INTRODUCTION
Hypertrophic cardiomyopathy (HCM) is characterized by left ventricular hypertrophy in the absence of aortic valve stenosis or chronic hypertension[ 1 , 2 ] . The HCM can be divided based on the site of hypertrophy (eg, basal, mid-ventricular, apical, or diffuse)[ 3 ] . Alternatively, HCM can be divided based on the presence or absence of left ventricular outflow tract (LVOT) obstruction. HCM patients with LVOT obstruction (hypertrophic obstructive cardiomyopathy [HOCM]) are associated with symptoms of severe heart failure, angina, syncope, and an increased risk of sudden cardiac death[ 4 ] .
Percutaneous transluminal septal myocardial ablation (PTSMA) is increasingly used to manage HOCM due to several important advantages, including minimal traumatic damage, significant reduction of LVOT gradient (LVOGT), and improvement of diastolic function. The current ESC and AHA guidelines recommend PTSMA in patients with resting LVOTG at ≥ 30 mmHg or provoked LVOTG at ≥ 50 mmHg[ 5 , 6 ] . In the European-alcohol septal ablation (Euro-ASA) registry study, HOCM patients with an interventricular septal thickness (IVST) at ≤ 16 mm had a high rate of early complications after PTSMA[ 7 ] . In studies by Veselka et al [ 8 , 9 ] , poor long-term survival was associated with an IVST at > 30 mm and post-PTSMA LVOTG at ≥ 30 mmHg.
Higher IVST tends to be associated with higher LVOTG, but a small variation in the location of the involved myocardium may lead to a large variance in LVOT gradient. A model that combines the use of both IVST and LVOTG, thus, may improve prognostic performance in patients receiving PTSMA for HOCM[ 10 ] . We conducted a retrospective analysis to examine the predictive performance of the IVST/LVOTG product (IVST × LVOTG; referred to as thickness gradient, TG below). Results are reported below.
METHODS
Patients selection
This retrospective analysis included consecutive patients receiving PTSMA for HOCM during a period from 2010 to 2020 at the following centers: the First Affiliated Hospital of the University of Science and Technology of China, the First Affiliated Hospital of Anhui Medical University, the Second Affiliated Hospital of Anhui Medical University, and the Fourth Affiliated Hospital of Anhui Medical University. For inclusion in the analysis, the following conditions must be met: dyspnea of New York Heart Association (NYHA), a history of angina, recurrent exercise-induced presyncope or syncope, resting LVOTG at ≥ 30 mmHg or ≥ 50 mmHg upon provocation (Valsalva maneuver or post-extra systolic potentiation).
The study was conducted in accordance with the Declaration of Helsinki (as revised in 2013) and approved by ethics board of the First Affiliated Hospital of University of Science and Technology of China (USTC) (NO. 2021-BE(H)-070; October 2021). Due to the retrospective nature of the study, informed consent was waived by above ethics board of the First Affiliated Hospital of USTC.
Percutaneous transluminal septal myocardial ablation
PTSMA was conducted after careful evaluation by a multidisciplinary team, as described previously[ 11 , 12 ] . Blood samples were obtained in the 24 hours post-PTSMA to determine the cardiac infarction of creatine kinase-MB (CK-MB) and troponin-I.
Term definitions
The 30-day major cardiovascular adverse events consisted of permanent pacemaker implantation, electrical defibrillation for ventricular tachycardia/ventricular fibrillation, sudden cardiac death or cardiac tamponade, and an appropriate International Classification of Diseases (ICD) discharge. The severity of dyspnea was based on the NYHA classification.
Follow-up
The HOCM patients underwent a first noninvasive follow-up and cardiac echocardiography at 3–6 months post-PTSMA. Afterward, the routine cardiac examination was performed either in our hospital or by the other cardiologists. The follow-up was conducted with either clinical visits or telephone calls, and the information was updated in 2020–2021.
Statistical analysis
The R software 3.6.5 (Lucent Technologies, USA) and SPSS 17.0 (SPSS Inc., Chicago, USA) were used for statistical analysis. All descriptive statistics were dichotomized using the median level of LVOTG, IVST, and TG as the cutoff. Continuous variables were analyzed using the Student t test and shown as means ± standard deviation. Categorical variables were analyzed using the chi-square test or Fisher exact test, as appropriate. Cox proportional hazards regression was used to identify risk factors for all-cause mortality. The variable included in the modeling included echocardiography-based measures, sex, age, body mass index (BMI), alcohol drinking, smoking, intraoperative alcohol dose, and preoperative NYHA grade). The results of the regression analysis are shown as hazard ratio (HR) and its 95% confidence interval (CI). The inverse probability weights method was used for the regression using the RISCA (one of the package of software entitled “Causal Inference and Prediction on Cohort-Based Analysis”) statistical package of R software.
RESULTS
Baseline characteristics
The final analysis included 284 adult HOCM patients (54.80 ± 11.98 years of age, 152 women) (Table 1 ). The basal IVST was 20.75 ± 4.56 mm. LVOTG at rest was 78.58 ± 22.30 mmHg. The comparison of baseline clinical and echocardiographic characteristics in the study cohort is shown in Table 1 . The rates for patients with atrial fibrillation (AF) in the LVOTG ≤ 82 mmHg and > 82 mmHg groups were 16% and 4%, respectively. There was a higher prevalence of AF in HOCM patients with higher LVOTG (P = 0.005). When striped group by either LVOTG or IVST, no difference was found in the prevalence of angina, syncope, NYHA class, and left ventricular ejection fraction (LVEF) value. When stripped by the TG index, also no significant difference was observed in the prevalence of angina, syncope, NYHA class, and LVEF between the two groups. However, patients in the TG ≤ 1,683 and > 1,683 groups showed significant differences in both LVOTG (64.25 ± 21.9 vs 93.31 ± 9.38 mmHg; P < 0.001) and IVST (18.44 ± 4.17 vs 23.11 ± 3.66 mm; P < 0.001). Interestingly, patients with thicker IVST or bigger TG index were accompanied by smaller left ventricular end diameter (LVED).
Table 1 -
Comparative analysis of preoperative baseline characteristics of HOCM patients
Factors
Overall
LVOTG ≤82 mmHg
LVOTG >82 mmHg
P value
IVST ≤20 mm
IVST >20 mm
P value
TG index ≤1,683
TG index >1,683
P value
Age, y
54.8 ± 12.0
53.7 ± 12.1
55.9 ± 11.8
0.182
55.9 ± 11.5
53.7 ± 12.4
0.192
53.8 ± 11.8
55.8 ± 12.2
0.219
Sex, male
132 (46.5)
68 (47.9)
64 (45.1)
0.634
60 (42.3)
72 (50.7)
0.153
64 (45.1)
68 (47.9)
0.634
Smoking history
32 (11.3)
12 (8.5)
20 (14.1)
0.133
16 (11.3)
16 (11.3)
1.000
8 (5.6)
24 (16.9)
0.007
Drinking history
20 (7.0)
8 (5.6)
12 (8.5)
0.354
8 (5.6)
12 (8.5)
0.354
4 (2.8)
16 (11.3)
0.005
Hypertension
116 (40.8)
56 (39.4)
60 (42.3)
0.629
68 (47.9)
48 (33.8)
0.033
60 (42.3)
56 (39.4)
0.629
Diabetes
28 (9.9)
20 (14.1)
8 (5.6)
0.017
12 (8.5)
16 (11.3)
0.426
20 (14.1)
8 (5.6)
0.017
BMI, kg/m2
25.0 ± 4.0
25.6 ± 4.3
24.4 ± 3.7
0.035
25.5 ± 4.4
24.5 ± 3.6
0.082
25.7 ± 4.0
24.4 ± 4.0
0.017
Atrial fibrillation
20 (7.0)
16 (11.3)
4 (2.8)
0.005
12 (8.5)
8 (5.6)
0.354
12 (8.5)
8 (5.6)
0.354
Chest pain
63 (20.1)
31 (21.3)
32 (22.9)
0.886
35 (24.8)
28 (20.0)
0.317
37 (25.9)
26 (18.1)
0.116
NYHA class
II
28 (9.9)
12 (8.5)
16 (11.4)
0.338
12 (8.5)
16 (11.4)
0.338
12 (8.5)
16 (11.4)
0.338
III
244 (85.9)
126 (88.7)
118 (83.1)
126 (88.7)
118 (83.1)
126 (88.7)
118 (83.1)
IV
12 (4.2)
4 (2.8)
8 (5.6)
4 (2.8)
8 (5.6)
4 (2.8)
8 (5.6)
Syncope, %
44 (15.5)
28 (19.4)
16 (11.4)
0.049
28 (19.4)
16 (11.4)
0.049
20 (13.9)
24 (17.1)
0.512
Basal LVOTG at rest, mmHg
78.6 ± 22.3
60.3 ± 17.0
97.4 ± 3.7
<0.01
76.6 ± 22.2
80.6 ± 22.4
0.199
64.3 ± 21.9
93.3 ± 9.4
<0.001
Basal IVST, mm
20.8 ± 4.6
20.4 ± 4.4
21.1 ± 4.7
0.247
17.3 ± 2.9
24.3 ± 3.0
<0.001
18.4 ± 4.2
23.1 ± 3.7
<0.001
LAD, mm
46.5 ± 6.7
46.0 ± 7.2
47.0 ± 6.2
0.280
44.8 ± 6.2
48.3 ± 6.9
<0.001
45.8 ± 6.8
47.3 ± 6.6
0.116
LVED, mm
45.6 ± 4.8
45.3 ± 5.0
45.9 ± 4.5
0.312
47.2 ± 4.4
44.0 ± 4.5
<0.001
46.5 ± 5.2
44.7 ± 4.1
0.008
LVEF, %
67.5 ± 7.9
68.0 ± 7.1
66.9 ± 8.6
0.308
68.1 ± 6.5
66.8 ± 9.0
0.250
67.7 ± 6.6
67.2 ± 9.0
0.657
Data are expressed as n (%) or mean ± SD as appropriate.
BMI: Body mass index; HOCM: Hypertrophic obstructive cardiomyopathy; IVST: Interventricular septum thickness; LAD: Left atrial diameter; LVED: Left ventricular end diameter; LVEF: Left ventricular ejection fraction; LVOTG: Left ventricular obstruction tract gradient; NYHA: New York Heart Association; SD: Standard deviation; TG: IVS thickness × LVOT gradient.
Early complications post-PTSMA
No significant difference was found in the early occurrences of sudden cardiac death and other types of complications (electrical defibrillation, cardiac tamponade, and ICD discharge) (Table 2 ). However, patients with IVST ≤ 20 mm or the TG index ≤ 1,683 had a higher incidence of complications, which were driven by a higher rate of a permanent pacemaker.
Table 2 -
Comparative analysis of last clinical check-up characteristics of patients post-PTSMA
Factors
Overall
LVOTG ≤82 mmHg
LVOTG >82 mmHg
P value
IVST ≤20 mm
IVST >20 mm
P value
TG index ≤1,683
TG index >1,683
P value
NYHA class
I
4 (1.4)
4 (2.8)
0 (0)
0.043
4 (2.8)
0 (0)
<0.001
4 (2.8)
0 (0)
<0.001
II
232 (81.7)
118 (82.5)
115 (81.0)
126 (88.7)
106 (74.7)
129 (90.8)
103 (72.5)
III
44 (15.5)
21 (14.7)
23 (16.2)
12 (8.5)
32 (22.5)
9 (6.3)
35 (24.7)
IV
4 (1.4)
0 (0)
4 (2.8)
0 (0)
4 (2.8)
0 (0)
4 (2.8)
LVOTG at rest, mmHg
40.1 ± 24.4
34.7 ± 23.5
45.6 ± 24.2
0.001
33.3 ± 25.6
47.4 ± 21.0
<0.001
33.8 ± 22.9
46.5 ± 24.4
<0.001
IVS thickness, mm
17.7 ± 4.1
17.8 ± 3.7
17.6 ± 4.5
0.695
15.7 ± 2.8
19.8 ± 4.2
<0.001
16.5 ± 3.7
18.8 ± 4.1
<0.001
LAD, mm
42.9 ± 7.2
43.1 ± 7.8
42.7 ± 6.5
0.666
41.3 ± 6.4
44.6 ± 7.6
0.001
42.5 ± 7.3
43.3 ± 7.1
0.472
LVED, mm
44.7 ± 3.9
44.9 ± 4.0
44.6 ± 3.8
0.670
45.8 ± 4.1
43.7 ± 3.3
<0.001
45.5 ± 4.3
43.9 ± 3.3
0.003
LVEF, %
70.6 ± 6.0
69.2 ± 6.1
71.8 ± 5.6
0.002
70.2 ± 5.1
70.9 ± 6.7
0.408
69.7 ± 5.6
71.4 ± 6.2
0.031
Alcohol volume, mL
2.2 ± 1.0
2.2 ± 1.1
2.2 ± 0.89
0.825
2.3 ± 1.2
2.1 ± 0.8
0.410
2.0 ± 1.1
2.4 ± 0.9
0.015
Decrease of LVOTG, mmHg
38.8 ± 28.8
25.7 ± 26.6
51.8 ± 24.8
<0.001
43.4 ± 30.9
33.9 ± 25.7
0.017
30.7 ± 30.0
46.9 ± 25.2
<0.001
Reduction of IVST, mm
3.0 ± 3.3
2.4 ± 3.0
3.5 ± 3.4
0.008
1.6 ± 1.7
4.5 ± 3.9
<0.001
1.6 ± 1.8
4.3 ± 3.8
<0.001
CKMB, IU/L
133.4 ± 74.2
140.7 ± 86.3
126.0 ± 59.2
0.153
124.5 ± 82.6
142.7 ± 63.3
0.074
137.5 ± 87.2
129.2 ± 58.6
0.422
Troponin I, ng/mL
12.1 ± 5.8
10.7 ± 5.7
13.5 ± 5.5
0.003
12.0 ± 5.9
12.2 ± 5.7
0.832
10.9 ± 5.8
13.2 ± 5.5
0.016
Data are expressed as n (%) or mean ± SD as appropriate.
CK-MB: Creatine kinase MB; IVS: Interventricular septum; IVST: Interventricular septum thickness; LAD: Left atrial diameter; LVED: Left ventricular end diameter; LVEF: Left ventricular ejection fraction; LVOTG: Left ventricular obstruction tract gradient; NYHA: New York Heart Association; PTSMA: Percutaneous transluminal septal myocardial ablation; SD: Standard deviation; TG: IVS thickness × LVOT gradient.
Clinical and echocardiographic characteristics at the last clinical check-up post-PTSMA
At the last clinical check-up post-PTSMA, LVOTG was reduced from 78.58 ± 22.30 to 40.11 ± 24.44 mmHg (P < 0.001), and IVST was reduced from 20.75 ± 4.56 to 17.68 ± 4.07 mmHg (P < 0.001) (Table 3 ). There was no significant difference in the usage of total alcohol dose among different groups. Also, the increase of serum CK-MB within 24 hours after PTSMA did not differ among the different groups.
Table 3 -
In-hospital cardiac events after PTSMA
Outcomes
LVOTG ≤82 mmHg
LVOTG >82 mmHg
P value
IVST ≤20 mm
IVST >20 mm
P value
TG index ≤1,683
TG index >1,683
P value
Pacemaker implantation
13 (9.2)
8 (5.6)
0.257
20 (14.1)
1 (0.7)
<0.001
17 (12.0)
4 (2.8)
0.003
Other complications
2 (1.4)
4 (2.8)
0.680
3 (2.1)
3 (2.1)
1.000
2 (1.4)
4 (2.8)
0.680
Sudden cardiac death
3 (2.1)
1 (0.7)
0.615
3 (2.1)
1 (0.7)
0.615
3 (2.1)
1 (0.7)
0.615
Patients with IVST ≤20 mm or the TG index ≤1,683 had a higher incidence of complications, which were driven by a higher rate of a permanent pacemaker. The R software was used for statistical analysis.
IVST: Interventricular septum thickness; LVOTG: Left ventricular obstruction tract gradient; other complications: Electrical defibrillation for ventricular tachycardia/ventricular fibrillation: cardiac tamponade, and International Classification of Diseases discharge; PTSMA: Percutaneous transluminal septal myocardial ablation; TG: IVS thickness × LVOT gradient.
In the LVOTG subgroup, there was a parallel decrease in the IVS thickness and LVOTG. However, a higher reduction of IVS thickness (4.45 ± 3.87 vs 1.58 ± 1.65 mm; P = 0.017) in the IVST > 20 mm group but less decrease of LVOT gradient (33.88 ± 25.65 vs 43.36 ± 30.87 mmHg; P < 0.001) was observed in the IVST ≤ 20 mm group. In the TG index subgroup, still, there was a parallel reduction in the IVS thickness and LVOT gradient (4.29 ± 3.77 mm and 46.86 ± 25.19 mmHg, each) after PTSMA.
Long-term outcomes
None of the patients was lost to follow-up. Within the mean follow-up of 4.24 ± 2.17 years (903 patient-years), a total of 21 (9.8%) deaths occurred. The number per 100 patient-years was 1.27 and 3.49 in high versus low LVOTG groups, respectively; 1.97 and 2.59 in the high versus low IVST groups, respectively; 0.65 and 4.06 in the high versus low TG groups, respectively.
All-cause mortalities are shown in Figure 1 . The 5-year OS rate in the high versus low LVOTG groups was 86.02% (95% CI = 78.83%–90.05%) versus 90.78% (95% CI = 85.48%–92.10%; log-rank P = 0.578), respectively. The 8-year all-cause mortality in the high versus low LVOTG groups was 54.35% (95% CI = 45.38%–63.95%) versus 74.40% (95% CI = 66.09%–79.32%; log-rank P < 0.001), respectively. Patients in the high IVST group tended to have lower survival as compared to the low IVST group (HR = 2.82, 95% CI = 0.90–8.85). The 5-year OS rate was 80.79% (95% CI = 74.99%–86.66%) versus 88.95% (95% CI = 83.83%–93.68%; log-rank P = 0.134) in the high versus low TG groups, respectively. The 8-year OS rate was 48.95% (95% CI = 39.07%–57.75%) versus 82.63% (95% CI = 74.99%–86.66%; log-rank P < 0.001) in the high versus low TG groups, respectively.
Figure 1.: Kaplan-Meier curves of LVOTG, IVST, and TG index. A , Kaplan-Meier curves describing survival from cardiovascular mortality events in patients with residual LVOTG. B , Kaplan-Meier curves describing survival from cardiovascular mortality events in patients with IVST. C , Kaplan-Meier curves describing survival from cardiovascular mortality events in patients with TG index (adjustment for age, sex, baseline LVOTG, and baseline septum thickness).IVST: Interventricular septum thickness; LVOTG: Left ventricular outflow tract gradient; TG: IVS thickness × LVOT gradient.
In the multivariate analysis, the predictor of all-cause mortality included NYHA class (HR = 4.804, 95% CI = 1.064–21.689; P = 0.041), baseline LVOTG before PTSMA (HR = 5.607, 95% CI = 1.206–26.054; P = 0.028), and TG index (HR = 5.725, 95% CI = 1.551–21.128; P = 0.009). The greater NYHA class, the baseline LVOTG and TG index before PTSMA, the higher the incidence of all-cause time to death in the postoperative period.
Subgroup analysis
In the analysis that included only patients with high IVST, the risk of all-cause mortality is higher in patients with high versus low LVOTG (HR = 18.63, 95% CI = 1.09–319.15) (Tables 4 and 5 ). In the analysis that included only patients with low IVST, the risk of all-cause mortality did not differ in patients with high versus low LVOTG. In the subgroup analysis that included only patients with high LVOTG, the risk of all-cause mortality was higher in patients with high versus low IVST (HR = 15.31, 95% CI = 2.12–110.75). In the subgroup analysis that included only patients with low LVOTG, the risk of all-cause mortality did not differ in patients with high versus low LVOTG.
Table 4 -
Cox proportional hazard regression analysis on the association of LVOTG with all-cause mortality in IVST subgroups
Group
IVST ≤20 mm
P value
IVST >20 mm
P value
LVOTG ≤82 mmHg
Reference
Reference
LVOTG >82 mmHg
1.11 (0.20–6.19)
0.904
18.63 (1.09–319.15)
0.044
Adjusted factors: age, sex, BMI, alcohol drinking, smoking, total alcohol dose, NYHA classification.
BMI: Body mass index; IVST: Interventricular septum thickness; LVOTG: Left ventricular obstruction tract gradient; NYHA: New York Heart Association.
Table 5 -
Cox proportional hazard regression analysis on the association of IVST with all-cause mortality in LVOTG subgroups
Group
LVOTG ≤82 mmHg
P value
LVOTG >82 mmHg
P value
IVST ≤20 mm
Reference
Reference
IVST >20 mm
0.91 (0.04–21.35)
0.955
15.31 (2.12–110.75)
0.007
Adjusted factors: age, sex, BMI, alcohol drinking, smoking, total alcohol dose, NYHA classification.
BMI: Body mass index; IVST: Interventricular septum thickness; LVOTG: Left ventricular obstruction tract gradient; NYHA: New York Heart Association.
DISCUSSION
The results from the current study showed an association between a high TG index (the product of baseline IVS thickness and LVOT gradient at rest) with poor outcomes in HOCM patients. Specific findings include: (i) PTSMA is effective in decreasing LVOTG and improving cardiac function. (ii) Patients with thinner IVST (≤20 mm) had greater LOVTG reduction but more acute complete conduction block. (iii) There was no statistically significant difference in long-term outcomes regardless of IVS thickness in this study. (iv) Patients with a lower TG index had lower all-cause mortality. (v) Patients with both high IVST and high LVOTG had the lowest long-term survival.
The median preoperative IVST (20 mm) and LVOTG at rest (82 mmHg) in the current study were consistent with the study by Batzner et al [ 13 ] and the Euro-ASA registry[ 14 ] . The first check-up LVOTG post-PTSMA in the current study (40.11 ± 24.44 mmHg) was also consistent with previous studies[ 13 , 15–18 ] . The low rate of short-term cardiac sudden death post-PTSMA (<1%) regardless of LVOGT, IVST, and TG index was also consistent with previous reports[ 14 ] . The patients with low IVST had a higher rate of complete conduction block (13.89% vs 0.95%; P < 0.001); this result was similar to the Euro-ASA registry but the cutoff of IVST was higher (20 mm) in our study[ 19 ] .
Past studies have associated high alcohol injection doses with early complications, including conduction problems, cardiac sudden death, and ventricular septal defect[ 6 , 14 , 19–21 ] . Veselka et al [ 15 ] , however, failed to show an association between alcohol dose with either short- or long-term outcomes in a study of 1,440 HOCM patients. The total alcohol volume (2.201 ± 1.025 mL) in the current study was almost identical to that reported by previous studies[ 13 , 15 ] . We found lower alcohol dosage in patients with low TG index (2.033 ± 1.116 vs 2.374 ± 0.894; P < 0.015); these patients had a high rate of permanent pacemaker implantation driven by complete heart block (12.04% vs 2.86%). The potential bias by different alcohol dosage was included in the multivariate regression analysis.
In the current study, PTSMA reduced LVOTG from a preoperation level of 78.58 ± 22.30 to 40.11 ± 24.44 mmHg (P < 0.001) and improved cardiac function from NYHA class preoperation level of 2.94 ± 0.37 to 2.17 ± 0.45 In the Euro-ASA registry study, patients with mild hypertrophy had better long-term survival[ 19 ] . In a study by Jensen et al [ 22 ] , patients with baseline IVST > 25 mm had a 5-fold increased risk of all-cause mortality compared with patients with baseline IVST ≤ 20 mm. We found a trend for poorer survival in the patients with high IVST (>20 mm), but the 5-year OS was similar regardless of baseline IVST. Several factors may have contributed to such a discrepancy. First, patients with IVST > 20 mm had a higher reduction of IVST but smaller LVOTG reduction after PTSMA with the same alcohol dosage. Second, the cutoff IVST in the current study (20 mm) was higher than reported by previous studies.
The most important finding in the current study is the markedly higher 8-year OS rate in patients with low TG index (≤1,683) (82.63%) versus in patients with high TG index (>1,683 group) (48.95%). TG was also associated with the magnitude of reduction of both LVOTG and IVST after PTSMA. In the study by Veselka et al [ 9 ] , LVOTG ≥ 30 mmHg upon the first postdischarge check-up was a strong predictor for the occurrence of subsequent cardiovascular mortality events. Thus, baseline IVST should not be considered the only factor to evaluate the long-term outcomes in the HOCM patients post-PTSMA. These results seem to indicate that the TG index is a better indicator of long-term prognosis in HOCM undergoing PTSMA.
Limitations
This study has several limitations. First, it is a retrospective and therefore subject to inherent biases. Second, the sample size is relatively small. Third, diversities exist in the interpretation and implementation of the existing evidence on PTSMA, for example, patient selection, and myectomy as an alternative method, and these patients were treated by tertiary center cardiologists specializing in HOCM[ 23 ] . Fourth, we did not compare PTSMA with other treatment modalities. Further studies with large sample sizes are needed to verify the performance of the TG index as a measure of long-term risk and to compare different treatment modalities.
FUNDING
This work was supported by the National Natural Science Foundation of China (81870192, 82170263), the National Key Research and Development Program of China (2021YFA0804904), and the Natural Science Foundation of Anhui Province, China (2208085MH197).
AUTHOR CONTRIBUTIONS
ML and JP are responsible for the study concepts and design, literature research, experimental studies, data analysis and analysis, statistical analysis, and manuscript preparation. HS and LM are responsible for the study concepts, literature research, data acquisition, and manuscript editing. JP is responsible for the guarantor of integrity of the entire study, study concepts and design, definition of intellectual content, clinical studies, data acquisition and acquisition, manuscript editing, and review. All authors read and approved the final manuscript.
CONFLICTS OF INTEREST STATEMENT
The authors declare that they have no conflict of interest with regard to the content of this manuscript.
DATA SHARING STATEMENT
Research data will be available to other researchers upon request to the corresponding author.
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