“Spongy Myocardium”: Left ventricular non compaction A case report and a brief overview

Introduction

Ventricular non compaction is an uncommon cause of end stage heart failure in adults. This condition is also associated with significant risk of developing life threatening cardiac arrhythmias and thrombo-embolic events. ¹   Accurate diagnosis of this fascinating condition and differentiating it from other forms of cardiomyopathy is important to reduce morbidity and mortality. We report a case of isolated left ventricular non compaction and a brief overview regarding this interesting condition.

Case

A 27-year-old woman presented with symptoms of progressive dyspnea on exertion and lower extremity swelling of one month duration. She complained of dry cough with no associated wheezing, chest tightness, fever or chills. There was no family history of any cardiac disease. On presentation her heart rate 90/min, blood pressure 120/70, respiratory rate 16/min. and pulse oximetry of 98% on room air. Physical examination revealed no jugular venous distension, normal heart sounds, no murmurs, bilateral coarse chest crackles and +2 pitting pedal edema. There was no facial dysmorphism. Electrocardiography demonstrated normal sinus rhythm, with normal QRS duration and no ST segment changes. Chest roentgenogram was consistent with congestive heart failure with mild cardiomegaly. Tranthoracic echocardiography revealed severely dilated left ventricle with an ejection fraction of 11%; mild left atrial enlargement and multiple left ventricular myocardial trabeculations and deep intertrabecular recesses filled with blood from the ventricular cavity; findings suspicious of ventricular non compaction (Figure 1,2). EKG gated cardiac computer tomography demonstrated an enlarged heart with both dilated left and right ventricles. The left ventricular myocardium appeared thin with some excessive trabeculations with a deep intra-trabecular recess along the basal, lateral and apical walls of the left ventricle. These recesses were filled with contrast material and were in communication with the left ventricle. There were also prominent trabeculations in the apical regions of the right ventricle (Figure 3). Evaluation of the coronary arterial tree revealed a traditional anatomy with a right dominant system which was patent. No significant plaque or stenosis was identified within the left main coronary artery, left anterior descending artery or circumflex coronary artery.

The patient was diagnosed with isolated ventricular non compaction (LVNC) based on the appearance of the left ventricular myocardium and absence of other associated cardiac anomalies on EKG gated cardiac computer tomography. The patient was treated medically with carvedilol, lisinopril, spironololactone and warfarin. Despite optimization of medical therapy she continued to be symptomatic. An automated implantable cardio-defibrillator was placed three months later and she was referred for cardiac transplantation.

Discussion

LVNC is characterized by prominent trabeculations and deep intertrabecular recesses that extend into the ventricular wall without any communication with the coronary circulation. ²  It was first described in 1984, later categorized as an unclassified cardiomyopathy as per world health organization classification in 1995. The American Heart Association’s 2006 classification of cardiomyopathies considers ventricular noncompaction a genetic cardiomyopathy. ³  The prevalence of this disorder has been reported to be about 0.06 to 0.3%. ⁴  However a recent large case series demonstrated a high percentage of patients with heart failure fulfilling current echocardiography criteria of LVNC. ⁵

Two forms of this anomaly have been described 1) LVNC-associated with congenital heart diseases and 2) Isolated LVNC-absence of other cardiac anomalies. Isolated LVNC has become the topic for recent debate with several conflicting views on its pathogenesis. The mechanism that leads to LVNC is unclear; some consider it to be an adaptive response to poor systolic function and altered ventricular load. ⁶  However, the most widely accepted hypothesis is the arrest in the gradual compaction of the ventricular myocardium during embryogenesis at 5-8 weeks of fetal life results in the persistence of multiple prominent ventricular trabeculations and deep intertrabecular recesses. ¹  A genetic basis of the disease is suggested at least by the finding that first degree relatives of affected people also have cardiomyopathy. Familial patterns of inheritance described are X-linked, autosomal dominant, mitochondrial in children and autosomal dominant inheritance pattern in adults. ^{7 8}  Several gene mutations have reported including LIM domain binding protein 3, taffazin, α dystrobrevin, and lamin A/C to be associated with LVNC and the search for other genes is still ongoing. ^{9 10 11}

Clinical complications from LVNC include arrhythmias, heart failure and thrombo-embolic events. An extensive review of literature demonstrate that more than 50% patients with LVNC develop symptomatic heart failure. ^{2 7}  Both systolic and diastolic dysfunction has been noted. Common electrocardiographic abnormalities associated with LVNC are left ventricular hypertrophy, non specific repolarization changes, ST segment changes and intraventricular conduction defects. Arrhythmias that are associated with LVNC include atrial fibrillation (25%), ventricular tachyarrhythmias, paroxysmal supraventricular tachycardia, complete heart block and sudden cardiac death. A sudden cardiac death is responsible for majority of the deaths in patients with noncompaction. ^{1 2 12}

Echocardiography is the diagnostic test of choice but other imaging modalities such as magnetic resonance imaging, cardiac computer tomography and contrast ventriculography have been used. ¹³  Multiple ventricular trabeculations, the presence of deep intertrabecular recesses, and blood flow through the ventricular cavity and deep recesses are diagnostic. Several echocardiographic definitions have been proposed but the diagnostic criteria by Chin et al, Stollberger et al and Jenni et al. have been widely used. ^{1 14 15}  A recent study by Kohli et al in 2009 has demonstrated an unexpectedly high percentage of patients with heart failure fulfilling current echocardiographic criteria for LVNC leading to over diagnosis of the condition. ⁵  There is sufficient evidence to say that the current diagnostic criteria in the diagnosis of LVNC is imperfect; so combining different criteria may help to increase accuracy in diagnosing this rare form of cardiomyopathy. ¹⁶  As compared to echocardiography and cardiac magnetic resonance imaging, there are only a few reported cases of the diagnosis of LVNC using EKG gated cardiac computer tomography in the literature. ¹⁷  This imaging modality yields higher resolution images of the intracardiac structures. The ability to retrospectively reprocess imaging data in any imaging plane at any phase of the cardiac cycle makes EKG gated cardiac computer tomography to be an extremely flexible and a superior mode of imaging in the diagnosis of LVNC. ¹⁸  Although it is potentially limited by the ionizing radiation dose and intravenous contrast administration, EKG gated cardiac computer tomography is a relatively inexpensive tool which can provide a broad range of valuable clinical information.

Table 1:  Clinical features of LVNC

1. Heart failure:
   • Systolic or diastolic
2. Tachyarrhythmias:
   • Atrial fibrillation
   • Paroxysmal supraventricular tachycardia
   • Ventricular tachyarrhythmias
3. Conduction abnormalities:
   • Bundle branch block
4. Thrombo-embolic events:
   • Cerebral

Table 2: Differential diagnosis

1. Normal variant: Trabeculations seen on echocardiogram routinely. However, these are few in number (<3), rarely located in the apical region.
2. Hypertrophic cardiomyopathy
3. Dilated cardiomyopathy
4. Apical left ventricular thrombus
5. Arrhythmogenic right ventricular cardiomyopathy
6. Endocardial fibroelastosis

1. Stollberger et al. (20)
   1. More than three trabeculations protruding from the left-ventricular wall, apical to the papillary muscles, visible in a single image plane.
   2. Intertrabecular spaces perfused from the ventricular cavity,visualized on color Doppler imaging
2. Jenni et al. (19)
   1. LVNC is defined by a ratio of N/C>2 N= non-compacted layer of myocardium C= compacted layer of myocardium A two-layer structure, with a thin compacted layer and a thick non-compacted layer measured in end systole at the parasternal short-axis views.
   2. Absence of other co-existing cardiac structural abnormalities
   3. Numerous, excessively prominent trabeculations and deep intratrabecular recesses
   4. Recesses supplied by intraventricular blood on color Doppler
3. Chin et al. (1)
   1. LVNC is defined by a ratio of X/Y <=0.5
   2. X=distance from the epicardial surface to the trough of the trabecular recess
   3. Y=distance from the epicardial surface to peak of trabeculation
   4. These criteria focus on trabeculae at the LV apex on the parasternal short axis and apical views, and on left-ventricular free-wall thickness at end-diastole

Management of LVNC includes treatment for heart failure, arrhythmias, and thromboembolic events. Implantation of an automated implantable cardio-defibrillator is indicated for secondary prophylaxis after documented sustained ventricular tachycardia or severely impaired left ventricular function. ¹⁹  No criteria exist for primary prophylaxis in patients that might be at high risk. ²⁰  Early listing for heart transplantation should be considered in patients with end stage congestive heart failure and severe symptoms. Long-term prophylaxis with oral anticoagulants appears beneficial in all cases with LVNC and is especially mandatory when impaired left ventricular function, thrombi or atrial fibrillation have been documented. ¹⁷  Genetic studies are not yet routinely recommended but echocardiographic screening of family members is suggested. ^{8 17}  The prognosis of symptomatic LVNC is debatable but is thought to be associated with considerable morbidity and mortality. ^{12 17}

Conclusion

Although the diagnostic criteria for LVNC are imperfect, there is good evidence that pathological hypertrabeculation is a concerning clinical entity. Early and accurate diagnosis of this interesting condition is essential as the condition may require genetic counseling and echocardiographic screening of first-degree relatives and can be associated with significant morbidity and mortality. Future studies are required to improve the diagnostic criteria on echocardiography. Until then, the use of other adjuvant imaging studies such as cardiac computer tomography and magnetic resonance imaging supporting the echocardiography findings is essential. EKG gated computer tomography is an extremely useful adjuvant tool in diagnosing LVNC as it is able to demonstrate the abnormal architecture of the left ventricle and also evaluate the coronary arteries for any underlying pathology which is not possible by other modes of imaging.