March 23, 2012 -- In an infamous 2002 interview with ABC News' Diane Sawyer, pop icon Whitney Houston candidly spoke about her abuse of drugs such as cocaine, which, along with heart disease, factored into her accidental drowning last month, according to the Los Angeles County Coroner's Office.
"It has been [alcohol, marijuana, pills, cocaine] at times," Houston told Sawyer in the frank 2002 interview that delved headlong into her addiction struggles. "Nobody makes me do anything I don't want to do. It's my decision; the biggest devil is me. I'm my best friend and my worst enemy."
In a statement to ABC News Thursday, the Los Angeles County Coroner's chief, Craig Harvey, outlined the findings in the office's preliminary toxicology report.
"We had approximately a 60 percent occlusion in the arteries, in the narrowing of the arteries," Harvey said. "So, that condition, complicated by the chronic cocaine use, all combined to result in her drowning. The final cause of death has been established as drowning due to atherosclerotic heart disease and cocaine use."
Atherosclerotic heart disease is a build-up of plaque that narrows the small blood vessels that supply blood and oxygen to the heart, according to the National Institutes of Health. It is not known how long the singer had the condition.
Despite the coroner's announcement, questions remain about the nature of the pop star's death after she was found "underwater and unconscious" in the bathtub in her room at the Beverly Hilton Hotel Feb. 11. It is still unclear how much her chronic drug abuse contributed to her death at 48, and whether she was already incapacitated when she drowned.
Dr. Michael Fishbein of the UCLA Medical Center, who spoke with ABC News regarding the coroner's office report, explained the short- and long-term effects that cocaine has on the heart, and speculated about what might have happened in Houston's final moments.
"The immediate effect of cocaine is that it interferes with the electrical system of the heart," Fishbein said. "An analogy might be a swimming pool pump. You can have a perfectly good pump, but if you cut the electrical cord, the pump stops working. If the heart stops pumping blood, and all the organs are deprived of oxygen. The tissue dies and the person dies."
Cocaine also increases the demand for oxygen, as it increases heart rate and blood pressure.
"The long-term effect is that cocaine causes the heart to be enlarged, which increases the risk of sudden death," Fishbein said. "It also causes scarring in the heart, which increases the risk of a sudden cardiac death, and it causes accelerated atherosclerosis, or a hardening of the arteries, which we associate with high blood pressure and smoking."
When occlusion in the arteries reaches 75 percent narrowing, it is typically considered dangerous, but, Fishbein says, 60 percent occlusion for a woman of 48 is above average.
Repeated cocaine use has been proven to raise the risk of heart attack risk, according to a 2008 report from the Beth Israel Deaconess Medical Center in Boston. Ten percent of heart attacks in people 18 to 45 years old were associated with more than 10 uses of cocaine over their lifetime.
The study led the American Heart Association to issue a statement urging doctors to consider the use of cocaine in young people with unusual cardiovascular or lung complaints.
Although Houston had been a chronic cocaine user throughout her life, as noted Thursday by the chief coroner, Fishbein said even a person with a normal heart can die of cocaine use and that if someone takes too much cocaine, he or she can die from even one exposure.
Perhaps the biggest mystery still surrounding Houston's death is whether the singer died before or after she was submerged underwater in her hotel bathtub: was she incapacitated and alive when she went under water, or was she already dead?
Medical examiners tend to say that someone has died of drowning if they are found in the water, and it is likely that water was found in Houston's lungs. In the report released Thursday, the coroner lists drowning first.
Fishbein says there are two possibilities in Houston's case.
"People can have what is called agonal respirations. That is, you can have a gasping breath, even after the heart is stopped. There are two possibilities: that she was incapacitated and alive when she went under the water, or she was basically dead, and the water got in with these respirations."
"How does someone die in a bathtub?" he asked. "It's not like they're swimming the English Channel. So she had to have been incapacitated. And I think that was due to the cocaine causing an abnormal cardiac rhythm."
Dr. Drew Pinsky, an addiction specialist and host of "Dr. Drew" on HLN, says that while the official cause of death was drowning, he believes Houston died from addiction.
"The cocaine probably caused some sort of cardiac arrhythmia or damage to the heart muscle, which resulted in her losing blood pressure and consciousness, and slipping into the water and drowning," Pinsky said.
It is still possible that these questions will be answered, and much of the mystery surrounding the star's death might still become clear, when the final coroner's report is released. It is expected within the next two weeks.