About one-third of all patients cant exercise adequately to get good information without those pharmacologic agents. That means being able to walk for at least five minutes and reach 85 percent of maximum age-predicted heart rate: 220 minus age.
If you can exercise adequately, it increases blood flow to the heart about twofold, so you dont need pharmacologic agents, which increase blood flow four- to fivefold, says Dr. Robinson. An exercise EKG is the test we should try first if its feasible.
However, if a patient cant walk without pain, shortness of breath or other symptoms that led to testing in the first place, he goes right to stressing the heart with pharmacologic agents. The agents reduce the risk of the test for some patients, because their hearts dont have to work as hard. In fact, they have been used safely in patients approximately 48 hours after a heart attack, Dr. Robinson says.
Without these agents, exercise EKGs have about a 64 percent probability of picking up disease, leaving lots of room for concern if serious disease is suspected, he says. If you perform like an athlete, walk for 12 minutes with no EKG changes, are laughing and have no symptoms, that is a great test. That means your chance of needing revascularization, of having dangerous coronary artery disease that could kill you, is almost zero, Dr. Robinson says. But if you puttered along, got to five minutes and had chest pain but your EKG was still normal, you better believe I would go on to do pharmacologic stress with the perfusion agent. The point here is, in a lethal disease, you cannot accept a 64 percent probability of picking up the disease.
In some patients, such as those with pacemakers, exercise EKGs are not even a first option; pharmacologic stress agen
|Contact: Toni Baker|
Medical College of Georgia