Bipolar Tined Polyurethane Ventricular Lead: A Four-Year Experience

With the advent of polyurethane as an insulating material for permanent pacemaker leads, concern has arisen over the integrity and long-term durability of polyurethane-insulated pacing leads. Specific concern has arisen over particular bipolar tined polyurethane ventricular leads. We have assessed our 4-year experience with this lead. This experience involves two groups of patients, those with leads manufactured before a certain date and those with leads manufactured at a later date. In the first group (judged to be at increased risk) the failure rate was 8.8%, and in the second group (judged not to be at increased risk) the rate was 3.9%. Lead failure occurred at an average of 17.5 months in the first group. Adequate follow-up on the second group is not available to determine whether or not the failure rate may eventually be as high as that in the early group. Actuarial analysis suggests that survivorship free of lead failure is probably not significantly different in the two groups. This experience points out the need for determining lead failure rates, identifying optimal lead design and configuration, and establishing a lead registry or mechanism by which the integrity of various pacing leads can be evaluated.     

A Multicenter Experience with a Bipolar Tined Polyurethane Ventricular Lead

A multicenter study was undertaken to determine the failure rate of a specific polyurethane bipolar tined pacing lead, the Medtronic 4012 pacing lead. Six centers in the United States and Canada implanted 1,190 Medtronic 4012 pacing leads. The study was designed to determine the probability and clinical manifestations of lead failure. Only failures compatible with an insulation problem were included. The probability of a 4012 lead failure by Kaplan-Meier analysis was 20.9% at 6 years after implantation. Failures were manifested as sensing abnormalities, failure to capture, early battery depletion, and significant decrease in measured impedance compared with the previous impedance measurements. Of the 95 definite lead failures, 16 (16.8%) were associated with symptoms similar to those experienced before pacemaker placement. The observed failure rate is unacceptable, and strong consideration should be given to replacing the 4012 pacing lead in pacemaker-dependent patients and closely monitoring nondependent patients.     

Multicenter Experience With a Bipolar Tined Polyurethane Ventricular Lead

A multicenter study was undertaken to determine the failure rate of a specific bipolar tined polyurethane ventricular pacing lead, the Medtronic 4004/4004M pacing lead. Seven centers in the United States and Canada implanted 586 Medtronic 4004/4004M pacing leads. The study was designed to determine the probability and clinical manifestations of lead failure. Only failures compatible with an insulation problem were included. The Kaplan-Meier estimate of the percentage of 4004/4004M lead failures within 4 years after implantation was 14.1% (95% confidence interval: 8.5%–19.3%). Failures were manifested as sensing abnormalities, failure to capture, early battery depletion, and significant decrease in measured impedance compared with previous impedance measurements. The observed rate of failure is unacceptable, and strong consideration should be given to replacing the 4004/4004M pacing lead in pacemaker dependent patients and closely monitoring nondependent patients.     

Comparison of Lead Complications with Polyurethane Tined, Silicone Rubber Tined, and Wedge Tip Leads: Clinical Experience with 822 Ventricular Endocardial Leads

Lead-related complications have been prospectively studied for 602 unipolar tined endocardial ventricular pacemaker leads implanted over a five-year period. No differences were noted in overall complication rates between 238 polyurethane insulated leads (4.2%) and 364 silicone rubber insulated leads (3.6%). Comparing the total series of 602 tined leads to a retrospective survey of 220 wedge tip leads, a marked reduction in dislodgements (0.3% vs. 7.7%, P<0.001) and reoperations (2.0% vs. 15.0%, P<0.001) was found using tined leads. We conclude that tined ventricular leads are far superior to wedge tip leads with respect to lead complications.     

Elimination of Lead Dislodgement by the Use of Tined Transvenous Electrodes

Pacemaker lead dislodgement has accounted for a large proportion of the postoperative complications seen after transvenous pacemaker insertion. Ninety-two patients underwent implantation of a tined transvenous electrode over a three-year period without a single dislodgement. Excellent thresholds were obtained and no difficulties related to electrode insertion were encountered. Tined transvenous pacemaker leads are preferred for routine use at this time.     

Polyurethane Sheath Disintegration Causing Impaction of Pacer Lead and Shock during Attempted Removal

Steady traction to remove a lead whose polyurethane sheath had disintegrated caused displacement of the heart and caused hypotension; the bared lead uncoiled and impacted in the wall of the subclavian vein. The tension on the intrathoracic lead was relieved via immediate anterior thoracotomy and compartmentalization of the superior vena cava.     

Repetitive Ventricular Responses Induced by Radiofrequency Ablation for Idiopathic Ventricular Tachycardia Originating from the Outflow Tract of the Right Ventricle

In 23 consecutive patients, radiofrequency (RF) ablation was used as treatment for idiopathic ventricular tachycardia (VT) originating from the outflow tract of the right ventricle. In this study, we focused on the repetitive ventricular response (> 5 consecutive QRS beats during RF application). The incidence and clinical implications of the repetitive ventricular response were examined through the results of endocardial mapping and RF ablation. VT origin was mapped as the earliest activation site during VT, and it was determined within 0.5 × 0.5 cm (narrow site) in 13 patients and wider than 0.5 × 0.5 cm (wide origin) in the other 10 patients. The repetitive ventricular response was induced during application of RF current in 14 of 23 patients (61%), and it was more frequently observed in VT from a wide origin (100%) than in the VT from a narrow site (31%). The QRS morphology of the repetitive ventricular response was identical to that of clinical VT. As RF application was continued and/or repeated, the RR interval of the repetitive ventricular response was gradually prolonged, the number of consecutive QRS complexes was decreased, and clinical VT was finally eliminated. The overall success rate of RF ablation was 96% (22/23 patients), and no complications were observed. In conclusion, a repetitive ventricular response was frequently observed in idiopathic right VT. The changing pattern of repetitive ventricular response, slowing, and/or disappearing was consistent with successful RF ablation.     

Clinical Surveillance of an Active Fixation, Bipolar, Polyurethane Insulated Pacing Lead, Part II: The Ventricular Lead

Since 1989, 72 Telectronics 330–201 active fixation, polyurethane insulated ventricular leads (Accufix) have been implanted at the Mayo Clinic. There were four (5.6%) acute lead related complications (perforation, microdislodgment, and macrodislodgment), three of which led to early reoperation. Over a follow-up time of up to 2.7 years (median 9.4 months), there were six (8.3%) chronic lead related complications but no failures of lead material. Most of these complications developed during the first month, and half of them were transient, with documented improvement later. Two patients (2.6%) required reoperation for chronic complications. At follow-up examination of the pacing thresholds, usually performed about 3 months after implantation, 14.3% of the examined patients had high pacing thresholds necessitating high-output programming. The mechanisms and later evolution of this phenomenon should be further evaluated.     

Recurrent Polymorphic Ventricular Tachycardia Complicating Radiofrequency Catheter Ablation of the Atrioventricular Junction

Recurrent ventricular tachycardia and ventricular fibrillation were observed immediately after RF ablation of the AV junction in a 64-year-old man. This arrhythmia was preceded by ventricular bigeminy and a long-short sequence. It was not associated with prolongation of the QT interval compared to baseline, and recurred 3 months later despite ventricular pacing at 90 beats/min. This is the first reported case of sustained ventricular arrhythmia complicating RF AV junction ablation despite rapid ventricular pacing, and recurring 3 months after discharge. It may explain the rare cases of sudden death complicating this procedure.     

Ventricular Fibrillation Triggered during and after Radiofrequency Energy Delivery to the Site of Origin of Idiopathic Right Ventricular Outflow Tract Arrhythmia

We observed a case of idiopathic ventricular arrhythmias originating from the right ventricular outflow tract (RVOT). The origin of target premature ventricular contraction (PVC) and nonsustained ventricular tachycardia (VT) was within a wide low‐voltage area around the RVOT. During radiofrequency (RF) application to the site of arrhythmia origin, polymorphic VT and ventricular fibrillation were repeatedly triggered by new PVC that had developed near the site of ablation. This electrical storm persisted >30 minutes after cessation of RF current delivery, and was suppressed by additional RF applications to the site of origin of the new PVC.     

Radiofrequency Catheter Ablation of the Slow Reentrant Pathway of Sustained Ventricular Tachycardia

The article reports the cases of two patients with severe coronary artery disease and associated recurrent sustained ventricular tachycardia successfully treated with radiofrequency catheter ablation. In the first patient, two different types of ventricular tachycardia (one incessant) were eliminated. In all procedures, an area of slow conduction critical for tachycardia maintenance was localized by endocardial mapping techniques. Radiofrequency energy delivered to this area could permanently modify the anatomical substrate of the arrhythmia. After single follow-ups of 19, 14, and 13 months regarding the arrhythmic entities, the patients are well and free from spontaneous recurrences.     

Morphological Variation of Nonreentrant Idiopathic Ventricular Tachycardia Originating from the Right Ventricular Outflow Tract and Effect of Radiofrequency Lesion

RF catheter ablation was performed in 16 patients with nonreentrant idiopathic VT originating from the RVOT. All documented VT was monomorphic, but subtle morphological variation in the VT-QRS complex was observed in 10 (63%) of 16 patients. Through endocardial mapping, VT origin was determined within a narrow site (< 0.5 ± 0.5 cm) in 4 of the 10 patients with the morphological variation. In the other 6 of 10 patients, the origin extended to an area of > 0.5 ± 0.5 cm. In VT with morphological variation, the local electrogram at the site of VT origin also showed variation in morphology and activation sequence. For VT of narrow origin, RF application to the site eliminated the VT. However, in VT from a wide arrhythmogenic area, RF current had to be delivered to 3–7 distinct sites to cover the possible origin, and specific QRS configuration of VT and/or PVC was ablated at each of the earliest activation site. All but one VT were successfully ablated by RF current. Subtle morphological variation was frequent in this type of VT, and about half were associated with a wide arrhythmogenic area. Precise mapping and analysis of the efficacy of each BF application might be helpful to better understand the relationship between subtle changes of VT-QRS morphology and their origins.     

Ventricular Fibrillation and Sudden Death After Radiofrequency Catheter Ablation of the Atrioventricular Junction

Two hundred thirty-five patients underwent RF catheter abhtion of AV conduction for symptomatic drug refractoiy AF (84%), atrial flutter (9%), and atrial tachycardia (7%). In the first 100 patients, postahlation pacing was not prospectively set at any specific rate and was always ≤ 70 beats/min. In the next 135 patients, postabiotion pacing was prospectively set at 90 beats/min for 1–3 months. Six of the first 100 patients (6%) had VF or sudden death after the RF procedure and none (0%) of the next 135 patients did (P < 0.05). One of the six patients had recurrent VF 4 days after the ablation. Five patients were successfully resuscitated and one patient died. There were no statistically significant differences between patients with and without (aborted) sudden death or between the first 100 and the next 135 patients with respect to age, sex, underlying heart disease, EF, number of RF applications, or leftor right-sided approach of the procedure. VF mostly occurred during episodes of slow ventricular escape rhythms or during slow ventricular pacing. We conclude that malignant ventricular arrhythmias and sudden death are possible complications of RF ablation of the AV junction. The mechanism of these complications could have a bradycardia dependent nature and it seems that the occurrence of malignant arrhythmias can be prevented by temporarily pacing the heart at relatively fast rates immediately after ablation.     

False Inhibition of an Atrial Demand Pacemaker Caused by an Insulation Defect in a Polyurethane Lead

A patient who had an atrial demand pacemaker (AAI) presented with irregular pacing at a routine examination 5 months after implantation. When a magnet was applied over the pulse generator regular fixed rate pacing was obtained, thus proving oversensing in the system. Reprogramming the input sensitivity level to 2.5 and 5.0 m Vdid not solve the problem. Programming the pulse generator to the triggered mode (AAT) showed acceleration of the stimulation rate but also inhibition of the system. An S-S interval of 1260 ms was measured at a programmed interval of 857 ms (70 bpm). The pulse generator was disconnected and the intra-atrial electrogram was recorded. This showed different spurious signals varying in morphology and amplitude. Fortunately we were able to remove the lead (Medtronic 6991-U) from the atrial appendage. Subsequently a Helifix 12 mm AT lead was successfully implanted in the right atrial appendage and the same pulse generator was connected to the newly implanted lead. When the removed lead was examined by the manufacturer, a small tear in the insulation of the wire was defected. The dimensions of the tear were 0.1 × 0.7 mm. The tear was caused by stress corrosion cracking in the polyurefhane tubing of the lead.     

Perforation of the Right Ventricular Free Wall by an Active Fixation Transvenous Cardioverter Defibrillator Lead

A 58-year-old patient with dilated cardiomyopathy underwent implantable cardioverter defibrillator (ICD) implantation. The postoperative course was complicated by perforation of the right ventricular free wall by the active fixation transvenous ICD lead. The type of ICD lead and the type of organic heart disease are apparently important risk factors for perforation.     

The Effect of Nonisodiametric Design on the Ease of Extracting Chronically Implanted Pacemaker Leads

Extracting permanently implanted transvenous pacemaker leads is often difficult because a fibrous sheath tends to trap the lead at various points along its course. Because many leads have bulbous or nonisodiametric portions, extraction may be rendered even more troublesome, because it is difficult to pull the larger portion through the narrow areas of the sheath. Furthermore, forceful extraction may have dire consequences, such as cardiac laceration. A study was undertaken in animals to evaluate the effect of lead isodiametricity on lead extraction. The results show that any increase in the diameter of the lead tip greatly reduces the ease of its removal. Consequently, leads designed to be isodiametric tbroughout their entire lengths will greatly enhance their removability.     

Reversibility of "Tachycardia Induced Cardiomyopathy" Following the Cure of Idiopathic Left Ventricular Tachycardia Using Radiofrequency Energy

We report a cose of incessant ventricular tachycardia with right bundle branch block and left axis deviation morphology resulting in severe LV dysfunction and congestive heart failure. Radiofrequency ablation of the appropriate site in the region of posteroapical part of the LV septum resulted in the cure of the arrhythmia. On a 3-month follow-up, the LV size and function returned to normal.     

Bradycardia Dependent QT Prolongation and Ventricular Fibrillation Following Catheter Ablation of the Atrioventricular Junction witb Radiofrequency Energy

Recurrent ventricular fibrillation was observed in a 67-year-old woman following catheter ablation of the AV junction using radiofrequency energy. This serious complication has been reported following direct current energy ablation of the AV junction, but not after using radiofrequency energy. This life-threatening arrhythmia seemed pause and bradycardia dependent. It was followed by QT_c prolongation of the QRS escape rhythm 1 day after the procedure. Ventricular arrhythmias were suppressed by rapid ventricular pacing.     

Long-Term Performance of the Attain Model 4193 Left Ventricular Lead

Background: Cardiac resynchronization therapy (CRT) has proven to be a valuable therapy addition for patients with drug-refractory heart failure and a ventricular conduction delay. Delivery of CRT is dependent upon the successful implantation and chronic performance of a left ventricular (LV) pacing lead. This study assessed the long-term electrical performance and safety of a steroid-eluting, transvenous, over-the-wire, cardiac vein pacing lead.
Methods: The Attain Model 4193 LV lead (Medtronic, Inc, Minneapolis MN, USA) was successfully implanted in 1,070 patients with 286 patients completing 3 years of follow-up. Clinical data were collected at pre-implant, implant, and at 6-month intervals for 3 years.
Results: Over 3 years, the mean chronic pacing threshold ranged from 1.9 V to 2.1 V, the mean R-wave sensing amplitudes ranged between 13.6 mV and 15.0 mV, and the mean pacing impedance ranged between 562 ohms and 590 ohms. Additionally, the observed freedom from first post-implant LV-lead-related complications was 90.4%. Of 1,070 total patients, 82 experienced 89 LV-lead-related adverse events requiring invasive interventions or resulting in the termination of the CRT therapy. The LV lead was repositioned in 31 patients, replaced in 21 patients, and explanted/capped in four patients. There were no deaths related to the LV lead during implantation or during the follow-up period.
Conclusions: The data suggest that the 4193 LV lead is safe and effective over time. The LV lead electrical measurements remained stable through follow-up, demonstrating reliable long-term performance within the recommended value range at 36 months and had an acceptable complication rate.     

Radiofrequency Catheter Ablation of Ventricular Tachycardia Guided by Nonsurgical Epicardial Mapping in Chronic Chagasic Heart Disease

We report a case of a 63-year-old women with Chagas'disease and recurrent, syncopal VT treated by RF catheter ablation in whom endocardial application of RF energy was guided by nonsurgical epicardial mapping. The procedure was undertaken in the electrophysiology laboratory under deep anesthesia. VT was interrupted after 2.4 seconds of application and rendered noninducible afterwards. Two weeks after the procedure, a distinct morphology VT was induced by programmed ventricular stimulation, and the patient was started on amiodarone, remaining asymptomatic 12 months after the procedure.