AutoCapture with Dual-Coil Leads of Implantable Cardioverter Defibrillator

AutoCapture™ (AC) can confirm ventricular capture with true bipolar single coil leads of implantable cardioverter defibrillators (ICD). The compatibility of AC with a new, true bipolar, dual-coil ICD lead needed to be evaluated. This multicenter study enrolled 46 patients (69 ± 10 years, 37 men) undergoing ICD implantation. All patients received a true bipolar, dual-coil lead. Evoked response (ER) sensitivity and AC threshold tests were performed using a pulse generator with the AC algorithm. Mean capture threshold was 0.85 ± 0.67 V, pacing impedance 612 ± 225 Ω, R wave amplitude 13.85 ± 6.17 mV, and defibrillation threshold 14.4 ± 5.1 J. AC was recommended in 45 patients (97.8%) with ER and polarization values of 14.86 ± 7.32 mV and 0.87 ± 0.69 mV, respectively. The AC algorithm was highly compatible with true bipolar, dual-coil ICD leads. An AC algorithm specifically designed for an ICD may improve the generator longevity. Further examination of AC compatibility with other leads is warranted.     

Permanent Pacing from the Coronary Sinus in a Patient with an Implantable Defibrillator

A woman with an ICD underwent permanent pacemaker implantation for bradycordia-tachycardia syndrome. Despite multiple right atrial positions, oversensing secondary to "double counting" was always noted. A coronary sinus pacing catheter was inserted and left atrial pacing was accomplished with acceptable pacing and sensing characteristics. The patient has since done well without further shocks.     

The Value of DDD Pacing in Patients with an Implantable Cardioverter Defibrillator

Although the beneficial effects of DDD pacing are well known, currently available ICDs provide only fixed rate ventricular antibradycardia pacing. In a consecutive series of 139 patients with ICDs, we have analyzed the need for antibradycardia pacing and the indications for DDD pacing. We also report our initial experience with the Defender 9001 (ELA Medical, France) DDD-ICD. Out of 139 patients, 25 (18%) were in need of antibradycardia pacing. Ten patients already had a pacemaker at the time of ICD implantation and ten other patients had a conventional pacemaker indication at that time. Five patients became pacemaker dependent during a follow-up of 20 ± 8 months. The disorders necessitating pacemaker therapy were high degree AV conduction disturbances in 72%, sick sinus syndrome in 12%, and AF with a slow ventricular response in 16% of patients. Based upon current indications, DDD pacing was indicated in 20 (80%) of 25 patients. The Defender 9001 DDD-ICD (ELA Medical) was used in two patients with ischemic cardiomyopathy and pacemaker syndrome with VVI pacing. Cardiac output during DDD pacing increased by 36% in one patient with an increase in VO₂ max during exercise of 29%. The other patient showed an increase in cardiac output of 50% with DDD pacing, and, while unable to exercise with VVI pacing, had a VO_2max of 24 mL/kg per minute during DDD pacing. Up to 18% of our ICD patients are in need of antibradycardia pacing. Of these pacemaker dependent patients, 80% have an indication for DDD pacing. Our first clinical experience with a DDD-ICD confirms the hemodynamic benefit of AV synchronous pacing in ICD patients with pacemaker syndrome.     

Inappropriate Pauses During Bradycardia Pacing in a Third-Generation Implantable Cardioverter Defibrillator

Many ICD devices have the capability for back up bradycardia pacing. Because of the use of a single sensing algorithm for both bradycardia and tachycardia functions, they may be prone to certain "sensing errors." Following implantation of an ICD in a patient with long QT syndrome, "inappropriate" pauses were noted during bradycardia pacing, which were exactly twice the programmed pacing cycle length. This was due to an automatic increase in the device's sensitivity during pacing, a characteristic of the automatic gain control of this particular ICD. Proper recognition of this ICD's special features, known as "lower threshold crossing," allowed noninvasive rectification of the problem and prevented these pauses.     

The Use and Interaction of Permanent Pacemakers and the Automatic Implantable Cardioverter Defibrillator

The adverse interactions of permanent pacemakers and automatic implantable cardioverter defibrillators (AICD) were studied in nine patients in whom both devices were implanted. Both unipolar and bipolar pacemakers were evaluated. The permanent pacemakers were also used to do noninvasive electrophysiological studies and to induce ventricular fibrillation. Undersensing of ventricular fibrillation by the permanent pacemakers caused inappropriate pacemaker stimuli, which caused undersensing of ventricular fibrillation by the AICD in three of four patients with unipolar pacemakers. After an AICD discharge, pacemaker noncapture was seen in eight of 22 episodes for an average 4.9 seconds and inability to sense was seen in 11 of 20 episodes for an average 9.0 seconds. Counting of pacemaker stimuli and QRS by the AICD caused inappropriate discharges. Noninvasive electrophysiological testing by the pacemakers correlated with invasive testing. Furthermore, induction of ventricular fibrillation was successful in four of five patients attempted, though requiring long bursts at high outputs at the shortest cycle lengths obtainable by these pacemakers. Operation of the AICD and permanent pacemakers must be clearly understood to avoid adverse interactions of these devices.     

Antitachycardia Pacing in Patients with Implantable Cardioverter Defibrillators: How Many Attempts Are Useful?

The purpose of this study was to determine the termination and acceleration rates for 1 to 6 attempts of antitachycardia pacing (ATP) delivered by ICD in order to terminate spontaneously occurring VTs. Twenty-four ICD recipients with active ATP programs, including a maximum of six ATP sequences and spontaneously occurring VTs during follow-up, were investigated. During a mean follow-up of 42 ± 15 months (range, 17–63 months) 413 spontaneous VT episodes (17 ± 14; range, 1–49 per patient) resulting in appropriate ATP delivery by the ICD occurred. ATP successfully terminated 328 episodes (80 %) with a mean number of 1.6 ± 1.1 pacing sequences. Eighty episodes (19%) were accelerated by ATP and 5 (1%) were unresponsive to ATP. The ATP success decreased until the third ATP sequence (59%→ 31%→ 24%), but increased again in the fourth to sixth attempt (46%→ 46%→ 29%). The acceleration rate increased from sequence one to sequence three (8%→ 13%→ 28%), but decreased significantly in further ATP attempts (19%→ 0%→ 0%). The mean time delays until redetection or termination after 4, 5, and 6 attempts of ATP were 22 ± 5 seconds, 37 ± 2 seconds, and 41 ± 9 seconds, respectively. Nine patients (37%) used ≥3 ATP attempts during follow-up and all of them had a therapeutic benefit from it. Five out of 13 VTs (38%) treated with ≥4 attempts could ultimately be terminated by ATP. The results of this study demonstrate that the first ATP sequence is the most effective and that > 4 ATP attempts may be useful in a minority of patients. There seems to be a low risk of VT acceleration by the fourth to sixth ATP sequence. Because of the associated time delay, a high number of ATP attempts should only be programmed in patients with hemodynamically well-tolerated stable VTs.     

Safety of Antitachycardia Pacing in Patients with Implantable Cardioverter Defibrillators and Severely Depressed Left Ventricular Function

The purpose of this study was to investigate the efficacy and safety of antitachycardia pacing (ATP) in third-generation implantable Cardioverter defibrillators (ICDs) for terminating spontaneously occurring ventricular tachycardias (VTs) in patients with severely depressed left ventricular (LV) function. Ninety-one patients with active ATP were followed for 16 ± 13 months. During this period, 775 VT episodes occurring in 36 patients were treated by ATP. The patients were divided into two groups according to their LV ejection fraction (LVEF): group A with LVEF ± 30% (n = 20), and group B with LVEF ± 30% (n = 16). There were no differences between both groups in age, gender, underlying heart disease, indication for ICD therapy, or drug therapy. The VT rates were comparable (group A: 183 ± 16 beats/min; group B: 180 ± 21 beats/min; P = NS). Eighty-three percent of all episodes (n = 332) in group A and 93% of the VTs (n = 443) in group B were ATP terminated (P ± 0.01). Ten percent of VTs in group A were accelerated by ATP into the ventricular fibrillation zone versus 2% in group B (P ± 0.01). The individual termination rate and acceleration rate per patient were comparable in both groups. All VT episodes unresponsive to ATP were converted by backup shocks. The efficacy of first-shock therapy was similar in both groups (group A: 89%; group B: 97%; P = NS). The proportion of patients who needed at least one backup shock for unsuccessful ATP was comparable in both groups (group A: 65%; group B: 56%; P= NS). We conclude that ATP is effective and safe in patients with recurrent VTs and severely depressed LV function, and it can be safely programmed in this group of patients to minimize the use of shock therapy.     

Modified Magnet Test for a Reversed Automatic Implantable Cardioverter Defibrillator

We present the case of a 55-year-old man with atrial septal defect and cardiomyopathy who underwent implantation of an automatic cardioverter defibrillator (AICD) for ventricular tachycardia resulting in collapse. This case demonstrates multiple unusual complications related to AICD, including rotation of the pulse generator unit about its long axis requiring a "left-handed" magnet test to determine the appropriate counts.     

Implantable Transvenous Pacing Leads:

With the dawn of a new millennium, physicians' demands for very thin transvenous leads able to be positioned in nontraditional sites like the Bachmann's bundle, the high and mid-right ventricular septum, and the His bundle have created new and exciting challenges for lead engineers. Bipolar leads can now be as thin and reliable as unipolar leads. Cathode electrodes are very small, porous, and demonstrate high impedance. To optimize stimulation thresholds, steroid-eluting passive- and active-fixation electrodes have become popular for use in the atrium and ventricle. To create thin lead body diameters, new insulation and conductor materials and lead body designs are necessary. Hybrid medical materials having the best features of silicone rubber and polyurethane will allow for reliable insulation. Conductor cables instead of helical coils permit strong thin diameter leads to be designed. Transvenous lead implantation using the traditional stylet may not be possible with thin diameter leads, necessitating the use of sophisticated workstations using steerable catheters to guide these new active-fixation leads to selective sites in the right heart. The pacing lead of the future may be very different from the one used today. Ironically, it will have features and implantation techniques similar to the transvenous leads designed prior to the use of the stylet. We are now approaching full circle in lead development, retracing the footprints of the early implanters of three and a half decades ago. (PACE 2004; 27[Pt. II]:887–893)     

Initial Clinical Experience with a New Small Sized Third-Generation Implantable Cardioverter Defibrillator: Results of a Multicenter Study

This study reports the acute clinical experience with the new CPI VENTAK MINI: a small sized (68 cc), implantable cardioverter defibrillator (ICD) with 33 J stored energy. Implantation of the device was attempted in 113 patients (90 men, mean age 57 ± 16 years, 64 with coronary artery disease, mean left ventricular ejection fraction 41%) with ventricular tachycardia or ventricular fibrillation (VF). All 113 patients (100%) were ultimately implanted, 12% of them for ICD replacement. Transvenous lead implantation was accomplished in all 104 patients (100%) receiving new leads, 95% of them with a single lead configuration. The safety criteria for implantation (2 consecutive VF conversions at 15 J or 3 at 20 J. in both cases without failures to convert) were demonstrated in all but 7 patients (6%). In 6 of these, safety criteria were not fully assessed while in the last patient defibriliation efficacy was not determined. Of the 104 patients with new leads, 90% underwent pectoral implantation. Of the 9 patients (9%) abdominally implanted, only 4 (4%) (3 children) were judged small sized for pectoral implant. At predischarge testing, reliable VF detection and conversion were noted in 96 of 97 patients tested. There was no perioperative mortality. At a 3.6 ± 1.3 months follow-up, 34% of the patients had a spontaneous arrhythmic event, and 24% of the patients received shocks. Clinically inappropriate therapies occurred in 8% of the episodes in which any kind of therapy was delivered. This study demonstrates the short-term clinical efficacy and safety of the new device, and that pectoral implantation can be performed in the large majority of patients.     

Implantable Cardioverter Defibrillator Proarrhythmia: Case Report and Review of the Literature

A 31-year-old man who received an automatic cardioverter defibrillator subsequently underwent exercise testing. During exercise, a sinus tachycardia resulted above his device detect rate prompting two shocks, the second of which produced an unstable polymorphous ventricular tachycardia. In this article, we review the literature on automatic cardioverter defibrillator-induced ventricular tachyarrhythmias as well as the management of exercise testing in patients with these devices.     

Infections in Implantable Cardioverter Defibrillator Patients

Implantable cardioverter de;fibrillators fICDsj have been documented as an effective modality in reducing arrhythmic mortality. A serious complication associated with implantation of the device is infection. Few studies have addressed this issue. Two hundred seven patients with refractory ventricular arrhythmias underwent 207 ICD implantations, and 56 subcutaneous generator changes at our institution. Eight patients developed wound infections, four following ICD implantation (4 out of 207 or 1.9%), and four following a generator change (4 out of 56 or 7.1%). Wound cultures most commonly revealed Staphylococcus aurous and Staphylococcus epidermidis. Infections treated with antibiotics alone, or with only generator removal, frequently recurred (four out of five attempts). There were no recurrences following total patch/lead and generator system removal. In jive patients, the same generator unit was successfully emplaned following ethylene oxide sterilization without infection recurrence. We conclude that treatment of device-associated infection generally requires total generator and patch/lead system removal, and that generator units can be successfully reimplanted yielding substantial cost savings.     

Infection of Implantable Cardioverter Defibrillator Systems: A Preventable Complication?

In a consecutive series of 164 patients undergoing primary implantation of an impJantable cardioverter defibrillator (ICD), two patients died in the hospital (1.2%) and early system infection developed in one patient requiring expJantation of the device (0.61%). Late infection developed in one additional patient (0.61%) 7 months after transvenous ICD implantation, and was thought to be due to a recent intravascular catheterization. Symptomatic generator pocket hematomas developed in three patients, two of which were treated by simple evacuation and one with temporary generator explantation and subsequent reimplantation of the unit in a new pocket. No infection developed in these three patients during follow-up. Generator erosion without obvious system infection developed in a fourth patient. Guidelines for the prevention of infection in ICD systems are presented.     

A Multicenter, Randomized Trial Comparing an Active Can Implantable Defibrillator with a Passive Can System

Replacing one defibrillation electrode lead by the defibrillator can may simplify implantation of the ICD. In this multicenter study, 304 patients were randomized to receive either the biphasic active can (AC) (model 7219C system, Medtronic, Inc.) or the passive can (PC) (model 7219D system). The AC and PC systems were compared with respect to their ability to meet the implant defibrillation criterion and to defibrillate VF, and to DFTs, implant time, patient adverse events, and survival rates. A higher percentage fulfilled the implant defibrillation criterion on the first configuration with the AC (86.3% vs 75.9% for PC; P = 0.023), and the first shock success for terminating induced VF was 94% for AC compared to 89% for PC (P = 0.026). DFTs were significantly lower (10.9 vs 12.7 J; P = 0.031), and implant time was significantly shorter for the AC patients (99.2 vs 112.0 min; P = 0.002). The two groups showed no significant differences in 3-month adverse event rates, 3-month survival, and hospital stay.     

Use of a Wireless Implantable Cardioverter Defibrillator in a Patient with a Preexisting Neurostimulator

We report the case of a 54-year-old man with a previously implanted neurostimulator who presented with palpitations and was found to have sustained ventricular tachycardia on electrophysiologic study. A Medtronic wireless implantable cardioverter defibrillator (ICD; Medtronic Inc., Minneapolis, MN, USA) with home monitoring (HM) was successfully implanted. Interaction testing during implantation, follow-up, and HM showed that there was no device-device interaction.     

Does the Initial Presentation of Patients with Implantable Defibrillator Influence the Outcome?

The influence of the clinical presentation on the long-term outcome in 213 consecutive patients with ICDs, ECG storage capability, and nonthoracotomy leads, was analyzed. Sixty-six patients presented with cardiac arrest (CA), 81 patients with hemodynamically stable VT, and 66 patients with syncope (SY). Patient characteristics were: mean age CA 62, VT 61, SY 61 years; mean ejection fraction CA 31%, VT 29%, SY 30%; coronary artery disease CA 71%, VT 71%, SY 64% (all P > 0.05 Fisher's exact test); female gender CA 40%, VT 14%, SY 19% (CA vs VT and SY, P < 0.005); inducibility by programmed stimulation CA 50%, VT 84%, SY61 % (VT vs CA and SY, P < 0.001, CA vs SY, P > 0.05). During a mean follow-up of 14.5 months, 29 patients died; CA 12%, VT 14%, SY 9% (P > 0.05). Comparing Kaplan-Meier curves, no difference in the time course of overall mortality was found (log-rank P > 0.05). In the CA, VT, and SY groups, 543, 1,630, and 189 ICD therapies (including antitachycardia pacing, low energy cardioversion, and defibrillation) were observed, respectively. Actuarial analysis showed a shorter interval between implantation and first ICD therapy for VT versus CA and SY (log-rank P < 0.005). Patients presenting with VT experienced earlier and more frequent ICD therapies than patients with CA or SY independent of age, ejection fraction, and heart disease. No difference in overall mortality and time course of fatal events was observed among the three groups.