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Biomedical subjects

K H Kuck

Publications and source records attributed to K H Kuck.

At least 127 records · Page 7Linked to original sources
PubMed1990

Recanalization of chronic, totally occluded coronary arteries by new angioplasty systems.

The benefit and safety of new angioplasty equipment as compared with the conventional guidewire approach was evaluated in 154 consecutive patients. with chronic, totally occluded coronary arteries. The protocol followed a stepwise design: first, conventional guidewires and low-profile balloons were used, followed by "balloon-on-the-wire" systems (Probe, Ace) or by a shaft-enforced, tip-deflecting catheter (Omniflex). In 97 patients with occlusions of 2 to 12 weeks' duration, recanalization was achieved in 51 patients (53%) with the conventional approach and in 29 patients with the new devices (balloon-on-the-wire [n = 5], Omniflex [n = 24]), thereby raising the success rate to 82%. In 57 occlusions of greater than 12 weeks' duration, the recanalization attempt was successful in 58%, mediated in 16 patients (28%) by the Omniflex catheter and in 5 patients by balloon-on-the-wire systems. There were no life-threatening complications and only 1 (0.6%) emergency bypass operation was necessary. New angioplasty devices are therefore of considerable value in the attempt to improve the results of coronary angioplasty in chronic total occlusions.

Angioplasty, Balloon, Coronary↗
PubMed1990

Syncope in hypertrophic cardiomyopathy: multivariate analysis of prognostic determinants.

Twenty-nine consecutive patients with symptomatic hypertrophic cardiomyopathy and a mean age of 44.8 +/- 12.2 years (range 21 to 63) underwent complex invasive and noninvasive testing to identify a risk profile for syncope. Clinical, morphologic, electrophysiologic and hemodynamic variables at rest and at a symptom-limited pacing rate were analyzed for a significant association with syncope. Exact stepwise logistic regression analysis identified three variables as significant independent predictors of syncope in hypertrophic cardiomyopathy: 1) age less than 30 years (beta = 4.803; p = 0.0007); 2) left ventricular end-diastolic volume index less than 60 ml/m2 (beta = 3.302; p = 0.006); and 3) nonsustained ventricular tachycardia on 72 h ambulatory electrocardiographic monitoring (beta = 2.5909; p = 0.03). The combined occurrence of all three variables had a sensitivity and specificity of 100% in identifying eight patients with syncopal events. Thus, the risk for syncope in hypertrophic cardiomyopathy is high in young patients with the combination of low left ventricular filling volume and episodes of nonsustained ventricular tachycardia. This finding might also explain the mechanism of syncope in hypertrophic cardiomyopathy as low input-low output failure induced by a sudden increase in heart rate in the presence of a low filling volume.

Adult↗
PubMed1990

Stability of pacing threshold, impedance, and R wave amplitude at rest and during exercise.

The pacing threshold of the human heart may be altered by physiological factors such as physical exercise. These changes may influence the individual programming of a pacemaker, since pacemakers can be programmed at pulse amplitudes of 2.5 volts and less. We investigated 22 patients with a multiprogrammable ventricular demand pacemaker 3 months after implantation; 16 patients had received a steroid-eluting lead and six patients had an Elgiloy lead. Parameters measured at rest and immediately after exercise were: Voltage threshold at pulse durations between 0.05 and 0.6 ms, impedance, R wave amplitude and energy consumption for the pacing threshold at 0.5 ms pulse duration. All patients performed a symptom limited supine bicycle exercise test. None of the investigated parameters showed a significant difference between rest and exercise, neither for the steroid eluting lead nor for the Elgiloy lead. The data suggest that the individual programming of a pacemaker adapted to the measurements at rest is also reliable and safe during exercise.

Aged↗
PubMed1990

Chronic ventricular electrograms: do steroid-eluting leads differ from conventional leads?

The aim of steroid-eluting leads is to reduce chronic pacing thresholds. Whether steroid-eluting leads also modify acute and chronic R wave amplitudes as well as R wave sensing of the pulse generator was investigated in 31 patients with a unipolar ventricular pacemaker. Four different leads were implanted: Two steroid-eluting leads with different electrode surface areas (8 mm2 and 5.8 mm2) and two conventional leads (Target Tip, Elgiloy lead). At implantation filtered R wave amplitudes, peak-to-peak values, and slew rates were measured by a pacing system analyzer. One year after implantation R wave amplitudes were directly determined from intracardiac electrograms and compared to the peak-to-peak data at implantation. Additionally, R wave inhibition was evaluated at a sensitivity setting of 5 mV. There were no differences among the four leads in respect to any of the parameters studied at implantation. At follow-up, no differences in R wave amplitudes were found leading to an appropriate sensing in all leads. Steroid-eluting leads did not differ from conventional leads and a smaller electrode surface area of 5.8 mm2 had no influence on ventricular electrogram. Together with a pacemaker with an input impedance of 37 kohms R wave sensing was a correct setting of 5 mV.

Aged↗
PubMed1990

Sites of conduction block in accessory atrioventricular pathways. Basis for concealed accessory pathways.

Catheter recordings of accessory pathway (AP) activation were used to identify the site of antegrade and retrograde AP conduction block in 126 consecutive patients undergoing electrophysiological testing. Activation was recorded from 89 of 121 left free-wall and posteroseptal pathways (left APs) and from 12 of 24 right free-wall, midseptal, and anteroseptal pathways (right APs). The recorded APs were further subdivided into those exhibiting consistent antegrade conduction during sinus rhythm (overt APs: 50 left APs, eight right APs), those exhibiting intermittent antegrade conduction (intermittent APs: six left APs, two right APs), and those exhibiting only retrograde conduction (concealed APs: 33 left APs, two right APs). The sites of block were recorded during decremental atrial and ventricular stimulation. The sites of both antegrade and retrograde block were determined in 40 of 50 overt left APs and six of eight overt right APs. Antegrade and retrograde block occurred at or near the AP-ventricular (AP-V) interface in 37 of 40 overt left APs and two of six overt right APs and at the atrial-AP (A-AP) interface in one of 40 overt left APs and four of six overt right APs. In three of three overt left APs with no retrograde conduction, retrograde block occurred at or near the AP-V interface. The site of antegrade and retrograde block differed in only two of 58 overt pathways. There was no difference between overt APs limited at the A-AP or the AP-V interface in the shortest atrial or ventricular pacing cycle length maintaining 1:1 antegrade or retrograde AP conduction, respectively. Both antegrade and retrograde block occurred near the AP-V interface in four of six intermittent left APs and zero of two intermittent right APs and near the A-AP interface in two of six intermittent left APs and one of two intermittent right APs. The sites of both antegrade and retrograde block were determined in 28 of 33 concealed left APs, and both occurred at or near the AP-V interface in 26 and A-AP interface in two APs. In two of two concealed right APs, antegrade block occurred at the AP-V interface. These findings suggest that both antegrade and retrograde conduction are limited by factors operating near the AP-V interface in overt left APs and at the A-AP or AP-V interface in overt right APs. Factors limiting antegrade conduction in concealed APs appear to be located almost always near the AP-V interface.

Atrioventricular Node↗
PubMed1990

[Risk of syncope in hypertrophic cardiomyopathy: a multivariate analysis of prognostic variables].

Twenty-nine consecutive patients with symptomatic hypertrophic cardiomyopathy and a mean age of 44.8 +/- 12.2 years (range 21 to 63 years) underwent complex invasive and noninvasive testing in an attempt to identify a risk profile for syncope. Clinical, morphologic and electrophysiologic as well as functional parameters at rest and at symptom-limited pacing rate were analyzed for significant association with syncope. Exact stepwise logistic regression analysis identified three variables as significant independent predictors of syncope in hypertrophic cardiomyopathy: 1) age less than 30 years (beta = 4.803; p = 0.0007); 2) left ventricular end-diastolic volume index less than 60 ml/m2 (beta = 3.302; p = 0.006) and 3) non-sustained ventricular tachycardia on 72 h ambulatory ECG monitoring (beta = 2.5909; p = 0.03). The combined occurrence of all three variables had a 100% sensitivity and specificity to identify eight patients with syncopal events. Thus, the risk for syncope in hypertrophic cardiomyopathy is high in young patients with the combination of low left ventricular filling volume and episodes of non-sustained ventricular tachycardia. This finding might also explain the mechanism of syncope in hypertrophic cardiomyopathy as low-input-low-output failure induced by a sudden increase in heart rate in presence of a low filling volume.

Adult↗
PubMed1990

[Prerequisites for pacemaker electrodes for individual programming of a low stimulation impulse (comparison of an Elgiloy and a steroid-dependent pacemaker electrode)].

The individual programming of cardiac pacemakers to pulse amplitudes of 2.5 volts and less reduces unnecessary energy consumption by the pacing impulse. In order not to impair the safety margin, electrodes must reveal a low chronic pacing threshold associated with a small standard deviation. For 3 months after implantation we investigated these conditions in 10 patients with a steroid-eluting lead and in 10 patients with a conventional elgiloy lead. During the study period patients with a steroid-eluting lead had a significantly lower pacing threshold. Twelve weeks after implantation all steroid-patients had 0.8 volts pacing threshold at 0.5 ms pulse width. In contrast to the conventional lead the steroid-eluting lead had a significantly lower impedance. Since voltage enters squared into the energy consumption formula, patients with a steroid-eluting lead needed significantly less energy for an effective stimulation of the myocardium 4 and 12 weeks after implantation. R-wave amplitude was not different in both groups. Our investigation demonstrates that immediately after implantation all patients with a steroid-eluting lead can be programmed at 2.5 volts pulse voltage or individually even lower. The saved energy results either in an extended pulse generator longevity or allows the implantation of a smaller pulse generator with a reduced battery capacity.

Aged↗
PubMed1989

[Arrhythmia as an indicator for reperfusion following acute myocardial infarct?].

For the purposes of the European double blind and randomized study 27 patients with acute myocardial infarction underwent thrombolysis with rt-PA (60 mg over 90 minutes i.v.) or placebo. To evaluate whether arrhythmias, especially ventricular arrhythmias indicate coronary reperfusion after thrombolysis a 24 hour Holter monitoring was performed from the beginning of the rt-PA or placebo infusion. Typical reperfusion arrhythmias were thought to be idioventricular rhythms (rate less than 110/min), ventricular tachycardia (rate greater than 110/min) or bradycardic rhythm disturbances (rate less than 50/min). The effect of thrombolysis on reperfusion of the infarct related artery was evaluated 90 minutes after the infusion by coronary angiography. After 90 minutes of rt-PA or placebo infusion in 16/16 patients treated with rt-PA and 2/11 patients, who received placebo, was the infarct artery patent. 16/18 patients with a patent artery presented a total of 105 arrhythmic events. 47% of the arrhythmias obviously due to reperfusion were classified as idioventricular rhythms. In contrast only 3/9 patients with an occluded infarct artery presented 25 arrhythmic events. The time of occurrence was not different during the running rt-PA infusion compared to placebo. The following interval up to 24 hours showed no difference in incidence and type of the arrhythmias. No relationship was found between reperfusion arrhythmias and salvage of myocardium during 90 minutes of rt-PA or placebo infusion.

Arrhythmias, Cardiac↗
PubMed1989

Diprafenone for treatment of Wolff-Parkinson-White syndrome.

The effect of intravenous (1.5 to 2.0 mg/kg body weight) and oral (300 to 375 mg/d) diprafenone was studied in 15 patients with the Wolff-Parkinson-White syndrome and symptomatic supraventricular tachycardia. Intravenous application of diprafenone significantly increased atrioventricular nodal conduction time as well as the effective refractory periods of the right ventricle and the accessory pathway in both the antegrade and retrograde directions. Antegrade conduction block in the accessory pathway occurred in two patients after the dose was increased to 2.0 mg/kg body weight. Intravenous diprafenone suppressed the inducibility of supraventricular tachycardia in two patients, but the tachycardia cycle length was significantly increased in all other patients. Fourteen patients were treated with oral diprafenone, and 11 were asymptomatic during a 17-month follow-up, two of these after the dose had been increased to 375 mg/d. Oral therapy had to be withdrawn in two patients because of adverse gastrointestinal side effects and in one because of recurring bronchospasm.

Administration, Oral↗
PubMed1989

Alcohol-induced coagulation necrosis in cardiac tissue: a new concept in the surgical management of recurrent ventricular arrhythmias.

Post myocardial infarction recurrent ventricular arrhythmias are usually coupled with depressed left ventricular function. We have until recently employed the most widely used surgical techniques such as endocardial resection, cryosurgery and isolation. After these methods had failed in a patient with an extensive septal focus, it finally became possible to effectively ablate the arrhythmogenic area by injection of 10 ml 95% alcohol subendocardially. The following experimental studies were carried out to investigate the effect of direct injection of alcohol on the myocardicytes. 95% alcohol, injected into the apex of the left ventricle of Wistar rats weighing between 150 and 200 g caused extensive coagulation necrosis 5 minutes after injection, as was revealed by histological examination. The site of injection showed marked scar formation after 6 months. On the basis of these findings, 4 more patients were treated successfully with alcohol, which was directly injected subendocardially without endocardial resection using a long needle. The advantage of this procedure is that resection can be avoided, particularly in critical areas such as the septum and regions around papillary muscles.

Animals↗
PubMed1989

Ablation of a left-sided free-wall accessory pathway by percutaneous catheter application of radiofrequency current in a patient with the Wolff-Parkinson-White syndrome.

A case is presented of a 20-year-old woman with a history of three episodes of syncope within the last 4 years, which was caused by a rapid ventricular response to atrial fibrillation via a left-sided posterior accessory pathway. A variety of antiarrhythmic agents had failed to control the arrhythmia. Using a novel dual catheter approach, with one catheter in the coronary sinus and an adjacent catheter in the left ventricle close to the mitral annulus, accessory pathway conduction was successfully interrupted by two radio-frequency current applications between the tip electrodes of the two catheters. During follow-up, 12-lead electrocardiograms have been normal and the patient has been asymptomatic.

Adult↗
PubMed1989

Pleomorphic ventricular tachycardia: demonstration of conduction reversal within the reentry circuit.

A case is presented of a patient with incessant ventricular tachycardia of left bundle branch block morphology. Endocardial mapping revealed the site of earliest activation during tachycardia to be the proximal right ventricular septum. Pacing at this site elicited the clinical tachycardia, whereas pacing at the proximal left ventricular septum induced a right bundle branch block morphology identical to that of a previously recorded spontaneous ventricular tachycardia. Electrophysiological evidence is given that both types of tachycardia originate from a single reentry circuit located in the proximal ventricular septum in which the reentrant wavefront may travel either orthodromically (during spontaneous tachycardia and right ventricular pacing) or antidromically (during left ventricular pacing).

Animals↗
PubMed1989

[Coronary artery spasm as a rare cause of sudden heart arrest].

After successful resuscitation only few patients present without any findings indicative of the causes of their cardiac arrest. We report on a 39-year-old woman who had normal clinical, electrocardiographic, and angiographic findings after she was successfully resuscitated. In contrast to other patients without apparent organic heart disease she had three cardiac arrests within 10 months; each episode was preceded by an ascending epigastric pain. During an attack with epigastric pain a long-term ECG recording documented an increasing ST-segment elevation followed by rapid, non-sustained ventricular tachycardia. Intravenous ergonovine induced a spasm of the right coronary artery with a subtotal vessel occlusion and an ST-elevation in lead III. After medication with a calcium antagonist no coronary vasospasm was demonstrated. For 11 months the patient has been without any complaints.

Coronary Angiography↗
PubMed1988

Encainide versus flecainide for chronic atrial and junctional ectopic tachycardia.

For treatment of chronic atrial and junctional ectopic tachycardia, standard antiarrhythmic therapy has been shown to be ineffective in most patients. Both the intravenous efficacy and the oral efficacy of 2 class IC antiarrhythmic drugs, encainide and flecainide, were studied in 16 patients with atrial ectopic tachycardia and in 3 patients with junctional ectopic tachycardia, using exercise testing, 24-hour long-term electrocardiography and programmed electrical stimulation. All patients had been previously treated unsuccessfully with several antiarrhythmic drugs. In 5 patients, tachycardia was persistent; in the remaining patients, it occurred intermittently for more than 12 hours/day. Intravenous encainide, in doses ranging from 0.3 to 2.0 mg/kg body weight, was given to 5 patients with atrial ectopic tachycardia, and it terminated atrial ectopic tachycardia in all patients. Intravenous flecainide was given to 9 patients, and it terminated atrial tachycardia in 4 and slowed the tachycardia rate in 2. It terminated junctional tachycardia in 2 patients and slowed tachycardia rate in 1. During a follow-up period of 10 +/- 5 months, oral encainide, in dosages between 150 and 225 mg/day, completely suppressed atrial ectopic activity in 4 patients. In the remaining patient, encainide reduced the number of tachycardia episodes markedly but had to be withdrawn because of intolerable side effects. During a 12 +/- 11-month (median 6) follow-up, oral flecainide at dosages between 200 and 300 mg/day, completely suppressed ectopic activity in 7 patients and improved symptoms in 5. Only 1 patient failed to respond to oral flecainide. The results of this study indicate that both encainide and flecainide are effective in the treatment of chronic ectopic atrial and junctional tachycardia.

Administration, Oral↗
PubMed1988

[Catheter-induced modulation of the electric conductivity of the atrioventricular node by high-frequency current].

A radio-frequency current was delivered via a catheter to the atrioventricular (AV) node in 13 patients with supraventricular arrhythmias (maximal heart rate 215/min). In nine patients with atrial fibrillation, three with AV nodal re-entry tachycardia and one with AV re-entry tachycardia, AV node conduction time was prolonged from 95 +/- 43 ms to 168 +/- 72 ms. In three patients the radio-frequency current had no lasting effect, necessitating AV node ablation with a direct-current shock. During a mean observation period of five months, all ten patients in whom the radio-frequency current had been successfully applied remained free of symptoms without any anti-arrhythmia treatment. There were no complications during or after treatment.

Adult↗
PubMed1988

Programmed electrical stimulation in hypertrophic cardiomyopathy. Results in patients with and without cardiac arrest or syncope.

Programmed electrical stimulation was performed in 54 consecutive patients with hypertrophic cardiomyopathy. There were 11 'symptomatic' patients: three had a history of cardiac arrest due to ventricular tachyarrhythmias (group A), and eight had a history of syncope of unknown origin (group B); 43 patients were 'asymptomatic', i.e. they had no documented or suspected symptomatic ventricular arrhythmias (group C). There were no differences among the groups with respect to electrocardiographic, echocardiographic or hemodynamic data. Ventricular arrhythmias were induced by atrial and right and left ventricular stimulation with a maximum of two extrastimuli in 18 patients. Induced arrhythmias were repetitive ventricular response in six patients, nonsustained ventricular tachycardia in four, sustained ventricular tachycardia in five, and ventricular fibrillation in three patients. With one exception, ventricular tachycardia was always rapid (cycle lengths ranged from 180 to 250 ms); it was polymorphic in six patients and monomorphic in three. Atrial stimulation induced rapid monomorphic ventricular tachycardia in one group A patient. The type and incidence of induced ventricular arrhythmias did not differ among the three groups. It is concluded that programmed electrical stimulation induces the same type of ventricular arrhythmia (rapid polymorphic ventricular tachycardia or ventricular fibrillation) in 'symptomatic' and 'asymptomatic' patients with hypertrophic cardiomyopathy, the incidence in the latter group being 19%. Induction by atrial stimulation of a rapid ventricular tachycardia may be a specific finding to identify patients with hypertrophic cardiomyopathy at risk for exercise-induced ventricular fibrillation.

Adult↗
PubMed1988

Modification of a left-sided accessory atrioventricular pathway by radiofrequency current using a bipolar epicardial-endocardial electrode configuration.

Transcatheter ablation of a left posterolateral free wall accessory atrioventricular pathway using radiofrequency current and a bipolar epicardial-endocardial electrode configuration was attempted in a 19-year-old woman. The patient had suffered from recurrent syncope due to atrial fibrillation with rapid conduction to the ventricles. Following applications of radiofrequency current between one electrode in the coronary sinus and another in the left ventricle placed high against the mitral annulus, the anterograde effective refractory period was increased from less than 205 ms to a lasting value of 460 ms. Radiofrequency application could be performed without general anaesthesia and caused no side-effects.

Adult↗