Diagnosis and Follow-Up

No interobserver studies were carried out for measurement of the noncompaction/compaction ratio, but in patients with diagnostic challenges, studies were reviewed by both authors to see if they met the criteria for inclusion. All included patients had multiple studies with multiple different readers making the diagnosis of left ventricular noncompaction. Those patients were then carefully examined to confirm if left ventricular noncompaction was present using the 4 criteria listed in our article and described in the literature.

Autopsy specimens were available for 3 of the patients in our series, and left ventricular noncompaction was verified in all. Figure 1 is an example of left ventricular noncompaction in patient 6 in group 2 (patients who died or needed heart transplantation).

Apical short-axis dissection of a pathologic specimen in a patient who died in our series from left ventricular noncompaction and Ebstein’s anomaly. The noncompaction (NC) is noted at the apex of the left ventricle (LV). The tricuspid valve (TV) apparatus is significantly displaced into the apical region, while the right ventricle (RV) demonstrates significant dilation and hypertrophy. The length of the black line represents 1 cm. This image was obtained courtesy of Andrew J. Connolly, MD, PhD, Stanford University, Lucille Packard Children’s Hospital. ∗Middle cardiac vein.

As stated in our paper, follow-up was not adequate to consistently state whether or not left ventricular noncompaction changed over time or with therapy, as discussed in the “Limitations and Future Directions” section. The majority of patients’ indications for echocardiography were to rule out structural heart disease or to evaluate a known cardiomyopathy. Many patients are referred to our institution for cardiomyopathy. Left ventricular noncompaction was an associated diagnosis that may not have been detected at the other institutions. As noted in the paper, one patient was discovered incidentally, prior to initiating chemotherapy.

Segmental Analysis

In all patients, the 16 segments were easily visualized and analyses were performed. Given that 16 segments were analyzed for 42 patients, a total of 672 segments were evaluated. In 150 of these segments, no left ventricular noncompaction was appreciated. One hundred ten segments lacked left ventricular noncompaction at the base. Only 30 segments lacked noncompaction at the midcavitary region, and only 10 lacked noncompaction at the apex.

High variability between adjacent regions was not as pronounced in our study. The most affected areas were the midpapillary and apical regions of the myocardium. The base was relatively spared, while the interventricular septum was not as affected as the free wall. This was explained in our “Discussion” section. Compaction begins at the base and extends to the apex; failure to compact would therefore affect the apex more than the base of the heart. Additionally, compaction occurs from the interventricular septum to the left ventricular free wall. Therefore, the free wall will be more affected than the interventricular septum.