People who already have damaged valves, producing an audible heart murmur when a stethoscope is used, are more susceptible to bacterial infection of the heart and need to take special precautions to avoid it. Hypertension is often the cause of heart disease, as well as of other serious organ failures. The heart is susceptible to various genetic and developmental problems as well. Some, such as aortic stenosis, are strictly diseases of the heart, while others, such as Down's syndrome or Marfan's syndrome , are pervasive disorders that usually affect the heart along with other organs. A wound to the heart is among the most dangerous of events, usually resulting in death in a matter of moments.
Electric shock can also stop a heart from beating.
In many cases a heart that has been stopped from beating for a brief period can be restarted. The technique is part of cardiopulmonary resuscitation, generally known as CPR, which is easily learned in special classes that are generally available. Sometimes emergency health workers also use certain electrical devices that can restore a heart to beating after it has stopped. Although heart disease is the leading cause of death, its incidence in the United States has been falling. The exact cause of the decline is not known for sure, but it is assumed that the population is increasing the practices known to reduce heart disease.