Whitney Houston Cause of Death: How Cocaine Contributes to Heart Disease

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.

In Photos: Whitney Houston's Final Days

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.