第一部分

室间隔基底段形态在肥厚型心肌病患者左心室流出道梗阻中的作用

背景 室间隔基底段（Basal Septum，BS）形态的详细评估对于理解左心室流出道（Left Ventricular Outflow Tract，LVOT）梗阻的形态学机制至关重要。我们发现在一组肥厚型心肌病（Hypertrophic Cardiomyopathy, HCM）患者中，BS肥厚程度相同，但LVOT梗阻（Left Ventricular Outflow Tract Obstruction，LVOTO）的发生情况不一。本研究旨在分析HCM患者BS形态及其周围结构的改变，并探讨其在LVOTO中的作用。

方法 回顾性分析105例HCM患者【64例梗阻性（Hypertrophic Obstructive Cardiomyopathy, HOCM）和41例非梗阻性（Hypertrophic Non-obstructive Cardiomyopathy, HNOCM）】以及28例健康对照组的超声心动图数据。采用一种新的测量方法来定量评估BS形态。测量并比较了HOCM、HNOCM和对照组之间的IVSa（BS凸向到LVOT的面积）、L_A（BS凸向LVOT的最大距离）、L_B（垂直于L_A方向的IVSa长度）和S-IVSa（IVSa除以L_B得到的标化值）。测量二尖瓣前叶、后叶（Anterior Mitral Leaflet，AML；Posterior Mitral Leaflet，PML）的长度以及二尖瓣环平面与升主动脉之间的夹角（the Mitral Annular Plane and Ascending Aorta，MV-AO夹角）。

结果 HOCM和HNOCM患者的BS最大厚度无显著差异（P > 0.999）。在三组中，AML和PML的长度、MV-AO夹角、IVSa、L_A、L_B和S-IVSa均有显著差异（P < 0.05）。与HNOCM患者相比，HOCM患者的AML和PML明显冗长，MV-AO夹角增加，IVSa、L_A和S-IVSa增大（P < 0.05）。在多因素回归分析中，AML冗长、MV-AO夹角增大、IVSa增大和S-IVSa增大与LVOTO相关【比值比（95%可信区间）：0.649（0.462-0.911）、0.842（0.768-0.923）、1.025（1.001-0.049）和0.276（0.101-0.754）；P < 0.05】。

结论 BS相对于LVOT的形态学改变可为评估是否存在LVOTO提供价值。AML冗长、MV-AO夹角增大、IVSa增大和S-IVSa增大与LVOTO相关。新测量方法可帮助定量评估室间隔基底段的形态，为未来进一步探究外科手术治疗HOCM的策略提供理论基础。

第二部分

基于静息超声心动图参数检测肥厚型心肌病患者的隐匿性梗阻

背景 超声心动图诊断肥厚型心肌病（Hypertrophic Cardiomyopathy，HCM）患者左心室流出道（Left Ventricular Outflow Tract Obstruction，LVOT）梗阻常需要特定的激发试验。我们旨在探讨与隐匿性梗阻性HCM相关的静息超声心动图参数。

方法 分析138例HCM患者（静息梗阻性65例，隐匿性梗阻性38例，非梗阻性35例）的超声心动图数据。在静息状态下，测量并比较三组室间隔基底段（Basal Septum，BS）形态参数【IVSa（BS凸向LVOT的面积）、L_A（BS凸向LVOT的最大距离）、L_B（垂直于L_A方向的IVSa长度）和S-IVSa（IVSa除以L_B得到的标化值）】、二尖瓣环平面与升主动脉之间的夹角（the Mitral Annular Plane and Ascending Aorta，MV-AO夹角）和常规超声心动图参数。对隐匿性梗阻性及非梗阻性患者进行进一步分析。使用多因素Logistic回归分析和受试者工作特征（Receiver Operating Characteristic，ROC）曲线评估参数与隐匿性梗阻之间的关联。

结果 MV-AO夹角、L_A、S-IVSa、二尖瓣后叶长度和异常肌束的存在在隐匿性梗阻性及非梗阻性患者中存在显著差异。在多因素分析中，MV-AO夹角、异常肌束的存在和S-IVSa与隐匿性梗阻独立相关。由这些参数所组成模型的ROC曲线显示与隐匿性梗阻有更强的关联，ROC曲线下面积为0.954（95%置信区间：0.878-0.989）。MV-AO夹角＞142.7°、S-IVSa＞5.9 mm及异常肌束的存在对检测隐匿性梗阻的灵敏度为92.1%，特异度为91.4%。

结论 将静息状态下评估的S-IVSa、MV-AO夹角和异常肌束相结合，可以有效识别隐匿性梗阻的患者，使新模型成为提高隐匿性梗阻检出率及使更多患者受益的有价值的工具。

第三部分

肥厚型心肌病合并严重左心室流出道梗阻患者的室间隔基底段形态及其在改良扩大室间隔切除术后的变化

背景 目前鲜有研究对肥厚型心肌病（Hypertrophic Cardiomyopathy，HCM）患者室间隔基底段（Basal Septum，BS）形态的定量评估。本研究旨在区分HCM合并严重左心室流出道（left ventricular outflow tract，LVOT）梗阻患者超声心动图特征及其在扩大室间隔切除术后的变化。

方法 根据LVOT压差，将118例确诊为HCM的患者分为组1（压差≥50 mmHg）和组2（压差＜50 mmHg）。采用新的测量方法评估BS形态，获得IVSa（BS凸向LVOT的面积）、L_A（BS凸向LVOT的最大距离）、L_B（垂直于L_A方向的IVSa长度）和S-IVSa（IVSa除以L_B得到标化值）。44例患者在扩大室间隔切除术后进行了超声心动图随访。

结果 两组患者BS厚度差异无统计学意义（P＞0.05）。组1的二尖瓣前叶及后叶长度、二尖瓣瓣环平面与升主动脉之间的夹角（the Angle Between the Mitral Annular Plane and Ascending Aorta，MV-AO夹角）、IVSa、S-IVSa和L_A均显著大于组2（P＜0.05）。组1存在异常肌束的比例较高（P＜0.05）。在多因素分析中，L_A、S-IVSa、前叶长度、MV-AO夹角以及存在异常肌束与严重LVOT梗阻相关。行改良扩大室间隔切除后，所有超声心动图特征均改善（P＜0.05）。

结论 对BS形态的评估比单纯评估厚度更为重要。PG≥50 mmHg的发生与多种因素相关。改良扩大室间隔切除后，BS形态特征得到改善。

Part 1

Morphology of hypertrophied basal septum contributes to left ventricular outflow tract obstruction in patients with hypertrophic cardiomyopathy

Background: Detailed assessment of basal septal morphology is essential for understanding the morphological mechanism of left ventricular outflow tract (LVOT) obstruction. We encountered a subset of hypertrophic cardiomyopathy (HCM) cases with a consistent degree of basal septal hypertrophy but with varied LVOT obstruction (LVOTO) occurrence. We aimed to analyze the morphological alterations of the basal septum (BS) and its surrounding structures and explore their role in LVOTO in patients with HCM.

Methods: We retrospectively reviewed echocardiographic data sets from 105 consecutive patients with HCM (64 obstructive [HOCM] and 41 non-obstructive [HNOCM]) and 28 healthy controls. A novel measurement method was used to quantitatively assess BS morphology. The IVSa (the area of the BS protruding into the LVOT), L_A (the largest distance of the BS protruding into the LVOT), L_B (IVSa length in the direction perpendicular to the L_A), and S-IVSa (IVSa divided by L_B) were measured and compared among the HOCM, HNOCM, and controls. We measured the length of the anterior and posterior mitral leaflets (AML and PML) and the angle between the mitral annular plane and ascending aorta (MV-AO angle).

Results: There was no significant difference in the maximal basal septal thickness between the HOCM and HNOCM patients (P > 0.999). Among the three groups, there were significant differences in the length of the AML and PML, MV-AO angle, IVSa, L_A, L_B, and S-IVSa (P < 0.05). Compared with HNOCM patients, HOCM patients had significantly longer AML and PML, an increased MV-AO angle, and larger IVSa, L_A, and S-IVSa (P < 0.05). In the multivariate analysis, a longer AML, an increased MV-AO angle, a larger IVSa, and a larger S-IVSa were associated with LVOTO (odds ratio [95% confidence interval]: 0.649 [0.462–0.911], 0.842 [0.768–0.923], 1.025 [1.001–1.049], and 0.276 [0.101–0.754], respectively; P <0.05).

Conclusions: Morphological alterations of the BS relative to the LVOT may provide additional value for estimating the extent of LVOTO. An elongated AML, an increased MV-AO angle, a large IVSa, and a large S-IVSa were associated with LVOTO.

Part 2

Detection of latent obstruction in patients with hypertrophic cardiomyopathy using parameters derived from resting echocardiography

Background: Diagnosis of left ventricular outflow tract (LVOT) obstruction in hypertrophic cardiomyopathy (HCM) by echocardiography requires specific provocation tests. We aimed to explore the echocardiographic parameters (under resting conditions) associated with latent obstruction in patients with HCM.

Methods: Echocardiographic data of 138 patients (65 with resting obstruction, 38 with latent obstruction, and 35 without obstruction) with HCM were analyzed. Under the resting condition, parameters of basal septal morphology [IVSa (area of basal septum protruding into the LVOT), L_A (depth of IVSa relative to the LVOT), L_B (length of IVSa in the direction of the left ventricular long axis), and S-IVSa (IVSa divided by L_B)], the angle between the mitral annular plane and ascending aorta (MV-AO angle), and routine echocardiographic parameters were measured and compared among the three groups. Further analyses were conducted on patients with and without latent LVOT obstruction. Associations between parameters and latent obstruction were assessed using multivariate logistic regression analysis and receiver operating characteristic (ROC) curves.

Results: The MV-AO angle, L_A, S-IVSa, length of the posterior mitral leaflet, and presence of abnormal muscle bundles (MBs) were significantly different between patients with and without latent obstruction. In multivariate analyses, the MV-AO angle, presence of abnormal MBs, and S-IVSa were independently associated with latent obstruction. The ROC curves of the model consisting of these parameters showed a stronger association with latent obstruction; the area under the ROC curve was 0.954 (95% confidence interval [CI], 0.878–0.989). The combination of MV-AO angle > 142.7°, S-IVSa > 5.9 mm and the presence of abnormal MBs showed a sensitivity and specificity of 92.1% and 91.4% for detecting latent obstruction.

Conclusions: Combining S-IVSa with the MV-AO angle and abnormal MBs evaluated at rest can effectively identify patients with provocable obstruction, making the new model a valuable tool for improving the detection rate of latent obstruction and benefiting more patients.

Part 3

Basal septal morphology and its changes after extended septal myectomy in patients with hypertrophic cardiomyopathy with severe left ventricular outflow tract obstruction: an echocardiographic study

Background: Quantitatively assessment of basal septal (BS) morphology in patients with hypertrophic cardiomyopathy (HCM) is rare. We are aimed to distinguish the echocardiographic characteristics and its changes after septal myectomy (SM) in patients with HCM with severe left ventricular outflow tract (LVOT) obstruction.

Methods: According to the LVOT pressure gradient (PG), 118 patients diagnosed with HCM were divided into Group 1 (≥ 50 mmHg) and Group 2 (< 50 mmHg). A novel method was used to evaluate BS morphology to obtain the IVSa (the area of the BS protruding into the LVOT), L_A (the largest distance of the BS protruding into the LVOT), L_B (IVSa length in the direction perpendicular to the L_A), and S-IVSa (IVSa divided by L_B). Forty-four patients underwent follow-up echocardiography after SM.

Results: BS thickness was comparable between the two groups (P > 0.05). The anterior and posterior mitral leaflets (AML and PML) lengths, the angle between the mitral annular plane and ascending aorta (MV-AO angle), IVSa, S-IVSa, and L_A were significantly larger in Group 1(P < 0.05). The presence of abnormal muscle bundles (MBs) was higher in Group 1 (P < 0.05). In the multivariate analysis, increased L_A, S-IVSa, AML length, MV-AO angle, as well as the presence of abnormal MBs were associated with severe LVOT obstruction. After SM, all echocardiographic characteristics improved (P < 0.05).

Conclusions: Evaluation of the morphology of the BS is more important than thickness alone. The occurrence of PG ≥ 50 mm Hg is related to various factors. Following SM, the morphological characteristics of BS improved, which provides new thought for SM.