Preventing and Reversing Heart Disease For Dummies. James M. RippeЧитать онлайн книгу.
Having more fun: Nothing slows you down or scares the family like a heart attack. Angina pain, angioplasty, coronary artery bypass surgery, and other common outcomes of heart disease aren’t picnics in the park, either. Working for heart health and controlling heart disease can help you avoid these problems.
Chapter 2
Understanding the Onset and Outcomes of Heart Disease
In This Chapter
▶ Understanding what causes atherosclerosis and coronary heart disease
▶ Determining the causes and effects of angina
▶ Exploring what causes heart attacks
▶ Learning about arrhythmias, heart failure, and other forms of heart disease
Your heart works harder than any other muscle in your body. Your life depends on this small but mighty pump never stopping. It’s about the size of your clenched fist and weighs less than a pound. Depending on your age and physical condition, a normal heart beats 60 to 90 times per minute when you are sitting and may get up to 150 to 200+ times per minute when you are maxing out aerobic physical activity. A healthy heart is equipped to sustain at this pace for 70 to 90 years and beyond. The key word here is healthy.
From the moment you are born (and even before), multiple factors related to your biology, behavior, and environment have an impact, for good or ill, on your heart and cardiovascular system. Heart disease is progressive: It starts stealthily in the coronary (and other) arteries and progresses silently for years before any detectable signs of disease emerge. Research over the last 25 years provided new insights into how heart disease begins, starting at the cellular and molecular levels. These new insights are helping to prevent heart disease in the first place and to halt or, in some aspects, even reverse its progress.
In this chapter, I first present a brief overview of the heart and cardiovascular system. Then, I discuss the silent precursors and early stages of heart disease. Next, I look at angina and unstable angina, two types of chest pain that are often the first signs of heart disease for many people. Finally, I discuss how disease progression may result in heart attacks, arrhythmia (heart rhythm problems), heart failure, and other acute problems.
Touring the Heart and Cardiovascular System
Understanding how your heart and cardiovascular system work provides a foundation for understanding heart disease and its many manifestations. Even if you begin snoozing at the mere idea of technical stuff, don’t forget that knowledge is power. These basics can help you do a better job of keeping your heart healthy.
Pumping for life: The heart’s anatomy and function
✔ The heart muscle: Called the myocardium (myo = muscle and cardium = heart; pronounced my-o-car-dee-um), this muscle contracts and relaxes to pump blood throughout the cardiovascular system.
✔ The coronary arteries: Three large coronary arteries and their many branches deliver a continuous supply of oxygenated blood to the heart. Narrowing of these arteries causes chest pain; blockage causes heart attack.
✔ The pumping chambers: The heart’s job is to pump blood to the lungs to get oxygen and to pump the oxygenated blood to the rest of the body. To fulfill these tasks, the heart has a left and a right side (shown in Figure 2-2), each with one main pumping chamber called a ventricle located in the lower part of it. Sitting above the left and right ventricles are two small booster pumps called atria (or atrium, when you’re talking about just one).
The right ventricle pumps deoxygenated blood from the body to the lungs to receive a new supply of oxygen and back to the heart, through the left atrium to the left ventricle. The left ventricle pumps oxygenated blood through the arterial system to the rest of the body where it feeds every single living cell. Various disease conditions can damage each of these structures.
✔ The valves: Four valves regulate the flow of blood in and out of the heart and from chamber to chamber. They act a bit like cardiac traffic cops by directing the way blood flows, how much of it flows, and when to stop it from flowing. Disease and injury can cause heart valves to leak, narrow, or otherwise malfunction, disrupting the heart’s ability to pump blood efficiently.
✔ The electrical system: This electrical system is controlled by a group of specialized cells that spontaneously discharge, sending electrical currents down specialized nerves and tissues, causing the heart to contract. When any of these electrical structures becomes diseased or disordered, arrhythmias (ay-rith-mee-uhz), or heart rhythm disturbances, occur.
✔ The pericardium: The entire heart is positioned in a thin sac called the pericardium (peri = around and cardium = heart; pronounced per-ry-car-dee-um). Fluid within the sac lubricates the constantly moving surfaces. Inflammation of the pericardium from an infection or other cause causes pericarditis. Build-up of excess fluid inside the pericardium can cause problems with how the heart functions, a condition called cardiac tamponade.
Illustration by Kathryn Born
Figure 2-1: A typical healthy heart.
Illustration by Kathryn Born
Figure 2-2: The interior of a normal heart.
Connecting every cell in your body: The cardiovascular system
A pump is useless without the rest of the plumbing, which in your body is called the cardiovascular system. Here’s a quick look at how it all fits together and functions.
✔ The lungs: The lungs are composed of an intricate series of air sacs surrounded by a complex, highly branching network of blood vessels. Their sole purpose is to receive the deoxygenated blood from the heart, fill the red corpuscles full of fresh oxygen, and send them back to the heart for delivery to the body. The red blood cells give off waste products such as carbon dioxide at the same time they take on oxygen; the lungs then expel the carbon dioxide. This low-pressure system facilitates the rapid flow and reoxygenation of enormous amounts of blood.
✔ The arteries: As oxygenated blood returns to the left side of the heart, it is pumped out to the body through the aorta, the main artery of the body, and into the rest of the arterial system to feed the entire body with oxygenated blood. Although the heart exerts enough force to push oxygenated blood throughout the body, the arteries also have muscular walls that help push the blood along. The force exerted against resistance of the artery walls creates a high-pressure system that is very elastic to allow the arteries to expand or contract to meet the needs of various organs and muscles. Your blood pressure reading results from measuring the pressure in these arteries when contracting and at rest. (Read more about high blood pressure in Chapter 8.)
✔ The capillaries: The arterial system divides and redivides into a system of ever smaller branches to distribute nourishing blood to each individual cell, ultimately ending up in a network of microscopic vessels called capillaries, which deliver oxygenated blood to the working cells of every organ and muscle in the body.
✔ The veins: After oxygen leaves the capillary system, the deoxygenated blood and waste products from the cells are carried