Background: Hypoplastic left heart syndrome (HLHS) encompasses a spectrum of structural cardiac malformations that are characterized by severe under development of structures in the left heart-aorta complex, including left ventricular cavity. Autopsy reports of this condition occurring in the Indian population are not available. This study was undertaken with the aim of documenting the spectrum of morphological changes of HLHS seen at neonatal autopsy. Methods: All autopsies over a period of fifteen years at All India Institute of Medical Sciences were reviewed and all cases of HLHS were included for analysis. The gross anatomical descriptions, histology and gross specimens were reviewed. Results: Of 618 neonatal autopsies, 6 were found to have HLHS (0.98%). All the six cases showed hypoplasia of the ascending aorta and left ventricle. On morphology and microscopy, two patterns were seen. Pattern 1, seen in four cases, showed partly stenotic patency of mitral and aortic valves, fibroelastosis of the left ventricular endocardium and mural hypertrophy of left ventricular myocardium. In Pattern 2, seen in two cases, there was complete atresia of mitral valve with slit like left ventricle and normal left ventricular endocardium. On microscopy, Pattern 1 cases showed fibroelastotic thickening and calcification of the endocardium. Myocardium showed hypertrophy and presence of sinusoidal vessels. These findings were absent in Pattern 2. All cases showed atrial septal defect and wide patent ductus arteriosus , which are essential to maintain circulation. Conclusion: Hypoplastic left heart syndrome is a complex disorder with a spectrum of malformations. A simplified division into two patterns is useful for autopsy practice and helps in accurate dissection and assessment.

Key words: Hypoplastic left heart syndrome, Endocardial fibroelastosis, Pathology, Autopsy, Congenital heart disease