The great Polish composer and pianist Frédéric Chopin had a morbid fear of premature burial. “The earth is suffocating,” he told one of his sisters as he lay on his death bed in 1849. “Swear to make them cut me open, so that I won’t be buried alive.”

An autopsy was duly performed to try to solve the mysterious cause of the 39-year-old’s death. His heart was removed and later stored in a jar of cognac, then interred in a church pillar in Poland.

Now scientists have taken advantage of Chopin’s morbid desire. Granted a rare opportunity to examine his pickled heart, they have concluded the musician was a victim of pericarditis, a rare complication of chronic tuberculosis.

The diagnosis, published in the American Journal of Medicine last week, is the latest and most convincing foray into the long-running dispute over the likely cause of Chopin’s slow decline and death in his 30s. Other suggested causes of his debilitation and death have included the inherited disease cystic fibrosis; alpha-1-antitrypsin deficiency, a relatively rare genetic ailment that leaves individuals prone to lung infections; and mitral stenosis, a narrowing of the heart valves.

But when the researchers examined the jar containing Chopin’s heart – kept in the crypt of the Holy Cross church in Warsaw – they noted the heart was covered with a fine coating of white fibrous materials. In addition, small lesions were visible, the telltale symptoms of serious complications of tuberculosis, concluded the team.

“We didn’t open the jar,” team leader Professor Michael Witt of the Polish Academy of Sciences told the Observer. “But from the state of the heart we can say, with high probability, that Chopin suffered from tuberculosis while the complication pericarditis was probably the immediate cause of his death.”

The new study is the latest chapter in the strange story of Chopin’s heart. The composer died in October 1849 in Paris and the rest of his remains lie in the city’s Père Lachaise cemetery, also the last resting place of Marcel Proust, Oscar Wilde and Jim Morrison. However, his status as a Polish national hero ensured his heart became embroiled in controversy.

Shortly after he died his sister Ludwika smuggled his heart into his homeland past guards from Russia (which then ruled Poland) and it was sealed inside the Holy Cross church.

During the Warsaw uprising in 1944, the heart was given to a high-ranking SS officer who professed to be a Chopin admirer. It was then kept in the local German high command headquarters before being returned to the church at the end of the second world war.

The examination of the heart by Witt and colleagues was the first since 1945. “We found it is still perfectly sealed in the jar,” said Witt. “Some people still want to open it in order to take tissue samples to do DNA tests to support their ideas that Chopin had some kind of genetic condition. That would be absolutely wrong. It could destroy the heart and in any case I am quite sure we now know what killed Chopin.”