What is pulmonary edema which cause the death of Stephen Gately

Do you know what is pulmonary edema which cause the death of Irish singer Stephen Gately, a member of the singing group Boyzone?
Pulmonary edema is a condition caused by excess fluid in the lungs. This fluid collects in the numerous air sacs in the lungs, making it difficult to breathe.
Pulmonary edema that develops suddenly (acute) is a medical emergency requiring immediate care. Although pulmonary edema can sometimes prove fatal, the outlook may be good when you receive prompt treatment for pulmonary edema along with treatment for the underlying problem. Treatment for pulmonary edema varies depending on the cause, but generally includes supplemental oxygen and medications.
Death by acute pulmonary oedema is a combined failure of heart and lung, with the former triggering a build-up of fluid in the latter. The result can be sudden and catastrophic — effectively causing a form of internal suffocation — though it is extremely rare in someone as young as Stephen Gately.
The most likely triggers for pulmonary oedema are problems with the rhythm of the heart, or the functioning of the heart muscle or a valve.
Rhythm irregularities may come on suddenly, such as atrial fibrillation.
Heart muscle function can fail as the result of a coronary or, more commonly in younger people, an inflammation of the muscle caused by a virus. If a heart valve is leaky or constricted, such as in aortic stenosis, it can also cause such failure.