*3.1. Study Population with Genetic and Clinical Evaluation*

A total of 38 isolated LVNC patients diagnosed by CMRI, APE, or both (Figure 1), were evaluated. Results of genetic evaluation are presented in Table 1.



#### *J. Clin. Med.* **2020**, *9*, 2524

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**Figure 1.** Transplanted patient with isolated left ventricle non-compaction cardiomyopathy diagnosed by CMRI and confirmed by anatomopathological examination. Panel (**A**) Transversal slides of the explanted heart. (**B**) Spheroidal shape of the transplanted heart. (**C**) Apical 4 chamber view in TTE. (**D**) Parasternal short axis in TTE. (**E**) LVNC in CMRI.

A P/LP variant was found in 13 patients (patients 1–13, group 1), meaning a genetic yield of 34.2%. Genetic testing was negative (no relevant genetic variants were identified) in patients 18 to 38 (group 2). Another five patients were carriers of VUS and, therefore, considered separately (patients 14–17, group 3). Family screening was performed in all available relatives, supporting variants segregation criteria in P/LP variants (Figure 2).

Principal clinical characteristics of patients with isolated LVNC are summarized in Table 2. Mean age was 49.4 ± 13.9 SD and 65% of patients were men. Median follow-up of patients was 9.5 years ± 5 SD. Most patients were referred to cardiology due to symptoms, especially due to dyspnoea or other heart failure secondary symptoms. If left ventricular dysfunction was present, optimal medical treatment was given in all patients. LVNC was correctly suspected in fist echocardiogram only in 55% of patients. A cerebrovascular accident (CVA) occurred in 18.4% of patients. In fact, neurological study was the reason for referral in four patients (10.8%). Atrial fibrillation (AF) was identified in only four of the seven patients with ACV. Two patients had suffered CVA with a normal LVEF and without documented AF. What is more, one of them had a recurrent CVA despite and international normalized ratio (INR) of 2.7. Possible trigger factors were identified in 18.4% of patients, most of them due to high intensity sport activity and one of them due to a high flow arteriovenous fistula. Family history of cardiomyopathy was present in 31.5% and 13.15% of patients required heart transplantation.


**Table 2.** Clinical characteristics of LVNC patients. CVA, cerebrovascular accident, EKG, electrocardiography; TTE, transthoracic echocardiogram; Tx, transplanted; FH, family history; LVEF, left ventricular ejection fraction (0, normal; 1, mild depressed, 2; moderate; 3, severely depressed).

With genetic screening, up to 22 relatives with P/LP variant carriers and 27 non-carriers relatives were identified. Intrafamilial phenotypic variability was frequently found. As expected, in LMNA families, DCM phenotype was present and HCM in those with sarcomeric pathogenic variants (Figure 2). Moreover, a fluctuant LVEF was found in a relative with previous history of a TTN LP variant carrier (Fam. 8, Figure 2). Clinical and genetic screening for suspicious VUS variants was also performed. However, information obtained was not considered strong enough yet to classify these variants as LP or likely benign variants.

**Figure 2.** Pedigree of families with LVNC. Fam., family; SD, sudden death; PM, pacemaker; LVNC, left ventricular non-compaction; DCM, dilated cardiomyopathy: HCM, hypertrophic cardiomyopathy. Symbols denote sex and disease status: +, carriers; −, non-carriers; without sign, not studied; box, male; circle, female; darkened, phenotype of hypertrophic cardiomyopathy; symbol clear, unaffected; ?, unknown phenotype; slashed, deceased; without sign, not genetically studied; arrow, proband. Age of deceased or PM implantation in brackets.

Main clinical differences between patients with P/LP variants (group 1) and those with negative genetic result, carriers of benign or likely benign variants (group 2) are shown in Table 3. Most patients from group 1 had a known family history of cardiomyopathy. Conversely to group 1, in group 2, a possible trigger factor for LVNC was found in 1/3 of them. Besides, the evolution of LVEF in time showed different patterns between these groups (Figure 3). Initial LVEF in group 2 was better and those impaired a tendency to improve under optimal medical therapy. At baseline, only 57% of them had normal LVEF and 28.6% had a moderate or severe dysfunction. During follow-up, 76.2% of them reached a normal LVEF, being only slightly reduced in 19%. No patients underwent cardiac transplantation or presented severe cardiac dysfunction in follow-up. However, during follow-up, most patients from group 1 (69.2%) presented moderate-severe LV dysfunction and 30.8% underwent heart transplantation.


**Table 3.** Clinical characteristics of carriers of P/LP variants (group 1) and patients with negative genetic result, carriers of benign or likely benign variants (group 2).

**Figure 3.** Left ventricle systolic function evolution in follow-up. Group 1, LVNC with pathogenic or likely pathogenic variants; Group 2, LVNC with benign or likely benign variants. Red colour, severely depressed LVEF; yellow, moderately depressed LVEF, bright blue, slightly depressed LVEF; dark blue, normal LVEF.

An internal cardiac defibrilator (ICD) was implanted in 12 patients. Almost half of patients from group 1 had an ICD (46.1%), 50% with at least one appropriate therapy during follow-up. Conversely, only three patients from group 2 (14.3%) received an ICD. What is more, in all three LVEF improved during follow-up and even normalized in two of them.

Apart from that, despite these differences in LVEF, patients suffered cerebrovascular accidents in similar proportions in both groups (23% group 1 vs. 19% group 2, *p* = 0.4). Atrial fibrillation or flutter had been detected in six patients form group 1 and 4 from group 2. However, in both groups, a patient suffered a cerebrovascular accident without previous known arrhythmias.
