Left Ventricular Hypertrabeculation (LVHT)/Left Ventricular Non-Compaction (LVNC): An Unclassified Form of Cardiomyopathy. Lorna Estabrooks, RN, MN,CCN(C), CNCC(C), Paula Price, RN, PhD. Susan Beischel, RN, MN. Department of Advanced Specialty Health, Mount Royal College, Calgary, Alberta, Canada. Background  In early embryonic development, the myocardium is a loose network of interwoven fibres separated by deep recesses that link the myocardium with the LV cavity. Gradual “compaction” of this spongy meshwork of fibres and intertrabecular recesses, or “sinusoids,” occurs between weeks 5 & 8 of embryonic life. (Ritter, Oechslin, & Sutsch, 1997).  The LV has up to 3 prominent trabeculations & is less trabeculated than the RV. LVHT Anatomic and Pathophysiologic Findings  Thought to be caused by arrest of the normal process of endomyocardial morphogenesis.  Is frequently described as an abnormal finding of the LV apex & its adjacent lateral and inferior walls.  Usually occurs distal to the papillary muscles (Finsterer, 2005).  In hearts with LVHT there is: (1) extensive spongy transformation of the LV myocardium and frequently associated with other cardiac morphologic abnormalities; (2) prominent coarse trabeculations of the ventricular wall and deep recesses of the ventricular cavity; (3) a dysplastic appearance of the myocardium with thinned myocardium and excessive trabeculations.  During normal embryonic development, endomyocardial trabeculations emerge from the apical region of the primitive ventricles at day 32 of fetal life, and involute by day 70 through resorption and remodeling. LVHT is thought to represent a failure of this “compaction” process.  There are several hypotheses proposed to explain the occurrence of LVHT: (1) it represents persistence of embryonal sinusoids and results from an arrest in the compaction process of the myocardium (Bellet & Gouley, 1932), (2) it might result from an attempt of an impaired myocardium to grow and, thus, trying to overcome an inborn error so the trabeculations in the ventricles enable the myocardium to increase its mass (Sedmera, Pexieder, Vuillemin, Thompson, & Anderson, 2000), (3) it might be the result of an adaptation to special hemodynamic conditions ( Agnisola & Tota, 1994), (4) it might be the consequence of an impaired adhesion of cardiac myocytes as a result of malfunction of gap junctions (Spach, 1994), (5) it might be a result of a cardiac neuropathy, a disturbance associated with the cardiac conduction system comprising His- and Purkinje fibres (Ansari & Ho, 1999). Synonyms  Honeycombed myocardium,  Spongy myocardium,  Persisting myocardial sinusoids,  LV noncompaction (LVNC),  Isolated LV abnormal trabeculation,  LV hypertrabeculation (LVHT). Prevalence  Rare - varies from 0.05 to 0.24%/year (Ritter, Oechslin, Sutsch, Attenhofer, Schneider, & Jenni, 1997; Stollberger, Finsterer, & Blazek, 2000; Stollberger, Finsterer, & Blazek, 2002).  Occurrence likely varies between different populations because it is often associated with genetically based disorders.  Of the 223 published cases there is a higher prevalence among men (66% vs. 32%) and age at diagnosis varies considerably (Stollberger & Finsterer, 2004). Clinical Characteristics Associated with other cardiac, neuromuscular, and genetic disorders.  May be present at birth but not always and may or may not have a familial occurrence (Strollberger & Finsterer, 2004). In some familial cases, the genes have been identified, but not in all cases (Weiford, Subbarao, & Mulhern, 2004).  Can be highly symptomatic with a high incidence of ventricular arrhythmias and progressive heart failure ( Murphy et al., 2004) or patients maybe asymptomatic (Weiford et al., 2004).  Patients with LVHT have poorly functioning dilated ventricles; therefore, some believe this to be a form of DCM (Murphy et al., 2005). Others have described it as a restrictive cardiomyopathy (Ichida et al., 1999).  The pathophysiolgic mechanisms of heart failure, systolic dysfunction, and arrhythmia are not known.  Diastolic dysfunction may be related to both abnormal relaxation and restrictive filling caused by the numerous prominent trabeculae (Weiford et al., 2004).  Associated with neuromuscular disorders in 80% of cases or with other genetic disorders (Finsterer, 2005).  Metabolic myopathies are the most frequent neurologic abnormality noted ( Strollberger et al., 2002).  Believed to be frequently associated with embolic events.  Some other clinical presentations include low set ears and coarctation (Finsterer, 2005) and facial dysmorphism (Chin et al., 1990). Nursing Implications I.Monitor for signs and symptoms of heart failure, tachyarrhythmias, and emboli. II.Patient and family counseling and education related to LVNC/LVHT being genetic and heterogeneous. III.Patients maybe asymptomatic. IV.Awareness that prevalence is higher than previously thought & prevalence has increased with the improvement of cardiac imaging (echocardiography & cardiac MRI and CT). (Towbin & Bowles, 2002)