Biomedical subjects

M Jazayeri

Publications and source records attributed to M Jazayeri.

At least 37 records · Page 2Linked to original sources

PubMed1994

Efficacy and safety of atrioventricular nodal modification for atrioventricular nodal reentrant tachycardia in the pediatric population.

The safety and efficacy of radiofrequency catheter modification of the atrioventricular node for atrioventricular nodal reentrant tachycardia in the pediatric population is described. Twenty-one patients with a mean age of 14.9 +/- 3.6 years underwent slow-pathway atrioventricular nodal modification with a stepwise anatomic approach. The average cumulative fluoroscopy exposure time (22 procedures in 21 patients) inclusive of the electrophysiologic study was 36.1 +/- 22 minutes. Noninducibility of tachycardia was achieved in all patients with one procedural complication (hemothorax). During a mean follow-up of 15 +/- 9.06 months, tachycardia recurred in one patient. Patient and family acceptance and satisfaction with the procedure was high. Because of the curative potential of radiofrequency catheter modification with low associated short- and long-term risks, it may be considered as a primary treatment option in pediatric patients with symptomatic atrioventricular nodal reentrant tachycardia.

Adolescent↗

PubMed1994

Preliminary experience with a hybrid nonthoracotomy defibrillating system that includes a biphasic device: comparison with a standard monophasic device using the same lead system.

OBJECTIVES: This study analyzed the advantage of combining a biphasic device with a transvenous system and compared the results with those obtained with a standard monophasic device. BACKGROUND: Available lead systems use monophasic pulses and may require lengthy intraoperative testing to achieve adequate defibrillation threshold in a conspicuous number of patients. The option of biphasic waveform may provide further benefits. However, clinical experience with a permanent implant is lacking. METHODS: Fifty-five patients underwent testing and received a permanent implant using the Endotak lead system associated with a CPI monophasic device. The remaining 36 patients received a permanent implant with the Endotak lead system connected to a biphasic device. In both groups a subcutaneous patch was combined when needed to obtain acceptable defibrillation thresholds. RESULTS: Biphasic pulses resulted in lower mean (+/- SD) defibrillation thresholds (monophasic 15 +/- 4.7 J vs. biphasic 12 +/- 5 J, p = 0.03) and a better implantation rate (100% biphasic vs. 89% monophasic, p = 0.07). Biphasic pulses allowed implantation with less ventricular fibrillation induction (7.4 +/- 3.2 vs. 3.5 +/- 1.8, p < 0.01) and a mean shorter procedure time (168 +/- 39 vs. 111 +/- 30 min, p < 0.01). With the biphasic waveform a greater proportion of patients met the implantation criteria with the lead system alone (83% vs. 45%, p < 0.01). When needed, the left prepectoral location of the patch electrode was always sufficient in left subscapular position was required in 15 patients in the monophasic group. Implantation of the biphasic device was associated with a shorter mean hospital stay (3.8 +/- 0.8 vs. 5.4 +/- 2.2 days, p < 0.01). CONCLUSIONS: Incorporation of a biphasic device in a transvenous implantable cardioverter-defibrillator uniformly increases the efficacy of the system and the ease of implantation.

Adult↗

PubMed1994

Experience with two different nonthoracotomy systems for implantable defibrillator in 170 patients.

Implantation of a nonthoracotomy system (Medtronic PCD or CPI Endotak) was attempted in 170 patients with ventricular tachycardia (VT) or ventricular fibrillation (VF) not requiring concomitant cardiac surgery. A nonthoracotomy system could be successfully implanted in 95 of the 115 patients with the PCD system and 49 of 55 patients receiving the Endotak lead system. In 26 patients with failed nonthoracotomy system because of defibrillation threshold (DFT) > 25 joules (J), an epicardial system was implanted at the same setting. Patients receiving the two lead systems were comparable with regard to age, sex, and ejection fraction. However, since the PCD system offers tiered therapy multiprogrammable options, all attempts were made to implant this lead system in patients with VT that could be pace terminated. Mean DFT (15 +/- 4.7 vs 17 +/- 4.6 J; P = 0.03) and implant time (2.5 +/- 0.6 vs 3.3 +/- 0.7 hours; P = 0.02) were less with the Endotak lead system. There was no perioperative mortality. During a mean follow-up of 20 +/- 4 months, there were eight instances of lead dislodgment in patients receiving the PCD system. There were four nonsudden cardiac deaths and one sudden death in the Endotak group and three nonsudden deaths in the PCD group. Sudden cardiac death and total survival using the intention-to-treat analysis during this follow-up period were 99% and 95%, respectively. In conclusion, successful implantation, perioperative mortality, and survival rate are comparable with both lead systems; however, incorporating two defibrillating electrodes in one lead minimizes lead dislodgment and reduces implant time.

Anti-Arrhythmia Agents↗

PubMed1994

Ventricular fibrillation and polymorphic ventricular tachycardia with critical coronary artery stenosis: does bypass surgery suffice?

INTRODUCTION: Previous studies have suggested that coronary artery bypass surgery is sufficient to prevent recurrence of sudden death in patients with critical coronary artery stenosis presenting with ventricular fibrillation or polymorphic ventricular tachycardia. We present our experience in patients with one or more episodes of sudden death associated with documented ventricular fibrillation or polymorphic ventricular tachycardia and severe operable coronary artery disease who underwent defibrillator implant at the time of bypass surgery. METHODS AND RESULTS: Fifty-eight consecutive patients (age 63 +/- 8 years) were included in this study. Eighteen of the 58 patients had no evidence of previous myocardial infarction. The mean ejection fraction was 37 +/- 13%. All patients underwent electrophysiologic study before and after revascularization. At the time of first defibrillator discharge, each patient was reevaluated to exclude the presence of ischemia. The benefits of defibrillator implant were estimated comparing the projected survival based upon defibrillator discharge preceded by syncope or presyncope with survival curves generated including total death and sudden plus cardiac death. After a mean follow-up of 4.6 +/- 2 years, 22 patients received appropriate shocks preceded by syncope or presyncope, and an additional 19 patients received asymptomatic shocks. At 4 years, survival free of total death was 71.2%, and the projected survival was 58.8% (P < 0.05). Multivariate analysis showed that ejection fraction lower than 30% and induction of arrhythmia with one or two extrastimuli (S2, S3) were independent predictors for defibrillator discharge. None of the remaining variables including age, gender, number of bypasses, history of myocardial infarction, and type of arrhythmias induced were predictive for death and occurrence of shocks. CONCLUSIONS: In patients with ventricular fibrillation and polymorphic ventricular tachycardia, bypass surgery does not protect from recurrence of life-threatening arrhythmias, and, as in our population, defibrillator implant may have significant impact on survival.

Adult↗

PubMed1993

Bundle branch reentry: a mechanism of ventricular tachycardia in the absence of myocardial or valvular dysfunction.

OBJECTIVES: The aim of this study was to present bundle branch reentry as the mechanism of sustained ventricular tachycardia in the absence of myocardial or valvular dysfunction. BACKGROUND: Previous reports have documented the relation between structural heart disease and bundle branch reentrant ventricular tachycardia. Myocardial or valvular dysfunction has thus far been recognized as the only anatomic substrate for the development of this tachycardia. METHODS: Three patients with a wide QRS complex tachycardia underwent noninvasive and invasive cardiac evaluation and electrophysiologic studies to identify the substrate and mechanism of tachycardia. Catheter ablation of the right bundle branch using radiofrequency current was performed in each patient. RESULTS: The patients were all men (aged 54, 34 and 72 years) who presented with presyncope, palpitation and cardiac arrest, respectively. Electrocardiography during sinus rhythm revealed nonspecific intraventricular conduction delay in all three patients. Cardiac evaluation revealed no evidence of myocardial or valvular dysfunction in any patient. The baseline HV interval was prolonged in each patient (90, 100 and 75 ms, respectively). Programmed right ventricular stimulation initiated bundle branch reentrant tachycardia with typical left (three patients) and right (one patient) bundle branch block pattern. Catheter ablation of the right bundle branch using radiofrequency current abolished bundle branch reentry in all three patients. After 26-, 13- and 8-month follow-up periods, complete right bundle branch block persisted, and all three patients remained asymptomatic without antiarrhythmic drugs. CONCLUSIONS: Sustained bundle branch reentry can be a clinical arrhythmia in patients with no identifiable myocardial or valvular dysfunction except for isolated conduction abnormalities in the His-Purkinje system. This mechanism of tachycardia should be recognized during electrophysiologic evaluation, given the seriousness of this arrhythmia and the availability of the effective treatment.

Adult↗

PubMed1993

Repeated use of ablation catheters: a prospective study.

OBJECTIVES: The objective of this study was to provide insight into the time course of electrical, physical and mechanical changes in ablation catheters after each use that may affect the safety and efficacy of the ablation procedure. BACKGROUND: An increasing number of institutions are reusing deflectable ablation catheters. At present, there are no data concerning the safety of reusing ablation catheters. METHODS: Over a period of 1 year, 69 Webster/Mansfield deflectable catheters used in 336 ablation procedures were prospectively studied. An additional 18 new catheters were tested after multiple sterilizations only. The catheters were evaluated for electrical and physical integrity and mechanical capabilities. These include deflection at room temperature and 37 degrees C, shaft compression and buckling during deflection, tip craters, torquing ability, glue separation and tip attachment using a stereoscope at x30 magnification and electrical resistance for each electrode. After each use, the catheters were gas-sterilized with ethylene oxide. RESULTS: The most common reasons for catheter rejection were tip electrode glue separation after 4.3 +/- 4.3 uses and loss of deflection after 5.0 +/- 3.3 uses. Electrical discontinuity between the catheter handle and electrodes was observed after 10.0 +/- 3.7 uses. There was no significant decrease in catheter torquing ability with repeated use. In this study the total estimated savings was $128,133, which includes the cost of catheter reprocessing. The reuse of Webster/Mansfield ablation catheters has not resulted in any major catheter failure or any major adverse clinical complications. CONCLUSIONS: On the basis of these observations, we believe that the Webster/Mansfield catheter can be reused an average of five times. It is strongly recommended that after each use catheters be carefully examined under appropriate magnification (x30) and that special attention be given to the ablation tip electrode. The catheters should also be tested for deflection and electrical integrity.

Catheter Ablation↗

PubMed1993

Physics and engineering of transcatheter cardiac tissue ablation.

Ablation of arrhythmogenic cardiac tissues has emerged as one of the most important advances in cardiac electrophysiology. With the introduction of transcatheter ablation, the treatment of ventricular tachycardia, Wolff-Parkinson-White syndrome and other cardiac arrhythmias has progressed from an expensive and painful surgical therapy accompanied by a long recovery period to the less expensive, less traumatic transcatheter approach. The feasibility of cardiac ablation, along with the increasing number of physicians using the technique, requires understanding of the anatomic and electrophysiologic bases of transcatheter ablation as well as the different technologies, their limitations and complications. This report provides an overview of the physical, scientific and technical aspects of cardiac ablation performed with the methods currently available and a summary of the limitations of each method and expected future technologic developments in this growing field. Emphasis is placed on radiofrequency and direct current energies, the primary methods now used. Methods such as cryoablation and laser, and microwave and chemical ablation are discussed with less detail because the method of delivering energy for these ablative procedures has not been fully developed.

Animals↗

PubMed1993

Cardioversion, defibrillation, and overdrive pacing of ventricular arrhythmias: the effect of moricizine in dogs with sustained monomorphic ventricular tachycardia.

The purpose of this investigation is to define whether the antiarrhythmic drug moricizine has beneficial or adverse effects on currently used antitachycardia and antifibrillatory devices. These studies were performed in a dog model of sustained monomorphic ventricular tachycardia (VT). In 11 dogs, the left anterior descending artery and all surrounding epicardial collateral feeder vessels were ligated. Defibrillator patches were implanted and the dogs were allowed to recover. After a 7-day recovery period, effective refractory period (ERP), end diastolic threshold (EDT), VT induction, and VT and ventricular fibrillation (VF) termination data were collected before and after moricizine infusion (2 mg/kg). In this experimental model, moricizine caused the following electrophysiological changes: a prolongation of the ERP from 173 +/- 14 to 182 +/- 15 (P < 0.02) with no significant effect on the EDT for pacing; a prolongation of the VT cycle length from 175 +/- 18 to 201 +/- 23 msec (P < 0.003); an increased cycle length required for overdrive pacing from 136 +/- 20 to 157 +/- 22 msec (P < 0.01); no effect on the energy required to cardiovert VT; an increase in the defibrillation threshold from 7.5 +/- 4 to 9.4 +/- 4 joules (P < 0.006) and; in 5 of the 8 dogs with VT, the VT could be initiated with somewhat less aggressive stimulation. Significant beneficial electrophysiological physiological effects were noted on the VT cycle length, including a proportionately prolonged overdrive pacing cycle length for VT termination.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1993

Implantable cardioverter defibrillator for prevention of sudden cardiac death in patients with ventricular tachycardia and ventricular fibrillation: ICD therapy in sudden cardiac death.

Among the various therapy options for survivors of ventricular tachycardia-ventricular fibrillation (VT-VF), the implantable cardioverter defibrillator (ICD) seems most promising. It reliably terminates VT-VF and thus significantly impacts sudden cardiac death (SCD) survival. It is more effective than any of the known antiarrhythmic drugs in prevention of SCD, particularly among survivors of cardiac arrest. Compared to VT surgery, the ICD therapy can be offered to a larger pool of patients and can be placed at a lower surgical risk. With proper patient selection, ICD therapy is of major benefits to its recipients since it markedly reduces the chances of VT-VF related mortality; the main cause of premature death in this population. The ICD therapy is cost effective when compared to other medical interventions and could be more so if the implant is carried out early in the course of VT-VF management.

Death, Sudden, Cardiac↗

PubMed1993

Bundle branch reentrant ventricular tachycardia: cumulative experience in 48 patients.

INTRODUCTION: The clinical, electrophysiologic features and follow-up of 48 patients with inducible bundle branch reentrant (BBR) tachycardia are presented. METHODS AND RESULTS: Forty-eight patients were identified in whom a diagnosis of BBR tachycardia was made during electrophysiologic evaluation. The clinical presentation was syncope or sudden death in 38 patients, and sustained palpitations during wide QRS complex tachycardia in 5 patients. Electrophysiologic studies were performed in 5 additional patients for various other reasons. Structural heart disease was present in 45 patients. Idiopathic dilated cardiomyopathy and coronary artery disease were the anatomical substrates in 19 (39%) and 24 (50%) patients, respectively, severe aortic regurgitation was present in 2 patients, and no organic heart disease was identified in 3. All 48 patients had evidence of His-Purkinje system disease. BBR tachycardia with left and right bundle branch block morphologies was induced in 46 and 5 patients, respectively, and interfascicular BBR tachycardia was initiated in 2 patients. Ventricular tachycardia of a myocardial origin was induced in 11 patients. Management of BBR tachycardia included transcatheter bundle branch ablation in 28 patients, and antiarrhythmic drug therapy in 16 patients. Four patients were treated with implantable defibrillators. After a mean follow-up of 15.8 months in 42 patients, there were 13 deaths due to congestive heart failure, 4 sudden cardiac deaths, 3 nonsudden cardiac deaths, and 3 noncardiac related deaths. CONCLUSION: Sustained BBR, a form of monomorphic ventricular tachycardia, is a highly malignant arrhythmia usually seen in patients with structural heart disease. Three different types of BBR tachycardia are described. If distinguished from ventricular tachycardia of a myocardial origin, catheter ablation of the right bundle branch can be easily performed and effectively eliminates BBR. During follow-up, congestive heart failure is the most common cause of death in this population.

Adult↗

PubMed1992

Induction of ventricular fibrillation versus monomorphic ventricular tachycardia during programmed stimulation. Role of premature beat conduction delay.

BACKGROUND: Premature stimuli can cause ventricular fibrillation (VF) during electrophysiological testing. The electrophysiological correlations associated with the onset of VF were evaluated in 40 patients who had this rhythm induced during programmed ventricular stimulation. These parameters were compared with those observed in 51 patients who had inducible sustained monomorphic ventricular tachycardia (VT) and 45 patients who had no inducible sustained ventricular tachyarrhythmias. METHODS AND RESULTS: Shortest premature coupling intervals for S2, S3, and S4 at induction of tachycardia or before achieving refractoriness, corresponding conduction latencies (defined as the time from the premature stimulus to the upstroke of the depolarization wave front recorded 35 mm away from the stimulation site), and ventricular activation times (defined as the time from the premature stimulus to the end of the depolarization wave) were compared. The mean coupling intervals were longest in the inducible VT patients: 300 +/- 30, 254 +/- 57, and 228 +/- 32 msec for S2, S3, and S4, respectively. In the inducible VF group, the coupling intervals were 260 +/- 37, 208 +/- 20, and 213 +/- 30 msec. In the group with no inducible VT or VF, these coupling intervals were 251 +/- 24 (p less than 0.01 versus inducible VT group), 209 +/- 27 (p less than 0.001 versus inducible VT group), and 194 +/- 21 msec (p less than 0.05 versus inducible VT and VF groups). The coupling interval of the last premature extrastimulus was above 200 msec in 70% of the patients in whom VF was induced. The largest increases in latency and activation times were recorded in patients in whom VF was induced. The cumulative increase in latency, defined as increased conduction time from baseline, summed for all the premature stimuli was also the greatest at initiation of VF. In contrast, the smallest increases in these parameters were noted in the patients with no inducible VT or VF. Measurements of total activation time yielded similar results as those recorded for latencies. The most important parameters distinguishing the VT patient population from the other two groups were the low ejection fractions and the longer coupling intervals at which VT was induced, whereas in the VF group, the most important discriminating factor was cumulative activation time. Sixty-three percent of the inducible VF patients presented with abnormal hearts (myocardial infarction or cardiomyopathy), whereas 88% of the inducible VT patients had abnormal hearts. In contrast, only 25% of the patients in whom no arrhythmia was induced presented with abnormal hearts. Mean ejection fraction was 32 +/- 15% for the inducible VT group, 45 +/- 13%* for the inducible VF group, and 51 +/- 17%* for patients with no inducible VT/VF (*p less than 0.001 versus VT). CONCLUSIONS: The results suggest that 1) initiation of ventricular tachycardia during programmed ventricular stimulation occurs with minimal conduction latency; 2) because of the large overlap in coupling intervals where VF or VT were induced, a single coupling interval cannot be recommended to adequately separate these groups; and 3) induction of VF was preceded by increased latency and prolongation of the local activation time. These parameters should not be allowed to prolong if VF is to be avoided during programmed stimulation. In addition, 4) the initiation of VF during electrophysiological studies is often associated with the presence of structural heart disease; such structural disease may promote conduction latency and the development of VF.

Cardiac Complexes, Premature↗

PubMed1992

Iontophoretic transmyocardial drug delivery. A novel approach to antiarrhythmic drug therapy.

BACKGROUND: Antiarrhythmic drugs often fail to achieve therapeutic effects without toxic systemic levels. Direct transport of drugs into the myocardium may circumvent this problem and may also provide new insights into antiarrhythmic drug effect on arrhythmogenic tissues. In a canine model, procainamide (PA) was delivered iontophoretically using pulsed current synchronized with the ventricular depolarization via an implantable defibrillator patch electrode that was modified to contain a 3.6-ml chamber. Myocardial tissue concentrations of PA were evaluated in 7-day myocardial infarcts (n = 16) that were exposed to 10 minutes of iontophoretic PA delivery and compared with passive diffusion (n = 5) and intravenous (n = 16) PA. These dogs were followed for 3 hours. The infarcted tissue PA levels were compared with normal myocardium. Coronary and systemic blood levels of PA, effective refractory period (ERP), diastolic threshold, and efficacy of ventricular tachycardia (VT) suppression were evaluated throughout the follow-up period. METHODS AND RESULTS: Three hours after 10 minutes of iontophoretic, passive, and intravenous PA, the epicardial layer concentration in the center of the infarcted zone was 840 +/- 853 micrograms/g, 93 +/- 90 micrograms/g, and 15 +/- 8 micrograms/g of tissue, respectively. In the endocardial layer, the PA concentrations with iontophoresis were 38 +/- 57 micrograms/g and were significantly higher than those achieved with either passive diffusion 38 +/- (4 +/- 2 micrograms/g) or with intravenous delivery (11 +/- 5 micrograms/g) (p less than 0.05). Epicardial tissue PA concentrations 3 hours after iontophoresis, passive diffusion, and intravenous PA in the normally perfused tissues were 14 +/- 13 micrograms/g, 3 +/- 2 micrograms/g, and 16 +/- 8 micrograms/g of PA, respectively. Venous blood levels were 2 +/- 3 micrograms/ml 3 hours after iontophoresis, 1 +/- 1 microgram/ml 3 hours after passive PA delivery, and 11 +/- 7 micrograms/ml with intravenous administration (p less than 0.05 intravenous versus passive and iontophoresis). Iontophoretic delivery of PA resulted in 22 +/- 29 msec ERP prolongation intramurally in the infarcted zone with no significant normal tissue ERP prolongation. Passive delivery of PA produced no significant changes in ERP. After intravenous infusion, the ERP in the infarcted zone increased by 35 +/- 29 msec and 13 +/- 12 msec in the normal tissue. Sustained monomorphic VT was induced in 20 animals. In one of these animals, only nonsustained VT could be induced at baseline; however, after intravenous PA, VT could be induced and remained inducible throughout the 3-hour follow-up period. In the iontophoretic delivery group, PA suppressed VT in all of the animals, with termination time ranging from 20 seconds to 7 minutes. In three cases, sustained monomorphic VT could be reinduced, two after 60 minutes and one after 120 minutes. However, in seven dogs, VT could not be induced during the 3-hour follow-up period. None of the dogs in which PA was delivered iontophoretically into the infarcted myocardium developed VT that was not induced before delivery of the drug. Intravenous PA administration resulted in VT suppression in one of 10 dogs. In two dogs, VT could not be induced before intravenous infusion of PA. However, after intravenous PA, VT could be induced. Immunohistochemical mapping of the PA within the infarcted tissue revealed transmural PA distribution. CONCLUSIONS: These data show that 1) the delivery of high transmural concentrations of PA directly into infarcted myocardium is both feasible and effective...

Animals↗

PubMed1992

Localization of the fast and slow pathways in atrioventricular nodal reentrant tachycardia by intraoperative ice mapping.

BACKGROUND: Atrioventricular (AV) nodal reentrant tachycardia is classically described as a reentrant rhythm entirely contained within the compact AV node. Although the concepts of longitudinal dissociation of two intranodal pathways and a distal common pathway are accepted, the proximal portion of the circuit remains undefined. Current reports suggest that the two pathways may be separable by atrial tissue and not contained entirely within the compact node. METHODS AND RESULTS: We used an ice mapping method to demonstrate the slow and fast pathways of the reentrant circuit and their relation to the atrial septum around the AV node. Six patients with the usual form (slow-fast) of AV nodal reentrant tachycardia were mapped during surgery. In most patients, antegrade slow pathway localization was posterior and inferior to the compact AV node along the tricuspid annulus; in two patients, it was superior along the tendon of Todaro. Retrograde fast pathway localization was anterior or superior to the compact AV node in all patients. In all patients, anatomic distinction was made between the two pathways and the compact node. CONCLUSIONS: We conclude that no upper common pathway exists within the compact AV node in the usual type of nodal reentrant tachycardia and that the perinodal atrial tissue is a requisite part of the tachycardia circuit.

Adolescent↗

PubMed1992

Role of implantable cardioverter defibrillator therapy in the management of high-risk patients.

Cardiovascular mortality from ventricular tachycardia (VT) and ventricular fibrillation (VF) continues to be a major health problem. Several therapeutic approaches are now available to treat patients with known VT/VF. Among the various therapeutic options are antiarrhythmic drugs, catheter or surgical ablation of VT focus, and implantable cardioverter defibrillator (ICD). The overall 2-year cardiovascular mortality is significantly reduced by ICD therapy. The ICD is particularly useful in patients with 1) no inducible but clinical VT/VF, 2) drug refractory VT/VF, and 3) VT/VF in association with left ventricular ejection fraction of less than or equal to 30%. Significant improvements in ICD therapy have already been made; these improvements include tiered antitachycardia therapy, antibradycardia pacing, lower defibrillation threshold, and longer life of generator. Further improvements are expected, including nonthoracotomy approach to defibrillation, pectoral implant, and dual chamber sensing. It is likely that with all of the advances in ICD therapy its acceptance as a therapeutic option will increase.

Costs and Cost Analysis↗

PubMed1991

Cardiovascular causes of syncope. Identifying and controlling trigger mechanisms.

Syncope usually has a cardiovascular source, so neurologic evaluation has a low diagnostic yield in these patients. Cardiac arrhythmias in persons with or without structural heart disease can produce syncope. Neurocardiogenic dysfunction that results in diminished venous return and hypercontractility is another frequent cause. Postural hypotension or left ventricular outflow obstruction may also be to blame. Careful history taking and physical examination, head-up tilt testing, echocardiography or radionuclide isotope imaging, and electrophysiologic study are often diagnostic. However, syncope remains undiagnosed in some patients, and they may require periodic reassessment. Treatment options are available for most cardiovascular disorders, among them use of pharmacologic agents; catheter, surgical, or radio-frequency modification of certain tachycardias; and permanent pacing.

Cardiac Pacing, Artificial↗

PubMed1991

When is it safe not to replace an implantable cardioverter defibrillator generator?

In most reports on patients receiving implantable cardioverter defibrillators, shocks were received mainly during the first 2 to 3 years. Thus, the question had been raised as to the need for device replacement after 3 or 4 years if no shocks had been received. In order to answer this question, shock experience in 184 patients receiving the implantable cardioverter defibrillator was analyzed. Patients were followed for a mean of 24 +/- 18.7 months. A patient's shock was judged to be appropriate if there was electrocardiographic documentation of sustained ventricular tachyarrhythmia at the time of shock or if it was preceded by sudden onset of presyncopal or syncopal symptoms. The majority of patients had coronary artery disease. In approximately two-thirds of patients, left ventricular ejection fraction was below 40%. One hundred fourteen patients had inducible sustained monomorphic ventricular tachycardia. On follow-up, there were 29 deaths, five of which were sudden. Sixty-eight patients received an appropriate shock during follow-up (37%). Over 90% of these 68 received their first shock within the 2 years after implant. The actuarial risk of receiving an appropriate shock by the fifth year after implant was 69%. Conversely, 31% of patients who survived 5 years had not received an appropriate shock. Hazard analysis indicates that there is a high incidence of first appropriate shock during the year following implant. Subsequently, the incidence dropped to a relatively steady rate with a rise in this rate during the fifth year. This analysis suggested a bimodal distribution of appropriate shocks.(ABSTRACT TRUNCATED AT 250 WORDS)

Actuarial Analysis↗

PubMed1991

Does reception of appropriate shocks from the implantable cardioverter defibrillator affect survival?

The implantable cardioverter defibrillator has become an important therapeutic modality for treatment of life-threatening ventricular tachyarrhythmias. Recent reports have suggested that patients who receive appropriate shocks from this device have an inordinately high overall mortality, and questioned the extent of benefit these patients derive from the implant. This report analyzed the survival among 184 patients who received the implantable cardioverter defibrillator to assess survival differences between patients who received appropriate shocks versus those who did not. At a mean follow-up of 24 +/- 18.7 months, 68 patients received an appropriate shock from their device while 116 did not receive an appropriate shock. Overall survival of the entire population was quite similar to those published by others. There was no significant difference between overall survival of patients who received an appropriate shock versus those who did not. However, there was a statistically significant difference in sudden death mortality. The group of patients that received appropriate shocks included all five sudden deaths. This observation suggested that sudden death in this population was likely due to ventricular tachyarrhythmias rather than strictly bradycardia or asystole. The "benefit" of the device to the entire population was also assessed by estimating survival after receipt of the first appropriate shock. Using this approach, an estimated 10% of patients died without receiving an appropriate shock. In other words, ultimately, 90% of patients were expected to benefit from the device. This survival curve, which initiated only after receipt of the first appropriate shock was fairly similar to those estimated from conventional methods. Therefore, survival after receipt of an appropriate shock was comparable to overall survival and there was no significant difference between survival of patients who received appropriate shocks and those who did not.

Death, Sudden, Cardiac↗

PubMed1990

Automatic implantable cardioverter/defibrillator discharges and acute myocardial injury.

Multiple defibrillations by the automatic implantable cardioverter/defibrillator (AICD) have been reported to result in localized epicardial damage. No data exist, however, regarding whether this damage can be detected in the clinical setting or whether it interferes with the detection of true myocardial infarction. Forty-nine patients who received defibrillations by patch electrodes were studied prospectively. We attempted to document the presence of myocardial injury with the following three commonly used modalities for the detection of myocardial infarction: serial electrocardiographic changes, serial creatine phosphokinase (CPK) and CPK-MB release, and technetium 99m pyrophosphate scanning. Fifteen patients received defibrillations by AICD patches at the time of AICD generator replacement. Nine patients received defibrillations at the time of new AICD lead placement. The average total energy delivered was 85 +/- 29 J. None of these patients had detectable myocardial injury. Ten patients had defibrillations by the AICD patches at the time of bypass operation. One patient in this group developed acute myocardial infarction in the inferior wall after posterior descending coronary bypass operation, as detected by electrocardiogram, 99mTc pyrophosphate scanning, and CPK-MB analysis. Fifteen patients were evaluated for spontaneous AICD discharges. Thirteen had a maximum of five consecutive shocks, and cumulative energy delivered was not greater than 330 J. None of these patients had detectable injury. Two patients had CPK-MB release of 15.3% and 7.5%, respectively. One of these patients had a positive 99mTc pyrophosphate scan. These two patients received 12 and 17 rapid and consecutive AICD discharges, respectively, with cumulative delivered energy of 360 and 510 J, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗