Patients with coronary artery blockages may have minimal symptoms and an unremarkable or unchanged EKG while at rest. Alternatively, patients with no heart disease may have fairly convincing symptoms and a suspicious EKG. Both groups may benefit from a cardiac stress test during which exercise or a chemical substance is used to stress the heart and expose hidden heart disease or to help rule it out. .
The heart may be stressed by having a patient exercise on a treadmill or a stationary bicycle. If the patient is unable to exercise secondary to physical limitations such as severe arthritis, artificial limbs, generalized weakness, paralysis, unsteady gait, etc., the physician may choose a pharmacological or chemical form of test. In the latter case, a medication is given intravenously to perform a nearly comparable degree of cardiac stress. If possible, some form of pharmacological stress testing may be combined with a brief period of treadmill exercise.
Stress testing, particularly those employing exercise, help reveal the following:
- The length of exercise demonstrates physical tolerance and conditioning.
- Extreme and inappropriate shortness of breath, chest discomfort, dizziness and unexpected weakness may suggest underlying heart disease.
- The blood pressure is recorded at intervals during stress (in the beginning and usually at three minute intervals, if stable). It may be checked more frequently if the patient's blood pressure response to exercise is abnormal.
- High blood pressure during exercise may provide an early clue or indication about this problem. Normally, the systolic (upper reading) blood pressure may rise up to 200 during extreme or peak exercise, while the diastolic (lower reading) remains below 90. Patients with inadequately controlled high blood pressure usually display high diastolic readings during exercise.
- A drop in blood pressure during exercise may indicate heart disease.
- Exercise may provoke arrhythmias (pronounced a-rhyth-me-yaz) or irregular heart rhythm which may not be seen at rest and may or may not point to heart disease.
- The EKG is constantly monitored during exercise and recorded on paper at intervals (usually every minute) and compared to the EKG obtained at rest. Changes in the ST segment and T waves may indicate heart disease.
The RISK of cardiac stress testing is very small. However, since it is carried out in patients with known or suspected heart disease, almost every lab is also equipped with emergency cardiac drugs and resuscitative equipment. It is emphasized that these are precautionary measures that are rarely needed.
