INTRODUCTION The purpose of this study was to evaluate the effects of an acute increase in atrial pressure on refractoriness (mechanoelectrical feedback) and the vulnerability to atrial fibrillation (AF) and to investigate the effects of autonomic blockade and verapamil on mechanoelectrical feedback in humans. METHODS AND RESULTS Right atrial pressure and effective refractory period (ERP) at ...

A 52-year-old woman with a history of multiple episodes of paroxysmal supraventricular tachycardia underwent electrophysiologic studies and a catheter ablation procedure. The 12-lead electrocardiogram during tachycardia showed a long RP tachycardia with negative P waves in leads II, III, and aVF. At baseline, dual atrioventricular (AV) and ventriculoatrial (VA) nodal conduction was elicited by ...

OBJECTIVES This study assessed the effects of inhibition of nitric oxide synthesis on epicardial human coronary arteries and on coronary flow velocity during baseline conditions and during atrial pacing. BACKGROUND Epicardial coronary artery dilation occurs in response to an increase in heart rate. It is not known whether the dilation of both angiographically normal and diseased epicardial co...

A 76-year-old man underwent implantation of a model 5386 Identity ADx XL DR pacemaker (St. Jude Medical, Sylmar, CA, USA) for intermittent, high-degree atrioventricular (AV) block. A model 4480 passive bipolar lead (St. Jude) was placed in the right atrial appendage, and a model 1688T active fixation lead (St. Jude) was placed on the right ventricular midseptum. The device was programmed in DDD...

OBJECTIVE To evaluate the incidence of intraoperative and early postoperative complications (up to two months after implant) of endocardial permanent pacemaker insertion in all patients under-going a first implant at a referral centre. METHODS Prospective evaluation of all endocardial pacemaker implantation procedures performed from April 1992 to January 1994 carried out by completion of stan...

SUMMARY The hemodynamic effects of atrial pacing were evaluated in a group of 19 patients soon after cardiac valve surgery. Atrial pacing at 30 beats/min above the control rate of 88 beats/min produced an increase in cardiac index of 600 ml/min/m2. Isoproterenol was infused into eight of these patients to produce an increment in heart rate identical to that during atrial pacing. In these patien...

AIMS Endocardial (ENDO) or epicardial (EPI) pacing systems are implanted in infants but it remains unclear which system should be preferred. METHODS AND RESULTS We evaluated the results of children <or=1 year who underwent pacemaker (PM) implantation at our centre with a retrospective analysis. Between 1992 and 2004, 56 patients, 37 of whom had other congenital heart defects (CHDs), received ...

BACKGROUND In five chronically instrumented conscious dogs, we studied the effects of rapid pacing on sustained electrically induced atrial fibrillation. METHODS AND RESULTS Twenty-three unipolar atrial electrograms were recorded simultaneously from the bundle of Bachmann and the lateral wall of the right and left atria. During sustained atrial fibrillation, the surface electrocardiogram show...

INTRODUCTION Standard electrophysiologic techniques generally allow discrimination among mechanisms of paroxysmal supraventricular tachycardia. The purpose of this study was to determine whether the response of paroxysmal supraventricular tachycardia to atrial and ventricular overdrive pacing can help determine the tachycardia mechanism. METHODS AND RESULTS Fifty-three patients with paroxysma...