Alan B. Wagshal

Arrhythmias and conduction disturbances after coronary artery bypass graft surgery: Epidemiology, management, and prognosis

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 patients 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.

Use of the Saline Infusion Electrode Catheter for Improved Energy Delivery and Increased Lesion Size in Radiofrequency Catheter Ablation

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 Iuminal 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 × 7.0 × 5.1 vs 5.2 × 4.9 × 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. At the higher level (20 W), only 1 of 5 dogs had an impedance rise with the saline infusion catheter versus 5 of 5 with the standard catheter. We conclude that the use of a saline infusion catheter for radiofrequency energy delivery during catheter ablation produces a significantly larger lesion than that produced with a standard catheter and is effective in preventing impedance rise.

Cardiovascular complications after radiofrequency catheter ablation of supraventricular tachyarrhythmias

Abstract We report the incidence of cardiovascular complications in patients receiving RF catheter ablation for supraventricular tachyarrhythmias. To reduce the incidence of complications, a rigid guideline or policy for the personnel and facilities should be followed. A prospective, multicenter registry program may be needed to further define the complications associated with this procedure.

Electrophysiological effects of propofol on the normal cardiac conduction system.

To determine the electrophysiological effects of propofol and to explain the potential mechanism(s) whereby it causes bradyarrhythmias, 10 closed-chest pigs weighing 20-25 kg were studied. Each animal was premedicated by intramuscular administration of ketamine hydrochloride, intubated, and mechanically ventilated. Femoral arterial and venous catheters were placed, and a comprehensive electrophysiologic evaluation was performed at baseline and after two doses (1 mg/kg i.v. bolus and 0.1 mg/kg/min infusion and an extra 1- mg/kg i.v. bolus and 0.2 mg/kg/min infusion) of propofol. The electrophysiological effects obtained on low-and high-dose propofol were compared to baseline values. Propofol caused a dose-related decrease in sinus cycle length (baseline 565 +/- 36 ms, low-dose propofol 541 +/- 28, high-dose propofol 527 +/- 26 ms; p < 0.05), a prolongation of the corrected sinus node recovery time (baseline 119 +/- 35 ms, low-dose propofol 126 +/- 32, high-dose propofol 130 +/- 30 ms; p < 0.01), and an increase in the His-ventricular interval (baseline 33 +/- 4 ms, low-dose propofol 36 +/- 4, high-dose propofol 40 +/- 3 ms; p < 0.005). All other electrophysiological parameters remained unchanged, and there were no cases of spontaneous atrioventricular block or sinus pauses. We conclude that propofol causes dose-related depression of sinus node and His-Purkinje system functions, but has no effect on the atrioventricular node function and on the conduction properties of atrial and ventricular tissues in normal pig hearts.

Coincident Idiopathic Left Ventricular Tachycardia and Atrioventricular Nodal Reentrant Tachycardia: Control by Radiofrequency Catheter Ablation of the Slow Atrioventricular Nodal Pathway

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.

Radiofrequency Catheter Ablation of the Atrioventricular Junction by a Supravalvular Noncoronary Aortic Cusp Approach

Radiofrequency catheter ablation of the atrioventricular janction 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.

Clinical Utility of Routine Transthoracic Echocardiographic Studies After Uncomplicated Radiofrequency Catheter Ablation: A Prospective Multicenter Study

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.

Ventricular Lead Transection and Atrial Lead Damage in a Young Softball Player Shortly After the Insertion of a Permanent Pacemaker

We report a case in which permanent pacemaker implantation using a conventional subclavian approach on the throwing side of an avid Softball player resulted in complete transection of the ventricular lead and severe damage to the atrial lead. The site of the lead fracture suggested that both leads were crushed between the clavicle and the first rib as a result of the frequent and repetitive arm movement. This case illustrates the importance of the selection of the correct approach for permanent pacing lead insertion.

Temperature-guided radiofrequency catheter ablation of closed-chest ventricular myocardium with a novel thermistor-tipped catheter

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.

Use of Double Ventricular Extrastimulation to Determine the Preexcitation Index in Atrioventricular Nodal Reentrant Tachycardia

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.