Left ventricular noncompaction of the ventricular myocardium: ever a challenging diagnosis.

Noncompaction of the ventricular myocardium is currently listed as an unclassified cardiomyopathy. (1) This relatively new entity, first described in 1990, (2) poses a problem of differential diagnosis in patients presenting with heart failure.

Left ventricular noncompaction (LVNC) is characterized by multiple, prominent trabeculations of the left ventricular endocardium and deep intertrabecular recesses, which communicate freely with the left ventricular cavity. Right ventricular myocardium can also be trabeculated, but persistence of prominent trabeculations in the left ventricle is normally not seen after birth. Thus, LVNC appears to represent an arrest in the intrauterine endomyocardial morphogenetic process of myocardial compaction. This process begins in the 2nd month of embryonic life, when the heart is a "spongy," loosely interwoven mesh of muscle fibers which gradually compacts from the epicardium to the endocardium and from the base to the apex.

Noncompacted myocardium has also been described in association with congenital cardiac malformations that cause intraventricular pressure overload or ischemia (obstructive lesions of the RV or LV outflow tract and congenital coronary anomalies). The deep recesses in such cases are in continuity with the coronary arteries and are described as persisting intramyocardial sinusoids. On the contrary, isolated LVNC exists in absence of other cardiac anomalies.

The prevalence of LVNC ranges from 0.05 to 0.24% per year in various echocardiographic studies. (3) It is expected, however, that incidence of the disease is higher and will be revealed with increasing awareness by cardiologists.

The clinical course of LVNC is highly variable, ranging from the complete asymptomatic status to severe heart failure requiring heart transplantation. Most reports have so far suggested that LVNC is associated with left ventricular dilation and systolic dysfunction, often accompanied by ventricular arrhythmias and systemic emboli. (4) Nonetheless, patient selection through population or family screening has identified patients with milder phenotype and lower incidence of death, stroke or sustained ventricular arrhythmias. (5,6) The age at onset of symptoms is also variable, with heart failure, ventricular tachyarrhythmias and death presenting predominantly in adults. (4) Systolic ventricular dysfunction seems to develop from long-standing subendocardial ischemia due to microcirculatory dysfunction, even though epimyocardial blood flow is normal. (2) Indeed, coronary flow reserve is decreased in most hypokinetic segments while it is preserved in most normal segments, not depending on the presence of trabeculation. (7) Although not proven yet, it seems that isolated LVNC present at birth is a progressive disorder leading to heart failure due to the superimposed chronic myocardial ischemia. (8)

Three different approaches to the echocardiographic criteria for diagnosis of LVNC have been proposed. They focus on trabeculae at the left ventricular apex on the parasternal short axis and apical views and on the corresponding left ventricular wall thickness. First, Chin et al (2) define LVNC by a ratio of X/Y[less than or equal to]0.5, where X is the distance from the epicardial surface to the trough of the trabecular recess and Y is the distance from the epicardial surface to peak of trabeculation during diastole. Secondly, Jenni et al (9) propose a method based on recognition of a two-layer structure with a compacted thin epicardial band and a much thicker noncompacted endocardial layer of trabecular meshwork with deep endomyocardial spaces, supplied by intraventricular blood on color Doppler, where a maximal end-systolic thickness ratio of noncompacted to compacted layers of >2 is diagnostic. In the last approach, Stollberger et al (10) define LVNC by echocardiographic depiction in one image plane of >3 trabeculations that protrude from the apical parts of the left ventricular wall, have the same echogenicity like the myocardium and move synchronously with ventricular contractions, while intertrabecular spaces are perfused from the ventricular cavity on color Doppler.

Since trabeculation is mostly located at the apex, which is often difficult to visualize adequately with echocardiography, the above criteria appear complementary for the diagnosis of LVNC. (6) In addition, contrast echocardiography can be useful, as it provides clearer endocardial border delineation for the application of the above criteria, especially in cases with more subtle morphology of noncompaction. (11) In such cases, MRI might also be helpful. (12)

Diagnostic efficiency of LVNC has evolved with technological advances in echocardiography. It is frequently admitted that earlier generation equipment did not offer sufficient image resolution in contrast to newer harmonic imaging that overcomes earlier diagnostic ambiguities. Even so, there is always need to distinguish LVNC from prominent normal ventricular trabeculations, false tendons and aberrant bands, as well as from hypertrophic cardiomyopathy, dilated cardiomyopathy, endocardial fibroelastosis, myocarditis, apical thrombus or tumor, all of which have been described as wrong initial diagnoses in patients with LVNC.

References

1. Richardson P, McKenna W, Bristow M, et al. Report of the 1995 World Health Organization/International Society and Federation of Cardiology Task Force on the Definition and Classification of cardiomyopathies. Circulation 1996;93:841-842.

2. Chin TK, Perloff JK, Williams RG, Jue K, Mohrmann R. Isolated non-compaction of left ventricular myocardium. A study of eight cases. Circulation 1990;82:507-513.

3. Stollberger C, Finsterer J. Left ventricular hypertrabeculation/noncompaction. J Am Soc Echocardiogr 2004;17:91-100.

4. Rigopoulos A, Rizos IK, Aggeli C, et al. Isolated left ventricular non-compaction: an unclassified cardiomyopathy with severe prognosis in adults. Cardiology 2002;98:25-32.

5. Ichida F, Hamamichi Y, Miyawaki T, et al. Clinical features of isolated noncompaction of the ventricular myocardium: long-term clinical course, hemodynamic properties, and genetic background. J. Am Coil Cardiol 1999;34:233-240.

6. Murphy RT, Thaman R, Blanes JG, et al. Natural history and familial characteristics of isolated left ventricular non-compaction. Eur Heart J 2005;26:187-192.

7. Jenni R, Wyss CA, Oechslin EN, et al. Isolated ventricular noncompaction is associated with coronary microcirculatory dysfunction. J Am Coll Cardiol 2002;39:450-454.

8. Oechslin EN, Attenhofer Jost CH, Rojas JR, Kaufmann PA, Jenni R. Long-term follow-up of 34 adults with isolated left ventricular noncompaction: a distinct cardiomyopathy with poor prognosis. J Am Coll Cardiol 2000;36:493-500.

9. Jenni R, Oechslin E, Schneider J, et al. Echocardiographic and patho-anatomical characteristics of isolated left ventricular non-compaction: a step towards classification as a distinct cardiomyopathy. Heart 2001;86:666-671.

10. Stollberger C, Finsterer J, Blazek G. Left ventricular hypertrabeculation/noncompaction and association with additional cardiac abnormalities and neuromuscular disorders. Am J Cardiol 2002;90:899-902.

11. de Groot-de Laat LE, Krenning BJ, ten Cate FJ, et al. Usefulness of contrast echocardiography for diagnosis of left ventricular noncompaction. Am J Cardiol 2005;95:1131-1134.

12. Petersen SE, Selvanayagam JB, Wiesmann F, et al. Left ventricular non-compaction: insights from cardiovascular magnetic resonance imaging. J Am Coll Cardiol 2005;46:101-105.

If children grew up according to early indications, we should have
nothing but geniuses.
--Johann Wolfgang von Goethe

Angelos Rigopoulos, MD, Ioannis Rizos, MD, and Dimitrios T. Kremastinos, MD

From the Second Department of Cardiology, University of Athens Medical School, Attikon University Hospital, Athens, Greece.

Reprint requests to Dr. Angelos Rigopoulos, Empedokleous 46, 11632 Athens, Greece. Email: [e-mail]

Accepted May 16, 2006.