Mechanical Tricuspid Valve Research Articles

Successful ablation of cavotricuspid isthmus dependent flutter through a mechanical tricuspid valve

Successful ablation of cavotricuspid isthmus dependent flutter through a mechanical tricuspid valve

RIGHT VENTRICULAR DYSFUNCTION AND TRICUSPID VALVE SURGICAL CORRECTION: ROOM FOR STRESS ECHOCARDIOGRAPHY?

Abstract We report the case of a 50–years–old young woman with multi–operated rheumatic valvular heart disease; aortic, mitral, and tricuspid commissurotomy (1994); aortic valve replacement with bioprosthesis for endocarditis (1998); mitro–aortic replacement with mechanical prosthesis and tricuspid valve plastic repair (1999); mitral valve replacement and re–do of tricuspid plastic repair (2003). Concomitant conduction pathway disease (BAV II type 1 and RBB). The patient was admitted in June 2023 for wet & warm NYHA IV right heart failure with severe peripheral congestion and ascites. On echocardiography: LV with systo–diastolic compression, EF 51%; normo–functioning aortic prosthesis; dilated (TDA 24 cm2), hypokinetic (TAPSE 9mm,S‘ 4 cm/s,FAC 25%) right ventricole (RV), with poor load adaptation (load adaptation index 16, RVCPI 108 mm*mmHg, ePAPI 1.1); torrential IT, caval plethora with systolization of hepatic venous flow. Medical therapy was initiated with intravenous bolus diuretics, nitroglycerin and inotropic support (dobutamine 2.5 y). In order to define the best therapeutic strategy in the persistence of torrential IT and RV dysfunction we performed: trans–oesophageal echocardiography, showed massive IT from ring dilatation and wide flail of the septal flap not suitable for edge–to–edge correction, total–body angioTC, with no relevant findings, right cardiac catheterization, which documented pulmonary pressure and arteriolar resistances within limits (wedge 12 mmHg,PAP25/15/18 mmHg,RAP 11 mmHg,PAPI 0. 9,RVSWI 4.8) with reduced cardiac index (2.14 l/min/cm2) and stress–echocardiography with dobutamine that showed presence of RV contractile reserve (FAC 28%>39%). In consideration of the functional properties of the tricuspid valve, absence of pulmonary hypertension and given the presence of RV contractile reserve, patient underwent tricuspid valve replacement surgery with a bioprosthesis (SJ Epic 27 mm) in mini–thoracotomy with smooth postoperative course. At 3 months follow–up showed functional recovery (NYHA II), with good prosthetic function and partial reverse remodeling of the RV (TDA 14 cm2, FAC of 30%). In conclusion, by documenting right ventricular contractile reserve, stress echocardiography proved to be an important aid in predicting absence of RV failure in the immediate post–surgical period, presenting attractive prospects in the assessment of RV functional reserve in patients undergoing to corrective tricuspidal surgery.

Transcatheter knocking of a stuck mechanical tricuspid valve.

Immobilisation of mechanical valve leaflets can be a life-threatening complication. In the acute setting, medical therapy can be attempted but is not always successful. We present the first described case of a patient with a mechanical tricuspid valve with recurrent leaflet immobilisation that was able to be mobilised using a transcatheter knocking technique.

Management of isolated native tricuspid valve infective endocarditis by a multidisciplinary program: a single-center retrospective cohort study.

Isolated native tricuspid valve infective endocarditis remains a challenging disease to treat given the large number of patients with substance use disorder. There is limited data on the optimal treatment strategy and the impact of a multidisciplinary endocarditis program on outcomes for this population. To assess the clinical outcomes associated with management of native tricuspid valve infective endocarditis by a multidisciplinary team. Single-center, retrospective cohort study. Patient cases were identified from the registry of the institutional multidisciplinary endocarditis team. Patients with left-sided endocarditis, multivalvular endocarditis, prosthetic tricuspid valves and cardiac implantable electronic devices were excluded. Between September 7th, 2021 and February 1st, 2024 72 consecutive patients with isolated native tricuspid valve infective endocarditis were identified. Sixty-six (91.7%) patients were managed medically. Five patients underwent percutaneous mechanical aspiration of tricuspid valve vegetations and one patient underwent tricuspid valve replacement during the index hospitalization. In-hospital mortality was 1.4% and 90-day mortality was 2.8%. Nineteen (26.4%) patients discharged before medically advised and 25% were re-admitted within 30 days. Ten (13.9%) patients underwent elective tricuspid valve replacements after outpatient follow-up. Among 72 patients with isolated native tricuspid valve infective endocarditis managed by a multidisciplinary endocarditis program over a 2.5-year period, in-hospital, 90-day mortality and 1-year mortality were very low despite low rates of percutaneous mechanical aspiration and tricuspid valve surgery. Multidisciplinary follow-up can lead to elective tricuspid valve surgery in a delayed fashion.

A patient with Tuberculous para-valvular leak and tuberculous hepatic abscesses treated conservatively with anti-tuberculous medication without the need for surgical intervention. “Case report”

Introduction: We report a case of a young lady with rheumatic heart disease who underwent mechanical prosthetic mitral valve replacement and tricuspid valve repair. The case was complicated after one year by multi system tuberculous abscesses, para-valvular leak and hemolytic anemia. Case summary: The case started one year following mechanical prosthetic mitral valve replacement, and after contact with a tuberculous patient. The lady developed, sterile pyuria, two tuberculous hepatic abscesses, and a big pelvic tuberculous abscess. She first needed percutaneous drainage for the pelvic abscess followed by laparotomy and surgical drainage after recurrence. The case was complicated by Para-valvular leak in the prosthetic mitral valve detected by Transoesophageal echocardiography as well as refractory hemolytic anemia needing multiple transfusions. She required six months of anti-tuberculous therapy for the hemolysis to stop. Treatment continued for a total of one year of anti-tuberculous therapy. The patient restored normal valve dynamics and hematological parameters without the need for surgical intervention for the para-valvular leak. Conclusion: We report this case to show that small tuberculous para-valvular leak and hemolytic anemia as well as tuberculous hepatic abscesses can be treated medically as an alternative option to the well-known and recommended surgical indication. We also confirm delayed healing of the abdominal surgical wound due to tuberculosis.

Kytococcus Schroeteri Prosthetic Valve Endocarditis Complicated by Aortic Pseudoaneurysm: A Rare Complication from A Rare Agent

Kytococcus schroeteri is a rarely described slow-growing gram-positive coccus, with recent association with Infective Endocarditis cases. A 29-year-old male with prior history of rheumatic valvular heart disease and HIV infection, previously submitted to two cardiac surgeries, the last one 12 years ago with mechanical mitral and aortic valve implantation plus tricuspid annuloplasty was evacuated from Cape Verde with congestive heart failure and no features of infection. The diagnostic workup revealed an aortic paravalvular leak and a large pseudoaneurysm as well as a severe tricuspid regurgitation. The patient underwent surgery with Bentall procedure and a mechanical tricuspid valve implantation. The microbiologic exam of the removed aortic valve using 16sRNA sequencing showed a Kytococcus schroeteri, revealing its association with a severe complicated case of prosthetic valve endocarditis

Coronary sinus pacing in patient with complete heart block after mechanical tricuspid valve implantation

We present a case of a 69-year-old patient after implantation of a mechanical prosthesis of the tricuspid valve due to infective endocarditis and a pacemaker with epicardial lead via substernal approach implanted as the first line treatment of postoperative complete heart block. After approximately 20 years, dysfunction of epicardial pacing lead was diagnosed. The heart team selected transvenous implantation of coronary sinus pacing as the optimal alternative treatment. A Medtronic Attain Ability MRI SureScan lead was successfully inserted via left cephalic venotomy into the coronary sinus venous system. A two years follow-up was uneventful and regular check-up of the pacing system disclosed proper electrical parameters of the pacing system.

A Novel Approach to Diagnostic Left and Right Heart Catheterization in a Patient With a Mechanical Prosthetic Tricuspid Valve.

A 47-year-old patient was experiencing dyspnea and fatigue concerning for right ventricular hypertension and new heart failure. Because of the risks associated with catheter entrapment, prosthetic valve leaflet damage, and valve thrombosis associated with crossing a mechanical valve, a novel technique was used for diagnostic left and right heart catheterization in a patient with mechanical tricuspid valve replacement and tortuous pulmonary arteries. Using a percutaneous subxiphoid approach to avoid traversing the mechanical valve without discontinuing anticoagulation, a Volcano fractional flow reserve pressure wire (Philips Volcano) was advanced for distal measurements of pressures and saturations.

MECHANICAL TRICUSPID VALVE THROMBOSIS TREATED WITH LOW DOSE ALTEPLASE

MECHANICAL TRICUSPID VALVE THROMBOSIS TREATED WITH LOW DOSE ALTEPLASE

Early and long-term outcomes of bioprosthetic versus mechanical tricuspid valve replacement: A nationwide population-based study

ObjectivesWe compared early and long-term clinical outcomes of bioprosthetic versus mechanical tricuspid valve replacement in a nationwide study based on the database from the National Health Insurance Service. MethodsOf 1425 patients who underwent tricuspid valve replacement from 2003 to 2018, 1241 patients were enrolled after excluding retricuspid valve replacement, complex congenital heart disease, Ebstein anomaly, and age less than 18 years at operation. Bioprostheses (group B) and mechanical prostheses (group M) were used in 562 patients (45.3%) and 679 patients (54.7%), respectively. The median follow-up duration was 5.6 years. Propensity score matching was performed. Subgroup analysis was performed in patients aged 50 to 65 years. ResultsThere was no difference in operative mortality or postoperative complications between the groups. All-cause mortality was higher in group B (7.8 vs 4.6 per 100 patient-years, hazard ratio, 1.75, 95% confidence interval, 1.33-2.30, P < .001). The cumulative incidence of stroke was higher in group M (hazard ratio, 0.65, 95% confidence interval, 0.43-0.99, P = .043), whereas the cumulative incidence of reoperation was higher in group B (hazard ratio, 4.20, 95% confidence interval, 1.53-11.54, P = .005). In terms of the age-dependent hazard of all-cause mortality, group B demonstrated a higher hazard than group M below the age of 75 years, and it was statistically significant between 54 and 65 years of age. In the subgroup analysis, all-cause mortality was also higher in group B. ConclusionsMechanical tricuspid valve replacement demonstrated higher long-term survival than bioprosthetic tricuspid valve replacement. In particular, mechanical tricuspid valve replacement showed significantly higher overall survival between 54 and 65 years of age.

Cardiac valve surgery in Far North Queensland, Australia. A retrospective audit of rheumatic heart disease prevalence, patient demographics and surgical management

Abstract Funding Acknowledgements Type of funding sources: None. Background Rheumatic heart disease (RHD) is a preventable valve disease following acute rheumatic fever. It results in &amp;gt;300,000 deaths annually worldwide (1). While commonly encountered in the developing world, the prevalence in Australia remains high with over 6000 patients currently living with RHD (2). This disease is over-represented in Northern Australia among the indigenous community with Aboriginal and Torres-strait Islander people accounting for over 80% of cases (2). Purpose This audit will evaluate the contribution of RHD to valve surgeries in Far North Queensland (FNQ) and the effect this has on procedure type and patient demographics. Methods We analysed a cohort of 200 consecutive patients from a regional centre in FNQ referred for valve surgery. We recorded age, gender, indigenous status, valve aetiology, ejection fraction (EF), surgery type, and procedure urgency. This data was then compared to the latest European Association for Cardio-Thoracic Surgery (EACTS) registry report (3). Results 136 male and 64 female patients underwent 162 elective and 38 emergent valve procedures. The surgeries performed were bioprosthetic AVR (119), mechanical AVR (12), bioprosthetic MVR (14), mechanical MVR (11), TAVR (17), mitral valve repair (25), tricuspid valve repair (6) and balloon valvuloplasty (5) with combined CABG (33) and aortic root surgery (20). Average age at surgery was 64.2 years (range 21 – 89) which is significantly younger than the EACTS age at aortic, mitral and combined valve/CABG procedures. Notably, the average age at surgery reaches 75 years in European countries with a gross national income of $70,000 per capita. However, this is not evident in FNQ. 27 of the 200 procedures were for RHD and the average age of these patients was 45.4 years which explains this discrepancy. Indigenous patients accounted for 16.5% of total, and 77.8% of rheumatic valve surgeries. Mechanical prostheses comprised 15% and 48% of total and rheumatic valve replacements respectively which contrasts with 30-40% in the EACTS registry. RHD also accounted for almost the entirety of tricuspid valve surgeries and balloon valvuloplasties. The EACTS report suggested higher EF’s in Asian countries due to higher prevalence of RHD. This was not observed in our data with no statistically significant difference in EF between RHD patients and the overall cohort. Unfortunately, there is a lack of valve pathology data in the EACTS registry which limits further comparisons. Conclusion RHD is responsible for a significant proportion of valve surgery in FNQ. The indigenous population accounts for a vast majority of these patients. This has caused a shift towards lower age at surgery, higher proportions of mechanical valve replacements, valvuloplasties and tricuspid valve replacements. EF did not significantly differ in patients with rheumatic valve pathology. More data surrounding valve pathology is needed to draw similar conclusions in the EACTS cohorts.

Long-Term Outcomes of Bioprosthetic and Mechanical Tricuspid Valve Replacement after Left-Sided Valves Surgery.

This study aimed to show the outcomes of isolated tricuspid valve replacement (ITVR) after left-sided valve surgery (LSVS). Patients who underwent ITVR after LSVS were divided into bioprosthetic tricuspid valve (BTV) and mechanical tricuspid valve (MTV) groups. Clinical data were collected and analyzed between groups. 101 patients were divided into BTV (n = 46) and MTV (n = 55) groups. The mean ages of the BTV and MTV groups were 63.4 ± 8.9 and 52.4 ± 7.6 years, respectively (P <0.01). There was no significant difference in 30-day mortality (BTV 10.9% vs. MTV 5.5%), early postoperative complications, and long-term tricuspid valve (TV)-related adverse events between these two groups. New-onset renal insufficiency was an independent risk factor for early mortality. Survival rates in the BTV group were 94.8% ± 3.6%, 86.5% ± 6.5%, and 54.2% ± 17.6% and in the MTV group were 96.0% ± 2.8%, 79.0% ± 7.4%, and 59.4% ± 14.8% at 1, 5, and 10 years, respectively (P = 0.826). The TV prosthesis selection in ITVR after LSVS seems to not affect 30-day mortality and early postoperative complications. Long-term survival and the occurrence of TV-related events were also comparable between these two groups.

Mechanical Tricuspid Valves Have Higher Rate of Reintervention: A Single Center Experience.

We compared the composite outcome of tricuspid valve (TV) reintervention or heart failure (HF) admission in patients who underwent tricuspid valve replacement (TVR) with tissue vs. mechanical valves. The study included 159 patients who underwent TVR from 2009 to 2019. We grouped the patients according to the valve's type into tissue valve group (n = 139) and mechanical valve group (n = 20). The mean age of patients was 52.4 ± 12.8 years, and 117 patients were females (73.6%). Hospital mortality occurred in 20 patients (12.6%); all of them were in the tissue valve group. The composite outcome of reintervention and HF readmission occurred in 8 patients with mechanical valves (40%) vs. 24 patients with tissue valves (17.3%), (P = 0.018). Predictors of reintervention and HF admission were female (subdistributional hazard ratio [SHR]: 1.38-34.3, P = 0.019), stroke (SHR: 1.25-8.76, P = 0.016), hypertension (SHR: 1.13-5.36, P = 0.024), and mechanical valves (SHR: 1.6-10.7, P = 0.003). In post hoc analysis, the difference in the composite outcome was derived from the difference in the reintervention rate that was higher in mechanical valves. Survival did not differ significantly between groups (P = 0.12). Mechanical TVs have a higher rate of composite outcome of reintervention or HF readmission than tissue TVs that are related mainly to higher rate of reintervention.

Mechanical tricuspid valve replacement in hypoplastic left heart syndrome: An institutional experience

ObjectiveAtrioventricular valvar regurgitation in patients with single ventricles is associated with worse outcomes. Valve repair or replacement has been undertaken in an attempt to reduce mortality and morbidity. Current data on valve replacement in single ventricle patients are limited and derived from heterogenous populations. We describe our experience with repair and replacement of the tricuspid valve in children undergoing single ventricle palliation for hypoplastic left heart syndrome. MethodsWe included 27 patients with hypoplastic left heart syndrome with at least moderate tricuspid regurgitation who underwent valve intervention between 2007 and 2021 at our institution; charts were retrospectively reviewed for data. ResultsEleven patients (73% male) underwent valve replacement (median age, 3 years). Preoperative ventricular systolic function was normal in 10 patients (91%). Median follow-up postoperatively was 4 years with no early mortality, 1 (9%) late mortality, and 1 heart transplant (9%). Morbidity consisted of complete heart block in 1 patient (9%), with no important hemorrhagic or thrombotic events. Among survivors of replacement (n = 9), ventricular function was preserved in all (n = 8) who had normal function preoperatively and improved in the remaining patient. Sixteen patients underwent valve repair (median age, 4 months) with no early mortality, 8 (50%) midterm mortalities, and 2 heart transplants (12%). ConclusionsTricuspid valve replacement is a feasible option in hypoplastic left heart syndrome with significant tricuspid regurgitation, with favorable outcomes in the intermediate follow-up. When undertaken in the setting of normal function, ventricular function may be preserved in up to 80% of patients. Long-term follow-up is needed.

Mechanical tricuspid valve thrombosis: A midterm follow-up study.

The incidence of prosthetic tricuspid valve (TV) thrombosis is the highest among heart valves. It can lead to high morbidity and mortality without proper treatment. In this study, we sought to report the management and clinical outcomes of patients with mechanical TV thrombosis. The current study was conducted in Rajaei Heart Center on 42 patients with mechanical TV thrombosis from 2006 to 2017. The baseline characteristics and the rates of adverse events during the follow-up period were assessed. A total of 67 episodes of mechanical TV thrombosis in 42 patients were observed. The mean age of patients was 45.5 ± 14.3 years (19-77), and overall two-thirds were female. Thrombolytic therapy was used in 41 (61.1%), anticoagulant intensification in 16 (23.9%), and surgery as the first approach in 10 (14.9%) episodes; subsequently, surgery as the final approach was implemented in 20 (29.8%) episodes. In-hospital mortality occurred in two (2.98%) patients. The rates of freedom from recurrent thrombosis were 84%, 61%, and 21% at the end of 1, 4, and 10 years, respectively. Survival rates and freedom from chronic valve dysfunction were 93%, 82%, and 75% after 1, 4, and 10 years. The results of the present study showed that recurrent thrombosis requiring intervention is a major complication of mechanical TV, which underscores individual-approached therapy and close follow-up.

Permanent pacemaker implantation in Ebstein anomaly with metallic tricuspid valve

Right ventricular endocardial pacing is partially contraindicated in the presence of mechanical tricuspid valve. Occurrences of atrioventricular block are commonly associated in postoperative period in Ebstein anomaly repaired with mechanical tricuspid valve. Coronary sinus (CS) pacing is the preferred site in this scenario. However, the anatomical variations in Ebstein anomaly leads to difficulties in hooking the CS. With the help of real time left coronary injection enabled in understanding the anatomical orientation of CS ostium take off, leading to successful CS lead implantation.

Multiparametric Approach for the Assessment of Mechanical Prosthetic Tricuspid Leaflet Function

There is a lack of comprehensive echocardiographic data to allow discrimination of normal versus abnormal mechanical prosthetic tricuspid valve (MPTV) leaflet function. The identification of such parameters is essential to optimize diagnostic and therapeutic measures. The authors investigated bileaflet MPTV function by comparing transthoracic echocardiographic data from 21 episodes of leaflet dysfunction due to valve thrombosis in 12 patients with data from 56 individuals with normal MPTV function. All episodes of dysfunction were confirmed by transesophageal echocardiography and/or cine fluoroscopy. Transthoracic echocardiography-derived two-dimensional, color, and spectral Doppler variables, including MPTV peak early diastolic velocity (E velocity), mean gradient, pressure half-time, time-velocity integral (TVI) of the MPTV, ratio of TVIMPTV to TVI of the left ventricular outflow tract (LVOT) and TVI of the right ventricular outflow tract (RVOT), and continuity-derived effective orifice area, were measured in both groups. Most episodes of MPTV dysfunction resulted from simultaneous involvement of both leaflets (57%), with leaflet(s) often immobilized in the open or semiopen position (71%). Transthoracic and transesophageal echocardiography performed similarly in detecting abnormal leaflet motion (90% vs 88%, P=.68), whereas transesophageal echocardiography was better in identifying MPTV thrombosis (31% vs 14%, respectively, P=.01). Color Doppler demonstrated flow propagation abnormalities in 67% of episodes of leaflet dysfunction but not in the control group (P<.0001). Doppler variables associated with MPTV leaflet dysfunction included E velocity > 1.6m/sec, mean gradient > 5mm Hg, PHT > 157 msec, TVIMPTV > 42cm, TVIMPTV/TVILVOT > 2.3, TVIMPTV/TVIRVOT > 3.0, and continuity-derived effective orifice area ≤ 1.1cm2, with most variables showing high and similar accuracy (area under the curve ≥ 95%). This study represents the first comprehensive echocardiographic assessment of MPTV leaflet dysfunction that provides parameters and criteria to distinguish normal versus abnormal prosthetic valve function.

Reappraisal of mechanical tricuspid valve replacement in the current era: a single center retrospective study

BackgroundThis study aimed to investigate the early and late outcomes of mechanical tricuspid valve replacement (mTVR).MethodsWe evaluated 113 patients (82 women; median age, 53 years) who underwent mTVR between 1995 and 2017. Based on a history of cardiac surgery, patients were divided into primary (n=42) and reoperative mTVR (n=71) groups. The median follow-up duration was 12.7 years in primary and 9.3 years in reoperative mTVR, respectively (P=0.045).ResultsPatients in the reoperative group were older (54 vs. 46 years; P=0.007) and showed higher central venous pressure (16±6 vs. 13±6 mmHg; P=0.002) than the primary group. Early mortality occurred in 2 patients in the reoperative group (2 vs. 0; P=0.529). There was no significant difference in overall survival between the primary and reoperation groups (15-year survival rate: 86% vs. 78%; P=0.215). The independent risk factors of overall survival were age [P<0.001; hazard ratio (HR), 1.11; 95% confidential interval (CI), 1.05–1.18], left ventricular ejection fraction of less than 40% (P=0.001; HR, 5.1; 95% CI, 2.21–28.2), and central venous pressure over 20 mmHg (P=0.016; HR, 3.7; 95% CI, 1.28–10.7). Overall survival did not differ between the age groups (<60 vs. 60–70 years) in the reoperative group (P=0.772). Tricuspid valve thrombosis occurred in 8 patients (7 primary, 1 reoperative; P=0.004).ConclusionsThe incidence of tricuspid valve thrombosis was significantly higher in the primary mTVR group compared with the reoperative mTVR group. The patients who underwent mTVR at a relatively young age showed good early and late outcomes in both groups.

Which is the best prosthesis in an isolated or combined tricuspid valve replacement?

The debate concerning the optimal choice of tricuspid position continues. We compared the long-term results of mechanical and biological prostheses in patients who underwent isolated or combined tricuspid valve replacement, at 2 major cardiac surgical centres in central China. From January 1999 to December 2018, 338 patients underwent tricuspid valve replacement. Patients were divided into an isolated group or a combined group according to whether their surgery was combined with a left heart valve surgery. Mechanical tricuspid valve replacement was performed in 142 patients (isolated group: 41 vs combined group: 101), and 196 patients underwent bioprosthetic tricuspid valve replacement (isolated group: 145 vs combined group: 51). Operative results, long-term survival and tricuspid valve-related events were compared. Early mortality in the combined group was higher (n = 6, 4%) than that in the isolated group (n = 3, 2%), but no significant difference was observed between the mechanical and biological subgroups. In the isolated group, there was a higher event-free rate in the biological subgroup than in the mechanical subgroup (P = 0.042) and a similar result was also observed for patients without Ebstein's anomaly (P = 0.039). In the combined group, no significant difference was observed (P = 0.98). Survival rates were similar between the mechanical and biological subgroups in both the isolated (P = 0.54) and combined (P = 0.81) groups. Mechanical valves in isolated tricuspid valve replacement were more prone to valve thrombosis and bleeding. Every decision regarding tricuspid valve prostheses should be individualized, but biological prostheses may be an optimal choice for patients, especially for patients without Ebstein's anomaly, in isolated tricuspid valve replacement.

His-Bundle Pacing From the Right Atrium in a Patient With Tetralogy of Fallot and a Prosthetic Tricuspid Valve.

A mechanical tricuspid valve makes it difficult to implant a transvenous endocardial lead in the right ventricle, necessitating pacing by alternative nonphysiological methods such as implanting an epicardial lead and pacing through the coronary sinus. Permanent His-bundle pacing is an increasingly