Echocardiography

Echocardiographic examinations were performed in each subject using a Philips iE33 (Philips Medical Systems, Andover, MA) equipped with an S3 probe (2–4 MHz) for two-dimensional and Doppler measurements and an X3-1 matrix-array transducer (1.9–3.8 MHz) for three-dimensional examinations. All acquisitions were performed in the echocardiography laboratory of the Department of Cardiovascular and Respiratory Sciences at “Sapienza” University by expert cardiologists, with specific training in three-dimensional echocardiography.

Two-dimensional assessment of LV cavity diameters, wall thickness, left atrium, and aortic root diameter were performed according to the current European Association of Echocardiography and American Society of Echocardiography criteria.

Transthoracic harmonic real-time three-dimensional echocardiography was performed from the apical four-chamber view using the full-volume technique. Wide-angle acquisition was performed, and a high frame rate (30 ± 4 Hz) was obtained using the seven-beat acquisition protocol, in which seven consecutive wedge-shaped subvolumes are consecutively sampled with a trigger to the R wave of the electrocardiogram.

At least three acquisitions were obtained for each subject and analyzed offline using commercially available software (QLAB version 7.0; Philips Medical Systems).

LV end-diastolic and end-systolic volumes, stroke volume, and ejection fraction were obtained using a semiautomatic border detection technique, as previously described. LV mass was calculated using a biplane measurement obtained from a three-dimensional data set, as previously reported and validated.

The three-dimensional echocardiographic sphericity index (3DSI) was calculated, according to Mannaerts et al. , as LV end-diastolic volume divided by the volume of a sphere, the diameter of which is the LV major end-diastolic long axis.

For the purpose of this study we specifically defined the trabeculated LV volume (TLV) as the difference between the LV end-diastolic volume measured by delineating the endocardial border at the bottom of the recesses and the end-diastolic volume delineated at the peak of the trabeculae.

In detail, the end-diastolic frame was identified, the gain level was optimized, and smoothing was reduced to visualize the endocardial border; by adjusting the cutting planes, the true apical four-chamber and two-chamber views were obtained, avoiding foreshortening, and then five reference points on the septal, lateral, anterior, and inferior aspects of the mitral annulus and at the apex were located. The software automatically delineated the endocardial contour of the left ventricle in the entire acquired data set. Subsequently, by rotating the long-axis cutting planes over 180°, the automatic tracing was reviewed by the operator, and the endocardial contour was modified to include or exclude the trabeculae and recesses ( Figure 1 ). The papillary muscles were excluded from tracing and included in the cavity. End-diastolic volume was first calculated by tracing the endocardial border at the interface between the noncompacted and compacted myocardium (the bottom of the recesses) and then by tracing the endocardial border at the peak of trabeculations; the TLV was obtained from the difference of the two values ( Figure 2 ).

The endocardial contour was traced over virtually infinite rotational cutting planes (with respect to the LV major axis) at end-diastole. Tracing was performed first at the bottom of recesses ( red line ) and thereafter at the peak of the trabeculae ( blue line ).

After tracing the endocardial border at the bottom of the trabeculae and at the peak of the recesses, we obtained the end-diastolic volume including trabeculae ( red ) and excluding trabeculae ( blue ). The difference between the two volumes corresponded to the TLV. TLV was also normalized by LV end-diastolic volume including trabeculae as the expression of the proportion of LV cavity occupied by trabeculae (TLV%).

The TLV as here defined included both trabeculae and blood inside the recesses and was expressed in milliliters. The TLV was also normalized by LV end-diastolic volume (TLV%) as the expression of the proportion of LV cavity occupied by trabeculae.

Offline analysis was performed by an investigator blinded to patients’ clinical data.

Statistical Analysis

Continuous data are expressed as mean ± SD and categorical data as frequencies. Two-tailed P values < .05 were considered statistically significant. Differences between mean values for continuous variables were assessed using unpaired Student’s t tests or Mann-Whitney tests for variables with nonnormal distributions.

Differences in terms of age and body surface area were assessed using analysis of variance with multiple post hoc Bonferroni’s tests. Differences in terms of male proportion among groups were assessed using χ ² tests.

Multiple Pearson’s simple correlations were calculated to test the association between TLV and TLV% and other parameters.

Receiver operating characteristic curve analysis was performed to identify optimal cutoff values for three-dimensional echocardiographic TLV and TLV% to identify patients with LVNC among our study population.

To assess the reproducibility of TLV and TLV%, measurements were repeated in a random sample of 10 patients with LVNC and 10 healthy controls by the same investigator (intraobserver variability) and by an additional reader (interobserver variability). Both were blinded to each other’s and patients’ data. Interobserver and intraobserver variability was assessed using intraclass correlation coefficients (ICCs) with 95% confidence intervals (CIs) and coefficients of variation (CVs; i.e., the absolute difference in percentage of the mean of repeated measurements).

Statistical analysis was carried out using SPSS version 15.0 (SPSS, Inc., Chicago, IL).

Demographic and Clinical Features

No difference in terms of age was detected between patients with LVNC (37 ± 21 years) and control subjects (26 ± 3 years, P = .077) or athletes (27 ± 2 years, P = .408). Athletes had higher body surface areas (2.06 ± 0.20 m ² ) than both controls (1.81 ± 0.18 m ² , P < .001) and patients with LVNC (1.83 ± 0.26 m ² , P < .001), while no differences were identified between the last two. The proportion of men was higher among athletes ( n = 24 [92%], P = .007), while no differences were found between controls ( n = 12 [71%]) and patients with LVNC ( n = 28 [57%]).

Clinical characteristics of patients with LVNC are reported in Table 1 . Electrocardiographic abnormalities were common among patients with LVNC ( n = 13 76%) and included left-axis deviation ( n = 4), nonspecific repolarization abnormalities ( n = 4), complete left bundle branch block ( n = 2), frequent premature ventricular contractions ( n = 2), and Wolff-Parkinson-White pattern ( n = 1). Seven patients had positive family histories, consisting of similar appearance of LVNC in a first-degree relative ( n = 3), hypertrophic or dilated cardiomyopathy ( n = 2), and sudden cardiac death ( n = 2). Six patients had symptoms of congestive heart failure ( n = 2) or decreased ejection fraction ( n = 4); one young patient required heart transplantation. Nine patients underwent cardiac magnetic resonance, which confirmed the diagnosis of LVNC on the basis of a noncompacted/compacted ratio > 2.3. Three patients had cryptogenic stroke (documented by positive findings on cranial computed tomography) or transient ischemic attack. Finally, one patient had a neuromuscular disorder (esophageal achalasia).

Table 1

Clinical and echocardiographic parameters of 17 patients with LVNC

Patient	Gender	Chin index	Jenni index	Stöllberger criteria	Ejection fraction (%)	CMR	Positive family history	ECG abnormality	NMD	CHF	Stroke/TIA
1	Male	0.33	2.10	+	52	+		+		+	+
2	Male	0.25	2.10	+	56	+		+
3	Male	0.25	2.3	+	45	NA	+	+		+
4	Male	0.34	2.6	+	56	+	+
5	Male	0.28	2.28	+	15	+	+	+		+
6	Female	0.22	2.0	+	64	+		+	+
7	Female	0.35	1.8	+	62	+
8	Male	0.35	1.9	+	45	+		+		+
9	Male	0.24	2.3	+	61	NA		+
10	Male	0.26	2.0	+	65	+		+
11	Male	0.46	1.9	+	69	+	+
12	Female	0.32	2.0	+	26	NA		+		+
13	Female	0.32	1.75	+	45	NA		+		+	+
14	Male	0.15	3.75	+	42	NA	+	+		+
15	Male	0.37	2.0	+	58	NA	+	+
16	Male	0.23	2.0	+	69	NA	+	+
17	Female	0.21	1.33	+	66	NA					+

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