Stimulation rate and the optimal interventricular interval during cardiac resynchronization therapy in patients with chronic atrial fibrillation

Background: Optimization of cardiac resynchronization therapy (CRT) with respect to the interventricular (V‐V) interval is mainly limited to pacing at a resting heart rate. We studied the effect of higher stimulation rates with univentricular and biventricular (BiV) pacing modes including the effect of the V‐V interval optimization. Methods: In 36 patients with heart failure and chronic atrial fibrillation (AF), the effects of right ventricular (RV), left ventricular (LV), simultaneous BiV, and optimized sequential BiV (BiVopt) pacing were measured. The effect of the pacing mode and the optimal V‐V interval was determined at stimulation rates of 70, 90, and 110 ppm using invasive measurement of the maximum rate of left ventricular pressure rise (LV dP/dt_max). Results: The average LV dP/dt _max for all pacing modalities at stimulation rates of 70, 90, and 110 ppm was 781 ± 176, 833 ± 197, and 884 ± 223 mmHg/s for RV pacing; 893 ± 178, 942 ± 186, and 981 ± 194 mmHg/s for LV pacing; 904 ± 179, 973 ± 187, and 1052 ± 206 mmHg/s for simultaneous BiV pacing; and 941 ± 186, 1010 ± 198, and 1081 ± 206 mmHg/s for BiVopt pacing, respectively. In BiVopt pacing, the corresponding optimal V‐V interval decreased from 34 ± 29, 28 ± 28, and 21 ± 27 ms at stimulation rates of 70, 90, and 110 ppm, respectively . In two individuals, LV dP/dt_max decreased when the pacing rate was increased from 90 to 110 ppm. Conclusion: In patients with AF and heart failure, LV dP/dt_max increases for all pacing modalities at increasing stimulation rates in most, but not all, patients. The rise in LV dP/dt_max with increasing stimulation rates is higher in biventricular (BiV and BiVopt) than in univentricular (LV and RV) pacing. The optimal V‐V interval at sequential biventricular pacing decreases with increasing stimulation rates.     

Ventricular activation sequence during left ventricular pacing promotes QRS complex oversensing in the atrial channel

Background: Left ventricular (LV)‐only pacing has a significant effect on delay in depolarization of parts of the ventricles that are likely oversensed in the right atrial channel. The study aimed to assess the impact of ventricular activation sequence on QRS oversensing and far‐field endless‐loop pacemaker tachycardia (ELT) in patients who received cardiac resynchronization therapy (CRT) devices. Methods: The study examined 102 patients with CRT devices. Oversensing artifacts in the atrial channel were inspected on intracardiac electrograms, and their timing with respect to the beginning of QRS was determined during DDD‐right ventricular (RV), DDD‐LV, DDD‐biventricular (BiV), and AAI pacing modes. The occurrence of ELT during DDD‐LV pacing with a postventricular atrial refractory period (PVARP) of 250 ms was also assessed. Results: The timing of oversensing artifacts (in relation to the beginning of surface QRS) was dependent on ventricular activation sequence, occurring promptly following intrinsic activation via the right bundle branch (47.1 ± 26.4 ms), later during RV pacing (108.7 ± 22.5 ms) or BiV pacing (109.4 ± 23.1 ms), and significantly later, corresponding to the final part of the QRS, during LV pacing (209.6 ± 40.0 ms, range: 140–340 ms, P < 0.001). Oversensing was significantly more frequent during LV than during RV pacing (35.3% vs 22.5%, P < 0.001). Far‐field ELT was observed in six patients. Conclusions: Oversensing artifacts in the atrial channel are likely caused by depolarization of the basal part of the right ventricle. The novel mechanism of QRS oversensing outside PVARP, caused by a reversed ventricular activation sequence during LV‐only pacing, may be important in some CRT patients. (PACE 2011; 34:1682–1686)     

The hemodynamic effect of right ventricle (RV), RT3DE targeted left ventricle (LV) and biventricular (BIV) pacing in the early postoperative period after cardiac surgery

Background: Congestive heart failure negatively impacts the prognosis in patients after cardiac surgery. The aim of our study was to assess the value of targeted cardiac resynchronization therapy (CRT) within 72 hours after cardiac surgery in patients with mechanical dyssynchrony, who had an ejection fraction ≤ 35%, QRS ≥150 ms or between 120 and 150 ms. Methods: A prospective randomized trial based on three‐dimensional echocardiography (RT3DE) and optimized sequential dual‐chamber (DDD ) pacing in patients after cardiac surgery. DDD epicardial pacing (Medtronic coaxial epicardial leads 6495) was provided by a modified Medtronic INSYNC III Pacemaker (Medtronic Inc., Minneapolis, MN, USA). Summary of results: The study included 21 patients with ischemic heart disease (HD) or valvular HD (16 men, 5 women, average age 69 years) with left ventricle (LV) dysfunction after cardiac surgery . Patients with biventricular (BIV) (CO 6.7 ± 1.7 L/min, CI 3.5 ± 0.8 L/min/m²) and LV (CO 6.2 ± 1.5 L/min, CI 3.2 ± 0.7 L/min/m²) pacing had statistically significantly higher CO and CI than patients with right ventricular (RV) (CO 5.4 ± 1.4 L/min, CI 2.8 ± 0.6 L/min/m²) pacing (BIV vs RV P ≤ 0.001; LV vs RV P ≤ 0.05; BIV vs LV P ≤ 0.05). Conclusions: RT3DE targeted and optimized CRT in the early postperative period after cardiac surgery provided better hemodynamic results than RV pacing. (PACE 2011; 34:1231–1240)     

Transseptal left ventricular endocardial pacing reduces dispersion of ventricular repolarization

Background: Cardiac resynchronization therapy (CRT) may be proarrhythmic in some patients. This may be due to the effect of left ventricular (LV) epicardial pacing on ventricular repolarization. The purpose of this study was to evaluate the effect of endocardial versus epicardial LV biventricular pacing on surface electrocardiogram (ECG) parameters that are known markers of arrhythmogenic repolarization. Methods: ECG markers of repolarization (QT dispersion, QTD; T peak to end, T_peak‐end; T_peak‐end dispersion, T_peak‐endD; QTc) were retrospectively measured before and after CRT in seven patients with transseptal LV endocardial leads (TS group), 28 matched patients with coronary sinus (CS) LV leads (CS group), and eight patients with surgical LV epicardial leads (SUR group). All ECGs were scanned and analyzed using digital callipers. Results: Compared to the CS group, the TS group CRT was associated with a significant postpacing reduction in QTD (?45.2 ± 35.6 vs ?4.3 ± 43.6 ms, P = 0.03) and T_peak‐end (?24.2 ± 22.1 vs 3.4 ± 26.7 ms, P = 0.02). There was a nonsignificant post‐CRT reduction in both T_peak‐endD (?11.3 ± 31.0 vs 2.4 ± 28.9 ms, P = 0.27) and QTc (?50.0 ± 46.4 vs 4.4 ± 70.2 ms, P = 0.06) in the TS versus the CS group. In contrast, there were no differences between the SUR and CS groups in terms of the effect of CRT on these repolarization parameters. Conclusions: CRT with (atrial transseptal) endocardial LV lead placement is associated with repolarization characteristics that are considered to be less arrhythmogenic than those generated by CS (epicardial) LV lead placement. Further work is needed to determine whether these changes translate to a reduction in proarrhythmia. (PACE 2011; 34:1258–1266)     

Long‐Term Effects of Upgrading to Biventricular Pacing: Differences with Cardiac Resynchronization Therapy as Primary Indication

Background: Few studies have assessed the long‐term effects of cardiac resynchronization therapy (CRT) in patients with advanced heart failure (HF) and previously right ventricular apical pacing (RVAP). Aims: To assess the clinical and hemodynamic impact of upgrading to biventricular pacing in patients with severe HF and permanent RVAP in comparison with patients who had CRT implantation as initial therapy. Methods and Results: Thirty‐nine patients with RVAP, advanced HF (New York Heart Association [NYHA] III–IV), and severe depression of left ventricular ejection fraction (LVEF) were upgraded to biventricular pacing (group A). Mean duration of RVAP before upgrading was 41.8 ± 13.3 months. Clinical and echocardiographic results were compared to those obtained in a group of 43 patients with left bundle branch block and similar clinical characteristics undergoing “primary” CRT (group B). Mean follow‐up was 35 ± 10 months in patients of group A and 38 ± 12 months in group B. NYHA class significantly improved in groups A and B. LVEF increased from 0.23 ± 0.07 to 0.36 ± 0.09 (P < 0.001) and from 0.26 ± 0.02 to 0.34 ± 0.10 (P < 0.001), respectively. Hospitalizations were reduced by 81% and 77% (P < 0.001). Similar improvements in echocardiographic signs of ventricular desynchronization were also observed. Conclusion: Patients upgraded to CRT exhibit long‐term clinical and hemodynamic benefits that are similar to those observed in patients treated with CRT as initial strategy. (PACE 2010; 841–849)     

Greater three-dimensional ventricular lead tip separation is associated with improved outcome after cardiac resynchronization therapy

Background: Effective cardiac resynchronization therapy (CRT) is more likely with widely separated left ventricular (LV) and right ventricular (RV) pacing leads tips. We hypothesized that lead separation is an important factor in determining the clinical response to CRT. Methods: A retrospective study of 86 consecutive patients age 71 ± 10 years, male (74%), coronary disease (71%), atrial fibrillation (23%), LV ejection fraction (22 ± 9%), QRS duration (160 ± 27 ms), New York Heart Association (NYHA) class III (81%), NYHA class IV (19%) undergoing CRT from January 2006 to September 2008. The median follow‐up was 12 months and clinical response to CRT was defined as reduction of NYHA class by one or more. The three‐dimensional separation between RV and LV pacing lead tips was calculated using measurements obtained from orthogonal posteroanterior and lateral chest radiographs performed the day after implantation. Results: Fifty‐nine patients (69%) responded to CRT. There was a statistically significant association between increased three‐dimensional lead separation and clinical response to CRT (P= 0.005). Stronger association was obtained when lead separation was corrected for cardiac size (P= 0.001). A significantly higher response rate of 88% was achieved in patients with QRS duration of 160 ms or more, and lead separation of 100 mm or more compared with 60% when lead separation was less than 100 mm and QRS duration remained the same (P = 0.027). Conclusions: Greater three‐dimensional separation of LV‐to‐RV leads is associated with improved response to CRT. A prospective multicenter trial is needed to assess lead separation as a predictor for response. (PACE 2010; 33:1490–1496)     

Acute hemodynamic effects of right and left ventricular lead positions during the implantation of cardiac resynchronization therapy defibrillators

Background: To evaluate the acute hemodynamic effects of different right (RV) and left ventricular (LV) pacing sites in patients undergoing the implantation of a cardiac resynchronization therapy defibrillator (CRT‐D). Methods: Stroke volume index (SVI), assessed via pulse contour analysis, and dp/dt max, obtained in the abdominal aorta, were analyzed in 21 patients with New York Heart Association class III heart failure and left bundle branch block (mean ejection fraction of 24 ± 6%), scheduled for CRT‐D implantation under general anesthesia. We compared the hemodynamic effects of RV apical (A), RV septal (B), and biventricular pacing using the worst (lowest SVI; C) and best (highest SVI; D) coronary sinus lead positions. Results: Mean arterial pressure, SVI, and dp/dt max did not differ significantly between RV apical and septal pacing. Dp/dt max and SVI increased significantly during biventricular pacing (dp/dt max: B, 588 ± 160 mmHg/s; C, 651 ± 218 mmHg/s, P = 0.03 vs B; D, 690 ± 220 mmHg/s, P = 0.02 vs C; SVI: B, 33.6 ± 5.5 mL/m², C, 34.8 ± 6.1 mL/m², P = 0.08 vs B, D 36.0 ± 6.0 mL/m², P < 0.001 vs C). The best hemodynamic response was associated with lateral or inferior lead positions in 15 patients. Other LV lead positions were most effective in six patients. Conclusions: The optimal LV lead position varies significantly among patients and should be individually determined during CRT‐D implantation. The impact of the RV stimulation site in patients with intraventricular conduction delay, undergoing CRT‐D implantation, has to be investigated in further studies. (PACE 2011; 34:1537–1543)     

Pacemaker optimization in nonresponders to cardiac resynchronization therapy: left ventricular pacing as an available option

Background: Echocardiographic (ECHO)‐guided pacemaker optimization (PMO) in cardiac resynchronization therapy (CRT) nonresponders acutely improves left ventricular (LV) function. However, the chronic results of LV pacing in this group are less understood. Methods: We retrospectively studied 28 CRT nonresponders optimized based on ECHO to LV pacing and compared them to 28 age‐ and gender‐matched patients optimized to biventricular (BiV) pacing. ECHOs with tissue Doppler imaging assessed LV hemodynamics before, immediately after, and 29 ± 16 months after PMO. Also, 56 age‐ and gender‐matched CRT responders were included for comparison of clinical outcomes. Results: PMO resulted in acute improvements in longitudinal LV systolic function and several measures of dyssynchrony, with greater improvements in the LV paced group. Chronic improvements in ejection fraction (EF) (3.2 ± 7.7%), and left ventricle end‐systolic volume (LVESV) (?11 ± 36 mL) and one dyssynchrony measure were seen in the combined group. Chronically, both LV and BiV paced patients improved some measures of systolic function and dyssynchrony although response varied between the groups. Survival at 3.5 years was similar (P = 0.973) between the PMO (58%) and nonoptimized groups (58%) but survival free of cardiovascular hospitalization was significantly (P = 0.037) better in the nonoptimized group. Conclusions : CRT nonresponders undergoing PMO to either LV or BiV pacing have acute improvements in longitudinal systolic function and some measures of dyssynchrony. Some benefits are sustained chronically, with improvements in EF, LVESV, and dyssynchrony. A strategy of ECHO‐guided PMO results in survival for CRT nonresponders similar to that of CRT patients not referred for PMO. (PACE 2012; 35:685–694))     

Advantage of Optimizing V‐V Timing in Cardiac Resynchronization Therapy Devices

Background: There is little consensus as to the benefits of interventricular (V‐V) timing optimization in cardiac resynchronization therapy (CRT). A variety of parameters are currently used to optimize device timing. This study was designed to investigate the potential advantage of using 3D ejection fraction (EF) and aortic velocity‐time integral (VTI) as measures of global left ventricular (LV) function to optimize ventricular activation in CRT devices. Methods: Seventy‐four patients seen in the Optimization Clinic with adequate echocardiographic images were included. Three aortic VTI and two 3D EF values were recorded at five V‐V settings and the average value used. Aortic VTI and 3D EF were classified as the best, worst, and simultaneous setting values. Data were analyzed using a two‐tailed paired t‐test. Results: Comparing the best to worst V‐V timing settings, VTI improved by 4.7 ± 7.5 cm (P < 0.0001) and 3D EF by 9.9%± 5.7% (P < 0.0001). Comparing the simultaneous setting to the best V‐V timing setting, VTI improved by 2.4 ± 2.1 cm (P < 0.0001) and 3D EF by 3.8%± 4.9% (P < 0.0001). Aortic VTI improved in 85% of patients and 3D EF improved in 72%. However, only 26% of the patients had the same optimal setting using aortic VTI and 3D EF yielding an r² value of 0.003. Conclusions: Individualized echocardiographic V‐V optimization of CRT devices improves global LV function as measured by aortic VTI and 3D EF. Substantial differences in function were seen over an 80‐ms range of V‐V timing and optimization resulted in improved LV function in the majority of patients. (PACE 2010; 33:1161–1168)     

Improvement in right ventricular systolic function after cardiac resynchronization therapy correlates with left ventricular reverse remodeling

Background: Cardiac resynchronization therapy (CRT) improves left ventricular (LV) systolic function in heart failure (HF). However, the effects of CRT on right ventricular (RV) systolic function are not fully understood. Objective: We aimed to determine echocardiographic correlates of improvement in RV systolic function after CRT. Methods: Fifty‐four patients (61.9 ± 10.5 years; 43 men; LV ejection fraction 24.6 ± 4.0%; QRS duration > 120 ms) with HF were enrolled. Standard echocardiography, strain rate (SR), and tissue Doppler imaging were performed in all patients before and 6 months after CRT. Pulsed‐wave TDI‐derived systolic indices of RV included systolic (RV_S) and isovolumic velocity (RV_IVV) and isovolumic acceleration (RV_IVA). Response to CRT was defined as decline in LV end‐systolic volume (LVESV) ≥ 10%. Results: When indices of RV systolic function were assessed between responders and nonresponders, in responders (38 patients, 70.4%) RV end‐diastolic diameters (RVD1–3), mid‐RV strain, and mid‐RV SR improved significantly (P < 0.01, for all). RV_S (10.77 ± 4.29 vs 12.62 ± 4.10 cm/sec, P = 0.005), RV_IVV (14.71 ± 5.88 vs 18.52 ± 6.62 cm/sec, P < 0.001), and RV_IVA (1.69 ± 0.70 vs 2.39 ± 0.77 m/sec², P < 0.001) significantly increased among responders. There was no significant change in these parameters among nonresponders. Pearson's analyses revealed moderate positive correlations between reduction of LVESV and ΔRV_IVV (r = 0.467, P = 0.001) and ΔRV_IVA (r = 0.473, P = 0.001), respectively. Conclusions: RV diameters and systolic indices after CRT improved only in the responder group. Improvement in RV systolic performance after CRT is correlated with the reduction of LVESV. (PACE 2011; 34:200–207)     

Long‐Term Nonoutflow Septal Versus Apical Right Ventricular Pacing: Relation to Left Ventricular Dyssynchrony

Background: Right ventricular (RV) apical pacing deteriorates left ventricular (LV) function. RV nonoutflow (low) septal pacing may better preserve ventricular performance, but this has not been systematically tested. Our aim was to assess (1) whether long‐term RV lower septal pacing is superior to RV apical pacing regarding LV volumes and ejection fraction (EF), and (2) if the changes in LV dyssynchrony imposed by pacing are related to the long‐term changes in LV volumes and EF. Methods: In thirty‐six patients with atrioventricular (AV) block, a dual‐chamber pacemaker was implanted. The ventricular electrode was placed either at the apex or at the lower septum, in a randomized sequence. Twenty‐four to 48 hours following implantation, we measured LV volumes, EF, and LV dyssynchrony (by tissue Doppler imaging), both with and without pacing. Patients were reassessed echocardiographically after 12 months. Results: Lower septal pacing induced a more synchronized pattern of LV contraction changes (P < 0.05). Following 12 months, differences were observed between groups regarding LV volumes and EF. EF increased within the septal group (from 52 ± 3.3% to 59 ± 3.0%, P < 0.05). A significant inverse relation was documented between changes in LV dyssynchrony and changes in EF (r =?0.64, P < 0.05). Conclusions: In patients with AV block, RV nonoutflow septal pacing represents an attractive alternative, since it preserves better and may even improve LV volumes and EF. Late changes in EF are associated with the changes in LV dyssynchrony imposed by pacing.     

Effect of pacing-induced ventricular dyssynchrony on right ventricular function

Background: Asynchronous electrical activation induced by right ventricular (RV) pacing can cause several abnormalities in left ventricular (LV) function. However, the effect of ventricular pacing on RV function has not been well established. We evaluated RV function in patients undergoing long‐term RV pacing. Methods: Eighty‐five patients and 24 healthy controls were included. After pacemaker implantation, conventional echocardiography and strain imaging were used to analyze RV function. Strain imaging measurements included peak systolic strain and strain rate. LV function and ventricular dyssynchrony by tissue Doppler imaging (TDI) were assessed. Intra‐ and interobserver variabilities of TDI parameters were tested on 15 randomly selected cases. Results: All patients were in New York Heart Association functional class I or II and percentage of ventricular pacing was 96 ± 4%. RV apical induced interventricular dyssynchrony in 49 patients (60%). LV dyssynchrony was found in 51 patients (60%), when the parameter examined was the standard deviation of the time to peak myocardial systolic velocity of all 12 segments greater than 34 ms. Likewise, septal‐to‐lateral delay ≥65 ms was found in 31 patients (36%). All echocardiographic indexes of RV function were similar between patients and controls (strain: ?22.8 ± 5.8% vs ?22.1 ± 5.6%, P = 0.630; strain rate: ?1.47 ± 0.91 s^?1 vs ?1.42 ± 0.39 s^?1, P = 0.702). Intra‐ and interobserver variability for RV strain was 3.1% and 5.3%, and strain rate was 1.3% and 2.1%, respectively. Conclusions: In patients with standard pacing indications, RV apical pacing did not seem to affect RV systolic function, despite induction of electromechanical dyssynchrony. (PACE 2011; 34:155–162)     

Interatrial conduction correlates with optimal atrioventricular timing in cardiac resynchronization therapy devices

Background: Echocardiographic optimization of the atrioventricular delay (AV) may result in improvement in cardiac resynchronization therapy (CRT) outcome. Optimal AV has been shown to correlate with interatrial conduction time (IACT) during right atrial pacing. This study aimed to prospectively validate the correlation at different paced heart rates and examine it during sinus rhythm (Sinus). Methods: An electrophysiology catheter was placed in the coronary sinus (CS) during CRT implant (n = 33). IACT was measured during Sinus and atrial pacing at 5 beats per minute (bpm) and 20 bpm above the sinus rate as the interval from atrial sensing or pacing to the beginning of the left atrial activation in the CS electrogram. P‐wave duration (PWd) was measured from 12‐lead surface electrocardiogram, and the interval from the right atrial to intrinsic right ventricular activation (RA‐RV) was measured from device electrograms. Within 3 weeks after the implant patients underwent echocardiographic optimization of the sensed and paced AVs by the mitral inflow method. Results: Optimal sensed and paced AVs were 129 ± 19 ms and 175 ± 24 ms, respectively, and correlated with IACT during Sinus (R = 0.76, P < 0.0001) and atrial pacing (R = 0.75, P < 0.0001), respectively. They also moderately correlated with PWd (R = 0.60, P = 0.0003 during Sinus and R = 0.66, P < 0.0001 during atrial pacing) and RA‐RV interval (R = 0.47, P = 0.009 during Sinus and R = 0.66, P < 0.0001 during atrial pacing). The electrical intervals were prolonged by the increased atrial pacing rate. Conclusion: IACT is a critical determinant of the optimal AV for CRT programming. Heart rate‐dependent AV shortening may not be appropriate for CRT patients during atrial pacing. (PACE 2011; 34:443–449)     

Invasive optimization of cardiac resynchronization therapy: role of sequential biventricular and left ventricular pacing

BACKGROUND: Aim of this invasive study was to characterize and quantify changes in left ventricular (LV) systolic function due to sequential biventricular pacing (BV) as compared to right atrial triggered simultaneous BV (BV(0)), LV, and right ventricular (RV) pacing in patients with congestive heart failure (CHF). METHODS: In 22 CHF patients, all in sinus rhythm, temporary multisite pacing was performed prior to implantation of a permanent system. LV systolic function was evaluated invasively by the maximum rate of LV pressure increase (dP/dt(max)). Sequential BV pacing was performed with preactivation of either ventricle at 20-80 ms. RESULTS: In comparison to RV pacing, LV and BV(0) pacing increased dP/dt(max) by 33.9 +/- 19.3% and 34.0 +/- 22.6%, respectively (P < 0.001). In 9 patients, optimized sequential BV pacing further improved dP/dt(max) by 8.5 +/- 4.8% compared to BV(0) (range 3.3-17.1, P < 0.05). In 10 patients exhibiting a PR interval < or =200 ms, LV pacing was either superior (n = 6) or equal to BV(0) pacing (n = 4). In these 10 patients, LV pacing yielded a 7.4 +/- 8.0% higher dP/dt(max) than BV(0) pacing (P < 0.05). CONCLUSIONS: Using sequential BV pacing, generally with LV preactivation, moderate improvements in LV systolic function can be achieved in selected patients. Baseline PR interval may aid in the selection of the optimum cardiac resynchronization therapy (CRT) mode, favoring LV pacing in patients with a PR interval < or =200 ms.     

Right Ventricular Septal Pacing: A Comparative Study of Outflow Tract and Mid Ventricular Sites

Background: Prolonged right ventricle (RV) apical pacing is associated with left ventricle (LV) dysfunction due to dysynchronous ventricular activation and contraction. Alternative RV pacing sites with a narrower QRS compared to RV pacing might reflect a more physiological and synchronous LV activation. The purpose of this study was to compare the QRS morphology, duration, and suitability of RV outflow tract (RVOT) septal and mid‐RV septal pacing. Methods: Seventeen consecutive patients with indication for dual‐chamber pacing were enrolled in the study. Two standard 58‐cm active fixation leads were passed to the RV and positioned in the RVOT septum and mid‐RV septum using a commercially available septal stylet (model 4140, St. Jude Medical, St. Paul, MN, USA). QRS duration, morphology, and pacing parameters were compared at the two sites. The RV lead with less‐satisfactory electrical parameters was withdrawn and deployed in the right atrium. Results: Successful positioning of the pacing leads at the RVOT septum and mid‐RV septum was achieved in 15 patients (88.2%). There were no significant differences in the mean stimulation threshold, R‐wave sensing, and lead impedance between the two sites. The QRS duration in the RVOT septum was 151 ± 14 ms and in the mid‐RV septum 145 ± 13 ms (P = 0.150). Conclusions: This prospective observational study shows that septal pacing can be reliably achieved both in the RVOT and mid‐RV with active fixation leads using a specifically shaped stylet. There are no preferences in regard to acute lead performance or paced QRS duration with either position. (PACE 2010; 33:1169–1173)     

T-wave alternans testing in pacemaker patients: comparison of pacing modes and long-term prognostic relevance

Background: T‐wave alternans (TWA) is a useful method for identifying patients who are at risk for sudden cardiac death. We aimed to determine the effects of different pacing modes on test results and long‐term prognostic relevance of TWA in patients following a dual‐chamber (DDD) pacemaker implantation. Methods: Sixty‐three patients (mean age 68 ± 13 years) with structural heart disease and recently implanted DDD pacemakers were enrolled. Left ventricular (LV) function was normal or moderately impaired (mean LV ejection fraction 61 ± 13%). All patients underwent sequential TWA testing using atrial and ventricular pacing. Results: During atrial pacing requiring physiologic conduction to the ventricles, 21% of TWA tests were positive, 43% negative, and 36% indeterminate. When using right ventricular (RV) pacing in the same patients, 19% of tests were positive, 40% negative, and 41% indeterminate. When positive and indeterminate tests were grouped as nonnegative, the concordance between atrial and ventricular pacing was 62% (κ= 0.22). After a mean follow‐up of 5.9 ± 1.9 years, 18 (29%) patients had died. Improved survival was predicted by a negative TWA test using atrial pacing (P = 0.028), but not with ventricular pacing (P = 0.722). Conclusions: In patients with dual‐chamber pacemakers, there is a low concordance of TWA test results between atrial pacing with intrinsic conduction to the ventricles and apical RV pacing via pacemaker electrode. However, TWA during atrial pacing clearly exerts long‐term prognostic relevance in a patient group with preserved LV function and structural heart disease. (PACE 2011; 34:1054–1062)     

Anodal capture in cardiac resynchronization therapy implications for device programming

INTRODUCTION: Right ventricular (RV) anodal capture (AC) has been reported in cardiac resynchronization therapy (CRT), when left ventricular (LV) pacing uses pseudobipolar (LV tip to RV proximal electrode) configuration. The aim of the study was to analyze the prevalence of AC and its implications for device programming. METHODS AND RESULTS: When AC occurred, the resulting QRS morphology was evaluated with the following pacing modes: (1) LV tip pacing plus RV AC, (2) Biventricular (BiV) pacing (i.e., both LV and RV tip pacing), and (3) BiV pacing plus RV AC. Several interventricular pacing (VV) intervals from 50 ms of LV preactivation to 30 ms of RV preactivation were tested in modes 2 and 3. From 38 consecutive patients, AC was achieved in 14 (in 74% of the pacemakers and in none of the defibrillators). LV tip pacing plus RV AC obtained narrower QRS than BiV pacing at all VV intervals in seven of the patients with AC (50%). When BiV pacing is combined with RV AC, it produced a ventricular depolarization through two wave fronts (one from the LV tip and the second from either the ring or the tip of the RV lead depending on the VV interval programmed). CONCLUSIONS: AC obtained the narrowest QRS of all tested pacing modes in a significant proportion of patients undergoing CRT. Though the stimulus was delivered from three sites (BiV pacing plus RV AC mode), only two wave fronts of ventricular activation were seen by ECG.     

Influence of Different Atrioventricular and Interventricular Delays on Cardiac Output During Cardiac Resynchronization Therapy

Restoration of the atrioventricular (AVD) and interventricular (VVD) delays increases the hemodynamic benefit conferred by biventricular (BiV) stimulation. This study compared the effects of different AVD and VVD on cardiac output (CO) during three stimulation modes: BiV-LV = left ventricle (LV) preceding right ventricle (RV) by 4 ms; BiV-RV = RV preceding LV by 4 ms; LVP = single-site LV pacing. We studied 19 patients with chronic heart failure due to ischemic or idiopathic dilated cardiomyopathy, QRS ≥ 150 ms, mean LV end-diastolic diameter = 78 ± 7 mm, and mean LV ejection fraction = 21 ± 3%. CO was estimated by Doppler echocardiographic velocity time integral formula with sample volume placed in the LV outflow tract. Sets of sensed-AVDs (S-AVD) 90–160 ms, paced-AVDs (P-AVD) 120–160 ms, and VVDs 4–20 ms were used. BiV-RV resulted in lower CO than BiV-LV. S-AVD 120 ms and P-AVD 140 ms caused the most significant increase in CO for all three pacing modes. LVP produced a similar increase in CO as BiV stimulation; however, AV sequential pacing was associated with a nonsignificantly higher CO during LVP than with BiV stimulation. CO during BiV stimulation was the highest when LV preceded RV, and VVD ranged between 4 and 12 ms. The most negative effect on CO was observed when RV preceded LV by 4 ms. Hemodynamic improvement during BiV stimulation was dependent both on optimized AVD and VVD. LV preceding RV by 4–12 ms was the most optimal. Advancement of the RV was not beneficial in the majority of patients.     

Cardiac resynchronization therapy and obstructive sleep-related breathing disorder in patients with congestive heart failure

Objectives: To assess the impact of cardiac resynchronization therapy (CRT) with or without atrial overdrive pacing, on sleep‐related breathing disorder (SRBD). Introduction: CRT may have a positive influence on SRBD in patients who qualify for the therapy. Data are inconclusive in patients with obstructive SRBD. Methods: Consenting patients eligible for CRT underwent a baseline polysomnography (PSG) 2 weeks after implantation during which pacing was withheld. Patients with an apnea hypopnea index (AHI) ≥15 but <50 were enrolled and randomized to atrial overdrive pacing (DDD) versus atrial synchronous pacing (VDD) with biventricular pacing in both arms. Patients underwent two further PSGs 12 weeks apart. Results: Nineteen men with New York Heart Association class III congestive heart failure participated in the study (age 67.2 ± 7.5, Caucasian 78.9%, ischemic 73.7%). The score on Epworth Sleepiness Score was 7.3 ± 4.0, Pittsburgh Sleep Quality Index 7.4 ± 3.1, and Minnesota Living with Heart Failure Questionnaire 36.9 ± 21.9. There were no differences between the groups. At baseline, patients exhibited poor sleep efficiency (65.3 ± 16.6%) with nadir oxygen saturation of 83.5 ± 5.3% and moderate to severe SRBD (AHI 21.5 ± 15.3) that was mainly obstructive (central apnea index 3.3 ± 6.7/hour). On both follow‐up assessments, there was no improvement in indices of SRBD (sleep efficiency [68.3 ± 17.9%], nadir oxygen saturation of 82.8 ± 4.6%, and AHI 24.9 ± 21.9). Conclusion: In a cohort of elderly male CHF patients receiving CRT, CRT had no impact on obstructive SRBD burden with or without atrial overdrive pacing. (PACE 2011; 34:593–603)     

Continuously adjusting CRT therapy: clinical impact of adaptive cardiac resynchronization therapy

Cardiac resynchronization therapy (CRT) is a well-established therapy to reduce morbidity and mortality in patients with moderate and severe symptomatic congestive heart failure. Left ventricular (LV) pacing that fuses with intrinsic right ventricular (RV) conduction results in similar or even better cardiac performance compared to biventricular (Biv) pacing. Optimal programming of the atrio-ventricular (AV) and inter-ventricular (VV) delays is crucial to improve LV performance since suboptimal programming of AV and VV delays affect LV filling as well as cardiac output. CRT optimization using echocardiogram is resource-dependent and time consuming. Adaptive CRT (aCRT) algorithm provides a dynamic, automatic, ambulatory adjustment of CRT pacing configuration (Biv or LV pacing) and optimization of AV and VV delays. aCRT algorithm is safe and efficacious for CRT-indicated patients without permanent atrial fibrillation. It has been shown to improve CRT response and reduce morbidity and mortality for patients with normal AV conduction.