DDD Mode Research Articles

Energy loss by right ventricular pacing: Patients with versus without hypertrophic cardiomyopathy.

BackgroundRight ventricular (RV) pacing causes left ventricular (LV) dyssynchrony sometimes resulting in pacing‐induced cardiomyopathy. However, RV pacing for hypertrophic obstructive cardiomyopathy is one of the treatment options. LV flow energy loss (EL) using vector flow mapping (VFM) is a novel hemodynamic index for assessing cardiac function. Our study aimed to elucidate the impact of RV pacing on EL in normal LV function and hypertrophic cardiomyopathy (HCM) patients.MethodsA total of 36 patients with dual‐chamber pacemakers for sick sinus syndrome or implantable cardioverter defibrillators for fatal ventricular tachyarrhythmias were enrolled. All patients were divided into two groups: 16 patients with HCM (HCM group) and others (non‐HCM group). The absolute changes in EL under AAI (without RV pacing) and DDD (with RV pacing) modes were assessed using VFM on color Doppler echocardiography.ResultsIn the non‐HCM group, the mean systolic EL significantly increased from the AAI to DDD modes (14.0 ± 7.7 to 17.0 ± 8.6 mW/m, P = .003), whereas the mean diastolic EL did not change (19.0 ± 12.3 to 17.0 ± 14.8 mW/m, P = .231). In the HCM group, the mean systolic EL significantly decreased from the AAI to DDD modes (26.7 ± 14.2 to 21.6 ± 11.9 mW/m, P < .001), whereas the mean diastolic EL did not change (28.7 ± 16.4 to 23.9 ± 19.7 mW/m, P = .130).ConclusionsRV pacing increased the mean systolic EL in patients without HCM. Conversely, RV pacing decreased the mean systolic EL in patients with HCM.

Characteristics of Cardiac Memory in Patients with Implanted Cardioverter-defibrillators: The Cardiac Memory with Implantable Cardioverter-defibrillator (CAMI) Study.

This study sought to determine factors associated with cardiac memory (CM) in patients with implantable cardioverter-defibrillators (ICDs). Patients with structural heart disease [n = 20; mean age: 72.6 ± 11.6 years; 80% male; mean left ventricular ejection fraction (LVEF): 31.7 ± 7.6%; history of myocardial infarction in 75% and nonsustained ventricular tachycardia (NSVT) in 85%] and preserved atrioventricular conduction received dual-chamber ICDs for primary (80%) or secondary (20%) prevention. Standard 12-lead electrocardiograms were recorded in AAI and DDD modes before and after seven days of right ventricular (RV) pacing in DDD mode with a short atrioventricular delay. The direction (azimuth and elevation) and magnitude of spatial QRS, T, and spatial ventricular gradient vectors were measured before and after seven days of RV pacing. CM was quantified as the degree of alignment between QRSDDD-7 and TAAI-7 vectors (QRSDDD-7 –TAAI-7 angle). Circular statistics and mixed models with a random slope and intercept were adjusted for changes in cardiac activation, LVEF, known risk factors, and the use of medications known to affect CM occurring on days 1 through 7. The QRSDDD-7–TAAI-7 angle strongly correlated (circular r = −0.972; p < 0.0001) with a TAAI-7–TDDD-7 angle. In the mixed models, CM-T azimuth changes [+132° (95% confidence interval (CI): 80°–184°); p < 0.0001] were counteracted by the history of MI [−180° (95% CI: −320° to −40°); p = 0.011] and female sex [−162° (95% CI: −268° to −55°); p = 0.003]. A CM-T area increase [+15 (95% CI: 6–24) mV*ms; p < 0.0001] was amplified by NSVT history [+27 (95% CI: 4–46) mV*ms; p = 0.007]. These findings suggest that preexistent electrical remodeling affects CM in response to RV pacing, that CM exhibits saturation behavior, and that women reach CM saturation more easily than men.

P1495Energy loss by right ventricular pacing: normal left ventricular function vs. hypertrophic cardiomyopathy

Abstract Background Right ventricular (RV) pacing causes left ventricular (LV) dysfunction. On the other hand, RV pacing for hypertrophic obstructive cardiomyopathy (HOCM) is an established treatment. LV flow energy loss (EL) is a new hemodynamic index for assessing cardiac function. However, the impact of RV pacing on EL remains unknown. Objective The objective of this study was to investigate the EL by RV pacing on normal LV function and hypertrophic cardiomyopathy (HCM). Methods A total of 28 patients underwent echocardiography for EL assessment under AAI (without RV pacing) and DDD (with all RV pacing) mode. Among them, 16 were sick sinus syndrome (SSS) patients with normal LV function, and 12 were HCM patients. EL was calculated from color Doppler images using a vector flow mapping. Results There were no significant difference in patients' background parameters between the SSS and the HCM groups. In the SSS group, mean systolic EL was significantly increased from AAI to DDD mode (14.9 to 19.2 mW/m, P&lt;0.01, Panel A), whereas diastolic EL was not changed from AAI to DDD mode (22.3 to 18.8 mW/m, P=0.12). In the HCM group, systolic mean EL was significantly decreased from AAI to DDD mode (29.9 to 22.5 mW/m, P&lt;0.01, Panel B) irrespectively of with or without LV outflow obstruction, whereas diastolic mean EL was not changed from AAI to DDD mode (28.6 to 24.3 mW/m, P=0.47). Change of flow energy loss Conclusion RV pacing increased mean systolic EL in normal LV function, but decreased in HCM with or without LV outflow obstruction. In the patients with HCM, the impact of RV pacing on EL is different compared with normal LV function.

Assessment of Left Ventricular Dyssynchrony and Cardiac Function in Patients with Different Pacing Modes Using Real-Time Three-Dimensional Echocardiography: Comparison with Tissue Doppler Imaging

Background: Previous studies revealed that right ventricle apex pacing with different modes may yield abnormal electrical activity and left ventricle dyssynchrony.Aim of the work: To evaluate systolic function of left ventricle and mechanical dyssynchrony with different modes of pacing using real time three dimensional echocardiography [the RT3DE] and tissue Doppler imaging [TDI].Patients and Methods: The study included thirty-five individuals with permanent dual chamber pacemaker with atrial leads placed in right atrial appendage and right ventricular leads placed in right ventricular apex, the pacemakers were programmed to different modes. Imaging parameters were obtained following pacing for 24 hours in each mode.Results: The results revealed that the RT3DE and TDI-derived dyssynchrony indices in the atrial demand pacing [AAI] mode were significantly lower than those in the dual chamber demand pacing [DDD] and ventricular demand pacing [VVI] modes; however, there was no significant difference between the DDD and VVI modes. Also, left ventricular ejection fraction [LVEF] during AAI and DDD modes was significantly higher than that during VVI mode; however, there was no significant difference between the DDD and AAI modes. There were negative correlations between LVEF and Ts-MD and Ts-SD, and there was positive strong correlation between RT3DE and TDI-derived dyssynchrony indices.Conclusions: Left ventricular systolic synchronicity in AAI mode was superior to that in DDD and VVI modes. Left ventricular ejection fraction in the AAI and DDD pacing modes are superior to that in the VVI mode.

Sudden onset pacemaker-induced diaphragmatic twitching during general anesthesia

BackgroundInvoluntary muscle contraction caused by extracardiac stimulation is a rare complication induced by a pacemaker. We report a case who developed sudden onset diaphragmatic contractions during general anesthesia caused by a DDD mode pacemaker.Case presentationA 74-year-old woman with a permanent pacemaker was scheduled to undergo mastectomy. The pacing mode was switched from DDD to VOO intraoperatively to avoid electromagnetic interference. Immediately after returning the pacing mode to DDD after surgery, diaphragmatic contractions occurred, mimicking bucking type of movements. After switching the pacing to A-sense V-pace, the twitching ceased. Because no structural problems were noted, and the twitching disappeared after terminating atrial pacing, diaphragmatic contractions might be caused by stimulation of the right phrenic nerve located near the right appendage where the electrode was installed.ConclusionThe potential risk of muscle twitching should be carefully evaluated preoperatively especially in patients with atypical position of pacemaker leads.

Assessment of QT interval in ventricular paced rhythm: Derivation of a novel formula

ObjectiveThe objective of the study was to determine the optimal formula to estimate QT interval adjusting for QRS prolongation during right ventricular (RV) pacing. MethodsThis observational study included individuals (n = 43) with a newly implanted permanent ventricular pacemaker, who had a narrow QRS complex before pacemaker insertion. QT interval with RV pacing was related to QT interval before pacemaker implantation. The validation cohort (n = 442) had permanent RV pacing in DDD mode. ResultsA new QTc formula was derived utilizing the constants from the relationship between the spline heart rate QT correction (QTcRBK) before and after pacing; specifically, QTcRBKPACED = QTcRBK × 0.86. The JT interval from paced complexes was highly heart rate (HR) dependent and was not accurate for QT assessment. Previous, QTc formula for paced complexes were not highly correlated with QT before pacing unless a robust HR correction is added. Formulae subtracting a fixed amount from QTcPACED markedly overestimated QTc before pacing. ConclusionWe proposed a new, simple formula for QT estimation in RV pacing. JT interval in paced complexes is highly HR dependent and is not accurate for QT assessment. The new spline approach for HR correction for the QT, once incorporated into some previously proposed formulae, blunts HR dependency and improves prediction of QT before pacing. QTcRBKPACED*0.86 and QTcRBKPACED – (QRS*0.5) demonstrated the best balance of relatively strong correlation to QTc before pacing and accurate QTc prolongation identification. Abnormal QT for QTcRBKPACED*0.86 as defined by the 97.5th and 99th percentile are 469 and 479 ms respectively.

Cardiac Electrical Modeling for Closed-Loop Validation of Implantable Devices.

Evaluating and testing cardiac electrical devices in a closed-physiologic-loop can help design safety, but this is rarely practical or comprehensive. Furthermore, in silico closed-loop testing with biophysical computer models cannot meet the requirements of time-critical cardiac device systems, while simplified models meeting time-critical requirements may not have the necessary dynamic features. We propose a new high-level (abstracted) physiologically-based computational heart model that is time-critical and dynamic. The model comprises cardiac regional cellular-electrophysiology types connected by a path model along a conduction network. The regional electrophysiology and paths are modeled with hybrid automata that capture non-linear dynamics, such as action potential and conduction velocity restitution and overdrive suppression. The hierarchy of pacemaker functions is incorporated to generate sinus rhythms, while abnormal automaticity can be introduced to form a variety of arrhythmias such as escape ectopic rhythms. Model parameters are calibrated using experimental data and prior model simulations. Regional electrophysiology and paths in the model match human action potentials, dynamic behavior, and cardiac activation sequences. Connected in closed loop with a pacing device in DDD mode, the model generates complex arrhythmia such as atrioventricular nodal reentry tachycardia. Such device-induced outcomes have been observed clinically and we can establish the key physiological features of the heart model that influence the device operation. These findings demonstrate how an abstract heart model can be used for device validation and to design personalized treatment.

Impact of DDD and VVIR Stimulation Modes on Functional Capacity and Quality of Life of Chagasic Patients

Introduction: Atrioventricular stimulation provides hemodynamic benefits over the isolated ventricular rate, but this advantage is not completely established in chagasic patients with systolic dysfunction. Objectives: To evaluate the influence of DDD and VVIR stimulation modes on functional capacity, quality of life (QoL) and laboratory abnormalities of a natriuretic peptide in chagasic patients with ventricular dysfunction submitted to pacemaker implantation. Methods: Twenty patients (55% male) with a mean age of 62.7 (± 9.9 years) and a mean ejection fraction of 41.8% (± 2.8) were prospectively studied. Alternately, patients received pacing in the DDD and VVIR modes for a period of three months under each schedule. The minimum percentage of ventricular pacing was 80%. After each period, the patient was submitted to the six-minute walk test (6MWT), QOL assessment by the Minnesota Living with Heart Failure Questionnaire (MLHFQ) and the Assay of QUAlity of life and RELated events (AQUAREL). Laboratory evaluation was performed with the N-terminal fraction of the brain natriuretic peptide (N-terminal pro b-type natriuretic peptide - NT-proBNP). Results: The mean distance walked on the 6MWT in the DDD and VVIR modes were 390.60 (± 52.71) and 396.30 (± 52.71) meters respectively (p = 0.160). Results of lower QOL were found, considering the physical domain of the MLHFQ (p = 0.03) and the domains of effort dyspnea (p = 0.05) and arrhythmia (p &lt;0.001) of the AQUAREL with the VVIR mode. NT-proBNP levels increased significantly with stimulation in VVIR mode (p &lt; 0.001). Conclusion: After three months of stimulation with the VVIR mode, there was worsening of the QoL of the chagasic patients and increase of the levels of NT-proBNP (clinical trial record: ReBEc RBR-53x476).

Impacto dos Modos de Estimulação DDD e VVIR na Capacidade Funcional e Qualidade de Vida de Pacientes Chagásicos

Introdução: A estimulação atrioventricular propicia benefícios hemodinâmicos em relação à ventricular isolada, mas essa vantagem não está completamente estabelecida em pacientes chagásicos com disfunção sistólica. Objetivo:Avaliar a infl uência dos modos de estimulação DDD e VVIR na capacidade funcional, qualidade de vida (QV) e alterações laboratoriais de peptídeo natriurético em pacientes chagásicos com disfunção ventricular submetidos a implante de marcapasso. Métodos: Estudaram-se prospectivamente 20 pacientes (55% do sexo masculino) com média de idade de 62,7(± 9,9 anos) e média da fração de ejeção de 41,8% (± 2,8). Alternadamente, os pacientes receberam a estimulação nos modos DDD e VVIR por um período de três meses sob cada programação. O mínimo percentual de estimulação ventricular admitido foi de 80%. Após cada período, o paciente foi submetido ao teste de caminhada de seis minutos (TC6M), avaliação de QV pelo Minnesota Living with Heart Failure Questionnaire (MLHFQ) e pelo Assesment of QUAlity of life and RELated events (AQUAREL). A avaliação laboratorial foi realizada com a dosagem da fração N-terminal do peptídeo natriurético cerebral (N-terminal pro b-type natriuretic peptide – NT-proBNP). Resultados: A média da distância percorrida no TC6M nos modos DDD e VVIR foram respectivamente 390,60 (± 52,71) e 396,30 (± 52,71) metros (p = 0,160). Verifi caram-se resultados de QV inferiores, considerando o domínio físico do MLHFQ (p = 0,03) e os domínios dispneia de esforço(p = 0,05) e arritmia (p &lt; 0,001) do AQUAREL, com o modo VVIR. Os níveis de NT-proBNP aumentaram signifi cativamente com a estimulação no modoVVIR (p &lt; 0,001). Conclusão: Após três meses de estimulação com omodo VVIR, houve piora da QV dos pacientes chagásicos e aumento dos níveis de NT-proBNP (registro de ensaio clínico: ReBEc RBR-53x476)

Heart rhythm model for the simulation of electric fields in transesophageal atrial pacing and cardiac resynchronization therapy

Abstract Electric field of biventricular (BV) pacing, left ventricular (LV) electrode position and electrical interventricular desynchronization are important parameters for successful cardiac resynchronization therapy (CRT) in patients with heart failure, sinus rhythm and reduced LV ejection fraction. The aim of the study was to evaluate electric pacing field of transesophageal left atrial (LA) pacing and BV pacing with 3D heart rhythm simulation. Bipolar right atrial (RA), right ventricular (RV), LV electrodes and multipolar hemispherical esophageal LA electrodes were modeled with CST (Computer Simulation Technology, Darmstadt). Electric pacing field were simulated with bipolar RA and RV pacing with Solid S (Biotronik) electrode, bipolar LV pacing with Attain 4194 (Medtronic) electrode and bipolar LA pacing with TO8 (Osypka) esophageal electrode. 3D heart rhythm model with esophagus allowed electric pacing field simulation of 4-chamber pacing with bipolar intracardiac RA, RV, LV pacing and bipolar transesophageal LA pacing. The pacing amplitudes were 3V RA pacing amplitude, 50V LA pacing amplitude, 1.5V RV pacing amplitude and 3V LV pacing amplitude with 0.5ms pacing pulse duration. The atrioventricular delay between RA pacing and BV pacing was 140ms atrioventricular pacing delay and simultaneous RV and LV pacing. Electric pacing fields were simulated during the different pacing modes AAI, VVI, DDD and DDD0V. The intracardiac far-field pacing potentials were evaluated with intracardiac electrodes and a distance of 1mm from the electrodes with RA electrode 1.104V, RV electrode 0.703V and LV electrode 1.32V. The transesophageal far-field pacing potential was evaluated with transesophageal electrode and a distance of 10mm from the elelctrode with LA electrode 6.076V. Heart rhythm model simulation with esophagus allows evaluation of electric pacing fields in AAI, VVI, DDD, DDD0V and DDD0D pacing modes. Electric pacing field of RA, RV and LV pacing in combination with LA pacing may additional useful pacing mode in CRT non-responders.

A Case of a Cardiac Resynchronization Therapy-Defibrillator Exhibiting a Lower and Alternately Variable Basic Rate

A cardiac resynchronization therapy defibrillator (CRT-D) (Medtronic Inc. Protecta XT) was implanted in a 67-year-old man who had cardiac sarcoidosis with extremely low cardiac function. He had ventricular tachycardia which was controlled by catheter ablation, medication and pacing. The programmed mode was DDI, lower rate was 90 beats/minute, paced AV delay was 150 ms, and the noncompetitive atrial pacing (NCAP) function was programmed as 300 ms.After his admission for pneumonia and heart failure, we changed his DDI mode to a DDD mode because he had atrial tachycardia, which led to inadequate bi-ventricular pacing. After a while, there were cycle lengths which were longer than his device setting and alternately varied. We were able to avoid this phenomenon with AV delay of 120 ms and NCAP of 200 ms.NCAP is an algorithm which creates a gap above a certain period after the detection of an atrial signal during the postventricular atrial refractory period of the pacemaker. This is to prevent atrial tachycardia and repetitive non-reentrant ventriculoatrial (VA) synchrony in the presence of retrograde VA conduction. But in this case, NCAP algorithm induced much lower rate than the programmed basic lower rate. This situation produced some arrhythmias and exacerbated symptoms of heart failure. This had to be paid attention to, especially when the device was programmed at high basic heart rate.

Impact of pacemaker mode in patients with atrioventricular conduction disturbance after trans-catheter aortic valve implantation.

This study aimed to assess the impact of pacemaker mode programming on clinical outcomes in patients with high-degree atrioventricular conduction disturbance (AVCD) after transcatheter aortic valve implantation (TAVI). Although high-degree AVCD after TAVI can receive pacemaker, recovery of the AVCD is often observed. Specific pacemaker algorithms (AAI-DDD mode switch) are available which favor spontaneous atrioventricular conduction. Of 1,621 consecutive multi-center TAVI patients, 269 (16.4%) received pacemaker. We retrospectively included 91 patients with persistent high-degree AVCD at hospital discharge. Pacemaker dependency was defined as absence, inadequate intrinsic ventricular rhythm, or ventricular pacing time > 95% on pacemaker interrogation during follow-up. Comparison of heart failure hospitalization and death between conventional DDD (cDDD) and other modes was examined (AAI-DDD and VVI). During a mean follow-up duration of 13 months, the pacemaker dependency rate was 52.8%. Patients with cDDD mode (N = 36: 40.0%) had significantly more pacemaker dependency. Multivariate analysis showed that cDDD mode was independently associated with pacemaker dependency (odds ratio = 3.63, P = 0.03). Moreover, cDDD patients had a significant higher incidence of heart failure hospitalization (Hospitalization: cDDD vs. others = 45.4% vs. 18.2%, P = 0.03) and had a higher incidence of mortality (Death: cDDD vs. the others = 27.0% vs. 4.4%, P = 0.06). Up to half of patients implanted for high-degree AVCD after TAVI had conduction recovery. Patients with cDDD programming at hospital discharge had more pacemaker dependency and a worse cardiac prognosis. Thus, pacemaker mode should be systematically set to promote spontaneous atrioventricular conduction in patients with pacemaker implantation after TAVI.

Prognostic Factors in Patients with an Implanted Pacemaker after 80 Years of Age in a 4-Year Follow-Up

Background: The controversy over electrotherapy for patients aged >80 years occurs already at the stage of qualification for this treatment type and concerns optimal device selection, the implantation strategy, and the overall benefit from pacemaker therapy. The group also has a considerable number of cardiovascular risk factors, and the data from the literature on the impact of the pacing mode on the remote prognosis of this group are ambiguous. Objective: Assessment of the risk factors for death among patients with implanted pacemakers >80 years of age in a 4-year follow-up. Methods: The study group consisted of 140 consecutive patients (79 women) aged 84.48 ± 3.65 years with single- or dual-chamber pacemakers implanted >80 years of age because of symptomatic bradycardia. In univariate and multivariate Cox regression analyses, demographic, echocardiographic, and laboratory parameters, pharmacotherapy, and factors related to the implanted device - i.e., indications, pacemaker type, and the implantation position of the tip of the right ventricular lead - were included. The endpoint was death for any reason in a 4-year follow-up. Results: During follow-up, 68 patients (48.6%) died. Although atrial fibrillation with a slow ventricular response constituted 20% of the indications for implantation, 60.8% of the patients received a single-chamber system (VVI/VVIR). In the whole group, the multivariate Cox regression analysis showed both a favourable prognostic significance of DDD pacing system implantation (HR = 0.507; 95% CI: 0.294-0.876) and coexisting hypertension (HR = 0.520; 95% CI: 0.299-0.902). The risk factors were fasting glycaemia (HR = 1.180; 95% CI: 1.038-1.342) and, potentially, female sex (HR = 1.672; 95% CI: 0.988-2.830; p = 0.056). In the female subgroup a more favourable prognosis was related to the use of angiotensin-converting enzyme inhibitors (HR = 0.435; 95% CI: 0.202-0.933) and DDD pacemaker implantation (HR = 0.381; 95% CI: 0.180-0.806). In the male subgroup a more favourable prognosis was related to concerned patients with coexisting hypertension (HR = 0.349; 95% CI: 0.079-0.689). Conclusions: DDD mode pacing seems to serve as a factor which decreases mortality among patients aged >80 years in long-term follow-up. The potentially poorer prognosis for the female patients in this group may result from a combination of the dominant VVI pacing mode, potential propagation of atrial fibrillation, a low proportion of antithrombotic therapy, and sex-related predispositions to thromboembolic complications.

Bigeminy and a Pacemaker.

An 81-year-old woman with a medical history of coronary artery disease, paroxysmal atrial fibrillation, and sick sinus syndrome, and implantation in 2013 of an Altrua™ dual-chamber pacemaker (Boston Scientific Corporation; Natick, Mass), presented after device interrogation revealed elevated impedance of >2,500 Ω in her atrial lead. The device settings were DDD mode, a lower rate limit of 60 beats/min, and a maximum atrioventricular (AV) delay of 330 ms. She reported fatigue, dyspnea on exertion, and occasional palpitations. She was admitted for new atrial lead implantation, and an electrocardiogram was obtained (Fig. 1).The electrocardiogram shows which of the following?Figure 1 shows ventricular depolarizations in a bigeminal pattern in lead V1, all of which are preceded by a pacing stimulus, which excludes selection A. In addition, the first beat (odd numbers) in each pair is followed by an atrial depolarization (Fig. 2, arrows), which appears to be retrograde atrial activation from the ventricular-paced beat.This observation is supported by the predominantly negative deflection of the P waves and the proximity to the preceding T wave. Therefore, underlying sinus rhythm is not seen, so selection C is excluded. These atrial depolarizations appear to have been sensed by the pacing device, because a ventricular-paced beat is seen after each atrial beat at a consistent delay of 300 ms, and the programmed AV delay was 330 ms, correlating with this finding. Selection B is therefore excluded.The pattern of the tracing is of particular note, given the grouped beats of ventricular pacing in a bigeminal pattern. Absence of an atrial depolarization is noted after the second ventricular-paced beat in each pair (even numbers). Therefore, second-degree 2:1 retrograde AV block is present. Had retrograde conduction of ventricular-paced beats continued, a pattern of pacemaker-induced tachycardia might have been seen. “Endless-loop” tachycardia is a known sequela of DDD pacing in dual-chamber pacemakers.1–3 Its characteristics are usually a function of the set AV delay and ventriculoatrial (VA) blanking periods.3 Our patient's programmed atrial blanking period after ventricular pacing was 120 ms with an observed VA conduction of 320 ms, well outside this period. However, pacemaker-induced tachycardia is not present, evidenced by the absence of atrial depolarization after each second ventricular-paced beat.In cardiac electrophysiologic studies of healthy patients, VA conduction in ventricular pacing has had an average refractory cycle length of 432 ms (range, 360–600 ms). Most patients (66%) had block within the AV node, whereas the remaining patients had block within the His-Purkinje system.4 Our patient was elderly and had sick sinus syndrome, making underlying AV nodal disease highly likely. A longer refractory period of the AV node could explain the intermittent absence of retrograde P waves with ventricular pacing.Ultimately, our patient underwent uncomplicated implantation of a new right atrial lead, with normal device function thereafter.

Successful treatment of ventricular fibrillation storm triggered by short-long-short sequence; time to avoid managed ventricular pacing

Sudden cardiac death (SCD) in hypertrophic cardiomyopathy (HCM) is caused by ventricular tachyarrhythmia that can be effectively treated by implantable cardioverter defibrillator (ICD) therapy.We report of a 28-year-old man with HCM and a dual chamber ICD, originally implanted for primary prevention of SCD, (programmed to AAI(R)-DDD(R); managed ventricular pacing (MVP) mode, Medtronic Inc. St Paul, MN USA). He presented with recurrent ICD shocks due to ventricular fibrillation (VF) despite antiarrhythmic therapy. Careful assessment of the stored electrograms demonstrated a repetitive pattern of VF initiation following short-long-short sequences. Initially, activation of ventricular rate stabilization (VRS) algorithm failed to prevent recurrent VF. Ultimately, deactivation of MVP and reprogramming the device to DDD mode with VRS on, resulted in arrhythmia suppression and avoidance of ICD shocks. Physicians should be aware that although VRS function is available in MVP mode, it does not function in the AAI mode during MVP; in order to effectively treat short-long-short sequence induced ventricular arrhythmia by device programming.

Effects of closed-loop stimulation vs. DDD pacing on haemodynamic variations and occurrence of syncope induced by head-up tilt test in older patients with refractory cardioinhibitory vasovagal syncope: the Tilt test-Induced REsponse in Closed-loop Stimulation multicentre, prospective, single blind, randomized study.

Closed-loop stimulation (CLS) seemed promising in preventing the recurrence of vasovagal syncope (VVS) in patients with a cardioinhibitory response to head-up tilt test (HUTT) compared with conventional pacing. We hypothesized that the better results of this algorithm are due to its quick reaction in high-rate pacing delivered in the early phase of vasovagal reflex, which increase the cardiac output and the blood pressure preventing loss of consciousness. This prospective, randomized, single-blind, multicentre study was designed as an intra-patient comparison and enrolled 30 patients (age 62.2 ± 13.5 years, males 60.0%) with cardioinhibitory VVS, carrying a dual-chamber pacemaker incorporating CLS algorithm. Two HUTTs were performed one week apart: one during DDD-CLS 60-130/min pacing and the other during DDD 60/min pacing; patients were randomly and blindly assigned to two groups: in one the first HUTT was performed in DDD-CLS (n = 15), in the other in DDD (n = 15). Occurrence of syncope and haemodynamic variations induced by HUTT was recorded during the tests. Compared with DDD, DDD-CLS significantly reduced the occurrence of syncope induced by HUTT (30.0% vs. 76.7%; P < 0.001). In the patients who had syncope in both DDD and DDD-CLS mode, DDD-CLS significantly delayed the onset of syncope during HUTT (from 20.8 ± 3.9 to 24.8 ± 0.9 min; P = 0.032). The maximum fall in systolic blood pressure recorded during HUTT was significantly lower in DDD-CLS compared with DDD (43.2 ± 30.3 vs. 65.1 ± 25.8 mmHg; P = 0.004). In patients with cardioinhibitory VVS, CLS reduces the occurrence of syncope induced by HUTT, compared with DDD pacing. When CLS is not able to abort the vasovagal reflex, it seems to delay the onset of syncope.

Safety of the Wearable Cardioverter Defibrillator (WCD) in Patients with Implanted Pacemakers.

The wearable cardioverter defibrillator (WCD) is an important approach for better risk stratification, applied to patients considered to be at high risk of sudden arrhythmic death. Patients with implanted pacemakers may also become candidates for use of the WCD. However, there is a potential risk that pacemaker signals may mislead the WCD detection algorithm and cause inappropriate WCD shock delivery. The aim of the study was to test the impact of different types of pacing, various right ventricular (RV) lead positions, and pacing modes for potential misleading of the WCD detection algorithm. Sixty patients with implanted pacemakers received the WCD for a short time and each pacing mode (AAI, VVI, and DDD) was tested for at least 30 seconds in unipolar and bipolar pacing configuration. In case of triggering the WCD detection algorithm and starting the sequence of arrhythmia alarms, shock delivery was prevented by pushing of the response buttons. In six of 60 patients (10%), continuous unipolar pacing in DDD mode triggered the WCD detection algorithm. In no patient, triggering occurred with bipolar DDD pacing, unipolar and bipolar AAI, and VVI pacing. Triggering was independent of pacing amplitude, RV pacing lead position, and pulse generator implantation site. Unipolar DDD pacing bears a high risk of false triggering of the WCD detection algorithm. Other types of unipolar pacing and all bipolar pacing modes do not seem to mislead the WCD detection algorithm. Therefore, patients with no reprogrammable unipolar DDD pacing should not become candidates for the WCD.

Recent impact study of automatic search function of the pacemaker atrial hysteresis on atrial arrhythmias

Objective: To explore the recent influences of pacemaker with automatic search function of atrial hysteresis on atrial arrhythmias, and to evaluate it clinical efficacy and safety. Methods: Indentify ADx DDD 5286 implanted dual chamber pacemaker for sick sinus syndrome in 43 cases. Automatic search of atrial lag was not opened with after pacemaker implantation, and the pacemaker settings were kept. Follow-up program after 3 months, DDD mode with automatic search of atrial lag was opened, and this mode was followed up for 6 months, comparing the atrial pacing percentage and DCG atrial tachyarrhythmias of pacemaker implantation to opening atrium lag mode. Results: Compared with the preoperative and operative 3 months later, dynamic electrocardiogram (DCG) 24 h showed that the number of atrial premature beats (APB) and atrial tachycardia, atrial fibrillation (AF) array increased ( p < .05); the cases of APB, atrial tachycardia and AF episodes were also increased ( p < .05). Compared with the automatic search function in atrial hysteresis model opened with and not opened: atrial pacing percentage decreased [0.54 (0.41, 0.71) vs. 0.82 (0.65, 0.93), p < .05]; DCG 24 h showed that the number of APB, AF episodes was reduced ( p < .05). Conclusions: Automation search function in atrial hysteresis model can obviously reduce the proportion of atrial pacing, reduce the occurrence of atrial arrhythmias; opened with automatic search function in atrial hysteresis model was safe and reliable.

Long-term outcome in patients receiving permanent pacemaker implantation for atrioventricular block: Comparison of VDD and DDD pacing.

A permanent pacemaker (PPM) with dual chamber pacing (DDD) offers atrioventricular synchronization for patients with atrioventricular block (AVB). Single lead atrial synchronous ventricular pacing mode (VDD) is an alternative, but there are concerns about its efficacy and risk of atrial undersensing. Whether VDD can be a good alternative in patients with AVB remains unknown. The aim of the present study was to compare the long-term risk of mortality of VDD with DDD pacing.A total of 207 patients undergoing PPM implantations for AVB with VDD mode were enrolled from 2000 to 2013. Another 828 age- and sex-matched patients undergoing DDD implantations during the same period of time were selected as the control group in a 1 to 4 ratio. The study endpoint was mortality.A total of 1035 patients (64.3% male) were followed up for 46.5 ± 43.2 months. The mean ages were 75.0 years for VDD, and 74.9 years for DDD. The Kaplan–Meier survival analysis showed no significant difference in long-term survival between the VDD and DDD groups (log-rank P = 0.313). After adjustment for baseline characteristics, the VDD and DDD groups had a similar long-term prognosis with an adjusted hazard ratio of 0.875 (P = 0.445). Further analyses for the risk of cardiovascular and noncardiovascular deaths also showed no significant differences between the 2 groups.The long-term prognosis of VDD mode is comparable to that of DDD mode. Single lead VDD can be considered as an alternative choice in patients with AVB without sinus nodal dysfunction.

216-35: Performance of the RYTHMIQ(TM) algorithm to minimize right ventricular pacing: a multicenter study

Background: In Boston Scientific dual-chamber devices, the RYTHMIQ(TM) algorithm aims to minimize RV pacing. We evaluated its performance by determining 1) the appropriateness of the switch from the AAI(R) with backup VVI pacing to the DDD(R) mode in case of suspected loss of AV conduction and 2) the rate of recorded pacemaker mediated tachycardia (PMT) when AV hysteresis searches for restored AV conduction. Conclusion: The RYTHMIQ algorithm shows: 1) high rate of inappropriate switch (mostly PVCs) and 2) high rate of induction of PMT. This may have clinical implications in terms of selection of the patients and may suggest required changes in the algorithm architecture.