His bundle pacing improves left ventricular diastolic function in patients with heart failure with preserved systolic function

Abstract

Key Teaching Points•There currently are no guideline recommendations for cardiac resynchronization therapy or for conduction system pacing in patients dependent on chronic ventricular pacing in the setting of preserved ejection fraction.•His bundle pacing can improve exertional intolerance in patients with chronic right ventricular pacing in the setting of a normal ejection fraction.•His bundle pacing may be associated with improved diastolic function when compared to right ventricular apical pacing.•Prospective randomized controlled trials are warranted to elucidate the benefit of conduction system pacing compared to conventional right ventricular pacing in this patient population.IntroductionCardiac resynchronization therapy (CRT) is highly effective for patients with left bundle branch block, heart failure, and left ventricular (LV) systolic dysfunction. In heart failure patients with systolic dysfunction, CRT can also improve diastolic dysfunction.1Aksoy H. Okutucu S. Kaya E.B. et al.Clinical and echocardiographic correlates of improvement in left ventricular diastolic function after cardiac resynchronization therapy.Europace. 2010; 12: 1256-1261Crossref PubMed Scopus (27) Google Scholar Evidence guiding diastolic heart failure treatment is limited.2Butler J. Fonarow G.C. Zile M.R. et al.Developing therapies for heart failure with preserved ejection fraction: current state and future directions.JACC Heart Fail. 2014; 2: 97-112Crossref PubMed Scopus (246) Google ScholarSimilar to left bundle branch block, chronic right ventricular pacing (RVP) is associated with pacing-induced cardiomyopathy and may result in exertional dyspnea in absence of LV systolic dysfunction.3Kiehl E.L. Makki T. Kumar R. et al.Incidence and predictors of right ventricular pacing-induced cardiomyopathy in patients with complete atrioventricular block and preserved left ventricular systolic function.Heart Rhythm. 2016; 13: 2272-2278https://doi.org/10.1016/j.hrthm.2016.09.027Abstract Full Text Full Text PDF PubMed Scopus (169) Google Scholar Observational studies have shown that His bundle pacing (HBP) in patients dependent on chronic RVP can restore physiologic ventricular activation and improve LV systolic function.4Vijayaraman P. Herweg B. Dandamudi G. et al.Outcomes of His-bundle pacing upgrade after long-term right ventricular pacing and/or pacing-induced cardiomyopathy: insights into disease progression.Heart Rhythm. 2019; 16: 1554-1561Abstract Full Text Full Text PDF PubMed Scopus (43) Google Scholar We investigated the acute changes of echocardiographic parameters of overall cardiac function and diastolic function5Nagueh S.F. Smiseth O.A. Appleton C.P. et al.Recommendations for the evaluation of left ventricular diastolic function by echocardiography: an update from the American Society of Echocardiography and the European Association of Cardiovascular Imaging.J Am Soc Echocardiogr. 2016; 29: 277-314Abstract Full Text Full Text PDF PubMed Scopus (2589) Google Scholar,6Tei C. Ling L.H. Hodge D.O. et al.New index of combined systolic and diastolic myocardial performance: a simple and reproducible measure of cardiac function--a study in normals and dilated cardiomyopathy.J Cardiol. 1995; 26: 357-366PubMed Google Scholar during HBP compared to RVP in patients with preserved LV systolic function and exertional intolerance.Case reportWe studied 5 consecutive patients with a dual-chamber pacemaker and apical RVP lead implanted for complete atrioventricular (AV) block (all male, aged 78 ± 3 years, body mass index 27 ± 6, QRS duration 179 ± 13 ms, septal and posterior wall thickness 1.16 ± 0.05 and 1.12 ± 0.15 cm, respectively). All patients suffered from exertional intolerance despite preserved LV systolic function. At the time of generator change, an HBP lead (Model 3830; Medtronic Inc, Minneapolis, MN) was implanted and plugged to the LV port of the CRT-pacemaker, which resulted in nonselective HBP capture in all patients. Echocardiographic parameters of diastolic and global cardiac function were then obtained during RVP and HBP, with similar AV intervals. Paced AV intervals were optimized prior to hemodynamic assessment using the mitral inflow iterative method. The grade of diastolic dysfunction was calculated based on standard echocardiographic parameters.5Nagueh S.F. Smiseth O.A. Appleton C.P. et al.Recommendations for the evaluation of left ventricular diastolic function by echocardiography: an update from the American Society of Echocardiography and the European Association of Cardiovascular Imaging.J Am Soc Echocardiogr. 2016; 29: 277-314Abstract Full Text Full Text PDF PubMed Scopus (2589) Google Scholar The Tei or MPI (myocardial performance index), a measure of combined diastolic and systolic function, was calculated as the ratio of the time spent in isovolumetric activity divided by the time spent in ventricular ejection.6Tei C. Ling L.H. Hodge D.O. et al.New index of combined systolic and diastolic myocardial performance: a simple and reproducible measure of cardiac function--a study in normals and dilated cardiomyopathy.J Cardiol. 1995; 26: 357-366PubMed Google ScholarResultsThe QRS duration decreased from 179 ± 13 ms with RVP to 113 ± 6 ms with HBP (P < .001, Figure 1A and 1B ). Four out of 5 patients noted acute improvement of dyspnea. LV ejection fraction was 59% ± 6% with RVP and 64% ± 8% with HBP (P = .5). Compared to RVP, HBP was associated with increased diastolic filling time (440 ± 67 ms vs 484 ± 47 ms, P < .05), increase in septal E′ (5.6 ± 1.5 vs 6.0 ± 1.7, P < .05), and decreased Tei index (0.57 ± 0.27 vs 0.44 ± 0.19, P = .08) (Figure 1). No differences were found in lateral E′ (9.9 ± 4.9 with RVP vs 9.8 ± 3.2 with HBP) and mitral inflow E/A ratio (1.2 ± 0.6 for both). The LV outflow tract velocity time integral (reflecting stroke volume) increased from 17.7 ± 3.6 with RVP to 20.0 ± 5.0 with HBP (P = .19). The clinical characteristics, echocardiographic findings, and long-term HBP thresholds are summarized in Table 1.Table 1Clinical characteristics, device-related data, and echocardiographic findings during right ventricular vs His bundle pacingPatient / age (y) / sexHeart rate (bpm) AV interval (ms)LA volume (mL)BMI / BSAValvular diseaseLVEFE/e’•septal, lateral (avg)Mitral valve inflow•E, A wave (cm/s), (E/A ratio)Tricuspid regurgitation velocity (m/s)Tei/MPI, DD gradeQRS duration His bundle threshold at follow-upPatient 1 / 82 / femaleRV paced•60/200∗Atrial sensed.His paced•60/200∗Atrial sensed.RV paced•22.5His paced•27.420 / 2.1Mild MR72%RV paced•17.7, 21.4 (19.5)His bundle paced•25.2, 16.7 (20.9)RV paced• 124, 60 (2.1)His bundle paced•124, 48 (2.6)RV paced•3.3His bundle paced•3.3RV paced•0.16, 3His bundle paced•0.15, 3RV paced•180 msHis bundle•114 ms•0.4 V @ 1.0 msPatient 2 / 78 / maleRV paced•65/140∗Atrial sensed.His paced•65/140∗Atrial sensed.RV paced•27.2His paced•27.526 / 2.0None63%RV paced•10.5, 10.9 (10.7)His bundle paced•7.4, 7.2 (7.3)RV paced• 93, 93 (1.0)His bundle paced•68, 89 (0.75)RV paced•2.6His bundle paced• 2.5RV paced•0.51, normalHis bundle paced•0.35, normalRV paced•175 msHis bundle•118 ms•1.75 V @ 0.5 msPatient 3 / 78 / maleRV paced•68/210∗Atrial sensed.His paced•68/210∗Atrial sensed.NA; poor image quality37 / 2.6Trivial MR55%RV paced•10.7, 7.5 (9.1)His bundle paced•9.1, 5.5 (7.3)RV paced• 54, 55 (0.98)His bundle paced•58, 61 (0.95)RV paced•2.1His bundle paced• 2.1RV paced•0.69, 1His bundle paced•0.52, 1RV paced•160 msHis bundle•120 ms•1.3 V @ 1.0 msPatient 4 / 85 / maleRV paced•60/250†Atrial paced.His paced•60/250†Atrial paced.RV paced•61.5His paced•61.524 / 1.8Mild MR56%RV paced•12.7, 5.4 (9.1)His bundle paced•13.2, 4.6 (8.9)RV paced• 59, 65 (0.91)His bundle paced•68, 67 (1.01)RV paced•2.2His bundle paced• 2.2RV paced•0.92, 1His bundle paced•0.6, 1RV paced•184 msHis bundle•110 ms•1.1 V @ 0.5 msPatient 5 / 80 / maleRV paced•65/230∗Atrial sensed.His paced•65/230∗Atrial sensed.RV paced•31.1His paced•31.129 / 2.2None56%RV paced•14.3, 3.97 (9.1)His bundle paced•15.3, 5.99 (10.6)RV paced• 92, 85 (1.1)His bundle paced•90, 80 (1.3)RV paced•2.4His bundle paced• 2.2RV paced•0.57, normalHis bundle paced•0.56, normalRV paced•195 msHis bundle•105 ms•0.5 V @ 0.5 msAvg = average; BMI = body mass index; BPM = beats per minute; BSA = body surface area; LA = left atrium; LVEF = left ventricular ejection fraction; MPI = myocardial performance index; MR = mitral regurgitation; RV = right ventricle.∗ Atrial sensed.† Atrial paced. Open table in a new tab At follow-up of 57 ± 21 months, 4 of 5 patients reported good functional tolerance; 1 patient had diminished functional capacity due to advanced lung disease. One patient died from an acute unrelated illness 22 months after implantation.DiscussionWe present 5 consecutive patients with AV block and preserved LV systolic function experiencing disabling exertional intolerance presumed to be related to chronic RVP and diastolic dysfunction. Owing to lack of other therapeutic alternatives, we upgraded their conventional dual-chamber pacing system to a CRT-pacemaker with a His bundle pacing lead. This enabled us to compare echocardiographic parameters of overall cardiac function and diastolic dysfunction during RVP and HBP at optimized AV interval settings.It is impressive that despite normal LV systolic function, the LV stroke volume, a measure of overall cardiac function, increased by 13%, and the diastolic filling time increased by 11%, accompanied by improved septal early diastolic myocardial relaxation velocity (E′). In 4 out of 5 of our patients with symptomatic heart failure with preserved ejection fraction, conduction system pacing resulted in a remarkable improvement of heart failure symptoms. The acute impact of HBP on diastolic function has not been reported in patients with preserved LV function, although it has been demonstrated in patients with reduced ejection fraction.7Kato H. Yanagisawa S. Sakurai T. et al.Efficacy of His bundle pacing on LV relaxation and clinical improvement in HF and LBBB.JACC Clin Electrophysiol. 2022; 8: 59-69https://doi.org/10.1016/j.jacep.2021.06.011Crossref PubMed Scopus (5) Google ScholarPacing to maintain physiologic ventricular activation is recommended in patients with AV nodal block and an LV ejection fraction of 36%–50% if the ventricular pacing burden is expected to be >40% (class IIa indication). There are no current guideline recommendations for conduction system pacing in patients with preserved LV systolic function.8Kusumoto F.M. Schoenfeld M.H. Barrett C. et al.2018 ACC/AHA/HRS Guideline on the Evaluation and Management of Patients With Bradycardia and Cardiac Conduction Delay: Executive Summary: A Report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines, and the Heart Rhythm Society.Circulation. 2019; 140: e333-e381PubMed Google Scholar Randomized controlled trials are warranted to explore the effects of conduction system pacing on diastolic function and to determine the potential therapeutic benefits for heart failure patients with preserved ejection fraction.9Infeld M. Wahlberg K. Cicero J. et al.Personalized pacing for diastolic dysfunction and heart failure with preserved ejection fraction: design and rationale for the myPACE randomized controlled trial.Heart Rhythm O2. 2021; 3: 109-116Abstract Full Text Full Text PDF PubMed Scopus (1) Google Scholar Key Teaching Points•There currently are no guideline recommendations for cardiac resynchronization therapy or for conduction system pacing in patients dependent on chronic ventricular pacing in the setting of preserved ejection fraction.•His bundle pacing can improve exertional intolerance in patients with chronic right ventricular pacing in the setting of a normal ejection fraction.•His bundle pacing may be associated with improved diastolic function when compared to right ventricular apical pacing.•Prospective randomized controlled trials are warranted to elucidate the benefit of conduction system pacing compared to conventional right ventricular pacing in this patient population. •There currently are no guideline recommendations for cardiac resynchronization therapy or for conduction system pacing in patients dependent on chronic ventricular pacing in the setting of preserved ejection fraction.•His bundle pacing can improve exertional intolerance in patients with chronic right ventricular pacing in the setting of a normal ejection fraction.•His bundle pacing may be associated with improved diastolic function when compared to right ventricular apical pacing.•Prospective randomized controlled trials are warranted to elucidate the benefit of conduction system pacing compared to conventional right ventricular pacing in this patient population. •There currently are no guideline recommendations for cardiac resynchronization therapy or for conduction system pacing in patients dependent on chronic ventricular pacing in the setting of preserved ejection fraction.•His bundle pacing can improve exertional intolerance in patients with chronic right ventricular pacing in the setting of a normal ejection fraction.•His bundle pacing may be associated with improved diastolic function when compared to right ventricular apical pacing.•Prospective randomized controlled trials are warranted to elucidate the benefit of conduction system pacing compared to conventional right ventricular pacing in this patient population. IntroductionCardiac resynchronization therapy (CRT) is highly effective for patients with left bundle branch block, heart failure, and left ventricular (LV) systolic dysfunction. In heart failure patients with systolic dysfunction, CRT can also improve diastolic dysfunction.1Aksoy H. Okutucu S. Kaya E.B. et al.Clinical and echocardiographic correlates of improvement in left ventricular diastolic function after cardiac resynchronization therapy.Europace. 2010; 12: 1256-1261Crossref PubMed Scopus (27) Google Scholar Evidence guiding diastolic heart failure treatment is limited.2Butler J. Fonarow G.C. Zile M.R. et al.Developing therapies for heart failure with preserved ejection fraction: current state and future directions.JACC Heart Fail. 2014; 2: 97-112Crossref PubMed Scopus (246) Google ScholarSimilar to left bundle branch block, chronic right ventricular pacing (RVP) is associated with pacing-induced cardiomyopathy and may result in exertional dyspnea in absence of LV systolic dysfunction.3Kiehl E.L. Makki T. Kumar R. et al.Incidence and predictors of right ventricular pacing-induced cardiomyopathy in patients with complete atrioventricular block and preserved left ventricular systolic function.Heart Rhythm. 2016; 13: 2272-2278https://doi.org/10.1016/j.hrthm.2016.09.027Abstract Full Text Full Text PDF PubMed Scopus (169) Google Scholar Observational studies have shown that His bundle pacing (HBP) in patients dependent on chronic RVP can restore physiologic ventricular activation and improve LV systolic function.4Vijayaraman P. Herweg B. Dandamudi G. et al.Outcomes of His-bundle pacing upgrade after long-term right ventricular pacing and/or pacing-induced cardiomyopathy: insights into disease progression.Heart Rhythm. 2019; 16: 1554-1561Abstract Full Text Full Text PDF PubMed Scopus (43) Google Scholar We investigated the acute changes of echocardiographic parameters of overall cardiac function and diastolic function5Nagueh S.F. Smiseth O.A. Appleton C.P. et al.Recommendations for the evaluation of left ventricular diastolic function by echocardiography: an update from the American Society of Echocardiography and the European Association of Cardiovascular Imaging.J Am Soc Echocardiogr. 2016; 29: 277-314Abstract Full Text Full Text PDF PubMed Scopus (2589) Google Scholar,6Tei C. Ling L.H. Hodge D.O. et al.New index of combined systolic and diastolic myocardial performance: a simple and reproducible measure of cardiac function--a study in normals and dilated cardiomyopathy.J Cardiol. 1995; 26: 357-366PubMed Google Scholar during HBP compared to RVP in patients with preserved LV systolic function and exertional intolerance. Cardiac resynchronization therapy (CRT) is highly effective for patients with left bundle branch block, heart failure, and left ventricular (LV) systolic dysfunction. In heart failure patients with systolic dysfunction, CRT can also improve diastolic dysfunction.1Aksoy H. Okutucu S. Kaya E.B. et al.Clinical and echocardiographic correlates of improvement in left ventricular diastolic function after cardiac resynchronization therapy.Europace. 2010; 12: 1256-1261Crossref PubMed Scopus (27) Google Scholar Evidence guiding diastolic heart failure treatment is limited.2Butler J. Fonarow G.C. Zile M.R. et al.Developing therapies for heart failure with preserved ejection fraction: current state and future directions.JACC Heart Fail. 2014; 2: 97-112Crossref PubMed Scopus (246) Google Scholar Similar to left bundle branch block, chronic right ventricular pacing (RVP) is associated with pacing-induced cardiomyopathy and may result in exertional dyspnea in absence of LV systolic dysfunction.3Kiehl E.L. Makki T. Kumar R. et al.Incidence and predictors of right ventricular pacing-induced cardiomyopathy in patients with complete atrioventricular block and preserved left ventricular systolic function.Heart Rhythm. 2016; 13: 2272-2278https://doi.org/10.1016/j.hrthm.2016.09.027Abstract Full Text Full Text PDF PubMed Scopus (169) Google Scholar Observational studies have shown that His bundle pacing (HBP) in patients dependent on chronic RVP can restore physiologic ventricular activation and improve LV systolic function.4Vijayaraman P. Herweg B. Dandamudi G. et al.Outcomes of His-bundle pacing upgrade after long-term right ventricular pacing and/or pacing-induced cardiomyopathy: insights into disease progression.Heart Rhythm. 2019; 16: 1554-1561Abstract Full Text Full Text PDF PubMed Scopus (43) Google Scholar We investigated the acute changes of echocardiographic parameters of overall cardiac function and diastolic function5Nagueh S.F. Smiseth O.A. Appleton C.P. et al.Recommendations for the evaluation of left ventricular diastolic function by echocardiography: an update from the American Society of Echocardiography and the European Association of Cardiovascular Imaging.J Am Soc Echocardiogr. 2016; 29: 277-314Abstract Full Text Full Text PDF PubMed Scopus (2589) Google Scholar,6Tei C. Ling L.H. Hodge D.O. et al.New index of combined systolic and diastolic myocardial performance: a simple and reproducible measure of cardiac function--a study in normals and dilated cardiomyopathy.J Cardiol. 1995; 26: 357-366PubMed Google Scholar during HBP compared to RVP in patients with preserved LV systolic function and exertional intolerance. Case reportWe studied 5 consecutive patients with a dual-chamber pacemaker and apical RVP lead implanted for complete atrioventricular (AV) block (all male, aged 78 ± 3 years, body mass index 27 ± 6, QRS duration 179 ± 13 ms, septal and posterior wall thickness 1.16 ± 0.05 and 1.12 ± 0.15 cm, respectively). All patients suffered from exertional intolerance despite preserved LV systolic function. At the time of generator change, an HBP lead (Model 3830; Medtronic Inc, Minneapolis, MN) was implanted and plugged to the LV port of the CRT-pacemaker, which resulted in nonselective HBP capture in all patients. Echocardiographic parameters of diastolic and global cardiac function were then obtained during RVP and HBP, with similar AV intervals. Paced AV intervals were optimized prior to hemodynamic assessment using the mitral inflow iterative method. The grade of diastolic dysfunction was calculated based on standard echocardiographic parameters.5Nagueh S.F. Smiseth O.A. Appleton C.P. et al.Recommendations for the evaluation of left ventricular diastolic function by echocardiography: an update from the American Society of Echocardiography and the European Association of Cardiovascular Imaging.J Am Soc Echocardiogr. 2016; 29: 277-314Abstract Full Text Full Text PDF PubMed Scopus (2589) Google Scholar The Tei or MPI (myocardial performance index), a measure of combined diastolic and systolic function, was calculated as the ratio of the time spent in isovolumetric activity divided by the time spent in ventricular ejection.6Tei C. Ling L.H. Hodge D.O. et al.New index of combined systolic and diastolic myocardial performance: a simple and reproducible measure of cardiac function--a study in normals and dilated cardiomyopathy.J Cardiol. 1995; 26: 357-366PubMed Google Scholar We studied 5 consecutive patients with a dual-chamber pacemaker and apical RVP lead implanted for complete atrioventricular (AV) block (all male, aged 78 ± 3 years, body mass index 27 ± 6, QRS duration 179 ± 13 ms, septal and posterior wall thickness 1.16 ± 0.05 and 1.12 ± 0.15 cm, respectively). All patients suffered from exertional intolerance despite preserved LV systolic function. At the time of generator change, an HBP lead (Model 3830; Medtronic Inc, Minneapolis, MN) was implanted and plugged to the LV port of the CRT-pacemaker, which resulted in nonselective HBP capture in all patients. Echocardiographic parameters of diastolic and global cardiac function were then obtained during RVP and HBP, with similar AV intervals. Paced AV intervals were optimized prior to hemodynamic assessment using the mitral inflow iterative method. The grade of diastolic dysfunction was calculated based on standard echocardiographic parameters.5Nagueh S.F. Smiseth O.A. Appleton C.P. et al.Recommendations for the evaluation of left ventricular diastolic function by echocardiography: an update from the American Society of Echocardiography and the European Association of Cardiovascular Imaging.J Am Soc Echocardiogr. 2016; 29: 277-314Abstract Full Text Full Text PDF PubMed Scopus (2589) Google Scholar The Tei or MPI (myocardial performance index), a measure of combined diastolic and systolic function, was calculated as the ratio of the time spent in isovolumetric activity divided by the time spent in ventricular ejection.6Tei C. Ling L.H. Hodge D.O. et al.New index of combined systolic and diastolic myocardial performance: a simple and reproducible measure of cardiac function--a study in normals and dilated cardiomyopathy.J Cardiol. 1995; 26: 357-366PubMed Google Scholar ResultsThe QRS duration decreased from 179 ± 13 ms with RVP to 113 ± 6 ms with HBP (P < .001, Figure 1A and 1B ). Four out of 5 patients noted acute improvement of dyspnea. LV ejection fraction was 59% ± 6% with RVP and 64% ± 8% with HBP (P = .5). Compared to RVP, HBP was associated with increased diastolic filling time (440 ± 67 ms vs 484 ± 47 ms, P < .05), increase in septal E′ (5.6 ± 1.5 vs 6.0 ± 1.7, P < .05), and decreased Tei index (0.57 ± 0.27 vs 0.44 ± 0.19, P = .08) (Figure 1). No differences were found in lateral E′ (9.9 ± 4.9 with RVP vs 9.8 ± 3.2 with HBP) and mitral inflow E/A ratio (1.2 ± 0.6 for both). The LV outflow tract velocity time integral (reflecting stroke volume) increased from 17.7 ± 3.6 with RVP to 20.0 ± 5.0 with HBP (P = .19). The clinical characteristics, echocardiographic findings, and long-term HBP thresholds are summarized in Table 1.Table 1Clinical characteristics, device-related data, and echocardiographic findings during right ventricular vs His bundle pacingPatient / age (y) / sexHeart rate (bpm) AV interval (ms)LA volume (mL)BMI / BSAValvular diseaseLVEFE/e’•septal, lateral (avg)Mitral valve inflow•E, A wave (cm/s), (E/A ratio)Tricuspid regurgitation velocity (m/s)Tei/MPI, DD gradeQRS duration His bundle threshold at follow-upPatient 1 / 82 / femaleRV paced•60/200∗Atrial sensed.His paced•60/200∗Atrial sensed.RV paced•22.5His paced•27.420 / 2.1Mild MR72%RV paced•17.7, 21.4 (19.5)His bundle paced•25.2, 16.7 (20.9)RV paced• 124, 60 (2.1)His bundle paced•124, 48 (2.6)RV paced•3.3His bundle paced•3.3RV paced•0.16, 3His bundle paced•0.15, 3RV paced•180 msHis bundle•114 ms•0.4 V @ 1.0 msPatient 2 / 78 / maleRV paced•65/140∗Atrial sensed.His paced•65/140∗Atrial sensed.RV paced•27.2His paced•27.526 / 2.0None63%RV paced•10.5, 10.9 (10.7)His bundle paced•7.4, 7.2 (7.3)RV paced• 93, 93 (1.0)His bundle paced•68, 89 (0.75)RV paced•2.6His bundle paced• 2.5RV paced•0.51, normalHis bundle paced•0.35, normalRV paced•175 msHis bundle•118 ms•1.75 V @ 0.5 msPatient 3 / 78 / maleRV paced•68/210∗Atrial sensed.His paced•68/210∗Atrial sensed.NA; poor image quality37 / 2.6Trivial MR55%RV paced•10.7, 7.5 (9.1)His bundle paced•9.1, 5.5 (7.3)RV paced• 54, 55 (0.98)His bundle paced•58, 61 (0.95)RV paced•2.1His bundle paced• 2.1RV paced•0.69, 1His bundle paced•0.52, 1RV paced•160 msHis bundle•120 ms•1.3 V @ 1.0 msPatient 4 / 85 / maleRV paced•60/250†Atrial paced.His paced•60/250†Atrial paced.RV paced•61.5His paced•61.524 / 1.8Mild MR56%RV paced•12.7, 5.4 (9.1)His bundle paced•13.2, 4.6 (8.9)RV paced• 59, 65 (0.91)His bundle paced•68, 67 (1.01)RV paced•2.2His bundle paced• 2.2RV paced•0.92, 1His bundle paced•0.6, 1RV paced•184 msHis bundle•110 ms•1.1 V @ 0.5 msPatient 5 / 80 / maleRV paced•65/230∗Atrial sensed.His paced•65/230∗Atrial sensed.RV paced•31.1His paced•31.129 / 2.2None56%RV paced•14.3, 3.97 (9.1)His bundle paced•15.3, 5.99 (10.6)RV paced• 92, 85 (1.1)His bundle paced•90, 80 (1.3)RV paced•2.4His bundle paced• 2.2RV paced•0.57, normalHis bundle paced•0.56, normalRV paced•195 msHis bundle•105 ms•0.5 V @ 0.5 msAvg = average; BMI = body mass index; BPM = beats per minute; BSA = body surface area; LA = left atrium; LVEF = left ventricular ejection fraction; MPI = myocardial performance index; MR = mitral regurgitation; RV = right ventricle.∗ Atrial sensed.† Atrial paced. Open table in a new tab At follow-up of 57 ± 21 months, 4 of 5 patients reported good functional tolerance; 1 patient had diminished functional capacity due to advanced lung disease. One patient died from an acute unrelated illness 22 months after implantation. The QRS duration decreased from 179 ± 13 ms with RVP to 113 ± 6 ms with HBP (P < .001, Figure 1A and 1B ). Four out of 5 patients noted acute improvement of dyspnea. LV ejection fraction was 59% ± 6% with RVP and 64% ± 8% with HBP (P = .5). Compared to RVP, HBP was associated with increased diastolic filling time (440 ± 67 ms vs 484 ± 47 ms, P < .05), increase in septal E′ (5.6 ± 1.5 vs 6.0 ± 1.7, P < .05), and decreased Tei index (0.57 ± 0.27 vs 0.44 ± 0.19, P = .08) (Figure 1). No differences were found in lateral E′ (9.9 ± 4.9 with RVP vs 9.8 ± 3.2 with HBP) and mitral inflow E/A ratio (1.2 ± 0.6 for both). The LV outflow tract velocity time integral (reflecting stroke volume) increased from 17.7 ± 3.6 with RVP to 20.0 ± 5.0 with HBP (P = .19). The clinical characteristics, echocardiographic findings, and long-term HBP thresholds are summarized in Table 1. Avg = average; BMI = body mass index; BPM = beats per minute; BSA = body surface area; LA = left atrium; LVEF = left ventricular ejection fraction; MPI = myocardial performance index; MR = mitral regurgitation; RV = right ventricle. At follow-up of 57 ± 21 months, 4 of 5 patients reported good functional tolerance; 1 patient had diminished functional capacity due to advanced lung disease. One patient died from an acute unrelated illness 22 months after implantation. DiscussionWe present 5 consecutive patients with AV block and preserved LV systolic function experiencing disabling exertional intolerance presumed to be related to chronic RVP and diastolic dysfunction. Owing to lack of other therapeutic alternatives, we upgraded their conventional dual-chamber pacing system to a CRT-pacemaker with a His bundle pacing lead. This enabled us to compare echocardiographic parameters of overall cardiac function and diastolic dysfunction during RVP and HBP at optimized AV interval settings.It is impressive that despite normal LV systolic function, the LV stroke volume, a measure of overall cardiac function, increased by 13%, and the diastolic filling time increased by 11%, accompanied by improved septal early diastolic myocardial relaxation velocity (E′). In 4 out of 5 of our patients with symptomatic heart failure with preserved ejection fraction, conduction system pacing resulted in a remarkable improvement of heart failure symptoms. The acute impact of HBP on diastolic function has not been reported in patients with preserved LV function, although it has been demonstrated in patients with reduced ejection fraction.7Kato H. Yanagisawa S. Sakurai T. et al.Efficacy of His bundle pacing on LV relaxation and clinical improvement in HF and LBBB.JACC Clin Electrophysiol. 2022; 8: 59-69https://doi.org/10.1016/j.jacep.2021.06.011Crossref PubMed Scopus (5) Google ScholarPacing to maintain physiologic ventricular activation is recommended in patients with AV nodal block and an LV ejection fraction of 36%–50% if the ventricular pacing burden is expected to be >40% (class IIa indication). There are no current guideline recommendations for conduction system pacing in patients with preserved LV systolic function.8Kusumoto F.M. Schoenfeld M.H. Barrett C. et al.2018 ACC/AHA/HRS Guideline on the Evaluation and Management of Patients With Bradycardia and Cardiac Conduction Delay: Executive Summary: A Report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines, and the Heart Rhythm Society.Circulation. 2019; 140: e333-e381PubMed Google Scholar Randomized controlled trials are warranted to explore the effects of conduction system pacing on diastolic function and to determine the potential therapeutic benefits for heart failure patients with preserved ejection fraction.9Infeld M. Wahlberg K. Cicero J. et al.Personalized pacing for diastolic dysfunction and heart failure with preserved ejection fraction: design and rationale for the myPACE randomized controlled trial.Heart Rhythm O2. 2021; 3: 109-116Abstract Full Text Full Text PDF PubMed Scopus (1) Google Scholar We present 5 consecutive patients with AV block and preserved LV systolic function experiencing disabling exertional intolerance presumed to be related to chronic RVP and diastolic dysfunction. Owing to lack of other therapeutic alternatives, we upgraded their conventional dual-chamber pacing system to a CRT-pacemaker with a His bundle pacing lead. This enabled us to compare echocardiographic parameters of overall cardiac function and diastolic dysfunction during RVP and HBP at optimized AV interval settings. It is impressive that despite normal LV systolic function, the LV stroke volume, a measure of overall cardiac function, increased by 13%, and the diastolic filling time increased by 11%, accompanied by improved septal early diastolic myocardial relaxation velocity (E′). In 4 out of 5 of our patients with symptomatic heart failure with preserved ejection fraction, conduction system pacing resulted in a remarkable improvement of heart failure symptoms. The acute impact of HBP on diastolic function has not been reported in patients with preserved LV function, although it has been demonstrated in patients with reduced ejection fraction.7Kato H. Yanagisawa S. Sakurai T. et al.Efficacy of His bundle pacing on LV relaxation and clinical improvement in HF and LBBB.JACC Clin Electrophysiol. 2022; 8: 59-69https://doi.org/10.1016/j.jacep.2021.06.011Crossref PubMed Scopus (5) Google Scholar Pacing to maintain physiologic ventricular activation is recommended in patients with AV nodal block and an LV ejection fraction of 36%–50% if the ventricular pacing burden is expected to be >40% (class IIa indication). There are no current guideline recommendations for conduction system pacing in patients with preserved LV systolic function.8Kusumoto F.M. Schoenfeld M.H. Barrett C. et al.2018 ACC/AHA/HRS Guideline on the Evaluation and Management of Patients With Bradycardia and Cardiac Conduction Delay: Executive Summary: A Report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines, and the Heart Rhythm Society.Circulation. 2019; 140: e333-e381PubMed Google Scholar Randomized controlled trials are warranted to explore the effects of conduction system pacing on diastolic function and to determine the potential therapeutic benefits for heart failure patients with preserved ejection fraction.9Infeld M. Wahlberg K. Cicero J. et al.Personalized pacing for diastolic dysfunction and heart failure with preserved ejection fraction: design and rationale for the myPACE randomized controlled trial.Heart Rhythm O2. 2021; 3: 109-116Abstract Full Text Full Text PDF PubMed Scopus (1) Google Scholar