How good is operator opinion at predicting high ventricular pacing burden among patients receiving device therapy for bradycardia?

Funding Acknowledgements

Type of funding sources: None.

Introduction

Current guidelines indicate that pacing methods that maintain physiologic ventricular activation (biventricular pacing or His-bundle pacing) should be chosen over right ventricular pacing (Vp) among patients with EF 36-50% who are expected to Vp >40% of the time. There are no guidelines to help predict which patients will receive a high burden of Vp and this is left to operator

opinion. We sought to ascertain whether operator opinion is an accurate predictor of high burden of Vp.

Methods

This was a single-centre single-blinded observational study of patients who received pacemaker implant for treatment of bradycardia between April 2015 and 2019 and had at least 12 month follow-up data on record. Patients’ demographic, clinical, electrocardiographic and echocardiographic data were reviewed in a blinded fashion by a senior implanting physician, who estimated whether the Vp at 12 months would exceed 40%. The Vp at approximately 12 months was obtained from the pacing records and compared with the prediction.

Results

Some 982 patients underwent pacemaker implantation during the study period, 698 for conduction system disease (CSD), 267 for sinus node disease (SND) and 17 for other conditions. Overall, 856 had valid follow-up data. Of these, 543 (63.4%) were predicted to Vp >40% , and 527(61.6%) were documented as having Vp >40%. The sensitivity and specificity of operator prediction were 93.2% and 84.2%, with positive and negative predictive values of 90.4% and 88.5%. Table 1 illustrates analyses of different populations by clinical parameter. In sub-group analysis, complete heart block and PR > 300ms were significant factors for accurate prediction of Vp > 40%, however clinical features, such as syncope, were poor discriminators.

Conclusion

In this single-centre study, among patients receiving pacemaker implant for treatment of bradycardia, operator prediction of the burden of Vp >40% has an acceptable degree of accuracy. Sub-group analysis suggests that certain clinical parameters could make this prediction easier. Table 1. Comparison of operator opinion SND CSD CHB SND+PR < 160 PR > 300 Syncope Non-syncope n 698 267 216 84 60 409 344 Sensitivity 44.4% 97.7% 100% 6.3% 100% 86.4% 87.9% Specificity 98.3% 62.0% 45.2% 97.1% 0%* 89.9% 79.6% PPV 87.0% 90.6% 91.6% 33.3% 98.3% 94.2% 92.2% NPV 87.9% 87.9% 100% 81.5% - 77.6% 70.5% * only 1 patient did not RV pace >40% - this was not predicted. SND – sinus node disease; CSD – conduction system disease; CHB – complete heart block, PPV – positive predictive value; NPV – negative predictive value

Ablation Index-guided 50W ablation for left atrial posterior wall isolation compared with lower powers: feasibility and lesion level analysis

Funding Acknowledgements

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Groupe de Rythmologie de la Société Française de Rythmologie

Background 

Posterior Wall Isolation (PWI) is increasingly performed for Atrial Fibrillation (AF). The use of Ablation Index (AI)-guided 50W ablation for PWI has not been described, nor the interplay between ablation parameters at this power when compared to lower powers. 

Methods 

40 consecutive AF patients (26 males, 65.5 ± 10.0 years. 95% non-paroxysmal AF) underwent PWI following pulmonary vein isolation. A roof line and floor line were created with point-by-point ablation, targeting a contact force (CF) of 10-30g, AI 550-600 on the roof and 400-450 on the floor, and inter-tag distance of <6mm. 35-40W powers were used for the first 20 patients, and 50W used for the next 20. Generator impedance was monitored in real time for each lesion. Ablation inside the box was delivered in case of failure of first pass isolation (FPI). All VisiTags (n = 959) were analyzed retrospectively. 

Results 

PWI was successful in 19(95%) of the 35-40W group and in all 20 patients in the 50W group, with FPI seen in 8(40%) and 10(50%) respectively, p = 0.53. The mean CF and number of RF applications on the roof. floor and inside the box were similar between the two groups. Ablation time per lesion (10.4 [8.8-12.5]sec) and total ablation time per patient (3.84[3.34-4.66] min) were shorter in the 50W group as compared to 35-40W (13.0 [11.6-16.2] sec and 5.86 [4.23-7.73] min respectively), p < 0.005. The mean AI and Impedance Drop were larger in the 50W group (Table). There was no steam pop observed in any of the 959 radiofrequency applications. 

Conclusion 

Ablation Index guided 50W ablation has a very high success rate for posterior wall isolation with shorter ablation times and higher impedance drop compared to conventional powers. Steam pops may be avoidable by targeting CF < 30g, and by monitoring impedance in real-time. 50W Group(N = 458) 35-40W Group(N = 501) p-value Number of lesions (s, IQR)Roof lineFloor lineAdditional ablation inside box 21.5 [19.5-26.3]7.0 [5.8-9.0]13.0 [10.8-14.3]6.0 [6.0-6.8] 24.0 [20.8-29.5]8.0 [6.0-10.0]12.5 [10.8-14.0]5.5 [2.8-9.0] 0.330.180.850.59 Ablation Time per lesion (s, IQR)Roof lineFloor lineAdditional ablation inside box 10.4 [8.8-12.5]13.0 [10.9-16.0]9.9 [8.7-11.4]8.1 [6.9-9.0] 13.0 [11.6-16.2]14.5 [12.4-19.0]12.7 [11.4-15.9]11.8 [10.6-14.0] <0.005<0.005<0.005<0.005 Total RF Time (min, IQR)Roof lineFloor lineAdditional ablation inside box 3.84 [3.34-4.66]1.54 [1.15-1.90]2.06 [1.68-2.54]0.79 [0.65-1.07] 5.86 [4.23-7.73]1.98 [1.62-2.59]2.78 [2.28-3.25]1.07 [0.59-1.42] < 0.0050.0190.0090.50 Impedance Drop (ohms, IQR)Roof lineFloor lineAdditional ablation inside box 7.4 [5.2-10.3]8.7 [6.1-11.3]6.9 [5.0-10.1]7.1 [5.4-9.8] 6.9 [4.8-9.7]7.5 [5.1-10.0]6.0 [4.2-8.3]8.3 [5.8-10.9] 0.0070.04< 0.0050.17 Contact Force (g, IQR)Roof lineFloor lineAdditional ablation inside box 21.1 [14.5-30.3]23.9 [17.8-32.7]19.2 [13.2-25.3]25.5 [18.5-36.9] 21.2 [14.9-28.1]24.3 [17.2-30.3]19.0 [14.1-25.0]23.1 [16.9-31.7] 0.560.450.870.21 Ablation Index (IQR)Roof lineFloor lineAdditional ablation inside box 471 [441-519]560 [509-571]453 [436-475]461 [430-488] 461 [434-493]502 [466-541]446 [426-464]455 [434-478] < 0.005< 0.005< 0.0050.59 Lesion level analysis for Posterior Wall Isolation

How many patients treated for bradycardia may be eligible for His bundle pacing?

Funding Acknowledgements

Type of funding sources: None.

Introduction

Pacing-Induced Cardiomyopathy (PICM) can lead to significant morbidity, requiring treatment by device upgrade procedures. The risk of occurrence is directly related to the burden of right ventricular pacing, which can be reduced by careful device programming. When frequent ventricular stimulation cannot be avoided, pacing the conduction system may offer an alternative to myocardial pacing and reduce the risk of PICM. The most recent international pacing guidelines recommend that His-bundle pacing should be considered among 1) patients with EF 36-50% and expected to require >40% ventricular pacing (Vp > 40%) (class IIa); and 2) patients requiring pacing who have block at the level of the AV node (class IIb).

Purpose

This study sought to determine how many patients undergoing bradycardia pacing would have fulfilled those criteria.

Methods

This was a single-centre retrospective study over a 5 year period to the end of April 2020. Demographic and clinical details of patients receiving device implants were obtained from the Pacing Service Database, along with the indication for pacing, electrocardiographic and echocardiographic data. A cardiology consultant with a special interest in pacing reviewed each case with regards to the likelihood of requiring >40% ventricular pacing. Heart block at the level of the AV node was considered present if patients presented with a narrow QRS in conjunction with second or third degree heart block.

Results

1,265 patients underwent pacemaker implant for bradycardia during the study period, 888 for conduction system disease (198 second degree block, 333 complete heart block), 349 for sinus node disease and 28 for other indication. Figure 1 gives a breakdown of patients with conduction system block according to i) level of block; ii) ejection fraction; iii) expectation or not of Vp > 40%.  In total, 166 patients had a class IIa indication for His-bundle pacing. 227 patients had block at the level of the AV node, of whom 36 also fulfilled the class IIa criteria for His-bundle pacing; 191 patients (16% of the total) had a sole class IIb indication for His-bundle pacing. Adjusting for the 176 patients who did not undergo echocardiography, up to an additional 45 patients may be expected to have an indication for His-bundle pacing

Conclusion

As many as 32% of patients in a bradycardia pacing population may be eligible for His-bundle pacing. This has significant implications for training and service provision. Abstract Figure 1. Flowsheet showing distribution

1266Novel formin homology 2 domain containing 3 (FHOD3) mutations associated with the pathogenesis of hypertrophic cardiomyopathy (HCM) in an Irish population

Background

The genetic cause of hypertrophic cardiomyopathy (HCM) remains unexplained in a substantial proportion of cases. Recent large sequencing studies suggest that, though not previously implicated, FHOD3 (a Formin protein responsible for sarcomere assembly) may have a role in the pathogenesis of HCM, particularly variants affecting a conserved small coil-coiled domain (amino acids 622 to 655).

Aim

To investigate the relationship between novel FHOD3 mutations, previously classified as variants of uncertain significance (American College of Medical Genetics ACMG Class III), and the development of HCM. 

Methods

A single center review of HCM probands carrying mutations in the FHOD3 gene was conducted. Existing HCM patients from the family heart screening clinic database were retrospectively reviewed. Frequency of FHOD3 mutations, segregation among family members and clinical characteristics of patients were reviewed. All genetic analysis was conducted via the same internationally validated next generation sequencing lab.

Results

Of 367 HCM probands identified in our center, 9 (2.45%) were found to have ACMG Class III mutations affecting the FHOD3 gene. Five of these 9 probands (56%) displayed the same p.Arg637Gln mutation, while the remaining 4 (44%) carry the same p.Ile648Thr residue alteration. Both of these are rare mutations, found to be present in <1% of controls in previous large sequencing studies and not previously reported. Among probands with the p.Ile648Thr mutation, co-segregation was confirmed in one family, another first-degree relative in the same family having suffered a sudden cardiac death (HCM confirmed on autopsy). In those with the p.Arg367Gln mutation, a strong family history was observed in two separate families, 4 first-degree members having a confirmed HCM diagnosis. Carriers of both mutation types displayed varying degrees of disease severity with rates of non-sustained ventricular tachycardia and device implantation similar to other HCM cohorts (∼40%).

Conclusions

FHOD3 is a novel gene, recently implicated in the pathogenesis of HCM, though not previously well described in the literature. Carrier frequency of FHOD3 mutations in the HCM population in our center is similar to that described in recent publication (1-2%), and all carry variants affecting the suspected small coil-coiled domain (amino-acids 622-625).

1269The SADS heart of the matter: a review of the sudden arrhythmic death syndrome (SADS) biobank - the cornerstone of a national strategy

Background

Sudden cardiac death (SCD) in the young (age 1-35) is commonly attributed to structural and arrhythmogenic syndromes, for which there is often an underlying genetic basis. Expert recommendation emphasises the importance of genetic testing in such cases, however to date this remains the first and only national programme in Europe to facilitate this. 

Aim

 To review detection rates of genetic variants in samples tested via the SADS BioBank and possibly demonstrate the merits of this novel resource for primary prevention for family members.

Methods

 Family screening and consent for genetic testing was carried out in the Family Heart Screening Clinic. Result analysis of samples sent for molecular autopsy via the BioBank from its induction in January 2015 was performed. Genetic analysis was conducted via the same internationally accredited next generation sequencing lab.

Results

 From January 2015 to July 2019, 161 samples had been stored in the SADS BioBank following confirmed SADS death on autopsy; 33% female and 67% male. Of these, 24 (14.9%) samples were sent for genetic testing: 21 for a 380 gene molecular autopsy and 3 for a targeted hypertrophic cardiomyopathy panel (173 genes). Of 24 samples tested, 10 (42%) yielded positive genetic variants: 4 American College of Medical Genetics (ACMG) Class IV or V mutations considered pathogenic, and 6 ACMG class III variants of uncertain significance (VUS). Familial cascade screening following confirmed pathogenic mutations resulted in detection of 3 (33.3%) positive genotypes in 9 first-degree relatives. Screening of relatives of Class III positive probands resulted in diagnosis of an Inherited Cardiac Condition (ICC) in 25% of first-degree relatives. 8.2% of first-degree relatives of probands with negative gene testing were given an ICC diagnosis following clinical screening.

Conclusions

 This short study demonstrates the unique potential the SADS BioBank has to offer in terms of identifying those most at risk and optimising prevention strategies for relatives, thus highlighting the role for such a resource in terms of preventative screening in the future.

Pathogenic Variant (ACMG Class IV & V) Variant of Uncertain Significance(ACMG Class III) No Gene Variant Identified Number Detected (n = 24) 4 6 14 1st Degree Relatives Screened (n = 86) 17 20 49 2nd Degree Relatives Screened (n = 46) 4 23 19 Genotype Detected (n = 4) 3 1 0 Phenotype Detected (n = 10) 1 5 4 Breakdown of clinical and genetic results of family screening by ACMG class.

Abstract Figure.