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Béla Merkely

Publications and source records attributed to Béla Merkely.

24 records · Page 2Linked to original sources
PubMed2002

Expressed monophasic action potential alternans before the onset of ventricular arrhythmias induced by intracoronary bolus administration of endothelin-1 in dogs.

We showed previously a direct arrhythmogenic effect of the intracoronary infusion of endothelin-1 (ET-1). We aimed to examine the electrophysiological effects of intracoronary bolus administration of ET-1 using monophasic action potential (MAP) recordings. Eight mongrel dogs received boli of ET-1 (1 and 2 nmol) into the left anterior descending coronary artery. These intracoronary ET-1 boli rapidly caused a marked decrease in coronary blood flow (1 nmol, 78+/-7%; 2 nmol, 89+/-7%). Ischaemic changes of MAP morphology, a decrease in upstroke velocity (baseline, 1.78+/-0.2 V/s; 1 nmol, 0.95+/-0.18 V/s; 2 nmol, 0.45+/-0.21 V/s; P<0.01) and a decrease in MAP duration at 90% repolarization (MAPD(90)) [1 nmol, from 191+/-3 to 176+/-5 ms (P<0.05); 2 nmol, from 212+/-4 to 180+/-8 ms (P<0.05)] occurred after ET-1 bolus administration. However, at 7-10 min after the 1 nmol bolus, a significant increase in MAPD(90) was observed (10 min, in the left ventricular anterior epicardial region: from 191+/-3 to 206+/-6 ms; P<0.05). The incidence of ventricular arrhythmias was as follows: after the 1 nmol ET-1 bolus: ventricular tachycardia, 3/8 animals; ventricular fibrillation, 1/8; after the 2 nmol ET-1 bolus: ventricular tachycardia, 5/7; ventricular fibrillation, 5/7. MAP alternans was present in each animal (1 nmol, 18.2+/-5.8%; 2 nmol, 10.8+/-2.5%). Thus electrophysiological and coronary blood flow changes indicate the predominance of an ischaemic arrhythmogenic effect of the bolus administration of ET-1 (shortening of action potential duration; appearance of MAP alternans), whereas the observed delayed prolongation of MAPD(90) suggests a direct arrhythmogenic effect of ET-1. The expressed MAP alternans could have a pathogenic role in the onset of ventricular arrhythmias induced by an intracoronary bolus of ET-1.

Action Potentials↗
PubMed2002

The ET(A) receptor antagonist LU 135252 has no electrophysiological or anti-arrhythmic effects during myocardial ischaemia/reperfusion in dogs.

The anti-arrhythmic effects of ET(A) receptor antagonists during myocardial ischaemia and reperfusion remain controversial. Moreover, the electrophysiological mechanism has not yet been identified. The aim of this study was to investigate the potential anti-arrhythmic and electrophysiological effects of the ET(A) receptor antagonist LU 135252 (LU) during myocardial ischaemia and reperfusion in a canine model. A bolus of LU (1 mg/kg; n=10) or saline (control; n=10) was injected into the left anterior descending coronary artery before ligation of this vessel for 30 min, which was followed by a 90-min reperfusion period. LU bolus administration (0.5 mg/kg) was repeated every 30 min. There were no differences in mean arterial blood pressure or coronary blood flow between the two groups. The determined left ventricular ischaemic mass was 25.5+/-1.8% and 27.8+/-2.2% of the total left ventricular mass in the control and LU groups respectively. The total incidence of ventricular fibrillation during ischaemia and reperfusion was 40% in the control and 50% in the LU group (not significantly different). The incidence of non-sustained and sustained ventricular tachycardias during ischaemia, reperfusion and over the whole period (ischaemia plus reperfusion) in the control group was 50%, 50% and 70% respectively, and that in the LU group was 80%, 70% and 100% respectively (no significant differences between groups). The number of ventricular premature beats was not decreased by LU during either ischaemia or reperfusion [median (25th-75th percentile): ischaemia, 20 (13-37) and 56 (32-130) for LU and control groups respectively; reperfusion, 15 (2-21) and 39 (7-74) respectively; ischaemia+reperfusion, 16 (4-35) and 43 (10-82) respectively; no significant differences between groups]. During ischaemia, the monophasic action potential duration at 90% repolarization (MAPD(90)) decreased significantly, while during reperfusion a significant prolongation of MAPD(90) was observed in the left anterior descending region that was similar in the two groups. In conclusion, LU did not affect repolarization changes and did not have anti-arrhythmic effects during either ischaemia or reperfusion in this model.

Action Potentials↗
PubMed2002

Effects of implantable cardioverter defibrillator implantation and shock application on serum endothelin-1 and big-endothelin levels.

The incidence of ventricular tachyarrhythmias in the early post-operative period following implantable cardioverter-defibrillator (ICD) implantation is relatively high compared with that in control periods. Since endothelin-1 (ET-1) has been proven to be an endogenous arrhythmogenic substance, we investigated the changes in serum ET-1 and big-ET levels in patients undergoing ICD implantation. Serum concentrations of ET-1 and big-ET were measured in 14 patients with various heart diseases before the operation, as well as 1 min and 1 h after the last shock therapy. Big-ET levels and the sum of ET-1 and big-ET levels were unchanged immediately after the operation, but had increased significantly by 1 h after implantation (before, 1.57+/-0.61 pmol/l; 1 min, 1.86+/-0.87 pmol/l; 1 h, 4.29+/-1.65 pmol/l for big-ET; before, 3.44+/-1.07 pmol/l; 1 min, 3.79+/-1.29 pmol/l; 1 h, 6.36+/-2.03 pmol/l for big-ET+ET-1). There was a significant correlation between left ventricular ejection fraction and big-ET level measured 1 h after the last shock delivery (r=-0.542, P<0.05). We conclude that the increased big-ET level observed 1 h after the last induction and shock therapy of ventricular fibrillation might have a pathophysiological role in the increased incidence of post-operative spontaneous ventricular arrhythmias.

Aged↗
PubMed2002

Permanent left atrial and left ventricular single-lead DDD pacing with a coronary sinus electrode.

This report describes a patient with drug refractory severe chronic congestive heart failure, first-degree AV block, and wide QRS complexes of 175-ms duration with left bundle branch block who was successfully treated by a left-sided dual chamber pacemaker system using a single-lead coronary sinus electrode. Left atrial and ventricular signal amplitudes, left atrial and ventricular pacing thresholds were 2.5 mV, 13 mV, 1.8 V and 0.7 V (0.5 ms), respectively. Using DDD pacing with an optimal 120-ms AV delay the QRS duration decreased to 150 ms and the mitral filling pattern improved. Three months after implantation the patient's functional status improved from NYHA Class III-IV to Class II.

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