Prognostic Significance of Myocardial Ischemia Detected by Single-Photon Emission Computed Tomography in Children with Hypertrophic Cardiomyopathy

Abstract

Myocardial ischemia caused by microvascular dysfunction is an important pathophysiologic component of hypertrophic cardiomyopathy (HCM), promoting myocardial fibrosis, adverse left ventricular remodeling, and impacting on clinical course and outcome in HCM patients. The aim of study was to assess the prevalence and clinical significance of myocardial ischemia in children with HCM using 99mTc-MIBI single-photon emission computed tomography (SPECT). Ninety-one children with HCM, median age 13.6 years, underwent SPECT evaluation from 2006 to 2017. Imaging was performed at rest and after maximal exercise. Myocardial perfusion defects were identified in 70 children (76.9%; group I), median age 13.8 years. Fixed perfusion defects were evident in 22 of them, while reversible at rest in 48. In 21 children (23.1%; group II), median age 11 years, myocardial perfusion defects were not detected. Patient demographics, echocardiography, resting electrocardiogram (ECG), 24-h Holter ECG, myocardial fibrosis in cardiovascular magnetic resonance imaging, and cardiovascular events were analyzed and compared between the groups. During follow-up at a median of 8.3 years in children with myocardial ischemia, clinical endpoints occurred more often (47 vs. 5; p = 0.02) and more patients reached a clinical endpoint (28 [40%] vs. 3 [14.3%]; p = 0.036). In children with myocardial ischemia, myocardial fibrosis was observed with greater frequency. Myocardial perfusion defects may reflect an ischemic process which (1) affects the clinical manifestations and (2) is an important predictor of adverse clinical events and risk of death in children with HCM. Myocardial ischemia in HCM patients frequently correlates with myocardial fibrosis.

Keywords: Children; Hypertrophic cardiomyopathy; Myocardial ischemia; Prognosis.

Fig. 1

SPECT imaging: patient with septal and left ventricular posterior wall hypertrophy. Fixed perfusion defects were detected during exercise in the basal segments of septum and in the left ventricular inferior wall. Perfusion defects not resolved at rest

Fig. 2

SPECT imaging: patient with asymmetric septal hypertrophy. Perfusion defects were detected only during exercise in the basal segments of septum and in the left ventricular inferolateral wall. Perfusion defects completely resolved at rest

Fig. 3

Late gadolinium enhancement (LGE) on cardiovascular magnetic resonance (CMR) imaging in a child with hypertrophic cardiomyopathy. LEFT: cine image shows asymmetrical hypertrophy; MIDDLE: short-axis LGE image shows extensive mid-wall fibrosis; RIGHT: long-axis four-chamber LGE image confirms extensive mid-wall LGE in the septum

Fig. 4

Kaplan-Meyer curves for groups with (blue) and without myocardial ischemia (red). a Endpoints include sudden cardiac death, resuscitated sudden cardiac arrest, adequate ICD discharge, heart failure-related death, heart transplant, syncope, and non-sustained ventricular tachycardia. b Endpoints include arrhythmic events such as sudden cardiac death, resuscitated sudden cardiac arrest, adequate ICD discharge, and non-sustained ventricular tachycardia

Fig. 5

Kaplan-Meyer curves for groups with fixed (blue) and reversible perfusion defect (red) showing no substantial differences between groups. Endpoints include sudden cardiac death, resuscitated sudden cardiac arrest, adequate ICD discharge, heart failure-related death, heart transplant, syncope, and non-sustained ventricular tachycardia