The tricuspid valve: an unusual site of endocardial pacemaker lead fracture.

Two patients are described in this article who developed fractures of transvenous endocardial pacing leads at the point of passage across the tricuspid valve. In one case life-threatening asystole occurred, emphasizing the potential seriousness of this complication.

Impedance changes during catheter ablation and their relationship to electrical arcing and clinical efficacy.

This study has used high energy ablative shocks in saline and in man to characterize the complex, energy dependent behavior of the impedance at the electrode-tissue interface. In vitro shocks showed a fall in impedance when an arc was formed, due to formation around the electrode of a vapor globe rendered conductive by the arc. Following arc extinction, this same vapor globe insulates the electrode, and subsequently collapses, forming a shock wave, and allowing current flow to resume.

Coronary venous aneurysms and accessory atrioventricular connections.

Histological investigation of a heart with aneurysmal malformation of the anterior cardiac vein showed atypical accessory atrioventricular pathways that could have been the basis for bypass tracts and ventricular pre-excitation. Review of other cases with coronary sinus or venous aneurysms showed a striking association with sudden death. Such malformations may not be as benign as previously thought.

Wolff-Parkinson-White syndrome: atrial fibrillation as the presenting arrhythmia.

Atrial fibrillation was identified as the initial arrhythmia complicating the Wolff-Parkinson-White syndrome in ten (9%) of 108 patients. Despite initially rapid ventricular responses in seven, long term survival and control of arrhythmia were excellent on medical treatment. Whereas symptom free patients with the pre-excitation syndrome who have additional underlying disease predisposing to atrial fibrillation may need detailed electrophysiological study, a more conservative approach is suitable for the typical symptom free individual.

Cryoablation of the accessory pathway in Wolff-Parkinson-White syndrome: initial results and long term follow up.

Cryoablation of the accessory pathway was used in the management of 20 patients with pre-excitation syndromes. All patients had presented with paroxysmal atrioventricular reentrant tachycardia; in addition, six had experienced atrial fibrillation. In 16 patients pre-excitation was overt and in four the accessory pathway was concealed.

Wolff-Parkinson-White syndrome: inadvertent permanent ablation of the accessory pathway during electrophysiological study.

A case of permanent unintentional ablation of an accessory pathway during electrophysiological study is reported. Possible factors predisposing to such ablation include the location and depth below the endocardium of the accessory pathway.

Latent pre-excitation: exposure of anterograde accessory pathway conduction during atrial fibrillation.

In three patients anterograde conduction across a previously undocumented accessory pathway was exposed by the development of atrial fibrillation. This unusual presentation illustrates the possible unmasking of the Wolff-Parkinson-White syndrome by other factors in patients who have not previously demonstrated the potential for anterograde accessory pathway conduction.

A comparison of bepridil with amiodarone in the treatment of established atrial fibrillation.

Fourteen patients with established atrial fibrillation (longer than three months) that was refractory to treatment were studied to compare the clinical and electrophysiological effects of amiodarone and bepridil. All patients initially received bepridil for three weeks (200-600 mg/day), followed by amiodarone for two to three months (100-400 mg/day). Bepridil seemed to be slightly more effective than amiodarone in converting the fibrillation to sinus rhythm (nine of fourteen compared with four of ten).

Cell-free detection and characterization of a novel nerve growth factor-activated protein kinase in PC12 cells.

We have developed a cell-free assay to detect and characterize nerve growth factor (NGF)-activated protein kinase activity. Cultured PC12 cells were briefly exposed to NGF, and extracts of these were assayed for phosphorylating activity using exogenously added tyrosine hydroxylase as substrate. Tyrosine hydroxylase was employed since it is an endogenous substrate of NGF-regulated kinase activity and is activated by phosphorylation.

Treatment of refractory supraventricular arrhythmias with flecainide acetate.

We treated 13 children aged 0.2 years to 15.7 years (median 7.

Rapid and safe termination of supraventricular tachycardia in children by adenosine.

Adenosine (0.05-0.25 mg/kg intravenously) successfully terminated resistant supraventricular tachycardia (SVT) in three seriously ill newborn infants and one older child.

A new low energy power source for catheter ablation.

The current technology in the area of catheter ablation for cardiac arrhythmia is limited by the amount of damage sustained by the ablated area in relationship to the energy used. Thus, a newly designed power source is described in this report in three patients, two with resistant atrial flutter/fibrillation and one with a reentrant AV tachycardia. The delivered energy in all patients was 5.

Right ventricular abnormalities in ventricular tachycardia of right ventricular origin: relation to electrophysiological abnormalities.

Patients with right ventricular tachycardia may have adverse electrophysiological abnormalities linked to disturbed right ventricular structure. Seventeen patients who presented with right ventricular tachycardia without coronary artery disease or gross abnormalities of left ventricular function were studied. Patients had the ventricular tachycardia characterised at electrophysiological study and most underwent radionuclide and contrast angiography.

Is the pulse in atrial fibrillation irregularly irregular?

The belief that there is total irregularity of the pulse in atrial fibrillation has been re-examined. In a computerised analysis of R-R intervals and pulse volumes, 100-500 (mean 237) consecutive cycles were examined in 74 patients with atrial fibrillation, of whom 36 were on digoxin and 38 were not taking any antiarrhythmic treatment. A Doppler ultrasound technique was used to assess pulse volumes, against which R-R intervals were correlated.

Echocardiographic measurement of the normal adult right ventricle.

In studies of the right ventricle the complexities of chamber shape may be overcome by use of multiple tomographic imaging planes. An established protocol for the echocardiographic description of the heart was used to examine the right ventricle in an ordered series of transducer locations and orientations. Diastolic measurements were made of the right ventricular inflow tract, outflow tract, and right ventricular body, and the range and reproducibility of normal values for cavity size and right ventricular free wall thickness were established.

The plasma atrial natriuretic peptide response to treatment of acute cardiac failure, spontaneous supraventricular tachycardia and induced re-entrant tachycardia in man.

Patients with acute congestive cardiac failure had elevated plasma concentrations of atrial natriuretic peptide (ANP) which fell towards normal levels with successful diuretic therapy. The plasma ANP concentration was closely correlated with the clinical condition of the patients as assessed by serial clinical measurement of the jugular venous pressure and body weight. Plasma ANP concentrations were also raised in patients with a spontaneous acute onset of supraventricular tachycardia but to a lesser extent in patients with chronic tachycardia.

Electrophysiologic and antiarrhythmic actions of bepridil. Comparison with verapamil and ajmaline for atrioventricular reentrant tachycardia.

Bepridil (2 mg/kg intravenously) was given to 20 patients with atrioventricular (AV) reentrant tachycardia and its effects were compared with those of verapamil (0.15 mg/kg intravenously) in 8 patients and ajmaline (0.75 mg/kg intravenously) in 12.