Researchers examining the pickled heart of Frederic Chopin think the famous composer died from complications of tuberculosis.

The Polish composer died in Paris in 1849 and was buried there, but his heart was smuggled back to his homeland Warsaw in a glass jar as had been his wish. During the Warsaw Uprising the Nazis allowed for the heart to be put in safekeeping and since 1945 it has been kept in a crypt at the Holy Cross Church in Warsaw. In 2014, though, a group of scientists got permission to inspect the jar in the crypt, hoping they would be able to identify Chopin’s cause of death. The results of their study show he most probably died from complications of tuberculosis.

The reason the composer asked for his heart to be preserved was because he was afraid he might be interred alive. He had even written a note before his death stating he wanted his body to be cut open so that he wouldn’t be buried alive. Ludwika Jędrzejewicz, Chopin’s eldest sister, respecting her brother’s wish, had an autopsy performed on the composer’s body and his heart removed and preserved. The autopsy records have not been preserved. Although the official version regarding the composer’s death was that it was caused by tuberculosis, some proposed he might have suffered from another disease.

Although many theories had emerged from time to time regarding his cause of death, ranging from cystic fibrosis to alpha-1-antitrypsin deficiency, no researcher had had the opportunity to examine the preserved heart. Doctors in Spain, on the grounds of accounts of Chopin’s hallucinations had proposed that he might have had epilepsy.

When the group of researchers, including priests and forensic scientists, were allowed to open the crypt and examine the heart, they found that the heart still floating in a liquid, probably cognac used for preservation. They noticed that the heart was covered in white fibrous materials and was dotted with lesions. They took hundreds of pictures hoping to perform a visual analysis of the organ. Michal Witt, from the institute of Human Genetics at the Polish Academy of Sciences, who led the team of researchers concluded that the composer had indeed suffered from tuberculosis and the immediate cause of his death was pericarditis or inflammation of the membrane around the heart, an uncommon but serious complication of the disease.

The findings of the study were published last month in The American Journal of Medicine.