Left-ventricular Non-compaction Cardiomyopathy Presenting With Atrial Flutter With Rapid Ventricular Response

Abstract

Left ventricular non-compaction cardiomyopathy (LVNC) is a rare genetic cardiomyopathy characterized by prominent trabeculations and deep recesses that predispose to arrhythmias and heart failure. We describe a 42-year-old man with persistent tachycardia and exertional fatigue found to have CTI-dependent atrial flutter with 2:1 conduction. Transesophageal echocardiography showed severe biventricular dysfunction with an ejection fraction of 15%, and cardiac MRI confirmed LVNC with a non-compacted to compacted ratio of 3.3. After successful ablation and normal coronary angiography, he was diagnosed with LVNC. This case highlights an unusual presentation of LVNC with typical atrial flutter and underscores the value of cardiac MRI in diagnosing unexplained atrial arrhythmias.

1. Introduction

A 42-year-old male with no known past medical history presented to our Emergency Department for evaluation of persistent tachycardia, intermittently detected by his smartwatch over several years, with heart rates of 140–150 bpm. Recently, alerts increased in frequency and were accompanied by exertional fatigue and reduced exercise tolerance. Our patient endorsed regular daily use of both marijuana and tobacco, with a family history significant for an unknown arrhythmia in his father for which he had undergone a catheter ablation. On admission, the patient was hemodynamically stable. 12-lead electrocardiogram revealed a typical cavotricuspid isthmus (CTI)-dependent atrial flutter with a 2:1 atrioventricular conduction and a ventricular rate of 143 bpm. Initial management included initiation of a rate control agent with metoprolol tartrate.

2. Investigations

A transesophageal echocardiogram (TEE) performed during admission prior to catheter ablation revealed a severely reduced left ventricular systolic function (EF 15%) with global hypokinesis, biventricular chamber enlargement, and impaired right ventricular function. The left atrium was dilated, with moderate functional mitral and tricuspid regurgitation (Fig. 1). No thrombus was visualized in the left atrial appendage, allowing the patient to proceed with catheter ablation.

Fig. 1.

(1) Transthoracic echocardiogram, parasternal long-axis view demonstrating biventricular dilation with enlargement of the left ventricle (red arrow), right ventricle (blue arrow), and right atrium (green arrow), along with left atrial enlargement. (2) Transesophageal echocardiogram, midesophageal four-chamber view confirming biventricular dilation and biatrial enlargement. (3) Transesophageal echocardiogram with color Doppler demonstrating functional mitral regurgitation. (4) Transesophageal echocardiogram with color Doppler demonstrating functional tricuspid regurgitation.

Our patient subsequently underwent an electrophysiology study and catheter ablation. Findings revealed normal sinus node function, with no evidence of dual atrioventricular node (AVN) physiology or accessory pathways. A linear ablation line was created along the cavotricuspid isthmus, extending from the tricuspid annulus to the inferior vena cava (TA/IVC line). This resulted in restoration of normal sinus rhythm in our patient.

With findings of dilated cardiomyopathy, the patient was evaluated for potential ischemic etiology underlying the cardiomyopathy. A coronary angiography was performed, which demonstrated normal coronary artery anatomy without obstructive disease (Fig. 2). Given the unexplained cardiomyopathy in a young adult male, cardiac magnetic resonance (CMR) imaging was ordered. CMR illustrated prominent myocardial trabeculations with a non-compacted to compacted myocardial ratio of 3.3 at the inferior apical wall in end-diastole, fulfilling Petersen criteria for LVNC (Fig. 3).1

Fig. 2.

Left heart catheterization demonstrating no obstructive coronary artery disease. Angiographic views: (1) Left anterior oblique (LAO) caudal; (2) Right anterior oblique (RAO) caudal; (3) Cranial left anterior descending (LAD); (4) Right coronary artery (RCA), LAO cranial view.

Fig. 3.

Cardiac magnetic resonance imaging. Steady-state free precession (SSFP) cine images at end-diastole. (1) Four-chamber view demonstrating prominent trabeculations in the distal left ventricle consistent with non-compacted myocardium (red arrow). (2) Short-axis view demonstrating a two-layered myocardium with non-compacted and compacted layers and a non-compacted to compacted myocardial ratio of 3.3 at the inferior apical wall.

3. Management

We initiated guideline-directed medical therapy (GDMT) for heart failure with reduced ejection fraction (HFrEF), which included an ACE inhibitor and beta-blocker. Additionally, the patient was started on an anticoagulation agent of apixaban given the recent atrial flutter and cardioversion.

4. Outcome

He was discharged in stable condition with a wearable cardioverter-defibrillator (WCD) and scheduled for outpatient follow-up. At 3-month follow-up, echocardiography showed normalization of biventricular size and function, with LVEF improving to 50% and resolution of mitral and tricuspid regurgitation. The patient remained in normal sinus rhythm with strict adherence to GDMT. Genetic testing was discussed, but the patient has elected to defer testing at this time.

5. Discussion

LVNC is a rare disorder characterized by prominent trabeculations and deep intertrabecular recesses within the left ventricular myocardium.2 Non-compaction cardiomyopathy develops as a result of a failure of myocardial fibers to compact during embryonic development.1,3 Since its first description in 1926 and initial echocardiographic report in 1984, the etiology of LVNC remains debated.1 Genetic studies have shed light on its pathogenesis, with mutations most commonly identified in sarcomere and nuclear envelope genes such as MYH7, ACTC1, TNNT2, MYBPC3, TPM1, and TNNI3.2 These findings support the theory of disrupted myocardial compaction during embryogenesis, particularly from the base to the apex of the heart.2 Clinically, LVNC may be asymptomatic or present with signs of arrhythmias, heart failure, systemic thromboembolism, and sudden cardiac death. The diagnosis of LVNC is based on established imaging criteria, most commonly those proposed by Jenni et al. for echocardiography (non-compacted to compacted ratio >2:1 in end-systole) and Petersen et al. for CMR (>2.3:1 in end-diastole).3–5

Management of LVNC is tailored to the individual patient’s clinical presentation. For those with heart failure, treatment aligns with guideline-directed medical therapy (GDMT), including ACE inhibitors or ARNi, beta-blockers, mineralocorticoid receptor antagonists, and SGLT2 inhibitors.6 The decision to initiate anticoagulation remains individualized, especially in patients with atrial fibrillation or an ejection fraction of less than 40%, due to a lack of definitive guidelines but known risk of thrombus formation. Patients with sustained ventricular arrhythmias or a history of sudden cardiac arrest typically require an implantable cardioverter-defibrillator (ICD) implantation for secondary prevention.6 Genetic counseling and testing are integral parts of management. The 2018 Heart Failure Society of America (HFSA) guidelines recommend a detailed three-generation family history genetic testing in the most phenotypically affected individuals, and subsequent cascade screening of first-degree relatives when a pathogenic variant is identified.7,8 Our patient reported a family history of an unspecified arrhythmia in his father, managed with catheter ablation, raising the possibility of an underlying heritable mutation. Despite this, the patient elected to defer genetic testing at this time. Approximately 15–20% of LVNC cases are familial, while those without an identifiable genetic mutation or family history are considered sporadic.7,8 Early identification and personalized treatment are essential to optimizing outcomes in patients with LVNC.

Despite LVNC being rare, this case highlights the importance of including it in the differential diagnosis, as it may mimic other cardiomyopathies and result in diagnostic delays. In our case, echocardiography did not identify the characteristic trabeculations, and CMR, initially obtained to assess scar burden, revealed findings consistent with LVNC. Transthoracic echocardiography may miss apical trabeculations, whereas CMR provides superior delineation of myocardial architecture when suspicion remains high. Supraventricular arrhythmias (SVAs) are less frequently reported as an initial manifestation.4 In this patient, the initial manifestation of typical CTI-dependent atrial flutter with a rapid ventricular response is noteworthy. While arrhythmias are common in LVNC, atrial flutter is rarely the initial rhythm. According to a study by Tumolo and Nguyen,4 atrial flutter was reported in only 2 out of 557 cases of isolated LVNC, indicating that it is a rare arrhythmia in this population. Although supraventricular arrhythmias are common in LVNC, presentation with typical CTI-dependent atrial flutter, severe yet reversible biventricular dysfunction, and echocardiographically occult trabeculation is uncommon, highlighting how structural disease and tachycardia can interact to drive cardiomyopathy.

The pathophysiology underlying atrial arrhythmias in LVNC is not fully understood but may be due to left atrial remodeling secondary to elevated filling pressures or diffuse myocardial fibrosis involving both ventricles and atria.2 In our patient, TEE revealed severely reduced left ventricular ejection fraction (15%), biventricular enlargement, impaired right ventricular function, and elevated right ventricular systolic pressure (RVSP), consistent with advanced cardiomyopathy. A dilated left atrium and moderate secondary mitral and tricuspid regurgitation provided an ideal structural substrate for macro-reentrant atrial arrhythmias. These findings reflect atrial stretch and remodeling, creating a substrate for reentrant arrhythmias. In this context, trabecular abnormalities may facilitate reentry and sustain atrial arrhythmias. Non-compacted myocardium exhibits abnormal conduction due to fibrosis and disarray and may involve atrial tissue, promoting arrhythmogenesis. 2 The marked improvement in ventricular function at 3-month follow-up likely reflects a substantial tachycardia-mediated component. The rapid normalization of biventricular size and improvement in ejection fraction from 15% to 50% is more characteristic of tachycardia-mediated cardiomyopathy than primary LVNC alone, suggesting that sustained atrial flutter with rapid ventricular response was the principal driver of myocardial dysfunction.

Discussion continues regarding optimal CMR criteria for diagnosing LVNC. In the Multi-Ethnic Study of Atherosclerosis (MESA), Kawel et al. found that the Petersen criterion may be met more often in the general population than previously recognized, suggesting that a higher threshold could improve specificity.9 Grothoff et al. proposed a >3:1 ratio, which demonstrated 100% sensitivity and greater specificity compared with the Petersen criteria.10 The non-compacted to compacted ratio of 3.3 exceeds both the Petersen threshold and the more specific Grothoff criterion, which offers improved specificity for LVNC. In this clinical context, LVNC is favored as the most likely unifying diagnosis, although hypertrabeculation with superimposed tachycardia-mediated dysfunction cannot be excluded. Late gadolinium enhancement findings were not reported, limiting assessment of myocardial fibrosis and risk stratification. Follow-up CMR was not performed; reassessment after reverse remodeling may help distinguish persistent LVNC from loading-related hypertrabeculation.

6. Conclusion

LVNC may present with typical atrial flutter and severe yet reversible ventricular dysfunction. This case highlights key points: LVNC should remain in the differential for unexplained cardiomyopathy, especially when echocardiography is nondiagnostic; CMR is critical for identifying apical trabeculations and confirming the diagnosis; supraventricular arrhythmias, though rarely the initial presentation, may unmask underlying structural disease; and recognition of superimposed tachycardia-mediated cardiomyopathy is essential, as timely rhythm control can lead to marked recovery. Together, these findings emphasize the importance of integrating advanced imaging with clinical context to avoid diagnostic delay and guide management.