Hypereosinophilic syndrome presenting as recurrent presyncope and acute myocarditis (QF_SA_121)

A 63-year-old lady presented with recurrent presyncope and exertional dyspnea. Workups showed elevated troponin, non-obstructive coronary artery disease and incidental finding of elevated absolute eosinophil count (AEC). Three months after, she had new-onset chest pain, worsening dyspnea and transient left upper extremity weakness. Tests were consistent with myocarditis. In the background of persistent eosinophilia (maximum AEC 40.7x10⁹/L), she was diagnosed with hypereosinophilic syndrome (HES) with eosinophilic myocarditis (EM). Patient responded to steroid therapy.

Diagnostic Techniques and Their Most Important Findings:

Electrocardiogram showed isorhythmic dissociation and new-onset right bundle branch block (Fig. 1). Decreased ejection fraction (40%) with regional wall motion abnormalities were noted on echocardiogram. On cardiac MRI, there was subendocardial hypo-enhancement on early gadolinium imaging and patchy mid-wall and subendocardial late gadolinium enhancement (LGE) in multiple territories (Fig. 2 and 3). No thrombus was noted. Cranial MRI revealed subacute infarcts. Endomyocardial biopsy was inconclusive. Bone marrow biopsy and whole body CT scan did not show any malignancy. The patient was placed on prednisolone 1 mg/kg daily and 3-day methylprednisolone (1 gram) pulse therapy with symptomatic improvement, resolution of arrhythmia, and down-trending AEC and cardiac markers.

Learning Points from this Case:

HES is a heterogeneous disorder characterized with persistent eosinophilia resulting in tissue infiltration and damage. Neurologic involvement is rare (4%) and could explain the initial presentation of recurrent presyncope secondary to autonomic dysfunction¹. EM is likewise uncommon (5%) but is considered the most life-threatening with its complications of cardioembolic phenomenon, heart failure and arrhythmia². Cardiac MRI plays a major role in the diagnosis as it demonstrates eosinophil-mediated cardiac injury³. In this case, there was elevated T1 (1066 msec), extracellular volume (33.7%), LGE and pericardial effusion consistent with acute myocarditis⁴. It is interesting to note that the patchy mid-wall LGE in this case is less common compared to the typical diffuse or patchy subendocardial distribution in EM². In addition, early gadolinium imaging findings were indicative of microvascular obstruction (MVO), seen as circumferential subendocardial hypo-intensity⁵. The frequency of MVO in eosinophilic myocarditis has not yet been reported. The presence of MVO on CMR after acute coronary syndrome  is an independent predictor of cardiovascular events and mortality, but its role in prognosticating patients with non-ischemic cardiomyopathy is still unknown⁶. Close follow-up for disease progression is recommended.