Ask Dr. Zipes
The Amazing Heart
A noted cardiologist answers your questions.
By Douglas Zipes, M.D.
From the November/December 2005 Issue
Reader: It has been written that the heart's beat is caused by "electricity" and that energy is made up of electrons. Where does this electrical impulse come from? Where is it generated? Are we receptors? Do we "store" energy like a battery? Dr. Zipes: Each heartbeat begins in a small bundle of cells in the top right part of the heart called the sinus node (see right). The electrical impulse is due to the flow of ions, mainly sodium, potassium, and calcium, in and out of the cells. This process cannot be seen visually but can be recorded easily by an electrocardiograph or similar instrument. The impulse then travels to both top chambers of the heart called the right and left atria, and then over specialized tracts to the bottom chambers, called the right and left ventricles, causing each chamber to contract in turn and squeeze blood forward. The atria push blood into the ventricles to help fill them with blood. The right ventricle pumps blood to the lungs to pick up oxygen and get rid of carbon dioxide, and the left ventricle pumps oxygenated blood to the entire body. The heart does not "store" electricity but rather generates it for each heartbeat. If you do the math, you can calculate that the heart beats on average about 70 times a minute, 4,200 times an hour, 100,800 times a day, almost 37 million times a year, reaching almost 3 billion times in an 80-year-old person. It is truly an amazing organ! At times, problems can arise and cause irregularities in the heartbeat called arrhythmias. These can be treated with drugs or devices such as pacemakers and defibrillators.AAA Surgical Repair Reader: I have received conflicting advice about when an abdominal aortic aneurysm (AAA) requires surgical repair. My AAA is 4.8 cm. Is the operation so serious that the chances of survival are poor? I was told that I probably couldn't survive it. Dr. Zipes: You are correct in noting that size is the major issue in determining whether an abdominal aortic aneurysm will rupture and when surgery should be done to avoid that risk. Aneurysms smaller than 4.0 to 4.9 cm have a 1.5 percent annual rupture risk, and for those 5.0 to 5.9, the risk is 6.5 percent. For aneurysms greater than 6.0 cm, the annual risk of rupture rises sharply. Other important determinants are rapidity of size increase and whether abdominal pain is present.Controlling Cholesterol Reader: Kindly inform me what natural methods can be used to reduce cholesterol and LDL levels. Dr. Zipes: An appropriate diet of vegetables, chicken, and fish, along with daily exercise and avoidance of alcohol (although a little wine is beneficial), can help reduce total and LDL cholesterol. However, for most persons, the lifestyle is too stringent and/or the reduction is insufficient. Therefore, in the majority of people, drugs like the "statins" are a necessary adjunct.
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