Pulmonary Atresia with Intact Ventricular Septum: Correlation of Preoperative Computed Tomography-Derived Parameters with Echocardiographic Tricuspid Valve Z-Score and Surgical Outcomes.

The role of preoperative cardiac computed tomography (CT) in neonates with pulmonary atresia and intact ventricular septum (PA-IVS) remains unclear. This study was aimed to elaborate the role of preoperative CT-derived anatomical and functional findings in planning treatment strategies in neonates with PA-IVS. The presence of ventriculocoronary arterial connections was evaluated by CT. CT-derived ventricular volumetric parameters were compared and correlated with echocardiographic tricuspid valve (TV) z-score in 12 neonates with PA-IVS. Cardiac CT and echocardiographic findings were compared between definite surgical types (median follow-up, 4 years). Ventriculocoronary arterial connections were identified with CT in 58.3% of cases (7/12) and associated with higher incidence of Fontan procedure (42.9%, 3/7) and high mortality (28.6%, 2/7). The CT-derived and echocardiographic TV z-scores exhibited a high correlation (R = 0.924, p < 0.001). The CT-derived right ventricle (RV) volume and RV-left ventricle volume ratio also displayed high correlations (R = 0.875 and 0.867, respectively; p < 0.001) with echocardiographic TV z-score. More positive echocardiographic TV z-score, high CT-derived RV end-diastolic volume and RV-left ventricle volume ratio, and low CT-derived left ventricular end-diastolic volume were observed in biventricular surgery group (N = 2), compared to Fontan operation (N = 3) and 1.5 ventricular surgery (N = 3) groups, and mortality cases (N = 3). Preoperative CT-derived coronary artery anatomy and ventricular volumetric parameters may supplement treatment planning in neonates with PA-IVS especially when multifactorial decision including echocardiographic TV z-score is in a gray zone.W.

Pulmonary Atresia with Intact Ventricular Septum, a National Comparison Between Interventional and Surgical Approach, in Combination with a Systemic Literature Review.

This study aimed to compare long-term morbidity in patients with pulmonary atresia with intact ventricular septum (PA-IVS) treated with catheter-based intervention (group A) versus those undergoing heart surgery (group B) as initial intervention. Additionally, we conducted a systematic literature review on PA-IVS treatment. All neonates born in Sweden with PA-IVS between 2007 and 2019 were screened for inclusion. The inclusion criterion was decompression of the right ventricle for initial intervention. Medical records were reviewed, as well as the initial preoperative angiogram, and the diagnostic echocardiogram. Comparisons between groups were performed with Mann-Whitney U-test and Fisher´s exact test. A systematic literature review of original studies regarding treatment of PA-IVS (2002 and onward) was conducted following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines, to assess the outcomes of patients with PA-IVS. 34 (11 females) patients were included, 18 in group A and 16 in group B. There was no mortality in either group. Follow-up time ranged from 2 to 15 years (median 9). All attempted perforations in group A were successful, and 16 out of 18 patients reached biventricular circulation. In the surgical group 15 out of 16 patients reached biventricular circulation. The literature review presented heterogeneity in standards for treatment. This retrospective population-based multicenter study demonstrates that both catheter-based intervention and heart surgery are safe procedures. Our results are comparable to, or exceed, those in the systematic literature review. The systematic literature review displays a great heterogeneity in study design, with no definitive golden standard treatment.

Performance and failure of right ventricle to pulmonary artery conduit in congenital heart disease.

INTRODUCTION: Surgical implantation of a right ventricle to pulmonary artery (RV-PA) conduit is an important component of congenital heart disease (CHD) surgery but with limited durability leading to re-intervention. Current single-center, retrospective, cohort study is reporting results of surgically implanted RV-PA conduits in a consecutive series of children and adults with CHD. METHODS: Patients with CHD referred for RV-PA conduits surgical implantation (October 1997 and January 2022) have been included. Primary outcome was conduit failure defined as peak gradient above 64mmHg/severe regurgitation/need for conduit-related interventions. Longitudinal echocardiographic studies were available for mixed-effect linear regression analysis. RESULTS: Two-hundred and fifty-two patients were initially included. One hundred and forty-nine patients were elegible for follow-up data collection. After a median follow-up time of 49 months the primary study endpoint occurred in 44 (29%) patients. Multivariable Cox regression model identified adult age (>18 years) at implantation and pulmonary homograft as protective factors (HR 0.11, 95% CI 0.02-0.47 and HR 0.34, 95% CI 0.16-0.74, respectively). Fever within 7 days of surgical conduit implantation was a risk factor for early (within 24 months) failure (OR 4.29, 95% CI 1.41-13.01). Longterm use of oral anticoagulant was independently associated with slower progression of peak echocardiographic gradient across conduits (mixed effect linear regression p-value 0.027). CONCLUSION: In patients with CHD, surgically implanted RV-PA conduit failure is faster in children and after non-homograft conduit implantation. Early fever after surgery is a strong risk factor for early failure. Longterm anticoagulation seems to exert a protective effect.

Comparison of Ductal Stent Versus Surgical Shunt as Initial Intervention for Neonates with Pulmonary Atresia with Intact Ventricular Septum.

Data comparing surgical systemic-to-pulmonary artery shunt and patent ductus arteriosus (PDA) stent as the initial palliation procedure for patients with pulmonary atresia with intact ventricular septum (PA-IVS) are limited. We sought to compare characteristics and outcomes in a multicenter cohort of patients with PA-IVS undergoing surgical shunts versus PDA stents. We retrospectively reviewed neonates with PA-IVS from 2009 to 2019 in 19 United States centers. Bivariate comparisons and multivariable logistic regression analysis were performed to determine the relationship between initial palliation strategy and outcomes including major adverse cardiovascular events (MACE): stroke, mechanical circulatory support, cardiac arrest, or death. 187 patients were included: 38 PDA stents and 149 surgical shunts. Baseline characteristics did not differ statistically between groups. Post-procedural MACE occurred in 4 patients (11%) with PDA stents versus 38 (26%) with surgical shunts, p = 0.079. Overall, the initial palliation strategy was not significantly associated with MACE (aOR:0.37; 95% CI,0.13-1.02). In patients with moderate-to-severe right ventricle hypoplasia, PDA stents were significantly associated with decreased odds of MACE (aOR:0.36; 95% CI,0.13-0.99). PDA stents were associated with lower vasoactive inotrope scores (median 0 versus 5, p < 0.001), greater likelihood to be extubated at the end of their procedure (37% versus 4%, p < 0.001), and shorter duration of mechanical ventilation (median 24 versus 96 h, p < 0.001). PDA stents were associated with significantly more unplanned reinterventions for hypoxemia compared to surgical shunts (42% vs. 20%, p = 0.009). In this multicenter study, neonates with PA-IVS who underwent PDA stenting received less vasoactive and ventilatory support postoperatively compared to those who had surgical shunts. Furthermore, patients with the most severe morphology had decreased odds of MACE.

Human Genetics of Ventricular Septal Defect.

Ventricular septal defects (VSDs) are recognized as one of the commonest congenital heart diseases (CHD), accounting for up to 40% of all cardiac malformations, and occur as isolated CHDs as well as together with other cardiac and extracardiac congenital malformations in individual patients and families. The genetic etiology of VSD is complex and extraordinarily heterogeneous. Chromosomal abnormalities such as aneuploidy and structural variations as well as rare point mutations in various genes have been reported to be associated with this cardiac defect. This includes both well-defined syndromes with known genetic cause (e.g., DiGeorge syndrome and Holt-Oram syndrome) and so far undefined syndromic forms characterized by unspecific symptoms. Mutations in genes encoding cardiac transcription factors (e.g., NKX2-5 and GATA4) and signaling molecules (e.g., CFC1) have been most frequently found in VSD cases. Moreover, new high-resolution methods such as comparative genomic hybridization enabled the discovery of a high number of different copy number variations, leading to gain or loss of chromosomal regions often containing multiple genes, in patients with VSD. In this chapter, we will describe the broad genetic heterogeneity observed in VSD patients considering recent advances in this field.

Echocardiographic features of a giant aneurysm of membranous ventricular septum.

We describe the echocardiographic features of a 22-year-old female with a giant aneurysm of membranous ventricular septum (AMVS). Both transthoracic echocardiography (TTE) and transesophageal echocardiography (TEE) demonstrated significant dilatation of the aortic annulus and severe aortic regurgitation. A giant aneurysm was detected extending from a large membranous ventricular septal defect (MVSD) to the anterior surface of the aortic root. Contrast-enhanced CT and three-dimensional CT revealed a giant aneurysm located below the aortic root and connected to the left ventricular outflow tract (LVOT). The diagnosis was confirmed by surgery and postoperative pathological examination.

Anaesthesia management of interventional cardiac catheterisation for pulmonary atresia with intact ventricular septum and critical pulmonary stenosis: a retrospective analysis.

OBJECTIVE: Pulmonary atresia with intact ventricular septum and critical pulmonary stenosis usually have to undergo treatment in the neonatal period. Compared to traditional surgical intervention, catheter-based cardiac interventions may achieve similar or superior outcomes for neonates with pulmonary atresia with intact ventricular septum and critical pulmonary stenosis. However, there is limited literature on anaesthesia techniques, challenges, and risks associated with cardiac catheterisation in this population. METHODS: This article retrospectively analysed the clinical data of pulmonary atresia with intact ventricular septum and critical pulmonary stenosis neonates who were treated with interventional cardiac catheterisation in our hospital from January 2015 to October 2022. Clinical outcomes considered were haemodynamic or pulse oxygen saturation instability, vasoactive requirements, prolonged intubation (>24 h postoperatively), and cardiovascular adverse events. RESULTS: A total of 63 patients met the inclusion criteria. All patients survived the intervention. Among the patients with critical pulmonary stenosis, 40 successfully received percutaneous balloon pulmonary valvuloplasty, while three patients received ductal stenting due to moderate right ventricular dysplasia at the same time. For patients with pulmonary atresia with intact ventricular septum, 17 of the 23 patients successfully underwent percutaneous pulmonary valve perforation and percutaneous balloon pulmonary valvuloplasty. Of these, five patients underwent ductal stenting due to unstable pulmonary blood flow. Three patients only underwent ductal stenting. In addition, three patients received hybrid therapy. CONCLUSIONS: There are various clinical techniques and risk challenges in the interventional cardiac catheterisation of neonatal pulmonary atresia with intact ventricular septum and critical pulmonary stenosis. However, by mastering the physiological and pathophysiological characteristics of the disease, adequately preparing for the perioperative period, and predicting the procedure process and potential complications, anaesthesia and surgical risks can be effectively managed.

A case report of pulmonary atresia with intact ventricular septum: an extraordinary finding of subsystemic right ventricle.

Background: Massive tricuspid regurgitation (TR) is the most common feature of pulmonary atresia with intact ventricular septum (PA/IVS), and mild or absent TR is observed in severe right ventricular (RV) dysplasia or RV-to-coronary fistulous connections, resulting in non-biventricular (BV) outcomes postnatally. Case summary: We report a case of fetal severe pulmonary stenosis with IVS diagnosed at 26 weeks of gestation. The severity of RV hypoplasia did not worsen or reach indications for intrauterine intervention, while the jet velocity of TR decreased significantly during pregnancy. The fetus was definitely diagnosed with PA/IVS with mild RV dysplasia after birth. Unusually, the fetus did not experience severe TR and myocardial sinusoids, the TR jet velocity was maintained at 2.0 m/s, and the coronary artery was almost normal. The incapable RV cannot pump blood into pulmonary circulation after RV decompression from valvular perforation and balloon dilation. It may be an extraordinary finding of subsystemic RV. Conclusion: PA/IVS is a heterogeneous disease with various degrees of RV dysplasia. Mild or no baseline TR is a reliable indicator with non-BV outcomes for fetal PA/IVS, even with acceptable dysplasia RV structures.

Epidemiology of Cardiac Myxoma in the Kingdom of Bahrain.

BACKGROUND: Cardiac myxomas (CM) are the most prevalent type of primary cardiac tumour. The majority of primary cardiac tumours, including CM, are found to be benign. In the context of this study, the objective was to investigate and analyse the experience of CM over a period of 10 years, specifically in Bahrain. By examining this particular subset of cardiac tumours, valuable insights can be gained regarding their prevalence, clinical presentation, diagnostic methods, treatment approaches, and outcomes in the Bahraini population. METHODS: We retrospectively evaluated the medical records of 20 patients who presented with CM at the Mohammed bin Khalifa bin Salman Al Khalifa Specialist Cardiac Centre in the Kingdom of Bahrain from January 2010 to January 2021. All patients had transthoracic echocardiography to establish a preoperative diagnosis. All of the patients underwent an operation using the median sternotomy, and a histopathology examination confirmed the final diagnosis. RESULTS: The mean age at the time of presentation was 57 (± 18.1) years, ranging from 17 to 80 years, and 55% (12 patients) were female. Dyspnea (n=8, 40%) and peripheral embolism (n=4, 20%), which include cerebrovascular accidents and acute monocular vision loss, were the most frequently observed symptoms. The largest diameter of the myxoma was 5.1 cm (±1.7). The left atrium was the predominant location for myxoma formation (n=16, 80%), with the majority of the myxomas attached to the atrial septum. CONCLUSION: CM poses a significant risk of cardiac and systemic complications. Early detection and timely gross-complete resection result in excellent early and long-term outcomes.

Pitfalls and tips for lumenless lead extraction inserted deep within the ventricular septum.

Key Clinical Message: This case highlights the pitfalls and provides tips for the extraction of deeply implanted lumenless leads, and encourages careful lead selection in the current era of widespread left bundle branch area pacing. Abstract: The extraction of cardiovascular implantable electronic device leads is sometimes complicated. We describe a case with difficult but successful extraction of SelectSecure, a lumenless permanent pacemaker lead, implanted deep in the ventricular septum, highlighting its pitfalls and tips in the current era of left bundle branch area pacing.

Unguarded Tricuspid Valve and Pulmonary Atresia With Intact Ventricular Septum Complicated With Right Coronary Artery Fistula and Advanced Atrioventricular Block in a Fetus: A Case Report.

The unguarded tricuspid valve is a rare and severe condition. When found in the fetus, they mostly undergo abortion or intrauterine death. The details of the fetal course in such cases are poorly understood. Here, we report a case of an unguarded tricuspid valve detected at 20 weeks of gestation who developed a complete atrioventricular block and survived in utero. The fetus also had pulmonary atresia with intact ventricular septum, Uhl's disease, hypoplastic right ventricle, noncompacted left ventricle, valvular aortic stenosis, and right coronary artery fistula to the right ventricle. Despite this serious condition, the fetal hydrops did not develop. The baby was born at 33 weeks of gestation but died on day two. Our experience suggests that some babies may survive the fetal period even with the severe type of an unguarded tricuspid valve. Hence, efficient fetal and neonatal treatment strategies for fetal unguarded tricuspid valves are crucial.

Percutaneous transient occlusion of the transtricuspid flow: a new method to evaluate the right ventricle-dependent coronary circulation in pulmonary atresia with intact ventricular septum.

Pulmonary atresia with an intact ventricular septum is characterised by heterogeneity in right ventricle morphology and coronary anatomy. In some cases, the presence of ventriculocoronary connections may promote coronary artery stenosis or interruption, and aortic diastolic pressure may not be sufficient to drive coronary blood flow. This requires a correct evaluation (currently done by angiography) which depends on whether the patient can be offered decompression of the right ventricle. To date, there is no objective method to do so, so we designed a percutaneous, transitory technique with the purpose of occluding the transtricuspid anterograde flow. The manoeuverer was performed in a 25-day-old female with pulmonary atresia with intact ventricular septum, right ventricle at suprasystemic level, and selective coronarography was not conclusive, the anterior descendant with stenosis in its middle third and from this point, thinner with to-fro flow. Occlusion was performed with a balloon catheter. We re-evaluated the coronary flow and the normalised anterior descendant flow. We hope that with this new method, we can give a more accurate diagnosis and determine the cases in which the coronary circulation is truly not right ventricle dependent to offer a greater number of patients biventricular or 1.5 ventricular repairs and thereby improve their quality of life and survival, the ones that turn out to be right ventricular dependant; offer them an early reference for cardiac transplant or in case it is not available to consider univentricular palliation knowing that this probably would not reduce the risk of ischaemia and/or death over time.

Ratio of left ventricular outflow tract area to aortic annulus area and complete atrioventricular block after transcatheter aortic valve replacement for aortic stenosis.

BACKGROUND: Mechanical compression of cardiac conduction system by transcatheter heart valves leads to complete atrioventricular block (CAVB) after transcatheter aortic valve replacement (TAVR). Bulging of ventricular septum in the left ventricular outflow tract (LVOT) may be associated with greater compression of conduction system, leading to irreversible CAVB. OBJECTIVE: This study aimed to investigate the association of ventricular septal bulging with TAVR-related CAVB and permanent pacemaker implantation (PPI). METHODS: Among 294 consecutive patients with severe aortic stenosis who underwent TAVR between July 2017 and February 2023, 271 were included in the analysis. As a quantitative evaluation of bulging of the ventricular septum, the ratio of LVOT area to aortic annulus area (L/A ratio) was measured at the systolic phase of computed tomography images. RESULTS: TAVR-related CAVB occurred in 64 patients (23.6%). Twenty-eight patients (10.3%) required PPI. The optimal thresholds of L/A ratio for predicting TAVR-related CAVB and PPI were 1.0181 and 0.985, respectively. Patients with less than the cut-off values had higher rate of TAVR-related CAVB and PPI than those above (28.3% vs 13.1%, p = 0.0063; 14.7% vs 4.4%, p = 0.0077, respectively). A multivariate analysis showed that L/A ratio < 1.0181 was an independent predictor of TAVR-related CAVB (odds ratio [OR] 2.65, p = 0.011), in addition to prior right bundle branch block (OR 3.76, p = 0.0005), use of a self-expanding valve (OR 1.99, p = 0.030), and short membranous septum length (OR 0.96, p = 0.037). Only L/A ratio < 0.985 was independently associated with PPI (OR 3.70, p = 0.011). CONCLUSION: Low L/A ratio is a predictor of TAVR-related CAVB and PPI.

[Right ventricle free wall rupture during transcatheter occluder implantation in a patient with postinfarction rupture of the interventricular septum and COVID-19-associated myocarditis. Case report].

Intraventricular septum rupture is a rare mechanic complication of myocardial infarction associated with high mortality. This case describes STEMI in recovered patient after COVID 19 associated pneumonia, which was complicated by ventricular septum rupture followed by cardiogenic shock. It was managed by percutaneous occluder implantation. The procedure was complicated by right ventricular wall rupture. Postmortem examination of myocardium showed the signs of inflammation infiltrate and myocyte necrosis, according to histopathological Dallas criteria diagnosis of COVID-19 associated myocarditis was established. The COVID-19 pandemic has contributed to increasing cardiovascular mortality. This is typically attributed to diminishing resources for timely and appropriate medical care, and patients' late presentations for fear of contracting the infection. Cardiovascular complication of COVID-19 may be another contributing factor. Further research is needed to improve our understanding of the mechanisms and long-term sequelae of myocardium damage in COVID-19, to optimize treatment strategy and subsequent follow-up in such patients.

Echocardiography: conotruncal anomaly: a case of common arterial trunk with intact ventricular septum and hypoplastic left heart complex with unbalanced pulmonary stenoses.

We describe the echocardiographic findings of a common arterial trunk with intact ventricular septum, mitral and left ventricular hypoplasia, atretic left ventricular outlet and bilateral, and unbalanced pulmonary artery stenoses.

Cardiac magnetic resonance parameters associated with successful conversion from a single ventricular to a one-and-a-half or biventricular circulation in patients with a hypoplastic right ventricle.

BACKGROUND: Some patients with pulmonary atresia with an intact ventricular septum (PA/IVS) or a left ventricle dominant atrioventricular canal defect (LDAVC) with a hypoplastic right ventricle (RV) and univentricular (1 V) circulation may be candidates for conversion to either a complete biventricular (2 V) repair or a one-and-a-half ventricle repair (1.5 V). We sought to identify pre-operative cardiovascular magnetic resonance (CMR) findings associated with successful conversion from 1V to 1.5V or 2V circulation. METHODS: In this single center retrospective study, subjects with PA/IVS or LDAVC and no conotruncal abnormalities were included if they had a 1 V circulation at the time of CMR followed by a surgical intervention intended to convert them to a 1.5 V or 2 V circulation. Conversion failure was defined as any of the following: (1) oxygen saturation < 90% at the most recent follow-up, (2) conversion back to a 1.5 V or 1 V circulation, or (3) death. RESULTS: In the PA/IVS cohort (n = 15, median age 1.32 years), 10 patients underwent surgical conversion to a 1.5 V circulation and 5 to a 2 V circulation. In the attempted 1.5 V group, there were 2 failures, and these cases had a lower RV mass (p = 0.04). In the attempted 2 V group, there was 1 failure, and no CMR parameters were significantly different compared to the successes. Among the successful 2 V group patients, the minimum RV end-diastolic volume (EDV) was 27 ml/m2. In the LDAVC cohort (n = 15, median age 1.0 years), 1 patient underwent surgical conversion to a 1.5 V circulation and 14 patients to a 2 V circulation. In the attempted 1.5 V group, the 1 conversion was a failure and had an RV EDV of 15 ml/m2. In the attempted 2 V group, there were 2 failures, and these cases had a smaller RV:LV stroke volume ratio (p = 0.05) and a lower RV ejection fraction (p = 0.05) compared to the successes. Among the successful 2 V group patients, the minimum RV EDV was 22 ml/m2. CONCLUSIONS: We identified multiple CMR parameters associated with successful conversion from 1 V circulation to 1.5 V or 2 V circulation in patients with PA/IVS and LDAVC. This information may improve patient selection for conversion procedures and encourage larger studies to better define the role of CMR.

Post-myocardial Infarction Ventricular Septal Defect in the Setting of No-Reflow and COVID.

The occurrence of post-myocardial infarction (MI) ventricular septal defect (VSD) is a rare but life-threatening complication. This case report presents a unique case of a 49-year-old female patient with an anterolateral ST-segment elevation MI who underwent percutaneous coronary intervention (PCI) and drug-eluting stent (DES) placement, complicated by a no-reflow phenomenon in the distal left anterior descending artery (LAD) and subsequent development of a hemodynamically significant VSD. Notably, this case occurred during the COVID-19 pandemic, which added to the complexity of the patient's management. The patient's clinical course was further complicated by cardiogenic shock, acute respiratory failure, COVID-19 pneumonia, and gastrointestinal bleeding. Despite these challenges, the patient received prompt treatment and optimal medical management, including the use of vasopressor support, insulin therapy, and bicarbonate infusions. The patient also underwent surgical repair of the VSD at a quaternary center, resulting in a favorable outcome. This case report highlights the increased incidence of mechanical complications, such as VSD, during the COVID-19 pandemic due to delayed presentation and patient concerns about exposure to the virus. It also emphasizes the occurrence of a no-reflow phenomenon during PCI, which can lead to adverse outcomes, including larger infarct size and potential ventricular septal rupture. The case further underscores the importance of multidisciplinary collaboration and early subspecialist involvement in managing complex cases of post-MI VSD.

From Other Journals: A Review of Recent Articles by Our Editorial Team.

In this review, we provide a brief description of recently published articles addressing topics relevant to pediatric cardiologists. This review includes (1) Fetal diagnosis, associated anomalies, and factors affecting outcomes in fetal congenitally corrected transposition of the great arteries (ccTGA), (2) The impact of Fontan-associated liver disease on heart and heart/liver transplant, (3) 1-year outcomes of the Harmony transcatheter pulmonary valve, (4) Risk factors associated with major adverse cardiac events in patients with pulmonary atresia and intact ventricular septum undergoing intervention, and (5) Benefits of pulmonary valve replacement in tetralogy of Fallot patients.

Initial studies on the implanting sites of high and low ventricular septa using leadless cardiac pacemakers.

OBJECTIVE: To study the safety and electrical characteristics of various implanting sites of the Micra pacemaker. METHOD: A total of 15 patients from Beijing Anzhen Hospital, Capital Medical University, were included, who were implanted with Micra leadless pacemakers and allocated to either the high ventricular septum group (eight patients) or the low ventricular septum group (seven patients) based on their individual patient factors and clinical conditions. The baseline of the patients, the implanting area, the electrocardiogram change after implantation, the implantation data, the threshold, R wave, impedance, and the date of the 1-month follow-up were then analyzed. With all of the data, the characteristics of different implantation sites of the Micra pacemaker were determined. RESULTS: Overall, the thresholds were low at implantation and remained stable over the 1-, 3-, 6-month, 1-, 2-, 3-, and 4-year follow-ups. On comparing the two groups, there was no difference in QRS duration at pacing (140.00 [40.00] ms vs. 179.00 [50.00] ms), threshold at implantation (0.38 [0.22] mV vs. 0.63 [1.00] mV), R wave at implantation ([10.85 ± 4.71] V vs. [7.26 ± 2.98] V), or impedance at implantation ([906.25 ± 162.39] Ω vs. [750.00 ± 173.40] Ω). While the difference in QRS duration between the two groups was not significant, the QRS duration of the high ventricular septum group exhibited a reduced tendency compared with that of the low ventricular group. The corrected QT interval during pacing exhibited a significant difference (440.00 [80.00] ms vs. 520.00 [100.00] ms; p < .05). For the 1-, 3-, 6-month, 1-, 2-, 3-, and 4-year follow-ups, there was no difference between the threshold of the high ventricular septum group and that of the low ventricular septum group (p > .05). CONCLUSION: High ventricular septum pacing appears to be a safe site for implantation of the Micra pacemaker. It could entail a shorter QRS duration at pacing and could be more physiological than low ventricular septum pacing.