Risk of Adverse Outcomes Associated With Cardiac Sarcoidosis Diagnostic Schemes

BACKGROUND

Multiple cardiac sarcoidosis (CS) diagnostic schemes have been published.

OBJECTIVES

This study aims to evaluate the association of different CS diagnostic schemes with adverse outcomes. The diagnostic schemes evaluated were 1993, 2006, and 2017 Japanese criteria and the 2014 Heart Rhythm Society criteria.

METHODS

Data were collected from the Cardiac Sarcoidosis Consortium, an international registry of CS patients. Outcome events were any of the following: all-cause mortality, left ventricular assist device placement, heart transplantation, and appropriate implantable cardioverter-defibrillator therapy. Logistic regression analysis evaluated the association of outcomes with each CS diagnostic scheme.

RESULTS

A total of 587 subjects met the following criteria: 1993 Japanese (n = 310, 52.8%), 2006 Japanese (n = 312, 53.2%), 2014 Heart Rhythm Society (n = 480, 81.8%), and 2017 Japanese (n = 112, 19.1%). Patients who met the 1993 criteria were more likely to experience an event than patients who did not (n = 109 of 310, 35.2% vs n = 59 of 277, 21.3%; OR: 2.00; 95% CI: 1.38-2.90; P < 0.001). Similarly, patients who met the 2006 criteria were more likely to have an event than patients who did not (n = 116 of 312, 37.2% vs n = 52 of 275, 18.9%; OR: 2.54; 95% CI: 1.74-3.71; P < 0.001). There was no statistically significant association between the occurrence of an event and whether a patient met the 2014 or the 2017 criteria (OR: 1.39; 95% CI: 0.85-2.27; P = 0.18 or OR: 1.51; 95% CI: 0.97-2.33; P = 0.067, respectively).

CONCLUSIONS

CS patients who met the 1993 and the 2006 criteria had higher odds of adverse clinical outcomes. Future research is needed to prospectively evaluate existing diagnostic schemes and develop new risk models for this complex disease.

The Impact of Vendor-Specific Ultrasound Beam-Forming and Processing Techniques on the Visualization of In Vitro Experimental "Scar": Implications for Myocardial Scar Imaging Using Two-Dimensional and Three-Dimensional Echocardiography

BACKGROUND

Myocardial scar appears brighter compared with normal myocardium on echocardiography because of differences in tissue characteristics. The aim of this study was to test how different ultrasound pulse characteristics affect the brightness contrast (i.e., contrast ratio [CR]) between tissues of different acoustic properties, as well as the accuracy of assessing tissue volume.

METHODS

An experimental in vitro "scar" model was created using overheated and raw pieces of commercially available bovine muscle. Two-dimensional and three-dimensional ultrasound scanning of the model was performed using combinations of ultrasound pulse characteristics: ultrasound frequency, harmonics, pulse amplitude, steady pulse (SP) emission, power modulation (PM), and pulse inversion modalities.

RESULTS

On both two-dimensional and three-dimensional imaging, the CR between the "scar" and its adjacent tissue was higher when PM was used. PM, as well as SP ultrasound imaging, provided good "scar" volume quantification. When tested on 10 "scars" of different size and shape, PM resulted in lower bias (-9.7 vs 54.2 mm³) and narrower limits of agreement (-168.6 to 149.2 mm³ vs -296.0 to 404.4 mm³, P = .03). The interobserver variability for "scar" volume was better with PM (intraclass correlation coefficient = 0.901 vs 0.815). Two-dimensional and three-dimensional echocardiography with PM and SP was performed on 15 individuals with myocardial scar secondary to infarction. The CR was higher on PM imaging. Using cardiac magnetic resonance as a reference, quantification of myocardial scar volume showed better agreement when PM was used (bias, -645 mm³; limits of agreement, -3,158 to 1,868 mm³) as opposed to SP (bias, -1,138 mm³; limits of agreement, -5,510 to 3,233 mm³).

CONCLUSIONS

The PM modality increased the CR between tissues with different acoustic properties in an experimental in vitro "scar" model while allowing accurate quantification of "scar" volume. By applying the in vitro findings to humans, PM resulted in higher CR between scarred and healthy myocardium, providing better scar volume quantification than SP compared with cardiac magnetic resonance.

Five year outcomes of the subcutaneous implantable cardioverter-defibrillator EFFORTLESS (evaluation of factors impacting clinical outcome and cost effectiveness of the S-ICD) registry

Funding Acknowledgements

Type of funding sources: Private company. Main funding source(s): Boston Scientific

OnBehalf

EFFORTLESS Registry

Introduction

Patients (pts) implanted with transvenous (TV) implantable cardioverter-defibrillator (ICD) experience complications (Cx) associated with TV leads and inappropriate shocks (IAS) for atrial fibrillation (AF) or other supraventricular tachycardias (SVT). The EFFORTLESS S-ICD Registry is a 5-year (yr) follow-up (f/u) study of pts implanted with the subcutaneous ICD (S-ICD).

Purpose

To report on the 5-yr outcomes of pts with a wide range of S-ICD indications implanted with early generation devices.

Methods

Pts were enrolled at 43 centers February 2011-December 2014. Kaplan-Meier Cx, appropriate shock (AS), and IAS rates are reported.

Results

994 pts (495 retrospective) were enrolled in the EFFORTLESS study and 984 pts (28% female, 48 ± 17 yrs, BMI 27 ± 6 kg/m2, ejection fraction 43 ± 18%) underwent S-ICD implantation. Mean study f/u was 4.4 ± 1.6 yrs. The pt cohort had diverse etiologies: 31% ischemic heart disease, 19% non-ischemic cardiomyopathy, 11% hypertrophic cardiomyopathy, 17% channelopathies, and 20% of pts miscellaneous. Total system- and procedure-related Cx (table) were 9.4% at 5 yrs. AS and IAS rates at 5 yrs were 15.9% and 16.9%, respectively and the IAS rates for AF/SVT and t wave oversensing were 3.1% and 5.8%, respectively. More pts experienced Cx and IAS in the first yr than in yrs 2-5 altogether (8.7 vs 8.2%), the most common as a result of discomfort/erosion (38%), IAS (26%), system infection (9%), and premature battery depletion (9%). Of these late Cx, 74% were experienced by retrospective pts. Spontaneous conversion efficacy for the first shock and final shocks was 89.7% and 97.7%. Of the 91 (9.2%) deaths reported, none were associated with the S-ICD system or procedure. Cause of death was cardiac for 40 pts, non-cardiac for 40 pts, other for 4 pts, and unknown for 7 pts. Only 20 (2.0%) pts had their S-ICD replaced for a TV device for pacing: 4 bradycardia, 7 anti-tachycardia, and 9 for biventricular pacing.

Conclusions

The EFFORTLESS registry provides 5-year follow-up for a diverse, large, multinational S-ICD registry. Complications primarily occurred in the first year but remained low through 5 years. Inappropriate shock rates were typically observed in older generation devices prior to introduction of the SMART Pass filter. Replacement for TV-ICD due to the need for pacing was rare. Outcome 30 day 1 yr 2 yr 3 yr 4 yr 5yr Annual Complications (Kaplan-Meier) 2.0 5.3 6.8 7.6 8.6 9.4 1.9 IAS, overall (Kaplan-Meier) 1.7 8.7 11.6 13.1 14.6 16.9 3.4 IAS, t wave oversensing 3.4 5.8 1.2

The impact of catheter ablation for atrial fibrillation in heart failure

Atrial fibrillation (AF) commonly co‐exists with systolic heart failure (SHF) and its presence is associated with a worse prognosis. Despite this, a rhythm control approach using antiarrhythmic drugs (AADs) to reduce AF burden has demonstrated no prognostic benefit. Catheter ablation (AFA) is more effective than AADs at reducing AF burden. We performed a meta‐analysis to evaluate the impact of AFA on outcomes in SHF. Electronic databases were systematically searched. We included only randomized controlled trials that examined the impact of AFA on clinical outcomes in patients with SHF (LVEF <50%). We included studies with any ablation strategy that incorporated pulmonary vein isolation and any control group. Seven studies (n = 858) were included with a mean follow‐up of 6‐38 months. In comparison to controls, AFA was associated with significant reductions in all‐cause mortality (relative risk [RR] 0.52, P = 0.0009) and unplanned or heart failure hospitalization (RR 0.58, P < 0.00001). Compared to controls, AFA was also associated with significant improvements in LVEF (mean difference 6.30%, P < 0.00001), Minnesota Living with Heart Failure Questionnaire score (mean difference 9.58, P = 0.0003), 6‐minute walk distance (mean difference 31.78 m, P = 0.003) and VO₂ max (mean difference 3.17, P = 0.003). However, major procedure‐related complications occurred in 2.4%‐15% of ablation patients. In patients with AF and SHF, catheter ablation has significant benefits. Further work is needed to establish the role of ablation in the routine treatment of SHF patients with AF.

We performed a meta‐analysis evaluating the impact of catheter ablation in patients with atrial fibrillation and systolic heart failure. A total of 858 patients were included across seven studies. Compared to controls, ablation was associated with lower all‐cause mortality and hospitalizations, higher LVEF, and improved symptoms and physiologic parameters.

An entirely subcutaneous implantable cardioverter-defibrillator

BACKGROUND

Implantable cardioverter-defibrillators (ICDs) prevent sudden death from cardiac causes in selected patients but require the use of transvenous lead systems. To eliminate the need for venous access, we designed and tested an entirely subcutaneous ICD system.

METHODS

First, we conducted two short-term clinical trials to identify a suitable device configuration and assess energy requirements. We evaluated four subcutaneous ICD configurations in 78 patients who were candidates for ICD implantation and subsequently tested the best configuration in 49 additional patients to determine the subcutaneous defibrillation threshold in comparison with that of the standard transvenous ICD. Then we evaluated the long-term use of subcutaneous ICDs in a pilot study, involving 6 patients, which was followed by a trial involving 55 patients.

RESULTS

The best device configuration consisted of a parasternal electrode and a left lateral thoracic pulse generator. This configuration was as effective as a transvenous ICD for terminating induced ventricular fibrillation, albeit with a significantly higher mean (+/-SD) energy requirement (36.6+/-19.8 J vs. 11.1+/-8.5 J). Among patients who received a permanent subcutaneous ICD, ventricular fibrillation was successfully detected in 100% of 137 induced episodes. Induced ventricular fibrillation was converted twice in 58 of 59 patients (98%) with the delivery of 65-J shocks in two consecutive tests. Clinically significant adverse events included two pocket infections and four lead revisions. After a mean of 10+/-1 months, the device had successfully detected and treated all 12 episodes of spontaneous, sustained ventricular tachyarrhythmia.

CONCLUSIONS

In small, nonrandomized studies, an entirely subcutaneous ICD consistently detected and converted ventricular fibrillation induced during electrophysiological testing. The device also successfully detected and treated all 12 episodes of spontaneous, sustained ventricular tachyarrhythmia. (ClinicalTrials.gov numbers, NCT00399217 and NCT00853645.)

Manual vs. automatic capture management in implantable cardioverter defibrillators and cardiac resynchronization therapy defibrillators

Aims

The Secura™ ICD and Consulta™ CRT-D are the first defibrillators to have automatic right atrial (RA), right ventricular (RV), and left ventricular (LV) capture management (CM). Complete CM was evaluated in an implantable cardioverter defibrillator (ICD) population.

Methods and results

Two prospective clinical studies were conducted in 28 centres in Europe and Israel. Automatic CM data were compared with manual threshold measurements, the CM applicability was determined, and adjustments to pacing outputs were analysed. In total, 160 patients [age 64.6 ± 10.4 years, 77% male, 80 ICD and 80 cardiac resynchronization therapy defibrillator (CRT-D)] were included. The differences between automatic and manual measurements were ≤0.25 V in 97% (RA CM) and 96% (RV CM) and were all within the safety margin. Fully automatic CM measurements were available within 1 week prior to the 3-month visit in 90% (RA), 99% (RV), and 97% (LV) of the patients. Results indicated increased output (threshold >2.5 V) due to raised RA threshold in seven (4.4%), high RV threshold in nine (5.6%), and high LV threshold in three patients (3.8%). All high threshold detections and all automatic modulations of pacing output were adjudicated appropriate.

Conclusion

Complete CM adjusts pacing output appropriately, permitting a reduction in office visits while it may maximize device longevity.

The study was registered at ClinicalTrials.gov identifiers: NCT00526227 and NCT00526162.

Gentamicin induced ototoxicity during treatment of enterococcal endocarditis: resolution with substitution by netilmicin

Enterococcal endocarditis can be very difficult to eradicate, requiring prolonged treatment with a combination of a penicillin and an aminoglycoside. In this patient with a pacemaker associated enterococcal endocarditis, ototoxicity occurred due to total gentamicin dose despite plasma concentrations consistently within the treatment range. Substitution with netilmicin, without a break in aminoglycoside treatment, resulted in a rapid improvement in hearing and allowed the required course of aminoglycoside to be completed. The risk factors for ototoxicity with gentamicin are reviewed, in particular the dangers of increasing age and of multiple and prolonged courses. Close treatment monitoring does not totally avoid this risk, especially when prolonged aminoglycoside treatment is required. This case emphasises the need for prompt investigation and adequate, definitive treatment of enterococcal endocarditis to avoid the increased risk consequent on repeated courses of antibiotics. The resolution of the ototoxicity with netilmicin is consistent with other reports of lower cochleotoxicity than with other aminoglycosides.

Permanent Pacemakers:. Should Straightened Atrial Leads Be Repositioned?

The aim of this study was to assess if atrial leads whose "J" configuration has straightened significantly on the postprocedural chest X ray should be repositioned. Between January 1996 and December 1997, 445 patients underwent dual chamber pacemaker implantation at the Papworth Hospital. Postprocedural chest X rays were available in 410 of these. The degree of straightening of the tip of the atrial lead was assessed from the lateral chest X ray and was graded as mild (-10 to +10 degrees from the horizontal), moderate (+10 to +30 degrees), or severe (> or = +30 degrees). Patients were followed with regard to atrial sensing and pacing characteristics, lead displacements, and lead revisions. Fifty-two (12%) patients had some degree of straightening (graded mild, moderate, severe) of the atrial lead on the postprocedure chest X ray (passive fixation in 48, active 4). Of these, 12 patients underwent next day lead repositioning, 5 of whom had abnormalities of pacing and/or sensing parameters. Seven patients therefore underwent repositioning of the atrial lead despite normal pacing parameters in view of lead straightening alone. Of the 12 patients who underwent repositioning, 3 still had lead straightening after the second procedure. The cohort for follow-up consisted of 43 patients (24 [56%] men, age 69 +/- 11 years at the time of implant) who were left with significant atrial lead straightening but adequate atrial parameters. Straightening was mild in 26 patients, moderate in 10, and severe in 7 patients. At implant the P wave amplitude was 4.8 +/- 2.4 mV. Follow-up was for 4.8 +/- 2.1 years, a total of 178 patient years. At final follow-up, the P wave amplitude was 2.7 +/- 1.3 (P < 0.05 vs implant). Censoring events occurred in 16 cases, comprising 11 deaths (none suspected to be pacemaker or lead related), 3 cases of persistent atrial fibrillation, 1 system extraction for infection, and 1 lead extraction for erosion. There were no cases of inadequate atrial lead sensing or pacing in the remaining patients. Irrespective of the degree of lead straightening on the postoperative lateral chest X ray, atrial leads should not be repositioned unless there are abnormalities of pacing or sensing parameters.

Catheter cryoablation of supraventricular arrhythmias: a painless alternative to radiofrequency energy

Cryothermy has potential advantages over RF energy for catheter ablation, including reversibility of lesion formation, catheter stability, and less procedural discomfort. Cryoablation procedures were performed in 14 patients with atrioventricular reentrant tachycardias (AVNRTs), 13 patients with accessory pathway (AP)-mediated tachycardias, and 5 patients with atrial fibrillation. The numbers of energy applications, pain scores, procedural times, and outcomes were recorded and compared with age- and sex-matched patients undergoing similar RF procedures. Cryoablation was successful in 26 of 32 patients (11/14 AVNRT, 10/13 AP, 5/5 AF) compared with 30 of 32 undergoing RF procedures, with similar numbers of energy applications and procedural times. Cryothermy was painless in all patients, and the overall procedural discomfort was significantly less than in patients treated with RF (1.3 +/- 2.2 vs 6.1 +/- 3.5). In patients with anteroseptal pathways, cryomapping successfully identified safe sites to target the delivery of energy. Cryothermy is a painless and safe alternative to RF. It may be particularly useful for catheter ablation of patients with pathways close to the atrioventricular node.

"Pills and pulses": hybrid therapy for atrial fibrillation

Nonpharmacologic techniques are being increasingly applied to the treatment of atrial fibrillation (AF). None of these techniques (other than maze surgery) begins to approach 100% efficacy for long-term elimination of arrhythmia. This review examines the evidence for "hybrid" therapy, using combinations of drug and nonpharmacologic treatments. The immediate success rate of electrical cardioversion can be increased with amiodarone or ibutilide, and a number of drugs reduce the risk of AF recurrence. Preventing or reversing electrical atrial remodeling is an attractive strategy for maintenance of sinus rhythm. However, the available evidence (relating to the use of verapamil) is limited and conflicting. Ablation of the cavotricuspid isthmus is effective when antiarrhythmic drugs given for AF give rise to typical flutter. Isthmus and other right atrial linear lesions are poor as a sole therapy for AF, but better when drugs are added. Better still is the combination of left atrial linear lesions with drugs. In patients with AF recurrence following focal ablation/pulmonary vein isolation procedures, drugs are an alternative to extensive linear ablation. Some studies indicate that pacing to prevent AF may be effective, but rarely without continued antiarrhythmic drug therapy. This may represent a specific effect or simply improved drug tolerance. Drugs also might assist pacemaker therapy by increasing the proportion of atrial arrhythmias that are highly organized and thus amenable to antitachycardia pacing. This and other forms of hybrid therapy will remain the subject of conjecture in the absence of controlled clinical trials, which are urgently needed.

The role of atrial ectopics in initiating paroxysmal atrial fibrillation

AIMS

To characterize the nature and timing of atrial ectopics preceding clinical episodes of paroxysmal atrial fibrillation.

METHODS AND RESULTS

Holter recordings (n= 177, 60 patients, 58% male, mean age 61.7 +/- 11.5 years) were performed on patients with paroxysmal atrial fibrillation. These were subjected to standard analysis and recordings containing atrial fibrillation episodes suitable for analysis were identified (n = 74). Beat interval files differentiating sinus rhythm from atrial fibrillation were generated and atrial ectopics were identified. Atrial ectopics preceding atrial fibrillation were found to be more frequent (5.07 +/- 7.39 min(-1)) and more premature (ratio of coupling interval to that of surrounding sinus cycles = 0.56 +/- 0.08) compared to ectopics occurring remote from atrial fibrillation episodes (frequency = 3.60 +/- 7.32 min(-1) P = 5 x 10(-24), prematurity ratio = 0.60 +/- 0.10, P = 2 x 10(-73)). Atrial ectopic coupling interval frequency histograms were generated and analysed visually and by an automated statistically based test. Many ectopics were seen to occur at one coupling interval in 27 recordings (in eight this occurred only preceding atrial fibrillation onset, while in a further 19 cases this was also seen remote from atrial fibrillation onset). Overall 45% of ectopics preceding atrial fibrillation episodes occurred in isolation, 13% as part of a bigeminal rhythm, 22% as couplets and 20% as runs. This pattern did not differ from that seen remote from atrial fibrillation episodes.

CONCLUSION

Paroxysmal atrial fibrillation is preceded by ectopics of a fixed coupling interval in a significant proportion of patients. If, as seems likely, this is a marker of 'focally mediated' atrial fibrillation, then Holter techniques may provide a useful screening tool with which to identify patients suitable for fuller electrophysiological assessment.

Non-pharmacological treatments for atrial fibrillation. A critical perspective on the status quo

In a proportion of patients with atrial fibrillation, antiarrhythmic drugs are either ineffective, unsafe, or poorly tolerated. Accordingly, a variety of non-pharmacological treatments have been developed. This article critically reviews these modalities. (i) For ventricular rate control, catheter ablation of the atrioventricular node with pacemaker implantation is commonplace. An alternative is atrioventricular node modulation using a procedure similar to "slow pathway" ablation. (ii) For restoration of sinus rhythm, internal cardioversion using low energy shocks is highly effective; this has prompted the development of atrial and dual chamber defibrillators. (iii) To eliminate the atrial fibrillation substrate, a number of surgical procedures have been developed, of which the most effective is the "Maze" operation. The efficacy of this operation cannot be reproduced by conventional catheter ablation, and current research is concentrating on simplified procedures using new catheter designs for linear ablation. (iv) Finally, pacemakers and catheter ablation may be used to suppress the triggers for atrial fibrillation episodes. A number of atrial algorithms are under investigation for overdrive suppression of ectopy, and the use of multisite atrial pacing to alter the atrial response to ectopy has shown promising results. Catheter ablation has shown considerable success in preventing "focal" atrial fibrillation that is triggered or driven by ectopy arising usually from the pulmonary veins. To date, there are few data regarding the long-term efficacy and safety of these techniques, and their effects on quality of life. However, ongoing multicentre trials addressing these issues are expected to report over the next few years.

Unipolar electrogram characteristics predictive of successful radiofrequency catheter ablation of accessory pathways

INTRODUCTION

The purpose of this study was to determine the characteristics of the unipolar electrogram that are most helpful in predicting successful radiofrequency ablation of accessory pathways.

METHODS AND RESULTS

The unipolar electrogram was analyzed at 185 ablation sites in 53 patients; 94 attempts were directed at the site of earliest atrial activation ("atrial group") and 91 at the site of earliest ventricular activation ("ventricular group"). The electrogram was analyzed for several features, including pattern ("QS" or "initial R"). Unipolar pattern: Overall, a "QS" pattern was seen at 55% of unsuccessful, 75% of temporarily successful, and 90% of permanently successful sites. For the atrial group, the respective frequencies were 53%, 77%, and 92%, and for the ventricular group, 57%, 73%, and 86%. The difference in pattern distribution between unsuccessful and permanently successful sites was significant for all groups: overall, P < 0.0001; atrial group, P = 0.0005; ventricular group, P = 0.02. Absence of a "QS" pattern (i.e., "initial R") predicted a 92% chance of unsuccessful ablation. Additional features: Activation times were significantly shorter at permanently successful than at unsuccessful (P < 0.0001) or temporarily successful sites (P = 0.0002). No significant differences were found in atrial or ventricular amplitudes or in A/V ratios. Intrinsic deflection slew was lower at temporarily successful sites (P = 0.03 vs all other sites).

CONCLUSION

Ablation at sites revealing an "initial R" pattern (i.e., absent "QS") is very unlikely to be successful. Activation time is shorter at successful sites. These features are equally applicable when mapping the atrial potential as when mapping the ventricular potential.

Double-blind placebo-controlled trial of digoxin in symptomatic paroxysmal atrial fibrillation

BACKGROUND

Digoxin is commonly prescribed in symptomatic paroxysmal atrial fibrillation (AF) but has never been evaluated in this condition.

METHODS AND RESULTS

From a multicenter registry, 43 representative patients with frequent symptomatic AF episodes were recruited into a randomized, double-blind crossover comparison of digoxin (serum concentration, 1.29+/-0.35 nmol/L) and placebo. The study end point was the occurrence of 2 AF episodes (documented by patient-activated monitors), censored at 61 days. The median time to 2 episodes was 13.5 days on placebo and 18.7 days on digoxin (P<0. 05). The relative risk (95% CI) of 2 episodes (placebo:digoxin) was 2.19 (1.07 to 4.50). A similar effect was seen on the median time to 1 episode: increased from 3.5 to 5.4 days (P<0.05), relative risk 1. 69 (0.88 to 3.24). The mean+/-SD ventricular rates during AF recordings during placebo and digoxin treatment were 138+/-32 and 125+/-35 bpm, respectively (P<0.01). Twenty-four-hour ambulatory ECG recordings did not show significant differences in the frequency or duration of AF or in ventricular rate.

CONCLUSIONS

Digoxin reduces the frequency of symptomatic AF episodes. However, the estimated effect is small and may be due to a reduction in the ventricular rate or irregularity rather than an antiarrhythmic action.

Evolution of changes in the ventricular rhythm during paroxysmal atrial fibrillation

Changes in the RR interval within episodes of paroxysmal atrial fibrillation (PAF) have not been fully characterized. A database of 177 24-hour Holter recordings were created from patients with PAF in the CRAFT studies. PAF episodes of > or = 1 minute duration containing < or = 20% noise and preceded by > or = 1 minute of sinus rhythm with < or = 20% noise were selected. Sections of each AF episode containing 10 and 25 RR intervals were identified at the onset, middle, and termination of each episode. Descriptive characteristics (mean, SD, and RMSSD of RR intervals) were calculated within each section, and compared using a nonparametric, paired Wilcoxon test. In 25 patients (17 men, 60.6 +/- 12.2 years old), 231 episodes from 44 recordings met the selection criteria. The mean RR interval increased slightly between the onset and mid-portion of AF episodes (565.9 +/- 128.3 vs 580.3 +/- 144.7 ms, P < 0.001). The RR interval at the termination of AF was significantly greater than that at the start (627.1 +/- 156.1 vs 565.9 ms, P < 10-11) or mid-portion (627.1 +/- 156.1 vs 580.3 +/- 144.7 ms, P < 10-13). SD of the RR interval increased significantly between onset and mid-portion (111.1 +/- 60.2 vs 118.2 +/- 66.7 ms, P < 0.001) and more substantially between mid-portion and termination (118.2 +/- 66.7 vs 201.8 +/- 93.7 ms, P < 10-21). During paroxysms of AF, the mean RR interval and the variability of RR intervals increases. Termination of a paroxysm is preceded by a marked increase in RR interval variability.

Circadian variation in atrial fibrillation in patients with frequent paroxysms

Determinants of the duration of episodes of atrial fibrillation (AF) in patients with paroxysmal atrial fibrillation (PAF) are poorly understood. However, autonomic tone shows circadian variation and is known to affect atrial electrophysiology. We therefore compared the duration of episodes of AF with an onset during the day (08:00-22:00) to those with an onset during the night in a database of 24-hour ECG recordings in patients with frequent symptomatic PAF. The heart rate in the 30 seconds prior to AF onset was also compared. From 42 recordings, 296 episodes of AF > 30 seconds duration and preceded by > 60 seconds sinus rhythm were identified. The 165 nocturnal episodes tended to be shorter (median = 1.15 min) than the 131 diurnal episodes (median = 1.5 min) and the distribution of nocturnal and diurnal durations was significantly different (P = 0.007; Kolgomorov-Smirnov test). This was also true in recordings containing at least 1 diurnal and at least 1 nocturnal episode. The mean heart rate prior to AF onset was lower at night (62.2 +/- 11.8 vs 75.6 +/- 16.4 beats/min; P < 0.0001 Wilcoxon test). These findings suggest that in patients with frequent symptomatic PAF, autonomic influences affect the duration of episodes of AF and has pathphysiological and therapeutic implications.

Age and gender influences on rate and duration of paroxysmal atrial fibrillation

The influence of age and gender on the character of paroxysmal atrial fibrillation (PAD) has not been described.

METHODS

The heart rate (HR) during PAF in patients receiving placebo or antiarrhythmic therapy was analyzed. Data from 177 24-hour Holter recordings were analyzed to mark the onset and termination of PAF and converted into RR interval files. PAF episodes lasting at least 2 minutes and containing < or = 20% noise were included. HR during the first 30-second segment versus during the remainder of the episode, and the duration of PAF episodes were compared among groups of different ages and sex (Wilcoxon test).

RESULTS

236 episodes from 55 recordings in 32 patients (all patients: 61.4 +/- 12.8 years; men (19): 58.5 +/- 12.6 years; women (13) 65.5 +/- 12.4 years, P = ns for difference in age) fulfilled the inclusion criteria. Women had a higher mean heart rate at AF onset (123 +/- 35 beats/min vs 115 +/- 20 beats/min, P = 0.02) and during the remainder of the episode (120 +/- 25 beats/min vs 112 +/- 22 beats/min at the start, P = 0.01, and 116 +/- 26 beats/min vs 108 +/- 18 beats/min subsequently, P = 0.01). Episodes tended to be longer in women (mean 89.8 min vs 50.5 min, P = NS) and in the aged (mean 83.8 min vs 46.9 min, P = NS).

CONCLUSION

PAF episodes are associated with faster heart rates and last longer in women, which may reflect differing autonomic responses to AF. A slower ventricular rate during PAF in older patients probably reflects an increasing prevalence of impaired atrioventricular conduction.

Mid- and long-term similarity of ventricular response to paroxysmal atrial fibrillation: digoxin versus placebo

The effects of digoxin on ventricular response during atrial fibrillation (AF) and consequent effects on arrhythmic symptoms have still not been fully explained. This study investigated whether the treatment by digoxin contributes to mid- and long-term stabilization of ventricular cycles in patients with paroxysmal AF. A population of 45 patients with paroxysmal AF underwent 24-hour ECG recordings during each arm of a randomized crossover trial comparing digoxin and placebo. This yielded 30 Holter recordings from 22 patients that contained AF episodes lasting in excess of 2 minutes and with acceptably low Holter noise. Each AF episode was divided into nonoverlapping segments of 30 seconds and the distribution of RR intervals in each segment was compared with the distribution of all other AF segments in the same recording using the Kolmogorov-Smirnov test. The percentage of tests that revealed significant differences at levels of P < or = 0.01, and P < or = 0.001 were sorted according to the time between the segments compared. The comparisons of these results were performed between: (a) all recordings on placebo (n = 16) and all recordings on digoxin (n = 14), and (b) between recordings on placebo and on digoxin in 8 patients in whom paired analysis was possible. Adjacent AF segments (distance 0) differed significantly only in < 30% of both recordings on placebo and on digoxin. However, with increasing the distance between segments, the proportion of the significant differences between RR interval distributions increased more with placebo than with digoxin (P < 10(-300), Chi-square test). Paired data revealed larger differences between placebo and digoxin with increasing distance between segments. Thus in patients with paroxysmal AF, digoxin leads to more reproducible patterns of ventricular cycles that may be better tolerated clinically.

Analysis of the cardiac rhythm preceding episodes of paroxysmal atrial fibrillation

AIMS

This study seeks to elucidate whether there was a common mode of initiation of paroxysmal atrial fibrillation (PAF) episodes that might suggest new therapies.

METHODS

A library of 177 digitized and analyzed 24-hour Holter recordings from PAF pharmacotherapy trials was studied. All noise-free PAF episodes > or =0.5 minutes were identified. PAF episodes and the preceding 2 minutes of sinus rhythm were printed as tachograms and visually inspected. Heart rate and ectopic beat behavior were used to characterize modes of PAF onset by comparing half-minute segments of the final 2 minutes of sinus rhythm.

RESULTS

Thirty-four recordings (from 19 patients, aged 61.7 +/- 11.5 years) provided 231 PAF episodes suitable for analysis. No patients had a consistent mode of PAF onset. This was confirmed by systematic analysis of the five patients with the most episodes. Overall, a highly significant increase in ectopic beats, from 1.34 to 6.52 min(-1) (p < 0.001) was found, but heart rate did not significantly change (mean heart rate at onset = 64 beats/min). PAF was initiated by a solitary ectopic beat in more than half of the cases. No consistent evidence for short-long-short sequences, seen in ventricular arrhythmias, was found.

CONCLUSION

The mode of onset of atrial fibrillation is inconsistent, both across a population with PAF and within individuals. This has implications for understanding the mechanisms of atrial fibrillation onset in human beings and for the treatment of the disorder.

Distribution of fast heart rate episodes during paroxysmal atrial fibrillation

OBJECTIVE

To investigate the defibrillator waiting time (time between the recognition of atrial fibrillation and the actual shock) by studying paroxysmal atrial fibrillation episodes with RR intervals shorter than a certain limit (that is, episodes during which defibrillation should not be attempted).

METHODS

Long term 24 hour Holter recordings from a digoxin v placebo crossover study in patients with paroxysmal atrial fibrillation were analysed. In all, 23 recordings with atrial fibrillation episodes of at least 1000 ventricular cycles and with < 20% Holter artefacts or noise were used (11 recorded on placebo and 12 on digoxin). For each recording, the mean ("mean waiting time") and maximum ("maximum waiting time") duration of continuous sections of atrial fibrillation episodes with all RR intervals shorter than a certain threshold were evaluated, ranging the threshold from 400 to 1000 ms in 10 ms steps. For each threshold, the mean and maximum waiting times were compared between recordings on placebo and on digoxin.

RESULTS

Both the mean and maximum waiting times increased exponentially with increasing threshold. Practically acceptable mean waiting times less than one minute were observed with thresholds below 600 ms. There were no significant differences in mean waiting times and maximum waiting times between recordings on placebo and digoxin, and only a trend towards shorter waiting times on digoxin.

CONCLUSIONS

Introduction of a minimum RR interval threshold required to deliver atrial defibrillation leads to practically acceptable delays between atrial fibrillation recognition and the actual shock. These delays are not prolonged by digoxin treatment.

A relationship between fluctuations in heart rate and the duration of subsequent episodes of atrial fibrillation

A relationship between autonomic tone and the onset of paroxysmal atrial fibrillation in some patients is recognised. Episodes of PAF may vary enormously in duration, however, from a few beats to many hours. Whether autonomic tone influences the duration of the episodes has been less well investigated. From a database of Holter recording taken from patients with symptomatic PAF, we identified all episodes of at least 30 seconds duration which were preceded by noise free sinus rhythm. This study examined the heart rate prior to AF onset, the change in heart rate over the final minute of sinus rhythm and the time of AF onset, and compared the data from those episodes of AF of more than 5 minutes duration to the shorter ones. Heart rate was slower before long episodes of AF, but this was found to predominantly represent data from separate recordings. A highly significant rise in heart rate was detected prior to long AF episodes compared to shorter ones. Daytime AF episodes were slightly longer than nocturnal ones. The most important finding was that longer AF episodes were typified by a heart rate acceleration. This suggests that, regardless of underlying aetiology, and increase in sympathetic tone may be important in the sustenance of episodes of PAF.

Performance of basic ventricular tachycardia detection algorithms in implantable cardioverter defibrillators: implications for device programming

Around 20% of patients with third generation implantable cardioverter defibrillators receive inappropriate therapy, usually triggered by atrial fibrillation. This is because the criteria used for ventricular tachycardia detection by current implantable cardioverter defibrillators are based on the analysis of a sequence of RR intervals and may be inappropriately satisfied by supraventricular tachyarrhythmias. Algorithms for ventricular tachycardia detection were challenged against the full RR interval sequences from 482 spontaneous episodes of atrial fibrillation and 260 spontaneous episodes of ventricular tachycardia to determine their ability to discriminate between the arrhythmias. The sensitivities and specificities of the algorithms were calculated over a wide range of programmable parameters. For a given window length and detection interval, the most stringent algorithms, that required all beats to be classified as "fast", were more specific than those allowing a proportion of "normal" intervals, even after adjustment for differing sensitivity. These differences were less marked for faster tachycardias. Specificity increased with the detection window length to a limit of approximately 18 beats. We conclude that ventricular tachycardia is detected with the highest specificity if all beats in an analyzed sequence are required to be "fast," even after lengthening of the tachycardia detection interval to maintain sensitivity. Further improvement in algorithm performance may require the incorporation of criteria such as tachycardia onset and stability.

Graphical representation of complex data--diurnal patterns of initiations of atrial fibrillation episodes

A construction of a purpose designed graphical display is demonstrated in a study investigating the circadian distribution of patterns of RR interval sequences preceding episodes of paroxysmal atrial fibrillation (PAF). Based on a comparison with a (80%, 120%) range around the median of preceding 10 RR intervals, each RR interval is classified as normal, short, or long. Classifications of RR intervals in n-tuplets (n = 1, ...,5) preceding PAF episodes are used to compute probabilities of individual types of sequences occurring within 4-hour periods of the day (between 1 am, 5 am, 9 am, 1 pm, 5 pm, and 9 pm). Graphical representation of the data is proposed using a hierarchy of bar graphs. The graphical system has been filled with data of 327 atrial fibrillation episodes recorded in 46 24-hour ECGs in PAF patients. The graphical analysis supports a link between PAF initiation and cardiac autonomic status.

Recurrent syncope due to complete atrioventricular block, a rare presenting symptom of otherwise silent coronary artery disease: successful treatment by PTCA

A patient presented with recurrent syncope and episodes of AV block preceded by asymptomatic ST segment elevation on ambulatory monitoring. Coronary angiography revealed a severe stenosis in the midsegment of the right coronary artery (RCA). Successful PTCA and stent insertion abolished further episodes of syncope.

Multicenter low energy transvenous atrial defibrillation (XAD) trial results in different subsets of atrial fibrillation

OBJECTIVES

This prospective, multicenter trial was aimed at defining efficacy and safety of low energy shocks during atrial fibrillation in a diverse cohort of patients.

BACKGROUND

Experimental studies in sheep and preliminary data in humans have suggested that low energy internal shocks delivered between right atrial and coronary sinus electrode catheters may terminate atrial fibrillation.

METHODS

Biphasic 3/3-ms R wave synchronous shocks were delivered between two electrode catheters in the right atrium and coronary sinus. The defibrillation protocol started with a test shock of 20 V, and shocks increased in 40-V steps until restoration of sinus rhythm or a maximum of 400 V. Shock delivery was withheld after short RR intervals. In 141 patients with atrial fibrillation, the protocol was carried out under sedation in case the shock was associated with discomfort. The atrial arrhythmia was paroxysmal (< or = 7 days) in 50 patients, chronic (> 30 days) in 53, intermediate (> 7 days, < or = 30 days) in 18 and induced in 20. Underlying heart disease was present in 88 patients (62%).

RESULTS

Paroxysmal atrial fibrillation was successfully terminated in 46 (92%) of 50 patients, chronic atrial fibrillation in 37 (70%) of 53, intermediate in 16 (89%) of 18 and induced in 16 (80%) of 20. Mean conversion threshold was 1.8 J (213 V) in the induced group, 2.0 J (229 V) in the paroxysmal group, 2.8 J (272 V) in the intermediate group and 3.6 J (311 V) in the chronic group. The conversion voltage was significantly (p < 0.001) higher in the chronic group than in the other groups of atrial fibrillation and increased significantly with the duration of atrial fibrillation and with left atrial size (p < 0.05). Of 1,779 R wave synchronized shocks delivered with a mean (+/-SD) preceding RR interval of 676 +/- 149 ms, no ventricular arrhythmia was induced. The latter may occur after unsynchronized shocks.

CONCLUSIONS

Low energy transvenous shocks in patients with atrial fibrillation are effective and safe, provided that shocks are properly synchronized to R waves with preceding RR intervals that meet appropriate cycle length criteria. This study provides data that may be useful in the development of an implanted atrial defibrillator.

[Use of PTCA in a gastroepiploic aortocoronary graft]

The use of the gastroepiploic inferior artery as an aortocoronary graft is at present a method of third choice after the mammary artery and venous grafts in revascularizations of the heart muscle. The results are comparable with those obtained with the mammary artery. With regard to the increasing number of operations are more plentiful on the development of atherosclerosis of the above mentioned graft. This dumps the initial enthusiasm that in this artery atherosclerosis does not develop. Reports on PTCA, when this artery is affected, are so far rate. The authors performed a successful PTCA of this graft in a patient with complete affection of the coronary circulation where alternative possibilities of revascularization of the heart muscle were practically exhausted. To improve the technique a suitable type of catheter must be developed which will make it possible to overcome technical problems associated with cannulation of artery and its dilatation.

Effect of digoxin on the ventricular rate variability during paroxysmal atrial fibrillation

This study investigated whether the irregularity of ventricular cycle length during atrial fibrillation (AF) is affected by digoxin. Patients (n = 41) with paroxysmal AF enrolled in a randomized crossover comparison of digoxin and placebo underwent 24-hour ambulatory monitoring during each treatment. Tapes containing AF episodes lasting at least 2 minutes were selected (24 recordings on placebo and 17 on digoxin). The mean (mRR) and standard deviation (SDRR) of RR intervals was calculated for each 30-second segment of AF. The resulting SDRR values were clustered according to bins of mRR values ranging from 350-650 ms in 25-ms steps. In each bin, the SDRR values of all placebo and all digoxin recordings were statistically compared for the top 5, 10, and 15 percentiles of each bin which represented the extremes of ventricular cycle length irregularity during AF. There were no significant differences between the total data of SDRR values in individual bins of mRR. However, the top 5, 10, and 15 percentiles of SDRR values corresponding to mRR values from 350-550 ms were significantly reduced by digoxin (P < 0.0001). The study concludes that although digoxin does not influence the mean variability of RR cycles during AF paroxysms, it suppresses episodes in which a fast ventricular response is associated with extreme variability of RR periods.

Low energy internal cardioversion of atrial fibrillation resistant to transthoracic shocks

OBJECTIVE

To investigate the efficacy of internal cardioversion using low energy shocks delivered with a biatrial electrode configuration in chronic atrial fibrillation resistant to transthoracic shocks.

METHODS

Low energy internal cardioversion was attempted in 11 patients who had been in atrial fibrillation for 233 (SD 193) days and had failed to cardiovert with transthoracic shocks of 360 J in both apex-base and anterior-posterior positions. Synchronised biphasic shocks of up to 400 V (approximately 6 J) were delivered, usually with intravenous sedation only, between high surface area electrodes in the right atrium and the left atrium (coronary sinus in nine, left pulmonary artery in one, left atrium via patent foramen ovale in one).

RESULTS

Sinus rhythm was restored in 8/11 patients. The mean leading edge voltage of successful shocks was 363 (46) V [4.9 (1.2) J]. Higher energy shocks induced transient bradycardia [time to first R wave 1955 (218) ms]. No proarrhythmia or other acute complications were observed.

CONCLUSIONS

Low energy internal cardioversion of atrial fibrillation can restore sinus rhythm in patients in whom conventional transthoracic shocks have failed.

[Reproducibility of signal-averaged electrocardiography]

The reproducibility of the parameters defining the presence of late potentials on the signal-averaged electrocardiogram is one of the limiting factors of the method. The authors studied the coefficients of correlation and reproducibility of these parameters in patients with coronary artery disease. In addition, they tried to determine which parameter was most often responsible for changing a diagnostic conclusion (i.e., presence or absence of late potentials). Two signal-averaged ECGs were recorded one after the other in 127 patients. The presence of late potentials was defined as the presence of a least two of the following criteria: total amplified and averaged QRS duration (tQRS) > 114 ms: duration of the last signal of under 40 microV (LAS) > 38 ms, and root mean square of the amplitude of the last 40 ms (RMS) < 20 microV. The correlation coefficients were 0.98, 0.96 and 0.94 for the duration of tQRS, LAS and RMS respectively (p < 0.0001). The coefficients of reproducibility were 7.0 ms. 7.0 ms and 16.1 microV respectively. Late potentials were present in 22% of patients. A change in diagnosis between the first and second recording was observed in 10 subjects (8% of the population). A combined change in LAS and RMS was responsible for 6 of these revised diagnoses, a change in LAS alone in 2 cases, of the RMS alone in 1 case and the tQRS alone in 1 case. In patients with coronary artery disease, the immediate reproducibility of the diagnosis of late potentials is affected by changes in LAS and RMS. The tQRS is only rarely responsible for a change in diagnosis. This study suggests that the result of the signal-averaged ECG should be interpreted with caution when the LAS or RMS are near their threshold values.

Atrial fibrillation: the last challenge in interventional electrophysiology

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Identification of atrial fibrillation episodes in ambulatory electrocardiographic recordings: validation of a method for obtaining labeled R-R interval files

Current systems for analyzing ambulatory electrocardiograms (ECGs) are unable to distinguish precisely between sinus rhythm and atrial fibrillation (AF) episodes, and are unable to produce RR interval listings that distinguish AF from sinus rhythm on a beat-to-beat basis. We describe a method for obtaining such a computerized listing ("Composite Rhythm" file) from ambulatory recordings containing episodes of AF. The file lists the rhythm of each beat, its real time, and the QRS complex morphology. A visual inspection is made of a full printout of the recording to identify the precise time of onset and termination of each episode of AF. These times are entered into a computer and identified with the corresponding beats on a conventional RR interval file generated by Holter analysis. The method was validated using 1-hour segments from 20 ambulatory ECGs containing 145 episodes of AF. These were visually identified by four independent observers with a mean sensitivity of 99.1%. The first beat of AF was identified concordantly in 96% of episodes, with a discrepancy of < or = 3 beats in the other episodes. The times of 200 selected QRS complexes were then entered into the computer by each observer; 91.1% of these complexes were identified exactly and 100% were identified to within one beat. The Composite Rhythm files have several potential applications for testing AF detection algorithms and studying the mode of onset of AF.

Efficacy and tolerability of transvenous low energy cardioversion of paroxysmal atrial fibrillation in humans

OBJECTIVES

This study investigated the efficacy and tolerability of low energy shocks for termination of atrial fibrillation in patients, using an endocardial electrode configuration that embraced both atria.

BACKGROUND

In animals, low energy biphasic shocks delivered between electrodes in the coronary sinus and right atrium have effectively terminated atrial fibrillation. If human defibrillation thresholds are sufficiently low, atrial defibrillation could be achieved in conscious patients using an implanted device.

METHODS

Twenty-two consecutive patients with stable atrial fibrillation were studied during electrophysiologic testing. Biphasic R wave synchronous shocks were delivered between large surface area electrodes in the coronary sinus and high right atrium, using a step-up voltage protocol starting at 10 or 20 V and increasing to a maximum of 400 V. Patients were conscious at the start of the study and were asked to report on symptoms but were sedated later if shocks were not tolerated.

RESULTS

Cardioversion was achieved in all 19 patients who completed the study, with a mean (+/- SD) leading-edge voltage of 237 +/- 55 V (range 140 to 340) and mean energy of 2.16 +/- 1.02 J (range 0.7 to 4.4). The mean maximal shock delivered without sedation was 116 +/- 51 V (range 60 to 180). No proarrhythmia or mechanical complications occurred.

CONCLUSIONS

The delivery of biphasic R wave synchronous shocks between the high right atrium and coronary sinus can terminate atrial fibrillation with very low energies. General anaesthesia is not required, and a minority of fully conscious patients are able to tolerate this method of cardioversion.

A new pacing algorithm for overdrive suppression of atrial fibrillation. Chorus Multicentre Study Group

Constant rapid pacing may suppress arrhythmias, but it is usually poorly tolerated in the long term. We report a pilot study of a new pacing algorithm for overdrive suppression of atrial premature complexes (APCs) and atrial fibrillation (AF), which prevents postextrasystolic pauses and varies the pacing rate in response to the frequency of APCs. The algorithm was tested in a multiple crossover study for 24 hours in dual chamber pacemakers implanted in 70 patients. Comparison was made on ambulatory recordings between the number of atrial arrhythmias commencing with the algorithm active and inactive. In all cases, the algorithm functioned as designed. No patient was aware of its operation, and no malignant arrhythmias were induced. The 36 recordings that showed atrial arrhythmia were included for analysis. The effects of the algorithm were: APCs (estimated from pacemaker statistics) reduced in 18 patients, increased in 8 (P = 0.02); atrial salvos reduced in 12, increased in 4 (P = 0.041); and AF reduced in 11, increased in 8 (P = NS). In all patients with frequent AF (> 5 episodes in total), fewer episodes occurred when the algorithm was active. We conclude that the algorithm is safe and well tolerated, reduces atrial ectopic activity, and may reduce the frequency of sustained atrial fibrillation.