Double-Chambered Left Ventricle

Abstract

Background

Double-chambered left ventricle (DCLV) is a rare congenital heart anomaly and can be easily misdiagnosed with transthoracic echocardiography. Cardiac magnetic resonance (CMR) can help in the diagnostic process and risk stratification.

Case Summary

A 15-year-old girl diagnosed with left ventricular noncompaction and unsustained ventricular tachycardia was referred to our institution for further characterization. The CMR scan demonstrated instead a DCLV with normal ejection fraction and tissue characterization parameters within normal limits. The patient was started on bisoprolol, which was effective in reducing the arrhythmic burden, and she is currently under regular follow-up.

Discussion

DCLV has been described only in anecdotal case reports since the first classification was published in 1981. In our case, a prominent paraseptal trabecula was the anatomical fingerprint, but it could not be properly identified with transthoracic echocardiography. CMR instead was pivotal in the diagnosis, which allowed us to properly identify the morphology of the left ventricle and provided tissue characterization, therefore refining arrhythmic risk stratification. In addition, it excluded other differential diagnosis such as ventricular septal defects.

Take-Home Message

This case highlights the importance of CMR in the diagnosis of rare congenital cardiac abnormalities, such as DCLV, especially when the echocardiographic window is suboptimal or unclear.

Graphical Abstract

History of Presentation

A 15-year-old girl was referred to the local pediatric cardiac service due to the onset of palpitation.

Electrocardiography (ECG) was performed, which highlighted repolarization abnormalities and frequent ventricular and supraventricular ectopic beats (Figure 1). The patient was then monitored with a 24-hour ECG Holter, which detected an episode of unsustained ventricular tachycardia. The diagnostic work-up was completed with a transthoracic echocardiogram (TTE) that showed normal biventricular size and function, with increased trabeculation in the distal inferior septum (Figure 2).

Figure 1.

Electrocardiogram Showing Sinus Rhythm, With Repolarization Abnormalities and Frequent Ventricular and Supraventricular Ectopic Beats

Figure 2.

Transthoracic Echocardiogram

Apical 4-chamber view showing the normal size of all the cardiac chambers. The arrow indicates the increased left ventricular trabeculation.

The patient was treated with bisoprolol and referred to our institution for cardiac magnetic resonance (CMR).

Past Medical History

The patient's past medical history was unremarkable, and she had no family history of cardiomyopathy, juvenile sudden cardiac death, and congenital heart disease.

Differential Diagnosis

Our initial diagnostic hypothesis, based on the symptoms, TTE findings, and ECG abnormalities with an increased arrhythmic burden obtained during 24-hour ECG Holter monitoring, was similar to that of left ventricular noncompaction cardiomyopathy (LVNC) (Figure 2, arrow).

In the differential diagnosis with respect to cardiomyopathy, a large muscular ventricular septal defect could have also been considered, based on the aspect of the ventricular septum in the proximity of the prominent paraseptal trabecula (Figures 2 and 3). However, large and uncommitted ventricular septal defects are usually diagnosed in fetal life or soon after birth, while at a later age, patients develop Eisenmenger syndrome.

Figure 3.

Cardiac Magnetic Resonance

(A to C) Cine b-SSFP in end-diastole showing the left ventricle morphology. (A) 4-chamber view, (B) modified 4-chamber view, and (C) short-axis view. (D to F) Corresponding late gadolinium enhancement sequences showing no hyperenhancement. The arrows indicate the paraseptal trabecula.

Finally, another diagnostic hypothesis could have been the presence of a left ventricular diverticulum. However, this condition rarely locates mid-ventriculum or occurs as an isolated finding and is usually associated with symptomatic congenital heart diseases from the early years of life.

Investigations

CMR was performed on a 1.5-T MRI scanner (Achieva, Philips Healthcare). The CMR protocol included a real-time localizer, cine b-SSFP sequences, 2D phase contrast, T₂ turbo spin echo fat saturation, T₁ mapping (Shortened Modified Look-Locker Inversion recovery), T₂ mapping (T₂-prep bSSFP), first pass perfusion, and late gadolinium enhancement (LGE) after intravenous gadobutrol administration (10 mmol). The scan showed a left ventricle (LV) of normal size and function (end-diastolic volume index: 80 mL/m², LV ejection fraction: 63%, and LV mass: 51 g/m²). No finding was in keeping with LV hypertrabeculation based on morphological planimetric criteria,¹ but an abnormal trabecula was identified within the LV, extending from the midventricular portion of the left interventricular septal border to the apex, where it terminated 2 cm away from the true septum (Figures 3A to 3C). A thinned myocardium and some crypts were noted in the basal inferior wall, but no regional wall motion abnormalities were observed. 2D phase contrast mapping at the level of proximal ascending aorta and pulmonary artery showed a normal Q_p:Q_s ratio of 0.95:1. T₁ and T₂ mapping at the level of the interventricular septum ranged within normal values according to the published literature (T₁ = 1029 milliseconds and T₂ = 53 milliseconds).2, 3, 4 There was no hyperintensity in the T₂-weighted sequences. First pass perfusion demonstrated homogeneous uptake and washout of gadolinium, and the LGE was negative (Figures 3D to 3F).

Outcome and Follow-Up

After the diagnosis, the patient was kept on bisoprolol. She is currently asymptomatic, under regular clinical review, including TTE and ECG Holter monitoring.

Discussion

In this case report, we present a case of double-chambered left ventricle (DCLV), highlighting the diagnostic role of CMR.

Double-chambered heart diseases are characterized by an abnormal partition of either the right ventricle (RV) or the LV. Although similarly named, double-chambered right ventricle (DCRV) and DCLV differ in epidemiology, in their anatomical etiology, and ultimately in hemodynamic implications.

In DCRV, the RV is divided into a high-pressure chamber (proximal) and a distal low-pressure chamber, either by anomalous muscle bands, hypertrophy of the trabecular tissue, or an aberrant moderator band,^5,6 and it is postulated that a failure in the absorption of the muscular ridge of the crista supraventricularis causes a permanent and abnormal partition between the RV and the infundibulum, which eventually becomes functionally an accessory ventricle.⁵ Patients with DCRV usually present with significant cyanosis⁷ and heart failure during the neonatal period or in early infancy.⁸

DCLV is a much rarer condition, having been described only in anecdotal case reports.⁹ Although its incidence is not known, Meier et al¹⁰ collected 3 cases of DCLV from 7,000 CMR scans, and in our experience, this was the first case diagnosed since the pediatric CMR service was established at our institution (>2,000 CMR scans).

The first classification of DCLV was published in 1981, when Gerlis et al¹¹ grouped the former case reports into 4 groups, which encompassed LV wall diverticulum or bulging in different portions of the LV. However, LV diverticula are different from DCLV because they are often associated with endocardial fibroelastosis and they are presumably caused by anomalies during the development of the myocardial intratrabecular sinusoids.¹² In our case, the CMR scan identified some crypts in the basal inferior wall, but it did not show LV protrusion, bulging nor findings in keeping with fibroelastosis.

Interestingly, in our patient, the LV was divided into 2 chambers by abnormal muscular tissue, making it similar to case #3 published by Gerlis et al,¹¹ described as a congenital tubular muscular diverticulum extending from the apex of the LV. DCLV is often asymptomatic, being diagnosed incidentally as part of other diagnostic work-up. In our case, the patient was referred to further investigation in view of the possible LVNC diagnosis using TTE, supported by frequent supraventricular and ventricular ectopic beats as well as repolarization abnormalities on ECG. However, in our case, CMR ruled out LVNC, based on morphological findings. In addition, a negative LGE, together with normal T₁ and T₂ mapping, made cardiomyopathy unlikely and supported a benign form of DCLV.

Other authors have demonstrated that differential diagnosis, such as tetralogy of Fallot or LV diverticulum, can potentially mimic DCLV,¹⁰ and Kato et al¹³ reported 1 case of DCLV in a patient admitted with out-of-hospital ventricular fibrillation.

Despite being a rare finding, case reports of DCLV are now diagnosed more frequently since the implementation of CMR, performed to support a different initial diagnosis.^9,10,14 In our case, CMR was pivotal because the transthoracic acoustic window was suboptimal and the abnormal muscular tissue dividing the LV was initially diagnosed as LVNC. Compared with transthoracic echocardiography, CMR cine b-SSFP sequences have a better spatial resolution and a high contrast-to-noise ratio, which allowed us to examine properly the morphology of the LV in 4-chamber, ad hoc modified 4-chamber, and short-axis views, overcoming the limit of a suboptimal transthoracic acoustic window. In addition, 2D phase contrast MRI excluded cardiac shunts, and negative first pass perfusion ruled out perfusion defects. Although we did not have direct anatomopathological characterization, a negative LGE together with normal T₁ values was in keeping with normal myocardium with no fibrosis or scar. T₂ mapping and T₂ turbo spin echo fat saturation completed the scan and excluded myocardial edema. However, the regional (rather than global) mapping and the use of published reference values instead of institution-specific normal ranges may represent some limitations.^15,16

Conclusions

DCLV is a rare congenital cardiac anomaly. Initially diagnosed as part of LV diverticular spectrum, DCLV is now defined as the division of the left ventricular chamber into 2 chambers by abnormal muscular tissue. Although most patients are asymptomatic and DCLV is an incidental diagnosis, premature ventricular and supraventricular complexes and ventricular arrhythmias may occur, thus suggesting regular cardiac follow-up in patients with DCLV. CMR is crucial in defining the anatomical characteristics of DCLV and in the follow-up of these patients because it provides a better spatial resolution and allows tissue characterization, identifying the anatomical substrate for arrhythmias.

Visual Summary.

Diagnostic Pathway in DCLV Diagnosis

Funding Support and Author Disclosures

The authors have reported that they have no relationships relevant to the contents of this paper to disclose.

Take-Home Messages

• •This case highlights the importance of CMR in the morpho-functional and tissue characterization of the left ventricular cavity.
• •CMR becomes pivotal in the diagnosis and follow-up of double-chambered left ventricle, especially when the transthoracic acoustic window is suboptimal or unclear.