The phenotypic expression of NCC is variable, but two thirds of patients have left ventricular systolic and / or diastolic dysfunction^{[1][2][3][4][5][6]}. Patients may also present with left ventricular restriction. Even if hemodynamic abnormalities were not present at the time of diagnosis, one study from Japan demonstrated that the majority of children developed hemodynamic abnormalities after 17 years of follow-up^[7].

Diastolic dysfunction is thought to be due to abnormal relaxation as a result of extensive trabeculation^[8].

Systolic dysfunction in NCC is thought to be due to subendocardial ischemia and microvascular dysfunciton in the absence of epicardial coronary artery disease. Ischemia in the territory of noncompaction has been documented on thallium 201 scintigraphy^[9], on positron emission tomography (PET) ^[10], and on MRI imaging ^[11]. Lesions consistent with subendocardial ischemia have been observed on autopsy. Impaired coronary flow reserve and microcirculatory defects have been observed on a variety of imaging modalities^[12]. The basis for the ischemia has been hypothesized to be extrinsic compression of the microvasculature by the hypertrophied muscle and isometric contraction of the myocardium against the trabeculae.

A restrictive pattern of filling can be observed on cardiac catheterization^[13][14].

These patients are at risk of forming mural thrombus in the left ventricle and embolization. As a result, all patients with NCC are treated with prophylactic aspirin.