Extent of Late Gadolinium Enhancement on Cardiac Magnetic Resonance Imaging in Japanese Hypertrophic Cardiomyopathy Patients

Abstract

Background: In addition to the presence of late gadolinium enhancement (LGE) on cardiovascular magnetic resonance (CMR), the extent of LGE is considered clinically important in hypertrophic cardiomyopathy (HCM). We evaluated the extent of LGE on CMR in a large series of Japanese HCM patients.

Methods and Results: CMR was performed in 317 HCM patients (147 male). The extent of LGE was scored as the sum of LGE-positive segments in a left ventricle (LV) 17-segment model. LGE was present in 246 patients (77.6%). LGE was detected in 3.5±3.1 segments on average. When the patients were divided according to maximum wall thickness (mild, <20 mm; moderate, 20–29 mm; severe, ≥30 mm), median LGE score increased as wall thickness increased (mild, 2 vs. moderate, 4 vs. severe, 5; P=0.000). When the patients were divided according to ejection fraction (EF) (reduced, <50%; low-normal, 50–65%; normal, >65%), median LGE score increased as EF decreased (reduced, 7 vs. low-normal, 4 vs. normal, 2; P=0.000). On multivariate analysis, reduced EF (OR, 0.947, P=0.015), pressure gradient <30 mmHg (OR, 0.359, P=0.000) and increased maximum wall thickness (OR, 1.236, P=0.000) were independent factors associated with extensive LGE.

Conclusions: Progression of LGE was related to increased wall thickness, decreased contractility, and reduced intraventricular pressure gradient. (Circ J 2016; 80: 950–957)

Hypertrophic cardiomyopathy (HCM) is the most common of the cardiomyopathies.¹ The recent advent of cardiovascular magnetic resonance (CMR), has facilitated the detailed evaluation of cardiac morphology including the myocardium, valves, and papillary muscle.^2,3 Furthermore, many studies have demonstrated the relationship between late gadolinium enhancement (LGE) on CMR and prognosis.^4–11 Because LGE is observed at a high frequency in asymptomatic HCM, rather than the presence or absence of LGE alone, determination of the proportion of myocardium with LGE (extent of LGE) is important, and a recent report suggested that the extent of LGE may be a predictor of sudden death.¹⁰ Other reports have indicated a relationship between extensive LGE and impaired systolic function, especially in patients with end-stage phase.^12–14

Although CMR is considered a useful examination for HCM, this imaging modality is not easily accessible in Japan. Moreover, recent studies using methods such as T1 mapping to evaluate fibrosis of the myocardium as an alternative to detecting LGE on CMR, have been reported.^15,16 Research on LGE in patients with HCM during the past decade, however, has provided valuable information.

In Japan, the only large-scale study on patients with HCM was the national survey conducted by Matsumori et al in 2002,¹⁷ but CMR was not performed at that time. We conducted a retrospective study on a large number of Japanese patients with HCM at Sakakibara Heart Institute, to examine the extent of LGE on CMR. This report is the first to describe the characteristics of LGE in a large series of HCM patients in Japan.

Methods

Patient Selection

We retrospectively studied 317 HCM patients who underwent CMR with gadolinium enhancement at Sakakibara Heart Institute between January 2008 and May 2015. Use of their clinical data for the retrospective study was explained to the patients, and consent in writing was obtained. HCM was diagnosed in the case of left ventricular (LV) wall thickness ≥15 mm on CMR in the absence of other cardiac or systemic diseases that could account for the hypertrophy. In all subjects, the absence of significant stenotic lesion in coronary artery was confirmed on cardiac catheter or coronary computed tomography. Given that the aim of this study was to investigate LGE in HCM, patients with congenital heart disease and those with a history of coronary angioplasty, coronary bypass surgery, old myocardial infarction, severe valvular disease, heart valve surgery, or percutaneous transluminal septal myocardial ablation or myectomy before CMR were excluded. Patients with renal dysfunction (estimated glomerular filtration rate <30 ml/min/1.73 m²) were also excluded.

Clinical Status

The clinical records of all 317 patients were reviewed, and the clinical findings, medications and echocardiographic characteristics at the time of CMR were extracted. Among the 5 conventional factors of sudden death (family history of sudden death; history of syncope; LV wall thickness ≥30 mm; non-sustained ventricular tachycardia [NSVT]; and low blood pressure during exercise) in HCM patients,¹⁸ low blood pressure during exercise was not included in the analysis because the exercise test was performed in very few study patients. NSVT was defined as heart rate >120 beats/min for >3 consecutive beats. Given that some patients did not undergo Holter electrocardiogram (ECG), NSVT was observed on past ECG records, including monitored ECG.

CMR Protocols and Image Analysis

CMR was performed with a 1.5-T MR scanner (Magnetom Sonata; Siemens Medical Solutions, Erlangen, Germany) using a 6-channel phased-array body and spine coil. All images were acquired using the ECG-gated breath-hold technique. First, steady-state free-precession cine images were acquired in long-axis (2-, 3-, and 4-chamber) and short-axis views covering the LV from base to apex (TR, 56.8 ms; TE, 1.2 ms). Subsequently, LGE images were acquired 10 min after i.v. injection of 0.1 mmol/kg gadodiamide hydrate (Omniscan; Daiichi Sankyo, Tokyo, Japan) in accordance with the standardized CMR protocols,¹⁹ using the inversion recovery technique in identical views (TR, 600 ms; TE, 1.26 ms; TI was individually optimized to null normal myocardial signal using a TI-scout sequence), but it takes a few minutes until the end of LGE imaging.

Two cardiologists and 1 radiologist evaluated late enhancement images for the presence of LGE areas within the LV myocardium for each patient, and the results were obtained via consensus.

The LGE was determined by visual inspection, and if the LGE presence and area were obscure and difficult to determine visually, the aforementioned measurement of signal intensity was applied. The mean signal intensity (and SD) of the normal myocardium was calculated, and a threshold ≥5 SD exceeding the mean was used to define areas of LGE. The extent of LGE was assessed using the LV 17-segment model.²⁰ The extent of LGE was scored on a scale of 0–17, as the sum of the segments in the 17-segment model with LGE. Maximum LV wall thickness was determined by measuring the minimum thickness of the thickest LV myocardium in the cine image at end-diastole.

Echocardiography

Two-dimensional, Doppler, and M-mode echocardiography was performed at rest using standard methods. LV obstruction was defined as peak resting gradient ≥30 mmHg. LV volumes and LV ejection fraction (LVEF) were calculated using the biplane Simpson’s rule from the apical 2-chamber and 4-chamber views.

Statistical Analysis

Data are given as mean±SD, median, or n (%) as appropriate. Differences between medians were analyzed using Mann-Whitney U-test. Frequencies were compared using chi-squared test or Fisher’s exact test, as appropriate. Kruskal-Wallis test was used to compare the extent of LGE across different LVEF subgroups and maximum wall thickness subgroups. Univariate analysis was carried out on the clinical, echocardiographic and CMR variables possibly related to the extent of LGE. For multivariate analysis, those variables with P<0.1 on univariate analysis were entered into the model. Furthermore, logistic regression analysis was performed with stepwise variable selection. P<0.05 was considered to be statistically significant. Analysis was performed using SPSS ver. 20.0.

Results

Clinical Characteristics

Table 1 summarizes the clinical characteristics of the 317 HCM patients. Mean age was 62±17 years. The series consisted of some relatively young-onset HCM patients, and the age distribution was as follows: 15 patients (4.7%) in the teens, 8 patients (2.5%) in the 20 s, 10 patients (3.2%) in the 30 s, 154 patients (48.6%) in the 40–60 s, 113 patients (35.6%) in the 70 s, and 17 patients (5.4%) in the 80 s.

Table 1. HCM Subject Clinical Characteristics (n=317)

Clinical characteristics
Age (years)	62±17
Male	147 (46.4)
Family history of HCM	25 (7.9)
Family history of SCD	37 (11.7)
History of syncope	56 (17.7)
DM	37 (11.7)
NSVT	44 (13.9)
AF	45 (14.2)
NYHA functional class III or IV	63 (19.9)
Medications
β-blocker	235 (74.1)
Aldosterone inhibitors	26 (8.2)
Diuretics	38 (12.0)
Anti-arrhythmics (class III)	14 (4.4)
Anti-arrhythmics (class I)	140 (44.2)
Calcium antagonist	104 (32.8)
ACEi/ARB	75 (23.7)
Echocardiographic characteristics
LVEDV (ml)	87.8±29.4
LVESV (ml)	32.3±15.9
LVEF (%)	63.7±6.3
LAD (cm)	4.2±0.6
Pressure gradient ≥30 mmHg	187 (59.0)
CMR characteristics
Maximum LV wall thickness (mm)	21.3±5.2
Maximum LV wall thickness ≥30 mm	29 (9.1)
LGE	246 (77.6)
LGE score	3.5±3.1

Data given as mean±SD or n (%). ACEi, angiotensin-converting enzyme inhibitors; AF, atrial fibrillation; ARB, angiotensin receptor blockers; CMR, cardiac magnetic resonance imaging; DM, diabetes mellitus; EDV, end-diastolic volume; EF, ejection fraction; ESV, end-systolic volume; HCM, hypertrophic cardiomyopathy; LAD, left atrial diameter; LGE, late gadolinium enhancement; LV, left ventricular; NSVT, non-sustained ventricular tachycardia; NYHA, New York Heart Association; SCD, sudden cardiac death.

Regarding the conventional risk factors of sudden death, family history of sudden death was identified in 37 patients (11.7%), history of syncope in 56 patients (17.7%), NSVT in 44 patients (13.9%), and maximum wall thickness ≥30 mm in 29 patients (9.1%). On analysis of the 4 conventional risk factors (excluding abnormal blood pressure during exercise from the 5 conventional factors), 185 patients (58.4%) had no risk factors; 102 patients (32.2%) had 1 risk factor; 26 patients (8.2%) had 2 risk factors; 4 patients (1.3%) had 3 risk factors; and none of the patients had all 4 risk factors. Atrial fibrillation was observed in 45 patients (14.2%). Regarding medication, 235 patients (74.1%) were taking β-blocker, and 140 patients (44.2%) were prescribed class I anti-arrhythmics. Intraventricular pressure gradient ≥30 mmHg, indicating obstructive HCM, was present in 187 patients (59.0%).

Echocardiographic and CMR Characteristics

When the extent of LGE was scored based on the LV 17-segment model, LGE score ranged from 0 to 16, with a median of 3 and mean±SD of 3.5±3.1. Absence of LGE (score 0) was found in 71 patients (22.4%), while LGE was present in the remaining 246 patients (77.6%; Figure 1A). Figure 1B shows the distribution of LGE in the 17 LV segments. LGE was most frequently detected in the basal septal region, followed by the mid-septal region. In contrast, the frequency was relatively low in the basal inferior-lateral wall.

Figure 1.

(A) Extent and (B) distribution of late gadolinium enhancement (LGE) in the myocardium of the left ventricle (LV). (A) Absence of LGE (score 0) was found in 71 patients (22.4%). (B) LGE was most frequently detected in the basal septal regions. In contrast, the frequency was relatively low in the basal inferior to lateral regions. (The number in each segment represents the percentage of LGE-positive patients in that segment: no. patients with LGE/total no. patients×100%.)

Figure 2A shows the distribution of maximum wall thickness. Patients with maximum wall thickness ≥15 mm were included in this study. The greatest maximum wall thickness was 49 mm, while the median was 20 mm and the mean was 21.3±5.2 mm. Furthermore, thickness ≥30 mm, conventionally considered a risk factor of sudden death, was found in 29 patients (9.1%). Figure 2B shows the sites of maximum wall thickness based on the LV 17-segment model. Maximum wall thickness was most frequently found in the basal septal regions, followed by the mid septal regions, corresponding to the same sites with the highest frequency of LGE (Figure 1B).

Figure 2.

(A) Magnitude of maximum wall thickness and (B) distribution of the sites with maximum wall thickness in the left ventricle (LV). (A) Maximum wall thickness ≥30 mm was found in 29 patients (9.1%). (B) Maximum wall thickness was most frequently found in the basal septal regions. (The number in each segment represents the percentage of patients with maximum wall thickness in that segment: no. patients with maximum wall thickness/total no. patients×100%.)

In the 317 patients, LVEF ranged from 27.9% to 76.8%, with a median of 64.8% and mean of 63.7±6.3% (Figure 3). LV contraction is considered to be normal in most HCM patients. In this series, LVEF was <50% in 10 patients (3.2%), 50–65% in 48 patients (15.1%), and >65% in 259 patients (81.7%; Figure 3).

Figure 3.

Distribution of the left ventricular ejection fraction (LVEF). LVEF <50% was found in 10 patients (3.2%).

LGE Score, LVEF, Wall Thickness and LV Pressure Gradient

Figure 4A shows the relationship between maximum wall thickness and LGE score. The patients were stratified by wall thickness into 3 groups: mild (<20 mm), moderate (20–29 mm), and severe (≥30 mm), and LGE score in the 3 groups was compared. Median LGE score was 2 (IQR, 4) in the mild group, 4 (IQR, 4) in the moderate group, and 5 (IQR, 5) in the severe group, with a significant difference between the 3 groups (P=0.000). The extent of LGE in the LV increased as wall thickening became more severe.

Figure 4.

Relationship of (A) maximum wall thickness, (B) left ventricular ejection fraction (LVEF) and (C) pressure gradient to extent of late gadolinium enhancement (LGE) in 317 patients (expressed as LGE score in an LV 17-segment model). Box, interquartile range; horizontal line, median.

Figure 4B shows the relationship between LVEF and LGE score. The patients were stratified by LVEF into 3 groups: reduced (<50%), low-normal (50–65%), and normal (>65%), and LGE score in the 3 groups was compared. Median LGE score was 7 (IQR, 8) in the reduced group, 4 (IQR, 5) in the low-normal group, and 2 (IQR, 4) in the normal group, with a significant difference between the 3 groups (P=0.000). The extent of LGE in the LV increased as LVEF decreased.

Figure 4C shows the relationship between pressure gradient and LGE score. The patients were stratified according to pressure gradient < or ≥30 mmHg, and LGE score in the 2 groups was compared. Median LGE score was 4 (IQR, 6) for pressure gradient <30 mmHg, and 2 (IQR, 4) for pressure gradient ≥30 mmHg, with a significant difference between the 2 groups (P=0.000). LGE score in the LV was significantly greater for pressure gradient <30 mmHg compared with pressure gradient ≥30 mmHg.

Stratification by LGE Score

The 317 patients were divided according to median LGE score (3) into 2 groups: LGE absent or mild (LGE score ≤3) and LGE extensive (LGE score ≥4). Compared with the LGE absent or mild group, the LGE extensive group was younger (64 vs. 68 years, P=0.007), contained more men (83/138, 60.1% vs. 64/179, 35.8%, P=0.000), and had a higher rate of NSVT (29/138, 21.0% vs. 15/179, 8.4%, P=0.001; Table 2). For echocardiographic parameters, LV end-diastolic volume (LVEDV) was significant greater (88.0 vs. 79.3 ml, P=0.041), LV end-systolic volume (LVESV) was significantly greater (32.5 vs. 27.8 ml, P=0.000), LVEF was significantly smaller (63.4 vs. 65.6%, P=0.000), and prevalence of LV pressure gradient ≥30 mmHg was significantly lower (67/138, 48.6% vs. 120/179, 67.0%, P=0.001) in the LGE extensive group compared with the LGE absent or mild group. On CMR, in the LGE extensive group maximum wall thickness was significantly greater (23.0 vs. 19.0 mm, P=0.000) and prevalence of maximum wall thickness ≥30 mm was significantly higher (22/138, 15.9% vs. 7/179, 3.9%, P=0.000) compared with the LGE absent or mild group.

Table 2. HCM Subject Clinical Characteristics vs. LGE Extent (n=317)

	LGE absent or mild (score ≤3) (n=179)	LGE extensive (score ≥4) (n=138)	P-value
Age (years)	68	64	0.007
Male	64 (35.8)	83 (60.1)	0.000
Family history of HCM	14 (7.8)	11 (8.0)	0.961
Family history of SCD	17 (9.5)	20 (14.5)	0.170
History of syncope	33 (18.4)	23 (16.7)	0.682
DM	18 (10.1)	19 (13.8)	0.307
VT	15 (8.4)	29 (21.0)	0.001
AF	24 (13.4)	21 (15.2)	0.647
NYHA functional class III or IV	36 (20.1)	27 (19.6)	0.904
Medications
β-blocker	132 (73.7)	103 (74.6)	0.857
Aldosterone inhibitors	10 (5.6)	16 (11.6)	0.053
Diuretics	18 (10.1)	20 (14.5)	0.228
Anti-arrhythmics (class III)	7 (3.9)	7 (5.1)	0.618
Anti-arrhythmics (class I)	85 (47.5)	55 (39.9)	0.175
Calcium antagonist	58 (32.4)	46 (33.3)	0.861
ACEi/ARB	39 (21.8)	36 (21.6)	0.372
Echocardiographic characteristics
LVEDV (ml)	79.3	88.0	0.041
LVESV (ml)	27.8	32.5	0.000
LVEF (%)	65.6	63.4	0.000
LAD (cm)	4.1	4.2	0.190
Pressure gradient ≥30 mmHg	120 (67.0)	67 (48.6)	0.001
CMR characteristics
Maximum LV wall thickness (mm)	19.0	23.0	0.000
Maximum LV wall thickness ≥30 mm	7 (3.9)	22 (15.9)	0.000
LGE	108 (60.3)	138 (100)	0.000
LGE score	1	6	0.000

Data given as median or n (%). VT, ventricular tachycardia. Other abbreviations as in Table 1.

Predictors for Extent of LGE

On comparison of clinical parameters between the LGE absent or mild group and the LGE extensive group, the following variables had P<0.1: age, gender, NSVT, aldosterone inhibitor use, LVEDV, LVESV, LVEF, pressure gradient ≥30 mm, and maximum wall thickness (maximum wall thickness ≥30 mm was not used); given that LVEDV and LVESV are strongly correlated, only LVESV was used. Using the aforementioned variables, univariate and multivariate logistic regression analysis with stepwise variable selection was conducted (Table 3). On multivariate analysis 3 variables were independently associated with extensive LGE: reduced LVEF (OR, 0.947; 95% CI: 0.907–0.990, P=0.015); pressure gradient <30 mmHg (OR, 0.359; 95% CI: 0.203–0.633, P=0.000); and increased maximum wall thickness (OR, 1.236; 95% CI: 1.161–1.316, P=0.000).

Table 3. Significant Factors of Extensive LGE

Variable	Univariate analysis		Multivariate analysis with stepwise variable selection
	OR (95% CI)	P-value	OR (95% CI)	P-value
Age (years)	0.979 (0.965–0.992)	0.002
Male gender	2.710 (1.715–4.292)	0.000
Presence of NSVT	2.909 (1.490–5.678)	0.002
Aldosterone inhibitor	2.216 (0.973–5.051)	0.058
LVEDV (ml)	1.005 (0.997–1.013)	0.214
LVESV (ml)	1.016 (0.999–1.033)	0.063
LVEF (%)	0.927 (0.889–0.967)	0.000	0.947 (0.907–0.990)	0.015
Pressure gradient ≥30 mmHg	0.464 (0.294–0.733)	0.001	0.359 (0.203–0.633)	0.000
Maximum LV wall thickness (mm)	1.193 (1.129–1.261)	0.000	1.236 (1.161–1.316)	0.000

Abbreviations as in Table 1.

Discussion

In the present study, clinical background and LGE findings on CMR were analyzed in a large number of Japanese patients with HCM. Intraventricular pressure gradient ≥30 mmHg, indicating obstructive type, was present in 59.0%; LVEF <50%, indicating end-stage type, was present in 3.2%; and LGE was noted in 77.6% of patients with HCM. Additionally, LGE was detected in an average 3.5 segments in an LV 17-segment model, and was most frequently found in the septal regions, corresponding to the site most prominently involved in wall thickening. Furthermore, the progression of LGE was related to increased wall thickness, decreased contractility, and reduced intraventricular pressure gradient.

The assessment of LGE on CMR in HCM patients was reported in 2002,²¹ and recent studies have suggested that LGE reflects the pathology of mainly interstitial and replacement fibrosis in the myocardium.²² The frequency of LGE detection differs in large-scale studies conducted in America and Europe due to the differences in evaluation method and subject population, and frequencies ranging from 50 to 80% have been reported.² In the present study, LGE was observed in 77.6% of the HCM patients.

In HCM, LGE has been detected commonly at the right ventricle insertion to the ventricular septum.²³ In the present study, LGE was also most prominently found in the ventricular septum, and was relatively rarely in the lateral wall. The distribution of LGE is related to the wall thickness, which has been reported previously.²⁴ When we stratified the present subjects by wall thickness into 3 groups, LGE score increased as wall thickness increased; thus LGE tends to occur in sites of severe hypertrophy, consistent with previous reports.

HCM accompanied by LVEF <50%, which indicates reduced systolic function, is termed end-stage HCM.¹² In a nationwide survey conducted by Matsumori et al in Japan, HCM patients with LVEF <50% comprised 6.2% of all subjects.¹⁷ In the present single cardiovascular center study, 3.2% of the subjects had LVEF <50%. Harris et al also reported a prevalence of 3.5%.¹² Thus, end-stage HCM probably comprises several percent of all HCM patients.

Extensive LGE has been identified in HCM patients with remarkably impaired systolic function.^12–14 Olivotto et al examined a group of patients with LVEF 50–60% (low-normal group) who did not reach end-stage HCM.¹³ They found a high prevalence of LGE in this low-normal group, and suggested that this group represents the stage before end-stage HCM and should be followed carefully. In the present study, we also stratified LVEF into 3 groups, and found that LGE score increased as LVEF decreased, indicating a relationship between the extent of LGE and impaired systolic function in HCM.

Furthermore, LGE has attracted attention recently as a possible prognostic factor of cardiovascular events.^4–11 Reviewing previous reports of large-scale studies over time, from 2008 to 2010, LGE was reported to be an independent prognostic factor for cardiovascular event in some reports, and not a prognostic factor in others.^4–7 In 2012, a meta-analysis of past studies reported that LGE significant predicts all deaths, cardiac death, and heart failure death, while there is a trend toward significance for predicting sudden death or aborted sudden cardiac death (P=0.091).⁸ Then in 2014, Ismail et al reported that LGE was not an independent prognostic factor when the data were adjusted for LVEF.⁹ In the same year, however, a large-scale prospective study of 1,293 patients conducted by Chan et al found that LGE was an independent prognostic factor even after adjustment for LVEF.¹⁰ In their study, each 10% increase in LGE was associated with a 40% increase in relative risk of sudden cardiac death. According to their results, although LGE is found in a large proportion of HCM patients, the extent of LGE ranges from trivial to extensive. Therefore, the presence of LGE should not be treated as a single risk marker, but the extent of LGE should be used for risk stratification. Furthermore, in a study using myocardial biopsy, the severity of fibrosis was related to lethal arrhythmic events, indicating the importance of the extent of fibrosis.²⁵

In our previous study of a large number of Japanese HCM patients, LGE was scored as the sum of sites with LGE based on an LV 17-segment model, and LGE score ≥4 was classified as marked LGE. The arrhythmia event rate was higher in the group with marked LGE compared with the mild or no LGE group.¹¹

Given that the median LGE score in the present study was 3, the patients was classified into LGE absent or mild (LGE score ≤3) and LGE extensive (LGE score ≥4), and the clinical parameters compared between the 2 groups. On multivariate analysis increased wall thickness, lowered LVEF, and decreased intraventricular pressure gradient were independent factors associated with extensive LGE.

The main phenotype of HCM is characterized by hypertrophy of the myocardium. Hypertrophy causes fibrosis mainly via the mechanism of microvascular ischemia,^26–28 and this pathological change is probably recognized as LGE on CMR. LGE is present markedly in the hypertrophic region, and expansion of the LGE area in the myocardium probably causes not only impaired diastolic function but also impaired systolic function,^29,30 resulting in a decrease in intraventricular pressure gradient. Regarding intraventricular pressure gradient, patients with low LVEF have been reported to have a low prevalence of obstructive HCM.^31–33 Therefore, reduced pressure gradient is probably the result and not the cause of extensive LGE.

Taken together, LGE presumably indicates the pathological state of the myocardium in HCM patients and may be an indicator of remodeling. Thus, LGE is an important imaging finding for predicting events related to sudden cardiac death and heart failure. Recently, the chronological changes in LGE detected on CMR have been reported,^34,35 but the number of reports remains small and is an important topic for further studies.

Several issues on the quantitative measurement of LGE remain unsolved. As a result, evaluation of myocardium fibrosis is being switched to new methods such as T1 mapping and extracellular volume quantification.^15,16,36 Research on LGE over the past 2 decades, however, has provided valuable clinical data. Furthermore, LGE can be assessed relatively easily on visual inspection of CMR. Evaluation of LGE will continue to provide useful imaging information in the routine clinical setting.

Study Limitations

This study had several limitations. First, the study was a retrospective observational study in a single institution. Second, Sakakibara Heart Institute is a cardiovascular specialty hospital and many patients are referred from other hospitals. The subjects were not consecutive patients who fulfilled the criterion of having undergone coronary artery evaluation, and therefore may not represent the general population of HCM patients. Last, LGE areas were judged on consensus, and were not measured quantitatively, but were scored semi-quantitatively by visual assessment based on an LV 17-segment model. A large-scale multi-center prospective study using the most appropriate method for quantifying LGE is required.

Conclusions

In the present single-center study of 317 Japanese HCM patients, LGE occurred most frequently in the basal septal region, corresponding to the site most prominently involved in wall thickening. Moreover, increased wall thickness, impaired systolic function, and reduced ventricular pressure gradient were independent factors associated with extensive LGE.

Acknowledgments

This study was supported by the Sakakibara Clinical Research Grant for Promotion of Science, 2015. We thank Mr Naokazu Mizuno, Mr Shou Sugioka, and Mr Jun Matsuda of the staff at Sakakibara Heart Institute for technical assistance.

References

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