Long-term electrical performance of Attain Performa quadripolar left ventricular leads with all steroid-eluting electrodes: Results from a large worldwide clinical trial.

BACKGROUND: Steroid-eluting (SE) electrodes suppress local inflammation and lower pacing capture thresholds (PCT); however, their effectiveness on quadripolar left ventricular (LV) leads in the cardiac vein is not fully studied. We evaluated the effectiveness of SE on all four LV pacing electrodes in human subjects enrolled in the Medtronic Attain® Performa™ quadripolar LV lead study. METHODS: A total of 1,097 subjects were included in this evaluation. At each follow-up visit (1, 3, 6, and 12 months), LV PCT and pacing impedance were measured using either manual or automated testing methods. Summary statistics for PCT and impedance values were obtained for implant and each scheduled follow-up visit for all lead models. RESULTS: Average extended bipolar (LV electrode to right ventricular Coil) PCTs for the four LV SE pacing electrodes (LV1, LV2, LV3, and LV4) on the three shapes of the quadripolar LV leads were 1.06 ± 0.97 V, 1.38 ± 1.26 V, 1.51 ± 1.33 V, and 2.25 ± 1.63 V, respectively, at 0.5-ms pulse width. PCTs remained low and stable throughout the 12-month follow-up period. CONCLUSION: This clinical trial demonstrated that SE on all LV pacing electrodes is associated with low and stable PCTs for all quadripolar LV lead electrodes, resulting in multiple viable vectors for LV pacing. The large number of available vectors facilitates basal pacing, avoidance of PNS, and potentially prolongs generator longevity due to lower PCTs.

Body surface mapping using an ECG belt to characterize electrical heterogeneity for different left ventricular pacing sites during cardiac resynchronization: Relationship with acute hemodynamic improvement.

BACKGROUND: Electrical heterogeneity (EH) during cardiac resynchronization therapy may vary with different left ventricular (LV) pacing sites. OBJECTIVE: The purpose of this study was to evaluate the relationship between such changes and acute hemodynamic response (AHR). METHODS: Two EH metrics-standard deviation of activation times and mean left thorax activation times-were computed from isochronal maps based on 53-electrode body surface mapping during baseline AAI pacing and biventricular (BiV) pacing from different pacing sites in coronary veins in 40 cardiac resynchronization therapy-indicated patients. AHR at different sites was evaluated by invasive measurement of LV-dp/dtmax at baseline and BiV pacing, along with right ventricular (RV)-LV sensing delays and QRS duration. RESULTS: The site with the greatest combined reduction in standard deviation of activation times and left thorax activation times from baseline to BiV pacing was hemodynamically optimal (defined by AHR equal to, or within 5% of, the largest dp/dt response) in 35 of 40 patients (88%). Sites with the longest RV-LV and narrowest paced QRS were hemodynamically optimal in 26 of 40 patients (65%) and 28 of 40 patients (70%), respectively. EH metrics from isochronal maps had much better accuracy (sensitivity 90%, specificity 80%) for identifying hemodynamically responsive sites (∆LV dp/dtmax ≥10%) compared with RV-LV delay (69%, 85%) or paced QRS reduction (52%, 76%). Multivariate prediction model based on EH metrics showed significant correlation (R2 = 0.53, P <.001) between predicted and measured AHR. CONCLUSION: Changes in EH from baseline to BiV pacing more accurately identified hemodynamically optimal sites than RV-LV delays or paced QRS shortening. Optimization of LV lead location by minimizing EH during BiV pacing, based on body surface mapping, may improve CRT response.

Effect of insulation material in aging pacing leads: comparison of impedance and other electricals: time-dependent pacemaker insulation changes.

BACKGROUND: There has been concern over declining bipolar (BP) impedance (Z) in aging polyurethane (PU) cardiac pacing leads. Subsequently, a prospective study was conducted comparing BP Z, threshold (Th), and R-wave sensing amplitude of 55D PU-insulated (Model 4024, Medtronic, Inc., Minneapolis, MN, USA) and silicone-insulated (Model 5024) leads. METHODS: This study was initiated by The Iowa Heart Center. Patients with Model 4024 (N = 162) or 5024 (N = 120) pacing leads with at least 6 years implant time were enrolled and followed for an additional 5 years. RESULTS: There was a significant drop in the mean BP Z for the Model 4024 population, between enrollment (6 years) and the final endpoint (11 years), which was in contrast to the Model 5024 which did not see a significant drop in its mean BP Z for this same period. The trend difference seen in the means between the two models was statistically significant (P < 0.0001). In addition, a statistically significant relationship was found between dropping BP Z and rising Th (P < 0.0001). The analysis showed that if BP Z dropped below 200 ohms, the probability of having a >3X increase over baseline, in Th at 2.5 V, increases from approximately 3-7% to as high as 30%. CONCLUSIONS: A significant drop in BP Z observed in the PU-insulated Model 4024 lead was not present in the silicone-insulated Model 5024 lead. The statistically significant relationship between dropping BP Z and rising Th helps to understand how to better manage patients with aging leads.

Magnetic resonance imaging in patients with a pacemaker system designed for the magnetic resonance environment.

BACKGROUND: Magnetic resonance imaging (MRI) of pacemaker patients is contraindicated due to documented potential risks to the patient from hazardous interactions between the MRI and pacemaker system. OBJECTIVE: The purpose of this prospective, randomized, controlled, worldwide clinical trial was to evaluate the safety and effectiveness of a pacemaker system designed for safe use in MRI for any bradycardia indicated patient. METHODS: Patients (n = 464) were randomized to undergo an MRI scan between 9 and 12 weeks postimplant (MRI group, n = 258) or not to undergo MRI (control group, n = 206) after successful implantation of the specially designed dual-chamber pacemaker and leads. Patients were monitored for arrhythmias, symptoms, and pacemaker system function during 14 nonclinically indicated relevant brain and lumbar MRI sequences. Sequences were performed at 1.5 T and included scans with high radiofrequency power deposition and/or high gradient dB/dt exposure. Clinical evaluation of the pacemaker system function occurred immediately before and after MRI, 1 week and 1 month post-MRI, and at corresponding times for the control group. Primary endpoints for safety analyzed the MRI procedure complication-free rate and for effectiveness compared capture and sensing performance between MRI and control groups. RESULTS: No MRI-related complications occurred during or after MRI, including sustained ventricular arrhythmias, pacemaker inhibition or output failures, electrical resets, or other pacemaker malfunctions. Pacing capture threshold and sensed electrogram amplitude changes were minimal and similar between study groups. CONCLUSION: This trial documented the ability of this pacemaker system to be exposed in a controlled fashion to MRI in a 1.5 T scanner without adverse impact on patient outcomes or pacemaker system function.

Clinical benefits of remote versus transtelephonic monitoring of implanted pacemakers.

OBJECTIVES: The purpose of this study was to evaluate remote pacemaker interrogation for the earlier diagnosis of clinically actionable events compared with traditional transtelephonic monitoring and routine in-person evaluation. BACKGROUND: Pacemaker patient follow-up procedures have evolved from evaluating devices with little programmability and diagnostic information solely in person to transtelephonic rhythm strip recordings that allow monitoring of basic device function. More recently developed remote monitoring technology leverages expanded device capabilities, augmenting traditional transtelephonic monitoring to evaluate patients via full device interrogation. METHODS: The time to first diagnosis of a clinically actionable event was compared in patients who were followed by remote interrogation (Remote) and those who were followed per standard of care with office visits augmented by transtelephonic monitoring (Control). Patients were randomized 2:1. Remote arm patients transmitted pacemaker information at 3-month intervals. Control arm patients with a single-chamber pacemaker transmitted at 2-month intervals. Control arm patients with dual-chamber devices transmitted at 2-month intervals with an office visit at 6 months. All patients were seen in office at 12 months. RESULTS: The mean time to first diagnosis of clinically actionable events was earlier in the Remote arm (5.7 months) than in the Control arm (7.7 months). Three (2%) of the 190 events in the Control arm and 446 (66%) of 676 events in the Remote arm were identified remotely. CONCLUSIONS: The strategic use of remote pacemaker interrogation follow-up detects actionable events that are potentially important more quickly and more frequently than transtelephonic rhythm strip recordings. The use of transtelephonic rhythm strips for pacemaker follow-up is of little value except for battery status determinations. (PREFER [Pacemaker Remote Follow-up Evaluation and Review]; NCT00294645).

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.

Design of the Pacemaker REmote Follow-up Evaluation and Review (PREFER) trial to assess the clinical value of the remote pacemaker interrogation in the management of pacemaker patients.

BACKGROUND: Although pacemakers are primarily used for the treatment of bradycardia, diagnostic data available in current pacemakers allow them to be also used as sophisticated, continuous monitoring devices. Easy access to these stored data may assist clinicians in making diagnostic and therapeutic decisions sooner, thus avoiding potential long-term sequelae due to untreated clinical disorders. Internet-based remote device interrogation systems provide clinicians with frequent and complete access to stored data in pacemakers. In addition to monitoring device function, remote monitors may be a helpful tool in assisting physicians in the management of common arrhythmia disorders. METHODS: The Pacemaker REmote Follow-up Evaluation and Review (PREFER) trial is a prospective, randomized, parallel, unblinded, multicenter, open label clinical trial to determine the utility of remote pacemaker interrogation in the earlier diagnosis of clinically actionable events compared to the existing practice of transtelephonic monitoring. There have been 980 patients enrolled and randomized to receive pacemaker follow up with either remote interrogation using the Medtronic CareLink(R) Network (CareLink) versus the conventional method of transtelephonic monitoring (TTM) in addition to periodic in-person interrogation and programming evaluations. The purpose of this manuscript is to describe the design of the PREFER trial. The results, to be presented separately, will characterize the number of clinically actionable events as a result of pacemaker follow-up using remote interrogation instead of TTM. TRIAL REGISTRATION: ClinicalTrials.gov: NCT00294645.

Optimizing implantable cardioverter-defibrillator treatment of rapid ventricular tachycardia: antitachycardia pacing therapy during charging.

BACKGROUND: Previous studies in implantable cardioverter-defibrillator (ICD) patients demonstrated the efficacy and safety of antitachycardia pacing (ATP) for rapid ventricular tachycardias (VT). To prevent shock delay in case of ATP failure, a new feature (ATP during charging) was developed to deliver ATP for rapid VT while charging for shock. OBJECTIVE: The purpose of this study was to determine the efficacy and safety of this new feature. METHODS: In a prospective, nonrandomized trial, patients with standard ICD indication received an EnTrust ICD. VT and ventricular fibrillation (VF) episodes were reviewed for appropriate detection, ATP success, rhythm acceleration, and related symptoms. RESULTS: In 421 implanted patients, 116 VF episodes occurred in 37 patients. Eighty-four (72%) episodes received ATP during or before charging. ATP prevented a shock in 58 (69%) of 84 episodes in 15 patients. ATP stopped significantly more monomorphic (77%) than polymorphic VTs (44%, P = .05). Five (6%) episodes accelerated after ATP but were terminated by the backup shock(s). No symptoms were related to ATP during charging. In four patients, 38 charges were saved by delivering ATP before charging. Of 98 induced VF episodes, 28% were successfully terminated by ATP versus 69% for spontaneous episodes (P <.01). CONCLUSION: Most VTs detected in the VF zone can be painlessly terminated by ATP delivered during charging, with a low risk of acceleration or symptoms. ATP before charging allows delivery of two ATP attempts before shock in the same time that would otherwise be required to deliver only one ATP plus a shock. It also offers potential battery energy savings.