Search

Background Risk stratification of sudden cardiac death (SCD) in hypertrophic cardiomyopathy (HCM) is mainly based on evaluations from patients at highly specialized centers. Aim To evaluate risk markers for appropriate implantable cardioverter defibrillator (ICD) therapy in an unselected, nationwide cohort of HCM. Methods Patients with an ICD due to HCM were identified from the Swedish ICD Registry since its start in 1995, merged with Patient Register data, and medical records were retrieved. Risk markers for ventricular arrhythmias leading to appropriate ICD therapy were analyzed using Cox proportional hazard ratio (HR). Results Of 321 patients (70.1% males), at least one appropriate therapy occurred in 77 (24.0%) during a mean follow-up of 5.4 years (5.3% per year; primary prevention 4.5%, secondary prevention 7.0%). Cumulative incidences at 1 year, 3 years, and 5 years were 8.1%, 15.3%, and 21.3%, respectively. Cardioversion effectively restored rhythm in 52% of the first episode and antitachycardia pacing was sufficient in the remaining. For the whole cohort, ejection fraction (EF) <50% (HR 2.63; P < 0.001) was associated with appropriate ICD therapy. In primary prevention, patients with established risk markers experienced appropriate therapy; atrial fibrillation (AF; HR 2.54; P = 0.010), EF < 50% (HR 2.78; P = 0.004), and nonsustained ventricular tachycardia (HR 1.80; P = 0.109) had the highest HR, and wall thickness ≥30 mm, syncope, exercise blood pressure response, or family history of SCD had weaker associations. Conclusion ICD therapy successfully terminates ventricular arrhythmias in HCM. In addition to conventional risk markers, a history of AF or EF < 50% may be considered in risk stratification. [ABSTRACT FROM AUTHOR]

Background: Intracardiac impedance (ICZ) has been known to reflect contractile capacity of the heart, and a strong relationship has been documented between stroke volume and ICZ. In this pilot study, conducted in heart failure patients during implantation of a biventricular device, we investigated acute changes in multiple vector ICZ signals during different pacing modes, and whether ICZ can be used to monitor hemodynamic variations. Methods: Z1 and Z2 impedance signals were recorded in the right ventricle (RV), and between the left ventricle (LV) and RV, respectively, in 12 patients during four programming modes. ICZ signals were analyzed with respect to average and peak-to-peak (p2p) amplitude and systolic slope, and correlated with noninvasive hemodynamic and echocardiographic variables. Results: ICZ p2p amplitude decreased during LV stimulation both in Z1 and in Z2 configuration (P = 0.021 and P = 0.022 vs intrinsic conduction, respectively). No significant variations in average amplitude or systolic slope were observed. ICZ variables correlated directly with hemodynamic measures (r = 0.48, P < 0.05, between Z2 p2p amplitude and pulse pressure), LV ejection fraction (r = 0.32, P < 0.05, for Z1 average amplitude), RV ejection fraction (r = 0.75, P < 0.05, for Z1 p2p amplitude), and inversely with ventricular volumes. Conclusions: Variations in ICZ may be observed during different pacing modes and seem to correlate with hemodynamic and echocardiographic variables. Multiple vector ICZ measurement may be a feasible tool for hemodynamic assessment in patients treated with biventricular pacing. [ABSTRACT FROM AUTHOR]

Aims: To evaluate the long-term clinical outcome and device performance of cardiac resynchronization therapy in a consecutive sample of patients with moderate to severe heart failure. Methods and Results: Between 1998 and 2000, forty consecutive patients with drug-refractory heart failure due to ischemic or idiopathic dilated cardiomyopathy were selected for cardiac resynchronization therapy (CRT). After successful implantation of the coronary sinus lead (n = 35, 88%), patients were followed every sixth month by New York Heart Association (NYHA) functional class, the 6-minute walking test (6´ walk), quality of life (QoL, Minnesota), and pacemaker control. NYHA-class and 6´ walk were significantly improved after 6 months and continued to improve gradually until 36 months of follow-up. The QoL improvement at 6 months was sustained over 3 years. After 3 years, the β-blocker dose could be increased in 10/23 patients as compared to baseline. Nine patients had to be re-operated. Coronary sinus lead thresholds were stable over time. Conclusion: The clinical improvements by CRT are sustained over 3 years of follow-up. In the setting of a University Medical Center, CRT can be applied in clinical routine with excellent clinical outcome, acceptable implantation success, and stable device performance over time. [ABSTRACT FROM AUTHOR]

STEINHAUS, D., et. al.: Implant Experience with an Implantable Hemodynamic Monitor for the Management of Symptomatic Heart Failure. Introduction: Management of congestive heart failure is a serious public health problem. The use of implantable hemodynamic monitors (IHMs) may assist in this management by providing continuous ambulatory filling pressure status for optimal volume management. Methods and Results: The Chronicle® system includes an implanted monitor, a pressure sensor lead with passive fixation, an external pressure reference (EPR), and data retrieval and viewing components. The tip of the lead is placed near the right ventricular outflow tract to minimize risk of sensor tissue encapsulation. Implant technique and lead placement is similar to that of a permanent pacemaker. After the system had been successfully implanted in 148 patients, the type and frequency of implant-related adverse events were similar to a single-chamber pacemaker implant. R-wave amplitude was 15.2 ± 6.7 mV and the pressure waveform signal was acceptable in all but two patients in whom presence of artifacts required lead repositioning. Implant procedure time was not influenced by experience, remaining constant throughout the study. Conclusion: Based on this evaluation, permanent placement of an IHM in symptomatic heart failure patients is technically feasible. Further investigation is warranted to evaluate the use of the continuous hemodynamic data in management of heart failure patients. (PACE 2005; 28:747–753) [ABSTRACT FROM AUTHOR]

NOWINSKI, K.,et al.: Pacing-Induced Electrophysiological Remodeling in Hypertrophic Obstructive Cardiomyopathy—Observations on Cardiac Memory. Background:Hypertrophic cardiomyopathy carries an increased risk for sudden cardiac death. While pacing therapy reduces the left ventricular outflow tract gradient and improves symptoms in a subgroup of hypertrophic obstructive cardiomyopathy (HOCM) patients, its electrophysiological consequences are unknown and were therefore assessed in this prospective study.Methods and Results:Fifteen consecutive HOCM patients were studied and compared with 14 patients without HOCM paced because of sinus bradycardia. ECG intervals were measured before pacemaker implantation and after≥3 months of DDD pacing in HOCM patients and≥5 weeks in controls. Both groups showed similar ECG signs of cardiac memory development. In HOCM patients, with baseline QTc 447± 33 ms, cardiac memory development was not associated with any significant changes in ECG intervals. In contrast, baseline repolarization in control patients was significantly prolonged by 6% (QTc 429± 33 vs 454± 46 ms; P<0.05). Furthermore, in HOCM patients repolarization was 7% shorter during DDD pacing compared to sinus rhythm (JTc 329± 25 vs 353± 21 ms; P<0.05), despite a significantly prolonged ventricular activation time (QRS duration 155± 16 vs 91± 9 ms; P<0.01).Conclusions:Importantly, the development of cardiac memory-induced different repolarization responses depending on baseline structure and electrophysiology. In HOCM patients repolarization was shorter during right ventricular apical pacing than during normal activation despite prolonged activation time.(PACE 2005; 28:561–567) [ABSTRACT FROM AUTHOR]

KENNERGREN C., et al.: Clinical Experience with an Automatic Threshold Tracking Algorithm Study. The automatic threshold tracking pacing system algorithm developed by St. Jude Medical, verifies ventricular capture beat by beat by recognizing the evoked response (ER) following each pacemaker stimulus. The present automatic threshold tracking function requires a bipolar ventricular lead with low polarization. The aim of this study was to evaluate a new algorithm developed to use with unipolar leads with different levels of polarization. An external pacemaker with the ability to sense intrinsic R waves and measure ER signals, as well as deliver stimulus, was used. An algorithm for detecting the true ER in a unipolar sensing configuration (tip-case) was developed. Based on the assumption that the true evoked R wave amplitude is independent of the stimulation amplitude, the algorithm calculates and subtracts the polarization present at any pacing stimulus from the measured ER. The resulting signal is analyzed to verify capture. This study comprises 35 patients of which 26 were new implants and 9 had chronic leads. The automatic threshold-tracking algorithm was calibrated for each patient and pacing was performed at different pulse amplitudes and pulse duration. Capture was verified for each paced beat. The recordings were stored for later comparison with the tape-recorded intracardiac heart signals. The new algorithm correctly verified capture or loss of capture for every single analyzed beat at the different pacing outputs in every individual patient. The results from this initial study suggests that the new ER detection principle will allow automatic threshold tracking to be used not only with low polarization bipolar leads but with most leads. (PACE 2003; 26:2219–2224) [ABSTRACT FROM AUTHOR]

This study was designed to prospectively assess ventricular de- and repolarization by the QRS, QT, and JT intervals, and their dispersion in the 12-lead ECG during right ventricular pacing at 60. 70, and 80 beats/min during the first month after AV junctional RE ablation. Previous reports have found early polymorphic ventricular arrhythmia after RF AV junctional ablation. Our hypothesis was that there is a proarrhythmic state following this procedure, which depends on the paced rate and time after ablation. The analysis of the immediate changes was based on 17 patients (10 men) with a mean age of 64 years (SD 14) (range 38-82 years). A 12-lead ECC was recorded during right ventricular pacing at 60, 70, and 80 beats/min within 24 hours (day 1), between 24 and 48 hours (day 2), and 1 week after ablation (day 7). For analysis of changes beyond 1 week, 13 additional patients with a mean age of 73 years (SD 8) (range 62-90 years) were analyzed on days 1, 7, and 30. All intervals were measured with a digitizing table. The mean QRS duration shortened by 2.4% at 60 beats/min (P < 0.01), and the mean QT and JT intervals shortened by 5-7% between days 1 and 7 (P < 0.001), The mean QT was 9% shorter and the mean QT interval was 13% shorter at 80 compared to 60 beats/min on day 1 (P < 0.001). QT dispersion was reduced by 13% when the stimulation rate was increased from 60 to 80 beats/min on day 1 (P < 0.05). There were no significant changes beyond the first week. The study results point to the induction of a proarrhythmic state immediately after AV junctional RE ablation resolving during the first week, Repolarization shortened gradually between 80 and 60 beats/min to an extent that is suggestive of a clinically important antiarrhythmic effect at the higher rate, which was supported also by clinical experience. [ABSTRACT FROM AUTHOR]