for the REPLACE Registry InvestigatorsBackground-Prospective studies defining the risk associated with pacemaker or implantable cardioverter-defibrillator replacement surgeries do not exist. These procedures are generally considered low risk despite results from recent retrospective series reporting higher rates. Methods and Results-We prospectively assessed predefined procedure-related complication rates associated with elective pacemaker or implantable cardioverter-defibrillator generator replacements over 6 months of follow-up. Two groups were studied: those without (cohort 1) and those with (cohort 2) a planned transvenous lead addition for replacement or upgrade to a device capable of additional therapies. Complications were adjudicated by an independent events committee. Seventy-two US academic and private practice centers participated. Major complications occurred in 4.0% (95% confidence interval, 2.9 to 5.4) of 1031 cohort 1 patients and 15.3% (95% confidence interval, 12.7 to 18.1) of 713 cohort 2 patients. In both cohorts, major complications were higher with implantable cardioverter-defibrillator compared with pacemaker generator replacements. Complications were highest in patients who had an upgrade to or a revised cardiac resynchronization therapy device (18.7%; 95% confidence interval, 15.1 to 22.6). No periprocedural deaths occurred in either cohort, although 8 later procedure-related deaths occurred in cohort 2. The 6-month infection rates were 1.4% (95% confidence interval, 0.7 to 2.3) and 1.1% (95% confidence interval, 0.5 to 2.2) for cohorts 1 and 2, respectively. Conclusions-Pacemaker and implantable cardioverter-defibrillator generator replacements are associated with a notable complication risk, particularly those with lead additions. These data support careful decision making before device replacement, when managing device advisories, and when considering upgrades to more complex systems. Clinical Trial Registration-URL: http://www.clinicaltrials.gov. Unique identifier: NCT00395447.

In this multicenter prospective study with 6 months of follow-up, infections associated with CIED replacements were surprisingly infrequent, possibly due to the use of preoperative antibiotics. Patients with infections were more likely to have had a postoperative hematoma, and sites with higher infection rates had sicker patients and lower overall procedural volume.

Heart rate rose, whereas LFP, LFPn and LFP/HFP fell before the onset of VT. This pattern of changes could be explained by a rise in sympathetic activity and saturation of the HRV signal resulting in dissociation of the average and rhythmical effects of sympathetic activity. These findings suggest that alterations in autonomic activity contributed to arrhythmogenesis in this group of patients.

Bipolar recordings eliminate much of the far-field signal, while minimally filtered unipolar recordings contain substantial far-field signal components. These properties may allow the onset of the unipolar recording to serve as a timing reference for the bipolar recording obtained from the same electrode catheter during mapping of focal atrial or ventricular tachycardias. Mapping and RF ablation were performed in 26 patients with focal ventricular tachycardia and 14 patients with focal atrial tachycardia. At 205 mapping sites, simultaneous recordings of (1) minimally filtered unipolar electrograms (0.5-500 Hz), (2) high pass filtered unipolar electrograms (100 Hz), and (3) filtered bipolar recordings (30-500 Hz) were analyzed. The interval between the onset of the minimally filtered unipolar electrogram and the first peak of the bipolar electrogram (UniOn-BiP) correlated closely with the timing of the local electrogram referenced to the surface ECG (r = 0.85, P < 0.001). Of 53 sites where RF ablation was performed, UniOn-BiP was shorter at successful compared to unsuccessful sites (3.8 +/- 3.5 vs 9.2 +/- 5.2 ms, P < 0.001) and was < 15 ms at all successful sites. In conclusion, the comparison of simultaneous unipolar and bipolar electrograms from a single catheter allows assessment of the prematurity of local electrograms from a focal source without the use of the P wave or QRS onset as a timing reference.

No abstract

HR and RRV did not change before type 1 VTsm, suggesting that short-term changes in autonomic activity were not essential to initiation of apparent PVC-triggered VTsm. In contrast, RR interval dynamics before type 2 VTsm suggested that short-term changes in neurohormonal activity contributed to arrhythmia initiation. Heterogeneities in arrhythmia onset may reflect distinct triggers and substrate properties that could provide a basis for effective therapeutic targets.

No abstract

Background:The implantable cardioverter defibrillator (ICD) has underscored the limitations of our methods of risk assessment. ICDs should be available to patients at high risk for arrhythmic death, but because of the potential for adverse effects and high cost it should be scrupulously avoided in patients whose lives will not be prolonged. Unfortunately, discrimination between these two groups of patients remains a challenge. Recent clinical trial results have not only shown that electrophysiological studies (EPS) in combination with other risk stratifiers identify patients with ischemic heart disease at high risk for arrhythmic death, but they have linked the efficacy of ICD therapy to the results of EPS. However, to perform EPS in all potential candidates for ICD therapy would be a time‐consuming and costly burden to medical services and would expose many patients to the risks and discomfort of an invasive procedure. Noninvasive identification of appropriate candidates is therefore essential to successful application of EPS. Methods:Nonsustained ventricular tachycardia (NSVT) and a reduced left ventricular ejection fraction (EF) was used to select patients for EPS in two important trials, but it is not certain that these are the optimal tests or that the optimal thresholds 1 episode of NSVT 3 beats; EF 0.35 or EF 0.40) were used. A number of studies have addressed the accuracy of clinical factors for predicting the results of EPS and a number of noninvasive tests have been proposed including the signal‐averaged electrocardiogram, heart rate variability, T‐wave alternans, and high spatial resolution (multilead) electrocardiography. In some contexts, combinations of factors provide significant improvements in accuracy. However, the populations studied were often highly selected, which makes comparisons between techniques or prediction of responses in the populations that would require screening difficult. Results from recently completed and ongoing clinical trials should provide important new information. A greater problem is that EPS has not been shown to consistently provide accurate discrimination of patients with nonischemic cardiac disorders. Conclusions:Effective widespread application of ICD therapy will require greater precision of patient selection. Noninvasive tests under investigation demonstrate considerable promise in selecting appropriate candidates for EPS. However, because the most precise methods of risk assessment are likely to be those most closely linked to the mechanisms of fatal arrhythmias, it is important that further development of noninvasive techniques incorporates advances in basic cardiac electrophysiology. A.N.E. 1999;4(4):434–442