Isolated right ventricular noncompaction caused ventricular tachycardia and pulmonary embolism

Abstract Isolated ventricular noncompaction is an unclassified cardiomyopathy due to intrauterine arrest of compaction of the loose interwoven meshwork. Its mortality and morbidity are high, including heart failure, thromboembolic events, and ventricular arrhythmias. Isolated right ventricular noncompaction was reported rarely, especially that causes pulmonary embolism and ventricular tachycardia. We describe a case of isolated noncompaction of the right ventricular causing pulmonary embolism and ventricular tachycardia.


| INTRODUC TI ON
Ventricular noncompaction (VNC) is a rare congenital heart disease that results from an abnormal arrest in endomyocardial embryogenesis. It is characterized by the presence of prominent ventricular myocardial trabeculations and deep intratrabecular crypts, which normally ventricular myocardial trabeculations usually involves in the left ventricular(LV) apex while rare in the bi-ventricles or right ventricle (RV) (Weiford, Subbarao, & Mulhern, 2004).We present a case of isolated right ventricular noncompaction (iRVNC) presenting as ventricular tachycardia (VT) and pulmonary embolism (PE).

| C A S E REP ORT
A 20-year-old man presented with repeated amaurosis and progressive dyspnea for the past 6 months. He was never found to have any heart diseases, relevant history of familial heart diseases, and risk factors for pulmonary embolism in the past. On examination, his blood pressure was 112/68 mmHg, pulse 104 beats per minute. The lips appeared cyanosis, and the jugular vein was filling together with negative liver-jugular vein backflow sign (−). His bi-lung breath sounded clear, and the heartbeat sounded strong with regular heart rhythm, P2 > A2; valve auscultation did not appear any noise, and the both lower extremities showed mild edema. D-dimer 2.80 g/ml (0-0.3 g/ml), blood gas analysis: arterial oxygen partial pressure 66 mmHg (75-100 mmHg), arterial carbon dioxide partial pressure 38.6 mmHg (35-45 mmHg). Brain In the electrophysiology laboratory, rapid ventricular pacing induced the clinical VT. Implantable cardioverter-defibrillator was recommended, while the patient and his parents refused resolutely.
Electroanatomic mapping and pace mapping located the VT origin to the right ventricular inferior wall. Radiofrequency ablation induced VT at this site; after several radiofrequency ablation applications, VT was no longer inducible. Besides, the patient was treated

| D ISCUSS I ON
The pathogenesis of VNC is not clear yet. Normally between the fetal 5th and 8th week, intertrabecular spaces are obliterated and ventricular compaction occurs from the base toward the apex and from epicardium to endocardium. VNC is generally thought to be caused by arrest of normal embryogenesis of the endocardium and myocardium (Weiford et al., 2004). Isolated left ventricular noncompaction (iLVNC) was proposed four diagnostic criteria (Jenni, Wyss, & Oechslin, 2002), which have been widely used, while, due to different anatomical characteristics, iRVNC is more difficultly diagnosed in clinics than iLVNC. Electrocardiograph, echocardiogram, computed tomography, and MRI are recommended as the diagnostic models (Weiford et al., 2004).
Major morbidity during long-term follow-up included heart failure, arrhythmias, and thromboembolic events. Heart failure, caused by systolic and diastolic dysfunction, was the most common cause for hospital admission. Cases of noncompaction isolated to the RV without LV involvement have been reported; however, they are often incidentally found and have not been described to cause PE and VT. We describe a case of isolated noncompaction of the RV causing PE and VT.
The electrophysiological mechanism of arrhythmia is still unclear, which may be linked to the irregular connection of the trabeculae and branches of the myocardium, and the instability of myocardial electrophysiology caused by insufficient blood supply to the myocardium. The VT of the patient in this report was successfully eliminated with catheter ablation.
Clinically, PE mostly comes from the lower extremity deep vein system, but if such patients have no evidence of deep venous thrombosis, other sources of emboli should be considered. It is very rare that the embolus comes from the right heart system (in situ thrombosis). The patient reported in this study was diagnosed as PE by SPECT.
Since the patient was never found to have any risk factors for PE in the past and no thrombus was found in ultrasound in both lower limb varices, it was thought the PE was caused by situ embolus of the RV. The deep intertrabecular space may aggravate the risk of thrombus formation and be an additional factor for the situ embolus of the RV. The patients with PE, especially those without significant risk factors or with normal results in lower extremity deep venous system examination, should be considered the possibility of this disease. One follow-up toward 34 adults with VNC recommended anticoagulants should be administered independent of ventricular function to prevent embolic complications (Oechslin, Attenhofer Jost, & Rojas, 2000). The patient in this report was treated with long-term warfarin anticoagulation therapy together with oral ACEI, β-block inhibitors, and spironolactone simultaneously so as to improve the right heart function.

| CON CLUS ION
Isolated ventricular noncompaction is a primary cardiomyopathy that affects the left ventricle and is known to cause arrhythmias and thromboembolic events. Case of on-compaction isolated to the right ventricular without left ventricular involvement has not been described to cause VT and PE. We describe a case of iRVNC causing VT and PE successfully treated with catheter ablation and anticoagulation separately. iRVNC is very rare in clinics, and can lead to PE and VT, so serious attention should be given clinically.

ACK N OWLED G M ENTS
We thank the patient in this study.

CO N FLI C T O F I NTE R E S T
None of the authors have any conflict of interest to disclose.

This study was approved by the First People's Hospital of Yunnan
Province and informed consent was obtained from the patient.