Efficacy and Safety of Rate Responsive Pacing in Patients with Coronary Artery Disease and Angina Pectoris

The present study included 17 patients with angina pectoris and coronary artery disease in whom a rate responsive ventricular pacemaker (Medtronic Activitrax) had been implanted. All patients had an exclusively paced rhythm. Single blinded, random, cross-over treadmill tests in the rate responsive pacing mode (VVIR) and in the fixed-rate demand mode (VVI) were performed, with an interval of 4-6 weeks. Mean exercise duration increased by 25% during VVIR pacing. Maximal heart rate increased significantly during VVIR compared to VVI pacing (VVI = 74 +/- 2 bpm, VVIR = 116 +/- 8 bpm, P less than 0.001) as did the rate-pressure product (VVI = 10.850 +/- 1,124, VVIR = 16.628 +/- 2,110, P less than 0.001). Despite improved performance, the number of anginal attacks per week and the nitroglycerin consumption did not show a significant difference between the two pacing modes. It is concluded that rate responsive pacing is beneficial and safe in patients with angina pectoris and coronary artery disease.     

Endothelial cell dysfunction in homocystinuria

Abstract. This report describes the isolation and culture of venous endothelial cells from the umbilical cord of an obligate heterozygote for homocystinuria. The effect of different sulphur-containing amino acids on the viability and function of these cells was studied and compared with cultured normal endothelial cells. When endothelial cells were cultured in the presence of methionine (10 mmol/l) or homocystine (10 mmol/l), differences occurred between the viability and function of the heterozygote and normal cells in terms of ⁵¹Cr release and ability to prevent platelet adherence. The Cr release corrected for spontaneous release increases for the heterozygote cells after incubation for 21 h in the presence of methionine to 81.3% (control cells, range: 0–23.3%, n = 5) and in the presence of homocystine to 141% (control cells, range: 13.5–55.2%, n = 5). The total number of platelets that adhere to confluent monolayers increases for heterozygote cells cultured in the presence of methionine to 0.98 ± 10⁷ platelets cm^-2 (normal cells, range: 0.56–0.72 ± 10⁷ platelets cm^-2) and in the presence of homocystine to 1.41 ± 10⁷ platelets cm^-2 (normal cells, range: 0.94–1±06 ± 10⁷ platelets cm^-2). Both normal and control cells were sensitive to homocysteine. This study indicates for the first time what vascular endothelial cells, derived from an obligate heterozygote, are (partly) deficient in cysthathionine synthase and are more susceptible to methionine- and homocystine-mediated injury than normal endothelial cells. Consequently, in homocystinuria, due to dysfunction of the endothelial cells, toxic sulphur-containing amino acids may accumulate in these cells, causing injury of these cells.     

Moving from hospital into a care home – the nurse's role in supporting older people

• ? Discharge planning has received much attention in the nursing literature over the past few years, and there has been particular concern over the discharge of older people back into their domestic environment.
• ? The practical and logistical problems of managing such a discharge are considerable, but in this paper we argue that discharging older people from hospital to care homes is equally problematic, though in different ways.
• ? This is a neglected area of research, perhaps because discharge into a care home seems to present fewer organizational problems.
• ? There is, however, an extensive body of literature from a range of different disciplines which suggests that the loss of home and entry into a strange environment can be very stressful.
• ? This paper outlines this literature and explores the implications for nursing practice.

     

Long-Term Follow-Up After Right Atrial Radiofrequency Catheter Treatment of Paroxysmal Atrial Fibrillation

Catheter ablation of paroxysmal atrial fibrillation using long linear lesions in the right atrium is still under investigation, and its long-term follow-up is unknown. Methods: Thirty-six men and nine women (aged 51 ± 12 years) with symptomatic daily episodes of AF for 6 ± 5 years despite the use of 4.7 ± 1.5 antiarrhythmic drugs were studied between July 1994 and January 1996. Progressively longer ablation lines were performed in 3 groups of 15 consecutive patients each, using a 14-electrode catheter or a single-electrode dragging technique. Success was defined as atrial fibrillation elimination or recurrence for no longer than 6 hours over 3 months of observation. Patients who had fewer than 6 hours of atrial fibrillation per month were considered "improved." Medium- (11 ± 4 months) and long-term (26 ± 5 months) results were assessed clinically from a patient's diary and from Holter recordings. Results: After a follow-up of 11 months, 24 patients had a favorable result of the ablation procedure with or without additional antiarrhythmic drug therapy, representing 53% of the original cohort. After 26 ± 5 months of follow-up, these successful results were reduced to 17 patients (37%). Conclusions: After linear atrial ablation, a significant long-term attrition of arrhythmia-free patients was observed. This may be due to a combination of disease progression, incomplete linear block, and ineffective ablation of arrhythmogenic triggers.     

Incidence and Prevention of Cardiac Tamponade Complicating Ablation for Atrial Fibrillation

Cardiac tamponade complicating catheter ablation of atrial fibrillation (AF) occurs in approximately 1% of pulmonary vein isolation (PVI), and up to 6% of linear ablation procedures. We reviewed 348 consecutive AF ablation (including repeat) procedures over 1 year, which all included PVI, with additional linear lesions at the mitral isthmus in 73%, and cavotricuspid isthmus (CTI) in 76%. An irrigated-tip ablation catheter was used, with power limited to 25–35 W for PVI and 45–60 W for linear lesions. Tamponade occurred in seven men and three women (2.9% of the population) during the creation of linear ablation lesions. Mechanical perforations occurred in two patients, and "popping" during radiofrequency (RF) energy delivery at the mitral isthmus in six, and at the CTI in two patients. Peak RF power was significantly higher in patients with than without tamponade (53 ± 4 W vs 48 ± 7 W; P = 0.02), and was greater than 48 W in all cases of "popping." In the following year, RF power for linear ablation was limited to ≤42 W. Among 398 procedures, tamponade occurred in four patients (1.0%; P = 0.047 vs first year), three from "popping" and one from mechanical trauma. Procedural success rate remained the same despite reduction of power. Risk of tamponade was highest during linear ablation, mainly associated with high energy delivery and "popping." Reducing the energy limited, though did not eliminate this complication.     

Long-term Prevention of Vagal Atrial Arrhythmias by Atrial Pacing at 90/Minute: Experience with 6 Cases

Six patients (5 men, 1 woman) with a history ranging from 3–16 years of resistant vagal atrial arrhythmias were treated by atrial pacing at a rate of 90Jmin. These patients have been followed up for an average of 5.5 years (range 2–11 years) with favorable resutls. The arrhythmias were charactemed by daily or weekly attacks of rypical alrial flutter and atrial fibrillalion occurring mainly or exclusively at night, at rest, or in the digestive periods in otherwise normal hearts of middle-aged palients (first attack between 25 and 54, mean 40). The arrhythmias werc resistant to quinidinc, and were usually aggravated by digitalis, beta-blockers and verapamil. Amiodaroneisusually the only effective drug in this syndrome, but was not used before pacing in the 2 first cases, and was in effective in the other 4 cases. Electrophysiologic studies confirmed the absence of sick sinus syndrome, and the close relationship betwecn a relative bradycardia and the onset of the arrhythmia. Atrial pacing alone totally controiled the arrhythmia in 1 palient; amiodarone was used in conjunction with pacing in 3 palients. In 1 patient the improvement was clear but incomplete, and in 1 patient permanent alrial fibrillation occurred shortly afler pacemaker implantalion.     

Circadian Variations in Minute Ventilation Can Be Reproduced by a Pacemaker Sensor

Special software allowing the memorization of 24-hour minute ventilation can be loaded into the memoiy of the Chorus RM, a DDDR pacemaker driven by minute ventilation. This feature was tested in the postimplant period in 13 patients. Measurements of minute ventiiation, respiratory rate, and respiratory amplitude were analyzed according to prospectively defined diurnal and nocturnal time periods. Minute ventilation decreased by 39% (P < 0.001) from the diurnal to the nocturnal phase, while respiratory rate and amplitude decreased by 18% and 28%, respectively (P < 0.001 each). Thus, minute ventilation allowed discrimination between sleep and waking hours. This information could be utilized to modulate the backup rate of the pacemaker.     

Sino-Atrial Dissociation: Evidence by Intracardiac Recordings in Man and by Microelectrode Studies on Isolated Rabbit Atrium

The electrophysiologic mechanisms of sinus dysfunction have recently been determined by direct recordings of the sinus node electrogram. The association of various degrees of abnormalities in the formation of the impulse within the sinus node and of sinoatrial conduction block, represents the pathophysiological substrate of the mechanism of sinus node dysfunction. The purpose of this work is to present clinical and experimental data supporting the concept of sinus node isolation. In our clinical case, the sinus node was probably intact despite aspects of sinus node dysfunction on the surface ECG. Sinus node electrograms were recorded with a sinoatrial conduction time of 100 ms (normal values in our laboratory: 83 ms +/- 38 ms). Atrial mapping demonstrated that the area depolarized by the sinus node involved a 2 cm2 zone surrounding it. This perisinusal activity could not be recorded on the surface ECG. Both exit and entry blocks in the sinus node were demonstrated. Our experimental data showed a total desynchronization between the electrical activity of the sinus node and that of the atrium under hypoxic conditions. Both types of cases demonstrated that an atrial dysrhythmia was coexisting with regular sinus activity. From these data we concluded that a sinus node free from any pathological involvement could be associated with severe symptoms of sinus node dysfunction on the surface ECG.     

The Effect of Age on the Electrophysiological and Autonomic Correlates of Sudden Death After Acute Myocardial Infarction

To examine the influence of age on the autonomic and electrophysiological correlates of sudden death after myocardial infarction, 223 patients aged <60 and 195 patients aged ≥60 were followed up for a mean of 790 days. The patients had Holter monitoring and a signal-averaged EGG 5–11 days after infarction. A mean ventricular ectopic beat frequency >10 beats/ hour (VE10) was present in 17.0% of young versus 28.2% of old patients (P < 0.01); a low heart heart variability index in 17.9% of young but in 32.3% of old patients (P < 0.001) and late potentials in 17.5% but 32% of young and old patients, respectively (P < 0.01). There was no difference in the incidence of sudden death between young and old patients (3.6% vs 3.1%). However, sudden death accounted for 50%, compared with 24% of all deaths in the young and old groups, respectively (P < 0.01). Sudden death was more closely associated with low heart rate variability and VE10 in the young than in the older group. The predictive values of a heart rate variability index <20 units with VE10 in younger patients were a sensitivity of 50%, a positive predictive accuracy (PPA) of 33% and risk ratio (RR) of 18 (P < 0.001); these values did not reach significance in older patients (16.7%, 4.3% and 1.4%, respectively.) Late potentials had a sensitivity of 50%, a PPA of 12.1%, and an RR of 4.7 in young patients (P < 0.05): the corresponding values in the older group were 80%, 8.9, and 8.4 (P < 0.02). It is concluded that sudden death is a more predominant mode of death and is more strongly associated with lower heart rate variability and with the VE10 incidence in young than in older postinfarction patients. Age should be taken into account when assessing the risk of sudden death after myocardial infarction.