A new steroid-eluting screw-in electrode

Acute changes in the pacing threshold after lead implantation. Comparison between retractable and sweet-tip active-fixation leads

Although the pacing threshold of steroid-eluting active-fixation leads remains stable over the long term, it changes rapidly after screw-in. We compared the pacing threshold in the acute phase between retractable and Sweet-Tip active-fixation leads. We studied 132 patients who were implanted with active-fixation leads for new pacemaker implantation or additional leads required due to disconnected/leaking leads. Pacing threshold was measured at 4 time points: before screw-in, immediately, and 5 and 10 minutes after screw-in. If the pacing threshold was > 1.5 volts (V) at 5 minutes, we changed the pacing site so that it became ≤ 1.5 V. A total of 169 retractable leads (Medtronic: 107 leads, St. Jude Medical: 62 leads) and 33 Sweet-Tip leads (Boston: 33 leads) were implanted. Eighty-nine leads were implanted in the atrium and 113 leads in the ventricle. Seventy patients were implanted with both atrial and ventricular leads. The pacing threshold of Sweet-Tip leads increased immediately after screw-in, while that of retractable leads decreased (Sweet-Tip: 0.20 ± 0.57 V, Retractable: -0.15 ± 0.53 V, P < 0.05). The pacing threshold of both types of leads decreased similarly from immediately to 5 minutes after screw-in (Sweet Tip: -0.29 ± 0.43 V, Retractable: -0.25 ± 0.36 V, P = NS). Few changes in the threshold were detected between 5 and 10 minutes. Because the pacing threshold of Sweet-Tip active-fixation leads increased immediately after screw-in and that of both type leads decreased from immediately to 5 minutes, we should measure the pacing threshold from 5 minutes after screw-in.

Randomized Comparison of J-Shaped Atrial Leads with and without Active Fixation Mechanism

BACKGROUND

In this prospective, randomized, controlled study, we compared the performance of J-shaped active fixation (AF) atrial leads with J-shaped passive fixation (PF) leads, over a 1-year follow-up period.

METHODS

A total of 200 consecutive patients were prospectively randomized for implantation with a Medtronic 5568 AF lead model (n = 103; Minneapolis, MN, USA) versus a Medtronic 5592 PF model (n = 97), and all lead-related measurements and complications were recorded over one year.

RESULTS

All leads were successfully implanted with a nonsignificant difference in crossover rate to the alternative lead due to failed implantation (1 in the AF and 4 in the PF group, P = NS). Fluoroscopy time during implantation procedure was significantly shorter in the PF group (2.1 +/- 3.6 vs 3.3 +/- 4.5 minute, P < 0.05). Pacing thresholds during implantation were significantly lower in patients with PF leads (0.7 +/- 0.3 V vs 0.9 +/- 0.3 V, P < 0.001) and this difference persisted at 1-year follow-up (0.8 +/- 0.6 V vs 1.3 +/- 0.9 V in PF and AF leads respectively, P < 0.05). Lead-related complications occurred in PF and AF with similar frequency (4% and 9% respectively, P = 0.2). However, pericardial complications occurred only in the AF group (6 cases, P = 0.01). Lead dislodgement was observed in only two cases-both in the PF group (P = 0.3).

CONCLUSION

Both types of J-shaped atrial leads had reasonable performance. PF leads required shorter fluoroscopy time for implantation, demonstrated a better pacing threshold over a 1-year follow-up period and had no pericardial complications, while AF lead implantation was complicated by pericardial irritation and/or effusion in 6% cases (P = 0.01).

Long-Term Performance of Screw-In Atrial Pacing Leads: A Randomized Comparison of J-Shaped and Straight Leads

OBJECTIVE

In this prospective, randomized, control study we compared performance of J-shaped (JL) and straight atrial leads (SL) with active (screw-in) fixation mechanism, over a 5-year follow-up period.

SUBJECTS AND METHODS

A total of 208 consecutive patients were randomized for implantation with a Medtronic 4568 JL model (n = 103) versus a Medtronic 4068 SL model (n = 105), and all lead-related measurements and complications were recorded.

RESULTS

Lead-related complications occurred in JL and SL with similar frequency (6% and 9%, respectively, P = 0.45). Lead dislodgment occurred in 8 (7.8%) cases in SL versus none in JL (P = 0.004). Lead malfunction and excessive pacing thresholds without macrodislodgment occurred more frequently in JL (11; 10.7%) than in SL (4; 3.8%), P = 0.055. Lead material failure (insulation break) occurred only once in SL at the 5-year checkup. Most complications occurred during the first year after implantation. Other events occurred in both leads with similar frequency and included: death in 39 and 35, loss of follow-up in 8 and 6, and development of atrial fibrillation in 9 and 15 patients, respectively. Of those who completed follow-up, lead impedance and pacing threshold increased significantly in both groups. P wave decreased in SL but not in JL.

CONCLUSION

More dislocations occurred in SL, but were counterbalanced by more lead malfunctions and excessive pacing thresholds in the JL group. Both leads demonstrated minor deterioration in electrical measurements during follow-up, with only 1 case of lead material failure in SL. Overall, both groups demonstrated favorable lead performance throughout follow-up.

Rapid Decline in Acute Stimulation Thresholds with Steroid-Eluting Active-Fixation Pacing Leads

BACKGROUND AND AIM

There is an increasing use of active-fixation leads for cardiac pacing, yet concerns remain regarding initial high stimulation thresholds. The aim was to perform a detailed analysis of pacing parameters at the time of implantation to determine when lead repositioning should be considered.

METHODS

We performed a prospective observational study of consecutive new pacemaker implants. Detailed analysis of pacing parameters was collected at 2-minute intervals for 10 minutes, and at day 1 and week 8 following implant.

RESULTS

Ninety-four patients underwent implantation of 79 dual-chamber and 15 single-chamber pacemakers using active-fixation leads in both chambers. An initial threshold of >1 V was demonstrated in 45/94 (48%) ventricular leads (mean threshold 1.5 +/- 0.3 V). This declined rapidly to 0.9 +/- 0.3 V at 4 minutes (P < 0.01), 0.7 +/- 0.3 V at 10 minutes (P < 0.01), and 0.6 +/- 0.3 V at day 1 (P < 0.01). At day 1, 43/45 leads were <1 V. There were 79 atrial leads. An initial threshold of >1 V (mean 1.7 +/- 0.6 V) was demonstrated in 41/79 (52%) leads falling significantly to 1.1 +/- 0.5 V at 4 minutes (P < 0.01), 0.9 +/- 0.4 V at 10 minutes (P < 0.01), and 0.6 +/- 0.2 V at day 1 (P < 0.01). At 10 minutes, 32 of 41 leads demonstrated a threshold of <1 V with all leads <1 V at day 1. Thresholds were maintained medium term.

CONCLUSIONS

Active-fixation leads are commonly associated with initially high thresholds that fall rapidly. An initial threshold of 2 V should be provisionally accepted and retested at 4 minutes. The majority will have a threshold of <1 V the following day. A failure of a high threshold to decline at 4 minutes requires lead repositioning.

Successful use of an acceleration rate response pacemaker with a transvenous steroid-eluting screw-in lead for third-degree atrioventricular block in a labrador retriever

Permanent pacemakers are commonly used in veterinary practice and can have a dramatic effect on the treatment of heart block. A Labrador Retriever dog suffering from exercise intolerance secondary to third degree atrioventricular block was treated with a new pacemaker system. A steroid-eluting screw-in type lead that has the advantage of being more fixed to the myocardial wall without increasing the pacing threshold was used. The heart rate was regulated with an acceleration sensing pacemaker generator that included several automatic modulation systems. Nineteen months after implantation, the dog has a normal level of activity. The present case suggests that this pacemaker design may offer important advantages for canine patients.

Randomized comparison of J-shaped and straight atrial screw-in pacing leads

OBJECTIVE

To study the importance of a J shape in atrial pacing leads.

PATIENTS AND METHODS

We compared in a randomized controlled study acute and chronic results with 2 steroid-eluting, polyurethane, screw-in atrial lead models that differ only in shape. A total of 208 patients were randomized to have implantation of either a straight atrial lead (n = 105) or a J-shaped atrial lead (n = 103). Patients were followed up for 1 year.

RESULTS

On implantation, there were no significant differences between leads in rates of failure to implant, implant measurements, number of attempts to achieve an acceptable position, and fluoroscopy times. Before discharge and at 3-month and 1-year follow-up, electrical measurements showed no statistical differences between leads. During the first year after implantation, there were 2.9% early dislodgments (< 1 week after implantation) and 2.9% late dislodgments in the straight lead group (5.9% rate of all dislodgments) vs no dislodgments in the J-shaped lead group (P = .01). There was a trend toward higher rates of exit block and lead malfunction in the J-shaped lead group. Rates of pericardial complications, subclavian/axillary thrombosis, and chronic atrial fibrillation were the same in both groups.

CONCLUSIONS

Both leads appear to have an equally favorable performance profile for 1 year of follow-up. The J-shaped lead seems to be more stable and have fewer dislodgments, although it may have a somewhat higher malfunction rate.

Low chronic pacing thresholds of steroid-eluting active-fixation ventricular pacemaker leads: a useful alternative to passive-fixation leads

Active-fixation pacemaker leads enable pacing at various sites, have a low dislodgment rate, and are easier to extract than passive-fixation leads, though are usually not routinely implanted in the ventricle because of their higher pacing threshold. The long-term pacing threshold associated with an active-fixation steroid-eluting lead was prospectively measured in 18 women and 20 men. At a mean follow-up of 14 months (range 3-25 months), pacing threshold increased from 0.71 +/- 0.29 V to 0.96 +/- 0.28 V (P = 0.01) between implant and the first month of follow-up, then remained stable over time, consistently allowing the long-term programming of the ventricular output at 2.5 V, while lead impedance remained stable (from 647 +/- 161 omega at implant to 666 +/- 122 omega at last follow-up). If the long-term performance of this type of lead is confirmed, the routine implantation of ventricular steroid-eluting active-fixation leads should be considered since lead extraction has become a major concern.

Evolution of an active fixation atrial pacing lead

Three bipolar atrial pacing leads from one manufacturer differing in a single electrode design characteristic were compared. Each lead had nonretractable screw and a microporous electrode tip made of activated carbon. Model S84F had a tip surface area of 8 mm2. In model S44F, the tip surface area was reduced to 4 mm2 by insulation of the screw, and in model BS45D, steroid elution was added to the 4 mm2 tip. Ten patients in each group received identical pulse generators. During implantation, atrial potentials (5.4 +/- 2.0, 4.2 +/- 2.0, 4.6 +/- 2.1 mV), pacing thresholds at 0.5 ms (0.47 +/- 0.14, 0.41 +/- 0.15, 0.55 +/- 0.33 V) and lead impedance at 2.5 V/0.5 ms (515 +/- 80, 575 +/- 152, 546 +/- 131 omega) were comparable among groups. The early postoperative threshold peak was significantly lower with the BS45D than with the S84F and S44F lead models. One year after implantation, charge threshold was significantly lower with the BS45D lead than with the S84F and the S44F model (0.34 +/- 0.11 vs. 0.68 +/- 0.20 and 0.56 +/- 0.21 microC; P < 0.05). Lead impedance at 2.5 V/0.5 ms (557 +/- 90, 549 +/- 36, 524 +/- 72 omega) and atrial sensing (4.3 +/- 2.1, 4.7 +/- 1.9, 4.7 +/- 0.9 mV) were not significantly different. One year postimplant, current drain of the pacing system was measured by pacemaker telemetry at chronic output settings in AAI mode/70 beats/min. Battery current measured among the three atrial lead models did not differ significantly (S84F: 11.9 +/- 0.90, S44F: 12.2 +/- 1.8, BS45D: 11.5 +/- 0.26 microA).

IN CONCLUSION

reduction of the tip surface area by insulation of the screw did not improve pacing performance. Addition of steroid elution to the 4 mm2 tip significantly lowered the early threshold peak and the long-term pacing threshold. Lowering of the pacing threshold, however, did not lower the current drain of the pacing system.

Atrial lead placement during atrial fibrillation. Is restitution of sinus rhythm required for proper lead function? Feasibility and 12-month functional analysis

Unexpected atrial fibrillation (AF) during implantation of an atrial pacemaker lead is sometimes encountered. Intraoperative cardioversion may lengthen and complicate the implantation process. This study prospectively investigates the performance of atrial leads implanted during AF (group A) and compares atrial sensing and pacing properties to an age- and sex-matched control group in which sinus rhythm had been restored before atrial lead placement (group B). Patient groups consisted of 32 patients each. All patients received DDDR pacemakers and bipolar, steroid-eluting, active fixation atrial leads. In patients with AF at the time of implantation (group A), a minimal intracardiac fibrillatory amplitude of at least 1.0 mV was required for acceptable atrial lead placement. In patients with restored sinus rhythm (group B), a voltage threshold < 1.5 V at 0.5 ms and a minimal atrial potential amplitude > 1.5 mV was required. Patients of group A in whom spontaneous conversion to sinus rhythm did not occur within 4 weeks after implantation underwent electrical cardioversion to sinus rhythm. Pacemaker interrogations were performed 3, 6, and 12 months after implantation. In group A, implantation time was significantly shorter as compared to group B (58.7 +/- 8.6 minutes vs 73.0 +/- 17.3 minutes, P < 0.001). Mean atrial potential amplitude during AF was correlated with the telemetered atrial potential during sinus rhythm (r = 0.49, P < 0.001), but not with the atrial stimulation threshold. Twelve months after implantation, sensing thresholds (1.74 +/- 0.52 mV vs 1.78 +/- 0.69 mV, P = 0.98) and stimulation thresholds (1.09 +/- 0.42 V vs 1.01 +/- 0.31 V, P = 0.66) did not differ between groups A and B. However, in three patients of group A, chronic atrial sensing threshold was < or = 1 mV requiring atrial sensitivities of at least 0.35 mV to achieve reliable atrial sensing. Atrial lead placement during AF is feasible and reduces implantation time. However, bipolar atrial leads and the option to program high atrial sensitivities are required.

Long-term superiority of steroid elution in atrial active fixation platinum leads

Steroid elution reduces the acute increase in stimulation threshold particularly in active fixation leads. The aim of this study was to investigate the long-term efficacy of steroid elution in atrial screw-in leads compared to conventional lead design. Two different bipolar active fixation platinum lead designs were implanted. Leads were similar except for the presence (group S, n = 66) or absence (group N, n = 68) of steroid elution. Patients received dual chamber pacemakers with the following atrial leads in consecutive order: Medtronic 4058 M (group N, n = 30), Medtronic 4068 (group S, n = 40), Vitatron IMS 13 (identical to 4058 M, group N, n = 38), and Vitatron IMX 13 (identical to 4068, group S, n = 26). The mean follow-up period was 40.7 +/- 16.1 months (range 10 to 84 months). Stimulation thresholds, pacing impedances, P wave potentials, and sensing threshold were assessed for both groups immediately, 10 days, 6 weeks, and 3 months after implantation followed by 6-months intervals. Energy thresholds, chronaxie-rheobase products, and energy consumption of atrial pacing were calculated. Chronic values were deduced from the most recent measurement performed in an individual patient. Within the first 10 days after implantation, atrial voltage threshold at pulse duration of 0.4 ms increased from 0.91 +/- 0.42 to 2.06 +/- 0.45 V in group N (P < 0.001). Less increase was observed in group S (0.83 +/- 0.39 to 1.08 +/- 0.53 V, P = 0.003). Atrial voltage thresholds remained markedly lower in steroid-eluting leads during whole follow-up (1.12 +/- 0.49 V in group S vs 1.58 +/- 0.71 V in group N, P < 0.001). Chronic energy consumption was markedly reduced in group S (4.0 +/- 2.7 microJ) compared to group N (9.8 +/- 7.5 microJ, P < 0.001). An atrial voltage threshold below 1.25 V at 0.4 ms was achieved in 92.3% of patients of group S allowing programming of an output of 2.5 V. Such low outputs were feasible in only 49.3% of patients in group N (P < 0.001). Chronic P wave amplitudes did not differ significantly between groups (3.27 +/- 1.81 mV in group N vs 3.24 +/- 1.18 mV in group S, P = 0.91). Steroid elution diminishes the increase of stimulation thresholds of nonsteroid atrial active fixation platinum leads resulting in a long-term reduction of energy consumption. Thus, use of steroids can be recommended for general use in atrial active fixation lead designs.

Successful results of a bipolar active fixation lead for atrial application: an interim analysis

Adequate atrial lead performance consists of stable sensing and pacing properties. To evaluate whether the CPI 4269 bipolar lead, covered with mannitol (Sweet Tip), in the atrial position encounters these properties, we performed a prospective study of this lead. After complete dissolution of the mannitol helix, mapping of the atrium to obtain the highest electrogram and lowest threshold was followed by screw-in into the endocardium. Intraoperative measurements were performed and long-term follow-up was scheduled every 6 to 12 months to measure threshold and perform an intracardial electrogram. Between February 1993 and December 1996, a total number of 73 leads in the atrial position in a consecutive series of patients was implanted. Implantation was performed in 28 patients receiving an AAIR and 45 patients a DDDR pacemaker. Reason for pacemaker implantation was a third-degree AV block in 37% of patients, type II second-degree AV block in 25%, sick sinus syndrome in 35%, and drug refractory paroxysmal atrial fibrillation following His-bundle ablation in 3%. The intraoperative bipolar atrial electrogram had a mean voltage of 4.25 +/- 2.1 mV. The acute atrial bipolar threshold was 0.63 +/- 0.43 V, and current was 1.35 +/- 0.81 mA at a 1.0-ms pulse duration. The mean acute resistance of the lead was 572 +/- 86 Ohm. After a mean follow-up of 18.3 months, the bipolar intracardial electrogram was 3.37 +/- 2.00 mV, the mean atrial threshold measured at the last outpatient clinic visit was 0.99 +/- 0.74 V and the mean impedance was 640 +/- 127 Ohm. A sensing problem due to traction of the atrial lead occurred in only one patient. Acute and late dislodgement did not occur. The CPI 4269 (Sweet Tip) lead is manufactured with a dissolvable capsule covering the helix tip electrode, permitting a safe passage through the venous system. This interim analysis shows that this lead in the atrial position has favorable acute and chronic results.

Five-year follow-up of a bipolar steroid-eluting ventricular pacing lead

Steroid-eluting pacing leads are known to attenuate the threshold peaking early after implantation. Long-term performance, however, is not yet settled. The lead design tested in this prospective study combines a 5.8-mm2 tip of microporous platinum-iridium with elution of 1.0 mg of dexamethasone sodium phosphate and tines for passive fixation (model 5024, Medtronic Inc.). In 50 patients (mean age 69 +/- 10 years), the electrode was implanted in the right ventricular apex. Follow-up was performed on days 0, 2, 5, 10, 28, 90, 180 and every 6 months thereafter for 5-years postimplant. At each visit, pacing thresholds were determined as pulse duration (ms) at 1.0 V and as the minimum charge (microC) delivered for capture. Lead impedance (omega) was telemetered at 2.5 V-0.50 ms, and sensing thresholds (mV) were measured in triplicate using the automatic sensing threshold algorithm of the pacemaker implanted (model 294-03, Intermedics Inc.). On the day of implantation, mean values were 0.10 +/- 0.03 ms, 0.12 +/- 0.03 microC, 758 +/- 131 omega, and 13.1 +/- 1.8 mV, respectively. Beyond 1-year postimplant, pacing thresholds did not vary significantly. Sensing thresholds and lead impedance values were stable during long-term follow-up. Five years after implantation, mean values were 0.23 +/- 0.11 ms, 0.24 +/- 0.07 microC, 670 +/- 139 omega, and 11.6 +/- 3.1 mV for pulse width and charge threshold, lead impedance, and sensing threshold, respectively, and all leads captured at 1.0 V with the longest pulse duration available (1.50 ms). It is concluded that the bipolar steroid-eluting tined ventricular lead showed stable stimulation thresholds, lead impedance values, and sensing thresholds for 5 years after implantation.

Experimental His-bundle pacing: histopathological and electrophysiological examination

His-bundle pacing gives a more physiological ventricular contraction in comparison to right ventricular apical pacing. However the problems of lead fixation and stability of long-term His-bundle pacing are yet unsolved. We used six adult beagles, in which a screw-in lead was anchored in the His-bundle region for observation of the pacing conditions and histopathologic changes of the conduction system over the course of 2 months. In the results, a satisfactory fixation was obtained using a conventional screw-in lead and no histological influence on the conduction system was observed. The pacing threshold at the time of implantation was 1.15 +/- 0.69 V (3.23 +/- 3.08 mA) in the pulse width of 0.5 ms. R wave amplitude, the impedance and slew rate were 7.28 +/- 2.04 mV, 409 +/- 102 Ohm, and 0.65 +/- 0.41 V/s, respectively. Two months later, these parameters changed to 2.83 +/- 1.06 V (10.4 +/- 5.71 mA), 5.63 +/- 1.62 mV, 310 +/- 71.3 Ohm, and 0.49 +/- 0.22 V/s, respectively. These results suggest the feasibility of clinical application of permanent His-bundle pacing.

Telemetry guided pacemaker programming: impact of output amplitude and the use of low threshold leads on projected pacemaker longevity

In a prospective study, a low threshold screw-in electrode (Medtronic 5078, group I, n = 9) was compared to a conventional active fixation lead (Biotronik Y60BP, group II, n = 9) to investigate whether lower pacing thresholds really translate into longer projected service life of the pacemaker. The leads were implanted in the atrium and were connected to a dual chamber pacing system which included the same ventricular lead (Medtronic 5024) and the same pulse generator model (Intermedics 294-03) in both groups. Eighteen months after implantation, atrial and ventricular pacing thresholds were measured as the charge delivered per pulse [microC] at 0.5, 1.0, 1.5, 2.0, and 3.5 V, respectively. For chronic output programming in both channels, patients capturing at 0.5 V were set to 1.0 V, those capturing at 1.5 V were permanently programmed to 2.0 V with the double of the charge threshold as the safety margin for pacing ("safety charge"). A combination of atrial and ventricular output settings was optimal, if it resulted in minimum battery current drain (microA] as measured by pacemaker telemetry. In both groups, current consumption [microA] decreased significantly as output amplitude was decreased, exhibiting its lowest value at 1.0 V in either channel. All ventricular leads could be programmed to the optimum output amplitude of 1.0 V in groups 1 and 2. As the 2:1 "safety charge" values were almost identical, the ventricular channel essential contributes the same amount to the battery drain of the pacing system in both groups. In the atrium, all patients of group 1 could be programmed to the optimum output amplitude of 1.0 V with an average pulse duration of 0.42 +/- 0.15 ms. In group 2, however, all patients had to be programmed to 2.0 V with a mean pulse width of 0.52 +/- 0.15 ms. With the atrial and ventricular output being optimized, the average battery drain of the whole pacing system was 12.19 +/- 0.63 microA in group 1 versus 14.42 +/- 0.32 microA in group 2 (P < 0.001). As patients were chronically programmed to these output settings, this difference translates into a clinically relevant gain in projected pacemaker longevity of 17 months or 18.3% (121 +/- 4 vs. 104 +/- 2 months; P < 0.001). Thus, programming a 2:1 safety margin in terms of charge and optimizing the output parameters by real-time telemetry of the battery current is a useful approach to reduce battery current drain. Making the most of modern lead technology with a different performance in only one channel of an otherwise identical DDD pacing system translates into a significant prolongation of projected pacemaker service life which is of great importance with the increasing awareness of health care expenditures. The gain in projected longevity is mainly due to the option of reducing the output amplitude which is still significantly beneficial well below the nominal voltage of the power source.

Atrial pacing leads following open heart surgery: active or passive fixation?

The right atrial appendage is often amputated at the time of cardiopulmonary bypass. Because of concerns regarding lead displacement, use of active fixation atrial leads has been recommended in patients who require permanent atrial or dual chamber pacing after open heart surgery. We evaluated the acute and chronic performance of active and passive fixation atrial leads implanted at our institution between 1985 and 1993 in patients with previous open heart surgery. Of 78 consecutive patients, 38 had an active fixation atrial lead, 28 had a passive fixation steroid-eluting lead, and 12 had a passive fixation lead without steroid-eluting properties. At implantation, sensed P wave amplitudes were similar in the three groups, but lead impedance and threshold were significantly higher for active fixation leads compared to all passive fixation leads. During follow-up, atrial pacing thresholds were significantly higher, and sensed P wave amplitudes significantly lower, in the patients with active fixation leads compared to those with passive fixation leads. Loss of sensing occurred in 6 of 38 (16%) patients with active fixation leads and 1 of 40 (2.5%) patients with a passive fixation lead (P = 0.027). Atrial lead displacement occurred in two patients with active fixation leads and one with a passive fixation lead. Comparison with a parallel group of patients without previous open heart surgery demonstrated that atrial lead performance was similar in the two groups. We conclude that, when permanent atrial or dual chamber pacing is necessary in patients with prior open heart surgery, it is appropriate to implant a passive fixation atrial lead except on the infrequent occasions when a stable atrial position cannot be obtained.

Chronic ventricular pacing using an output amplitude of 1.0 volt

Thirty-seven patients (21 male, 16 female, mean age 71 years) received identical DDD pacemakers. They also received the same bipolar ventricular passive fixation electrode, which has a microporous tip of platinum-iridium, a surface area of 5.8 mm2, and steroid elution. Eighteen months after implantation the ventricular charge threshold [microC] was measured telemetrically at 0.5, 1.0, and 2.0 V, respectively. For the 1.0 and 2.0 V amplitudes the pulse duration was increased until the charge per pulse [microC] was twice the threshold value, thus giving a 100% safety margin in terms of charge ("safety charge"). Patients who had ventricular capture at 0.5 V were permanently programmed to 1.0 V (30/37 patients), while those who did not capture at 0.5 V were set to 2.0 V (7/37 patients). In both cases, the pulse duration was programmed according to the rationale of "safety charge." During a routine follow-up period of 6 months, no complications were observed and none of the patients suffered from symptoms indicating loss of ventricular capture. Twenty-four-hour Holter recordings, obtained from all patients at the end of the follow-up with the output parameters unchanged, revealed constant ventricular capture. In patients with chronic stable pacing thresholds and steroid-eluting low threshold leads who have capture at 0.5 V, chronic ventricular pacing at an output amplitude of 1.0 V is feasible, and it seems to be safe if the pacing threshold is measured as charge delivered per pulse and a 100% safety margin in terms of charge is programmed. Reducing the output amplitude to well below the battery voltage may increase pacemaker longevity.

Long-term clinical experience with a steroid-eluting active fixation ventricular electrode in children

In this study, the first study performed in pediatric patients, we assessed the safety and efficacy of a steroid-eluting active fixation ventricular electrode in 18 children. Our study shows that steroid-eluting active fixation leads are safe and effective in children, and suggests that these leads with their easy implantation and low chronic threshold values may be considered as the first choice in this age group.