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Biomedical subjects

M Glikson

Publications and source records attributed to M Glikson.

At least 37 records · Page 2Linked to original sources
PubMed1999

Clinical surveillance of a tined, bipolar, steroid-eluting, silicone-insulated ventricular pacing lead.

Since 1990, 1,068 Medtronic 5024 bipolar, silicone-insulated, tined, steroid-eluting ventricular leads have been implanted at the Mayo Clinic (Rochester, MN) and Midelfort Clinic (Eau Claire, WI). Implantation data were favorable: median pacing thresholds of 0.5 V at 0.5 ms, median R wave of 13.4 mV, and median impedance of 593 omega. Of the 2.1% acute lead-related complications (dislodgment, microdislocation, diaphragmatic pacing, and undersensing), 1.2% necessitated reoperation. This rate is lower than that in most published series of other leads. During a median follow-up of 23 months (up to 76 months), 12 (1.1%) chronic lead-related complications (high thresholds, loss of capture, and undersensing) and no instances of definite or suspected lead material failure occurred. This rate is much lower than that in studies of other leads. Thus, the 5024 lead combines the reliability of silicone insulation with a low rate of chronic complications that is probably the result of its steroid elution. No evidence of failure of lead material has appeared up to 6 years after implantation.

Adolescent↗
PubMed1999

Clinical surveillance of a tined, bipolar, J-shaped, steroid-eluting, silicone-insulated atrial pacing lead.

Since 1990, 558 Medtronic 5524 bipolar, silicone-insulated, J-shaped, tined, steroid-eluting atrial leads have been implanted at the Mayo Clinic (Rochester, MN, USA) and the Midelfort Clinic (Eau Claire, WI, USA). Implantation data were favorable, with pacing thresholds at implantation (median threshold, 0.6 V) better than most published data on other atrial leads. The rate of acute lead-related complications (dislodgment and diaphragmatic pacing) necessitating reoperation or electrical abandonment of the atrial lead was 0.9%. This rate is lower than that in most published series of atrial leads. Over a median follow-up time of 17.5 months (up to 69 months), there were no chronic lead-related complications and no definite or suspected failures of lead material. This rate is much lower than that with other atrial leads studied previously. We conclude that the Medtronic 5524 atrial lead combines the reliability of silicone insulation with a lack of chronic complications and high thresholds due to its steroid elution and with stability in the atrium due to its J shape despite a passive fixation mechanism. There is no evidence of lead material failure during up to 6 years of follow-up.

Administration, Topical↗
PubMed1999

Defibrillation thresholds are increased by right-sided implantation of totally transvenous implantable cardioverter defibrillators.

Whether an ICD is placed via a left- or right-sided approach depends on venous access, the presence of a preexisting pacemaker, and other factors. Since the DFT is affected by lead position, which in turn is determined in part by the side of access, right-sided venous access could adversely affect DFTs. Furthermore, right-sided active can placement directs electric current toward the right hemithorax, which could further increase DFTs. This study sought to determine whether DFTs were increased by right-sided vascular access, and whether active can technology was beneficial or detrimental with right-sided ICD placement. Stepdown to failure DFTs were found in 290 patients receiving transvenous systems at the time of initial ICD implantation. Of these, 271 (93%) received left-sided systems and 19 (7%) received right-sided systems. The mean DFT in systems placed via left-sided vascular access was 11.3 +/- 5.3 J versus 17.0 +/- 4.9 J for right-sided implantation (P < 0.0001); right-sided DFTs were elevated for both active can and cold can systems. Right-sided active can devices had a lower DFT than right-sided cold can systems (15 +/- 4.1 J vs 19 +/- 4.8 J, P = 0.05). The right-sided implantation of implantable defibrillators results in significantly higher DFTs than the left-sided approach. This may be due to the less favorable distribution of the defibrillating field relative to the myocardium with the devices on the right. When right-sided implantation is clinically mandated, active can devices result in lower thresholds and should be used.

Adult↗
PubMed1998

Noninvasive diagnosis of dual AV node physiology in patients with AV nodal reentrant tachycardia by administration of adenosine-5'-triphosphate during sinus rhythm.

BACKGROUND: Atrioventricular nodal reentry tachycardia (AVNRT) represents the most commonly encountered type of regular paroxysmal supraventricular tachycardia. This study determined whether administration of adenosine-5'-triphosphate (ATP) during sinus rhythm may be useful in the noninvasive diagnosis of dual AV nodal pathways. METHODS AND RESULTS: During electrophysiological study, we intravenously administered incremental doses of ATP (from 10 to 50 mg) during sinus rhythm to patients with spontaneous and inducible sustained AVNRT (study group, n=42) and to patients with no evidence of dual AV nodal physiology or inducible AVNRT (control group, n=21). Signs suggestive of dual AV node physiology after ATP administration during sinus rhythm ("jump" of AH > or =50 ms between 2 consecutive beats, > or =1 AV nodal echo beat, or initiation of AVNRT) were observed in 32 (76%) of 42 study patients but in only 1 (5%) of the 21 control patients (P<0.001). Similar results were observed when only surface lead recordings (without intracardiac recordings) were evaluated. Signs suggestive of dual AV node physiology by the ATP test were observed in 29 (80.5%) of 36 patients who had electrophysiological demonstration of dual AV node physiology and in 3 (50%) of 6 patients without AV nodal duality (P=NS). Signs suggestive of dual physiology according to the ATP test disappeared in 11 (92%) of the 12 patients who underwent successful slow AV nodal ablation but persisted in 8 (62%) of 13 patients who underwent AV nodal modification. CONCLUSIONS: Administration of ATP during sinus rhythm may be a useful bedside test for identifying patients with dual AV nodal pathways who are prone to AVNRT. This simple test should be considered as a screening test for patients with symptoms suggestive of paroxysmal supraventricular tachycardia but no documented arrhythmias or for patients with documented narrow complex tachycardia of unclear mechanism.

Adenosine Triphosphate↗
PubMed1998

Pneumothorax: an unusual cause of ICD defibrillation failure.

We describe two patients with defibrillation failure of implantable cardioverter defibrillators (ICDs) resulting from large left pneumothoraxes following subclavian vein puncture during the implantation. Following pneumothorax drainage, low defibrillation thresholds (DFTs) were attained without further manipulations. The absence of other signs and symptoms of pneumothorax and the presence of satisfactory pacing function during the procedure, resulted in a significant delay in diagnosis. Pneumothorax should be included in the differential diagnosis when unexpected high DFTs are found during ICD implantation or predischarge testing. This complication is avoidable by a different surgical approach, cephalic vein cutdown.

Aged↗
PubMed1998

Importance of pacemaker noise reversion as a potential mechanism of pacemaker-ICD interactions.

Numerous types of interactions between pacemakers and implantable cardioverter defibrillators (ICDs) have been described. Pacemaker outputs preventing appropriate detection of ventricular tachycardia or ventricular fibrillation by the ICD is one of the more serious. Asynchronous pacemaker activity during ventricular arrhythmias may be caused by either nonsensing of the arrhythmia or by noise reversion, which is an algorithm that causes the pacemaker to switch to asynchronous pacing when repetitive sensing at a high rate occurs. We analyzed the mechanisms underlying asynchronous pacemaker activity in ventricular arrhythmias using pacemaker telemetry during the arrhythmia. Thirty-nine induced arrhythmias from 26 different procedures in 19 patients with both pacemakers and ICDs were analyzed. Of the 39 arrhythmias, asynchronous pacemaker activity occurred in 16. The underlying mechanism was nonsensing in 4 episodes and noise reversion in 12 episodes. Clinically significant interference with detection arose on three occasions. Conditions favoring the occurrence of noise reversion include specific pacemaker models, arrhythmia cycle lengths in the range causing noise reversion of the individual pacemaker model, long noise sampling periods, and VVI pacing mode. Noise reversion can be diagnosed by telemetering the pacemaker marker channel during ventricular arrhythmias as a part of routine pacemaker-ICD interaction evaluation. It can be prevented or minimized by programming short ventricular refractory periods or using pacemakers with short retriggerable refractory periods.

Bradycardia↗
PubMed1997

Indications, effectiveness, and long-term dependency in permanent pacing after cardiac surgery.

The purposes of this study were to define predictors of long-term pacemaker dependency in patients having permanent pacemakers implanted shortly after cardiac surgery, and to evaluate short- and long-term results and survival in this population. Data from 120 adult patients with implantation since 1980 were retrospectively analyzed. Acute and chronic complication rates (4.2% and 16.6%, respectively) were not higher than those expected in the general paced population. In addition, continuous rhythm was evaluated by use of pacemaker inhibition in a subgroup of 20 patients to verify the validity of clinical criteria for pacemaker dependency. Of the patients evaluated for dependency, 41% eventually became nondependent. Prolonged monitoring with an inhibited pacemaker confirmed the accuracy of our method of clinical evaluation of pacemaker dependency. Significant predictors of long-term pacemaker dependency were complete atrioventricular block as the indication and bypass time of > 120 minutes (by multivariate and univariate analyses, respectively). Postoperative complete atrioventricular block is the most important predictor of pacemaker dependency, enabling an earlier decision on permanent pacemaker implantation (no later than the sixth and the ninth postoperative days for wide-complex and narrow-complex escape, respectively). Further prospective studies are needed to define optimal implantation times for indications other than complete atrioventricular block.

Adult↗
PubMed1997

Newer clinical applications of pacing.

For many years, the indications for permanent cardiac pacing consisted primarily of AV block and sinus node dysfunction. In recent years, the indications for pacing have expanded considerably. This article details recent advances in the application of permanent pacing and the use of permanent pacing for patients with hypertrophic cardiomyopathy, dilated cardiomyopathy, prevention of atrial fibrillation, and pacing in the long QT syndrome. Pacing is now an accepted therapeutic modality in hypertrophic cardiomyopathy and has rapidly gained acceptance in the United States, although there are still many unknowns about selection of patients and long-term benefits. Even less is known about pacing for dilated cardiomyopathy. Certain patients do respond with definite subjective improvement and improved quality of life, although there are no data to date to suggest improved longevity. Pacing for long QT syndrome is now a well-accepted indication for this relatively small subset of patients. Pacing for the prevention of atrial fibrillation is still in the very early stages of development. Multiple methods have been tried with the current method of choice being dual site atrial pacing. However, it is too early to predict the long-term success of this modality.

Adult↗
PubMed1996

Short- and long-term results with an active-fixation, bipolar, polyurethane-insulated atrial pacing lead.

Since 1989, 136 Medtronic 4058 and 4058M bipolar atrial screw-in leads have been implanted at the Mayo Clinic. Early lead related complications included dislodgment in 4 (2.9%). Over a median follow-up time of 14.4 months (1 day to 3.3 years), there were 11 lead related complications (undersensing, failure to capture, diaphragmatic pacing, and gross lead dislodgment). Chronic complications resulted in reoperations in four patients (2.9%). Of 77 patients in whom pacing thresholds were measured between 2 and 4 months after implantation, 9 (11.7%) and 2 (2.6%) had high pacing thresholds and very high thresholds, respectively. The Kaplan-Meier estimate of the probability of 1-year complication-free lead survival was 93.5%. There were no lead material failures. We conclude that the 4058/4058M lead implanted in the atrial position has favorable acute and chronic performance data, with a tendency toward high pacing thresholds at 3 months. The cause of this phenomenon and its course over time should be further evaluated.

Actuarial Analysis↗
PubMed1995

Expanding indications for permanent pacemakers.

PURPOSE: To review the current clinical experience with new and expanding indications for permanent cardiac pacing. DATA SOURCES: A MEDLINE search was done of the English-language literature published from 1980 through 1994 about indications for permanent pacing. Five major areas were identified and searched: cardiomyopathies, atrial fibrillation, the long QT syndrome, cardiac transplantation, and vasovagal syncope. A manual search was then done for other contributions, including abstracts. STUDY SELECTION: Because published reports in these areas are scarce, all of the peer-reviewed articles and most of the relevant abstracts found were reviewed. DATA EXTRACTION: Data were manually extracted from the various sources, and the reports were classified and summarized according to specific indications. RESULTS: Pacing is becoming an important option in the treatment of patients with symptomatic drug-resistant hypertrophic obstructive cardiomyopathy. Symptomatic and hemodynamic benefits have been shown in patients with pacing over various periods of follow-up. In patients with the long QT syndrome in whom medical therapy had failed, pacing at relatively fast rates markedly reduced symptoms and almost completely abolished fainting spells. Preliminary results suggest that pacing may be beneficial in dilated cardiomyopathy and in preventing episodes of paroxysmal atrial fibrillation. Further studies are needed to clarify the mechanisms of and to improve selection criteria for pacing in these conditions. Our ability to select cardiac transplant recipients for permanent pacing and our ability to optimize the timing of pacing in these patients have recently improved considerably. The role of pacing therapy in patients with neurally mediated (vasovagal) syncope remains incompletely understood. Better classification of these patients, made according to the sequence of hemodynamic events leading to syncope, is likely to clarify the potential benefit of pacing in these patients and improve the selection of patients for pacing. CONCLUSION: Few peer-reviewed clinical trials have been done, and further studies are needed to confirm the promising effects of pacing in patients with these newly recognized and expanding indications for pacing.

Atrial Fibrillation↗
PubMed1994

Low molecular weight heparin (Fragmin) prevents early reocclusion following femoral artery thrombolysis with rt-PA in rabbits.

The purpose of this study was to evaluate the effect of low molecular weight heparin Fragmin on thrombolysis with tissue-type plasminogen activator (rt-PA) and to compare its effect to that of standard heparin. A rabbit thrombosis model was used, consisting of a blood clot produced in an isolated femoral artery segment with superimposed endothelial damage and distal stenosis. Thirty rabbits were randomized to three treatment groups with rt-PA (30 micrograms.kg-1.min-1 for 60 min and no additional therapy), rt-PA with i.v. standard heparin (200 IU.kg-1 bolus and then 70 IU.kg-1 hourly) and rt-PA with s.c. Fragmin (a single dose of 500 IU.kg-1) prior to rt-PA administration. In six of 10 rabbits given rt-PA only, recanalization was observed which was persistent in three. In eight of 10 rabbits given rt-PA with intravenous heparin, reflow was achieved, which was persistent in three. Fragmin resulted in recanalization in eight of 10 rabbits, with persistent patency in each recanalized rabbit. Reflow time was not shortened with either standard heparin or Fragmin compared with rt-PA alone (64 +/- 41, 56 +/- 18, 50 +/- 23 min respectively), (P = 0.7). Persistent reocclusion after reflow was not observed with Fragmin (0/8) but was present with both standard heparin (5/8, P = 0.03 vs Fragmin) and rt-PA alone (3/6, P = 0.05 vs Fragmin). Thus, in the femoral artery of the rabbit, Fragmin, unlike standard heparin, was found to prevent reocclusion following rt-PA thrombolysis.

Animals↗
PubMed1994

Recent advances in cardiac pacing.

This article reviews recent studies, chapters, and review articles describing advances in cardiac pacing. Initially we discuss expanding and controversial pacing indications, including neurocardiogenic syncope and hypertrophic as well as dilated cardiomyopathies. Recent contributions to the understanding of factors influencing pacing mode selection are then discussed, including survival and atrial fibrillation in the various modes, the hemodynamic importance of atrioventricular synchrony and adaptive atrioventricular intervals, the importance of rate adaptation, the development of pacemaker syndrome, pacemaker response to the development of atrial arrhythmias, and special pacing modes such as VDD and AAIR. Finally, recent advances in rate-adaptive sensors and algorithms are reviewed, including preliminary results with dual sensors.

Bradycardia↗
PubMed1994

Clinical surveillance of an active fixation, bipolar, polyurethane insulated pacing lead, Part II: The ventricular lead.

Since 1989, 72 Telectronics 330-201 active fixation, polyurethane insulated ventricular leads (Accufix) have been implanted at the Mayo Clinic. There were four (5.6%) acute lead related complications (perforation, microdislodgment, and macrodislodgment), three of which led to early reoperation. Over a follow-up time of up to 2.7 years (median 9.4 months), there were six (8.3%) chronic lead related complications but no failures of lead material. Most of these complications developed during the first month, and half of them were transient, with documented improvement later. Two patients (2.8%) required reoperation for chronic complications. At follow-up examination of the pacing thresholds, usually performed about 3 months after implantation, 14.3% of the examined patients had high pacing thresholds necessitating high-output programming. The mechanisms and later evolution of this phenomenon should be further evaluated.

Adult↗
PubMed1994

Clinical surveillance of an active fixation, bipolar, polyurethane insulated pacing lead, Part I: The atrial lead.

Since 1989, 168 Telectronics model 330-801 active fixation, polyurethane insulated atrial leads (Accufix) have been implanted at the Mayo Clinic. There were four (2.4%) acute lead related complications, (i.e., perforation, microdislodgment, and pericarditis). Over a median follow-up time of 7.6 months (up to 2.7 years), there were 14 (8.3%) chronic complications, including 1 instance (0.6%) of definite lead failure. Most of these complications were early (within the first month) and transient. Four patients (2.4%) required reoperation for chronic complications. During follow-up, 23% of the examined patients had high pacing thresholds, most at about 3 months after implantation, necessitating high-output programming. The exact mechanism and natural history of this phenomenon should be further investigated.

Adolescent↗
PubMed1994

Electrical injury in the femoral artery of rabbits as a model for arterial thrombosis: a pilot study.

Electrical stimulation was delivered to the femoral artery of 20 rabbits to examine whether endothelial injury results in a consistent formation of arterial thrombosis. The arterial patency was monitored throughout the experiment by flowmeter and was visualized by femoral angiography in 5/20 cases. The arterial segments remained totally occluded in 7/20 (35%), partially occluded in 9/20 (45%), and patent in 4/20 (20%) rabbits following stimulation with 200 microA anodal current for 180 minutes. The average time of electrical stimulation needed to achieve total occlusion (n = 7) was 110 +/- 49 minutes. Alternating occlusion and recanalization of the artery (cyclic flow variation) was observed in 12 rabbits, with total occlusion ensuing in 6/12 cases. Intravenous administration of recombinant tissue-type plasminogen activator (20 micrograms/kg/min for sixty minutes) resulted in femoral reflow and subsequent reocclusion in 2/5 cases. Histopathologic examination disclosed arterial thrombi composed of platelets, fibrin, and red blood cells. Thus, according to these data this technique was found to induce arterial thrombosis following electrical stimulation of the rabbit femoral artery but was inconsistent regarding the arterial patency.

Animals↗
PubMed1993

From swirling to a mobile, pedunculated mass--the evolution of left ventricular thrombus despite full anticoagulation. Echocardiographic demonstration.

We describe the unusual evolution of a left ventricular thrombus following acute anterior myocardial infarction despite adequate anticoagulation. Serial echocardiographic examinations demonstrated the evolution from swirling in the left ventricle through a solid apical mass gradually dislodging into a mobile, pedunculated mass that was removed surgically to prevent embolization. This report emphasizes the need to follow echocardiographically left ventricular thrombi during treatment with anticoagulants, and to identify morphologic changes that may predict embolization. This case suggests that left ventricular thrombectomy should be considered in selected patients in whom a very high-risk thrombus morphology is detected.

Anticoagulants↗