Most Americans don't eat enough fiber, and many people say it's because they are worried about eating too many carbs, but eating the right kind of carbs is the key, and it's not that difficult to meet the recommended daily amount.

Q. After my heart attack, my doctor told me that damaged heart muscle cannot be replaced. If this is true, why am I walking on a treadmill five days a week? Is this helping repair the heart muscle damage or strengthen what's left of my heart muscle?

A. Your skeletal muscles can repair themselves after an injury — pull your calf muscle and, after a few days or so, it heals. Until recently, it was believed that the human heart didn't have this capacity. But the heart does have some ability to make new muscle and possibly repair itself. The rate of regeneration is so slow, though, that it can't fix the kind of damage caused by a heart attack. That's why the rapid healing that follows a heart attack creates scar tissue in place of working muscle tissue.

Q. Some friends invited me to accompany them to Rocky Mountain National Park. I would love to go, but I have high blood pressure and worry that high altitudes are dangerous for people with  high blood pressure. Is that the case?

A. If you have high blood pressure but are otherwise healthy, your blood pressure is under control, and you take some precautions, a trip to the Rocky Mountains should be fine.

Arteries are the vital channels that carry oxygen-rich blood from the heart to all the body's tissues. When blockages develop, blood flow slows and tissues suffer. Blockages in the coronary arteries cause angina and heart attacks; blockages in the arteries that supply blood to the brain cause strokes. But the peripheral arteries that carry blood to the legs and other parts of the body are also vulnerable. Heart attacks and strokes get all the publicity, but peripheral artery disease (PAD) is a major problem that deserves more attention and respect — especially since new methods make diagnosis easier and treatment better than ever before.

What is PAD?

Like most strokes and nearly all heart attacks, PAD (formerly called peripheral vascular disease) is a form of atherosclerosis. Peripheral artery disease begins when LDL ("bad") cholesterol passes from the blood into the wall of an artery. Arteries damaged by high blood pressure, smoking, or diabetes are at particular risk. As the cholesterol builds up, it triggers inflammation, which adds to the damage. Unless treatment halts the process, the cholesterol deposit builds up into a plaque, or blockage, that narrows the artery. Mild narrowing may not produce any symptoms, but moderate narrowing may prevent tissues from getting the blood they need to fuel the extra work of exercise. When blockages are severe, the tissues suffer even during rest. Blood clots can add insult to injury by increasing blockages.

Q. On the day I stopped smoking a few weeks ago, I started using a nicotine patch. When I smoked, my blood pressure was great — 100/70. Now it is up to 160/90. I would hate to stop the patch, since it really helps, but I'm worried that it could cause high blood pressure..

A. First off, congratulations for trying to stop smoking. Every part of your body will benefit if you quit.

Q: What are the best ways to increase HDL (good) cholesterol levels?

A: Before I answer that question, why bother to increase HDL cholesterol at all? Many studies have found that people with low levels of HDL are at increased risk for heart attacks, strokes, and other complications of arteries diseased by atherosclerosis: that's why we call HDL the "good" cholesterol. Given that, you'd think that raising HDL levels would reduce a person's risk for atherosclerosis. Unfortunately, despite a lot of research, we don't yet know if that's true, nor how best to raise HDL levels.

Q. I have allergies. Could they be the reason I have high blood pressure?

A. Although allergies don't usually directly increase blood pressure, they can contribute indirectly to high blood pressure in two very different ways.

Symptoms, heart measurements guide the need for mitral valve surgery.

The heart is a marvel of biological engineering. Four strategically placed valves ensure that every contraction propels blood forward with little or no backflow. On the right side of the heart, the tricuspid and pulmonary valves direct the orderly flow of blood; on the left side, the mitral and aortic valves. Although all four valves are essential for good health, we focus on the mitral valve and mitral valve regurgitation in this article.

If the mitral valve is damaged or becomes misaligned, it can't close completely with each heartbeat. Some blood spurts backward with each contraction. This backflow, called mitral regurgitation, puts a strain on the heart. It can provoke symptoms such as breathlessness and fatigue and lead to atrial fibrillation or heart failure.

Ask the doctor

Q. What causes high blood pressure?

A. My answer is going to start in your back yard; stay with me. You're holding a hose, you turn on the water, and it shoots through the hose and out the nozzle. The water is moving because it's under pressure. Similarly, when your heart beats it creates pressure that enables your blood to "water" your body with the nutrients that are in your blood.

Three things affect the amount of pressure that pushes blood through your body: how forcefully the heart pumps, how much blood there is, and how narrow the smallest blood vessels are. That last one may need some explanation. When you're watering plants, and you want the stream of water to go farther, what do you do? You make the nozzle smaller. Narrowing the opening through which the water flows increases the pressure, and the water then is able to reach the distant flowerbed.

New guidelines provide advice on the role of drugs, weight loss, and procedures to cope with this common heart rhythm disorder.

The classic symptom of atrial fibrillation — a fluttering or thumping sensation in the chest — can leave you breathless, dizzy, and tired. Caused by electrical misfires in the heart's upper chambers (atria), this condition affects an estimated one in 11 people ages 65 and older.

While the symptoms of atrial fibrillation (often called afib) can be unsettling, the real danger is a heightened risk of serious strokes (see "How afib can lead to a stroke"). As many as 30% of strokes from afib prove fatal, notes Dr. Christian Ruff, a cardiologist at Harvard-affiliated Brigham and Women's Hospital.