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This chapter describes in greater detail the common and uncommon heart-related causes of sudden death as well as the non-heart-related causes.1 In King County, Washington, 72 percent of people who experience cardiac arrest and who receive care from emergency medical services have underlying heart disease as the cause of cardiac arrest. The remaining 28 percent suffer from a variety of causative conditions. Among them are respiratory disease (7 percent); stroke and aneurysm (3 percent); cancer (4 percent); drug overdose and alcohol intoxication (3 percent); sudden infant death syndrome (2 percent); renal disease (1 percent); drowning (1 percent); other conditions, including anaphylaxis (6 percent); and unknown causes (1 percent; see figure 3.1). heart disease as the cause of cardiac arrest As figure 3.1 illustrates, underlying heart disease is by far the leading cause of cardiac arrest.2 The term “underlying heart disease” refers in general to problems of the heart. The specific causes of heart disease that may lead to cardiac arrest are listed in table 3.1. Myocardial ischemia and myocardial infarction are responsible for 70 to 75 percent of all cardiac arrests connected with underlying heart disease. The remaining 25 to 30 percent of such cardiac arrests are caused by a variety of other heart conditions, including congestive heart failure, dilated and hypertrophic cardiomyopathy, primary electrical diseases (long Q-T syndrome, Brugada syndrome, and Wolff-ParkinsonWhite syndrome), valvular heart disease, and commotio cordis, all of which are described in this chapter. 44 three Causes of Sudden Cardiac Death coronary artery disease and ischemia At first William A., a retired pharmacist, thought it was his typical angina—a squeezing sensation under his breastbone, radiating into his upper left arm. The pain tended to be triggered by eating a large meal or making a strenuous effort, such as climbing stairs too fast or mowing the lawn on a hot day. William’s doctor had told him about some anginaprevention medications he could take before such activities, but William hadn’t yet filled the prescription. (Ironically, this former pharmacist didn’t like taking medications.) William’s angina usually let up if he rested and took a nitroglycerin tablet or two. But this time the pain was still there after three tablets. William wondered if he should take a fourth, or call 911 as his doctor had told him to do if his symptoms persisted after three tablets. He decided to do neither. Instead, he would just wait and see if the pain subsided . The last thing he wanted was an ambulance racing up to his house with lights flashing and sirens blaring. Over the next fifteen minutes, the pain and pressure in his chest did seem to lessen somewhat, and it occurred to William that it might be a good idea for him to start taking the medications his doctor had mentioned. And that was his last thought. As his heart fibrillated, he instantly lost his pulse and blood pressure. That evening William’s daughter, after phoning him repeatedly, found him slumped on one side of his favorite chair. He looked peaceful, she said later. causes of sudden cardiac death 45 3.1 Causes of cardiac arrest, by percentage in King County, Washington, 1980-2010, for cases in which EMS personnel attempted resuscitation. William’s death from sudden cardiac arrest was due to underlying coronary artery disease (also known as “atherosclerotic heart disease” or “ischemic heart disease”). The actual trigger of ventricular fibrillation was the ischemia in his heart muscle. The term “ischemia” means a condition in which insufficient blood and oxygen are reaching the heart muscle. It leads to the symptom of angina, which is like a muscle cramp.3 Ischemia is the most common cause of sudden cardiac death, probably accounting for 40 to 50 percent of all sudden deaths due to underlying heart disease. The symptoms of angina typically occur before the heart fibrillates. They may be brief, perhaps lasting only seconds or minutes, or they may go on for hours. Clearly, the fact that an area of the heart is receiving insufficient blood and oxygen is the trigger for the VF episode. What is not so clear is why a particular episode of angina has triggered VF, especially when the victim may have had dozens and dozens of anginal episodes without any long-term harm. What separates the fatal bout of ischemia from the routine one? The answer is not known. acute myocardial infarction Harold R.’s wife had...

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