The Heart: What Makes It Tick
Healthy blood vessels help keep the beat
by the Numbers
|Here are some recommended goals for people with diabetes to help prevent or slow cardiovascular disease.|
|HDL ("good") cholesterol||For men:
For women: greater than
|LDL ("Bad") cholesterol||Less than
|Triglycerides (blood fats)||Less than
|Blood pressure||Less than 130/80 mmHg|
|Source: American Diabetes Association Clinical Practice Recommendations|
Forget about Elvis. As far as heartbreakers go, diabetes is king. Adults with diabetes, whether type 1 or type 2, are two to four times as likely to die from heart disease as those without the disease. While diabetes is defined by too much glucose in the blood, this disease takes its greatest toll on the heart. More than two-thirds of diabetes-related deaths in people 65 and older are from heart disease, according to the Centers for Disease Control and Prevention. Heart disease is the No. 1 cause of death in the United States and has been for decades. Yet the connection between diabetes and heart disease is anything but obvious; researchers are still working out the details.
Worried about your heart? Here's a primer on this vital organ. Learning about what makes the heart tick can help it keep thumping along for many years to come.
The human heart is one hardworking organ, beating about 3 billion times during an 80-year lifespan. Roughly the size of a fist, the heart is nestled snugly behind the rib cage, a bit closer to your left arm than to your right. Its job is to pump blood throughout the body. It is made up of four muscular chambers, separated by a system of one-way valves through which blood flows. The heart is divided into right and left sides, each with two chambers: an atrium at the top and a ventricle at the bottom.
Blood pumped from the heart carries oxygen, an essential chemical ingredient for the process that ultimately turns food into energy for the body. As blood circulates through the body, cells help themselves to the oxygen it carries. When blood returns to the heart, its oxygen spent, it enters the right atrium. From there, it proceeds to the right ventricle, which pumps blood to the lungs for a breath of fresh air. The newly oxygenated blood then reenters the heart via the left atrium and moves into the left ventricle, the strongest chamber, which squeezes hard enough to propel blood out to the body, from your heart to your head to your toes and back again.
Heartbeats are a continuous progression of contractions and relaxations. The contractions are triggered by electricity produced by specialized heart cells (this is the electricity measured by an electrocardiogram). When the heart forces blood out of the ventricles, either to the lungs or to the rest of the body, this contraction is called systole. Between contractions, the heart relaxes and the ventricles fill with blood. This is called diastole. Accordingly, blood pressure during a contraction is called systolic (the top-line number in a blood pressure reading); during relaxation, it's called diastolic (the bottom-line figure).
It may seem strange that heart disease doesn't usually start with the heart at all, but with blood vessels. This is why heart disease and stroke (caused by damaged blood vessels leading to the brain) are also referred to as cardiovascular disease.
Healthy blood vessels are flexible tubes that make an ideal thruway for the blood and its cargo of oxygen and nutrients; anything that stymies this flow is a serious problem. Enemy No. 1 is atherosclerosis, the stiffening and narrowing of arteries caused, in part, by fatty plaques that build up along blood vessel walls.
These plaques are formed when the levels of fats in the blood diverge from their normal ranges. Triglycerides and LDL ("bad") cholesterol that are too high, coupled with HDL ("good") cholesterol that is too low—a trio of characteristics common in people with diabetes—are classic risk factors for developing atherosclerosis, as are smoking and high blood glucose. High blood pressure can also damage vessel walls, leading to accumulations of cell debris that form the core of atherosclerotic plaques.
Atherosclerosis can occur and cause disease in just about any blood vessel in the body. For example, atherosclerosis in the legs can cause peripheral arterial disease (PAD); in the vessels leading to the brain, it may lead to a stroke. Atherosclerosis in the coronaries, the arteries that supply the heart muscle with blood, can starve the heart of oxygen and cause the most common form of heart disease: coronary heart disease (also known as coronary artery disease). In milder forms, this blockage causes angina, pain or discomfort associated with a shortage of blood to the heart. In severe cases, atherosclerosis can completely stop the flow of blood to the heart. This is what causes a heart attack, or myocardial infarction.
Another type of heart disease is heart failure, a weakening of the heart's pumping ability due to structural changes in the heart muscle. Causes include coronary artery disease, high blood pressure, diabetes, or some combination of these factors. Structural changes or damage to the heart can alter the electrical messages that keep the heart beating, causing arrhythmia, an abnormal beating pattern. Arrhythmias can contribute to heart failure and stroke, and severe arrythmias can cause sudden death due to cardiac arrest.
Taking care of your heart means showing some TLC to your blood vessels. In the early stages of heart disease, you can feel perfectly fine, so it's essential to visit your doctor regularly to spot mild problems before they get worse. Not smoking, eating a veggie-rich diet that's low in saturated fat, salt, and cholesterol, and exercising at least 30 minutes a day five days a week will help stave off heart disease in part by keeping blood fats and blood pressure in their optimal ranges (see chart). People with diabetes should follow all of these guidelines while also practicing good blood glucose control to avoid cardiovascular disease, as well as other complications.
Should the risk factors for damage to the blood vessels start to worsen, medications to lower blood pressure and LDL cholesterol can supplement a good diet and plenty of exercise. Adding blood-thinning medications, such as aspirin, to the mix may also thwart heart disease by keeping blood circulating smoothly. Medications that regulate heart rhythm may be beneficial in cases of arrhythmia. Of course, you should always discuss medications and the reasons for taking them with your doctor.
When meds aren't enough, a procedure may be necessary. For coronary heart disease, doctors may suggest either angioplasty or bypass surgery. Angioplasty uses a tiny balloon and stent to prop open a narrowed coronary artery, allowing blood to get to the heart. Bypass surgery creates an alternate route—using a vein taken from another part of the body and grafted in place—for blood to get around an atherosclerotic blockage. If the problem is rhythm, medical procedures may help reset the heart's electrical pacing, or a pacemaker can be implanted to deliver electrical signals that regulate the heartbeat.
As numerous as heart problems can be, lifestyle changes, medication, and surgery offer just as many possible solutions. Prevention is ideal, but even if you're faced with heart disease, it's rarely too late to make a change for the better.