Ask the Doctors March 2011 Issue

Ask The Doctors: March 2011

I live in a city where the air quality can be very poor at times. Can you tell me how dangerous poor air quality can be for heart health, and how I can reduce the risk?

Air pollution is generally divided into two categories: particulate matter (PM) and gases. Data from multiple population-based studies have shown a strong association between elevated PM levels–particularly particles smaller than 2.5 microns in diameter (PM2.5)–and cardiovascular disease (CVD). Links have been found between exposure to air pollution and abnormal function of blood vessels, increased blood pressure, arrhythmias, inflammation in the body, blood clotting, and progression of atherosclerosis. Cardiac events are increased in persons exposed to higher levels of PM. Both short-term and long-term cardiovascular mortality are also elevated. As a result of these worrisome findings, which continue to accrue each year, the 2010 American Heart Association’s updated Scientific Statement on PM and CVD stated their opinion that "the overall evidence is consistent with a causal relationship between PM2.5 exposure and cardiovascular morbidity and mortality."

Your question is an apt one: Other than heading for the hills, how do we reduce this risk? Part of the problem is figuring out which sources of pollution, including motor vehicle traffic, wood stoves, power plants, or steel mills and other industrial structures, are contributing most to local (ambient) levels. Until more specific information has been gleaned, public air policy should be aimed at generally lowering release of potentially-harmful PM. As for what you can do to reduce your exposure and cardiovascular risk, EPA recommendations can be found on http://airnow.gov/, their public website. When the Air Quality Index (AQI) is unhealthy (151-200), persons with heart or lung disease, the elderly, and children should avoid prolonged or heavy exertion, and all other persons should reduce such activity. Plan strenuous activity when particle level forecasts are lower, and reduce time spent doing vigorous activities outdoors. Avoiding streets with especially heavy traffic (for example, during rush hours), may be helpful.

I’ve had a pacemaker for many years and have developed persistent atrial fibrillation (AF). In the past three years, I’ve also had episodes of ventricular tachycardia (VT). I had valve surgery six years ago and am concerned that the pacemaker lead may have been damaged during surgery. What should I know about a replacement pacemaker?

The most concerning element of your history is the onset of VT. This arrhythmia is potentially dangerous, and needs to be addressed soon. The first study I would recommend is a nuclear stress test. It is important to make sure you do not have a problem with blood flow to your heart muscle tissue, which can cause ischemic VT. If the stress test is abnormal, you may require a heart catheterization to assess the status of your coronary arteries, and to determine whether or not you need stents placed to open up narrowings. On the other hand, if the stress test is normal, then you probably suffer from nonischemic VT. An echocardiogram should also be performed, mainly to measure the pump function of the ventricles, and to look at your valves.

It is indicated for you to start taking a beta-blocker, such as metoprolol, which can be very effective for this purpose. Regarding your pacemaker lead, it is very unlikely that damage to it would lead to VT. However, an office-based interrogation of the pacemaker would reveal if the lead was malfunctioning. In any case, it sounds like you will probably need replacement of your current pacemaker with an implantable cardioverter-defibrillator (ICD). The presence of VT which is sustained (lasting >30 secs) is a strong indication for an ICD, which can either pace the heart out of VT, or if this is unsuccessful, deliver a potentially life-saving shock. The minor procedure will require placement of a new ventricular lead, as well as a new pulse generator.