearance of iatrogen sick sinus syndrome or AV block, urgent temporary pacing is indicated to prevent the deleterious hemodynamic effect of bradycardia. In the cases of persistent iatrogen sick sinus syndrome and iatrogen AV block, permanent pacemaker implantation is needed. It is remarkable that although the incidence rate of iatrogen sick sinus syndrome is greater than that of iatrogen AV block, in iatrogen sick sinus syndrome the regression is quite frequent, while in iatrogen AV block the 2nd or 3rd degree AV block is usually permanent. We performed pacemaker implantation in 56 cases of iatrogen sick sinus syndrome (24%) and in 57 patients of iatrogen AV block (63%). With pacemaker therapy the outcome of iatrogen sick sinus syndrome and iatrogen AV block is very favourable.

Bradycardia↗
PubMed1985

Effects of intense "stretching"-flexibility training on the mechanical profile of the knee extensors and on the range of motion of the hip joint.

The sample for the study involved 12 volunteer male, active but not specially trained secondary school students. They averaged 15.33 years with a mean height of 168.20 cm, and a mean mass of 55.08 kg. Changes, if any, in the mechanical properties (MVC, half-relaxation time, fast isometric contraction, concentric contraction of the knee extensors) and flexibility of the hip joints were studied. The subjects executed passive, purely slow stretching as well as range-of-motion flexibility exercises for the knee extensors and the hip joints for 7 weeks three times a week. Pre- and post-measurements for flexibility and stride frequency on the spot showed significant improvement as did half-relaxation time, fast isometric force development, and speed of concentric contractions when low loads were to be overcome. In addition to studies in which improvements reported were attributed to and related to myoelectrical, reflex, and connective tissue changes, in the present study it was concluded that stretching exercises influence intrinsic muscle mechanical character along with a simultaneous improvement in range of motion of the joints exercised.

Adolescent↗