Sudden cardiac arrest as the initial presentation for left ventricular noncompaction cardiomyopathy

Abstract

A 37-year-old man without a significant medical history had an out-of-hospital sudden cardiac arrest. A bystander started cardiopulmonary resuscitation, and emergency medical services arrived promptly, confirmed ventricular fibrillation, and restored sinus rhythm. An emergent coronary arteriogram was normal. Transthoracic echocardiography revealed a severely reduced left ventricular ejection fraction and suggested left ventricular noncompaction. The patient’s heart failure with reduced ejection fraction was treated with carvedilol, lisinopril, and spironolactone, and after he was weaned from the ventilator he received an implantable cardioverter-defibrillator. The patient’s identical twin was treated in the same fashion for a sudden cardiac arrest. Although many experts think that left ventricular noncompaction cardiomyopathy is a distinct nosological entity, others think that it is simply a dilated cardiomyopathy with unusually prominent left ventricular trabeculae.

Case report

A 37-year-old man without any significant past medical history presented to the emergency department via emergency medical services following an out-of-hospital cardiac arrest. The patient was with friends and reportedly had two drinks before collapsing. He was unresponsive and without a palpable pulse. A bystander started cardiopulmonary resuscitation; paramedics arrived 7 minutes later and determined that the patient’s cardiac rhythm was ventricular fibrillation. He was treated using a standard American Heart Association advanced cardiac life support protocol for ventricular fibrillation. After 12 minutes of cardiopulmonary resuscitation, a drug protocol, and three defibrillation attempts, the patient returned to sinus rhythm and was intubated and transported to a university-affiliated hospital. Upon arrival in the emergency department, he was noted to be unresponsive, with a Glasgow Coma Scale score of 3. His blood pressure was 135/75 mm Hg; heart rate, 120 beats/min; and respiratory rate, 18 breaths/min via endotracheal tube with bag/valve backup and 100% inspired oxygen. His blood oxygen saturation was 99%. His electrocardiogram showed sinus tachycardia, left ventricular (LV) hypertrophy, and ST-T changes (Figure 1).¹

Figure 1.

Electrocardiogram in a 37-year-old man after resuscitation from ventricular fibrillation shows sinus tachycardia at a rate of approximately 130 beats/min, voltage criteria for left ventricular hypertrophy (R waves in leads V₅ and V₆ and S waves in lead V₃ are each >2.5 mV, and the largest R plus the largest S are therefore >4.5 mV¹). The negative terminal portion of the P waves in lead V₁ are large, suggesting left atrial enlargement with the caveat that P waves generally become larger with faster sinus rates. There are nonspecific ST-T changes.

He emergently went to the cardiac catheterization laboratory, where a coronary arteriogram was normal (Figure 2). The patient remained hemodynamically stable and was transferred to the cardiac critical care unit, where he continued a targeted temperature management protocol. The patient had an identical twin who also had an aborted sudden cardiac arrest and heart failure with a reduced ejection fraction. His twin brother had an implantable cardioverter-defibrillator (ICD) for secondary prevention. The patient’s initial laboratory studies and toxicology screen did not any show any abnormalities. His transthoracic echocardiogram performed within 12 hours of his arrest showed a severely reduced LV ejection fraction and was suggestive of LV noncompaction (LVNC) (Figure 3). Cardiac magnetic resonance imaging (MRI) performed the following day confirmed the diagnosis of isolated LVNC. The patient was started on carvedilol 3.125 mg twice daily, lisinopril 5 mg daily, and spironolactone 25 mg daily to treat his heart failure with reduced ejection fraction. After he was weaned from the ventilator, he underwent ICD placement for secondary prevention of sudden cardiac death and was discharged home on day 8 of hospitalization.

Figure 2.

Coronary arteriograms. (a) Left anterior oblique view showing a nondominant right coronary artery and its branches. (b) Right anterior oblique view showing the left main, left anterior descending, and left circumflex coronary arteries. All arteries are arteriographically normal.

Figure 3.

Echocardiographic images of the left ventricle: (a) parasternal short axis view and (b) apical four-chamber view. Both views show unusually prominent trabeculae.

Discussion

Left ventricular noncompaction cardiomyopathy (LVNCC) is an uncommon primary genetic cardiomyopathy that often presents as heart failure. Typically the LV is dilated and hypocontractile with a thin compacted outer muscular layer and a thicker, heavily trabeculated inner layer with deep intratrabecular recesses that are continuous with the LV cavity. (Unlike the normal right ventricle, the normal LV is not heavily trabeculated.) The condition is thought to arise from intrauterine arrest of compaction of fetal myocardium. Malignant arrhythmias or sudden cardiac arrest is a rare presentation and constitutes about 2% to 5% of cases.²

Although LVNC had been described in patients with other congenital cardiac malformations and in a variety of muscular dystrophies, isolated LVNCC was initially described in eight patients by Chin et al in 1990.³ LVNC with or without LV dysfunction has been found in 0.14% to 0.26% of patients referred for echocardiography.^4,5 Both sporadic and familial mutations have been described for LVNC. Familial mutations are most often autosomal dominant, and in rare cases inheritance has been X linked.⁶ Several familial mutations have been reported in genes responsible for sarcomeric and mitochondrial proteins. Beta myosin heavy chain (MYH7), alpha-cardiac actin (ACTC), cardiac troponin T (TNNT2), troponin I (TNN13), SCN5A, and G4.5 are some of the familial mutations that have been described.^6,7 Murphy et al screened asymptomatic first-degree family members with echocardiography and found 25% of the screened population to have echocardiographic abnormalities, which included LVNC, enlarged LV diameter, and noncompaction of posterior wall that did not meet criteria for LVNC.⁸

Most commonly, patients with LVNC present with symptoms of heart failure followed by an abnormal cardiac exam.^2,6 An incidental finding on an echocardiogram performed for any reason is the presentation in about 10% of cases. Malignant arrhythmias leading to syncope or sudden cardiac death are rare but have been reported.² The prevalence of thromboembolic events is increased in patients with LVNC and was found to be 24% by Oechslin et al.⁹ Thromboembolic risk could be multifactorial: an increased incidence of atrial fibrillation, a decreased LV ejection fraction, and hypertrabeculation of the LV myocardium.

The diagnosis of LVNC is both clinical and echocardiographic. If echocardiographic features are inconclusive, then cardiac MRI can be done to establish a diagnosis. When Chin et al first described LVNC in 1990,³ they compared the morphological features on echocardiogram with those of normal subjects. They described an X-to-Y ratio of ≤0.5 where X is the distance from the epicardial surface to the trough of trabecular recess and Y is the distance from the epicardial surface to the peak of trabeculation.³ Jenni et al described the echocardiographic appearance of the compacted epicardial layer and a thicker endocardial layer with prominent trabeculations with color Doppler evidence of flow within these trabeculations.¹⁰ According to their criteria, a maximal end systolic ratio of noncompacted to compacted layers of >2 is diagnostic of LVNC.¹⁰ They also noted that noncompaction was predominantly localized to mid-lateral, apical, and mid-inferior areas of the LV. The Jenni criteria were later validated in a retrospective analysis of medical records and blind review of echocardiograms.¹¹

Cardiac MRI offers more spatial resolution in imaging the LV. Noncompacted appearance may be more common on an MRI due to this increased resolution and may also be seen in other types of cardiomyopathy such as dilated cardiomyopathy. In 2005, Petersen et al¹² studied the cardiac MRI cine images of seven patients previously diagnosed with LVNC, where the diagnosis was supported by additional features, and compared them to MRI images of healthy volunteers, athletes, and patients with hypertrophic cardiomyopathy, dilated cardiomyopathy, hypertensive heart disease, and aortic stenosis. They found that a noncompacted-to-compacted ratio of >2.3 in diastole is a cutoff for pathological noncompaction, with a sensitivity of 86% and specificity of 99%.¹² When compared to echocardiogram, cardiac MRI allows for better visualization of the LV apex and has better sensitivity and specificity.

LVNC is managed like cardiomyopathy from other etiologies. Guideline-directed medical therapy for systolic heart failure is indicated for all patients after initial evaluation with echocardiography.⁶ Genetic testing has a yield of around 50% and should be recommended to patients at the time of diagnosis.⁷ It is appropriate to screen asymptomatic first-degree family members with clinical examination and echocardiography. Anticoagulation in patients with LVNC and atrial fibrillation should be guided by the CHADS2-Vasc scoring system. In patients without atrial fibrillation, anticoagulation is indicated for those with prior thromboembolic events or LV thrombus. Per American College of Cardiology/American Heart Association guidelines, primary prevention with an ICD is indicated in patients for heart failure with reduced ejection fraction.⁹ Advanced heart failure therapies with mechanical circulatory support and cardiac transplantation may be required in patients with severely decreased end-stage cardiac function.

The status of LVNCC as a distinct nosological entity is not universally accepted. LVNCC and dilated cardiomyopathy have many similarities.^13,14 Roberts and colleagues opined that isolated LVNC is morphologically overdiagnosed.¹⁴ Fortunately, the management is similar for LVNCC and dilated cardiomyopathy.