Biomedical subjects
Publications and source records attributed to A B Wagshal.
A case of atrial fibrillation with asystole was diagnosed as ventricular fibrillation because of the autogain feature of the electrocardiographic monitor. Direct current shock therapy was withheld only because the patient regained consciousness.
A patient presented with atrial tachycardia. The work-up, guided by the tachycardia morphology, led to the diagnosis of left atrial appendage aneurysm. Surgical removal of the atrial appendage resulted in cure of the tachycardia and associated symptoms.
INTRODUCTION: Although accelerated junctional rhythm (AJR) is a known marker for successful slow pathway (SP) ablation sites, AJR may just be a regional effect of the anisotropic conduction properties of this area of the heart. We believe that detailed assessment of the AJR might provide insight into the SP specificity of this AJR and perhaps the nature of the SP itself. METHODS AND RESULTS: Our ablation protocol consisted of 30-second, 70 degrees C temperature-controlled ablation pulses with assessment after each pulse. Serial booster ablations were performed at the original successful site and at least 2 to 3 nearby sites to assess for residual AJR after the procedure in 50 consecutive SP ablations. We defined three distinct patterns of AJR: continuous AJR that persisted until the end of energy delivery (group I, 25 patients); alternating or "stuttering" AJR that persisted throughout energy delivery (group II, 9 patients); and AJR that ended abruptly during energy delivery (group III, 16 patients). Mean ablation temperatures in the three groups was 57 degrees+/-5 degrees C, 54 degrees+/-5 degrees C, and 63 degrees+/-5 degrees C, respectively (P = 0.0002 for groups I and II vs group III). Ten of 34 (29%) patients in groups I and II ("low-temperature ablation") exhibited residual SP (jump and/or single echo beats) despite tachycardia noninducibility, and 25 of 34 (73%) patients had residual AJR during the booster ablations, but neither of these was seen in any group III patients. CONCLUSION: Ablation temperature correlates with the pattern of AJR produced during SP ablation. That higher temperature lesions simultaneously abolish all SP activity as well as the focus of AJR suggests that this AJR is specific for the SP and is not a nonspecific regional effect.
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Previous studies have reported only short-term (6 to 10 months) follow-up after ablation of atrioventricular (AV) nodal reentrant tachycardia by using the anterior approach. The objective of this study was to determine the long-term efficacy and safety of radiofrequency catheter ablation of AV nodal reentrant tachycardia with the anterior-approach method. In 56 patients (16 men and 40 women; mean [+/-SD] age, 44 +/- 19 years) with symptomatic AV nodal reentrant tachycardia. In 53 patients, ablation was performed initially by using a standard 7F, 2 mm-tipped tripolar His bundle catheter when the large-tip electrode was not as available, and in the remaining 3 patients, ablation was performed with a 7F, 4 mm-tipped catheter. Ablation was successful in the short term in 53 (95%) patients after a median of 7 radiofrequency applications. Three (5%) patients developed complete AV block immediately after ablation. Six (11 %) patients had recurrence of tachycardia within 3 months (n = 5) and 13 months (n = 1) after ablation. Repeated ablation resulted in successful outcome in 4 patients and in complete AV block in 1 patient; the other patient refused a repeated ablation attempt. A total of 51 patients was monitored for 36 +/- 12 months (range, 25 to 72 months), and none had tachycardia recurrence or delayed AV block. In conclusion, our results show that the anterior approach to radiofrequency catheter ablation can be used successfully to treat patients with AV nodal reentrant tachycardia with a good long-term efficacy and safety.
Unsuspected cardiac complications have been occasionally identified on postablation echocardiographic studies; however, the clinical utility of route echocardiographic studies following uncomplicated radiofrequency catheter ablation procedures has not been established. Two-dimensional/Doppler echocardiographic studies obtained preablation (within 3 months of the procedure) in 355 consecutive patients (180 males and 175 females, mean age 37 +/- 21 years) were compared to postablation (within 24 hours of the procedure) studies obtained after a total of 387 uncomplicated RF catheter ablation procedures for AV node slow pathway (n = 120), accessory AV pathways (n = 214), and complete AV junction (n = 39). Postablation studies identified 6 new cases (1.5%) of new wall motion abnormalities, and 3 additional patients had septal wall motion abnormalities during ventricular pacing. LVEF remained unchanged from baseline (62 +/- 10 vs 62 +/- 11). A small pericardial effusion was detected after 11 procedures (2.8%), and there were 9 (2.3%), 21 (5.4%), and 20 (5.2%) new findings of mild (1+) aortic, mitral, and tricuspid regurgitation, respectively; and no cases of significant valvular dysfunction in any patient. There were no new cases of cavity thrombus. There was no clear relationship between postablation echocardiographic findings and the type and approach to ablation, and no patient had any clinical sequelae possibly related to any of the new echocardiographic findings during a mean follow-up of 15 +/- 6.0 months (range 1-26 months). Routine transthoracic echocardiographic studies after uncomplicated RF catheter ablation procedures identify occasional minor abnormalities that (1) may or may not be procedure related, (2) are of no apparent clinical consequence, and (3) thus appear to be of limited value.
Radiofrequency energy has emerged as the current energy source of first choice for ablation procedures. We review the development of radiofrequency energy for ablation procedures and its advantages and disadvantages. We also review how radiofrequency energy can be applied to treat various arrhythmias. We also discuss some of the insights that catheter ablation has in turn provided in our understanding of arrhythmias.
We assessed the usefulness of routine follow-up electrophysiologic studies after successful catheter ablation for supraventricular tachycardia and the role of event monitoring as an alternative modality in 310 patients at 11 centers using an investigational catheter ablation system with closed-loop temperature control. A routine follow-up electrophysiologic study between 1 and 3 months after ablation was required as part of the study protocol, and patients developing palpitations after ablation were encouraged to use event monitors. Recurrence of the initially targeted arrhythmia developed in 23 patients (7.4%) at a mean of 1.5 +/- 1.5 months after ablation. However, only 2 of these 23 recurrences were discovered by routine follow-up electrophysiologic study in asymptomatic patients (both with concealed accessory pathways); in the remaining 21 patients a positive follow-up electrophysiologic study was heralded by either recurrent symptoms, documented recurrent supraventricular tachycardia, and/or preexcitation on the electrocardiogram. Eighteen patients complained of palpitations after ablation and received an event monitor, which correctly diagnosed another cause of palpitations and ruled out recurrence of the ablated arrhythmia in 8 patients. Thus, the combination of clinical follow-up and event monitoring appears to be an effective alternative to routine follow-up electrophysiologic studies after catheter ablation of supraventricular tachycardia.
CABG is associated with many perioperative complications, including supraventricular and ventricular arrhythmias and conduction disturbances. Atrial fibrillation occurs in < or = 40% of patients after CABG and is especially common in older patients. Although it is often benign and self-limited, it can lead to complications such as stroke. Treatment consists primarily of control of the ventricular response rate; in some cases, antiarrhythmic drugs or electrical cardioversion are needed. Anticoagulation should be considered in appropriate cases of persistent (48 to 72 hours) atrial fibrillation after initial treatment. Prophylaxis, especially with beta-blocking agents, seems to be effective and should be considered in appropriate cases. Simple ventricular arrhythmias are common after CABG and do not affect the patient's prognosis; however, sustained VT/VF occur infrequently (< 2% of patients) and carry a high mortality rate. Treatment is aimed at correcting precipitating factors (e.g., myocardial ischemia). Electrophysiologically guided drug therapy and implantation of an ICD should be considered in appropriate cases for patients who survive the initial events. Transient minor conduction disturbances are common after CABG; in some patients persistent AV block and sinus node dysfunction develop and may require treatment with permanent pacemaker.
The ability of single paced ventricular beats during tachycardia to penetrate the tachycardia circuit and reset the subsequent atrial depolarization (atrial preexcitation), enabling calculation of the "preexcitation index," can be helpful in analyzing supraventricular tachycardias. However, the ventricular refractory period often prevents ventricular capture of beats with the necessary prematurity to demonstrate atrial preexcitation, particularly in atrioventricular nodal reentrant tachycardia (AVNRT). We hypothesized that the use of double premature stimuli could overcome this limitation. In 25 consecutive patients with either AVNRT or atrioventricular reciprocating tachycardia (AVRT) we attempted to demonstrate atrial preexcitation with single and double ventricular extrastimuli. Whereas atrial preexcitation with a single extrastimulus could only be achieved in 3 of 11 patients with AVNRT, all but 1 patient demonstrated atrial preexcitation with the use of double ventricular extrastimuli. On the other hand, in all but 1 patient with AVRT, atrial preexcitation could be achieved with single and double extrastimuli. A formula was derived for obtaining a preexcitation index with double extrastimuli and shown to correspond closely with the preexcitation index obtained with a single extrastimulus in the 16 patients in whom atrial preexcitation could be achieved with single and double extrastimuli. Thus, this technique significantly enhances the ability to achieve atrial preexcitation and to calculate the preexcitation index in patients with AVNRT, and thus may be useful in deciphering tachycardia mechanism in some patients, as well as being a useful technique in studying the electrophysiological properties of the antegrade and retrograde limbs of AVNRT.
Although radiofrequency catheter ablation has undergone explosive growth as the treatment for a variety of arrhythmias, a limiting factor with the existing catheter delivery system has been the relatively small size of the lesions, which appears to be in part due to coagulum formation around the catheter tip, producing a rise in impedance and limiting energy delivery. In order to test the hypothesis that infusion of saline during radiofrequency current application can increase the lesion size and decrease the incidence of impedance rise, ten dogs were each given two radiofrequency ablation lesions to the left ventricular endocardium. One of these lesions was delivered with a standard 7 French quadripolar catheter with a 2-mm tip, and the second was done with a 7 French luminal electrode catheter (also with a 2-mm tip) for the infusion of normal saline during the delivery of radiofrequency energy. Energy was delivered for 60 seconds at either 10 or 20 watts at two distinct sites in the left ventricle for each animal. Four to 7 days following ablation, the animals were sacrificed for pathological examination. The lesions created with the saline infusion catheter were significantly bigger than those produced with a standard catheter (7.3 x 7.0 x 5.1 vs 5.2 x 4.9 x 3.5 mm, respectively, P < 0.001). At the lower energy level (10 W), none of the animals with the saline infusion catheter experienced an impedance rise versus 3 of 5 of the animals in whom the standard catheter was used.(ABSTRACT TRUNCATED AT 250 WORDS)
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Successful lesion formation using radiofrequency energy requires adequate tissue heating. Temperature monitoring during ablation may thus improve the efficiency of radiofrequency catheter ablation. Each of five anesthetized, closed-chest adult mongrel dogs weighing 19 to 24 kg received a single pulsed ablation at four left ventricular and two right ventricular sites using a thermistor-tipped 2 mm electrode catheter. The maximum temperature at the electrode-tissue interface was preset at 90 degrees C and current delivered for 40 seconds (method A) or at 70 degrees C for 40 seconds (method B1) or 80 seconds (method B2). With method C, the temperature was set at 90 degrees C for 20 seconds, after which the temperature setting was turned off and ablation continued until impedance increased or the temperature reached > or = 100 degrees C. The size of the resultant lesion was greater with method A than with methods B1, B2 or C (mean length x width x depth, 5.6 x 4.8 x 6.5 vs 4.1 x 4.0 x 5.1 vs 4.2 x 4.0 x 5.2 vs 5.0 x 4.3 x 5.7 mm, respectively; p < 0.01). There was no significant difference in lesion size between pulse durations of 40 seconds (group B1) and 80 seconds (group B2). Only two ablations, both in the anteroapical right ventricle, resulted in a marked rise in impedance without the temperature reaching > or = 100 degrees C. We conclude that temperature (and thus impedance) monitoring improves control and efficacy of lesion formation during radiofrequency catheter ablation.
A healthy 37-year-old male presented with a history of frequent palpitations and sustained wide QRS complex tachycardia with a right bundle branch block and left axis morphology. Serial electrophysiological studies revealed two inducible tachycardias, which were shown to represent atrioventricular nodal reentrant tachycardia and idiopathic left ventricular tachycardia. Transformation from one tachycardia to the other occurred spontaneously as well as following atrial or ventricular pacing. Radiofrequency catheter ablation of the slow atrioventricular nodal pathway resulted in cure of atrioventricular nodal reentrant tachycardia and the prevention of spontaneous recurrence of ventricular tachycardia, suggesting a role of atrioventricular nodal reentrant tachycardia in triggering the clinical episodes of ventricular tachycardia. The patient has remained asymptomatic without antiarrhythmic therapy for 8 months.
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Radiofrequency catheter ablation of the atrioventricular junction is usually achieved from either the right or left atrioventricular junction. We describe a new approach in which the atrioventricular junction was successfully ablated from the supravalvular region of the noncoronary cusp of the aortic valve in an unusual patient in whom conventional approaches were unsuccessful.
In patients presenting with sustained ventricular tachyarrhythmias, when oral quinidine monotherapy fails as determined by programmed electrical stimulation, the degree of benefit observed with combination therapy with mexiletine is debated. We prospectively studied 20 consecutive patients (16 men and 4 women) aged 33 to 77 years (mean age, 62 +/- 11 years) who were treated with maximally tolerated quinidine and mexiletine combination therapy and who had ventricular tachyarrhythmias induced at baseline and during oral quinidine monotherapy. Coronary artery disease was present in 19 patients (95%). Programmed electrical stimulation was performed at 2 drive train cycle lengths with up to 3 extrastimuli at two ventricular sites. During follow-up study with combination quinidine-mexiletine therapy ventricular tachyarrhythmias were rendered noninducible in four patients (20%). The remaining 16 patients showed a significant slowing of their tachycardia cycle length (267 +/- 56 msec baseline vs 320 +/- 75 msec with quinidine vs 345 +/- 53 msec with combination therapy, p < 0.05). There was also an increase in the mean QTc interval (452 +/- 50 msec baseline vs 477 +/- 79 msec after quinidine vs 486 +/- 65 msec with combination quinidine-mexiletine therapy, p = not significant) and in the mean ventricular effective refractory period (246 +/- 25 msec baseline vs 281 +/- 37 msec after quinidine vs 290 +/- 25 msec with combination quinidine-mexiletine therapy, p < 0.05). We conclude that sustained ventricular tachyarrhythmias induced during quinidine monotherapy were rendered noninducible by oral combination therapy with quinidine-mexiletine in 20% of cases.(ABSTRACT TRUNCATED AT 250 WORDS)