Researchers have found a connection between the abuse of most drugs and adverse cardiovascular effects, ranging from abnormal heart rate to heart attacks. Injection drug use can also lead to cardiovascular problems such as collapsed veins and bacterial infections of the blood vessels and heart valves.
Drugs affect the function of the heart in three main ways. They can affect the force of contraction of the heart muscle (inotropic effects) they can affect the frequency of the heartbeat, or heart rate (chronotropic effects) or they can affect the regularity of the heartbeat (rhythmic effects). Once drugs are taken and enter the bloodstream the heart pumps blood containing the drug to the brain where it will affect how people feel. Drugs can also have an effect on the heart directly and exacerbate heart disease. Heavy drinking of alcohol, for example, can weaken the heart's ability to pump blood and lead to heart failure although some studies have suggested that moderate consumption may be better for the heart than not drinking alcohol at all.
Taking regular and high doses of stimulant drugs like amphetamine, cocaine/ crack, ecstasy, anabolic steroids and even possibly caffeine may increase the risk of heart attacks, especially for people who already have heart problems or high blood pressure. Heavy tobacco use can also lead to greater risk of heart problems. Nicotine, as a kind of stimulant, increases the workload of the heart, while carbon monoxide deprives the heart of the oxygen it needs. Smoking also tends to thicken the blood hence making it less able to flow through narrowed arteries.