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Left ventricular noncompaction cardiomyopathy.

INTRODUCTION

A 62-year old-male presented to the hospital following a two-week history of dizziness, weakness, and dyspnea upon exertion. He denied chest pain, fever, chills, nausea, and vomiting. As a poor historian and currently homeless, the patient reported a medical history of only prior alcoholism and ongoing untreated diabetes and hypertension, secondary to noncompliance. At the time of presentation, blood pressure was recorded at 168/123 and pulse was 110. An electrocardiogram was interpreted to have ST-depressions with Q waves in V4 through V6 and mild ST elevation in V2 to V3 with a minimal elevation in aVR. Cardiac troponin was elevated at 0.59 ng/ml with a normal total CK and normal CKMB. He was referred for left heart catheterization, ventriculogram, and coronary angiography, which revealed severe multivessel coronary artery disease and ischemic cardiomyopathy with a left ventricular ejection fraction of approximately 20%, along with severe global hypokinesis. He underwent a right heart catheterization, and an intraaortic balloon pump was placed. On hospital day seven, he received emergent four vessel bypass grafting. Postoperatively, he continued with biventricular failure requiring placement of a ventricular assist device. On postoperative day seven, he was transferred to an outlying facility for possible heart transplant. He died three days following transfer. Unrestricted autopsy permission was granted by the coroner's office

At the time of autopsy, cardiac findings included a 720 gm heart with a 2.8 cm left ventricular free wall consisting of an inner spongy (noncompacted) layer (2.1 cm) and an outer compact layer of myocardium (0.7 cm). The ratio of noncompacted to total wall thickness was 75%. The spongy layer consisted of anastomosing trabeculae without well-formed papillary muscles and was most prominent in the apex and the mid-ventricular walls, with the exception of the septum. Histologically, the trabeculae making up the spongy layer formed staghorn-like deep recesses that were lined by endothelial cells. Prominent subendocardial fibrosis was also noted.

DISCUSSION

Isolated Left Ventricular Non Compaction Cardiomyopathy (LVNCC) is a rare disorder originally described in 19901 but not further classified as a primary genetic cardiomyopathy until 2006 by the American Heart Association. (2) The prevalence of LVNCC among patients undergoing echocardiographic examination and among patients with heart failure has been previously estimated at 0.014 and 3% to 4%, respectively. (3,4) Very recently, Paterick et al. have suggested that as awareness of this diagnosis grows, there may be an excessively elevated sensitivity inherent to the echocardiographic criteria for LVNCC, thus resulting in an excessive number of false positive cases. (5) With such confusion surrounding the antemortem diagnostic criteria, it is not uncommon for the initial diagnosis of LVNCC to be made pathologically at the time of autopsy examination, as is shown in the current case. (6)

Clinical signs and symptoms associated with LVNCC vary and range from a lack of symptoms to severe manifestations including significant (class III or IV) heart failure, sustained ventricular arrhythmias, cardioembolic events, and sudden death. In its isolated, non-syndromic form, LVNCC occurs most frequently in adults with an average age at the time of diagnosis of 42 years and is twice as common in men. Dyspnea is reportedly the most common initial presenting symptom, occurring in less than 2/3 of patients. Other complaints include chest pain, syncope, and weakness. In one prospective study of 34 adult patients with LVNCC, the initial 12lead electrocardiogram (ECG) was abnormal in 94% of patients, with the most common finding being left bundle branch block. Over the course of an average of 44 [+ or -] 39 months, the authors report pulmonary emboli in 9%, systemic embolic events in 21%, ventricular tachycardia in 41%, and significant heart failure either necessitating transplantation or causing death in 24% of patients. (3)

Standards for the diagnosis of LVNCC by echocardiogram are not yet universally established, though the body of literature offering various schemes for cardiac echo and/ or magnetic resonance diagnosis of LVNCC is growing. Generally acceptable indices for LVNCC consideration by cardiac imaging include demonstration of 1) two ventricular layers: the outer compacted and inner noncompacted zone with a maximum ratio of noncompacted to compacted myocardium >2:1 at end-systole in the parasternal short-axis view; 2) deep trabeculations in the left ventricular apex or midventricular segments of the inferior and lateral wall; and 3) color Doppler evidence of flow within the deep muscular recesses. (7)

Morphologic features used in the pathologic diagnosis of LVNCC include excessively prominent trabeculae and deep intertrabecular recesses that are most notable in apical segments of the left ventricle and which result in an overall thickened left ventricular wall >1.5 cm in thickness. Continuity between these inter-trabecular recesses and the left ventricular main chamber should also be established. (8) Histologic evidence for continuity between the recesses and the ventricular chamber has been shown by demonstration that the recesses are lined by endothelial cells, as is the case along all endocardial surfaces in each of the four cardiac chambers. (1) The coarse and broad trabeculae that are seen in LVNCC take the place of the normally conspicuous anterior and posterior papillary muscles that anchor the chordae tendinae of the three cusps of the mitral valve. The two discrete ventricular layers found in LVNCC should be characterized by an inner (periventricular), spongy, noncompacted layer that lies beneath the outer, more notably dense compact layer. The ratio of the noncompacted layer to the total wall thickness in the involved region should be >50%. (8,9) Histologic examination of the left ventricular myocardium has shown variable features from myocyte necrosis to replacement fibrosis and endocardial fibroelastosis. (6,10)

Just as awareness of this rare clinical entity increases, so do the etiologic studies aimed at elucidating the pathogenesis of LVNCC. More recent reports have revealed that LVNCC, in its isolated form, is genetically heterogeneous and thought to occur both sporadically, as well as in a familial, most often autosomal dominant, pattern. (11) At least nine genes have been purported to harbor mutations in cases of isolated LVNCC, including genes that code for cardiac muscular cytoskeletal proteins and the alpha-cardiac actin (ACTC) gene, which has also been a gene implicated in other cardiomyopathies such as familial hypertrophic cardiomyopathy. Generally, though, it is believed that LVNCC arises from a developmental failure or intrauterine arrest of cardiac maturation in its compact muscular layer during embryonic weeks five through eight. (12) Additional reports of LVNCC with multi-perspective characterization; including clinical, cardiac, electrophysiologic, radiographic, genetic, and pathologic, both gross and histologic; will be important as we continue the current momentum towards better awareness, diagnostic precision and, ultimately, appropriate management aimed at preventing the long-term sequelae attributed to this rare primary cardiomyopathy.

ACKNOWLEDGEMENTS

The authors would like to gratefully acknowledge the support of the Orleans Parish Coroner's Office: Dr. Frank Minyard, Chief Investigator John Gagliano, and Ms. Julia Powers for providing the case material for this report.

REFERENCES

(1.) Chin TK, Perloff JK, Williams RG, et al. Isolated noncompaction of left ventricular myocardium: a study of eight cases. Circulation 1990; 82(2):507.

(2.) Maron BJ, Towbi JA, Thiene G, et al. Contemporary definitions and classification of the cardiomyopathies. Circulation 2006; 113:1807.

(3.) Oechslin EN, Attenhofer Jost CH, Fojas JR, et al. 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.

(4.) Kovacevic-Preradovic T, Jenni R, Oechslin EN, et al. Isolated left ventricular noncompaction as a cause for heart failure and heart transplantation: a single center experience. Cardiology 2009; 112:158.

(5.) Paterick, TE, Umland MM, Jan MF, et al. Left ventricular noncompaction: A 25-year odyssey. J Am Soc Echocardiogr 2012;25(4): 363.

(6.) Li L, Burke A, Zhang X and Fowler D. Sudden unexpected death due to left ventricular noncompaction of myocardium. Am J For Med Pathol 2010; 31(2):122.

(7.) Jenni R, Oechslin E, Schneider J, et al. Echocardiographic and pathoanatomical characteristics of isolated left ventricular non-compaction: a step towards classification as a distinct cardiomyopathy. Heart 2001; 86(6)666.

(8.) Ritter M, Oechslin E, Sutsch G, et al. Isolated noncompaction of the myocardium in adults. Mayo Clin Proc 1997; 72:26.

(9.) Burke A, Mont E, Kutys R and Virmani R. Left ventricular noncompaction: a pathological study of 14 cases. Hum Pathol 2005; 36:403.

(10.) Finsterer J, Stollberger C, Feichtinger H. Histological appearance of left ventricular hypertrabeculation/noncompaction. Cardiology 2002; 98(3): 162.

(11.) Zaragoza MV, Arbustini E, Narula J. Noncompaction of the left ventricle: primary cardiomyopathy with an elusive genetic etiology. Curr Opin Pediatr 2007; 19:619.

(12.) Henderson DJ, Anderson RH. The development and structure of the ventricles in the human heart. Pediatr Cardiol 2009; 30:588.

Kelley Willis Sherling, MD; Theresa Nuttli, MD; William P Newman III, MD; Robin R. McGoey, MD

In the Department of Pathology at the Louisiana State University Health Sciences Center in New Orleans, Dr. Sherling is a third-year Pathology Resident, Dr. Nuttli is a second-year Pathology Resident, Dr. Newman is a Professor of Pathology and Director of the Autopsy Service, and Dr. McGoey is Associate Professor of Pathology and Residency Program Director.
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Author:Sherling, Kelley Willis; Nuttli, Theresa; Newman, William P., III; McGoey, Robin R.
Publication:The Journal of the Louisiana State Medical Society
Article Type:Clinical report
Geographic Code:1USA
Date:May 1, 2013
Words:1515
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