BACKGROUND Memory is a diverse biological phenomenon whose importance in the ventricle has been demonstrated. We hypothesized its occurrence in the atrium, contributing to the modulation of cardiac rhythm. METHODS AND RESULTS We analyzed P and Ta waves in conscious chronically instrumented dogs with complete heart block. Animals were atrioventricularly sequentially paced at 5% greater than th...

Radiotracer kinetics were used to evaluate the activity of the sympathetic nervous system in 10 patients who had had unstable ischaemic symptoms within the previous 12 weeks and 10 with stable angina. Patients with recent unstable angina or angina after recent acute myocardial infarction had higher basal cardiac noradrenaline spillover than patients with stable angina. This represents a selecti...

OBJECTIVES The contribution of nitric oxide (NO) and adenosine to the increase in coronary blood flow (CBF) induced by cardiac pacing was investigated in 28 subjects with angiographically normal coronary arteries with and without one or more risk factors for atherosclerosis. BACKGROUND NO and adenosine are important in the regulation of coronary circulation, and the inhibition of NO synthesis...

Twenty patients aged between 12 months and 13 years underwent permanent pacemaker implantation. The main indication for pacing was post-surgical atrioventricular block. The complication rate was high and related mainly to infections and lead system problems. The use of small multiprogrammable pacemakers is expected to reduce the reoperation rate for system malfunction and elective replacement. ...

Clinical trials. In the last two years, a number of landmark clinical trials have been published which further our understanding and clinical management of patients with atrial fibrillation (AF). Two of the major goals in the treatment of this condition include reducing progression or recurrence of the arrhythmia and decreasing the risk of cardiovascular events, thereby improving quality of lif...

Advances in pacemaker technology over the last 25 years have made cardiac pacing in infants and children a safe and practical therapy. Some of the technical challenges encountered with the first permanent pacemaker implantation in children during the early 1960s have been solved with miniaturized generators, lithium batteries, noninvasive programmability, and improved placement techniques. This...

The effects of atrial pacing on the cardiac balance of inorganic phosphate (Pi) were studied during control, atrial pacing, and recovery periods in 29 patients. Group A (n= 18) who had roentgenographically demonstrated coronary artery disease (CAD) developed angina during pacing, and showed mean myocardial lactate (L) production, abnormal left ventricular end-diastolic pressure (LVEDP) and ST s...

Pacemaker stimulation influences plasma levels of atrial natriuretic peptide (ANP). This study evaluated in individuals without impaired myocardial function whether a consecutive increase of pacing rates results in reduced alteration of plasma ANP levels mirroring a putative decrease of atrial contribution to cardiac output. In nine resting patients with DDD pacemakers, absolute and relative AN...

OBJECTIVE To determine the effects of ventricular pacing on the normal contraction sequence of the helical ventricular myocardial band, and its' impact on left ventricular function. METHODS Ten pigs (25-68 kg) underwent analysis of percent segmental shortening (%SS) by sonomicrometry, with crystals placed along the fiber orientation of the ascending and descending segments, and posterior LV w...

Cardiac alternans, a beat-to-beat alternation in action potential duration (at the cellular level) or in electrocardiogram morphology (at the whole heart level), is a marker of ventricular fibrillation, a fatal heart rhythm that kills hundreds of thousands of people in the United States each year. Investigating cardiac alternans may lead to a better understanding of the mechanisms of cardiac ar...