Eva Rausing, the wife of the Tetra Pak heir Hans Rausing, died from the effects of cocaine on a damaged heart, two months before police found her body under piles of bedding and plastic in a squalid apartment within the couple's London mansion.

The inquest into her death was told how her husband was shaving in the bathroom when he heard her slip from the bed, saw her eyes dulling as he tried to lift her, and knew she was already dead. In her left hand, a London coroner's court heard, she still held a piece of foil rolled into a tube for smoking cocaine.

Mr Rausing hid her body, unable to face up to her death, and told anyone who asked that she had gone to California, Westminster coroner's court heard.

The inquest was told that Mr Rausing, who was given two suspended sentences in August for preventing the lawful burial of her body, was medically unfit to give evidence in person, but in a long statement he described their marriage as "very close and loving", and said he was "devastated" at her death.

The death was discovered on 9 July, when police stopped Mr Rausing for erratic driving and found a still warm crack cocaine pipe in the footwell, and a plastic bag full of unopened post to his wife in the boot. At their huge house in Cadogan Place they found the badly decomposed body in the second-floor apartment where the servants – who had last seen her in late April – had been told never to set foot.

Police first suspected foul play, but the inquest heard there was no evidence of violence. Toxicology tests showed traces of cocaine, opiates and amphetamines.

PC Darren Reynolds said the apartment, reached only by an internal lift, resembled a squat, with drug paraphernalia, clothes and furniture littered about. Officers were immediately aware of a smell of decomposition. In the bedroom they saw a large bed covered in blue tarpaulin that stretched beyond it to cover the space to one side, weighed down with pieces of furniture including a 50-inch television. Under layers of plastic, clothing, blankets and duvets, they eventually found the body.

Ms Rausing was identified from a thumb print and the serial number of a pacemaker fitted six years earlier. The pacemaker showed there had been chaotic disruption of its rhythm at 7.19am on 7 May, almost certainly the time of her death.

Her husband's statement said that although they met in rehab, both had been clean of drugs and alcohol for years, until on New Year's Eve 1999 she decided to drink champagne. Both were soon back on drugs, though she first tried to hide her cocaine use from him. He never supplied her with drugs, he wrote, and she did not tell him where she got hers.

She made a last attempt to get clean, but returned having been asked to leave a clinic in Malibu because she had kept forbidden Valium pills.

He described a reclusive life in the last months, when they spent almost all the time alone together in the apartment. "We both felt things were completely hopeless," he wrote.

The deputy coroner, Dr Shirley Radcliffe, found Ms Rausing died as a result of cocaine intoxication, on the balance of probability on 7 May, and noted that the drug could seriously damage the heart.

Rausing had had heart valve surgery as well as the pacemaker, but repeatedly missed follow-up appointments. "Mrs Rausing's death was as a result of dependent abuse of drugs," she said.

Radcliffe described Mrs Rausing's life as being on a "downward trajectory" as she failed to take care of her physical and mental health. "I offer my condolences to the family for the loss of a 48-year-old mother, wife, sister and daughter," she added.