Safety and efficacy of direct oral anticoagulants in bioprosthetic valves: A systematic review and meta-analysis

Background

Direct oral anticoagulants are efficient alternatives to vitamin K antagonists. There is little evidence regarding their use in patients who underwent bioprosthetic valve replacement whether surgically or through a transcatheter approach and have another indication of anticoagulation. Trials have compared different members of the DOACs family to VKAs and showed that they were at least non-inferior to VKAs with regard to safety and efficacy. However, this is still controversial. Our meta-analysis aims at providing a clearer view of their future use in this subgroup of patients.

Methods

PubMed and Cochrane were searched for randomised clinical trials and observational studies. Bleeding, stroke, and all-cause mortality were the outcomes of interest.

Results

Ten papers with a total of 4,088 patients were included. Our meta-analysis revealed no significant differences between the incidence of bleeding between DOACs and warfarin (16% vs. 17%, OR = 0.94, 95% CI [0.56-1.57], p = 0.81, I 2 = 81%). No statistical difference was found in stroke between both groups (2.5% vs. 3.3%, OR = 0.75, 95% CI [0.41-1.38], p = 0.36, I 2 = 35%). All-cause mortality was not statistically significant between both groups (9.2% vs. 13.7%, OR = 0.85, 95% CI [0.68-1.07], p = 0.16, I 2 = 56%). Interestingly, subgroup analysis of randomised controlled trials and prospective studies favoured DOACs with lower risks of both bleeding and stroke.

Conclusion

Direct oral anticoagulants appear to be at least as safe and effective as VKAs in patients with bioprosthetic valves and another indication of anticoagulation. There could be potential benefit from the use of DOACs; however, further evidence is required.

Systematic Review Registration

https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42021222146, identifier CRD42021222146.

Outcomes of very high-power short-duration ablation using 90w for pulmonary vein isolation in patients with atrial fibrillation: a real world observation study

Introduction

Pulmonary vein isolation (PVI) ablation is the established gold standard therapy for patients with symptomatic drug refractory atrial fibrillation (AF). Advancements in radiofrequency (RF) ablation, have led to the development of the novel contact force-sensing temperature-controlled very high-power short-duration (vHPSD) RF ablation. This setting delivers 90W for up to 4 seconds with a constant irrigation flow rate of 8ml/min. The aim of this study was to compare procedural outcomes and safety with conventional radiofrequency ablation.

Methods

An observational study was conducted with patients who underwent first time PVI ablation from 2019 to 2021. The cohort was divided in to: 1) vHPSD ablation – QMODE+ via QDOT MICRO catheter, 2) QMODE via QDOT MICRO catheter and 3) Conventional power-controlled RF (PCRF) ablation via THERMOCOOOL SMARRTOUCH SF (STSF) catheter. The QMODE+ vHPSD ablation group was prospectively recruited while the QMODE and PCRF group were retrospectively collected. Primary outcomes were procedural success, PVI duration, ablation duration and incidence of perioperative adverse events. Secondary outcomes were intraprocedural morphine and midazolam requirement.

Results

A total of 155 patients were included in the study with 80, 30 and 45 patients in the QMODE+ (vHPSD), QMODE and PCRF, respectively. PVI was successfully attained in all patients. QMODE+ (vHPSD) demonstrated significantly reduced time required for PVI and total energy application in comparison to the QMODE and PCRF groups (68.3±3.30 vs. 92.9±4.86 vs. 93.6±4.34 min, P<0.0001; 9.7±0.452 vs. 33.9±0.452 vs. 36.0±1.56 min, P<0.0001, respectively) (Figure 1). Intravenous morphine and midazolam requirement was lower in the QMODE+ (vHPSD) group compared to the QMODE and PCRF groups (10.3±0.45 vs. 16.1±0.935 vs. 15.3±0.686 mg, P<0.0001; 4.05±0.402 vs. 8.63±1.07 vs. 8.58±0.821 mg, P<0.0001) (Figure 2). QMODE+ (vHPSD) observed a non-significant reduction in fluoroscopy time compared to QMODE and PCRF. One cardiac tamponade were observed in both the QMODE+ (vHPSD) and QMODE group while the PCRF group exhibited an embolic stoke and two pericardial effusions that did not require drainage.

Conclusion

In this study, QMODE+ (vHPSD) demonstrated a comparable safety profile to the other treatment arms. Procedural duration and energy application time was substantially reduced while a non-significant reduction was observed for fluoroscopy time for QMODE+. Furthermore, sedation requirement was reduced and thus potentially conveyed greater patient tolerability of the procedure when conducted with QMODE+.

Notwithstanding the limitations of observational study design, these preliminary findings are promising with respect to periprocedural outcomes and safety of QMODE+. Longer term outcomes with respect to maintenance of sinus rhythm and symptomatic burden will be essential to assessing the overall efficacy of this novel technology.

Funding Acknowledgement

Type of funding sources: None.

Understanding HCP views about delivering a rehabilitation programme for people living with atrial fibrillation

Background

People living with Atrial Fibrillation (AF) can experience symptoms such as palpitation, dyspnea, fatigue and dizziness which lead to reduced physical activity levels and quality of life [1,2]. Current management of AF mainly focus on pharmacological treatments and invasive procedures, while no routine prescription of exercise or rehabilitation programme is offered.

Purpose

To assess the views and opinions of healthcare professionals about delivering a tailored exercise/cardiac rehabilitation programme to people living with AF, and to explore the barriers in referral to this programme.

Methods

A cross-sectional survey was conducted online between April and September 2021 for healthcare professionals who are involved in the care for adults with AF in UK. A range of professions were targeted, including general practitioners, cardiac physicians, physiotherapists and nurses. The survey comprised twelve questions designed to explore healthcare professional views about rehabilitation programmes for adults with AF, factors influencing their decision to recommend rehabilitation and barriers to the referral process.

Results

Overall, n=209 participants responded from a wide range of disciplines (57% female, 43% specialist arrhythmia nurses). The majority of participants agreed that a rehabilitation programme would be beneficial to support patients to perform daily activities (127, 61%), with n=123, 58% agreeing that rehabilitation programme would be beneficial in reducing breathlessness and would reduce other symptoms such as palpitation (108, 52%).

Nearly all the healthcare professional (n=206/99%) suggested that a tailored programme should include information about AF (206, 99%), weight management and symptom management (n=197, 94%) aside from exercise. The factors that strongly influence their decision to refer to a rehabilitation programme included patients with low physical activity levels (n=166, 80%) and low exercise tolerance (n=157, 76%). The main barrier in referring to the programme was transportation problems (n=128, 62%) (Figure 1). The majority reported that home based programme would be the best way to deliver the programme (166, 79%) (Figure 2).

Conclusions

The responses indicate the enthusiasm for a programme targeting people with AF, poor activity levels was the main reason for referral.

Funding Acknowledgement

Type of funding sources: None.

Short term outcomes of distal (ventricular) His bundle pacing: A single centre retrospective study

Funding Acknowledgements

Type of funding sources: None.

Introduction

Chronic right ventricular apical pacing can lead to pacing induced cardiomyopathy in a significant proportion of patients. Conduction system pacing may restore more physiological activation of the heart, and has recently been shown to have favourable outcomes in clinical trials. However there remains concern regarding the long-term outcomes due to lead displacement and high pacing thresholds. The most widely used technique in current practice is to pace the His bundle proximal to the tricuspid valve. Distal His bundle pacing has a number of advantages over proximal His pacing, including, lower capture thresholds, a more stable lead position, less far field atrial sensing and better spacing from the AV node in case ablation of this is required for AF rate control. Despite these, outcomes of distal His bundle pacing from the ventricular aspect are less well defined.

Methods

We performed a retrospective review of patients who underwent conduction system pacing between January 2020 and October 2021 at our centre. During this period all procedures were performed employing a distal His bundle pacing approach with the lead placed on the ventricular aspect of the tricuspid annulus. Data was collected at implant, follow-up at 1 month and then every 6 months.

Results

Out of 35 patients, 33 underwent successful His bundle pacing (acute success rate of 94%), 1 patient had left bundle branch pacing and another patient had an unsuccessful procedure. Mean age was 74 years, median LVEF 45% and median pre-implant QRS was 108ms. 80% of the cohort had a history of AF. The indications for pacing were as follows: AF - for pace & ablate (60%); high grade AV block with narrow QRS and mild LVSD (17%); failed LV lead (14%); and other 9%. Mean procedure duration and fluoroscopy time were 78 minutes and 12.05 minutes, respectively. Median threshold at implant was 1.00V (IQR 0.719V). Selective His bundle pacing was achieved in 60% and non-selective in 34%. Mean follow-up duration was 150 days with median threshold at last f/up of 0.75V (IQR 0.750V). There were no acute procedural complications. 1 patient had a significant rise in threshold at follow-up and therefore required upgrade to CRT-P.

Discussion

Our data shows that distal His bundle pacing is a safe and effective technique for conduction system pacing. Thresholds appear stable at follow-up and failure rate was found to be comparable to biventricular pacing. We noted an initial learning curve for both implanter and physiologists with relatively poorer outcomes for the earlier cases. Longer term follow-up is ongoing, including functional assessment and follow-up to assess for remodelling with echocardiography. Prospective randomised trials are needed to compare conduction system pacing vs RV pacing in AF patients with HFpEF or mild LVSD undergoing AVN ablation, and vs biventricular pacing in the severe LVSD population.

Short term outcome of distal (ventricular) His bundle pacing and atrioventricular node ablation in patients with symptomatic atrial fibrillation - Refining the concept

Funding Acknowledgements

Type of funding sources: None.

Introduction

Many patients with atrial fibrillation (AF) do not benefit from rhythm control due to failed catheter ablation, advanced left atrial disease and comorbidities. "Pace and AV node (AVN) ablation" strategy is often adopted for rate control but with a substantial risk of pacing-induced cardiomyopathy. His bundle pacing (HBP) enables physiological biventricular activation through the His Purkinje conduction system. However, the proximity of the HBP lead to the site of AV node ablation may potentially compromise lead integrity in patients who undergo conventional HBP and AVN ablation. Therefore, we have modified HBP by placing the HBP lead distally at the ventricular side of the His bundle (D-HBP) before AVN ablation in patients with symptomatic AF. All patients had a backup RV lead.

Method

Patients who had D-HBP as part of a "Pace and AVN ablation" strategy were retrospectively analysed. Implant and device clinic follow-up data were collected and analysed.

Result

Twenty-one patients who had "pace and AVN ablation strategy" with D-HBP between 26th February 2020 and 3rd November 2021 were included. They had a mean age of 75 ± 1.4 years (mean ± SEM), NYHA class of 2.1 ± 0.2, QRS duration of 106 ± 5.3ms and 50% had at least moderately impaired LV systolic function. Seventeen patients (81%) had narrow QRS duration. D-HBP was successful in twenty of twenty-one patients (95%). At D-HBP implant, the mean acute threshold of the HBP lead was 0.96 ± 0.12V at 0.5 ± 0.05ms and the mean HBP lead impedance was 548.1 ± 29.5Ω. Selective HBP pacing was observed in thirteen of twenty patients. The mean QRS duration of HBP paced beats was 104.5 ± 4.7ms. Failure to capture the His bundle was observed in one patient. AVN ablation was performed on the same day after D-HBP in eleven patients and as a subsequent procedure in nine patients. The mean duration of procedure and fluoroscopy for D-HBP were 77.4 ± 4.6 minutes and 11.9 ± 1.4 minutes respectively. There were no acute procedural complications with no lead damage, displacement or lead perforation observed. The median follow-up period was 207 days. The mean D-HBP lead threshold following AVN ablation was 1.1 ± 0.2 V at 0.6 ± 0.07 ms and the mean lead impedance was 433.8 ± 20.7Ω, which were similar to before AVN ablation. One patient was reprogrammed with RV pacing only for elevated HBP lead threshold after AVN ablation to 4.2 V at 1ms. The mean D-HBP percentage was 92.3 ± 6.6% and the mean estimated battery longevity of the pacemaker was 7.9 ± 0.6 years at the last follow up. There was improvement in heart failure symptoms in eight patients from previously symptomatic to NYHA class I following D-HBP and AVN ablation.

Conclusion

D-HBP appear to be safe with potentially more favourable lead parameters than conventional proximal HBP in patients with symptomatic AF offered "Pace and AVN ablation" strategy.

Hybrid machine learning to localize atrial flutter substrates using the surface 12-lead electrocardiogram

Aims

Atrial flutter (AFlut) is a common re-entrant atrial tachycardia driven by self-sustainable mechanisms that cause excitations to propagate along pathways different from sinus rhythm. Intra-cardiac electrophysiological mapping and catheter ablation are often performed without detailed prior knowledge of the mechanism perpetuating AFlut, likely prolonging the procedure time of these invasive interventions. We sought to discriminate the AFlut location [cavotricuspid isthmus-dependent (CTI), peri-mitral, and other left atrium (LA) AFlut classes] with a machine learning-based algorithm using only the non-invasive signals from the 12-lead electrocardiogram (ECG).

Methods and results

Hybrid 12-lead ECG dataset of 1769 signals was used (1424 in silico ECGs, and 345 clinical ECGs from 115 patients—three different ECG segments over time were extracted from each patient corresponding to single AFlut cycles). Seventy-seven features were extracted. A decision tree classifier with a hold-out classification approach was trained, validated, and tested on the dataset randomly split after selecting the most informative features. The clinical test set comprised 38 patients (114 clinical ECGs). The classifier yielded 76.3% accuracy on the clinical test set with a sensitivity of 89.7%, 75.0%, and 64.1% and a positive predictive value of 71.4%, 75.0%, and 86.2% for CTI, peri-mitral, and other LA class, respectively. Considering majority vote of the three segments taken from each patient, the CTI class was correctly classified at 92%.

Conclusion

Our results show that a machine learning classifier relying only on non-invasive signals can potentially identify the location of AFlut mechanisms. This method could aid in planning and tailoring patient-specific AFlut treatments.

128Non-invasive 3D mapping of earliest activation of premature ventricular complexes originating from intracardiac structures to guide catheter ablation

Funding Acknowledgements

Research funding from Catheter Precision, Inc.

Introduction

Catheter ablation for ventricular arrhythmias such as premature ventricular complexes and ventricular tachycardia is an established management approach.  Non-invasive mapping to localise the earliest activation (site of origin) on the myocardium may help guide ablation.  Established ECGi methods using the inverse solution to reconstruct epicardial electrograms are unable to accurately locate arrhythmias from the endocardium or from intracardiac structures.  VIVO™ (Catheter Precision) is a novel vectorcardiography based 3D mapping system that may be able to localise arrhythmias from any part of the ventricle.

Methods

We reviewed our initial experience utilising this mapping system to guide catheter ablation of ventricular ectopics from the inter-ventricular septum, coronary cusp or papillary muscle.  A patient-specific 3D heart and torso model was created using semi-automated segmentation of MRI or CT scan images.  A 3D topographic image of the patient’s torso was taken to accurately position surface ECG electrode locations onto the 3D heart-torso model.  An ECG of the PVC was imported from LabSystemPro (Bard) into VIVO™ for analysis prior to ablation.  The result was then compared with the site of earliest activation identified using invasive electro-anatomical (EA) mapping.

Results

VIVO™ was used in 12 cases where the PVC was localised to an intracardiac structure – six papillary muscle, four to the septum and two from the coronary cusp.  VIVO™ was able to accurately localise the earliest activation site when compared to the invasive map in 5/6 papillary muscle cases, 3/4 septal cases and 2/2 coronary cusp cases.  Ablation was acutely successful in all cases.  One additional patient had a PVC localised non-invasively to the postero-medial papillary muscle, however an invasive 3D electro-anatomical map or ablation was not performed.

In three cases we were able to merge the 3D geometry of the non-invasive map from VIVO™ into the Carto™ system to guide mapping and ablation in real time (see figure).

Conclusion

Our experience shows promising results for accurate non-invasive localisation of ventricular arrhythmias originating from intracardiac structures.  Non-invasive localisation is of particular value in cases where the arrhythmia is infrequent, difficult to induce or poorly tolerated haemodynamically.  The two cases where PVC localisation was inaccurate were performed using an older version of the software. With recent refinements, localisation is anticipated to be improved further.

We also present the first experience of combining the VIVO™ geometry with the real-time invasive EA map.  This has potential to significantly speed up mapping time and reduce the need for expensive multi-polar catheters by allowing the operator to see their target in real time 3D.  Further work is ongoing to validate the accuracy of VIVO™ prospectively and quantitatively.

Abstract Figure. VIVO map merged with Carto LV geometry

P439Could regional electrogram desynchronization identified using mean phase coherence be potential ablation targets in persistent atrial fibrillation?

Funding Acknowledgements

This work was supported by the NIHR Leicester Biomedical Research Centre. XL was funded by MRC(MR/S037306/1) and BHF (PG/18/33/33780)

Background

It remains controversial as to whether rotors detected using phase mapping during persistent atrial fibrillation (persAF) represent main drivers of the underlying mechanism as others found rotors to be located near line of conduction block. Regional electrogram desynchronization (RED) has been suggested as successful targets for persAF ablation, but automatic tools and quantitative measures are lacking.

Purpose

We aim to use mean phase coherence (MPC) to automatically identify RED regions during persAF. This method was compared with phase singularity density (PSD) maps.

Methods

Patients undergoing left atrial (LA) persAF ablation were enrolled (n = 10). 2048-channel virtual electrograms (VEGMs) were collected from each patient using non-contact mapping (St Jude Velocity System, Ensite Array) for 10 seconds.  To remove far field ventricular activities, QRS onset and T wave end locations were detected from ECG lead I (Figure 1A) and only the VEGM segments from T end to QRS onset were included in the analysis. VEGMs were reconstructed using sinusoidal wavelets fitting and the phase of VEGMs determined using Hilbert transform. Phase singularities (PS) were detected using the topological charge method and repetitive PSD maps were generated. RED was defined as the average of MPC of each node against direct neighbouring nodes on the 3D mesh (Figure 1A-B). Linear regression analysis was used to compare the average MPC vs. PSD and vs. the standard deviation of MPC (MPC_SD).

Results

A total of 221,184 VEGM segments were analysed with mean duration of 364.2 milliseconds.  MPC has shown the ability to quantify the level of synchronisation between VEGMs (Figure 1B). Inverse correlation was found between PSD and average MPC values for all 10 patients (p < 0.0001, Figure 1C). Average MPC and MPC_SD were found to be inversely correlated (p < 0.0001, Figure 1C). Spatially, similar graphic patterns can be found from LA MPC maps and PSD maps for all patients (Figure 1D).

Conclusion

We have proposed a method to quantify the level of synchronisation between VEGMs. Phase density mapping showed a considerable agreement with RED regions reflecting regional conducting delays, which supports the previous finding where rotors found at conduction block. Inverse correlation between local average MPC and MPC_SD suggests that conduction delays of the identified regions are not heterogenous, posing directional preferences. Rather than solely looking for rotational activities, this method could identify comprehensive RED regions, which may also explain the conflicting results from different studies targeting rotational activities, where incomplete subsets of RED regions could have been targeted. Atrial RED regions can easily be identified with simultaneously collected electrograms from multi-polar catheters and should be targeted in future persAF studies.

Abstract Figure 1

P1113Patchy localisation of late gadolinium enhancement associated with ventricular arrhythmia in dilated cardiomyopathy

Funding Acknowledgements

None

Introduction

Myocardial fibrosis detected using late gadolinium enhancement(LGE) on cardiac magnetic resonance(CMR) imaging holds prognostic value in dilated cardiomyopathy(DCM). Recent reports have demonstrated the localisation of LGE to be promising predictors of ventricular arrhythmic (VA).Aim: To determine the localisation of LGE associated with high risk of VA in DCM patients. Methods: Retrospective review of consecutive DCM patients(n = 85) implanted with an implantable cardioverter defibrillator(ICD) at a single tertiary centre between 2011-2018. All patients with insufficient follow-up data, cardiac channelopathies, primary valvular pathology and congenital heart disease were excluded from analysis(n = 11). Details of VA occurrence were obtained from medical and pacing notes. VA was defined as VA causing haemodynamic compromise or appropriate device therapy (anti-tachycardia pacing/shock). Localisation of LGE was defined as midwall, patchy, subepicardial or transmural. Left ventricular ejection fraction(LVEF) <35% was defined as severely impaired function. Results:74 DCM patients implanted with an ICD were identified for analysis; LGE was observed in 18(60%) VA and 29(66%) non-VA patients(p = 0.6). There was no observed difference in mean age for patients with and without LGE (68 ± 10 vs. 65 ± 10 years,p = 0.07). A significant difference was seen between localisation and VA (p = 0.04), with patchy LGE demonstrating a higher arrhythmic risk(p = 0.005). There was no association between LVEF and LGE(p = 0.2) however, a significant difference was seen in LVEF and arrhythmic risk, with a more severely impaired LV function seen in patients without VA(p = 0.01). Conclusion:This study has demonstrated a patchy LGE localisation to be strongly associated with ventricular arrhythmia in DCM. Whilst this is a valuable tool in risk stratification, a prospective study with a larger population is required to confirm the validity of this finding. Moreover, an additional method will need to be considered to identify high risk patients without LGE.

Ventricular Arrhythmia (n = 30) No Ventricular Arrhythmia (n = 44) P Value Male(%) 20(67%) 24(55%) p = 0.29 Age(Mean ± SD) 65 ± 12 65 ± 10 p = 0.36 LGE Midwall 10(56%) 24(83%) p = 0.04 Subepicardial 1(5.5%) 2(7%) p = 0.85 Transmural 1(5.5%) 2(7%) p = 0.85 Patchy 6(33%) 1(3%) p = 0.005 LVEF <35% 23(77%) 42(95%) p = 0.01

LifeMap: towards the development of a new technology in sudden cardiac death risk stratification for clinical use

Sudden cardiac death (SCD) is a major cause of mortality presenting a significant unmet clinical need. Patients at risk of SCD are implanted with implantable cardioverter-defibrillators (ICDs) according to international guidelines based on clinical trial evidence. Implantable cardioverter-defibrillators are not inexpensive and not without problem in terms of inappropriate shocks and infection risk. Also, only a minority of patients implanted with the ICD ever use the device during its battery lifetime highlighting the fact that methods used for SCD risk stratification are inadequate. Better ways of predicting who is at risk of SCD are needed. In addition, there is no effective prevention due to the lack of understanding of the electrical mechanisms underlying SCD. Our group has been investigating the electrophysiological basis of ventricular fibrillation and have successfully applied our preclinical findings to translational studies in patients with ischaemic cardiomyopathy. We have developed two ECG markers which have been shown to be strong predictors of ventricular arrhythmias and SCD. Ongoing clinical studies are being carried out including a multicentre UK study to consolidate the evidence base. They are being incorporated into the technology, LifeMap, with the aim to develop a successful clinical tool for the assessment of SCD risk. We hereby present the scientific data leading to the technology and the development to date. The information provided here was presented at the European Heart Rhythm Association (EHRA) Europace/Cardiostim conference at which LifeMap won the EHRA Inventors Award 2016.

European survey on efficacy and safety of duty-cycled radiofrequency ablation for atrial fibrillation

AIMS

Duty-cycled radiofrequency ablation (RFA) has been used for atrial fibrillation (AF) for around 5 years, but large-scale data are scarce. The purpose of this survey was to report the outcome of the technique.

METHODS AND RESULTS

A survey was conducted among 20 centres from seven European countries including 2748 patients (2128 with paroxysmal and 620 with persistent AF). In paroxysmal AF an overall success rate of 82% [median 80%, interquartile range (IQR) 74-90%], a first procedure success rate of 72% [median 74% (IQR 59-83%)], and a success of antiarrhythmic medication of 59% [median 60% (IQR 39-72%)] was reported. In persistent AF, success rates were significantly lower with 70% [median 74% (IQR 60-92%)]; P = 0.05) as well as the first procedure success rate of 58% [median 55% (IQR 47-81%)]; P = 0.001). The overall success rate was similar among higher and lower volume centres and were not dependent on the duration of experience with duty-cycled RFA (r = -0.08, P = 0.72). Complications were observed in 108 (3.9%) patients, including 31 (1.1%) with symptomatic transient ischaemic attack or stroke, which had the same incidence in paroxysmal and persistent AF (1.1 vs. 1.1%) and was unrelated to the case load (r = 0.24, P = 0.15), bridging anticoagulation to low molecular heparin, routine administration of heparin over the long sheath, whether a transoesophageal echocardiogram was performed in every patient or not and average procedure times.

CONCLUSION

Duty-cycled RFA has a self-reported success and complication rate similar to conventional RFA. After technical modifications a prospective registry with controlled data monitoring should be conducted to assess outcome.

Variability in the manifestation of pre-excited atrial fibrillation: its quantification, theoretical origin, and diagnostic potential

BACKGROUND

Irregular broad complex tachycardia (BCT) may be due to atrial fibrillation (AF) occurring in the presence of ventricular pre-excitation (pre-excited AF) or bundle branch block (BBB-AF). While irregularity is a defining characteristic of AF, it is a common subjective impression that greater variability in manifestation exists for pre-excited AF than BBB-AF. This difference can potentially be exploited for distinguishing the two conditions if some means can be found to quantify it.

METHODS

For each of 75 ECGs showing irregular BCT (41 pre-excited AF and 34 BBB-AF), a random sample of 10 distinct QRS complexes were selected for quantitative measurement of variability in manifestation, which included the standard deviation (SD) of the width, the SD of the axis, and the coefficient of variation (CV) of the amplitude of the QRS complex.

RESULTS

Pre-excited AF showed statistically significantly greater values than BBB-AF with respect to these measures, and receiver-operating characteristic curves showed that these differences could be useful for their discrimination. For the SD of QRS width, a cut-off value of 8 ms appeared optimal (sensitivity 1.00 and specificity 0.79). For the SD of QRS axis, a cut-off value of 2.5 degrees appeared optimal (sensitivity 0.84 and specificity 0.56). For the CV of QRS amplitude, a cut-off value of 0.10 appeared optimal (sensitivity 0.82 and specificity 0.76).

CONCLUSIONS

Pre-excited AF demonstrated greater variability than BBB-AF in manifestation. The measures of variability developed can potentially be useful for diagnosing irregular BCT in practice, especially in the context of automated computer-aided diagnosis.

The midlands trial of empirical amiodarone versus electrophysiology-guided interventions and implantable cardioverter-defibrillators (MAVERIC): a multi-centre prospective randomised clinical trial on the secondary prevention of sudden cardiac death

AIMS

MAVERIC was a randomised clinical trial designed to test the possibility of prospectively identifying patients who would benefit most from the implantable cardioverter-defibrillator (ICD) by electrophysiology (EP) study in the context of secondary prevention of sudden cardiac death (SCD) through comparing EP-guided interventions (anti-arrhythmic drugs, coronary revascularization, and ICD) against empirical amiodarone therapy.

METHODS

Two hundred and fourteen survivors of sustained ventricular tachycardia (VT), ventricular fibrillation (VF) or SCD were randomized to either treatment strategy, pre-stratified for haemodynamic status at index event, and followed up for a median of 5 years.

RESULTS

Of the 106 amiodarone arm patients, 89 (84%) received the drug and 5 (5%) received an ICD after crossing over. Of the 108 EP arm patients, 31 (29%) received an ICD, 46 (43%) received anti-arrhythmic drugs only (mainly amiodarone or sotalol) and 18 (17%) received coronary revascularization but no ICD. No significant differences in survival or arrhythmia recurrence existed between the two treatment arms after 6 years. However, ICD recipients had a lower mortality than non-ICD recipients, regardless of allocated treatment (hazard ratio=0.54, p=0.0391).

CONCLUSIONS

Prospective selection of patients to receive the ICD by EP study did not improve survival compared with empirical amiodarone therapy among survivors of VT, VF or SCD, whereas ICD implantation improved survival regardless of allocated treatment. On this basis, routine EP study has no role in the management of such patients, who should be offered empirical ICD therapy according to the results of other secondary prevention ICD trials.

Visual illusions created by survival curves and the need to avoid potential misinterpretation

Randomized clinical trials play an increasingly important role in guiding management decisions, and survival curves are the most popular means for summarizing and depicting the results of a clinical trial. However, survival curves may create certain "visual illusions" that can be misinterpreted by the unwary, with potentially adverse effects on patient care. The authors provide a brief outline of the theoretical background of survival curves and explain the origin of the most common visual illusions. Statisticians need to be aware of such potential for misinterpretation of clinical trial data in order to safeguard clinicians against drawing undue inferences and applying them to actual practice.

Comparison of two diagnostic algorithms for regular broad complex tachycardia by decision theory analysis

Sensitivity and specificity are two inversely related properties of a diagnostic test and it is often practically infeasible to secure a high value for both simultaneously. Decision theory analysis shows that the utility of a diagnostic test depends not only on its sensitivity and specificity but also on the prevalence of the intended target disorder: when prevalence is low, a high specificity is more important than a high sensitivity, whereas when prevalence is high, a high sensitivity is more important than a high specificity. The significance of this principle is illustrated by two popular algorithms for the electrocardiographic diagnosis of regular broad complex tachycardia (BCT), of which the two main differential diagnoses are ventricular tachycardia (VT) and supraventricular tachycardia with aberrant conduction (SVTAG). Brugada et al. focused on criteria highly specific for VT and used them to build a four-step algorithm. In contrast, Griffith et al. first selected criteria highly sensitive for VT and then criteria highly specific for VT to build a simple two-step algorithm. It can be objectively demonstrated that the Griffith algorithm is more efficient and effective than the Brugada algorithm in terms of clinching the final diagnosis and improving overall diagnostic accuracy. The main reason for this is that VT is more common than SVTAC as the cause of regular BCT, and the Griffith algorithm adhered to the aforementioned principle governing the choice between sensitivity and specificity according to prevalence in its design. The Griffith algorithm also embodies an additional important principle, namely, it is easier and more efficient to choose alternatively between criteria highly specific and highly sensitive for the intended target disorder than concentrating on just one or the other in designing a multiple-step sequential diagnostic algorithm.

Effects of direct sympathetic and vagus nerve stimulation on the physiology of the whole heart--a novel model of isolated Langendorff perfused rabbit heart with intact dual autonomic innervation

A novel isolated Langendorff perfused rabbit heart preparation with intact dual autonomic innervation is described. This preparation allows the study of the effects of direct sympathetic and vagus nerve stimulation on the physiology of the whole heart. These hearts (n = 10) had baseline heart rates of 146 +/- 2 beats x min(-1) which could be increased to 240 +/- 11 beats x min(-1) by sympathetic stimulation (15 Hz) and decreased to 74 +/- 11 beats x min(-1) by stimulation of the vagus nerve (right vagus, 7 Hz). This model has the advantage of isolated preparations, with the absence of influence from circulating hormones and haemodynamic reflexes, and also that of in vivo preparations where direct nerve stimulation is possible without the need to use pharmacological agents. Data are presented characterising the preparation with respect to the effects of autonomic nerve stimulation on intrinsic heart rate and atrioventricular conduction at different stimulation frequencies. We show that stimulation of the right and left vagus nerve have differential effects on heart rate and atrioventricular conduction.

Electrocardiographic criteria for diagnosis of irregular broad complex tachycardia with a high sensitivity for preexcited atrial fibrillation

AF may appear as an irregular broad complex tachycardia (BCT) if atrioventricular conduction occurs via an accessory pathway (preexcited AF) or if bundle branch block (BBB), preexistent or rate related, exists in the His-Purkinje system (BBB-AF). While BBB-AF is relatively benign, preexcited AF may herald sudden cardiac death. Hence it is important that the two conditions can be reliably distinguished. Yet, there is no preexistent algorithms for this purpose. Griffith et al. previously proposed a simple algorithm for a similar problem, that of distinguishing the two differential diagnoses for regular BCT: VT and SVT with BBB, on the basis that unless the QRS morphologies in V1 and V6 are absolutely typical of BBB, VT will be diagnosed. The authors propose an extrapolation of this principle to irregular BCT by stating that, unless the QRS morphologies in V1 and V6 are absolutely typical of BBB, preexcited AF will be diagnosed. Seventy-five ECGs showing irregular BCT (41 preexcited AF and 34 BBB-AF) were shown to two fellows in electrophysiology who were given no other information and were instructed to diagnose preexcited AF unless the QRS morphology pattern was typical of BBB. Observer 1 achieved a sensitivity of 100% (41/41) and a specificity of 79% (27/34), while observer 2 achieved a sensitivity of 100% and a specificity of 85% (29/34). By QRS morphology pattern, an average sensitivity of 100% and specificity of 82% were achieved for the diagnosis of irregular BCT. The algorithm is simple and easy to implement and recommended for clinical use.

The Bayesian approach improves the electrocardiographic diagnosis of broad complex tachycardia

Despite numerous attempts at devising algorithms for diagnosing broad complex tachycardia (BCT) on the basis of the electrocardiogram (ECG), misdiagnosis is still common. The reason for this may lie with difficulty in implementing existent algorithms in practice, due to imperfect ascertainment of ECG features within them. An attempt was made to approach the problem afresh with the Bayesian inference by the construction of a diagnostic algorithm centered around the likelihood ratio (LR). Previously studied ECG features most effective in discriminating ventricular tachycardia (VT) from supraventricular tachycardia with aberrant conduction (SVTAC), according to their LR values, were selected for inclusion into a Bayesian diagnostic algorithm. A test set of 244 BCT ECGs was assembled and shown to three independent observers who were blinded to the diagnoses made at electrophysiological study. Their diagnostic accuracy by the Bayesian algorithm was compared against that by clinical judgement with the diagnoses from EPS as the criterial standard. Clinical judgement correctly diagnosed 35% of SVTAC, 85% of VT, and 47% of fascicular tachycardia. In comparison, by the Bayesian algorithm devised, 52% of SVTAC, 95% of VT, and 97% of fascicular tachycardia were correctly diagnosed. The Bayesian algorithm devised has proved to be superior to the clinical judgement of the observers who participated in this study, and theoretically will obviate the problem of imperfect ascertainment of ECG features. Hence, it holds the promise for being an effective tool for routine use in clinical practice.

Temperature-sensitive focal atrial tachycardia in the left atrium

Temperature sensitivity has not been reported in focal atrial tachycardia. We describe a patient with a left atrial tachycardia whose tachycardia rate was affected by hot and cold drinks. The effects were still evident after autonomic blockade. The arrhythmia focus was located at the entrance of the left upper pulmonary vein. Radiofrequency ablation was carried out, which proved to be difficult, but it was successful after several applications of energy, suggesting an epicardial location of the arrhythmia focus. Sensitivity of atrial tachycardia rate to the temperature of food or drink ingested suggests a left atrial focus with a posterior and possibly epicardial location.

A new ECG sign of an accessory pathway in sinus rhythm: pseudo partial right bundle branch block

It is clinically important to be able to detect the presence of an accessory pathway, as pre-excited atrial fibrillation is a well recognised cause of sudden cardiac death, for which there is a potential "cure" in the form of radiofrequency ablation of the pathway. The classic manifestations such as a shortened PR interval or delta waves may not always be present. In certain patients a pseudo partial right bundle block pattern-that is, an rSr' complex in lead V1- may be the sole manifestation of a left sided accessory pathway. An electrophysiological mechanism is proposed for this pattern and it is suggested that this pattern may be used as a new ECG sign for diagnosing an accessory pathway in sinus rhythm.

Imaging of adenosine bolus transit following intravenous administration: insights into antiarrhythmic efficacy

OBJECTIVE

To study the effects of the site of intravenous injection of adenosine and to assess the site of action of adenosine in the heart by correlating cardiac effects with bolus transit.

METHODS

Ten patients undergoing routine technetium (Tc-99m) gated blood pool ventriculography consented to the coadministration of intravenous adenosine. The dose of adenosine required to produce heart block during sinus rhythm was determined following antecubital vein administration. This dose (6-18 mg) was mixed with Tc-99m and given first into the same antecubital vein (proximal injection) and then repeated into a hand vein (distal injection). The ECG was recorded and the transit of the bolus was imaged using a gamma camera.

RESULTS

Heart block occurred in all 10 patients (second degree in seven, first degree in three) at (mean (SEM)) 17.5 (1.0) seconds after the proximal injection of adenosine. Distal injection produced heart block in six patients (second degree in two, first degree in four) at 21.9 (4.4) seconds (p < 0.01). In eight of 10 patients the electrophysiological effects were less with distal injection. The onset of heart block was close to the time of peak bolus Tc-99m activity in the left ventricle. Peak bolus activity was delayed (by about three seconds) and the duration of bolus activity in the left ventricle was increased with distal injection compared with proximal injection, at 17.2 (4.2) v 9.2 (3.1) seconds, p < 0.01.

CONCLUSIONS

The lesser electrophysiological effects of adenosine following distal intravenous injections were associated with delay in transit time and dispersion of the bolus. The correlation of adenosine induced heart block with bolus activity in the left heart indicated dependence on coronary arterial delivery of adenosine to the atrioventricular node.

Non-uniform prolongation of intracellular Ca2+ transients recorded from the epicardial surface of isolated hearts from rabbits with heart failure

OBJECTIVES

To study the time course of Ca2+ transients recorded from the left ventricular epicardial surface of isolated hearts from rabbits with heart failure and to correlate the results with mechanical function.

METHODS

Heart failure was induced in the rabbit 8 weeks after coronary ligation (n = 17) with 13 controls. Echocardiography was used to assess in vivo left ventricular dysfunction. The fluorescent indicator Indo-1 was loaded into isolated Langendorff-perfused hearts and Ca2+ transients were recorded from 15 sites over the left ventricular epicardial surface using a single core light guide. The time course of the Ca2+ transients was analysed and the duration measured and correlated with in vitro mechanical function.

RESULTS

Significant mechanical dysfunction was produced in this model of heart failure. The mean duration of the Ca2+ transients obtained from failing hearts was prolonged (156.2 +/- 3.2 ms) when compared to controls (124.9 +/- 2.6 ms, P < 0.001). Delayed relaxation as measured by the maximum rate of intraventricular pressure decay was significantly correlated with the prolonged Ca2+ transients (r = -0.63, P < 0.001). In addition, there was increased variation of the Ca2+ transient duration in the failing hearts.

CONCLUSIONS

Coronary artery ligation-induced heart failure is associated with changes in the surviving myocardium which result in a non-uniform prolongation of Ca2+ transient duration. This suggests that there is a regional heterogeneity to the abnormal intracellular Ca2+ handling in heart failure.

When is it futile for ambulance personnel to initiate cardiopulmonary resuscitation?

OBJECTIVE

To determine whether patients with unexpected prehospital cardiac arrest could be identified in whom ambulance resuscitation attempts would be futile.

DESIGN

Review of ambulance and hospital records; detailed review of automated external defibrillator rhythm strips of patients in whom no shock was advised.

SETTING

Scottish Ambulance Service; all cardiopulmonary resuscitation attempts after cardiorespiratory arrest during 1988-94 included in the Heartstart Scotland database.

SUBJECT

414 cardiorespiratory arrest patients with no pulse or breathing on arrival of ambulance personnel, no bystander cardiopulmonary resuscitation performed, and more than 15 minutes from time of arrest to arrival of ambulance. Patients were stratified into those with "shockable" and "non-shockable" rhythms.

MAIN OUTCOME MEASURES

Return of spontaneous circulation, or survival to reach hospital alive, or survival to discharge, or all three.

RESULTS

No patient with a non-shockable rhythm who met the entry criteria for analysis survived a resuscitation attempt. Review of the defibrillator rhythm strips of these patients failed to find any case in which the tracing was deemed compatible with survival.

CONCLUSION

On the basis that it would be inappropriate to initiate vigorous resuscitation in patients who can be identified as "dead" and beyond help an algorithm was prepared to guide ambulance personnel.