Search Results
Results 651 - 700 of 1048
< 9 10 11 12 13 14 15 16 17 18 19 >
Nisam S - - 1997
Efficacious therapy for chronic coronary patients, known to be at high risk of sudden arrhythmic death, has been a long-lasting challenge for cardiologists. The "Multicenter Automatic Defibrillator Implantation Trial" (MADIT) has demonstrated in a prospective, randomized trial that such patients achieve 54% better survival (p < or = 0.009) when ...
Tomassoni G - - 1997
BACKGROUND: Recent studies have shown that specifically shaped biphasic waveforms can lower energy requirements for ventricular defibrillation. We prospectively compared the defibrillation efficacy of three different biphasic wave shapes incorporated in three commercially available implantable defibrillators. The results led to the development of a second protocol in which the importance ...
Barold H S - - 1997
This case describes ventricular proarrhythmia as a result of a synchronized internal atrial defibrillation shock in a 29-year-old man with Ebstein's anomaly referred for radiofrequency ablation of a right posterior accessory pathway. During the electrophysiologic study, atrial fibrillation was induced and 3/3 msec shocks of various strengths were delivered between ...
Fotuhi P C - - 1997
OBJECTIVES: We investigated the impact of an inactive endocardial lead on the 50% effective dose (ED50%) for successful ventricular defibrillation. BACKGROUND: The presence of abandoned epicardial mesh patch electrodes detrimentally affects the defibrillation efficacy of an endocardial lead system. It is not known whether abandoned endocardial electrodes produce a similar ...
Behrens S - - 1997
OBJECTIVES: This study investigated the effects of acute global ischemia on the vulnerable window, the upper limit of vulnerability and the defibrillation threshold. BACKGROUND: Myocardial ischemia, an important factor for arrhythmogenesis and sudden death, may affect the inducibility of ventricular fibrillation by T wave shocks as well as the defibrillation ...
Dorian P - - 1997
Electrical storm is defined as recurrent, hemodynamically destabilizing ventricular tachycardia or ventricular fibrillation occurring two or more times in a 24 h period, and usually requiring electrical cardioversion or defibrillation. Recent advances in the understanding of the pathogenesis of this serious arrhythmia and in its pharmacological management have improved the ...
Martin D J - - 1997
INTRODUCTION: The upper limit of vulnerability (ULV) is the shock strength at or above which ventricular fibrillation cannot be induced when delivered in the vulnerable period. It correlates acutely with the acute defibrillation threshold (DFT) and can be determined with a single episode of fibrillation. The goal of this prospective ...
Strohmenger H U - - 1997
OBJECTIVE: The purpose of this study was to assess from the ventricular fibrillation ECG signal whether certain amplitude parameters, or frequency parameters derived using fast Fourier transform analysis, are predictive of countershock success (defined as a stable supraventricular rhythm following countershock). DESIGN: Retrospective, descriptive study. SETTING: Emergency medical service at ...
Peralta A O - - 1997
OBJECTIVE: Evaluation of the impact of undersensing on VF detection time and the relationship of undersensing to the programmed shock energy. BACKGROUND: Failure to reconfirm an ongoing arrhythmia due to undersensing by a noncommitted ICD might prolong the time to therapy. METHODS: We measured initial detection times and redetection times ...
Murakawa Y - - 1997
OBJECTIVES: We tested whether a new class III drug (MS-551) administered during ventricular fibrillation (VF) could decrease the defibrillation threshold (DFT) in anesthetized canine hearts. BACKGROUND: Pretreatment with class III antiarrhythmic agents is known to enhance electrical defibrillation efficacy. METHODS: In a preliminary study (n = 10), we ascertained the ...
Link M S - - 1997
OBJECTIVES: This study evaluates the hypothesis that in patients with syncope of unknown origin, inducible ventricular arrhythmias are specific arrhythmias and therefore should be appropriately treated. BACKGROUND: Although syncope is a common clinical entity, the evaluation and treatment of patients with syncope without a clear etiology are not well defined. ...
Dorian P - - 1997
INTRODUCTION: Drugs which primarily prolong cardiac refractoriness decrease defibrillation voltage and energy requirements in animals and man. The effect of such drugs on ventricular fibrillation itself is not well understood. We hypothesized that tedisamil, an investigational antiarrhythmic drug which blocks Ito and IK repolarizing potassium channels, would increase organization of ...
Herlitz J - - 1997
AIM: To describe rhythm changes during the initial phase of resuscitation from ventricular fibrillation in relation to the interval between collapse and defibrillation, to survival and to bystander-initiated cardiopulmonary resuscitation (CPR). PATIENTS: All patients who suffered out-of-hospital cardiac arrest between 1980 and 1992, who were reached by the emergency medical ...
Luceri R M - - 1997
The use of transvenous ICD systems and the recent advances in atrial defibrillation techniques have heightened interest in internal defibrillation. However, most shocks for induced or spontaneous arrhythmias in patients without devices are still delivered transthoracically using high energy. We describe the history of temporary internal defibrillation techniques and report ...
Ayers G M - - 1997
Episodes of sustained atrial fibrillation have long been effectively treated with external, transthoracic defibrillation. Despite concomitant, postcardioversion therapy with antiarrhythmic agents, patients will frequently have additional episodes of atrial fibrillation requiring either repeat external cardioversion or treatment with either pharmacologic or additional nonpharmacologic therapies. The limited long-term efficacy of different ...
Fromm R E RE - - 1997
INTRODUCTION: sudden cardiac death is an important cause of mortality in the United States today. A major determinant of survival from sudden cardiac death is rapid defibrillation. Communities with high rates of bystander cardiopulmonary resuscitation (CPR) and early defibrillation enjoy the highest survival rates from out-of-hospital cardiac arrest. First responders ...
Moss A J - - 1996
BACKGROUND: Unsustained ventricular tachycardia in patients with previous myocardial infarction and left ventricular dysfunction is associated with a two-year mortality rate of about 30 percent. We studied whether prophylactic therapy with an implanted cardioverter-defibrillator, as compared with conventional medical therapy, would improve survival in this high-risk group of patients. METHODS: ...
Bardy G H - - 1996
BACKGROUND: The most important factor for improving out-of-hospital ventricular fibrillation survival rates is early defibrillation. This can be achieved if small, lightweight, inexpensive automatic external defibrillators are widely disseminated. Because automatic external defibrillator size and cost are directly affected by defibrillation waveform shape and because of the favorable experience with ...
Carlson M D - - 1996
External electrical atrial defibrillation was developed in the early 1960s. Direct current electrical external shocks convert atrial fibrillation to sinus rhythm in the majority of patients. Although much has been learned about the mechanisms of the arrhythmia and those responsible for successful external direct current atrial defibrillation, the technique has ...
Venditti F J FJ - - 1996
BACKGROUND: Reports have demonstrated a circadian variation in the incidence of acute myocardial infarction, ventricular arrhythmias, and sudden cardiac death. We tested the hypothesis that a similar circadian variation exists for defibrillation energy requirements in humans. METHODS AND RESULTS: We reviewed the time of defibrillation threshold (DFT) measurements in 134 ...
Santini M - - 1996
New technologic development of implantable cardioverter-defibrillators (ICDs) keeps up with the exponential increase of their use for primary and secondary prevention of sudden cardiac death. The first-generation ICD with limited shock capability alone could be considered adequate in most cardiac arrest victims, but it was not suitable for sudden death ...
Capucci A - - 1996
In considering alternatives to the implantable cardioverter-defibrillator (ICD) in patients with malignant ventricular arrhythmias, both pharmacologic and nonpharmacologic therapies are available. Unfortunately, both pharmacologic methods (even when therapy is individualized and optimized) and nonpharmacologic methods (including coronary revascularization and radiofrequency or surgical ablation) yield long-term results that are unacceptable for ...
Heisel A - - 1996
Atrial fibrillation (AF), the most common arrhythmia resulting in hospital admission, is a major health problem. The limited efficacy of antiarrhythmic drugs to control this rhythm disorder and their potential proarrhythmic risk led to the development of new techniques to ameliorate the treatment of AF. Transvenous atrial defibrillation using endocardial ...
Auricchio A - - 1996
A major problem in patients with cardioverter-defibrillators is to determine reliably the mechanism for spontaneous implantable cardioverter-defibrillator (ICD) discharges. Electrogram storage in ICD devices is comparable to that in permanent Holter monitors. Stored bipolar electrograms obtained from the sensing or shocking lead system contain a wide variety of different information. ...
Ujhelyi M R - - 1996
Hypertonic saline solution may enhance cardiac conduction via the fast inward sodium channel and alter transmembrane Ca+2 conductance via the sodium-calcium exchanger. Evidence suggests that both Ca+2 conductance and myocardial conduction velocity may affect ventricular defibrillation. Since hypertonic saline solution solutions (ie, sodium bicarbonate) may be administered to patients who ...
Isbruch F M - - 1996
Adequate sensing is a basic requirement for appropriate therapy with ICDs. Integrated sense pace defibrillation leads, which facilitate ICD implantation, show a close proximity of sensing and defibrillation electrodes that might affect the sensing signal amplitude by the high currents of internal defibrillation. In 99 patients, we retrospectively examined two ...
Bardy G H - - 1996
OBJECTIVES: The purpose of this study was to prospectively examine in a multicenter study the methods of use, efficacy and complications of a unipolar cardioverter-defibrillator in patients at risk for sudden cardiac death. BACKGROUND: Implantation of cardioverter-defibrillators in the pectoral region offers a significant opportunity to improve the management of ...
Dunbar S B - - 1996
OBJECTIVE: To examine the relationships among personal factors (demographic variables and trait optimism); situational factors (ejection fraction, functional status, history of sudden cardiac arrest); coping and appraisal processes; and mood disturbance in patients hospitalized for recurrent ventricular dysrhythmia before the insertion of an implantable cardioverter defibrillator (ICD). DESIGN: Descriptive and ...
Le Tourneau T - - 1996
We report a case of pericardial constriction associated with defibrillator patches developing 4.5 years after implantation. This constriction was related to the presence of a large pericardial mass that had developed above the defibrillator patch. This mass, which had a calcified superior border, suggested former hematoma associated with pericardial fibrosis. ...
Jalife J - - 1996
Ventricular fibrillation is the most important cause of cardiac electrical instability leading to sudden death. Fibrillation is believed to be associated with complex three-dimensional (3-D) spatio-temporal patterns of electrical excitation of the myocardium. However, to this date, such patterns have not been directly observed or characterized, and little is known ...
Yu J C - - 1996
The aim of this study was to examine the effect of ventricular fibrillation and a subsequent defibrillation shock on ventricular excitability and refractoriness in human beings. We studied 16 consecutive patients with implantable cardioverter-defibrillators undergoing follow-up studies. The pre- and post-shock pacing threshold, ventricular effective refractory period, monophasic action potential ...
Fredman C S - - 1996
This report describes a modified defibrillation technique used successfully in a patient with an implanted epicardial cardioverter defibrillator who developed refractory ventricular fibrillation. During operative testing at the time of generator replacement, two episodes of intractable ventricular fibrillation were terminated by using a combined internal (epicardial)-external (transthoracic) defibrillation system that ...
Saksena S - - 1996
Implantable cardioverter-defibrillators (ICDs) are an important nonpharmacological option in the treatment of malignant ventricular arrhythmias. Technological advances in current devices permit nonthoracotomy implantation with transvenous lead systems using biphasic shocks. Decreasing device size has resulted in pectoral implantation. Battery longevity is still short in comparison with that of pacemakers. Lead ...
Krasna M J - - 1996
Nonthoracotomy lead systems have been developed to reduce the morbidity associated with cardioverter/defibrillator implantation. Total endocardial lead systems are effective in only about 50% of patients with standard monophasic waveforms; so patch placement is frequently required. We developed a new patch design and surgical techniques for thoracoscopic patch placement over ...
Sanders W E WE - - 1996
Third-generation implantable cardioverter defibrillators (ICD) are frequently implanted with nonthoracotomy systems and provide noninvasive methods for electrical stimulation and ventricular fibrillation induction. These modalities facilitate postoperative testing of the ICD. Rapid right ventricular burst pacing via the defibrillator is commonly used for initiation of ventricular tachyarrhythmias. However, with the available ...
Swerdlow C D - - 1996
OBJECTIVES: The goals of this study were to determine the probability of successful defibrillation at the upper limit of vulnerability and to evaluate a minimal safety margin for implantable cardioverter-defibrillator first shocks based solely on the upper limit of vulnerability. BACKGROUND: The upper limit of vulnerability is the strength at ...
Molina J E - - 1996
A series of 78 consecutive implants of the transvene PCD (Medtronic, Inc.) defibrillator system is presented and the occurrence of right ventricular perforation in 4 patients reported (5.2%). Diagnosis of perforation is made using four signs: (1) decrease in arterial blood pressure without any other explanation; (2) decrease in pulsatility ...
Saksena S - - 1996
Implantable defibrillation devices have now been extensively applied to patients requiring cardioversion and defibrillation of sustained ventricular tachyarrhythmias. The focus of new developments is in improving technology, achieving physiologic operation in the atrium and ventricle, seeking new indications and identifying patient populations amenable to this therapy. Ventricular application technology is ...
Cmolik B L - - 1996
Sustained atrial fibrillation is very common after cardiac surgical procedures. We hypothesized that atrial defibrillation could be accomplished consistently and safely by means of low-energy shocks delivered by temporary stainless steel wire electrodes placed at the time of the operation. Sterile pericarditis was created in five mongrel dogs (20.9 +/- ...
Stajduhar K C - - 1996
OBJECTIVES: This study was performed to determine the optimal position for the proximal electrode in a two-electrode transvenous defibrillation system. BACKGROUND: Minimizing the energy required to defibrillate the heart has several potential advantages. Despite the increased use of two-electrode transvenous defibrillation systems, the optimal position for the proximal electrode has ...
Curwin J H - - 1996
The diagnostic accuracy of implantable cardioverter defibrillators may be improved by automatically adjusting gain algorithms, which in general reduce the likelihood of oversensing while maintaining the ability to detect the low amplitude signals associated with ventricular fibrillation. We present a patient with a third-generation device who developed prolonged ventricular asystole ...
Gillis A M - - 1996
Since its initial application in 1980, the implantable cardioverter defibrillator (ICD) has evolved into a highly sophisticated device that offers programmable tiered therapy (antitachycardia pacing, cardioversion, and defibrillation) for ventricular tachyarrhythmias and backup pacing for bradycardia. It also provides diagnosis information about detected events. Successful implantation of nonthoracotomy systems is ...
Jung W - - 1995
Changes in the amplitude of endocardial electrograms after an unsuccessful shock attempt have been demonstrated to cause failure of redetection of ventricular fibrillation in patients using an integrated sense-pace defibrillating lead system. Thus, the objective of this study was to compare the effects of defibrillator shocks on the amplitude of ...
Runsiö M - - 1995
The implanted cardioverter defibrillator represents an alternative therapy for patients with drug-refractory malignant ventricular arrhythmias. Implantation and testing of the device requires that ventricular fibrillation be evoked and converted, thus providing a situation in which cardiovascular haemodynamics can be studied. In this study we have evaluated the effects of electrically ...
Michelson B I - - 1995
This study examines whether the current clinical practice of using a 5 mV minimum amplitude during normal sinus rhythm (NSR) ensures adequate detection during subsequent episodes of ventricular fibrillation (VF) at the time of the implantable cardioverter-defibrillator (ICD) threshold testing. Risk of nondetection occurs with ICDs when a substantial portion ...
Fotuhi P C - - 1995
BACKGROUND: In previous studies, epicardial patch electrodes decreased transthoracic defibrillation efficacy. We studied the effects of two inactive epicardial 14-cm2 titanium mesh patches on defibrillation energy requirements with nonthoracotomy internal lead configurations. METHODS AND RESULTS: A 6/6-millisecond biphasic shock wave-form was delivered via several electrode configurations 10 seconds after ventricular ...
Valen G - - 1995
Histamine has inotropic, chronotropic, arrhythmogenic, and vasoactive effects, and is released from the heart in ischaemia-reperfusion injury. The effect of ventricular fibrillation (VF) and defibrillation (DEF) on histamine release was investigated in 9 anaesthetized patients undergoing transvenous implantation of ICD. Concomitant arterial and coronary sinus (CS) blood samples were drawn ...
Epstein A E - - 1995
INTRODUCTION: Although myriad factors influence the defibrillation threshold, the relation between the site of transvenous lead entry into the vascular system and the defibrillation threshold has not been reported. This study examines the influence that venous entry site has on defibrillation success for a transvenous implantable cardioverter defibrillator lead with ...
Saksena S - - 1995
We undertook a prospective randomized clinical trial evaluating efficacy and safety of internal atrial defibrillation in patients with drug-refractory atrial fibrillation (AF). Consecutive patients with paroxysmal or chronic AF were randomly tested with 3 internal atrial defibrillation lead configurations and biphasic shocks. Patients with implanted cardiac pacemakers were tested with ...
KenKnight B H - - 1995
Defibrillation is thought to occur because of changes in the transmembrane potential that are caused by current flow through the heart tissue. Impedance to electric countershock is an important parameter because it is determined by the magnitude and distribution of the current that flows for a specific shock voltage. The ...
< 9 10 11 12 13 14 15 16 17 18 19 >