Initial Presentation of an Accessory Left Ventricle in a Patient With Syncope
A 39-year-old woman was referred for a transthoracic echocardiogram after presenting to her primary care provider following an episode of unexplained loss of consciousness. Her past medical history was notable for fibromyalgia and migraine headaches. She had a normal cardiac and neurological physical examination with no extra heart sounds or murmurs.
Her transthoracic echocardiogram (Movie I of the online-only Data Supplement) revealed a large outpouching of the lateral wall of the left ventricle (LV) that contracted in synchrony with the ventricle (Figure 1A and 1B). The initial differential for this finding included an LV diverticulum or an accessory ventricle. An LV pseudoaneurysm was considered unlikely because of the synchronous contraction of the outpouching with the rest of the ventricle.
To further evaluate this abnormality, cardiac magnetic resonance imagine (MRI) was performed (Movie II of the online-only Data Supplement). This study demonstrated a large, irregular, multilobed, contracting outpouching of the mid to distal lateral wall of the LV (Figure 2). The neck measured 1.5×1.8 cm in diameter; the depth measured 2.5 cm. There was normal rest perfusion of the myocardium overlying this outpouching (Figure 3C). On late-enhancement imaging, there was no evidence of scar or infarction surrounding this area, thus eliminating the possibility of a prior infarct or scar leading to a pseudoaneurysm (Figure 3B and 3E). Notably, there were small projections within the wall of the outpouching, and in some of these areas (Figure 3D), the myocardium appeared particularly thin. Within the wall of the outpouching, there were very small areas of myocardial hyperenhancement enhancement most likely consistent with minimal fibrosis (Figure 3E). Cardiac MRI was also helpful in ruling out other cardiac causes of syncope such as infiltrative heart disease, myocardial scar, or other structural abnormalities.
The differential diagnosis for a LV outpouching that contracts synchronously with the rest of the ventricle includes an LV diverticulum or an accessory chamber. A diverticulum contains all 3 layers of cardiac tissue but has a narrow connection to the ventricle. An accessory chamber contains all 3 layers of cardiac tissue but has a wide connection to the ventricle1 and may have an anomalous septum or muscle bundle that divides the ventricular cavity into 2 chambers.2 The imaging features identified in our case, including a large outpouching with a relatively wide neck, multilobed morphology, and a partial accessory septum (Figure 2), all favored the diagnosis of an accessory ventricle.
Literature regarding accessory ventricular chambers in adult populations is sparse, given that the majority of cases have been reported in children and seem to be associated with cardiac systolic dysfunction or other cardiac abnormalities.1–3 However, patients who present with isolated LV outpouchings tend to remain asymptomatic and experience no complications, although ventricular arrhythmias, cardiac rupture, and sudden death have been reported. Thrombus formation within the outpouching causing systemic emboli has also been reported but is exceedingly rare because of the contractile function of the diverticulum or accessory chamber.4
The finding of an accessory ventricular chamber in our patient, coupled with the presentation of unexplained loss of consciousness, led to an electrophysiology study. Although no ventricular arrhythmias could be induced, an implantable cardiac defibrillator was placed owing to the unexplained syncope and the presence of a cardiac structural abnormality known to cause ventricular arrhythmias.
Guest Editor for this article was Leon Axel, MD, PhD.
The online-only Data Supplement is available with this article at http://circ.ahajournals.org/cgi/content/full/121/19/e401/DC1.