Successful external cardioversion of atrial fibrillation in patients referred to an electrophysiologist for internal cardioversion

BACKGROUND

Internal cardioversion of atrial fibrillation with direct current energy has become an increasingly employed technique for patients who fail external cardioversion.

HYPOTHESIS

The purpose of this study was to determine whether internal cardioversion could be avoided by careful attention to cardioversion technique in a group of patients referred specifically for internal cardioversion after failed external cardioversion by community cardiologists.

METHODS

We performed external cardioversion utilizing two operators applying significant pressure to the thorax with up to 360 J prior to the planned internal cardioversion in 20 patients referred for internal cardioversion after failed attempts at external cardioversion.

RESULTS

Sixteen patients (80%) were successfully cardioverted and avoided the risk, inconvenience, and cost of internal cardioversion.

CONCLUSION

External cardioversion with significant anterior paddle pressure by two operators can decrease the need for internal cardioversion in a significant portion of patients referred to electrophysiologists for internal cardioversion and should be considered prior to an invasive procedure.

Changes in heart rate and heart rate variability before ambulatory ischemic events(1)

OBJECTIVES

The aim of this study was to determine the time course of autonomic nervous system activity preceding ambulatory ischemic events.

BACKGROUND

Vagal withdrawal can produce myocardial ischemia and may be involved in the genesis of ambulatory ischemic events. We analyzed trajectories of heart rate variability (HRV) 1 h before and after ischemic events, and we examined the role of exercise and mental stress in preischemic autonomic changes.

METHODS

Male patients with stable coronary artery disease (n = 19; 62.1 +/- 9.3 years) underwent 48-h ambulatory electrocardiographic monitoring. Frequency domain HRV measures were assessed for 60 min before and after each of 68 ischemic events and during nonischemic heart rate-matched control periods.

RESULTS

High-frequency HRV decreased from -60, -20 to -10 min before ischemic events (4.8 +/- 1.3; 4.6 +/- 1.3; 4.4 +/- 1.2 ln [ms(2)], respectively; p = 0.04) and further from -4, -2 min, until ischemia (4.4 +/- 1.3; 4.1 +/- 1.3; 3.7 +/- 1.2 ln [ms(2)]; p's < 0.01). Low frequency HRV decreases started at -4 min (p < 0.05). Ischemic events occurring at high mental activities were preceded by depressed high frequency HRV levels compared with events at low mental activity (p = 0.038 at -4 min, p = 0.045 at -2 min), whereas the effects of mental activities were not observed during nonischemic control periods. Heart rate variability measures remained significantly decreased for 20 min after recovery of ST-segment depression when events were triggered by high activity levels.

CONCLUSIONS

Autonomic changes consistent with vagal withdrawal can act as a precipitating factor for daily life ischemia, particularly in episodes triggered by mental activities.

Atypical atrial flutter originating in the right atrial free wall

BACKGROUND

Data from experimental models of atrial flutter indicate that macro-reentrant circuits may be confined by anatomic and functional barriers remote from the tricuspid annulus-eustachian ridge atrial isthmus. Data characterizing the various forms of atypical atrial flutter in humans are limited.

METHODS AND RESULTS

In 6 of 160 consecutive patients referred for ablation of counterclockwise and/or clockwise typical atrial flutter, an additional atypical atrial flutter was mapped to the right atrial free wall. Five patients had no prior cardiac surgery. Incisional atrial tachycardia was excluded in the remaining patient. High-density electroanatomic maps of the reentrant circuit were obtained in 3 patients. Radiofrequency energy application from a discrete midlateral right atrial central line of conduction block to the inferior vena cava terminated and prevented the reinduction of atypical atrial flutter in each patient. Atrial flutter has not recurred in any patient (follow-up, 18+/-17 months; range, 3 to 40 months).

CONCLUSIONS

Atrial flutter can arise in the right atrial free wall. This form of atypical atrial flutter could account for spontaneous or inducible atrial flutter observed in patients referred for ablation and is eliminated with linear ablation directed at the inferolateral right atrium.

Frozen shoulder syndrome associated with subpectoral defibrillator implantation

Pectoral implantation of transvenous non-thoracotomy internal cardioverter defibrillators (ICD) has resulted in very few complications whether placed subpectorally or subcutaneously. We report the case of a 68 year old man with a subpectorally implanted MINI-plus (Cardiac Pacemakers, Incorporated, St. Paul, Mn.) transvenous ICD who developed nearly instantaneous severe ipsilateral shoulder pain and immobilization. The symptoms progressed despite aggressive physical therapy. We elected to remove the device from the pectoral site and place it in a traditional abdominal position due to the severity, duration and refractoriness of his symptoms. This procedure utilized the chronic Endotak DSP (Model 0125, Cardiac Pacemakers, Incorporated) transvenous lead, a compatible Endotak DSP lead extender (Model 6952, Cardiac Pacemakers, Incorporated) and the above described ICD. Immediate relief of symptoms was accomplished by relocation of the device to an abdominal site. This intervention should be reserved for patients with severely debilitating symptoms. Prospective comparison of subpectoral and subcutaneous surgical approaches with respect to patient comfort and acceptance and complications may be warranted.

Retrograde fast pathway ablation for atrioventricular nodal reentry associated with markedly prolonged PR intervals

Three patients with typical atrioventricular nodal reentrant tachycardia (AVNRT) and markedly prolonged PR intervals (>300 ms) without dual pathway physiology at baseline or during isoproterenol infusion underwent successful fast pathway ablation and remained asymptomatic without recurrent AVNRT, atrioventricular block, or symptomatic bradycardia for a mean of 19 months. In patients with recurrent AVNRT and markedly prolonged PR intervals, selective ablation of the retrograde fast pathway can eliminate AVNRT without further impairment of anterograde atrioventricular nodal function.

Atrial fibrillation after radiofrequency ablation of type I atrial flutter: time to onset, determinants, and clinical course

BACKGROUND

The occurrence of atrial fibrillation after ablation of type I atrial flutter remains an important clinical problem. To gain further insight into the pathogenesis and significance of postablation atrial fibrillation, we examined the time to onset, determinants, and clinical course of atrial fibrillation after ablation of type I flutter in a large patient cohort.

METHODS AND RESULTS

Of 110 consecutive patients with ablation of type I atrial flutter, atrial fibrillation was documented in 28 (25%) during a mean follow-up of 20.1+/-9.2 months (cumulative probability of 12% at 1 month, 23% at 1 year, and 30% at 2 years). Among 17 clinical and procedural variables, only a history of spontaneous atrial fibrillation (relative risk 3.9, 95% confidence intervals 1.8 to 8.8, P=0.001) and left ventricular ejection fraction <50% (relative risk 3.8, 95% confidence intervals 1.7 to 8.5, P=0.001) were significant and independent predictors of subsequent atrial fibrillation. The presence of both these characteristics identified a high-risk group with a 74% occurrence of atrial fibrillation. Patients with only 1 of these characteristics were at intermediate risk (20%), and those with neither characteristic were at lowest risk (10%). The determinants and clinical course of atrial fibrillation did not differ between an early (< or = 1 month) compared with a later onset. Atrial fibrillation was persistent and recurrent, requiring long-term therapy in 18 patients, including 12 of 19 (63%) with prior atrial fibrillation and left ventricular dysfunction.

CONCLUSIONS

Atrial fibrillation after type I flutter ablation is primarily determined by the presence of a preexisting structural and electrophysiological substrate. These data should be considered in planning postablation management. The persistent risk of atrial fibrillation in this population also suggests a potentially important role for atrial fibrillation as a trigger rather than a consequence of type I atrial flutter.

Alterations in heart rate following radiofrequency ablation in the treatment of reentrant supraventricular arrhythmias: relation to alterations in autonomic tone

To determine the relation between the creation of endocardial lesions and alterations in autonomic tone, we analyzed heart rate variability in patients undergoing radiofrequency catheter ablation for symptomatic supraventricular tachycardia. Elevated heart rates are frequently noted after radiofrequency catheter ablation for supraventricular arrhythmias. It has been postulated that this elevation may be secondary to alterations in cardiac autonomic tone. Since heart rate variability is a measure of autonomic nervous system activity, we used this technique to examine the heart rate elevation and to characterize postablation autonomic changes. Thirty-eight patients undergoing 44 radiofrequency catheter ablation procedures were included in the study. Total arrhythmic substrates treated included 34 accessory pathways and 13 AV nodes with dual physiology. Twenty-four hour ambulatory electrocardiographic recordings were obtained in a drug-free state prior to, ablation early postablation, and late postablation. Spectral and nonspectral analyses of heart rate variability were performed. Subgroup analyses were also done on specific cohorts. Subgroups included patients undergoing accessory pathway ablations, AV node modifications, and ablation of septal and nonseptal targets. To determine whether the amount of tissue damage was related to changes in heart rate variability, we analyzed the relation between the total energy delivered to the endocardium and the peak change in creatine kinase and heart rate variability. In this population, a significant transient increase in heart rate was noted following radiofrequency ablation. All time and frequency domain parameters of heart rate variability showed significant reversible decreases. These changes were independent of target site and arrhythmia substrate. There was no correlation noted between the changes in heart rate variability and either the total amount of energy applied to the endocardium or the change in creatine kinase. Increased heart rates and decreased heart rate variability occur following radiofrequency catheter ablation for supraventricular tachycardia. Clinically, the predominant effect is that of decreased parasympathetic tone. Since these transient changes are independent of arrhythmic substrate or ablation site in the atria, a rich parasympathetic innervation of the heart is proposed.

Successful ablation of a nonreentrant dual atrioventricular nodal tachycardia

Selective radiofrequency catheter ablation of the slow pathway of the AV node has become the treatment of choice for AV nodal reentrant tachycardia. We describe a case of a nonreentrant AV nodal tachycardia and its successful treatment by slow pathway ablation.

Implantation of a nonthoracotomy defibrillator using a second defibrillator patch in the abdominal pocket

Successful implantation of a biphasic nonthoracotomy implantable cardioverter defibrillator may not be achieved with a conventional system. We describe a successful device implantation using a pectoral and abdominal patch electrode system.

Supraventricular tachycardia precipitated by a peripherally inserted central catheter

Central venous catheters extending into intracardiac chambers can provoke premature atrial and ventricular complexes, which have been reported to initiate supraventricular tachyarrhythmias. These catheters are traditionally placed via the femoral, subclavian, or internal jugular veins. A new alternative to the conventional central catheter for patients requiring access to large veins is the peripherally inserted central (PIC) catheter. Since its proximal end is of small caliber, a PIC catheter can be mistaken for a peripheral intravenous catheter. The distal end, however, usually extends into the superior vena cava and may be erroneously advanced into intracardiac chambers. The authors report a case of a PIC catheter precipitating supraventricular reentrant tachycardia in a previously asymptomatic patient.