Automatic adjustment of stimulation output in resynchronization therapy: impact and effectiveness in clinical practice.

BACKGROUND: Algorithms for automatic pacing output adjustment have been implemented in pacemakers and implantable defibrillators (ICD) and recently in cardiac resynchronization therapy defibrillators (CRT-D). We assessed the impact and effectiveness of these automatic features. METHOD AND RESULTS: We prospectively enrolled patients successfully implanted with the following Medtronic CRT-Ds: Concerto [with automatic left ventricular (LV) output management algorithm], Consulta [automatic management of atrial, right ventricular (RV) and LV voltage], and Sentry (only manual voltage adjustments). Patients with complete device data available for at least 12 months were included in the analysis. We analysed data from 739 patients (360 Sentry, 335 Concerto, 44 Consulta). During the first 6 months, the LV pacing amplitude underwent more frequent adjustments in Concerto (63%, P< 0.001) and Consulta (64%, P= 0.047) patients than in Sentry (48%). Similarly, RV and atrial amplitude at 6 months differed from the pre-discharge value more frequently in Consulta (61 and 50%, respectively) than in Sentry patients (33 and 28%, both P< 0.01). The LV pulse amplitude for Concerto and the voltages in the three chambers of Consulta were significantly lower than the corresponding values programmed in Sentry at 6 and 12 months. The proportion of CRT-D interrogations involving manual reprogramming was 97 ± 8% for Sentry, 79 ± 20% for Concerto, and 56 ± 16% for Consulta (all P< 0.001). CONCLUSIONS: Algorithms for the automatic management of the pacing output reduced pacing output in comparison with the standard manual management approach, with potential optimization of battery longevity. Moreover, they reduced the need to manually reprogram CRT-Ds, suggesting the possibility to simplify CRT-D management and facilitate remote monitoring.

Contribution of morphology discrimination algorithm for improving rhythm discrimination in slow and fast ventricular tachycardia zones in dual-chamber implantable cardioverter-defibrillators.

AIMS: Morphology discrimination (MD) is an algorithm based on QRS morphology analysis, that can be used alone or in various combinations with other discriminators in order to diagnose ventricular tachycardia (VT) [the implantable cardioverter-defibrillator (ICD) may be set to diagnose VT if 'Any' or 'All' the discriminators indicate VT)]. METHODS AND RESULTS: We evaluated the contribution of MD in terms of Specificity (SP) and Sensitivity (SE) of rhythm discrimination in slow and fast VT zones (rates <150 bpm and between 150 and 180 bpm, respectively). Detection results (682 spontaneous episodes in 58 patients) were corrected for multiple episodes within a patient (generalized estimating equations method). Rhythm discrimination in slow VT zones was characterized by SE and SP below 80% without MD, while the use of MD alone allowed to enhance SP, maintaining SE at 96%. Use of MD in combination with other discriminators resulted in a decrease in SP (setting 'Any'). In fast VT zones, MD allows an increase in SE for VT detection from around 82% up to approximately 94%, coupled with an SP of 95-96%., although SP is much higher with MD alone (94.8%) than with any other combination (78.4%). Both in slow and fast VT zones, use of multiple discriminators with the setting 'All' resulted in an unacceptable decrease in SE. CONCLUSION: MD in a dual-chamber ICD in combination with a rate branch classification system makes it possible to achieve a very high SP in discriminating detected events both in slow and fast VT zones, while maintaining SE for VT detection.

Implantable CRT device diagnostics identify patients with increased risk for heart failure hospitalization.

PURPOSE: To determine the association between device-determined diagnostic indices, including intrathoracic impedance, and heart failure (HF) hospitalization. METHODS: Clinical and device diagnostic data of 558 HF patients indicated for CRT-D therapy (In Sync Sentry, Medtronic Inc.) were prospectively collected from 34 centers. Device-recorded intrathoracic impedance fluid index threshold crossing event (TCE), mean activity counts, tachyarrhythmia events, night heart rate (NHR) and heart rate variability (HRV) were compared within patients with vs. without documented HF hospitalization. RESULTS: Mean follow-up was 326 +/- 216 days. Patients hospitalized for HF had significantly higher rates of TCE, a higher percentage of days with the thoracic impedance fluid index above the programmed threshold, a higher percentage of days with low activity, with low HRV or with high NHR. Multivariate analysis showed that TCE resulted in a 36% increased probability of HF hospitalization. Both TCE duration and patient activity were also significantly associated with hospitalization. Kaplan Meier analysis indicated that patients with more TCE events were significantly more likely to be hospitalized (log rank test, p = 0.005). CONCLUSIONS: Decreased intrathoracic impedance, low patient activity and low HRV were all independently associated with increased risk for HF hospitalization in HF patients treated with resynchronization therapy. Device-derived diagnostic data may provide valuable and reliable indices for the prognostic stratification of HF patients.

Cardiac resynchronization therapy in patients undergoing open-chest cardiac surgery.

PURPOSE: Few data are available on the effects of cardiac resynchronization therapy (CRT) in candidates for cardiac surgery and affected by severe heart failure (HF). The aim of our analysis is to evaluate the percentage of patients who maintain indication for CRT after surgery and the efficacy of CRT in those patients subsequently implanted. METHODS: We enrolled 124 HF patients with indication both to heart surgery and to CRT. During surgery, an epicardial left ventricular lead was implanted, tunneled to a subclavear pocket, and capped. Afterward, patients were periodically reassessed to confirm indication for CRT. RESULTS: CRT indication was confirmed within 1 month from surgery in 54 patients (group A) and in 33 patients within 6 months (group B). In group A and B, 63% and 71% of patients were considered responders according to an arbitrary five-point increase of left ventricular ejection fraction (LVEF), respectively. The assessment of clinical response at 1 year, based on the definitions proposed by Packer, identified 63% and 80% of responders in group A and B, respectively. CONCLUSIONS: Our data show that a remarkable percentage of patients maintain an indication for CRT after cardiac surgery (76%), while in the remaining 24% the lack of an indication is confirmed by a higher LVEF at last follow-up. In combination with surgery, CRT proved to be an effective therapy in those patients who were subsequently implanted. The suggested method is simple, without significant adjunctive risks, and allows easier CRT implantation with stable thresholds.

A randomized, double-blind, placebo-controlled study of permanent cardiac pacing for the treatment of recurrent tilt-induced vasovagal syncope. The vasovagal syncope and pacing trial (SYNPACE).

AIMS: Recently, some studies revealed the efficacy of pacemaker implantation in decreasing recurrences in patients with vasovagal syncope. As these studies were not blinded or placebo-controlled, the benefits observed might have been due to a bias in the assessment of outcomes or to a placebo effect of the pacemaker. We performed a randomized, double-blind, placebo-controlled study in order to ascertain if pacing therapy reduces the risk of syncope relapse. METHODS AND RESULTS: Twenty-nine patients (53 +/- 16 years; 19 women) with severe recurrent tilt-induced vasovagal syncope (median 12 syncopes in the lifetime) and 1 syncopal relapse after head-up tilt testing underwent implantation of a pacemaker, and were randomized to pacemaker ON or to pacemaker OFF. During a median of 715 days of follow-up, 8 (50%) patients randomized to pacemaker ON had recurrence of syncope compared to 5 (38%) of patients randomized to pacemaker OFF (p = n.s.); the median time to first syncope was longer in the pacemaker ON than in pacemaker OFF group, although not significantly so (97 [38-144] vs 20 [4-302] days; p = 0.38). There was also no significant difference in the subgroups of patients who had had a mixed response and in those who had had an asystolic response during head-up tilt testing. CONCLUSION: Our data were unable to show a superiority of active pacing versus inactive pacing in preventing syncopal recurrence in patients with severe recurrent tilt-induced vasovagal syncope.