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.

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.

New trials in atrial fibrillation.

Large-scale clinical trials in atrial fibrillation (AF) now are addressing issues other than that of thromboembolic prophylaxis. The "rate versus rhythm" debated is fundamental--whether to accept the occurrence of AF and attempt control of the ventricular rate or to strive for the restoration and maintenance of sinus rhythm. The AFFIRM, PIAF, and RACE trials will provide information about the efficacy, costs, adverse effects, and benefits of attempting to maintain sinus rhythm. Atrial pacing is associated with less AF than ventricular pacing, and trials (AFT, SYNBIAPACE, and DAPPAF) now are assessing the antiarrhythmic efficacy of atrial pacing, including dual-site pacing and special algorithms compared with no pacing.

Entrapment of an ablation catheter in the cardiac venous system: a case report.

Cannulation of the coronary sinus is a common procedure with infrequent complications. We report an unusual case of a steerable "dumb-bell" catheter passed through the ostium of the coronary sinus prior to an intended radiofrequency ablation procedure becoming stuck and requiring general anesthesia for extraction. We caution against the use of such catheters with a "waist" for the cannulation of the coronary sinus.

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.

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.

Atrial fibrillation: maintenance of sinus rhythm versus rate control.

Atrial fibrillation represents a common and challenging arrhythmia. A rational approach to management of the individual case depends on careful assessment of the temporal of the arrhythmia, any associated cardiovascular disease, and any particular features suggesting the advisability or risks of any particular treatment regimen. The nature of an arrhythmia and of individual patient factors change over time, requiring a flexible approach to long-term treatment that may be defined only after months or years. While new treatment options such as catheter ablation techniques and implantable atrial defibrillators are being tested, old therapies (e.g., low-dose amiodarone) are undergoing reappraisal. Increasing recognition of the dangers of antiarrhythmic therapy used to maintain sinus rhythm is focusing attention on nonpharmacologic methods. All patients with persistent atrial fibrillation merit serious consideration for direct current cardioversion before accepting that atrial fibrillation is permanent, and many patients may benefit from more than one attempt to restore and maintain sinus rhythm.

Heart rate variability depression in patients with unstable angina.

The degree of reduction in heart rate variability (HRV) after myocardial infarction has been shown to have prognostic significance, but HRV has not been studied extensively in patients with unstable angina. We assessed spectral and nonspectral measurements of HRV in 52 patients with unstable angina, 52 patients with acute myocardial infarction, and 41 normal subjects. The spectral bands of 0.04 to 0.15 Hz (low frequency), 0.15 to 0.4 (high frequency), and nonspectral parameters SDNN, SDANN, SDNN index, rMSSD, and pNN50 were calculated from continuous 24-hour ECGs. All measures of HRV were reduced in patients with acute coronary syndromes compared to normal controls (p < 0.001), and there was no significant difference in measure of HRV between unstable angina and myocardial infarction patients. In patients with unstable angina who stabilized after admission, HRV had increased by the second 24 hours of monitoring. In contrast, HRV was further depressed in patients who had episodes of chest pain or transient ST-segment depression during the second 24 hours. rMSSD, pNN50, and SDNN index were lower in patients with unstable angina who had transient silent ischemia compared to those without silent ischemia. Of the patients with unstable angina, 4 died and 1 had nonfatal acute myocardial infarction within 11 months. HRV was lower in these patients than in patients without further cardiac events.

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.

Autonomic pathophysiology in heart failure: carotid baroreceptor-cardiac reflexes.

We evaluated reflex cardiac responses mediated by carotid baroreceptors in 14 patients with treated congestive heart failure and 14 age-matched healthy subjects. We used a neck chamber to deliver two types of pressure change: 5 s of continuous 50-mmHg suction and an R wave triggered, ramped neck pressure-suction sequence. Reflex latencies (functions of baroreflex arc duration) were comparable in heart failure patients and healthy subjects. However, the average maximum baroreflex slope (gain) was less in heart failure patients than healthy subjects (2.0 vs. 3.5 ms/mmHg, P less than 0.010), the R-R interval response range was smaller (91 vs. 188 ms, P = 0.002), and the resting R-R interval position on stimulus-response relation (operational point) was significantly (13 vs. 40%, P = 0.001) closer to threshold. Stepwise regression analysis suggested that baseline R-R interval variability, used as an index of ongoing vagal-cardiac nerve traffic, and the inverse of antecubital vein plasma norepinephrine level, used as an index of sympathetic nerve activity, contributed significantly to the prediction of abnormal carotid baroreceptor-cardiac reflex responses. Thus our results suggest that in heart failure patients, carotid baroreceptor-cardiac reflex abnormalities are related significantly to ongoing abnormalities of vagal and sympathetic cardiovascular outflow.

An antibody against revertant forms of cell-wall deficient bacterial variant in sera from patients with Crohn's disease.

Sera from patients with Crohn's disease or ulcerative colitis, and from controls were examined by indirect immunofluorescence for antibody against two strains of pseudomonas-like cell-wall-defective bacterial variants. Serum samples from 22 of 25 patients with Crohn's disease produced fluorescence of both revertant cell-wall-defective bacterial strains. Intensity of fluorescence correlated positively with the degree of disease activity. Sera from 23 patients with ulcerative colitis and from 15 control subjects did not produce any significant staining of either of the two revertant cell-wall-defective bacterial strains. Absorption of sera with Escherichia coli, Bacteroides thetaiotaomicron, and Pseudomonas aeruginosa did not alter the intensity of fluorescence in patients with Crohn's disease, whereas similar absorption of sera from patients with ulcerative colitis and controls abolished the slight staining of cell-wall-defective strains produced by 29% of unabsorbed serum samples.