During my training as a pediatric cardiologist, I recall standing at the bedside of an ill newborn as an echocardiogram was being performed. My attending physician pointed out the findings of a rare entity that he termed “spongy myocardium.” He had seen it only several times in his career, and surely this was my first encounter with the diagnosis. This condition was first described in 1966 in a publication in which dense trabeculations (termed “persistenz myokardialer Venensinusoide”) were seen at cardiac catheterization on left ventriculography, with clefts extending deep into the myocardium. Since then, we have come to recognize spongy myocardium by a variety of names, which have included “immature myocardium,” “hypertrabeculation of the myocardium,” and “myocardial spongiosum.” In 1990, Chin et al coined the term “noncompaction of the left ventricle,” and this has now become the accepted nomenclature for this condition. The diagnosis of left ventricular noncompaction (LVNC) has gained wider acceptance as a discrete entity since its inclusion as a separate class of cardiomyopathies by the American Heart Association in the 2006 scientific statement by Maron et al. In fact, population surveys suggest that LVNC may constitute as many as 10% of all cardiomyopathic patients.
And so the question arises: are we seeing a new condition, or is this a newfound recognition of a disease that has always been present? This question has been posed numerous times over the past decade. Paul Lurie tabulated the growth in interest that has developed over the past several decades. His review of the literature found scant references (<5 per year) between 1990 and 1999, with an exponential increase in publication number beginning in 2000. Lurie’s interest in myocardial development was prescient: he wrote in the 1968 edition of Moss and Adams’s textbook Heart Disease in Infants, Children and Adolescents ,
The hearts of primitive vertebrates, such as the hagfish, are formed of interlacing muscle fibers bathed in the same pool of blood that they pump. In the early embryonic life of the higher vertebrates, a similar condition exists, in which the heart wall is a loose meshwork of developing myocardial fibers. Relatively large spaces between the muscle trabeculations contain blood which circulates back and forth from the cavities with the heart beat. With gradual condensation of the myocardium, most of these spaces become flattened sinusoids, while some remain as deep clefts continuous with the ventricular cavities.
LVNC had not yet been described, but the understanding of embryologic determinants for the transition from a noncompacted to a compacted myocardial layer was well in place.
My own cursory PubMed literature search for the term “noncompaction” confirms a continued dramatic increase in the volume of case reports, scientific articles, and reviews over the past 10 years ( Figure 1 ). On the basis of “around the water cooler” conversations, it appears that those of us who care for these patients can certainly provide anecdotal theories regarding the explosion in the number of patients who are being diagnosed with LVNC. One plausible explanation entails the vast improvement in echocardiographic technology. Image resolution has allowed us to define details of cardiac structure unimaginable only a few short years ago. In addition, we have available to us numerous novel modalities (3-dimensional imaging, Doppler techniques, and cardiac magnetic resonance [MR] imaging) that have broadened our diagnostic capabilities but also have required us to develop a new set of norms. With these imaging methods, we are able to see entirely different (and better) views of the heart. However, these images result in the increasingly common question as to whether we are seeing a “normal” heart, a “normal variant,” or frank cardiac pathology. In addition, with breakthroughs in the understanding of the genetic basis of cardiac development, we are performing echocardiographic imaging on individuals with defined genetic anomalies and familial conditions to determine markers for risk for cardiac pathology. We are seeing autosomal dominant, x-linked inheritance, as well as sporadic cases of LVNC. Mutations have been found in genes coding for G4.5 (the tafazzin protein gene), α-dystrobrevin, and LIM domain protein 3. But in spite of this wealth of information at our fingertips, every cardiologist is still faced with the question of what are the criteria necessary to confer the diagnosis of LVNC.
Left Ventricular Noncompaction: Diagnostic Criteria
Jenni et al provided us with a working algorithm for the diagnosis of LVNC. This includes the following criteria:
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absence of coexisting cardiac structural abnormalities that would be expected to result in excessively high ventricular pressure;
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numerous, excessively prominent trabeculations and deep intertrabecular recesses supplied by intraventricular blood identified using color Doppler echocardiography;
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myocardial changes predominantly confined to the apical and mid left ventricular posterior wall segments (typically these regions are hypokinetic); and
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an end-systolic ratio of thick noncompacted layer to thin compacted layer > 2.
Although these criteria prove helpful in aiding us in the diagnosis of straightforward cases of LVNC, we continue to struggle with those patients who have some but not all of the criteria. The application of additional imaging techniques has assisted with these borderline cases.
Additional Imaging Techniques to Elucidate the Diagnosis
A variety of alternative imaging modalities as well as echocardiographic tools have been studied in an attempt to improve diagnostic accuracy. Cardiac MR imaging has proven accurate with segmental distribution of the disease process analogous to that found via assessment of pathologic specimens and echocardiographic imaging. The highest sensitivity, specificity, and predictive values are found when the noncompacted/compacted ratio is >2.3 during diastole (as opposed to the 2:1 ratio during systole used for echocardiographic diagnosis). MR has been less necessary as an alternative imaging strategy in children, because of greater ease in obtaining clear wall definition using echocardiography.
In studies with small numbers of patients and case reports, contrast echocardiography as well as three-dimensional echocardiographic imaging have helped augment our standard diagnostic tools and have aided in the imaging evaluation of these patients. It is clear that in specific situations, we must use creativity in taking advantage of all of the resources at our disposal in the echocardiography laboratory. As Doppler tissue imaging and strain and strain rate assessments become routine, we will surely use these to assist with LVNC diagnosis and management. These techniques have already been brought to bear in our attempts to gain a better understanding of the regional mechanical properties found in this population. Over the past few years, there have been numerous published studies on the use of tissue Doppler and strain in the assessment of these patients; a comprehensive and well-written review was provided recently by Eidem, describing the application of this emerging technology in LVNC.
Because LVNC is being increasingly recognized ( Figure 1 ), and because diagnostic methods and criteria vary, it is appropriate for those making diagnoses of LVNC to specify the methods and diagnostic findings, along with literature references.
Additional Imaging Techniques to Elucidate the Diagnosis
A variety of alternative imaging modalities as well as echocardiographic tools have been studied in an attempt to improve diagnostic accuracy. Cardiac MR imaging has proven accurate with segmental distribution of the disease process analogous to that found via assessment of pathologic specimens and echocardiographic imaging. The highest sensitivity, specificity, and predictive values are found when the noncompacted/compacted ratio is >2.3 during diastole (as opposed to the 2:1 ratio during systole used for echocardiographic diagnosis). MR has been less necessary as an alternative imaging strategy in children, because of greater ease in obtaining clear wall definition using echocardiography.
In studies with small numbers of patients and case reports, contrast echocardiography as well as three-dimensional echocardiographic imaging have helped augment our standard diagnostic tools and have aided in the imaging evaluation of these patients. It is clear that in specific situations, we must use creativity in taking advantage of all of the resources at our disposal in the echocardiography laboratory. As Doppler tissue imaging and strain and strain rate assessments become routine, we will surely use these to assist with LVNC diagnosis and management. These techniques have already been brought to bear in our attempts to gain a better understanding of the regional mechanical properties found in this population. Over the past few years, there have been numerous published studies on the use of tissue Doppler and strain in the assessment of these patients; a comprehensive and well-written review was provided recently by Eidem, describing the application of this emerging technology in LVNC.
Because LVNC is being increasingly recognized ( Figure 1 ), and because diagnostic methods and criteria vary, it is appropriate for those making diagnoses of LVNC to specify the methods and diagnostic findings, along with literature references.
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