The Australian and New Zealand cardiac pacing and implantable cardioverter-defibrillator survey: calendar year 1997.

BACKGROUND: A comprehensive pacemaker (PM) and implantable cardioverter-defibrillator (ICD) survey was undertaken in Australia (Aus) and New Zealand (NZ) for calendar year 1997. RESULTS: Compared to the 1993 survey, significant increases in implantation numbers were recorded. For 1997, the total new PM implanted was 6,405 Aus (3,834 in 1993) and 823 NZ (530 in 1993). The number of new pacemaker implants per million population was 345 Aus (216 in 1993) and 228 NZ (150 in 1993). Implantation centres increased between surveys from 49 to 92 in Aus and from seven to eight in NZ. There were smaller increases in pacemaker replacements between surveys with 735 in Aus (700 in 1993) and 126 in NZ (82 in 1993). In both countries, pacemaker implants were performed predominantly by non-surgeons. New recipients aged > 80 years were approximately 25% Aus and 30% NZ. The predominant indications were high degree atrio-ventricular block and sick-sinus syndrome in both Aus and NZ. Dual chamber implants were 65% Aus and 55% NZ. The median hospital stay was about 2 days in Aus and 1 day in NZ. Pacing leads were overwhelmingly transvenous, bipolar and tined in both chambers. They were inserted via a cephalic vein cutdown in approximately 40% of cases in Aus and 49% in NZ. For ICD, the implants were 449 Aus (180 in 1993) and 31 NZ (10 in 1993) with new implants per million population being 24 Aus and eight NZ. A breakdown of data for the six Aus States is presented.

The World Survey of Cardiac Pacing and Cardioverter Defibrillators: calendar year 1997--Asian Pacific, Middle East, South America, and Canada.

A comprehensive cardiac pacing and ICD survey of the Asian Pacific region, Middle East, South America, and Canada was undertaken for calendar year 1997. Thirteen countries in the Asian Pacific region contributed to the survey. There were also two countries from the Middle East, three from South America, and Canada. Accurate numbers of new implants and replacements were obtained for cardiac pacemakers. In the Asian Pacific region, Japan with almost 20,000 implants, had the largest number of pacemaker implants, but Australia had the highest implant rate with 345 new implants per million population. However, Canada and Uruguay had higher new implant rates per million. The major indication for implantation of a cardiac pacemaker was high degree atrioventricular block. There was a high incidence of single chamber ventricular pacing in the developing countries of Asia. Only a few countries used substantial numbers of single lead VDD and AAIR pacing systems. Pacing leads were predominantly transvenous, bipolar, passive fixation, and steroid eluting. Active-fixation leads were also used in the atrium. With ICD use, Australia had the highest new implant rate per million population. The major indications were sudden death and ventricular arrhythmias. A group of enthusiastic survey coordinators has now been established. It is hoped to continue physician and country recruitment, particularly in the Middle East and South American regions to establish a fully global experience of cardiac pacing and ICD use.

Dual demand pacing using retriggerable refractory periods for ventricular rate control during paroxysmal supraventricular tachyarrhythmias in patients with dual chamber pacemakers.

The use of dual chamber pacing in patients with atrioventricular block and paroxysmal supraventricular tachyarrhythmias may present a clinical dilemma because of the rapid and erratic triggering of ventricular pacing. To avoid this, a variety of pacing methods have now been described, including the use of retriggerable atrial refractory periods or dual demand pacing. This review details the use, advantages, and limitations of this poorly understood algorithm referred to as "pseudo-mode switching."

Electrical remodeling of the atria following loss of atrioventricular synchrony: a long-term study in humans.

BACKGROUND: Evidence suggests that an increased incidence of atrial fibrillation occurs in patients undergoing single-chamber ventricular pacing (VVI) when compared with those undergoing single-chamber atrial pacing (AAI) or those having dual-chamber atrioventricular pacing (DDD). The mechanism for this is unknown. We hypothesized that long-term loss of atrioventricular (AV) synchrony leads to atrial electrical remodeling: a potential explanation for this difference. METHODS AND RESULTS: The study was a prospective, randomized comparison between 18 patients paced in VVI mode and 12 patients paced in DDD mode for 3 months. Under autonomic blockade, effective refractory periods (ERPs) from the lateral right atrium (RA), RA appendage, RA septum, and coronary sinus-corrected sinus node recovery times (cSNRTs), as well as P-wave duration (PWD), and biatrial diameters were measured at baseline and 3 months. The VVI group was then programmed to DDD pacing and reevaluated after a further 3 months. After long-term VVI pacing, ERPs at all 4 atrial sites increased significantly in a nonuniform fashion in association with biatrial dilatation. PWD and cSNRTs also prolonged significantly. With the reestablishment of AV synchrony, ERPs, PWD, cSNRTs, and biatrial dimensions returned to baseline levels. In the 12 patients who underwent long-term DDD pacing from baseline, no significant changes in atrial electrophysiology or biatrial dimensions were demonstrated. CONCLUSIONS: Long-term loss of AV synchrony induced by VVI pacing is associated with atrial electrical remodeling, which is reversible after the reestablishment of AV synchrony with DDD pacing. This process may be partly responsible for the higher incidence of atrial fibrillation in patients undergoing VVI pacing compared with AV sequential pacing.

Mechanical remodeling of the left atrium after loss of atrioventricular synchrony. A long-term study in humans.

BACKGROUND: Tachycardia-mediated mechanical remodeling of the atrium is considered central to the pathogenesis of thromboembolism associated with chronic atrial fibrillation. Whether atrial mechanical remodeling also occurs in response to atrial stretch induced by chronic asynchronous ventricular pacing in patients with permanent pacemakers is unknown. METHODS AND RESULTS: The study design was a prospective randomized comparison between 21 patients paced chronically in the VVI mode and 11 patients paced chronically in the DDD mode for 3 months. Left atrial appendage (LAA) function and the presence of spontaneous echo contrast (SEC) were determined with transesophageal echocardiography (TEE) within 24 hours of pacemaker implantation and after 3 months. The VVI patients were then programmed to DDD and underwent a third TEE after DDD pacing for an additional 3 months. After chronic VVI pacing, LAA velocity decreased from 82.4+/-29.0 to 42.1+/-25.4 cm/s (P<0.01), LAA fractional area change decreased from 74.9+/-17.2% to 49.8+/-22.0% (P<0.01), and 4 patients (19%) developed left atrial SEC (P<0.05). With the reestablishment of chronic AV synchrony, LAA velocity increased to 61.6+/-18.5 cm/s (P<0.01), LAA fractional area change increased to 76.4+/-18.1% (P<0.01), and SEC resolved. In the 11 patients undergoing chronic DDD pacing, no significant changes in LAA velocity (baseline, 86.0+/-28.8 cm/s versus 3 months, 79.6+/-14. 9 cm/s) or LAA fractional area change (baseline, 76.2+/-19.4% versus 72.5+/-15.7%) were demonstrated, and SEC did not develop. CONCLUSIONS: Chronic loss of AV synchrony induced by VVI pacing is associated with mechanical remodeling of the left atrium, which may reverse after the reestablishment of AV synchrony with DDD pacing. This process may be partly responsible for the higher incidence of thromboembolism observed in patients undergoing VVI pacing compared with AV sequential pacing.

Left atrial mechanical function after brief duration atrial fibrillation.

OBJECTIVES: This study examined the effect of brief duration atrial fibrillation on left atrial and left atrial appendage mechanical function in humans with structural heart disease. BACKGROUND: Left atrial dysfunction and the development of spontaneous echo contrast (SEC) may follow the cardioversion of atrial fibrillation (AF) to sinus rhythm. This phenomenon has been termed "stunning" and is implicated in the development of atrial thrombus and embolic stroke. The effects of brief duration AF on left atrial mechanical function in humans are unknown. METHODS: Twenty-four patients (23 men, aged 59.1+/-12.7 years) with significant structural heart disease (ejection fraction 31.2+/-9.0%, left atrial diameter 4.9+/-0.4 cm) undergoing implantation of a ventricular cardiodefibrillator underwent transesophageal echocardiography to evaluate left atrial appendage emptying velocities (LAAeV) and SEC before, during and after a 15-min period of AF induced by rapid right atrial pacing. Atrial fibrillation was then permitted to terminate spontaneously within 5 min or was reverted with an endocardial direct current shock. Velocities and SEC were assessed in sinus rhythm pre-AF, during AF and immediately, 5 and 10 min after reversion to sinus rhythm. RESULTS: Atrial fibrillation terminated spontaneously in 10 patients after 16.1+/-1.0 min. Endocardial direct current (DC) cardioversion of 10.4+/-6.4 J was required in 14 patients after AF lasting 20 min. Mean LAAeV pre-AF (50.0 +/- 17.5 cm/s) was not significantly different to LAAeV immediately (52.8 +/- 16.7 cm/s), 5 min (54.3 +/- 16.4 cm/s) or 10 min (53.7 +/- 15.7 cm/s) after reversion to sinus rhythm. Atrial stunning defined as a reduction in LAAeV of >20% was not observed in any patient. Fourteen of 24 patients (58%) developed SEC during AF, which resolved within 30 s of AF termination. There were no significant differences between LAAeV in those patients reverting with DC shock (pre-AF 50.6+/-16.2 cm/s vs. immediately post-AF 54.7+/-16.6 cm/s) or in those patients with spontaneous reversion (pre-AF 48.9+/-20.2 cm/s vs. immediately post-AF 49.8+/-17.3 cm/s). CONCLUSIONS: Significant left atrial stunning was not observed after brief duration AF in humans with structural heart disease. Transient left atrial SEC develops in a significant proportion of these patients during AF but resolves rapidly on reversion to sinus rhythm. These findings suggest that the risk of thromboembolism may be low after brief duration AF that terminates either spontaneously or with an endocardial DC shock even in patients with significant structural heart disease. These findings have important implications for recipients of implantable devices that are capable of atrial defibrillation in response to AF.

Left atrial "stunning" following radiofrequency catheter ablation of chronic atrial flutter.

OBJECTIVES: This study examined the effect of radiofrequency ablation (RFA) on left atrial (LA) and left atrial appendage (LAA) function in humans with chronic atrial flutter (AFL). BACKGROUND: Atrial stunning and the development of spontaneous echocardiographic contrast (SEC) is a consequence of electrical cardioversion of AFL to sinus rhythm. This phenomenon has been termed "stunning" and is associated with thrombus formation and embolic stroke. Radiofrequency ablation is now considered to be definitive treatment for chronic AFL, but whether this procedure is complicated by LA stunning is unknown. METHODS: Fifteen patients with chronic AFL undergoing curative RFA underwent transesophageal echocardiography to evaluate LA and LAA function and SEC before and immediately, 30 minutes and 3 weeks after RFA. To control for possible direct effects of RFA on atrial function, seven patients undergoing RFA for paroxysmal AFL were also studied. In this group, RF energy was delivered in sinus rhythm and echocardiographic parameters were assessed before and immediately and 30 minutes following RFA. RESULTS: Chronic AFL: Mean arrhythmia duration was 17.2 +/- 13.3 months. Twelve patients (80%) developed SEC following RF energy application and reversion to sinus rhythm. LAA velocities decreased significantly from 54.0 +/- 14.2 cm/s in AFL to 18.0 +/- 7.1 cm/s in sinus rhythm after arrhythmia termination (p < 0.01). These changes persisted for 30 minutes. Following 3 weeks of sustained sinus rhythm, significant improvements in LAA velocities (68.9 +/- 23.6 vs. 18.0 +/- 7.1 cm/s, p < 0.01) and mitral A-wave velocities (49.8 +/- 10.3 vs. 13.4 +/- 11.2 cm/s, p < 0.01) were evident and SEC had resolved in all patients. Paroxysmal AFL: Radiofrequency energy delivered in sinus rhythm had no significant effect on any of the above indexes of LA or LAA function and no patient developed SEC following RFA. CONCLUSIONS: Radiofrequency ablation of chronic AFL is associated with significant LA stunning and the development of SEC. Left atrial stunning is not secondary to the RF energy application itself. Sustained sinus rhythm for 3 weeks leads to resolution of these acute phenomena. Left atrial stunning occurs in the absence of direct current shock or antiarrhythmic drugs, suggesting that its mechanism may be a function of the preceding arrhythmia rather than the mode of reversion.

Atrial fibrillation and anticoagulation in patients with permanent pacemakers: implications for stroke prevention.

Several large prospective randomized trials have demonstrated that anticoagulation with warfarin reduces the risk of thromboembolic stroke in high risk patients with chronic AF by approximately 70%. Large numbers of patients with permanent pacemakers have AF, and anticoagulation rates in this population have not been described. In a prospective analysis of 110 consecutive patients attending the pacemaker clinic of a large university hospital we assessed the number of patients with AF and the proportion of these patients who were receiving anticoagulation to prevent thromboembolic stroke. Where necessary, temporary pacemaker reprogramming to low ventricular rates was utilized to facilitate the diagnosis of AF. Fifty-three of the 110 patients (48%) were diagnosed with AF, all of whom (100%) had accepted high risk factors for thromboembolic stroke. Only eight of the 53 (15%) had been anticoagulated with warfarin. Thirty-six of the 53 patients (68%) diagnosed with AF had no prior documented diagnosis of chronic AF, and the majority had no symptoms suggesting AF. A single lead II ECG was insufficient in 67 of the 110 patients (61%) to diagnose the underlying atrial rhythm; the remainder required 12-lead ECGs or temporary pacemaker reprogramming to low ventricular rates to diagnose the underlying atrial rhythm. AF is common in patients with permanent pacemakers. It is commonly asymptomatic, and anticoagulation is markedly underutilized in reducing stroke risk in these patients. Attention to the possibility of AF in paced patients should allow prompt diagnosis and allow both the initiation of anticoagulation in order to reduce thromboembolic stroke risk and consideration for cardioversion of AF to sinus rhythm.

Effect of direct current shocks on left atrial mechanical function in patients with structural heart disease.

OBJECTIVES: This study examined the effect of endocardial and transthoracic direct current (DC) shocks on left atrial and left atrial appendage function in humans with structural heart disease. BACKGROUND: DC cardioversion of atrial fibrillation (AF) to sinus rhythm is associated with transient left atrial and left atrial appendage dysfunction and the development of spontaneous echo contrast (SEC). This phenomenon has been termed atrial "stunning" and may be associated with thrombus formation and embolic stroke. To what extent the shock itself contributes to atrial stunning is unclear. METHODS: Thirteen patients in sinus rhythm undergoing implantation of a ventricular implantable cardioverter defibrillator (ICD) were prospectively evaluated. All patients had significant structural heart disease. To evaluate the effects of DC shocks on left atrial and left atrial appendage function, biphasic R wave synchronized endocardial shocks of 1, 10 and 20 J were delivered between the right ventricular electrode and the left pectoral generator of the ICD in sinus rhythm. R wave synchronized transthoracic shocks of 360 J were also delivered between anteriorly and posteriorly positioned chest electrodes. Transesophageal echocardiography was performed to evaluate left atrial appendage velocities, mitral inflow velocities and the presence of SEC before and immediately after each DC shock. RESULTS: There were no significant changes in left atrial or left atrial appendage function after endocardial or transthoracic DC shocks. Left atrial SEC did not develop after endocardial or transthoracic DC shocks. CONCLUSIONS: Endocardial and transthoracic DC shocks are not directly responsible for left atrial and left atrial appendage stunning and do not contribute to the stunning that is observed after the cardioversion of AF to sinus rhythm.

Transvenous ventricular pacing options in Ebstein's anomaly.

Transvenous pacing in patients with Ebstein's anomaly is challenging due to anatomical abnormalities of the tricuspid valve and right heart chambers. This paper describes the various transvenous ventricular lead placement options for permanent pacing in patients with Ebstein's anomaly. In Ebstein's anomaly, stable long-term ventricular pacing can be achieved by positioning the lead either in the atrialised right ventricle, true right ventricle or the cardiac venous system. The pitfalls and advantages of pacing from these sites with the electrocardiographic and chest X-ray appearances are described.

Clinical use of nonthoracotomy cardioversion-defibrillation system.

OBJECTIVE: To summarize our experience in 22 patients who had attempted nonthoracotomy implantable cardioverter-defibrillators (ICD) for malignant ventricular arrhythmias (VA). METHODS: Indications for implantation were ventricular fibrillation (VF) in 17 patients and refractory ventricular tachycardia in 5. Thirteen patients of them had underlying ischaemic heart disease. Seven had dilated cardiomyopathy and two had arrhythmogenic right ventricular dysplasia. RESULTS: 20 out of 22 patients were successfully implanted nonthoracotomic ICD with defibrillating threshold of 16.7 J. The mean hospital stay was 7.8 days. The complications included chest wall haematoma and ventricular lead dislodgment requiring repositioning. In the follow-up period of 10.1 +/- 8 months, 6 patients with VA were treated successfully by ICD. CONCLUSION: Nonthoracotomy ICD is possible in a vast majority of patients (91%) and should be considered in all patients requiring ICD without concomitant surgery.

Long-term performance of steroid-eluting lead in dual chamber pacing.

The atrial pacing lead is believed having higher stimulation thresholds and long-term complication rates than ventricular lead, this being one of the factors limiting the use of dual chamber pacing. A prospective study was undertaken to evaluate both atrial and ventricular bipolar tined steroid-eluting leads in long-term dual chamber pacing. There are 81 pairs of leads (Medtronic Capsure SP) used in 81 patients. Bipolar atrial and ventricular stimulation thresholds were measured immediately post implantation and 1, 3, 6, 12, 18 and 24 months. All leads demonstrated low mean stimulation thresholds during the follow-up and more than 94% of leads could be paced chronically in the atrium and ventricle at 2.5 volts. In conclusion, atrial and ventricular steroid-eluting leads gave excellent stimulation thresholds allowing low energy long-term dual chamber pacing.

Failure of automatic mode switching: recognition and management.

Dual chamber pacing is desirable to optimize AV synchrony and to potentially decrease the incidence of supraventricular tachyarrhythmias. Patients with alternating periods of both supraventricular tachyarrhythmias and bradycardia pose a difficult challenge when standard dual chamber pacemakers are implanted. The automatic mode switching mode algorithm was introduced to prevent tracking of paroxysmal supraventricular tachyarrhythmias and avoid the adverse hemodynamic and symptomatic consequences of a rapid ventricular response. In some cases, failure to mode switch may take place when the atrial signal during tachycardia is of insufficient amplitude to be sensed. Failure to mode switch may also occur when the atrial signal periodically occurs in the atrial blanking period(s). In this article, we describe failure to mode switch in seven patients with paroxysmal supraventricular tachyarrhythmias after a Telectronics Meta DDDR 1254 device was implanted. Each patient had paroxysmal atrial flutter and/or atrial fibrillation and presented with either repetitive episodes of oscillation between atrial tracking and mode switching to a nonatrial tracking pacing mode or complete failure to mode switch. Six of seven patients were taking antiarrhythmic drugs that resulted in slowing of the atrial cycle length. Pacemaker reprogramming was required in each case to restore reliable mode switching during subsequent recurrences of the atrial tachyarrhythmias. We conclude that careful pacemaker programming of patients with paroxysmal atrial flutter and the Telectronics Meta DDDR 1254 is necessary when patients are taking an antiarrhythmic drug that slows atrial cycle length.

Chronic steroid-eluting lead performance: a comparison of atrial and ventricular pacing.

It is generally believed that atrial pacing leads have higher stimulation thresholds and long-term complication rates than ventricular leads, and this is one of the factors limiting the use of dual chamber pacing. A study was undertaken to compare atrial and ventricular bipolar tined steroid-eluting leads in two designs: the Medtronic CapSure SP and the Telectronics Encor Dec. There were 123 pairs of leads: 81 CapSure SP and 42 Encor Dec. Bipolar atrial and ventricular stimulation thresholds, electrograms, and pacing impedance were measured using the Telectronics META DDDR pulse generator immediately postimplantation, and at 1, 3, and 6 months for all leads and at 12, 18, and 24 months for the CapSure SP. The only major lead complication was a 2% atrial lead dislodgment rate. All leads demonstrated low stimulation thresholds, with the CapSure SP leads having lower values than comparable Encor Dec leads. All leads had a mean range of 0.53-0.89 V at all testing periods with P < 0.05 for atrial leads only. There were no differences in electrogram size between manufacturers and no instances of atrial and ventricular undersensing. Pacing impedance was about 100 omega higher for the Encor Dec leads (P < 0.05, atrial leads only), suggesting that these leads will result in lower pacing energy losses provided the pulse generators are at identical settings. More than 90% of patients could be paced chronically in the atrium and ventricle at 2.5 V, but for chronic 1.6-V pacing, the CapSure SP leads were superior. In conclusion, atrial and ventricular steroid-eluting leads of both manufacturers gave excellent stimulation threshold results allowing low energy dual chamber pacing.

The safety of digital mobile cellular telephones with minute ventilation rate adaptive pacemakers.

In vitro tests suggest that rate adaptive pacemakers using changes in transthoracic impedance to vary pacing rate may be affected by digital mobile telephones. Electromagnetic fields generated by digital mobile telephones (Global System for Mobile [GSM]) represent a potential source of electromagnetic interference (EMI) for the Telectronics META rate adaptive pacemakers, which use transthoracic impedance as a sensor to determine changes in minute ventilation. Sixteen implanted Telectronics META pulse generators were exposed to 25-W simulated GSM transmissions (900-MHz carrier pulsed at 2, 8, and 217 Hz with a pulse width of 0.6 ms) and the antenna of a 2-W digital mobile telephone (900-MHz, 217-Hz pulse, 0.6-ms pulse width). The 12 dual and four single chamber devices were programmed to maximum sensitivity and assessed in unipolar and bipolar settings and rate adaptive and nonrate adaptive modes. In all cases of EMI, testing was repeated at lower, more routinely set bipolar sensitivity levels. At maximum sensitivity, 11 of 16 devices displayed no evidence of EMI. Brief ventricular triggering occurred in 2, a brief pause in 1, a combination of both in 1, and a brief episode of pacemaker-mediated tachycardia in 1. With pulse generators programmed to more routine sensitivities, only one device displayed rare single beat ventricular triggering. No changes in minute ventilation rate adaptive pacing were observed. At maximum unipolar sensitivities, the META series of rate adaptive pacemakers are resistant to clinically important EMI from digital mobile telephones. Set at routine sensitivities, these devices perform reliably in the presence of digital mobile telephones.

The steroid-eluting electrode: a 10-year experience.

The benefits of steroid-eluting electrodes in reducing stimulation thresholds are well established. A question frequently asked, however, is how long does such an electrode maintain its effect on reducing stimulation threshold? Two studies were designed to answer this question by reporting a long-term prospective human implant review as well as an analytical examination of explanted leads from both humans and animals to determine the amount of remaining steroid in the silicone plug. A previously reported double-blind human study using 20 implanted unipolar ventricular leads, 10 with and 10 without steroid, was followed for 10 years. Pulse width stimulation thresholds were determined at regular intervals using a customized VVIC pulse generator programmed to 1.5-V output. Throughout the study period, the mean stimulation thresholds for the steroid-eluting leads remained almost constant, with a narrow standard deviation, whereas the leads without steroid showed an unpredictable rise and a wide standard deviation. All patients with the steroid-eluting electrodes were paced at 1.5 V, and the four surviving patients still have their original pulse generators. In the second study, the remaining steroid from 25 explanted leads (18 canine and 7 human), were analyzed and graphed against implant times that ranged from 1-350 weeks. Extrapolation of the line of best fit suggests that about 20% of the steroid is still present at 10 years and 18% at 20 years. Only small quantities of steroid are required for its stimulation threshold lowering effect, which continues clinically to at least 10 years. Sufficient quantity of steroid may well be present at 20 years.

Assessment of left ventricular function after radiofrequency and direct current atrioventricular node ablation.

BACKGROUND: There is limited information available regarding the effect of catheter ablation of the antioventricular (AV) junction on left ventricular (LV) function. Both deterioration and improvement in LV function have been reported following direct current (DC) ablation of the AV junction. The deterioration of LV function following DC ablation of the AV junction may be due to the accompanying barotrauma, DC arcing and direct coagulation, or even the effects of chronic ventricular pacing. If this deterioration of LV function was a result of the accompanying effects of DC shock, the use of radiofrequency ablation (RF) should not result in deterioration of LV function. AIM: To study LV function before and after different methods of AV junction ablation and in patients with chronic ventricular pacing without AV junction ablation. MATERIAL: This study assessed LV function in patients following RF ablation, low energy DC ablation of the AV junction and compared the results with our previously reported finding in patients who had AV junction ablation using high energy DC shock. A group of patients undergoing permanent single chamber ventricular pacemaker implantation without AV junction ablation were selected as controls. METHODS: All patients were paced in the ventricle at 110 beats/minute during LV function assessment by radionuclide angiography. Global LV function and segmental wall motion abnormalities were assessed before, immediately following and three months after ablation. RESULTS: In the high energy DC ablation group, a fall in global LV function (50 +/- 3.0% to 43 +/- 3.0%, p = 0.02) and impairment of segmental wall motion were detected. Low energy DC ablation resulted in segmental wall motion impairment similar to high energy DC but without affecting global ejection fraction (47.0% +/- 6.7 to 45.5% +/- 3.1, p > 0.05). Neither RF ablation (44.0% +/- 3.3 to 45.3% +/- 3.5, p > 0.05), nor chronic pacing (46.7% +/- 4.9 to 47.0% +/- 2.9 p > 0.05) had any effect on global or segmental LV function. CONCLUSIONS: Low energy DC or RF ablation of the AV junction does not affect global LV ejection fraction. The deterioration of global LV function after high energy DC shock ablation appears to be related to the accompanying effects of DC energy and not to the effects of chronic ventricular pacing.

Atrial pacing leads: the clinical contribution of steroid elution.

Although the original atrial pacing leads were passive fixation and J shaped for right atrial appendage placement, the subsequent development of the active fixation screw-in lead found favor because of a perceived low incidence of lead dislodgment and a wider selection of atrial pacing sites. A bipolar atrial lead study was undertaken to compare the long-term atrial implant data in 215 patients. Study leads comprised one passive fixation, steroid-eluting lead (Medtronic CapSure SP, 119 patients) and three nonsteroid-eluting leads; two active fixation (Medtronic BISPING model 4058, 30 patients; and Telectronics ACCUFIX model 330-801, 44 patients) and one passive fixation (Telectronics ENCOR model 330-854, 22 patients). Bipolar atrial voltage stimulation thresholds and electrograms were measured using the Telectronics META DDDR immediately postimplantation, and at 1-, 3-, 6-, 12-, and 18-month follow-up. There were 135 males and the mean age 68 years. The incidence of lead dislodgment was 4% for active fixation and 2% for passive fixation. All nonsteroid leads showed a typical rise in stimulation threshold with the highest being the ACCUFIX followed by the BISPING and ENCOR. The steroid-eluting CapSure SP, however, demonstrated a flat response with 98% of leads at 18 months having a value < or = 1.3 volts allowing voltage programming to 2.5 volts (2:1 safety ratio). Telemeted electrograms showed no differences for all leads at all visits. For low voltage atrial pacing with a low incidence of dislodgment and satisfactory atrial sensing, the steroid-eluting passive fixation lead is superior to all nonsteroid-eluting leads.