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Dynamic Changes of Distinct Compartmental LV Remodeling Following Septal Myectomy in Hypertrophic Obstructive
Xinyi Luo1, Guanyu Lu2, Ziyu Liu3
1Department of Radiology (X.L., Y.C., J.O., R.C., H.L., Y.Y.), Guangdong Provincial People's Hospital (Guangdong Academy of Medical Sciences), Southern Medical University, Guangzhou, China.
Insights
Septal myectomy significantly reduces left ventricular mass index (LVMi) in hypertrophic obstructive cardiomyopathy patients. Early reduction involves cellular and extracellular changes, with sustained extracellular remodeling over 24 months.
Area of Science:
- Cardiology
- Cardiovascular Surgery
- Biomedical Imaging
Background:
- Hypertrophic obstructive cardiomyopathy (HOCM) is characterized by increased left ventricular mass index (LVMi).
- Septal myectomy is a surgical intervention for HOCM, leading to LVMi regression.
- The precise dynamics and mechanisms of LVMi regression post-myectomy remain incompletely understood.
Purpose of the Study:
- To investigate the temporal changes in LVMi, cellular volume, and extracellular volume after septal myectomy in HOCM patients.
- To identify factors associated with LVMi regression following the surgical procedure.
Main Methods:
- Prospective study of 27 HOCM patients undergoing septal myectomy.
- Cardiac MRI performed preoperatively and at 6, 12, and 24 months postoperatively.
- Analysis of LVMi, indexed cellular volume, and indexed extracellular volume using repeated measures ANOVA and linear regression.
Main Results:
- Significant LVMi decrease from baseline (105.76±25.22 g/m²) to 76.22±23.93 g/m² at 24 months (P<0.05).
- Early regression (first 6 months) driven by both cellular (23.70%) and extracellular (18.40%) volume reduction.
- From 12-24 months, extracellular volume continued to decline (P<0.001), while cellular volume stabilized.
- Greater reduction in left ventricular outflow tract pressure gradient correlated with LVMi regression (β=0.157; P=0.001).
Conclusions:
- Early LVMi reduction post-myectomy involves both cellular and extracellular compartments.
- Slower, sustained regression of extracellular volume occurs between 12 and 24 months, indicating myocardial adaptability to afterload reduction.
- The degree of left ventricular outflow tract pressure gradient reduction is a key factor associated with LVMi regression after septal myectomy.
Background:
In hypertrophic obstructive cardiomyopathy, left ventricular mass index (LVMi) regresses following septal myectomy, but the specific dynamics, mechanisms (involving cellular and extracellular compartments), and related factors remain unclear.
Methods:
This prospective study included patients with hypertrophic obstructive cardiomyopathy who underwent septal myectomy. Cardiac magnetic resonance imaging was performed preoperatively and at 6, 12, and 24 months postoperatively. LVMi, indexed cellular volume, and indexed extracellular volume were analyzed using repeated measures ANOVA. Factors associated with LVMi regression, postoperatively, were identified using linear regression.
Results:
The study included 27 patients (53.70±13.85 years; 17 female). LVMi significantly decreased from 105.76±25.22 g/m2, preoperatively, to 82.52±25.90 g/m2 at 6 months, postoperatively, further declining to 78.86±24.73 g/m2 at 12 months and 76.22±23.93 g/m2 at 24 months (P<0.05). The average percent decrease in LVMi from baseline was 22.97% at 6 months, 26.26% at 12 months, and 28.58% at 24 months postoperatively. This regression is primarily driven by indexed cellular volume regression (23.70%), with a smaller reduction in the indexed extracellular volume (18.40%) in the first 6 months. Both compartments exhibited sustained reductions through 12 months. But from 12 to 24 months, only indexed extracellular volume continued to decline (from 22.13±6.76 to 20.89±6.25 mL/m2; P<0.001). Greater left ventricular outflow tract pressure gradient reduction (β=0.157; P=0.001) was associated with LVMi regression after septal myectomy.
Conclusions:
In patients with hypertrophic obstructive cardiomyopathy postseptal myectomy, early LVMi reduction involves both cellular and extracellular compartments, with slower reduction from 12 to 24 months, mainly driven by the extracellular component. This demonstrates rapid myocardial adaptability to afterload relief, with slower extracellular matrix remodeling. Greater left ventricular outflow tract pressure gradient reduction was associated with greater LVMi regression after surgery.
Registration:
URL: https://www.chictr.org.cn; Unique identifier: ChiCTR2100043699.
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