In many complex forms of congenital heart disease, the aorta and pulmonary artery do not originate from their normal areas of the ventricles. In one of the most common of such cases—transposition of the great arteries—the aorta originates from the right ventricle and receives deoxygenated blood from the superior and inferior venae cavae , and the pulmonary artery arises from the left ventricle and receives fully oxygenated pulmonary venous blood. Survival in such cases depends on a naturally occurring communication between the two sides of the heart that allows oxygenated blood to enter the aorta; if such a communication is not present naturally, it may be created medically or surgically. Both the aorta and the pulmonary artery may originate from the right ventricle; this form of abnormal origin of the arteries usually is associated with a ventricular septal defect and, on occasion, pulmonary stenosis. This combination of defects is a severe form of cyanotic heart disease.
Clinical and epidemiological studies
There is no doubt that smoking is associated with considerably increased cardiovascular risk. However, nicotine is only one of the potential culprits in tobacco smoke and the risk associated with nicotine administration to humans has not been fully settled. An exhaustive review of the literature is beyond the scope of this article, so I will confine myself to summarizing a recent meta-analysis of studies on the cardiovascular safety of nicotine replacement therapy (NRT) as smoking cessation tool (assuming that the same holds for nicotine consumption using electronic cigarettes).