John Silberbauer

The relationship between right ventricular pacing and atrial fibrillation burden and disease progression in patients with paroxysmal atrial fibrillation: the long-MinVPACE study.

AIMSnIn patients requiring permanent pacemaker implantation for sinus node disease (SND) or atrioventricular (AV) block, right ventricular (RV) pacing has been demonstrated to increase the risk of developing atrial fibrillation (AF). The effects of RV pacing in patients with paroxysmal AF are less well defined. Short- and medium-term studies have suggested no significant correlation between RV pacing and atrial fibrillation burden (AFB) measurement; we sought to assess for an effect in the long-term.nnnMETHODS AND RESULTSnSixty-six patients were randomized to receive either conventional dual chamber pacing (DDDR, n = 33), or dual chamber minimal ventricular pacing (MinVP, n = 33), for a period of at least 1 year. Patients were reviewed every 6 months and all pacemaker data were downloaded. The primary outcome measures were device-derived AFB and progression to persistent AF. The mean duration of study follow-up was 1.4 ± 0.6 years. Mean ventricular pacing was less in the MinVP cohort compared with the DDDR cohort (5.8 vs. 74.0%, P < 0.001). At follow-up, the device-derived AFB was significantly lower in the MinVP cohort when compared with the DDDR cohort (12.8 ± 15.3% vs. DDDR 47.6 ± 42.2%, P < 0.001). Kaplan-Meier estimates of time to onset of persistent AF showed significant reductions in the rates of persistent AF for MinVP pacing (9%) when compared with conventional DDDR pacing (42%), P = 0.004.nnnCONCLUSIONnRight ventricular pacing induces increased AFB in patients with paroxysmal AF in the long term. Dual chamber MinVP algorithms result in reduced AFB and reduced disease progression from paroxysmal to persistent AF in the long term.

Imaging and epicardial substrate ablation of ventricular tachycardia in patients late after myocarditis

AIMSnWe present clinical, electroanatomical mapping (EAM), imaging, and catheter ablation (CA) strategies in patients with myocarditis-related ventricular tachycardia (VT).nnnMETHODS AND RESULTSnBetween January 2010 and July 2012, 26 consecutive patients underwent imaging-guided CA of myocarditis-related ventricular arrhythmias, 23 of 26 using a combined endo-epicardial approach. Segment per segment correspondence of late enhanced (LE) scar localization with EAM scar was assessed in all patients with available uni/bipolar maps (n = 19). Induced VTs were targeted prior to substrate modification. Late potentials (LPs) abolition constituted a procedural endpoint independently from VT inducibility. Clinical monomorphic VT was induced in 15 of 26 patients (57.7%) and was associated with epicardial LPs in 10 of 15, completely abolished in 7 of 10 patients. Of the 10 patients rendered non-inducible VTs were ablated epicardially in 7. Late potentials were also detected in 7 of 11 initially non-inducible patients and completely abolished in 4. After a median follow-up of 23 (15-31) months, 20 of 26 patients (76.9%) remained free from VT recurrence. Bipolar mapping revealed low-voltage scar (<1.5 mV) in 1 patient endocardially and in 14 of 19 epicardially. Unipolar mapping revealed low-voltage scar (<8 mV) in 12 of 19 patients endocardially and in 18 of 19 epicardially. Correspondence of LE scar localization with endocardial bipolar scar was 1%, with endocardial unipolar scar 23.7%, with epicardial bipolar scar 39.8%, and with epicardial unipolar scar 66.2%.nnnCONCLUSIONnPre-procedural scar imaging and EAM findings support the necessity of an epicardial approach in patients with prior myocarditis. Epicardial unipolar mapping (<8 mV) is superior in scar identification and CA based on substrate modification is safe and effective in this setting.

Electrophysiological characteristics associated with symptoms in pacemaker patients with paroxysmal atrial fibrillation

PurposeThe purpose of this study is to identify the electrophysiological factors affecting symptoms in paroxysmal atrial fibrillation (PAF) using patients with paroxysmal atrial fibrillation and pacemakers with advanced atrial fibrillation (AF) diagnostics.MethodsSeventy-nine patients (age 71.0u2009±u20098.2, 54.4% male) with symptomatic PAF and AF burden of 1% to 50% with DDDRP pacemakers implanted were assessed for 6xa0months. Patients recorded symptom onset and duration and these were correlated with device-derived electrophysiological data.ResultsOf 2,638 AF episodes, 333 were symptomatic and 2,305 asymptomatic, with 194 non-atrial tachyarrhythmia symptomatic episodes giving a sensitivity of 12.6% and a positive predictive value of 63.2% for specific AF symptoms. Symptomatic AF episodes were 3.8 times more common diurnally than nocturnally (pu2009<u20090.001). Diurnally, symptomatic AF was significantly associated with a shorter AF cycle length (CL; pu2009=u20090.04), faster ventricular rate (pu2009=u20090.004), shorter PR interval (pu2009<u20090.001), faster preceding heart rate (pu2009=u20090.001) and increased early recurrence of AF (pu2009<u20090.04). Nocturnally, a significantly longer AF CL (pu2009=u20090.04) and PR interval (pu2009<u20090.001) prior to AF onset predicted symptomatic AF.ConclusionsSymptoms in PAF are predicted by changes in AF episode duration, ventricular rate during AF, preceding sinus heart rate, AV nodal conduction and AF cycle length but not ventricular irregularity. Excess diurnal sympathetic tone and excess nocturnal vagal tone predispose to symptomatic PAF. These findings may have relevance for therapies for symptom control of PAF.

The usefulness of minimal ventricular pacing and preventive AF algorithms in the treatment of PAF: the ‘MinVPace’ study

IntroductionThe beneficial effects of atrial pacing on the incidence, duration and symptomatology of paroxysmal atrial fibrillation (PAF) may be negated by increased ventricular pacing. This prospective randomised study evaluates the effect of pacing algorithms that minimise ventricular pacing (MinVP) with and without anti-AF algorithms, on AF burden (AFB) in patients with symptomatic PAF.MethodsPatients implanted with pacemakers with MinVP capability with AFB 1–70% were enrolled. Three different DDDRP devices were assessed. Following a 1-month induction phase, patients were randomised to MinVP with and without preventive AF algorithms or dual chamber rate adaptive pacemaker (DDDR) (AV delay (AVD) 150xa0ms) for 2xa0months per study phase. The primary outcome measure was AFB.ResultsOne hundred and ten patients were enrolled; of these, 66 (mean age 74.3u2009±u20097.9, 56% males) had an AFB of 1–70% during the induction phase and completed all study phases. There was no significant difference in AFB between the control phase DDDR, 13.8% (95% CI 8.7 to 18.8), and MinVP, 14.4% (95% CI 9.4 to 19.4), or MinVP with AF algorithms enabled, 14.7% (95% CI 9.7 to 19.7), (pu2009=u20090.65 and pu2009=u20090.49, respectively). Median ventricular pacing was significantly higher during the control phase, 86.0% (IQR 72.8, 97.3), than in MinVP 2.0% (IQR 0.0, 14.1) and MinVPu2009+u2009algorithms 3.0% (IQR 0.4, 15.6), pu2009=u2009<u20090.001.ConclusionMinVP algorithms are effective in reducing ventricular pacing. However, there is no significant reduction in AFB with minimal ventricular pacing algorithms in the short term. No additional benefit or adverse outcome was found with preventative anti-AF algorithms in combination with MinVP algorithms.

Tissue Doppler–Derived Contractile Reserve Is a Simple and Strong Predictor of Cardiopulmonary Exercise Performance across a Range of Cardiac Diseases

Resting echocardiographic measures of cardiac function such as left ventricular ejection fraction correlate poorly with exercise capacity. Assessment during exercise using measures less dependent on hemodynamic loading conditions, such as tissue Doppler imaging (TDI), may more accurately characterize the relationship between cardiac function and exercise capacity.

The relationship between high-frequency right ventricular pacing and paroxysmal atrial fibrillation burden

AIMSnRight ventricular pacing increases the risk of persistent atrial fibrillation (AF) in the long term. The effects of right ventricular pacing on paroxysmal AF (PAF) are unknown. The aim was to examine the effect of right ventricular pacing on AF burden (AFB) in patients with symptomatic drug-resistant PAF. Pooled analysis of pacemaker-derived counters and AF diagnostic data from the Atrial Fibrillation Therapy (AFT) and Pacemaker Atrial Fibrillation Suppression (PAFS) randomized anti-AF pacemaker algorithm trials were used.nnnMETHODS AND RESULTSnFive hundred and fifty-four patients from the AFT (n = 372) and PAFS (n = 182) were studied. The individual percentages of pacing, Atrial Sense Ventricular Pace (ASVP), Atrial Pace Ventricular Pace (APVP), and Atrial Pace Ventricular Sense (APVS) as well as total ventricular pacing during synchronous rhythm (VPinSR, %) were examined for an effect on AFB. Three hundred and twenty-one (AFT, age 64 +/- 11, 55% male) and 79 (PAFS, age 71 +/- 8, 54% male) patients had complete data for analysis. Increased VPinSR was weakly associated with an increased AFB (effect size-10% VPinSR increased AFB by only 0.03%) in AFT (P = 0.04) but not PAFS (P = 0.98) or the pooled analysis (P = 0.95). None of the synchronous paced modalities (ASVP, APVP, APVS) significantly increased AFB compared with sinus rhythm (Atrial Sense Ventricular Sense) (P = ns).nnnCONCLUSIONnNo pacing modality, atrial or ventricular, had a significant effect on AFB. On the basis of these data, the detrimental effect of high-frequency right ventricular pacing on AFB in paced PAF patients, unlike with persistent AF, appears to be minimal in the short term.

Limitations to High Intensity Exercise Prescription in Chronic Heart Failure Patients

Background: Interval training is recommended for chronic heart failure patients (CHF), but specific guidelines on setting appropriate workloads have not been fully established. The aim of this study was to compare a traditional method of interval training prescription with a protocol specifically designed for CHF. Methods: Ten CHF and 7 healthy controls performed 2 maximal incremental cycle tests to determine interval training workload; a standard test (10 W min−1) and a steep test (25 W.10−s). Peak work rate and oxygen uptake (VO2peak) were determined. Training workloads were defined as 100% standard test and 50% steep test peak work rate. Results: Training workload determined from the standard test was higher than from the steep test in healthy controls (151 ± 17 W vs 118 ± 13 W; P < 0.01), whereas in CHF there was no significant difference between methods (88 ± 10 W vs 96 ± 9 W; P > 0.05). Steep test VO2peak reached 91 ± 5% of standard test VO2peak in controls, and 99 ± 4% in CHF, with no significant differences between tests in either group. Conclusion: Prescribing interval training from a standard test results in higher workloads than from a steep test in healthy individuals, but in CHF both methods prescribe similar workloads. However it should not be assumed that the two tests can be used interchangeably for CHF. This small-sized study raises issues about interval training prescription that may be hypothesis-generating for future larger-scale studies.

The Effect of Bipole Tip‐to‐Ring Distance in Atrial Electrodes upon Atrial Tachyarrhythmia Sensing Capability in Modern Dual‐Chamber Pacemakers

Introduction: Accurate atrial arrhythmia discrimination is important for dual chamber pacemakers and defibrillators. The aim was to assess the accuracy of atrial arrhythmia recording using modern devices and relate this to atrial tip‐to‐ring (TTR) distance.

Validating optimal function of the closed loop stimulation sensor with high right septal ventricular electrode placement in 'ablate and pace' patients.

PurposeThe study aim was to validate the closed loop stimulation (CLS) vs. accelerometer (ACC) rate-responsive sensors with electrodes placed in the right ventricular high septal (RVHS) or right ventricular apical (RVA) lead positions in patients following ‘ablate and pace’ therapy for persistent atrial fibrillation.Methods‘Ablate and pace’ patients were randomised to either RVHS or RVA electrode placement with a dual sensor device. A double-blind crossover study comparing CLS vs. ACC rate-response pacing modes was undertaken. Subjects undertook cardiopulmonary testing with constant workload light exercise followed by a ramp protocol in addition to activity of daily living assessments.ResultsTwenty subjects (14 male; age, 74u2009±u20098xa0years) were studied. Heart rate increase was greater from lying to sitting with ACC. With mental stress, heart rate increase was greater with CLS. Peak heart rates were similar for stair ascent and descent in ACC mode. With CLS mode, however, the peak heart rate was significantly lower for stair descent. There was no difference between modes in mean response time, oxygen deficit, peak VO2, VO2 at anaerobic threshold, peak heart rate, total exercise time and total workload. CLS function was equally optimal at both electrode sites.ConclusionsCLS rate adaptive pacing is appropriate for ‘ablate and pace’ patients, and this sensor functions equally well using RVA or RVHS lead positions.

The role of pacing in rhythm control and management of atrial fibrillation.

Atrial fibrillation is the most common sustained cardiac arrhythmia and is increasing in prevalence with an ageing population. As the arrhythmia is often asymptomatic the true prevalence is likely even higher. Largely because of stroke this arrhythmia places a huge financial burden on the health economy. Despite this, large studies assessing rate versus rhythm control have been equivocal. Because of the ineffectiveness of pharmacological therapy much research effort has been undertaken in device and ablative approaches to rhythm management. Although catheter ablation has gained favour because of the high success rates the technique requires considerable expertise and still has a significant complication profile maintaining interest in pacing therapies for atrial fibrillation. Dual chamber versus single-chamber ventricular pacing has been shown to significantly reduce the incidence of atrial fibrillation. Research is currently underway to see if minimising the deleterious effects of right ventricular apical pacing could further increase the benefits of atrioventricular synchronous pacing. Several studies show some (albeit variable) reduction in AF burden with anti-AF algorithms in the setting of bradycardia. Antitachycardia pacing, on the other hand, has not been shown to treat AF in a randomised trial despite the successful termination of co-existent atrial tachycardias. There is increasing evidence that alternative atrial pacing sites may treat AF by improving atrial function. Furthermore, these strategies coupled with other therapies in a ‘hybrid approach’ have also showed promising results.