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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 ...
Ortiz J - - 1995
OBJECTIVES: This study sought to determine whether temporary epicardial wire electrodes can be used safely and effectively to defibrillate the atria with low energy shocks in the absence of anesthesia. BACKGROUND: Atrial fibrillation after open heart surgery is a significant clinical problem. METHODS: Twelve dogs with sterile pericarditis were studied. ...
Jones G K - - 1995
The purpose of this report is to review the gross and histological cardiac anatomical findings in patients with chronically indwelling coronary sinus leads at the time of autopsy or cardiac transplantation. Transvenous cardioverter defibrillators offer effective protection against sudden death. The use of a coronary sinus electrode has been shown ...
Hou C J - - 1995
BACKGROUND: This study was designed to characterize the ventricular vulnerable period (VVP) and ventricular fibrillation (VF) threshold by use of T-wave shocks in patients undergoing implantation of cardioverter/defibrillators. A premature condensed shock applied during the VVP can induce VF. Most studies on the VVP and VF threshold have been conducted ...
Marchlinski F E - - 1995
Implantable defibrillators have evolved from simple event counters to sophisticated diagnostic monitoring units capable of storing electrocardiographic information surrounding arrhythmia events and device therapy. In this review, the nature and characteristics of these stored electrocardiographic recordings are discussed and examples displayed. Potential benefits and limitation of stored electrogram analysis are ...
Barrington W W - - 1995
Pericardial constriction associated with the placement of intrapericardial defibrillator patches is a rare occurrence that is reported only one tenth as often in defibrillator patients as in patients undergoing other types of cardiac operations. Although this discrepancy may be attributable to a lower incidence of constriction with the defibrillator patch ...
Martin D T - - 1995
We have previously reported a chronic increase in defibrillation threshold in a non-thoracotomy implantable cardioverter-defibrillator (ICD) system using monophasic waveforms. To determine if this phenomenon is related to the lead system or the waveform used, we studied the chronic defibrillation threshold in consecutive patients receiving an ICD capable of delivering ...
Hillsley R E - - 1995
Due to the limited efficacy of antiarrhythmic drugs for atrial fibrillation, several nonpharmacologic therapeutic options have evolved. One of these is an implantable atrial defibrillator. Recent studies have shown that internal atrial defibrillation is feasible with relatively low energies. To date, the optimal electrode configuration involves large surface area catheters ...
Zaugg C E - - 1995
Increased intracellular calcium (calcium overload) is considered one of the factors that can initiate ventricular fibrillation. In addition, ventricular fibrillation itself can cause and possibly maintain calcium overload. The goal of this study was to determine whether the class IA antiarrhythmic agent procainamide can reduce calcium overload during ventricular fibrillation ...
Manoach M - - 1995
Ventricular fibrillation (VF) is one of the most life-threatening arrhythmias encountered in daily clinical practice. Its occurrence cannot be completely prevented by currently used antiarrhythmic drugs, and, in most instances, VF is sustained and leads to the patient's death unless a successful DC defibrillation is applied. However, spontaneous reversion of ...
Behrens S - - 1995
To determine the circadian variation of sustained ventricular tachyarrhythmias, 78 consecutive patients with an implanted cardioverter defibrillator were analyzed with regard to the occurrence of spontaneous shock episodes during a mean follow-up period of 18 +/- 12 months. In 39 patients 207 shock episodes that terminated potentially life-threatening ventricular tachyarrhythmias ...
Greene H L - - 1995
All transthoracic defibrillators on the US market use nominally monophasic shock waveforms. However, biphasic waveforms have a lower defibrillation threshold than monophasic waveforms for transthoracic defibrillation of animals and for defibrillation of humans by implantable cardioverter defibrillators. The relative efficacies of Edmark monophasic and Gurvich biphasic transthoracic cardioversion waveforms (200 ...
Hillsley R E - - 1995
INTRODUCTION: We hypothesized that drugs which alter ventricular refractoriness or excitability produce quantifiable changes in ventricular fibrillation. METHODS AND RESULTS: We used a 528-channel mapping system to quantify the effects of the beta-antagonist, propranolol, and the beta-agonist, isoproterenol, on activation patterns in ventricular fibrillation. A plaque of 506 (22 x ...
Raitt M H - - 1995
OBJECTIVES: The purpose of this study was to determine the relation between clinical variables and the defibrillation threshold by using a standardized testing protocol and a uniform implantable defibrillator system. BACKGROUND: Past studied have not revealed useful correlations between clinical variables and the energy required to terminate ventricular fibrillation. Most ...
Callihan R L - - 1995
OBJECTIVES: This study sought to assess the effect of passive "bystander" epicardial electrodes on defibrillation efficacy. BACKGROUND: We hypothesized that an inactive epicardial patch placed in an area of low potential gradient from an endocardial electrode shock might affect defibrillation efficacy through its effects on the shock field and the ...
Mogayzel C - - 1995
STUDY OBJECTIVE: To compare causes and outcomes of patients younger than 20 years with an initial rhythm of ventricular fibrillation versus asystole and pulseless electrical activity. DESIGN: Retrospective cohort study. SETTING: Urban/suburban prehospital system. PARTICIPANTS: Pulseless, nonbreathing patients less than 20 years who underwent out-of-hospital resuscitation. Patients with lividity or ...
Bardy G H - - 1995
BACKGROUND: Early defibrillation is the single most important factor for improving out-of-hospital ventricular fibrillation resuscitation rates. To achieve the earlier response times required for survival, typically < 6 minutes from time of collapse, it will be necessary to equip a far wider network of first responders (firefighters, police, and other ...
Wood M A - - 1995
OBJECTIVES: This study examined the temporal patterns of ventricular tachycardia detections by implantable cardioverter-defibrillators for circadian variability. BACKGROUND: Previous studies of circadian arrhythmia patterns have been methodologically limited by very brief observational periods. Late-generation implantable cardioverter-defibrillators accurately record the times of arrhythmia detections during unlimited follow-up. METHODS: Forty-three patients with ...
Markewitz A - - 1995
The optimal placement for the second defibrillation lead in a two-lead system has never been addressed. We retrospectively reviewed the data of 33 patients with an average age of 59.2 years (range 41-78 years), predominantly male (n = 29), who underwent implantation of a cardioverter defibrillator (ICD) for treatment of ...
Coumel P - - 1995
The technology of the implantable cardioverter defibrillator (ICD) offers the opportunity to overcome the present limits of the invasive and noninvasive approaches of clinical electrophysiology. The invasive approach enables us to reproduce severe arrhythmias if they are inducible, but does not give information concerning the way they spontaneously arise. The ...
Block M - - 1995
Defibrillation of the heart is achieved if an electrical current depolarizes the majority of the unsynchronized fibrillating myocardial cells. The applied current or the corresponding voltage described as a function of time is called the waveform. In pacing, to stimulate myocardial cells close to the electrode, a relatively low voltage ...
Haught W H - - 1995
Hemodynamically unstable ventricular arrhythmias induced during electrophysiologic testing almost always respond to prompt application of direct current transthoracic shocks. In rare cases, however, ventricular fibrillation may be refractory to conventional treatment. Recently, a technique of intracardiac defibrillation has been successfully used to resuscitate patients with ventricular fibrillation refractory to transthoracic ...
Berul C I - - 1995
OBJECTIVES: The purpose of this study was to prospectively evaluate postshock redetection of ventricular fibrillation by a system that coupled an implantable cardioverter-defibrillator with an automatic gain control sense amplifier and a transvenous lead system. BACKGROUND: Redetection of ventricular fibrillation after an unsuccessful first shock has not been systematically evaluated. ...
Lerman B B - - 1995
The duration of ventricular fibrillation (VF) that precedes a high energy shock has been recognized as a critical determinant of defibrillation outcome. Factors such as metabolic acidosis or alkalosis do not affect outcome. The authors hypothesized that release of myocardial adenosine during VF could potentially mediate the time-dependent effects of ...
Friedman P A - - 1995
Pacer-Cardioverter-Defibrillator. This article reviews the function of the pacer-cardioverter-defibrillator (PCD). Detection of ventricular arrhythmias occurs in two programmable zones, with onset and stability modifiers available to diminish overdetection of sinus tachycardia and atrial fibrillation, respectively. The sensing circuitry utilizes an auto-adjusting sensitivity with exponential decay to allow detection of low-amplitude ...
Luceri R M - - 1995
Ninety-three patients underwent implants of the Telectronics Model 4211 ICD attached to the Enguard PFX endocardial defibrillation lead system. Eighty-one males and 12 females ranging in age from 25-85 years (mean = 64). Coronary disease was the substrate in the majority (88%); mean left ventricular ejection fraction was 30%. VT ...
Thakur R K - - 1995
A nonthoracotomy surgical approach using an endocardial electrode and combined implantation of a subcutaneous patch and the implantable cardioverter defibrillator (ICD) generator in a subpectoral pocket has been described. We report the long-term follow-up results in patients undergoing implantation using this approach. The patient population consisted of 28 patients (22 ...
KenKnight B H - - 1995
OBJECTIVE: To assess the impact of epicardial patch electrode position on internal defibrillation efficacy. METHODS: Two mesh patch electrodes (13 cm2) were positioned on the epicardium of acute, isoflurane-anesthetized pigs (n = 7, 40-47 kg). Defibrillation efficacy was determined for three different patch positions: P1 = anterior-basal right ventricle (RV) ...
Ruiz E - - 1994
Among the factors involved in the induction, generalization, and reversion of cardiac fibrillation, the amount of tissue is a determinant factor. One question is whether an increase in myocardial mass would or would not require the same electrical threshold. Accordingly, one objective was to determine if ventricular weight (VW) has ...
Natale A - - 1994
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 ...
Martinez-Taboada V - - 1994
The prognosis of systemic sclerosis (SSc) is poor, and a significant number of patients suffer sudden death, probably related to malignant ventricular arrhythmias for which there is no reliable drug treatment. We describe a patient with SSc who had 2 documented episodes of ventricular fibrillation, that reverted after electrical defibrillation. ...
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