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Representative images of the preoperative echocardiography (A), surgical specimens (B), and postoperative echocardiography (C) of HCM patients without and with muscle bundles. (A1-3) No muscle bundle, BMB originating from the basal septum, and muscle bundle originating from the mid-septum. (B1-3) Corresponding surgical specimen removed from IVS. (C1-3) Corresponding echocardiography demonstrating no BMB postoperatively. The yellow arrows indicate muscle bundles; red arrow, origin point of the muscle bundles; green line, mitral valve tip plane; and red box in C1-3, scope of surgical resection. AO, ascending aorta; LA, Left atrium; LV, left ventricle; RV, right ventricle.
Source publication
Aims
Many factors cause left ventricular outflow tract obstruction (LVOTO) in hypertrophic cardiomyopathy (HCM). Previous studies reported that left ventricular basal muscle bundle (BMB) may be associated with LVOTO. We aimed to evaluate the role of BMB in LVOTO by echocardiography.
Methods and results
Two hundred fifty-six patients diagnosed wi...
Context in source publication
Context 1
... second challenge was the lack of knowledge about BMB; more practice was needed. The reasons for falsepositive echocardiographic diagnosis of BMB were (i) accessory APM directly inserted into anterior mitral leaflet; (ii) abnormal thickened chordae tendineae; and (iii) ultrasonic artefact (Supplementary data online, Figure S2). It was sometimes challenging to distinguish BMB from abnormal chordae, especially for thin muscle bundles. ...
Citations
... Amongst obstructive HCM patients, those with worse LA stiffness (E/e′ to LA reservoir strain ratio) ≥ 0.41 had a higher probability of clinical deterioration requiring septal reduction therapy. The study by Xiao et al. 6 included 256 HCM patients and reported that an LV basal muscle bundle is a common echocardiographic feature in HCM and a risk factor for LV outflow tract obstruction, together with other morphological features (enlarged septum, an elongated anterior mitral leaflet with a smaller distance from its free margin and the septum, and a larger mitral-aorta angle). This particular structural abnormality needs to be recognized, as it has important implications for the choice of septal reduction therapy and may be one of the reasons for failure of alcohol septal ablation. ...
The European Heart Journal—Cardiovascular Imaging with its over 10 years existence is an established leading multi-modality cardiovascular imaging journal. Pertinent publications including original research, how-to papers, reviews, consensus documents, and in our journal from 2022 have been highlighted in two reports. Part I focuses on cardiomyopathies, heart failure, valvular heart disease, and congenital heart disease and related emerging techniques and technologies.
... The mechanism of LVOTO in patients with HCM was more complex than it initially seemed. The integration of various factors may responsible for the occurrence of LVOTO: narrowing of the left ventricular outflow tract (LVOT) resulting from the hypertrophied interventricular septum (IVS), abnormalities of mitral valve (MV) apparatus, and abnormal submitral apparatus [such as anomalous MV leaflets and papillary muscle (PM), abnormal muscle bundles (MBs)] give rise to systolic anterior motion (SAM) and LVOTO (5)(6)(7)(8). Septal hypertrophy is one of the major characteristics of HCM, and the thickness ≥30 mm is associated with sudden cardiac death (9). The main reasons for LVOTO were attributed to septal hypertrophy and SAM (10). ...
... A single muscular band crossing the LV cavity without chordae attached to the MV, but extended from the BS to the PM or apex was defined as abnormal MBs. MBs can be detected in the PLAX, LV short-axis views, A3C, and A4C (6). ...
... The prevalence of apical MBs in patients with mild septal hypertrophy has been demonstrated to be consistent with that in patients with evident septal hypertrophy. Researchers revealed that basal MBs, integrating with the hypertrophied IVS, increased MV-AO angle, and longer AML, may narrow the LVOT and lead to SAM by bringing the IVS/MBs closer to AML (6). In our study, we found that abnormal MBs were more common in patients with HOCM than in those with HNOCM, which is consistent with previous findings. ...
Background:
Detailed assessment of basal septal morphology is essential for understanding the morphological mechanism of left ventricular outflow tract (LVOT) obstruction. We aimed to analyze the morphological alterations of the basal septum (BS) and its surrounding structures and explore their role in LVOT obstruction (LVOTO) in patients with hypertrophic cardiomyopathy (HCM).
Methods:
During January 2019 and December 2019, 239 patients were diagnosed with HCM at Fuwai Hospital. We retrospectively reviewed echocardiographic data sets from 105 consecutive patients with HCM [64 with hypertrophic obstructive cardiomyopathy (HOCM) and 41 with hypertrophic non-obstructive cardiomyopathy (HNOCM)] and 28 healthy controls. For quantitatively assessing the basal septal morphology, a novel measurement method was used to obtain the IVSa (the area of the BS protruding into the LVOT), LA (the largest distance of the BS protruding into the LVOT), LB (IVSa length in the direction perpendicular to the LA), and S-IVSa (IVSa divided by LB). Echocardiographic parameters associated with LVOTO were analyzed using multivariable logistic regression analyses.
Results:
There was no significant difference in the maximal basal septal thickness between the HOCM and HNOCM patients (P>0.99). Among the three groups, there were significant differences in the length of the anterior and posterior mitral leaflets (AML and PML), the angle between the mitral valve orifice and ascending aorta (MV-AO) angle, IVSa, LA, LB, and S-IVSa (all P<0.001). Compared with HNOCM patients, HOCM patients had significantly longer AML and PML, as well as larger MV-AO angle, IVSa, LA, and S-IVSa (P<0.001, P<0.001, P<0.001, P=0.002, P<0.001, and P=0.03, respectively). In the multivariate analysis, AML, MV-AO angle, IVSa, and S-IVSa were associated with LVOTO {odds ratio (OR) [95% confidence interval (CI)]: 0.649 (0.462-0.911), P=0.01; 0.842 (0.768-0.923), P<0.001; 1.025 (1.001-1.049), P=0.04; and 0.276 (0.101-0.754), P=0.01, respectively}.
Conclusions:
Morphological alterations of the BS relative to the LVOT may provide additional value for estimating the extent of LVOTO. The length of AML, MV-AO angle, IVSa, and S-IVSa were associated with LVOTO.
... Standard echocardiography was used to help measure an instantaneous peak Doppler LVOT pressure gradient at rest. LVOT obstruction was defined as an LVOT gradient of 30 mm Hg or greater at rest or after being provoked by physiologic exercise (25). The maximal LVWT and left atrial diameter were collected. ...
Background Myocardial fibrosis contributes to adverse cardiovascular events in hypertrophic cardiomyopathy (HCM). Purpose To explore the characteristics of cardiac fibroblast activation protein inhibitor (FAPI) PET/CT imaging and its relationship with the risk of sudden cardiac death (SCD) in HCM. Materials and Methods In this prospective study from July 2021 to January 2022, participants with HCM and healthy control participants underwent cardiac fluorine 18 (18F)-labeled FAPI PET/CT imaging. Myocardial FAPI activity was quantified as intensity (target-to-background uptake ratio), extent (the percent of FAPI-avid myocardium of the left ventricle [LV]), and amount (the percent of FAPI-avid myocardium of LV × target-to-background ratio). Regional wall thickness was analyzed at cardiac MRI. The 5-year SCD risk score was calculated from the 2014 European Society of Cardiology guidelines. Univariable and multivariable linear regression analyses were used to identify factors related to the FAPI amount. The correlation between FAPI amount and 5-year SCD risk was explored. Results Fifty study participants with HCM (mean age, 43 years ± 13 [SD]; 32 men) and 22 healthy control participants (mean age, 45 years ± 17; 14 men) were included. All participants with HCM had intense and inhomogeneous cardiac FAPI activity in the LV myocardium that was higher than that in healthy control participants (median target-to-background ratio, 8.8 vs 2.1, respectively; P < .001). In HCM, more segments with FAPI activity were detected than the number of hypertrophic segments (median, 14 vs five, respectively; P < .001); 84% of nonhypertrophic segments showed FAPI activity. Log-transformed FAPI amount had a positive relationship with log-transformed N-terminal probrain natriuretic peptide, high-sensitive troponin I, and left atrial diameter and a negative relationship with LV ejection fraction z-score. Degree of FAPI activity positively correlated with the 5-year SCD risk score (r = 0.32; P = .03). Conclusion Fibroblast activation protein inhibitor (FAPI) PET/CT imaging indicated intense and heterogeneous activity in hypertrophic cardiomyopathy, and FAPI uptake was associated with 5-year risk of sudden cardiac death. © RSNA, 2022 Online supplemental material is available for this article.
... 8,9 Cardiologists have to be grateful to the cardiac surgeons since through direct inspection during myectomy, surgeons have at first raised the suspicion that MBs might contribute to left ventricular outflow tract obstruction (LVOTO) in HOCM and, thus, should be resected. 7, 10 Xiao et al. 11 describe echocardiographic and cMRI findings of patients with hypertrophic cardiomyopathy and how MBs might contribute to the development of LVOTO. In their study, comprising 256 patients, were 178 (70%) with MBs detected by echocardiography. ...
... Compared to patients without MBs, patients with MBs had a higher left ventricular outflow tract gradient. 11 Septal myectomy was carried out in 139 (54%) of these patients, and MBs were identified in 120 (86%) patients during surgery. For diagnosis of presence or absence of MBs, the sensitivity, specificity, positive and negative predictive value, and accuracy of detection by echocardiography were optimal (98%, 82%, 98%, 88%, and 96%, respectively). ...
... The accuracy of cMRI was superior to echocardiography in visualizing a special type of MBs which extend from the interventricular septum to the anterior papillary muscle. 11 What are the clinical implications of the findings of Xiao et al.? In the guidelines of the European Society of Cardiology (ESC), septal reduction therapy to improve symptoms is recommended as Class I evidence level B in patients with a resting or maximum provoked left ventricular outflow tract gradient of > 50 mmHg, who are in NYHA functional Class III-IV, despite maximum tolerated medical therapy. 12 According to the ESC guidelines, 'the choice of therapy should be based on a systematic assessment of the mitral valve and septal anatomy that includes deliberate exclusion of other left ventricular outflow tract and mitral valve abnormalities requiring surgical treatment'. ...
This editorial refers to ‘Left ventricular basal muscle bundle in hypertrophic cardiomyopathy: insights into the mechanism of left ventricular outflow tract obstruction’ by M. Xiao et al., https://doi.org/10.1093/ehjci/jeab200.
Filaments of tissue crossing the cavity of the left ventricle were first reported in 1893.¹ Although these structures are hardly mentioned in the textbooks of anatomy and cardiac pathology, the development of imaging methods like echocardiography, computed tomography (CT) or cardiac magnetic resonance imaging (cMRI) has awakened interest in them. These structures are termed ‘ventricular bands’, ‘false tendons’, ‘muscle bundles’, or ‘trabeculations’.2–5 On morphological inspection at autopsy, these structures are found in 46–48% hearts from patients of all ages with congenital heart disease, acquired heart disease, or normal hearts.4,5 The clinical importance of these structures is considered as low, with the possible exception of their suggested role as a source of innocent systolic murmurs and pitfalls in the interpretation of echocardiographic images.5,6 Presence or absence of these structures, termed ‘muscle bundles’ (MBs), is not mentioned in routine echocardiographic reports.
Background:
Mitral annular calcification (MAC) is a risk factor for cardiac surgery, but there is limited study on the prognosis value and the impact for valve function of MAC based on computed tomography (CT) diagnosis after myectomy for hypertrophic obstructive cardiomyopathy (OHCM).
Methods:
Consecutive OHCM patients underwent septal myectomy were compared according to the existence of MAC and its severity in preoperative CT scans. The survival data were evaluated and compared by Kaplan Meier analysis and log rank test. Cox regression analysis was used to evaluate the impact of MAC on endpoint events.
Results:
From the entire cohort of 1035 patients, 10.8% had MAC. In multivariate regression, female (OR = 2.23), age (OR = 1.07), aortic annular calcification (OR = 2.52), aortic calcification (OR = 2.56), systolic anterior motion of the mitral valve (SAM) (OR = 0.42), mitral valve thickening (OR = 2.13), and tricuspid regurgitation (OR = 3.12) were independent predictors of MAC. All-cause mortality (3.57% vs. 1.08%, p = 0.031), major adverse cardiovascular and cerebrovascular events (MACCE) (23.32% vs. 13.65%, p = 0.014), recurrent MR > 2+ (8.04% vs. 2.49%, p = 0.001) and NYHA III-IV (11.61% vs. 5.53%, p = 0.012) were more frequent in OHCM patients with MAC after myectomy. MAC was discovered to be an independent predictor of postoperative recurrent MR > 2+ after other risk factors were taken into account (HR 2.47, 95% CI 1.08-5.67, p = 0.0329). Moderate-to-severe MAC was an independent risk factor (HR 2.03, 95% CI 1.09-3.75, p = 0.0244) for long-term major adverse cardiovascular and cerebrovascular events (MACCE).
Conclusion:
MAC was detected in one-tenth of OHCM patients in preoperative CT scanning and is mainly associated with aging and atherosclerosis. OHCM patients with MAC had a worse prognosis and more recurrent mitral valve regurgitation than those without MAC after septal myectomy.
Purpose of review:
Whilst abnormally increased left ventricular wall thickness is the hallmark feature of hypertrophic cardiomyopathy (HCM), anomalies of the mitral valve and supporting apparatus are well documented. This review addresses the clinical importance of mitral valve abnormalities in HCM, their mechanistic associations with symptoms, and therapeutic strategies targeting mitral valve and apparatus abnormalities.
Recent findings:
The normal mitral valve possesses anatomical features facilitating unrestricted blood flow during LV filling, preventing regurgitation during LV systole, and avoiding obstruction of LV ejection. In HCM, a variety of structural and functional abnormalities can conspire to cause deranged mitral valve function, with implications for management strategy. Identification and characterization of these abnormalities is facilitated by multimodality imaging. Alcohol septal ablation (ASA) cannot address primary mitral valve abnormalities, and so is not preferred to surgical intervention if mitral valve abnormalities are present and are judged to make dominant contributions to LV outflow tract obstruction (LVOTO). Two broadly opposing surgical intervention strategies exist, one advocating isolated septal myectomy and the other including adjuvant mitral apparatus modification. Newer, less invasive surgical and transcatheter techniques will expand interventional options.
Summary:
Mitral valve abnormalities are a central pathological feature of HCM. Multimodality imaging is crucial for their identification and characterization prior to therapeutic intervention.
Hypertrophic cardiomyopathy (HCM) is the most common genetic cardiovascular disease, is characterized by unexplained hypertrophy of any myocardial segment, and has a prevalence of 0.2% to 0.5% among the general population. As one of the phenotypes of HCM, left ventricular outflow tract obstruction (LVOTO) is associated with high morbidity and mortality, including cardiac death. The integration of various factors, including septal hypertrophy, malformation of the mitral valve apparatus, and an anomalous mitral subvalvular apparatus, may contribute to the occurrence of LVOTO. Previous studies have thoroughly discussed the role of the mitral valve in the mechanisms of systolic anterior motion (SAM) and LVOTO. Recent studies have shown the importance of determining the potential mechanism of the submitral apparatus in inducing SAM and LVOTO. We aim to review the recent advances in knowledge regarding the submitral apparatus of HCM patients.
