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Biomedical subjects

K den Dulk

Publications and source records attributed to K den Dulk.

At least 37 records · Page 2Linked to original sources
PubMed1991

Applicability of the stimulus-T interval for antitachycardia pacing.

UNLABELLED: At the onset of tachycardia, the refractory period (RP) changes together with the tachycardia termination window. We evaluated dogs with total atrioventricular (AV) block to determine if stimulus-T interval (STI) can be used to adjust the coupling interval(s) of an antitachycardia pacemaker in relation to changes in RP. Endocardial STI was recorded continuously together with six surface ECG leads. Steady-state (greater than 2 min) RP was determined for drive cycle lengths (DCL) 400 msec and 900 msec. The test pulse (TP) coupling interval, with DCL 900 msec, was chosen to be equal to the RP of DCL 400 msec. DCL was then changed to 400 msec until TP captured. STI of DCL of beat before capture was gained was measured. DCL was then changed back to 900 msec and the interval determined when capture was lost. TP was then lengthened by 5 msec and the procedure repeated until TP captured immediately upon changing to DCL 400 msec. RESULTS: The difference between RP at onset of pacing at DCL of 400 msec and RP when capture was achieved with the shortest coupling interval was 35-50 (mean 40) msec. This required 35-90 (mean 62) seconds. The correlation coefficient RP to STI was greater than 0.95. CONCLUSIONS: (1) RP changed by as much as 35-50 msec at the onset of an abrupt increase in rate in a 35-90-second period; and (2) STI enables estimation of RP on a beat-to-beat basis. Capture can therefore be predicted from the previous beat and the coupling interval adjusted accordingly in an antitachycardia pacing mode.

Animals↗
PubMed1990

Long-term antitachycardia pacing experience for supraventricular tachycardia.

UNLABELLED: A pacemaker was used to control drug-resistant reentrant supraventricular tachycardia (SVT) in 40 patients. An antitachycardia pacemaker was implanted in 37 for SVT; in one for ventricular tachycardia that could also be used to terminate SVT; in one SVT could be terminated with an activity rate variable pacemaker; and in one a DDD pacemaker was used for prevention and termination of SVT. Twenty patients had AV nodal reentrant tachycardias, eight had tachycardias due to a concealed accessory pathway, eight had a Wolff-Parkinson-White syndrome, three had reentrant atrial tachycardias, and one had atrial flutter. Twenty-two patients were paced from the right atrium, five from the coronary sinus, ten from the right ventricle, and three had a DDD pacemaker. During a total follow-up period of 1,503 (mean 38) months an estimated 16,240 episodes of tachycardia were terminated promptly at home, 58 required several attempts, 57 episodes lasted longer than 30 minutes but did not require medical attention, and 11 required hospital admission. Hospital admission for SVT decreased from one per patient-month (in the 3 months before implantation) to 1 per 137 patient-months after implantation. Additional reentrant tachycardias occurred in 13 patients. Antiarrhythmic drug therapy in combination with a conservative antitachycardia pacing mode was required in four patients paced from the atrium to avoid pacing induced atrial fibrillation. Antiarrhythmic drug therapy was used in 42% of patients to help control SVT. CONCLUSIONS: (1) Drug-resistant SVTs can be safely and effectively managed on the long-term with antitachycardia pacemakers. (2) Rapid termination of SVT improved the quality-of-life significantly by avoiding prolonged episodes of tachycardia and repetitive hospital admissions.

Anti-Arrhythmia Agents↗
PubMed1988

The Activitrax rate responsive pacemaker system.

Bipolar Medtronic Activitrax rate responsive pacemakers were implanted in 31 patients for ventricular (28) or atrial (3) pacing. Mean follow-up was 16 months (range 10 to 26). Twenty pacemakers were implanted after catheter ablation of the His bundle, 7 for sick sinus syndrome. 1 for atrioventricular block and 3 for sick sinus syndrome with atrioventricular block. A rate response value was selected that gave a pacing rate of about 100 pulses/min during walking. Of the 31 patients, all had 24-hour ambulatory electrocardiographic monitoring with diary, 11 walked a 20-minute circuit, including a flight of stairs, and 20 had a treadmill exercise test. In 9 patients the pacing rate could be compared with the underlying sinus rate during exercise and was seen to match it very closely. In 12 patients the pacing rate during car driving was found to be similar to the sinus rate of 5 volunteers under similar conditions (mean minimum and maximum rate was 80 and 99 pulses/min, respectively). No pacing-induced arrhythmias were seen during ambulatory electrocardiographic monitoring. At high pacing rates slightly irregular pacing intervals were sometimes observed, which was due to polarization sensing. Sporadically, 1 pacing interval shortened to the upper rate value, because of a known and now resolved timing anomaly. Neither anomaly was of clinical consequence and the first could be resolved by reprogramming.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1988

Pacemaker syndrome with AAI rate variable pacing: importance of atrioventricular conduction properties, medication, and pacemaker programmability.

A patient who received an AAI Activitrax rate variable pacemaker for treatment of symptomatic sinus bradycardia is described. disopyramide prolonged the anterograde effective refractory period of the fast conducting atrioventricular (AV) nodal pathway to such an extent, that conduction switched to the slow AV nodal pathway at low atrial pacing rates. This gave rise to symptoms of the pacemaker syndrome during moderate exercise because the paced atrial event was conducted with a long, spike to Q interval with occurrence of the paced atrial event just after the preceding QRS complex. A change of medication solved this problem. Programming a bipolar electrode configuration avoided sensing of far-field QRS signals with the associated problems of resetting the basic pacing interval as well as the upper rate interval. AAI rate variable pacing requires careful evaluation of AV conduction properties, AV conduction intervals as well as the influence of medication to be given. The use of multiprogrammable pacemakers with marker channel capability will significantly facilitate the understanding and resolution of anomalous behavior.

Aged↗
PubMed1988

Modern pacemakers: implantable artificial intelligence?

For over twenty years computer programs have been written for applications in cardiology. Approximately one decade ago the first Expert Systems using knowledge on cardiology were built. The use of Expert System shells enabled a breakthrough. Many systems were developed, each covering a small part of cardiology. In the pacing environment Expert Systems can be used to select the optimal pacemaker therapy or to analyze complex pacemaker electrocardiograms. With the help of these artificial intelligence techniques pacemakers can be designed, that behave in an intelligent way. Finally this knowledge representation enables the reproducible simulation of the heart-pacemaker interaction.

Artificial Intelligence↗
PubMed1986

Is there a universal antitachycardia pacing mode?

A pacing mode using automatically increasing number of stimuli with adaptive coupling intervals was evaluated prospectively as a possible universal pacing mode, because a universal mode would save extensive testing and tailoring time. In group 1, which included 7 patients with implanted antitachycardia pacemaker systems, the test mode was compared with the previously tested and tailored mode. In group 2, which included 11 patients undergoing invasive electrophysiologic study, the test mode was compared with the scanning and asynchronous burst mode. There were 4 patients in group 3. The mode was tested prospectively in these 4 patients. Three of these patients were tested after pacemaker implantation (in supine and upright body position and after moderate exercise). The fourth patient had recurring episodes of VT, which were terminated with the test mode via an external lead. Of 209 tachycardias (156 supraventricular tachycardia [SVT] and 53 with VT) studied with the test mode, 1 episode of nonsustained atrial fibrillation was induced from the ventricle and 1 episode of VT was not terminated using the test mode and long coupling intervals. Two episodes of VT in patients with a recent myocardial infarction (MI) required direct-current countershock: due to acceleration in 1 patient and due to VF in 1. All other tachycardias were terminated promptly by the test mode without prior knowledge about successful coupling intervals or number of stimuli. Of the remaining 106 tachycardias studied (69 SVT, 37 VT) the scanning mode failed to terminate 2 episodes of SVT with up to 4 atrial premature beats and induced acceleration of VT in 1 patient with a recent MI.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1986

Detection of insulation failure by gradual reduction in noninvasively measured electrogram amplitudes.

Insulation failure of pacemaker leads may give rise to functional defects such as under- or oversensing, loss of capture or muscle stimulation. An increased incidence of such failures has been reported for the bipolar polyurethane-insulated Medtronic model 6972 pacing lead. It is therefore important to identify techniques that will detect such insulation defects early. A case report is presented in which diminishing electrogram amplitude at follow-up predicted lead failure several months before becoming clinically manifest. This finding suggests that routine measurement of such an electrogram may be a useful tool in predicting impending lead malfunction.

Aged↗
PubMed1986

Merits of various antipacemaker circus movement tachycardia features.

Pacemaker circus movement tachycardia (PCMT) was a significant problem in first generations of DDD pacemakers. Programmability of the atrial refractory period proved to be an effective tool to prevent PCMT except in patients with very long ventriculoatrial (V-A) conduction intervals, because a long atrial refractory period severely limits the maximum tracking rate. In these patients, extension of the atrial refractory period after a VPB, bipolar atrial sensing, adaptation of atrial refractory period to atrial rate, and VPB synchronous atrial stimulation helped limit the incidence of PCMT. Rate smoothing and fallback behavior have given rise to other forms of PCMT. Once initiated, PCMT can be terminated by a single P wave or by means of an appropriately timed atrial stimulus. Recognition by means of continued upper rate pacing may not be helpful in patients with a long V-A conduction interval because their PCMT rate will be low, thus requiring a low upper rate to trigger. Therefore, absolute prevention of PCMT has not yet been achieved, but PCMT is no longer a significant problem in DDD pacing; recognition of PCMT should not be related to the ventricular upper rate limit.

Atrioventricular Node↗
PubMed1985

Arrhythmias induced during termination of supraventricular tachycardia.

Pacing is being used frequently for the treatment of drug-resistant, paroxysmal supraventricular tachycardias (SVT). SVT can usually be terminated by pacing, but arrhythmias may be induced which interfere with the safety of antitachycardia pacing. To quantify these pacing-induced arrhythmias, 453 attempts to terminate SVT in 111 patients were analyzed. The patients were 6 to 73 years old (mean 41); 62 were male. Seventy-six patients had SVT using an accessory atrioventricular bypass, and 35 patients had intranodal SVT. Single and then, if required, multiple ventricular and atrial premature beats and overdrive pacing were delivered from the atrium and ventricle. A pacing-induced arrhythmia occurred in 9% of all attempts (34% of patients). Atrial flutter or fibrillation (AF) was the most frequent arrhythmia (in 8% of all attempts and sustained in 75%). Atrial vs ventricular pacing resulted in a 12% vs 2% incidence of AF. AF was unrelated to age, sex, atrial size and SVT type, and was predominantly induced by multiple premature beats. In 6 patients a different SVT and in 2 patients a nonsustained ventricular tachycardia was induced. In 6 patients SVT could only be terminated by initiating another arrhythmia. Thus, AF is frequently induced during attempted pacing termination of SVT. To limit the risk of AF, a single premature beat should preferentially be used to terminate SVT. In 6% of patients, SVT can only be terminated by inducing another arrhythmia.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1985

Automatic pacemaker termination of two different types of supraventricular tachycardia.

A new antitachycardia pacemaker system was used in a 58 year old woman to terminate two different types of supraventricular tachycardia by a single automatic pacing mode. During the invasive electrophysiologic study before pacemaker implantation (in the absence of medication), sustained episodes of atrioventricular (AV) nodal reentrant tachycardia and two short-lasting episodes of nonsustained atrial tachycardia were induced. After implantation, sustained episodes of both AV nodal tachycardia and atrial tachycardia were initiated. Both arrhythmias could be terminated reproducibly by a single pacing mode.

Automation↗
PubMed1985

PACTOT: a reprogrammable software pacing system.

The long battery life in modern pacemakers has created the need for pacemakers in which all the parameters can be changed and updated. The availability of such a system has potential advantages: new pacing techniques can be programmed without reoperation; the number of different pacemaker systems in stock in a hospital can be reduced to this reprogrammable unit; and, finally, this system can be of great help in designing and evaluating new pacing strategies.

Computers↗
PubMed1985

Evaluation of pacemaker performance using computer simulation.

A description is given of a mathematical model of impulse conduction through the heart. The model can be used to evaluate the best pacing mode for the individual patient and to develop new pacemakers. This allows study of the influence of different parameters related to the behavior of the heart or pacemaker. Two examples using a model of a DDD pacemaker and two examples describing simulation of an antitachycardia pacing system are given to illustrate how the performance of pacemakers under different conditions can be simulated.

Electrophysiology↗
PubMed1984

Value of lead V4R for recognition of the infarct coronary artery in acute inferior myocardial infarction.

In 84 patients with an acute inferior wall myocardial infarction (MI) admitted within 10 hours after the onset of chest pain, a right precordial lead V4R electrocardiogram was recorded in addition to the standard 12-lead electrocardiogram. The presence or absence of ST-segment elevation in lead V4R was correlated with results of coronary angiography performed 2 to 26 weeks (mean 10) after MI. Patients were classified into 3 groups: (1) those with a critical stenosis or occlusion proximal to the first right ventricular (RV) branch (27 patients); (2) those with stenosis distal to the right ventricular branch of the right coronary artery (36 patients); and (3) those with stenosis in the left circumflex coronary artery (21 patients). The presence of ST-segment elevation greater than or equal to 1 mm in lead V4R has a sensitivity of 100% and a specificity of 87% for occlusion of the right coronary artery above the first RV branch; the predictive accuracy is 92%. Seven of 36 patients with a distal occlusion of the right coronary artery showed ST-segment elevation of 1 mm or more in lead V4R . The absence of ST-segment elevation greater than or equal to 1 mm in lead V4R excluded proximal occlusion of the right coronary artery. ST-segment elevation in lead V4R was not seen either in 29 of 36 patients with a distal occlusion of the right coronary artery or in all patients with an occlusion of the left circumflex artery. Recording of lead V4R within 10 hours after onset of acute inferior wall MI can give information rapidly about the vessel responsible for MI.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1984

Noninvasive evaluation of pacemaker circus movement tachycardias.

Ventriculoatrial (VA) conduction was studied in 11 patients before DDD pacemaker implantation by incremental right ventricular pacing while recording right atrial endocavitary signals. After implantation and at 3-month outpatient visits, VA conduction and ability to initiate and sustain pacemaker circus movement tachycardia (PCMT) were systematically assessed noninvasively by testing the response of the pacemaker to asynchronous and single synchronized chest wall stimuli, muscle signals, and programmer pertubations. VA conduction was demonstrated in 3 of 11 patients before implantation as well as by noninvasive techniques after implantation with induction of PCMT. VA conduction became apparent in 2 additional patients after implantation. One of the 2 patients presented clinically with PCMT. In both patients, PCMT could be induced noninvasively. The presence or absence of VA conduction was variable, as was the rate of right ventricular pacing at which VA block occurred. In conclusion, (1) noninvasive testing techniques were effective in inducing PCMT in all patients with VA conduction and helpful in determining control of PCMTs, and (2) thorough preimplantation and repeated postimplantation assessment is needed to control and prevent PCMT.

Adult↗