Whitney Houston died because of a combination of cocaine, heart disease and, ultimately, drowning. The Los Angeles County coroner's preliminary report Thursday found heart disease had caused blockages in Houston's arteries, common in drug users, but could not determine whether she had had a heart attack.

"It's possible she fell asleep," says cardiologist Gina Lundberg, medical director of the Heart Center for Women at St. Joseph's Hospital of Atlanta.

"Based on the fact that the coroner lists drowning first would suggest she was alive when she went under the water, so she didn't have a heart attack first."

Houston died Feb. 11 at the Beverly Hilton, where she was discovered unresponsive and submerged in a bathtub.

The coroner's report points to chronic cocaine use, says chief investigator Craig Harvey.

"We feel that the cocaine coupled with the …heart disease complicated her condition," Harvey says. "Chances are if she did not have pre-existing heart disease and cocaine use, she might not have drowned."

The amount of chemicals found in Houston's body will be revealed in the final report expected in about two weeks.

Long-term cocaine use can cause inflammation and chronic damage to the blood vessels around the heart, which can lead to hardening of the arteries, says Cam Patterson, chief of cardiology at the University of North Carolina-Chapel Hill.

In the short term, a hit of cocaine can cause abnormal heart rhythms that can lead to sudden cardiac death.

"That could explain why someone seen just a few minutes earlier could suddenly drown," Patterson says.

Drowning likely wasn't the true cause of death, says pathologist Michael Fishbein of the Ronald Reagan UCLA Medical Center: "Cocaine is known to cause sudden cardiac death."

It can trigger heart disease as well, he adds, making heart rhythm failures more likely. "The fact that she was in a tub when she died may have been coincidental. She likely would have died just walking around."