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Biomedical subjects

A Waleffe

Publications and source records attributed to A Waleffe.

At least 19 recordsLinked to original sources
PubMed1992

Incidence, pathophysiology and prognosis of exercise-induced sustained ventricular tachycardia associated with healed myocardial infarction.

Of 150 consecutive patients with sustained monomorphic ventricular tachycardia (VT) (n = 116) or ventricular fibrillation (VF) (n = 34) late after acute myocardial infarction, 17 had reproduction of their sustained monomorphic VT during exercise testing. Data from these patients (group I) were compared with data from patients without exercise-induced VT (group II). No statistical difference was found between groups I and II with relation to age, sex, number of vessels with greater than 70% stenosis, left ventricular ejection fraction, number of previous myocardial infarctions, inducibility during programmed stimulation and total mortality during follow-up. In group I, only 1 patient (6%) developed ST depression during exercise compared with 47 patients (35%) in group II (p less than 0.01). After a 34-month mean follow-up, 6 patients in group I (35%) and 18 patients in group II (13%) died suddenly (p = 0.02). It is concluded that sustained monomorphic VT is reproduced during exercise in only 11% of patients with spontaneous late sustained monomorphic VT or VF. Electrocardiographic findings do not support ischemia as a triggering mechanism of exercise-induced sustained monomorphic VT. Patients with exercise-induced sustained monomorphic VT have a high incidence of sudden death.

Coronary Angiography↗
PubMed1992

Usefulness and adequacy of sensor data storage and retrieval for rate response simulation.

The usefulness of sensor data storage for rate response simulation was evaluated using a new dual chamber rate modulated pacemaker sensitive to acceleration forces (Relay 294-03 [Intermedics Inc.]). The pacemaker can store the sensor output during routine exercise and those values can be used to simulate rate profiles for other rate response settings. The predictive value of this feature was evaluated in three studies (mechanical, external pacemaker, and implanted pacemaker). In the first study, the pacemaker was submitted to three runs of eight different mechanical calibrated to-and-fro movements. In the second study, nine external pacemakers were strapped on healthy volunteers who performed three jogging tests. Finally, the predictive value of the simulation was studied in five implanted patients during three successive walking tests. In each study, the pacemaker was submitted three times to the same activity. The responsiveness was successively set to 5, 1, and 10, and the pacemaker outputs were continuously recorded on a Holter monitor. At the end of the first run, rate profile simulations for slopes 1 and 10 were performed; slope 5 rate response was simulated after the second run. A regression analysis was used to establish the correlation between predicted and achieved pacing rates for each study. The coefficients of correlation between predicted and measured pacing rates for the mechanical, external, and clinical studies were 0.999, 0.985, and 0.823, respectively. The corresponding slopes of regression lines were 1.005, 0.971, and 0.935. Calculated rate profile has a high predictive value and could be used to optimize rate responsive settings without serial exercise testings.

Acceleration↗
PubMed1992

Clinical interest of a sensor driven algorithm limiting ventricular pacing rate during supraventricular tachycardia in dual chamber pacing.

UNLABELLED: A sensor driven algorithm limiting ventricular pacing rate during supraventricular tachycardia (SVT) is included in a dual chamber rate modulated pacemaker sensitive to acceleration forces (Relay, 294-03, Intermedics Inc.). According to the intensity of concomitant exercise, the ventricular pacing rate is limited either to the programmed maximum pacing rate (MPR) or to an interim lower limit, called "conditional ventricular tracking limit" (CVTL). The MPR prevails over the CVTL when the sensor calculated pacing rate exceeds the minimal rate by more than 20 beats/min. The purpose of the study is to determine the clinical safety and efficacy of this algorithm in patients with intermittent SVT. METHOD: A Relay was implanted in four patients with a bradycardia/tachycardia syndrome and in four patients with complete atrioventricular block (CAVB). All had episodes of paroxysmal atrial tachycardia. The units were programmed in DDDR: rate responsive parameters were adjusted by simulating the rate response during three levels of exercise to let the MPR override the CVTL only during strenuous exercise. Holter monitors and exercise testings were performed at 3-month follow-up. RESULTS: In seven patients, Holter recordings showed supraventricular arrhythmias at rest with a ventricular pacing rate limited to the CVTL. Appropriate rate increases during exercise testings were also demonstrated. Three devices had to be reprogrammed in DDIR (one patient suffering from nearly permanent atrial flutter and two patients not tolerating the CVTL pacing rate at rest). CONCLUSION: The CVTL algorithm is effective in protecting against high ventricular pacing rates during supraventricular arrhythmias. It allows the selection of the DDDR mode even with a high MPR in patients with intermittent SVT.

Acceleration↗
PubMed1992

In vitro evaluation of a sensor sensitive to acceleration forces included in a new rate modulated pacemaker.

UNLABELLED: The characteristics of the sensor and rate adaptive algorithm included in a new dual chamber rate responsive pacemaker (Relay 294-03, Intermedics, Inc.) were studied by submitting the device to calibrated to-and-fro movements of specific frequencies and peak accelerations by means of a mechanical arm connected to a speed adapter. Atrial pacing rate was continuously recorded on a Holter monitor. The influences of the frequency, the magnitude, and the axis of the acceleration forces as well as the reproducibility of the rate response were evaluated. RESULTS: (1) The sensor was sensitive to frequencies ranging from 0.5 to 7 Hz with a peak sensitivity at 3 Hz; (2) the pacing rate was not affected during movements at frequencies > 6 Hz, commonly presented as nonactivity related signals (car, bus transportation, drilling....); (3) the pacing rate increased as a function of the acceleration magnitude up to 0.5 G (0.3 G for 3 Hz), then remained constant. This level of acceleration usually corresponds to high degrees of activity; (4) rate response was maximum when acceleration was directed in the anteroposterior direction; (5) reproducibility of the rate response was excellent (R2: 0.999; slope of the regression line: 0.999). CONCLUSION: Relay 294-03 is a low frequency signal sensing rate modulated pacemaker using an accelerometer sensitive to motion, mainly in the anteroposterior direction.

Acceleration↗
PubMed1990

Clinical experience with a new catheter for His bundle ablation.

Eleven patients aged 33-66 years were referred for treatment of refractory supraventricular arrhythmias. Each patient had failed to respond to medical treatment. One patient had a paroxysmal atrial flutter with a rapid ventricular response. Six patients had a chronic atrial fibrillation. Two others had a supraventricular tachycardia due to reentry in the atrioventricular (AV) node, and two patients suffered from circus movement tachycardia using a concealed left free wall accessory pathway. A specially built United States Catheter and Instruments (USCI) women Dacron polyurethane electrode catheter (bipolar 8F with an internal lumen, 90 A, 5,000 V, 5.5 omega) was positioned in the His bundle area to record unipolar large atrial and His signals. When the maximal ratio low right atrium/His spike was recorded, the pole was connected to the output of a standard defibrillator. A shock of 200-250 J was delivered through this pole. Ten patients developed complete AV block (CAVB) immediately. After 72 hours, these patients were implanted with a rate-responsive pacemaker. The procedure was without side effects. Nine patients remain in CAVB after 3-17 months; in one case AV conduction resumed but the patient is free of arrhythmia. Another patient needed a second catheter ablation after 1 month.

Adult↗
PubMed1990

Exercise-induced sustained symptomatic ventricular tachycardia: incidence, clinical, angiographic and electrophysiologic characteristics.

Among 112 patients with sustained ventricular tachycardia, 15 were found to have exercise-induced symptomatic ventricular tachycardia. This population was divided into two subgroups: group 1A included five patients with coronary artery disease and group 1B consisted of 10 patients with no structural heart disease. All patients underwent clinical examination, exercise electrocardiography, left ventriculography, coronary angiography (n = 14) and electrophysiologic study. In group 1B, right ventriculography (n = 7), M mode and two-dimensional echocardiography were also obtained. Group 1A patients were compared with a population of 27 patients with coronary artery disease and chronic sustained ventricular tachycardia not related to exercise (group 2). There were no statistically significant differences between group 1A and group 2 in terms of age, sex, incidence of prior myocardial infarction, NYHA functional class, angina pectoris, symptoms during arrhythmia, severity and extent of coronary arterial lesions, ventricular dysfunction and wall motion abnormalities. In group 1B, coronary angiography and right and left ventricular function were normal. During electrophysiologic study, ventricular tachycardia was initiated in four group 1A patients. In group 1B, ventricular tachycardia was initiated in eight patients. In four of these patients ventricular pacing had to be combined with isoproterenol administration. In group 2, ventricular tachycardia was induced in 26/27 patients. From this study we conclude that in patients with coronary artery disease the electrophysiologic substrate of exercise-related sustained ventricular tachycardia does not differ from the substrate of non-exercise-related ventricular tachycardia. Re-entry is the most likely electrophysiologic mechanism. In patients without structural heart disease, the mechanism of the arrhythmia remains speculative.

Angiography↗
PubMed1989

Mechanisms of termination of supraventricular tachycardias by intravenous class III antiarrhythmic agents. A comparison of amiodarone and sotalol.

The effects of amiodarone and sotalol were studied with programmed electrical stimulation of the heart in 19 patients with inducible tachycardia (AV nodal tachycardia: 10 cases, circus movement tachycardia: 9 cases). Amiodarone was administered intravenously at a dose of 300 mg over 2 min and sotalol at a dose of 1.5 mg kg-1 over 10 min. Both i.v. amiodarone and sotalol lengthened the transnodal conduction time, the effective refractory period of the AV node and the AV nodal Wenckebach cycle length. Only sotalol significantly lengthened the effective refractory periods of the right atrium and the right ventricle. Infused intravenously during tachycardia, amiodarone interrupted arrhythmia in five of six patients and sotalol in seven of ten cases. Tachycardia was stopped by blockade of the impulse into the AV node in three amiodarone patients and in five sotalol patients. In the remaining four cases, the weak link of the circuit was the accessory pathway. Thus i.v. sotalol exhibits electrophysiologic effects consistent with both class II and III activity, whereas the effects of i.v. amiodarone are the result of different activities throughout all areas of the cardiac tissue.

Adolescent↗
PubMed1989

Clinical experience with a new activity sensing rate modulated pacemaker using autoprogrammability.

Sensolog 703 is a new single chamber activity sensing rate modulated pacemaker that offers an automatic adjustment of settings called Autoset. Units were implanted in 11 patients (mean age: 67 years) for atrioventricular block (two patients), sinoatrial block (three patients), sick sinus syndrome (four patients), chronotropic incompetence (one patient), and atrial fibrillation with slow ventricular response (one patient). The devices were programmed in VVIR mode using Autoset. The accuracy of the settings was verified by the built-in histogram function. In 6/11 patients, these settings were not satisfactory. Autoset was repeated at 6 months (nine patients) and 10 months (five patients) after implantation. External telemetric recordings during daily life activities, Holter monitoring, bicycle or treadmill stress tests helped in the evaluation of the rate response obtained with the automatic programming. The following problems were encountered: maximum pacing rate for a low level of exercise (four patients), insufficient rate increase (four patients), higher pacing rate during low than during heavy exercises (four patients). A time-consuming (15 to 48 minutes) manual programming was necessary in eight out of nine patients (6 months) and five out of five patients (10 months). In our study, Sensolog 703 algorithm tended to behave as an on/off system; automatic programming was time consuming and only indicative.

Adult↗
PubMed1989

Antegrade conduction over a concealed accessory pathway after His bundle catheter ablation.

The existence of unidirectional retrograde preexcitation or concealed bypass fibers and their role in paroxysmal supraventricular tachycardia have been known for a long time. However, the exact anatomic and physiological nature of this retrograde limb remains unclear. We report here on a patient who had a concealed accessory pathway (AP) with circus movement tachycardia. After His bundle catheter ablation the AP had the property to conduct in the antegrade direction. The absence of antegrade conduction over the AP before ablation is likely due to its decremental properties of conduction and to repetitive retrograde concealed conduction from the normal pathway.

Adult↗
PubMed1986

[Treatment of refractory tachycardias using an implantable cardiac stimulator].

Treatment of tachycardia by permanent cardiac stimulation involves the application of techniques developed in laboratories of clinical cardiac electrophysiology. Clinicians using such treatment must possess detailed knowledge of the physiopathology of arrhythmias and of pacemaker technology, which is essential in the correct selection of patients. We report therapeutic (and not prophylactic) stimulation techniques for treatment of tachycardia, and discuss the possibilities of existing pacemakers and their clinical performance in the light of our own experience and literature data. The results are very promising and suggest that this is a treatment of the future for certain refractory supraventricular tachycardias, and particularly for rapid ventricular tachyarrhythmias. The efficacy and long-term value of this costly treatment in such cases must be evaluated by further studies.

Electric Countershock↗
PubMed1985

Programmable extrastimulus pacing for long-term management of supraventricular and ventricular tachycardias: clinical experience in 16 patients.

Sixteen patients with recurrent, drug-resistant supraventricular (13 patients) or ventricular (3 patients) tachycardia were treated chronically by programmable extrastimulus pacing; either a fully automatic device (Telectronics PASAR 4151: eight patients with supraventricular tachycardia) or a patient--activated device (Medtronic Interactive Tachy System) was used. During a follow-up period of 5 to 30 months, five of the subjects treated with the fully automatic device showed successful results, one had recurrent tachycardia, and two had their units explanted for system-related problems. The patients treated with the externally activated device were, on the whole, very well controlled. This mode of treatment, if applied in well-selected cases, is promising; it seems safe and considerably reduces the number of hospital admissions.

Adult↗
PubMed1985

Effects of intravenous diltiazem administration in patients with inducible tachycardia.

The efficacy of diltiazem was studied with programmed electrical stimulation of the heart in 13 patients with inducible tachycardia (atrioventricular nodal tachycardia: 8 cases; orthodromic circus movement tachycardia involving an accessory pathway: 4 cases; ventricular tachycardia: one case). Diltiazem was administered intravenously at a dose of 0.25 mg kg-1 over 2 min. It lengthened the transnodal conduction time, and the effective and the functional refractory periods of the AV node. The shortest pacing cycle length with 1:1 conduction through the node lengthened both in the anterograde and retrograde directions. Diltiazem did not alter anterograde or retrograde refractoriness of accessory pathways. Infused intravenously during episodes of tachycardia, diltiazem interrupted the arrhythmia in all patients. Tachycardia could still be initiated in 2 patients after drug, but the arrhythmia was not sustained in one case. One patient with preexcitation and atrial fibrillation exhibited an increase in ventricular rate after diltiazem. The shortest RR intervals before and after diltiazem were 240 ms and 180 ms, respectively. Thus, iv diltiazem is an effective antiarrhythmic drug for patients with reciprocal supraventricular tachycardia and for selected patients with ventricular tachycardia.

Adolescent↗
PubMed1985

Electrophysiologic effects, antiarrhythmic activity and pharmacokinetics of cibenzoline studied with programmed stimulation of the heart in patients with supraventricular reentrant tachycardias.

Cibenzoline, an imidazoline derivative is a new antiarrhythmic agent. Its electrophysiological effects and antiarrhythmic properties were studied with programmed electrical stimulation of the heart in 12 patients with recurrent episodes of reentrant supraventricular tachycardia; atrionodal (5 cases), circus movement tachycardia involving an accessory pathway (6 cases), intraatrial reentry (one case). Cibenzoline was infused intravenously at a dose of 1 mg kg-1 to 1.75 mg kg-1 during sustained episodes of tachycardia and over 9 to 15 min. Cibenzoline shortened the sinus cycle length, moderately increased the transnodal conduction time and markedly lengthened the HV interval. The refractory periods of the atrioventricular (A-V) node, the atrium and the ventricle did not change. The effects of cibenzoline on accessory pathways used in the anterograde direction were measurable in 4 cases. Complete blockade of the bypass was seen in every case. In the retrograde direction the refractory period of the bypass could be evaluated; in 5 patients it lengthened systematically. Infused intravenously during epidoses of tachycardia, the drug terminated the rhythm disorder in 9 out of 12 cases. Tachycardia could still be initiated in 8 patients after i.v. cibenzoline (2 out of 5 A-V nodal tachycardias, 6 out of 6 circus movement tachycardias). The distribution of the drug followed a bicompartment pharmacokinetic model. The plasma levels at the end of infusion ranged from 1.34 to 3.19 microgram ml-1. Cibenzoline, primarily has class I antiarrhythmic properties and its well-understood pharmacokinetics should be of help in tailoring the treatment to the individual needs of the patient.

Adolescent↗