A Case of Isolated Right Ventricle Noncompaction with ST-Elevation Chest Leads.

Non-compaction of ventricular myocardium (NCVM) is a rare genetic disorder caused by intrauterine arrest of endomyocardial development. Left ventricle is the usual site of NCVM with very rare reports of isolated right ventricular non-compaction (IRVNC). We describe a case of asymptomatic IRVNC with unique EKG changes.

INTRODUCTION

Isolated right ventricular noncompaction (IRVNC) is a very rare disorder Electrocardiographic (EKG) changes associated with it have never been described before. Noncompaction of the ventricular myocardium (NCVM) is a rare disorder caused by the intrauterine arrest of endomyocardial development and affects both children and adults.[1]

World Health Organization/International and Federation of Cardiology Task Force categorized NCVM as a “unclassified cardiomyopathy” in 1995.[2] American Heart Association in its scientific statement in 2006 classified it under the “genetic” section of “primary cardiomyopathies”.[3] The exact prevalence of NCVM in the adult population is unknown, but has been estimated to be between 0.014% and 0.045% of all patients referred for echocardiography.[45] The actual prevalence might be much higher. Left ventricle (LV) is the usual site of NCVM, with/without involvement of right ventricle (RV) and other congenital heart disease.[4567] However, IRVNC has been rarely reported.[8910111213] We describe a unique case of asymptomatic patient IRVNC with abnormal EKG finding.

CASE REPORT

A 51-year-old gentleman presented to our clinic for cardiovascular evaluation after an abnormal EKG at his primary care physician's office. He was asymptomatic and denied any complaints. His past history was significant for hyperlipidemia, for which he was taking simvastatin. There was no significant past surgical history. He was a former smoker and denied any use of alcohol or illicit drug. His family history was unremarkable.

On examination, his heart rate (HR) was regular, with normal heart sounds and without any murmurs, rubs or gallops. The rest of the physical examination was unremarkable.

Initial EKG showed normal sinus rhythm, bradycardia with HR 59 beats/min, normal QRS duration, with poor R-wave progression and ST segment elevation in leads V1–V3 [Figure 1]. Chest X-ray showed normal cardiac silhouette. Two-dimensional transthoracic echocardiography (TTE) showed spongy RV with hypertrophied trabeculae and deep inter-trabecular recesses in RV without any signs of hypokinesia. LV was normal in appearance and function without any trabeculation. There were no valvular and pericardial abnormality. Transesophageal echocardiography was done for further visualization which revealed spongy appearance of the RV with trabeculations forming deep fissures and grooves, located in the RV apical wall consistent with apical noncompaction in RV [Figure 2].

Figure 1

Initial electrocardiography revealing ST segment elevation in leads V1–V3

Figure 2

Transesophageal echocardiography image revealing spongy appearance of the right ventricle with trabeculations forming deep fissures and grooves, located in the right ventricle apical wall

No other cardiovascular abnormality was present. Contrast echo demonstrated flow from RV cavity into the trabecular recesses [Figure 3]. A follow-up TTE was done a year later and no changes were noticed. The patent stays asymptomatic till date.

Figure 3

Transesophageal echocardiography contrast echo demonstrating flow from right ventricular cavity into the trabecular recesses

DISCUSSION

Noncompaction of ventricular myocardium is a rare disorder now classified as a genetic primary cardiomyopathy.[3] During normal fetal development, ventricles initially are a meshwork of interwoven fibers and between 5th and 8th week, ventricular compaction occurs from the base towards the apex and from epicardium to endocardium.[11] During compaction, inter-trabecular spaces in ventricular myocardium are obliterated and the recesses in the trabecular network are reduced to capillaries.[11] Failure of this endocardial morphogenesis and regression of ventricular sinusoids results in ventricular noncompaction.[1112]

The exact pathophysiology of ventricular dysfunction is unclear, but it has been suggested that subendocardial hypoperfusion and coronary microcirculatory dysfunction are a cause of arrhythmogenesis and fibrosis.[14] We have earlier described association of myocardial fibrosis with NCVM.[7]

Isolated right ventricular noncompaction has been rarely reported in literature. This, to the best of our knowledge, is the first ever reported case with asymptomatic patient and with EKG changes of ST elevation in V1–V3 leads. The previous reported cases of IRVNC have described it with symptoms of right heart dysfunction,[9111213] palpitations,[10] and neurological symptoms.[8]

No specific criterion has been proposed for the diagnosis of IRVNC to date. The following diagnostic criteria for isolated left ventricular noncompaction (ILVNC) have been used in literature: (i) The absence of coexisting cardiac anomalies; (ii) a two-layered structure of LV wall, with the end-systolic ratio of the noncompacted to compacted myocardial layer > 2; (iii) finding this structure predominantly in the apical and mid-ventricular areas; and (iv) blood flow directly from the ventricular cavity into deep inter-trabecular recesses as assessed by Doppler echocardiography.[4] In the absence of clear cut criterion, the above mentioned criteria had been used earlier by authors,[1112] and similarly by us for this case. The ratio of noncompacted to compacted myocardium >2.3, as measured at end diastole in the long axis views was used by Zhang et al., and Chiribiri et al.,[910] and presence of marked trabeculations and inter-trabecular recess was used by Ying et al.,[8]

Our patient was diagnosed on the basis of transesophageal echocardiography. In our patient, all four echocardiographic criteria of IRVNC were present. There were no coexisting cardiac anomalies. Kohli et al., has classified noncompaction into three morphological categories namely; spongy, meshwork, and prominent trabeculations only.[15] In our case, noncompaction belongs to prominent trabeculations only type.

To better define the noncompaction, other diagnosing modalities such as contrast ventriculography, computed tomography and magnetic resonance imaging (MRI) have been used.[16] MRI has been shown to provide good correlation with echocardiogram for localization and extent of noncompaction and has been found to be useful in cases with poor echocardiography quality.[17] The demonstration of differences in MRI signal intensity in NCVM may also help identify substrate for potentially legal arrhythmia.[18] In our patient, MRI was done which ruled out presence of any underlying arrhythmogenic right ventricular cardiomyopathy.

Both familial and nonfamilial cases NCVM have been described. In the isolated form of NCVM, ZASP (Z-line) and mitochondrial mutations and X-linked inheritance resulting from mutations in the G4.5 gene encoding tafazzin (including association with Barth syndrome in neonates) have been reported. Noncompaction associated with congenital heart disease has been shown to result from mutations in the α-dystrobrevin gene and transcription factor NKX2.5.[3] Because of the risk of familial occurrence, a few authors have recommended screening of first-degree relatives by echocardiography to identify asymptomatic patients.[411]

Although EKG is found to be abnormal in about 87–94% of patients with IVNC, none of these changes are specific.[419] The most common finding was intra-ventricular conduction delay.[420] However, other abnormalities including left ventricular hypertrophy changes, repolarization changes, Wolff Parkinson White syndrome and atrial fibrillation have been reported.[192021] In patients with IRVNC, EKG changes including normal sinus rhythm and atrial fibrillation with complete right bundle branch has been reported.[913] There has been a single case of reported of NCVM with ST elevation changes in V1–V3 leads.[22]

There are no long term follow-up studies to date of patients with IRVNC. In a long-term follow-up of 34 patients with ILVNC by Oechslin et al., features of noncompaction were found predominantly in apical and mid-ventricular segments of both inferior and lateral walls in > 80% of the patients.[4] Endomyocardial morphology in NCVM is responsible for the development of mural thrombi within the inter-trabecular spaces. Oechslin et al. recommended that all adult patients with ILVNC be on oral anticoagulation irrespective of ventricular functions.[4] There is no evidence however, for similar approach on patients with IRVNC.

There are no prognostic criteria proposed for patients with IRVNC. ILVNC patients had variable prognosis, ranging from prolonged asymptomatic course to severe cardiac disability, leading to heart transplantation and death. Approximately 50% of the patients died suddenly.[4] The worse prognostic indicators include patients with heart failure New York Heart Association classes III–IV, the LV end diastolic diameter >60 mm, the left bundle branch block, chronic atrial fibrillation, a ratio of noncompacted to compacted myocardium >3 and involvement of three or more segments.[45]

Our knowledge on patients with IRVNC is still benign and based on a few case reports. In the absence of studies on IRVNC, our understanding of etiopathogenesis and prognosis mostly depends on studies on ILVNC. However, definite studies might be needed before prophylactic anticoagulation is initiated for IRVNC cases as recommended for ILVNC patients. To date our patient has been asymptomatic 2 years since diagnosis.

CONCLUSION

We describe here a case IRVNC presented as ST segment elevation in leads V1-V3. This, to the best of our knowledge is first ever reported case of asymptomatic patient with EKG changes and IRVNC. Our understanding of this entity will improve as more and more cases are diagnosed. Clinicians should have high index of suspicion for diagnosis of IRVNC.