Atrioventricular Interval Research Articles

Reference Ranges for Fetal Atrioventricular and Ventriculoatrial Time Intervals and Their Ratios during Normal Pregnancy

Background: The diagnostic assessment of fetal arrhythmias relies on the measurements of atrioventricular (AV) and ventriculoatrial (VA) time intervals. Pulsed Doppler over in- and outflow of the left ventricle and tissue Doppler imaging are well-described methods, while Doppler measurements between the left brachiocephalic vein and the aortic arch are less investigated. The aim of this study was to compare these methods of measurement, to find influencing factors on AV and VA times and their ratio, and to create reference ranges. Methods: Echocardiography was performed between 16 and 40 weeks of gestation in normal singleton pregnancies. Nomograms for the individual measurements were created using quantile regression with Matlab Data Analytics. Statistical analyses were performed with GraphPad version 5.0 for Windows. Results: A total of 329 pregnant women were enrolled. A significant correlation exists between AV and VA times and gestational age (GA) (p = 0.0104 to <0.0001, σ = 0.1412 to 0.3632). No correlation was found between the AV:VA ratio and GA (p = 0.08 to 0.60). All measurements differed significantly amongst the studied methods (p < 0.0001). Conclusions: AV and VA intervals increase proportionally with GA; no other independent influencing factors could be identified. As significant differences exist between the three methods of assessment, it is crucial to use appropriate reference ranges to diagnose pathologies.

Pacing failure caused by automatic pacing threshold adjustment system

Ventricular capture management is an automatic pacing threshold adjustment algorithm that automatically measures pacing threshold through detection of the evoked response after a pacing stimulus. Although it is principally designed to save device battery under the maintenance of the patient׳s safety, we experienced a rare case with serious pacing failure due to a weakness of this algorithm. This pacing failure might be explained by a large variation in the ventricular pacing threshold depending on the atrioventricular interval and daily variation of pacing threshold and concomitant steroid use in this patient.

P19.04: Fetal atrioventricular time intervals assessed by three different pulsed‐wave Doppler methods

P19.04: Fetal atrioventricular time intervals assessed by three different pulsed‐wave Doppler methods

Prediction of optimal cardiac resynchronization by vectors extracted from electrograms in dyssynchronous canine hearts.

Proper optimization of atrioventricular (AV) and interventricular (VV) intervals can improve the response to cardiac resynchronization therapy (CRT). It has been demonstrated that the area of the QRS complex (QRSarea) extracted from the vectorcardiogram can be used as a predictor of optimal CRT-device settings. We explored the possibility of extracting vectors from the electrograms (EGMs) obtained from pacing electrodes and of using these EGM-based vectors (EGMVs) to individually optimize acute hemodynamic CRT response. Biventricular pacing was performed in 13 dogs with left bundle branch block (LBBB) of which five also had myocardial infarction (MI), using 100 randomized AV- and VV-settings. Settings providing an acute increase in LV dP/dtmax ≥ 90% of the highest achieved value were defined as optimal. The prediction capability of QRSarea derived from the EGMV (EGMV-QRSarea) was compared with that of QRS duration. EGMV-QRSarea strongly correlated to the change in LV dP/dtmax (R = -0.73 ± 0.19 [LBBB] and -0.66 ± 0.14 [LBBB + MI]), while QRS duration was more poorly related to LV dP/dtmax changes (R = -0.33 ± 0.25 [LBBB] and -0.47 ± 0.39 [LBBB + MI]). This resulted in a better prediction of optimal CRT-device settings by EGMV-QRSarea than by QRS duration (LBBB: AUC = 0.89 [0.86-0.93] vs. 0.76 [0.69-0.83], P < 0.01; LBBB + MI: AUC = 0.91 [0.84-0.99] vs. 0.82 [0.59-1.00], P = 0.20, respectively). In canine hearts with chronic LBBB with or without MI, the EGMV-QRSarea predicts acute hemodynamic CRT response and identifies optimal AV and VV settings accurately. These data support the potency of EGM-based vectors as a noninvasive, easy and patient-tailored tool to optimize CRT-device settings.

Adaptive CRT in patients with normal AV conduction and left bundle branch block: Does QRS duration matter?

BackgroundAdaptive cardiac resynchronization therapy (aCRT) is a dynamic optimization algorithm which paces only the left ventricle (LV) when atrio-ventricular (AV) conduction is normal, thus reducing right ventricular (RV) pacing. However, the impact of QRS duration on aCRT efficacy remains uncertain. We examined whether QRS duration impacts aCRT effectiveness in patients with left bundle branch block (LBBB) and preserved AV conduction. MethodsRandomized patients in the Adaptive CRT trial, which enrolled NYHA III/IV patients, were used in this analysis. Patients were randomized to receive aCRT or echo-optimized bi-ventricular CRT (control arm). Endpoints for this analysis were clinical composite score (CCS) at 6months post-implant and time to first heart failure (HF) hospitalization or death. ResultsAmong the 199 patients with LBBB and normal AV intervals at baseline, 80 patients (40%) had a baseline moderately wide QRS of 120–150ms. In this subgroup, a greater proportion of aCRT patients had an improved CCS (79% vs. 50%) at 6months compared to the control group (p=0.03). There was also a trend toward a lower risk of death or HF hospitalization (hazard ratio: 0.53; 95% CI: 0.24–1.15; p=0.10) in the moderately wide QRS subgroup with aCRT compared to the control arm. In the wide QRS subgroup, the efficacy was comparable in both treatment arms. ConclusionAdaptive CRT was associated with improved patient outcomes over echo-optimized bi-ventricular CRT in patients with preserved AV conduction, LBBB, and moderately wide QRS.The adaptive cardiac resynchronization therapy trial (ClinicalTrials.gov Identifier: NCT00980057) was sponsored by Medtronic plc, Mounds View, MN.

Abstract 12968: Early AV Conduction Recovery After Pacemaker Placement for High-Degree AV Block Secondary to Transcatheter Aortic Valve Replacement

Introduction: Recovery of conduction has been demonstrated in &gt;50% of patients who receive pacemakers (PPMs) for high-degree atrioventricular block (HDAVB) after trans-catheter aortic valve replacement (TAVR). Little information is available about the time course of conduction recovery in these patients, and there is little comparative data regarding resolution of AV block after balloon-expandable compared to self-expanding valves. Methods: A retrospective review was performed of patients who underwent TAVR with balloon and self-expanding valves and required PPMs for HDAVB at 2 institutions. Serial PPM interrogations were analyzed to detect recovery of AV conduction. Analysis was performed to identify predictors and timing of conduction recovery. Results: Of a total population of 578 patients, 54 (9.3%) received PPMs for HDAVB. In multivariate analysis, predictors of HDAVB requiring a PPM included right bundle branch block (OR 5.99 [3.08 -11.6]), atrial fibrillation (OR 1.87 [1.02-3.45]), and self-expanding valves (OR 3.45 [1.85-6.43]). Of the 54 patients who received PPMs, 38 had follow-up sufficient to evaluate AV conduction recovery. Of these, 23 (61%) showed recovery of AV nodal conduction; 20 had already recovered by their first interrogation a median of 22 days (IQR 14-31) post PPM placement (figure). There were no statistically significant predictors of AV nodal conduction recovery, including type of valve implanted. For those who recovered conduction, 9/23 (39%) had ventricular pacing &gt;50% of the time on their final interrogation, of whom 5 had programmed AV intervals &lt;200 msec. Conclusions: A majority of patients who receive PPMs for HDAVB after TAVR recover AV conduction during follow-up, and in most patients conduction recovery occurs within weeks. These findings imply that longer observation periods may be appropriate after TAVR before PPM implantation, and programming that minimizes ventricular pacing may be beneficial.

Accessory pathway location affects brain natriuretic peptide level in patients with Wolff-Parkinson-White syndrome.

The purpose of this study was to investigate the relationship between the accessory pathway location and brain natriuretic peptide (BNP) level in patients with Wolff-Parkinson-White (WPW) syndrome. We divided 102 WPW syndrome patients with normal left ventricular systolic function into four groups: those with manifest right (MR, n = 14), manifest septal (MS, n = 11), manifest left (ML, n = 30), and concealed (C, n = 47) accessory pathways. BNP level and electrophysiological properties, including difference in timing of the ventricular electrogram between the His bundle area and the distal coronary sinus area (His-CS delay), which indicate intraventricular dyssynchrony, were compared. BNP levels (pg/dl) were higher in the MR and MS groups than in the ML and C groups (MR, 64 ± 58; MS, 55 ± 45; ML, 17 ± 15; C, 25 ± 21; P < 0.001). AV intervals (ms) were shorter in the MR and MS groups than in the ML and C groups (MR, 76 ± 16; MS, 83 ± 6; ML, 101 ± 19; C, 136 ± 20; P < 0.001). His-CS delay (ms) was longer in the MR group than in the other groups (MR, 50 ± 15; MS, 21 ± 7; ML, 23 ± 10; C, 19 ± 8; P < 0.001). The AV interval (P < 0.01) and the His-CS delay (P < 0.001) were negatively and positively correlated, respectively, with the BNP level. Anterograde conduction with a right or septal accessory pathway increased the BNP level in WPW syndrome patients with normal cardiac function.

Spike on T wave! What went wrong?

An 80-year-old male, who previously received a dual chamber pacemaker, was referred to our ambulatory for dizziness and fatigue. The ECG obtained showed sinus rhythm, highly variable atrioventricular (AV) interval and alternation between spontaneous and paced ventricular complexes. A spike on the ascending part of the T wave was observed, suggesting ventricular undersensing. However, telemetry-supported pacemaker control showed inconstant atrial undersensing.

Complex and interacting influences of the autonomic nervous system on cardiac electrophysiology in conscious mice.

Mice may now be the preferred animal model for biomedical research due to its anatomical, physiological, and genetic similarity to humans. However, little is known about accentuated antagonism of chronotropic and dromotropic properties in conscious mice. Accordingly, we describe the complex and interacting influence of the autonomic nervous system on cardiac electrophysiology in conscious mice. Specifically, we report the effects of single and combined cardiac autonomic blockade on measurements of pulse interval (heart rate), atrio-ventricular interval, sinus node recovery time (SNRT), SNRT corrected for spontaneous sinus cycle, and Wenckebach cycle length in conscious mice free of the confounding influences of anesthetics and surgical trauma. Autonomic influences were quantified as the change in parameter induced by its selective blocker (Sympathetic or Parasympathetic Effect) or as the difference between the intrinsic value and the value after a selective blocker (Sympathetic or Parasympathetic Tonus). Sympatho-Vagal Balance (SVB) was assessed as the ratio of control interval to intrinsic interval. SVB suggests slight parasympathetic dominance in the control of cardiac electrophysiology intervals. Furthermore, results documents a complex interaction between the sympathetic and parasympathetic divisions of the autonomic nervous system in the control of cardiac electrophysiology parameters. Specifically, the parasympathetic effect was greater than the parasympathetic tonus in the control of cardiac electrophysiology parameters. In contrast, the sympathetic effect was smaller than the sympathetic tonus in the control of cardiac electrophysiology parameters. Results have important implications because actions of pharmacological agents that alter the autonomic control of cardiac electrophysiology are transformed by these interacting mechanisms.

Temporary severe bradycardia due to pacemaker programming.

A 67-year-old male patient received a pacemaker for syncope. His parameters at check-up were: P/R amplitude 2.8/11 mV and atrial/ventricular threshold 0.875/0.625. The pacemaker was programmed as follows: lower rate 60 bpm; upper tracking rate 130 bpm; sensed AV interval 120 ms; paced AV interval 50 ms; atrial/ventricular sensitivity 0.5/5.6 mV, and atrial/ventricular output 2/2 V. Due to syncope in his history, the rate drop response was also activated: drop size 25 bpm; drop rate 50 bpm; detection beats: 2 beats. Both with an intervention rate of 100 bpm. The following ECG was recorded during carotid massage (Fig. 1). What is the explanation for this interesting ECG recording? Fig. 1 ECG recording during carotid massage: Lead I, marker channel, ventricular EGM

216-36: A Case with Pacing Failure due to the Pitfall of Automatic Pacing Threshold Adjustment

Although the automatic pacing output adjustment algorithm is smart and has been widely implemented in clinical pacemakers, we experienced a case with serious pacing failure through the pitfall of this system. A 63 year-old female underwent pacemaker implantation (MedtronicR Advisa DR) due to complete atrioventricular block in 2010. There were no specific episodes during the initial 4 years, but she suddenly suffered from syncope in 2014. The ECG showed irregular spontaneous heart beat with 30/min and uncaptured pacing spikes in rate of 60/min. The ventricular lead dislodgement was ruled out in the chest X-ray. The pacemaker interrogation revealed unchanged lead impedance, but the ventricular pacing out-put was set at 3.0 V with 0.6 ms through the automatic threshold adjustment, because the most recent ventricular pacing threshold was 0.625 V with 0.4 ms. We performed manual threshold testing with various AV intervals of 80, 120, 220 ms and various atrial rate of 100 and 120 bpm. Interestingly, the ventricular pacing threshold was influenced by the AV interval, i.e., the shorter the AV interval, the lower the pacing threshold (e.g., 1.00V, 1.25V, 1.75V at atrial rate of 100bpm, 1.00V, 1.00V, 1.50V at atrial rate of 120bpm, respectively). Because the routine automatic pacing threshold algorism uses a short AV interval (110 ms) to avoid fusion from native conduction, this algorism resulted in improper recommendation to use inappropriately lower pacing out-put in a programmed AV interval (160 ms). In addition, this case showed large day-to-day variation in pacing threshold ranging from 0.625V to 1.625V even in the same rate and AV interval. After reprogramming the ventricular output to provide an adequate safety margin (3.5V), consistent ventricular capture was achieved and no pacing failure was found in further observation.

176-70: Cardiac resynchronization therapy: long-term results of atrioventricular and interventricular delay optimization by ECG

Purpose: To assess the role of atrioventricular (AVD) and interventricular delay (VVD) optimization in CRT devices based on changes in PR interval and the width of QRS complex using standard ECG on hemodynamic parameters in the five year period. Materials and methods: The randomized study involving 128 patients in sinus rhythm after CRT implantation according to the guidelines. 2 patient groups were taken: 1) AVD and VVD optimization, n = 63, 2) only AVD optimization (conventional treatment), n = 65. Standard follow-up protocol, echocardiography as well as optimization of AVD and VVD were carried out every 6 months during 5 years. The target sensed/paced AV interval was assumed to the finished symmetrical intrinsic/stimulated P wave respectively. VVD optimization was implemented by gradual change of stimulation delay time of the right/left ventricle preactivation (from zero to 40 ms) and simultaneous measurement of the biventricular QRS width on ECG. The final VVD was assumed to the narrowest biventricular QRS complex (bivQRS). The heart failure (HF) functional class assessing was implemented by clinical evaluation and a six-minute walk test. Results: There were no differences in HF etiology, ECG and echocardiography parameters between the groups. For 5 year follow-up there was significant reduction in the bivQRS width in Group I, p = 0.042. Final values of the bivQRS and intrinsic QRS width were lower in Group I, p = 0.016 and p = 0.044 respectively. End-systolic and end-diastolic LV volumes decreased in both groups; reduction in the end-systolic LV volume was greater in Group I, p = 0.039. Ejection fraction (EF) increased in both groups, the degree of EF increase was higher in Group I, p = 0.048. Normalization of LV systolic function (EF ≥ 50%) occurred in 16 patients in Group I and 4 patients in Group II, p = 0.033. HF functional class decreased in both groups; the final value was lower in Group I, 2.12 versus 2.64 in Group II, p = 0.022. The survival analysis (Kaplan-Meier) showed no significant differences: p = 0.787 (Log-Rank test).

136-71: Echocardiographic Response to Dual vs Single Optimal Left Ventricular Resynchronization Therapy

Puropose of the study: The Dual Site LV Pacing study was a randomized, prospective, single center trial comparing dual LV +RV CRT with standard single LV CRT, with LV lead in optimal mid/basal lateral position. Method used: Thirty-nine patients (23 male) mean LVEF 27 ±10, 20 ischemic, NSR, LBBB, meeting standard CRT criteria, were randomized to single LV + RV (s-CRT) or Dual LV + RV CRT(d-CRT), and crossed over after 3 months to the other arm. Medications and AV intervals were carefully optimized. One LV lead was positioned mid or basal lateral, and the other anterior or posterior lateral closer to the apex. Maximal physical LV lead separation was attempted, requiring a positive fixation lead in 15, retaining coronary venous stents (12), coronary venoplasty (4). Echocardiograms performed at baseline, after 3 months, and 6 months were interpreted by a blinded echocardiographer. Summary of results: After 3 months, there was a greater percentage increase in EF in d-CRT (51%) than s-CRT (42%), although this difference was not significant. After crossover, there was similar further increase in LVEF % in both groups (4% vs 7%).

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.

OP-012 Assessment of Av Interval Optimisation Results With Echocardiography and Impedance Cardiography in Patients with Biventricular Pacemaker

OP-012 Assessment of Av Interval Optimisation Results With Echocardiography and Impedance Cardiography in Patients with Biventricular Pacemaker

Repetitive nonreentrant ventriculoatrial synchrony: An underrecognized cause of pacemaker-related arrhythmia

Similar to endless loop tachycardia (ELT), repetitive nonreentrant ventriculoatrial synchrony (RNRVAS) is a ventriculoatrial (VA) synchrony pacemaker-mediated arrhythmia. RNRVAS was first described in 1990 and can only occur in the presence of retrograde VA conduction and dual-chamber or cardiac resynchronization devices with tracking (P-synchronous ventricular pacing such as DDD, DDDR) or nontracking pacing modes that allow AV-sequential pacing (DDI, DDIR). RNRVAS is promoted by (1) high lower rate limit or any feature that allows rapid pacing, (2) long AV intervals, or (3) long postventricular atrial refractory period (PVARP). In contrast to ELT, RNRVAS is a less well-recognized form of pacemaker-mediated arrhythmia; thus, unlike ELT, there are no specific device algorithms to prevent, recognize, and terminate RNRVAS. However, RNRVAS has been recently shown to occur frequently. We present a series of cases, some of which were found fortuitously. Owing to its clinical implications, we propose that algorithms should be developed to prevent, identify, and terminate RNRVAS.

EVOLUTION OF THE FETAL ATRIOVENTRICULAR (AV) INTERVAL FROM 6-40 WEEKS OF GESTATION

Fetal atrioventricular (AV) conduction can be indirectly assessed by measuring the Doppler-derived AV interval (AVI) at fetal echocardiography. Normal values have been published from 16-18 weeks gestational age (GA) to term. We sought to investigate the evolution of the AV interval from 6 to 40

Hemodynamic device-based optimization in cardiac resynchronization therapy: concordance with systematic echocardiographic assessment of AV and VV intervals

Hemodynamic device-based optimization in cardiac resynchronization therapy: concordance with systematic echocardiographic assessment of AV and VV intervals M&aacute;rio M Oliveira, Luisa M Branco, Ana Galrinho, Nogueira da Silva, Pedro S Cunha, Bruno Valente, Joana Feliciano, Ricardo Pimenta, Ana Sofia Delgado, Rui Cruz Ferreira Santa Marta Hospital, Lisbon, Portugal Background: Inappropriate settings of atrioventricular (AV) and ventriculo-ventricular (VV) intervals can be one of the factors impacting response to cardiac resynchronization therapy (CRT). Optimal concordance of AV and VV intervals between echocardiographic-based assessment and a device-based automatic programming with a hemodynamic sensor was investigated, together with left ventricle (LV) reverse remodeling after 6 months of regular automatic device-based optimization.Methods: We evaluated blindly 30 systematic echocardiographic examinations during 6 months in 17 patients (12 men, 64&plusmn;10 years, in sinus rhythm and New York Heart Association class III; 76% with non-ischemic dilated cardiomyopathy, LV ejection fraction [LVEF] &lt;35%, QRS 130 milliseconds and LV dyssynchrony) implanted with the SonRtip lead and a cardioverter-defibrillator device. Dyssynchrony (AV, VV, or intraventricular) was evaluated by an experienced operator blinded to the device programming, using conventional echocardiography, tissue synchronization imaging, tissue Doppler imaging, radial strain, and 3D echocardiography.Results: Either no AV or VV dyssynchrony (n=11; 36.7%) or a slight septal or lateral delay (n=13; 43.3%) was found in most echocardiography examinations (80%). AV or VV dyssynchrony requiring further optimization was identified in one-fifth of the examinations (20%). At 6 months, 76.5% patients were responders with LV reverse remodeling, of which 69% were super-responders (LVEF &gt;40%). A statistically significant increase in LVEF was observed between baseline and 6 months post implant (P&lt;0.01). One patient died from non-cardiac causes.Conclusion: Concordance between echocardiographic methods and device-based hemodynamic sensor optimization was found in most examinations (80%) post CRT. After 6 months of systematic optimization with SonR, patients showed a statistically significant increase in LVEF, with a high rate of reverse remodeling. Keywords: cardiac resynchronization therapy, hemodynamic sensor, atrioventricular delay, interventricular delay, reverse remodeling

Shortness of breath in a patient with complete heart block and permanent pacemaker: A case of effective pacemaker reprogramming

An 82-year-old frail woman with a prior history of hypertension, complete heart block, and dual permanent pacemaker (Sensia DR SEDR01, Medtronic Inc., Minneapolis, MN) presented to pacemaker clinic with symptoms of shortness of breath (SOB), dizziness, and “low pulse rate”. Pacemaker interrogation showed underlying normal sinus rhythm, sinus rate of around 74 beats/ min with atrial sensed events, and ventricular paced rhythm with frequent symptomatic premature ventricular complexes (PVC). Pacemaker parameters were DDD, lower rate limit (LRL) of 60 beats/min, and maximum tracking rate of 120 beats/min, along with paced/sensed AV delay of 300/250 ms. Also noted was high pacing threshold of 3.5 V at 1 ms in the atrial lead with normal sensing parameters. In view of these, the pacemaker mode was reprogrammed to VDD mode and the patient was given betablocker therapy for frequent PVCs. She presented to arrhythmia clinic a few weeks later because of worsening SOB, light-headedness, and transient ischemic attacklike symptoms. Electrocardiography (ECG) performed in the clinic showed ventricular paced rhythmwith retrograde P waves (Fig. 1). What was the underlying arrhythmia mechanism? What treatment options are available? 2. Discussion

Vectorcardiography for optimization of stimulation intervals in cardiac resynchronization therapy.

Current optimization of atrioventricular (AV) and interventricular (VV) intervals in cardiac resynchronization therapy (CRT) is time consuming and subject to noise. We aimed to prove the principle that the best hemodynamic effect of CRT is achieved by cancelation of opposing electrical forces, detectable from the QRS morphology in the 3D vectorcardiogram (VCG). Different degrees of left (LV) and right ventricular (RV) pre-excitation were induced, using variation in AV intervals during LV pacing in 20 patients with left bundle branch block (LBBB) and variation in VV intervals during biventricular pacing in 18 patients with complete AV block or atrial fibrillation. The smallest QRS vector area identified stimulation intervals with minimal systolic stretch (median difference [IQR] 20 ms [−20, 20 ms] and maximal hemodynamic response (10 ms [−20, 40 ms]). Reliability of VCG measurements was superior to hemodynamic measurements. This study proves the principle that VCG analysis may allow easy and reliable optimization of stimulation intervals in CRT patients.