17-year-old boy with syncope and cardiac arrest

CASE PRESENTATION

A previously healthy 17-year-old male presented to the emergency department following a syncopal episode while playing basketball. His medical history was unremarkable, except for having sickle cell trait. There was no known family history of sudden death or cardiac disease. His electrocardiogram showed sinus rhythm, and his physical exam and troponin were normal. Echocardiogram revealed a dilated left ventricle (LV) with increased trabeculations (Figure 1) and decreased LV ejection fraction of 28%. An out-patient cardiac magnetic resonance imaging (MRI) was arranged, and the patient was counselled on interim activity restrictions. Sixteen days later, he experienced an out-of-hospital cardiac arrest while playing basketball. He was intubated on scene and had an initial shockable rhythm of ventricular tachycardia. After 53 minutes of cardiopulmonary resuscitation per advanced cardiac life support (ACLS) guidelines, including a drug protocol and multiple defibrillations, spontaneous return of circulation was achieved in the emergency department. His urine toxicology was negative. An electrocardiogram revealed a wide complex arrythmia and ST depression, without ST elevation. The patient was subsequently transferred to the intensive care unit, where he experienced another cardiac arrest. Spontaneous return of circulation was achieved after 10 minutes of ACLS. Further family history and an investigation established the underlying diagnosis.

Figure 1.

Two-dimension echocardiogram of a 17-year-old boy with left ventricular non-compaction cardiomyopathy. Parasternal short axis view of the left ventricle demonstrates two-layered myocardium with thin compacted epicardial band (C) and thicker noncompacted endocardial layer (NC) with deep recesses. LV, left ventricle. RV, right ventricle.

CASE DIAGNOSIS: LEFT VENTRICULAR NONCOMPACTION CARDIOMYOPATHY

Cardiac MRI confirmed trabeculations or bundles of muscle that extend into the LV chamber with a ratio of noncompacted-to-compacted myocardium of >2.3. His estranged father revealed that he received an implantable cardioverter-defibrillator (ICD) after a stroke secondary to left ventricular noncompaction cardiomyopathy at age 40. Furthermore, he shared that the patient’s paternal grandfather and paternal great-grandfather both died at around age 40 from cardiac disease. The patient received a single lead subcutaneous ICD and had no significant cognitive deficits at discharge. His two healthy siblings sired by the same father underwent transthoracic echocardiography, and both were found to have structurally normal hearts.

Left ventricular noncompaction cardiomyopathy (LVNC) is a relatively rare congenital condition with a heterogeneous age of presentation and clinical severity. This condition is postulated to arise from an arrest of normal myocardial compaction during intrauterine development. The resulting morphology is a LV with a thick inner layer with prominent trabeculations and deep intertrabecular recesses, and an outer myocardial layer that is thin and compacted (1). The inheritance pattern for LVNC is most commonly autosomal dominant. Sporadic mutations, X-linked inheritance, and autosomal recessive inheritance have been documented but are less common (1).

Cardiac symptoms in LVNC can vary from asymptomatic to overt heart failure or sudden cardiac death. However, the majority of patients with LVNC are asymptomatic from a cardiovascular perspective (1). The most common initial presentations of paediatric LVNC are symptomatic congestive heart failure or an abnormal cardiac exam, such as a murmur, abnormal heart sounds or arrhythmia (1). Other manifestations of symptomatic LVNC are chest pain, dyspnea, palpitations, peripheral edema, and exercise intolerance. Syncope can also result from the heart’s inability to sustain cerebral perfusion, which can be exacerbated by increased oxygen demand states such as exercise. Moreover, due to the arrhythmogenic nature of noncompacted myocardium, hypertrabeculation of the LV, and decreased LV ejection fraction, patients with LVNC have an increased risk of thromboembolic events (1). In the paediatric population, arrythmias leading to syncope or sudden cardiac death are rare, comprising only 2-5% of LVNC presentations (1). It is notable that children presenting within the first year of life have relatively higher mortality, which can be attributed to a greater likelihood of presenting with symptomatic heart failure or arrhythmias (1). Conversely, low mortality is associated with patients with normal cardiac dimensions and function (1).

The diagnosis of LVNC can be challenging given its heterogenous clinical features and variable age of presentation. The differential diagnoses include other cardiomyopathies, such as dilated, restrictive, and particularly hypertrophic. However, both cardiac MRI and echocardiography are reliable and commonly used imaging modalities for diagnosing LVNC if certain red flags are present on history of physical exam (Table 1). According to the validated Jenni criteria, a diagnosis of LVNC can be made if the ratio of noncompacted-to-compacted myocardium is >2 at end-systole on echocardiography (2). Alternatively, on cardiac MRI, a ratio of noncompacted-to-compacted myocardium >2.3 is reported to have 86% sensitivity and 99% specificity (2). Thus, cardiac MRI offers high sensitivity and specificity and can be used to establish a diagnosis of LVNC and/or corroborate echocardiographic findings.

Table 1.

“Red flags” on history and physical exam for cardiogenic syncope and LVNC

	Cardiogenic syncope	LVNC
History	Exertional syncope No associated precipitating factor or prodrome (e.g., nausea, sweating, pallor, visual changes, light-headedness) No other cause (hypovolemia, hypoglycemia, seizure, intoxication) Family history of sudden cardiac death	Older children   Exertional syncope Palpitations Progressive edema Shortness of breath Reduced exercise tolerance Orthopnea Paroxysmal nocturnal dyspnea Newborns Excessive sweating with feeds or activity Difficulty feeding Failure to thrive All Family history of sudden cardiac death or congenital heart disease
Physical Exam	Normal orthostatic vital signs Normal volume status Arrythmia Systolic murmur	Central cyanosis Mid-systolic murmur Extra heart sounds (e.g. S3, S4) Crackles Pitting edema

LVNC Left ventricular non-compaction cardiomyopathy

Management of LVNC is dependent on clinical manifestations of the disease and can include guideline-directed therapy for heart failure and anticoagulation. Moreover, antiarrhythmics are appropriate for patients with arrythmia, and ICD placement is indicated for patients with heart failure and reduced ejection fraction. In addition, genetic testing of the patient and screening of first-degree family members with echocardiography and physical examination is recommended. Given the strong association of sudden cardiac death with cardiac dysfunction and arrhythmias, lifelong cardiac evaluation with annual echocardiograms and holter monitoring is warranted for patients with LVNC. Lastly, infants with ventricular tachycardia and depressed ventricular function have high mortality and warrant consideration for mechanical device or transplantation (1).

We describe the case of a previously healthy adolescent with syncope and sudden cardiac arrest as an unusual initial presentation of LVNC. Despite an apparently benign family history and lack of preceding symptoms, one should consider LVNC as a differential diagnosis of syncope to prevent mortality and ensure appropriate treatment and cardiac follow-up for patients and their relatives.

CLINICAL PEARLS

1. Left ventricular noncompaction cardiomyopathy is a rare, congenital cardiomyopathy that is associated with significant trabeculations in the left ventricle. A minority of patients are symptomatic, and the most common initial presentation is congestive heart failure.

2. Diagnosing left ventricular noncompaction cardiomyopathy can be challenging given the varied age of presentation and clinical severity. Some red flags warranting further work-up include mid-exertional syncope, decreased exercise tolerance, palpitations, and a family history of sudden cardiac death or congenital heart disease. Cardiac imaging with echocardiography and MRI are reliable diagnostic tools.

3. A common and benign cause of syncope is vasovagal syncope, which is associated with a prodrome of nausea, visual disturbances, sweating, and light-headedness. In contrast, cardiogenic syncope secondary to left ventricular noncompaction cardiomyopathy requires cardiac imaging and is associated with exertional syncope, murmur, and malignant arrythmias.

Informed Consent: Family consent for publication of this case has been obtained in writing.

Funding: There are no funders to report.

Potential Conflicts of Interest: All authors: No reported conflicts of interest. All authors have submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest. Conflicts that the editors consider relevant to the content of the manuscript have been disclosed.