Clinical predictors of defibrillation thresholds with an active pectoral pulse generator lead system.

Active pectoral pulse generators are used routinely for initial ICD placement because they reduce DFTs and simplify the implantation procedure. Despite the common use of these systems, little is known regarding the clinical predictors of defibrillation efficacy with active pulse generator lead configurations. Such predictors would be helpful to identify patients likely to require higher output devices or more complicated implantations.

Temporal decline in defibrillation thresholds with an active pectoral lead system.

Objectives: The objective of this study was to characterize temporal changes in defibrillation thresholds (DFTs) after implantation with an active pectoral, dual-coil transvenous lead system.

Background: Ventricular DFTs rise over time when monophasic waveforms are used with non-thoracotomy lead systems. This effect is attenuated when biphasic waveforms are used with transvenous lead systems; however, significant increases in DFT still occur in a minority of patients.

Acute hemodynamic effects of right ventricular pacing site and pacing mode in patients with congestive heart failure secondary to either ischemic or idiopathic dilated cardiomyopathy.

The hemodynamic effects of pacing in patients with congestive heart failure (CHF) remain controversial. Early studies reported that pacing from the right ventricular (RV) apex improved acute hemodynamic parameters in patients with left ventricular systolic dysfunction, but these findings were not confirmed in subsequent controlled studies. More recently, it has been proposed that pacing from the RV side of the ventricular septum improves hemodynamic function compared with intrinsic conduction or apical pacing.

Optimization of transvenous coil position for active can defibrillation thresholds.

Introduction: Lead systems that include an active pectoral pulse generator are now standard for initial defibrillator implantations. However, the optimal transvenous lead system and coil location for such active can configurations are unknown. The purpose of this study was to evaluate the benefit and optimal position of a superior vena cava (SVC) coil on defibrillation thresholds with an active left pectoral pulse generator and right ventricular coil.

Atrial defibrillation with a transvenous lead: a randomized comparison of active can shocking pathways.

Objectives: The purpose of this study was to compare transvenous atrial defibrillation thresholds with lead configurations consisting of an active left pectoral electrode and either single or dual transvenous coils.

Background: Low atrial defibrillation thresholds are achieved using complex lead systems including coils in the coronary sinus. However, the efficacy of more simple ventricular defibrillation leads with active pectoral pulse generators to defibrillate atrial fibrillation (AF) is unknown.

Intravenous amiodarone suppression of electrical storm refractory to chronic oral amiodarone.

We report the case of an electrical storm in a cardiac arrest survivor with an ICD, in whom chronic oral amiodarone failed to suppress ventricular arrhythmias, and in whom intravenous amiodarone resulted in stability for 6 weeks prior to successful cardiac transplantation. Intravenous amiodarone can be successful in suppressing life-threatening ventricular arrhythmias, even when chronic oral amiodarone is unsuccessful.

A new defibrillator discrimination algorithm utilizing electrogram morphology analysis.

Inappropriate therapies delivered by implantable cardioverter defibrillators (ICDs) for supraventricular arrhythmias remain a common problem, particularly in the event of rapidly conducted atrial fibrillation or marked sinus tachycardia. The ability to differentiate between ventricular tachycardia and supraventricular arrhythmias is the major goal of discrimination algorithms. Therefore, we developed a new algorithm, SimDis, utilizing morphological features of the shocking electrograms.

The effect of shock configuration and delivered energy on defibrillation impedance.

Shock impedance is an important determinant of defibrillation efficacy. Lead configuration, shock polarity, and delivered energy can affect shock impedance, but these variables have not been studied in active can lead systems. The present study was a prospective evaluation of 25 patients undergoing initial transvenous defibrillator implantation.

Overdrive atrial pacing for conversion of atrial flutter: comparison of postoperative with nonpostoperative patients.

Background: Previous studies have reported varying success rates in overdrive pace termination of atrial flutter. We hypothesized that these discrepancies might be caused by differences in study populations. Accordingly, we prospectively compared the success rate of pacing in patients with atrial flutter that occurred after heart surgery with that of patients with atrial flutter from other causes.

Effect of shock polarity on biphasic defibrillation thresholds using an active pectoral lead system.

Introduction: The downsizing of implantable defibrillator pulse generators has made pectoral placement routine. A further reduction of defibrillation thresholds (DFTs) may simplify implantation defibrillation testing and allow for smaller, lower output pulse generators while maintaining an adequate defibrillation safety margin. One factor that may affect defibrillation efficacy is shock polarity.

Comparison of single- and dual-coil active pectoral defibrillation lead systems.

Objectives: The purpose of this study was to compare defibrillation thresholds with lead systems consisting of an active left pectoral electrode and either single or dual transvenous coils.

Background: Lead systems that include an active pectoral pulse generator reduce defibrillation thresholds and permit transvenous defibrillation in nearly all patients. A further improvement in defibrillation efficacy is desirable to allow for smaller pulse generators with a reduced maximal output.

Temporal stability of defibrillation thresholds with an active pectoral lead system.

Introduction: Monophasic defibrillation thresholds rise over time with a variety of lead systems. These chronic changes are attenuated or eliminated by biphasic waveforms, although the effect appears dependent upon the lead system. With the downsizing of pulse generator size to allow for routine pectoral implantation, active can lead systems have now become standard.

Effect of biphasic waveforms on transvenous defibrillation thresholds in patients with coronary artery disease.

This study is a prospective, randomized comparison of monophasic and biphasic defibrillation thresholds in 19 patients with a single transvenous lead. Despite using reverse polarity and optimal tilts for the monophasic waveform, the defibrillation threshold was reduced with biphasic shocks from 15.8 +/- 11.

Cardiac trauma. Diagnosis, management, and current therapy.

In cardiac trauma the two main mechanisms of injury are blunt and penetrating trauma. Common cardiac effects of trauma include myocardial rupture, contusion, laceration, pericardial insult, coronary injury, valvular damage, arrhythmias, and conduction abnormalities. Hemodynamic instability can develop rapidly and pose marked risk to patient survival.

Selective slow pathway ablation does not alter enhancement of vagal tone on sinus and atrioventricular nodal function.

We studied the effects of edrophonium on sinus cycle length, atrioventricular (AV) nodal fast pathway refractoriness, and AV nodal Wenckebach cycle length in 21 patients with AV nodal reentrant tachycardia (AVNRT) who received edrophonium, and 8 patients who received phenylephrine before and after selective slow pathway ablation. Changes in sinus cycle length, fast pathway conduction, and refractoriness were not altered by radiofrequency ablation of the slow pathway, suggesting that parasympathetic denervation does not occur after slow pathway ablation of AVNRT.

Dobutamine stress echocardiography predicts cardiac events in heart transplant patients.

Background: Cardiac transplantation is an accepted treatment modality for end-stage heart failure. Coronary artery disease remains a major cause of mortality in the long term after heart transplantation. Despite the high prevalence of coronary artery disease in heart transplant recipients, currently used noninvasive tests as well as invasive tests are highly unreliable in predicting prognosis.

Dobutamine stress-induced angina in patients with denervated cardiac transplants. Clinical and angiographic correlates.

Background: The clinical consequences of cardiac denervation include the inability of the heart transplant recipient to sense cardiac pain. This is due mainly to interruption of ventricular sympathetic afferents normally responsible for transmission of cardiac pain. Although angina has been reported in transplant recipients, to our knowledge, its temporal relationship to myocardial ischemia has not been previously demonstrated.