Intrinsic Atrioventricular Research Articles

Intrinsic Sinus Node/Atrioventricular Node Dysfunction Requiring Pacemaker Implantation: Role of Former Professional Sport Activity.

Sinus bradycardia and first degree or second degree Mobitz type I atrioventricular (AV) block in an athlete are considered adaptive and reversible phenomena; however, some evidence suggests that they may persist after detraining and become pathological. The aim of the study was to investigate the characteristics of a group of former professional athletes who required pacemaker (PM) implantation for intrinsic (idiopathic) sinus node (SN) dysfunction or AV block in comparison to control groups of sedentary individuals. We included all patients who underwent PM implantation during 2022. Three groups were compared: group 1 including 18 former professional athletes who received a PM for SN dysfunction/AV block in the absence of heart disease; group 2 including the first 20 sedentary individuals without heart disease who underwent PM implantation; and group 3 including all other 323 patients who received PM, the majority with underlying heart diseases. Compared to the non-athlete control group 2, the mean age at diagnosis and at the time of PM implantation of former professional athletes did not show statistically significant differences. However, subgroup analysis revealed significant differences depending on the type of sports discipline: the age at diagnosis and at PM implantation was significantly lower in former endurance athletes than former strength/mixed athletes, control non-athletes, and all other patients. Moreover, former endurance professional athletes exhibited a higher prevalence of second or third degree AV block (78%) as the reason for PM implantation compared to power/mixed athletes (44%). The other clinical characteristics, including echocardiographic parameters, did not differ between former athletes and non-athletes. Former professional endurance athletes with idiopathic SN dysfunction/AV block manifested the disease earlier in the life course compared to former power/mixed athletes and non-athletes. This suggests that bradycardia/AV block caused by intense and prolonged endurance sports may not always be benign and adaptive phenomena.

Role of RA-LV pacing in patients with symptomatic left bundle branch block with CRT - a single centre experience

Abstract Funding Acknowledgements Type of funding sources: None. Introduction Cardiac Resynchronisation Therapy(CRT) is considered as the cornerstone of treatment for patients with heart failure and left ventricular conduction delay ( left bundle branch block) who remain symptomatic despite optimal medical therapy. However, it has been well documented that the responder and success rates of this therapy are highly variable. Contemporary response rates from clinical trials as well as real world data demonstrate non-response rates of between 30–50%. Suboptimal AV delay timing is the most prevalent modifiable factor on follow up for improving response rates. AV Fusion pacing describes the delivery of CRT pacing with a programming strategy to preserve intrinsic atrioventricular (AV) conduction and ventricular activation via the right bundle branch. This concept is utilised in the RA- LV pacing strategies, which have been described in literature. However, RA-LV only pacing raises certain practical , moral and ethical concerns as it has never been a part of contemporary guidelines nor a part of large randomised control trial. Purpose The purpose of this study was to study the clinical as well as hemodynamic effects of RA-LV pacing in patients with a conventional CRT device with a programmed subthreshold RV lead. Methods All patients with a convention CRT indication ( CRT-P as well as CRT-D), with acceptable intrinsic AV conduction, non pacing dependent and normal Right Ventricular function were enrolled into the study. A total of 60 consecutive patients between 2016-2021 were enlisted from after the implant and followed up in the Device clinic of the institution. The baseline as well as follow-up LV function, Battery life and QRS duration was recorded and analysed. Results Total of 60 patients were enlisted of which 30 were males and 30 females. There were 16 patients were with Ischemic Cardiomyopathy in this group. The average follow-up period was 3 year from implant. The mean baseline Left Ventricular Ejection Fraction was 29% while the mean follow-up Left Ventricular Ejection Fraction was 46.5%. The mean QRS duration at implant was 155msec and the mean follow-up QRS was 123 msec. The subset analysis of ischemic vs the nonischaemic cardiomyopathy groups revealed that both groups had a similar response rates to improvement of clinical as well as Echocardiographic parameters including LVEF. The mean follow up LVEF in the ischemic and nonischaemic groups were 44.5 & 46.5% respectively. This finding suggests that the advantage of AV fusion pacing is not significantly impacted with underlying aetiology of the Cardiomyopathy. Conclusion RA-LV with RV subthreshold CRT is a reasonable strategy for achieving traditional response rates of CRT in patients with a good intrinsic AV conduction. This modality overcomes a large number of procedural as well as ethical roadblocks in the use of fusion pacing for CRT therapy optimisation.

Marked first-degree AV block may lead to complete AV block development

Abstract Funding Acknowledgements Type of funding sources: None. Background First-degree atrioventricular (AV) block (PR interval >200 ms) is considered a benign condition with rare progression to a higher degree AV block. The site of block is determined with electrophysiological (EP) study and measurement of His-ventricular (HV) interval, with normal values below 55 ms. Prolonged HV interval > 70 ms is predictive of higher-grade AV block development. Marked first-degree AV block with a PR > 300 ms may lead to symptoms such as fatigue, poor exercise tolerance and palpitations. When symptoms are correlated to the conduction delay, permanent pacemaker (PPM) implantation to restore AV synchrony should be considered. In the Framingham heart study, patients with first-degree AV block had a threefold higher risk of PPM implantation. However, there is no data on the HV intervals and the rate of progression of conduction disorder in patients with marked first-degree AV block. Purpose To assess the predictive value of HV interval measurement in patients with marked first-degree AV block for progression to a higher-degree conduction disorder. Methods We prospectively evaluated consecutive patients with symptomatic marked first-degree AV block that underwent a PPM implantation. His electrograms were recorded during the implantation, and HV intervals were measured from the first deflection of the His signal to the earliest onset of ventricular activation on a 12-lead surface ECG. Patients were followed for 6 months with three out-patient visits, during which the PPM was temporarily inhibited to check for intrinsic AV conduction. Results Seventeen patients were evaluated between January 2020 and September 2022. Ten patients (59%) were male, and 7 (41%) were female, with an average age of 61 ± 19 years. All patients had markedly prolonged PR interval (383 ± 47 ms) and narrow QRS complex (100 ± 16 ms). Three patients (17%) had intermittent type 1 second-degree AV block, right bundle branch block was recorded in two (12%) and left anterior fascicular block in four (24%) patients. Except for one patient with a corrected atrial septal defect, there were no echocardiographic signs of structural heart disease with a left ventricular ejection fraction of 61 ± 5%. The HV intervals were on the upper limit of normal values at 54 ± 6ms and no patient had an HV interval above 70 ms. Two patients (12%) developed complete AV block during follow-up: one female, and one male, 28 and 83 years old, respectively, with a PR interval 392 and 363 ms, QRS 104 and 94 ms, and HV 57 and 48 ms. None of the two had any additional conduction blocks at the time of PPM implant. Conclusion In our cohort of patients with symptomatic first-degree AV block (PR>300 ms), two patients (12%) developed complete AV block despite normal HV intervals at the time of implant. Closer monitoring, beyond only EP measurements, of patients with markedly prolonged PR intervals is warranted for the potential progression of conduction disorder.

Abstract 10530: Incidence and Electrocardiographic Predictors of Atrioventricular Conduction Recovery After Permanent Pacemaker Implantation in Transcatheter Aortic Valve Replacement

Background: High grade atrioventricular (AV) block (HGAVB) after transcatheter aortic valve replacement (TAVR) requiring permanent pacemaker implantation (PPM) is a well-established complication, but recovery of intrinsic AV conduction is not well studied. We assessed the incidence and electrocardiography (ECG) predictors of AV conduction recovery after PPM implantation post-TAVR. Methods: In this multicenter, retrospective study, consecutive patients undergoing TAVR between January 2015 to February 2019 were identified. All patients requiring PPM for HGAVB within 30 days after TAVR were included. Follow up ECGs, PPM checks, and clinic notes were reviewed to determine AV conduction recovery, defined as no need for ventricular pacing. Results: There were 533 TAVR patients, 443 with balloon expandable valves (BEV) and 90 with self-expanding valves (SEV). 5.1% of patients (n=27) required PPM for HGAVB, including 4.5% (n=20) from BEV group and 7.8% (n=7) from SEV group. Right bundle branch block (RBBB) was the most common baseline ECG finding (n=19). Mean time to PPM implant was 3.3±4.5 days. 11 patients received leadless and 16 received conventional pacemakers. At 6 months, 65% (n=13) of BEV group and none of SEV group had AV conduction recovery. BEV patients without AV conduction recovery had significantly longer baseline PR intervals compared to those with recovery (248±85 msec vs 169±22 msec; 95% CI 12.5-147.2; p=0.024). There were no significant differences in baseline QRS duration or presence of RBBB between those with and without AV conduction recovery. Conclusion: AV conduction recovery is more frequent after PPM implantation in TAVR patients receiving BEV (65%) compared to SEV (0%). Normal baseline PR intervals at baseline is associated with higher rate of AV conduction recovery among BEV patients. Temporary pacing with leadless pacemakers may be an alternative to conventional pacemakers in BEV patients without baseline first degree AV block.

Diagnostic reliability of AV synchrony self-diagnostics in leadless VDD pacemakers

Abstract Funding Acknowledgements Type of funding sources: None. Introduction Leadless pacemakers (PMs) capable of atrio-ventricular (AV) synchronous pacing have been introduced recently. These devices provide mechanical atrial sensing by detection of the atrial contraction via an accelerometer. Atrial tracking may be disturbed by external influences such as body motions and higher heart rates in real life. To track the amount of AV synchronous pacing, the device statistic classifies all sensed and paced QRS complexes according to presumed AV synchrony. The reliability of this self-diagnostics to estimate the true degree of AV synchrony, however, is insufficiently studied. Purpose To investigate the informative value of the device statistics offered by leadless VDD PMs regarding true AV snychrony. Methods We prospectively included all patients who received a leadless VDD PM between 07/2020 and 05/2021 at our center in this observational study. During the regular outpatient follow-ups, device interrogation was performed, which included evaluation of the PM statistics. True AV synchrony (defined as a QRS complex preceded by a p-wave within 300ms) was analyzed repeatedly during follow-up using Holter ECGs. Results We analysed 34 Holter ECGs from 20 outpatients (816 hours of ECG in total). Patients had a median age of 80 years (interquartile range 76-86 years), 55% were females. For Holter ECG sequences that showed high degree or complete AV-Block (>80% ventricular pacing), the percentage of paced beats that were presumed to be AV synchronous by the device statistic (ratio "AM-VP"/total VP) correlated well with AV synchrony as assessed using Holter-ECGs (Kendall’s τ=0.312, p<0.001). AV synchrony in the Holter ECG was different in patients with <66.6% presumed AV synchrony than in patients with >66.6% presumed AV synchrony (p<0.001, figure). For Holter ECG sequences with mostly preserved intrinsic AV conduction (<20% ventricular pacing), the ratio "AM-VP"/total VP was not predictive for true AV synchrony (Kendall’s τ=0.07, p=n.s.). In this situation, however, "VS only" (Kendall’s τ=0.110, p=0.005) correlated with true AV synchrony (due to AV conduction mode switch) and "VP only" showed an inverse correlation with AV synchrony (Kendall’s τ=-0.215, p<0.001). Conclusion Leadless PMs provide device statistics that show a correlation with true AV synchrony. The clinical setting as well as the device programming (e.g. AV conduction mode switch) significantly influence the predictive value of the different parameters of the device’s statistics.

AV timing in pacemaker patients with first-degree AV block: which is preferable, intrinsic AV conduction or pacing?

Some patients with pacemakers present with first-degree atrioventricular (AV) block. To avoid right ventricular (RV) pacing, preserving intrinsic AV conduction as much as possible is recommended. However, there is no clear cutoff AV interval to determine whether intrinsic AV conduction should be preserved or RV pacing should be delivered. This study aimed to compare a pacing mode-preserving, intrinsic AV conduction with the DDD mode delivering RV pacing in terms of echocardiographic parameters in patients with first-degree AV block and to investigate whether RV pacing induces heart failure (HF). Stroke volume (SV) was measured to determine the optimal AV delay with the intrinsic AV conduction rhythm and the DDD pacing delivering RV pacing. Echocardiographic evaluation was performed for 6-month follow-up period. Seventeen patients were studied. At baseline, mean intrinsic PQ interval was 250 ± 40 ms. SV was greater with RV pacing with optimal AV delay of 160 ms than with intrinsic AV conduction rhythm in all patients. Therefore, pacemakers were set to the DDD to deliver RV pacing. During follow-up, seven patients developed HF. Mean baseline E/E′ ratio in patients who developed HF (HF group) during RV pacing was higher than in patients without HF (non = HF group; 17.9 ± 8 versus 11.5 ± 2, P = 0.018) Even within HF group patients without a high baseline E/E′ ratio, it increased with RV pacing (22.2 ± 6 versus 11.6 ± 2; P < 0.001). In patients with pacemaker and first-degree AV block, RV pacing with the optimal AV delay of 160 ms increased SV. However, the risk of HF may be increased with RV pacing if the E/Eʹ ratio is > 15 during intrinsic AV conduction or RV pacing. RV pacing should be avoided in patients with high E/Eʹ ratio under intrinsic AV conduction or RV pacing.

Unusual Presentation of Atrial Flutter With Slow Ventricular Response

Atrial flutter is usually associated with tachycardia with a ventricular rate of 150 beats per minute. Less commonly, it may be associated with a slow ventricular response (SVR). This is typically seen in patients taking atrioventricular (AV) nodal blocking agents such as beta-blockers. In the absence of these drugs, atrial flutter with SVR may suggest intrinsic AV nodal disease, electrolyte disturbances, or atrial disease. We present a case of atrial flutter with SVR in a patient who was not receiving AV nodal blocking agents.

Assessment of the SyncAV fusion pacing algorithm on exercise capacity in patients with cardiac resynchronisation therapy device

Abstract Funding Acknowledgements Type of funding sources: Foundation. Main funding source(s): British Heart Foundation (BHF) and Local Departmental Research Funding Background Fusion pacing as part of cardiac resynchronization therapy (CRT) requires correct timing of left ventricular pacing to right ventricular activation. The SyncAV algorithm, available in Quadra Allure and Assura CRT devices, is designed to allow optimal fusion pacing by dynamic reassessment of intrinsic atrio-ventricular (AV) conduction to adjust the paced/sensed AV delay. However, it is unclear whether AV optimisation continues to maintain resynchronisation during exercise, or whether potential loss of fusion pacing with changes in intrinsic AV conduction could lead to decreased exercise capacity. Cardio-pulmonary exercise testing (CPET) is the gold standard method for assessing exercise performance. Purpose To assess exercise capacity using the SyncAV algorithm for fusion pacing, compared with conventional biventricular pacing with fixed AV delays (AVD) for CRT. Methods Patients at least 6 months post-CRT implant were recruited in a prospective single-centre randomized single-blind crossover study. Patients performed 2 CPET tests at least 1 week apart, with randomization to either SyncAV with fusion pacing or conventional biventricular pacing with a fixed AVD of 120ms. All other programming was optimised to produce the narrowest QRS duration possible at rest in each case. Results Nine patients (5 male, age 70 ± 10 years, mean ± standard deviation) were recruited, with both ischaemic and non-ischaemic aetiology of heart failure. All had clinical or echocardiographic response to CRT. There was no difference in peak oxygen consumption (V̇O2max) between programming (1.47 ± 0.57 vs 1.50 ± 0.65 l/min for fixed AVD and SyncAV groups respectively, p = 0.59), or oxygen consumption at anaerobic threshold (VT1) (0.72 ± 0.20 vs 0.74 ± 0.25 l/min, p = 0.57). There was no difference in oxygen pulse (V̇O2/heart rate - a surrogate of stroke volume) at peak (12.3 ± 3.8 vs 13 ± 5.0 ml/beat , p = 0.28) or VT1 (8.4 ± 2.2 vs 8.7 ± 2.1 ml/beat, p = 0.67) and also no change in time to V̇O2max (1400 ± 491 vs 1367 ± 543 seconds, p = 0.38) or VT1 (518 ± 211 vs 534 ± 200 seconds, p = 0.75). Average heart rate at the median stage of exercise showed no difference between programming (96 ± 18 vs 93 ± 15 bpm respectively, p = 0.32). There was no difference in BORG Rating of Perceived Exertion (BORG-RPE) score at either peak exercise (median 19 [interquartile range (IQR) 2] vs 17 [IQR 2], p = 0.23) or at the median stage of exercise (median 13 [IQR 1] vs 13 [IQR 2], p = 0.30). Conclusion Fusion pacing using the SyncAV algorithm does not appear to improve exercise capacity compared to optimised conventional biventricular pacing with fixed AVD.

Clinically guided pacemaker choice and setting: pacemaker expert programming study.

The aim of this multicentre, observational, transversal study was to evaluate pacemaker (PM) choice and setting in a large number of patients, in order to understand their relationship with the patients' clinical characteristics. The study enrolled a total of 1858 patients (71 ± 14 years, 54% male), consecutively evaluated during scheduled PM follow-up visits in 7 Italian cardiac arrhythmia centres. To evaluate the appropriateness of PM choice in relation to the patients' clinical characteristics, we analysed their rhythm disorders at the time of device implantation and the characteristics of the devices implanted. To evaluate the appropriateness of device setting, current rhythm disorders and device setting at the time of enrolment were analysed. In the overall study population, 64.3% of the patients received a PM with all of the features required for their rhythm disorder [80.8% in persistent atrioventricular (AV) block, 76.5% in atrial fibrillation needing pacing, 71.0% in sinus node disease, 58.7% in non-persistent atrioventricular block (AVB), 52.7% in neuro-mediated syncope]. The most frequent cause of inappropriate PM choice was the lack of an algorithm to promote intrinsic AV conduction in non-persistent AVB patients (38.1%). In 76.2% of the patients with an appropriate PM (n = 1301), the PM was optimally set for their rhythm disorder. In the present 'real-world' registry, a large number of patients (35.7%) did not receive an optimal PM for their rhythm disorders. Moreover, one-fourth of appropriate PMs were not programmed according to the patients' clinical characteristics.

179-02: First-degree atrioventricular Block, Atrioventricular (Dys)synchrony and Dual-chamber pacing. A long PR interval or a wide QRS? That is the dilemma

Background: In modern DDD pacemakers, strategies to minimize artificial right ventricular activation seek to avoid the potential but well-studied deleterious effects of cardiac pacing. While these mechanisms maintain electrical atrioventricular (AV) sequence, if significant 1st. degree AV block (1st.AVB) coexists, paradoxically AV mechanical dyssynchrony could be promoted. Apparently, atrioventricular sequence differs from atrioventricular synchrony. The purpose of this study was to elucidate clinical and hemodynamic results of long AV delays - narrow intrinsic QRS against DDD pacing with optimized AV interval - paced wide QRS. Methods: Prospectively included 32 adult patients with DDD pacemakers implanted for sick sinus node disease (SSND) and 1st.AVB. Study protocol demanded septal right ventricular lead, demonstrated <5% of ventricular pacing overall since implantation, normal QRS duration, preserved left ventricular ejection fraction (LVEF), no prosthetic valves and no history of atrial fibrillation (AF). Using Doppler echocardiography diastolic and systolic performances were verified in AAI pacing 10 beats/min faster than sinus rhythm, intrinsic long AV delay and native QRS (Ap-Vs), against the hemodynamic results (VTi, LVEF and Mitral regurgitation obtained by iteratively shortening the programmed AV delay (DDD pacing - Ap-Vp) at same cardiac rate. By Mitral valve inflow analysis (E/A waves measurements) optimal diastolic function (AV synchrony) was verified. Best left ventricular contractility and function was assessed by means of higher aortic flow time velocity integral (VTi) and LVEF. Optimal AV delay was defined by maximal separation of E/A waves, higher VTi and best LVEF with less Mitral valve regurgitation. AV dyssinchrony was determined by fused E + A waves, or E + A duration <40% of cardiac cycle. This patients were kept to ventricular pacing at the optimal AV interval (optimized AV – OAV group) for further comparison. The non-optimized AV (NOAV) group was formed by those whose best cardiac function was found at the intrinsic PR interval-native QRS. This group was kept to minimal ventricular pacing at the baseline PR interval. Follow-up included clinical evaluation and cardiac structure and function assessment at 3 and 6 months for both groups of patients. Results: Our cohort so far (mean= 73,6 + /-11,8 years) confirmed the existence of 2 separate groups from the diastolic function point of view: those showing AV dyssynchrony requiring AV optimization (OAV group: 18/32) and those with no AV dyssynchrony (no need for AV optimization - NOAV group: 14/32); p= 0.003. No other statistical differences were found in age, gender, symptoms, NYHA functional class, medication use, and structural heart disease, baseline PR interval or LVEF between groups. AAI pacing rate for echo measurements was 65 + /-9bpm for the OAV group vs. 67,5 + /-6,7bpm of their counterparts (p= NS). Remarkably, the AV interval when exceeded 263ms in the OAV group was 72% sensitive and 73% specific to demonstrate AV dyssynchrony. Moreover, in the OAV group, under optimized AV delay and artificial ventricular pacing, after 6 months of follow-up, LVEF is noticed to significantly decline (p= 0.002) and detrimental changes of cardiac structure with significant increase in left ventricular systolic (p= 0.04) and diastolic (p= 0.02) dimensions are noticed. No other statistical differences at follow-up were found in clinical outcomes (incidence of new AF episodes, electronic arrhythmias, pacemaker syndrome-like symptoms, NYHA functional class or hospitalizations) between groups. Conclusion: Our results preliminarily suggest that 1st.AVB with non-physiologically prolonged AV conduction (when ≥263ms) is highly associated with disturbed AV synchrony. However, this AV dyssynchrony when corrected by echocardiographycally optimized AV delays and forced ventricular pacing is negatively affected by the detrimental consequences of continual right ventricular artificial activation. Alternative-pacing strategies such as biventricular-pacing in this scenario merit further investigation.

Electrocardiographic and chronobiological features of paroxysmal AV block recorded by ambulatory electrocardiography.

The goal of this study was to investigate the electrocardiographic and chronobio-logical features of paroxysmal atrioventricular (AV) block (PAVB) using data from ambulatory electrocardiography (AECG). The study population consisted of five men and six women aged from 47 to 82 years of age. Main presenting symptoms were pre-syncope in five patients (45.5%) and syncope in three patients (27.3%). Organic cardiovascular diseases were seen in eight patients (72.7%), and AV conduction disturbances were seen in six patients (54.5%), such as right bundle branch block, first to second degree AV block on standard 12-lead electrocardiography. Incidence of PAVB events were 1-329 (37.9 ± 98.0) episodes/patient/day, and the maximum pause during Holter recordings was 3.3-12.4 (6.39 ± 3.09) seconds. This maximum pause caused by intrinsic AV block was longer than that of vagally mediated AV block (8.4 ± 3.2 sec vs 4.7 ± 1.0 sec, p<0.05). In chronobiological analysis, episodes of PAVB exhibited a circadian rhythm characterized by a peak between 2:00 am and 4:00 am and a trough between 0:00 pm and 2:00 pm. AECG is a useful tool to detect the maximum pause occurring during sleep and provides critical data necessary to prevent the sudden cardiac death caused by PAVB.

Clinical outcomes with synchronized left ventricular pacing: Analysis of the adaptive CRT trial

Acute studies have suggested that left ventricular pacing (LVP) may have benefits over biventricular pacing (BVP). The adaptive cardiac resynchronization therapy (aCRT) algorithm provides LVP synchronized to produce fusion with the intrinsic activation when the intrinsic atrioventricular (AV) interval is normal. The randomized double-blind adaptive cardiac resynchronization therapy trial demonstrated noninferiority of the aCRT algorithm compared to echocardiography-optimized BVP (control). To examine whether synchronized LVP (sLVP) resulted in better clinical outcomes. First, stratification by percent sLVP (%sLVP) and multivariate Cox proportional hazards model was used to assess the relationship between %sLVP and clinical outcomes. Second, outcomes were compared between patients in the aCRT arm (n = 318) and control patients (n = 160) stratified by intrinsic AV interval at randomization. In the aCRT arm, %sLVP ≥50% (n = 142) was independently associated with a decreased risk of death or heart failure hospitalization (hazard ratio 0.49; 95% confidence interval 0.28-0.85; P = .012) compared with %sLVP <50% (n = 172). A greater proportion of patients with %sLVP ≥50% improved in Packer's clinical composite score at 6-month (82% vs. 68%; P = .002) and 12-month (80% vs. 62%; P = .0006) follow-ups compared to controls. In the subgroup with normal AV (n = 241), there was a lower risk of death or heart failure hospitalization (hazard ratio 0.52; 95% confidence interval 0.27-0.98; P = .044) with the aCRT algorithm. A greater proportion of patients in the aCRT arm improved in the clinical composite score at 6-month (81% vs. 69%; P = .041) and 12-month (77% vs. 66%; P = .076) follow-ups compared to controls. Higher %sLVP was independently associated with superior clinical outcomes. In patients with normal AV conduction, the aCRT algorithm provided mostly sLVP and demonstrated better clinical outcomes compared to echocardiography-optimized BVP.

Minimizing ventricular pacing by a novel atrioventricular (AV) delay hysteresis algorithm in patients with intact or compromised intrinsic AV conduction and different atrial and ventricular lead locations

Purpose. To investigate if an advanced AV search hysteresis (AVSH) algorithm, Ventricular Intrinsic Preference (VIP™), reduces the incidence of ventricular pacing (VP) in sinus node dysfunction (SND) with both intact and compromised AV conduction and with intermittent AV block regardless of the lead positions in the right atria and the ventricle.Methods. Patients were classified as having intact AV (AVi) conduction if the PR interval was ≤ 210 ms on ECG and 1:1 AV conduction during atrial pacing up to 120 bpm with PR interval ≤ 350 ms. Otherwise the AV conduction was classified as compromised (AVc). Both AVi and AVc patients were randomized to VIP ON or OFF. VIP performed an intrinsic AV conduction search every 30 s for three consecutive atrial cycles with the extension of the sensed and paced AV (SAV/PAV) delays from basic values of 150/200 ms to 300/350 ms. Extended AV intervals were allowed for three cycles when VP occurred before returning to basic AV delays. The primary end-point was %VP at 12 months.Results. Among 389 patients, 30.1% had intact and 69.9% had compromised AV conduction. The mean %VP at 12 months was 9.6% by VIP compared to 51.8% with standard AV settings in patients with AVi (P < 0.0001) and 28.0% versus 78.9% (P < 0.0001) with AVc. With VIP, excessive %VP among most used lead positions was not seen. Conversely, when VIP was off %VP was low only in patients who had leads in the RA septal–RV septal position (23.0%).Conclusions. VIP feature reduces VP both in patients with SND and with intermittent heart block regardless of the lead positions in the right atria and the ventricle.

Usefulness of Overlapping of the E and A Waves of the Transmitral Flow as a Predictor of Responders to Cardiac Resynchronization Therapy

Atrioventricular (AV) dyssynchrony as well as ventricular-ventricular dyssynchrony plays an important role in the selection of candidates for cardiac resynchronization therapy (CRT), but no method for assessing the AV dyssynchrony has been established. The aim of this study was to investigate whether the degree of overlap of the E and A waves can predict response to CRT. The study subjects were 48 consecutive patients maintaining sinus rhythm and intrinsic AV conduction who underwent de novo dual-chamber CRT device implantation. CRT responders were defined as those with reductions in left ventricular end-systolic volume >15% at 6 months after CRT device implantations. Twenty-three patients (48%) were CRT responders. In a multivariate analysis, the overlap ratio of the E and A waves was the only independent predictor of response to CRT (odds ratio 1.03, 95% confidence interval 1.01 to 1.06, p= 0.01). Using a cut-off value of 33%, patients with overlap ratios of the E and A waves ≥33% had a significantly higher rate of response to CRT than those with ratios <33% (73% vs 27%, p= 0.002). In conclusion, the overlap ratio of the E and A waves before CRT device implantation may predict CRT response. This simple method may be helpful in evaluating dyssynchrony in patients, particularly with severe reduced left ventricular wall motion, because this method does not require any wall motion analysis.

Programmed versus Effective VV Delay during CRT Optimization: When What You See Is Not What You Get

In cardiac resynchronization therapy (CRT) devices, the interventricular (VV) delay denotes the time interval between left (LV) and right ventricular (RV) pacing. This study aimed to determine the proportion of patients in whom the effective VV delay (VVeff , delay between LV and RV depolarization, being induced either by pacing or intrinsic conduction) is different from the programmed VV delay during a standard VV delay optimization procedure. Thirty-three patients with heart failure and left bundle branch block configuration without total atrioventricular (AV) block receiving CRT were prospectively included. VVeff was calculated from intrinsic AV intervals, programmed optimal AV delay, and programming system. Intrinsic AV intervals were measured on intracardiac electrograms. The optimal AV and VV delays were determined by highest increase in maximum rate of LV pressure rise (dP/dtmax ). VV delays of 20-80 ms LV and RV preactivation were tested. Calculated maximum possible VVeff was shorter than 80 ms LV preactivation in up to 46% of patients and shorter than 40 ms LV preactivation in up to 3% of the patients. These proportions were 6% and 0% during 80 and 40 ms RV preactivation, respectively. In CRT patients with left bundle branch block without total AV block, the effective VV delay is shorter than the programmed VV delay during a standard optimization procedure in approximately half of the patients and this phenomenon is encountered predominantly during LV preactivation by 40 ms or more. Calculation of the individual maximum VVeff in advance can shorten the VV delay optimization procedure.

Comparison of Cardiac Resynchronization Therapy Optimization Methods with Respect to Biventricular Pacing Percentage: Sub-Analysis of Adaptive CRT Trial

A greater percent of bi-ventricular (BiV) pacing in CRT is associated with superior survival and clinical outcomes. Pacing is inhibited when the device atrio-ventricular (AV) delay is longer than the intrinsic AV conduction interval. CardioSync is an automatic CRT optimization method, which determines the optimal AV delay based on the measurement of intrinsic AV and P-wave intervals. We aimed to compare CardioSync to echocardiographic (echo) optimization with respect to cardiac function and percent BiV pacing lost due to AV programming.

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ORAL PRESENTATION

Pacing to Reduce Refractory Angina in Patients with Severe Coronary Artery Disease: A Crossover Pilot Trial

Biventricular pacing (BiV) has been shown to reduce wall stress and workload in regions near the pacing sites. This trial investigated if BiV near the ischemic region would reduce chest pain in patients with refractory angina due to severe coronary artery disease (CAD). Eleven patients were implanted with BiV devices with leads positioned at or adjacent to their ischemic regions as detected by single-photon emission computed tomography (SPECT) and randomized to either pacing turned ON or OFF for 3 months, and then crossed over for 3 months. With pacing turned ON, a Dynamic atrioventricular (AV) delay was set for approximately 90% and 70% of the intrinsic AV delay at the resting heart rate and at the onset of symptoms, respectively. One patient was excluded from the analysis due to a large amount of RV pacing during the OFF periods (24-64%) and due to an inability to properly deliver therapy because of an excessive number of ventricular premature complexes. Overall, with the device ON vs. OFF, the number of angina episodes (0.8 ± 0.4 vs. 1.2 ± 0.7 per week, P = 0.03) and amount of nitroglycerin used (0.2 ± 0.1 vs. 1.0 ± 0.7 per week, P = 0.11) was lower with BiV pacing. Furthermore, the treadmill exercise time to symptoms trended higher (427 ± 65 vs. 408 ± 64 s, P = 0.19), and the sum of fluorodeoxyglucose-positron emission tomography (FDG-PET) scores trended lower (7.9 ± 3.5 vs. 12.0 ± 4.0, P = 0.11) with the device ON vs. OFF. Nevertheless, there were no significant differences in SPECT myocardial perfusion scores, left ventricle ejection fraction, wall motion score index, and quality of life scores with device programmed ON vs. OFF (all P > 0.05). In conclusion, this pilot study demonstrated that BiV-P at or near the ischemic region was feasible and associated with significant reductions in angina in patients with severe CAD. Adequately powered prospective studies are needed to confirm these findings.

Adjusting the timing of left-ventricular pacing using electrocardiogram and device electrograms

Left-ventricular (LV) pacing with optimized atrio-ventricular (AV) timing may provide similar or greater benefit in comparison with bi-ventricular (BiV) pacing in a subset of cardiac resynchronization therapy (CRT) patients with sinus rhythm and preserved AV conduction. We hypothesized that the optimal device AV delays during LV pacing can be predicted using electrocardiogram (ECG) and device electrograms. METHODS AND RESULTS PATIENTS: (n= 55) with sinus rhythm and PR interval < 300 ms had their CRT devices programmed to atrial and LV pacing with a range of AVs as well as to echocardiographically optimized BiV and no ventricular pacing. At each setting, LV function was evaluated using echocardiography and AVs corresponding to the highest LV ejection fraction (LVEF), lowest LV end-systolic volume (LVESV), and the average of the two (by EF and ESV) were determined. Correlation between the optimal AVs and the following intervals was investigated: intrinsic QRS duration (QRSs), intervals from atrial pacing (Ap) to right-ventricular (RV) sensing (Ap-RVs), from RV sensing to LV activation (RVs-LVs), and from LV pacing to RV sensing (LVp-RVs). Optimal AVs moderately correlated with intrinsic Ap-RVs interval, whereas other parameters showed weak or no correlation. The best correlation (R = 0.66, P< 0.0001) was between the optimal AV delay according to EF and ESV, and Ap-RVs interval. Programming of AVs during LV pacing to the shortest of 70% of the intrinsic Ap-RVs interval, or Ap-RVs--40 ms resulted in significant improvement in LV function similar to that in case of BiV. Optimal AV during LV pacing can be approximated from the intrinsic AV conduction time.

Syncope Due to Idiopathic Paroxysmal Atrioventricular Block: Long-Term Follow-Up of a Distinct Form of Atrioventricular Block

We present data on patients with syncope due to paroxysmal atrioventricular (AV) block unexplainable in terms of currently known mechanisms. Paroxysmal AV block is known to be due to intrinsic AV conduction disease or to heightened vagal tone. We evaluated 18 patients presenting with unexplained syncope who had: 1) normal baseline standard electrocardiogram (ECG); 2) absence of structural heart disease; and 3) documentation, by means of prolonged ECG monitoring at the time of syncopal relapse, of paroxysmal third-degree AV block with abrupt onset and absence of other rhythm disturbances before or during the block. The study group consisted of 9 men and 9 women, mean age 55 ± 19 years, who had recurrent unexplained syncope for 8 ± 7 years and were subsequently followed up for as long as 14 years (4 ± 4 years on average). The patients had no structural heart disease, standard ECG was normal, and electrophysiological study was negative. In all patients, prolonged ECG monitoring documented paroxysmal complete AV block with 1 or multiple consecutive pauses (mean longest pause: 9 ± 7 s at the time of syncope); AV block occurred without P-P cycle lengthening or PR interval prolongation. During the observation time, no patient had permanent AV block; on permanent cardiac pacing, no patient had further syncopal recurrences. Common clinical and electrophysiological features define a distinct form of syncope due to idiopathic paroxysmal AV block characterized by a long history of recurrent syncope, absence of progression to persistent forms of AV block, and efficacy of cardiac pacing therapy.