Ask the Doctors May 2011 Issue

Ask The Doctors: May 2011

I recently started using supplemental oxygen because I have chronic obstructive pulmonary disease (COPD). Iím still fairly active, but Iím concerned about an upcoming mitral valve operation. How will relying more on supplemental oxygen affect my heart and circulation?

You are not alone in having the dual problems of heart and lung disease. In some cases, such as coronary artery disease and COPD, the disorders share major risk factors, such as smoking. Also, patients with COPD can sometimes develop higher pressures in their pulmonary arteries due to the COPD. The most important issue at hand is that you use the supplemental oxygen as instructed by your doctor, since low oxygen levels in the blood can put undue strain on the heart, sometimes even causing injury. Also, persons with COPD often become less and less active, both due to adverse symptoms, and because they resent needing to wear oxygen when they exercise. It is important that you continue to be as active as you can, even if it means wearing your oxygen when you exert yourself.

With regards to your impending mitral valve surgery, the COPD and dependence on supplemental oxygen do have certain implications. It will be important for the surgeons and anesthesiologists to know specifically how impaired your lung function is, in order to treat you better during the perioperative period. This information will be obtained by pulmonary function tests prior to the operation. It may prove more difficult to "wean" you off of the ventilator during the period immediately after the surgery, and other treatments such as continuous positive airway pressure may be needed to "bridge" you back to normal breathing. However, you should know that most patients with COPD can undergo cardiac surgery with a minimum of risk, as long as the hospital and its clinical personnel are experienced in handling such individuals. I would recommend that you discuss these considerations with your cardiologist and cardiac surgeon prior to surgery.

At a recent checkup, I was told that I had experienced a mild heart attack, even though I donít recall having any symptoms. What does this mean for my future heart health and am I now more likely to have a major heart attack?

Your situation raises two important questions: How do doctors diagnose a previous heart attack, and how does this change your risk of a future event? If you were admitted to a hospital in the past with clear symptoms and clinical evidence of a heart attack, the answer is obvious. However, a "silent" heart attack is often diagnosed simply on the appearance of the 12-lead electrocardiogram (EKG), the unique electrical "signature" of a personís heart. Although the EKG is a wonderfully useful, noninvasive test, it is not always correct. Some patients appear to have experienced a past heart attack simply due to the position of the heart in the chest cavity, the placement of the electrical leads on the chest wall, or an electrical abnormality of the heart unrelated to coronary artery disease.

In order to prove whether someone has truly experienced a silent heart attack, various tests can help clarify a diagnosis. An echocardiogram of the heart is an ultrasound which may reveal abnormalities of the left ventricle (LV). Wall motion abnormalities of the LV, or a reduced LV ejection fraction can provide clues to whether a past heart attack has occurred. Another useful test is a nuclear stress test, which can demonstrate if certain areas of the heart muscle tissue have been replaced by scar. Stress tests can also suggest the presence or absence of ischemia, a condition in which blood flow to the heart muscle tissue is normal at rest, but reduced during stress. Ischemia is generally worked up further with heart catheterization and coronary angiography, since it usually indicates severe coronary artery narrowing. If heart tissue scarring is identified, without the presence of ischemia, the decision of whether or not to do a heart catheterization is more debatable, and should be discussed with your cardiologist.