In this column, I’ll talk about the varied tests done in cardiology in general and how we do them in a COVID-19 world. After all, people don’t stop having heart trouble because of a pandemic. First, I will discuss the various facets of the heart, how the tests are done and how we check them now. These are only the common tests usually done in doctor’s offices. I will not discuss heart catheterization, stenting, etc., at this time.
- Heart muscle function and valves: The most common test done is an echocardiogram. It is an ultrasound of the heart and can show cavity sizes, muscle thickness, valve function, septal defects, aorta and pulmonary pressures. Because of COVID-19 concerns, both the technician and the patient wear masks, so it is safe. Temperatures are taken, as well. Only a few people are allowed in the area.
- Coronary artery disease: The most common test done is stress testing. This can be done in one of many ways. The first part is how to stress the heart and the second is how to gauge the response. The simplest way is to exercise the patient on a treadmill and look at the EKG response. However, here in Florida, a lot of our patients are old and cannot exercise. Also, in people with abnormal EKGs the exercise EKG may not be interpretable. Finally, in women, the exercise EKG may be difficult to interpret. In all these patients, we need another way to look at the heart.
- Nuclear imaging: The patients can be stressed with a chemical that mimics the heart response with exercise. The common way to image the heart in these patients is by injecting a radioactive isotope. This is usually a Technetium compound that is taken up by the active myocardial cells. It has a short half-life, and two sets of images are done; one post stress and the other at rest. The doctor can compare the stress images with the rest images. The stressing agents are adenosine, Lexiscan, or dobutamine.
- Adenosine and Lexiscan work by increasing blood flow in normal heart arteries. Arteries with blockage will have decreased flow and images from that segment will look a little dull compared to normal arteries.
- Dobutamine, on the other hand, works by making the heart squeeze harder, and therefore needing more blood to work harder as with exercise.
In Covid times, we generally prefer chemical stress testing to exercise testing because it decreases the likelihood of droplet secretions which is likely with exercise. Of course, masks are worn.
- Stress Echo: A stress test can be done with imaging of the heart by echo. Wall motion is seen at rest and with either exercise or with dobutamine. Heart rate and EKG are monitored closely to increase the heart rate
- Electrical activity and heart rhythm: The simplest way this can be done is by an EKG. This can show rhythm problems, heart attacks, hypertrophy, enlargement, tachycardia etc. It is always good to have a baseline tracing so that subsequent changes can be monitored.
- Arrhythmia: Irregular heart rhythm often will need monitoring for a longer period. Three kinds of monitors are available: a Holter that is for 24-48 hours, an event monitor (usually for a month) and an implanted Loop recorder, which is implanted under the skin on the chest and can stay in place for months.
In short, all cardiac tests are being done now just as we used to do pre-covid. It can be done in a manner that keeps patients, healthcare staff, and doctors safe.