More information is required to definitively evaluate an ST depression from an EKG.
From my stress test 3 years ago, the report states, "patient had a 1 mm ST segment depression"...and my test was stopped after 4 minutes 20 seconds at 7.2 METs. It was/is known I have occluded coronary vessels and the depressed ST segment is the result of deprived oxygen-rich blood to a portion of the heart.
An EKG almost always requires other clinical evidence for a dx, but some perspective Intermediate risk members as it pertains to my previous conditrion of heart failure and occluded vessels:
Exercise test limited to 6-9 METS; or Ischemic ECG response to exercise of less than 2 mm of ST depression; or uncomplicated myocardial infarction, coronary artery bypass surgery, or angioplasty and has a post-cardiac event maximal functional capacity of 8 METS or less on ECG exercise test.
Exercise test limited to less than or equal to 5 metabolic equivalents (METS); or
Marked exercise-induced ischemia, as indicated by either anginal pain or 2 mm or more ST depression by ECG; or severely depressed left ventricular function (ejection fraction less than 30 %); or resting complex ventricular arrhythmia; or ventricular arrhythmia appearing or increasing with exercise or occurring in the recovery phase of stress testing; or decrease in systolic blood pressure of 15 mm Hg or more with exercise; or recent myocardial infarction (less than 6 months) which was complicated by serious ventricular arrhythmia, cardiogenic shock or congestive heart failure; or
survivor of sudden cardiac arrest.
As shown there requires other evidence than just ST segment depression. If you successfully completed the test at 9 METS or higher, that would/ should indicate a healthy cardiovascular system.
The criteria in my prior post is a Bruce protocol based stress test..
Standard stress test can be highly UNDIAGNOSTIC. I had one and achieved a METS of 10.1 with no abnormalities in EKG shown however an angiogram revealed an RCA 95% occluded. Get the gold standard, get an angiogram.
Didn't you have angina, SOB? You must have had symptoms and/or other signs otherwise what would be the reason for an interventional procedure? Frequently, an EKG can be false positive, but a false negative seems to me to be unlikely...apparently possible based on your experience.
The reason for a false positive has to do with artefacts produced by chemical interaction (medication, drugs, electrolyte deficency), etc. and other artificial means that can influence the nartural state of electrogram complexes.. Also there can be motion and noise artefacts that can disturb the EKG signal and EKG equipment may not be properly calibrated or have maladaptive filtering algorithms. Technician error and improperly placed electrodes, etc.
Nope never any angina or shortness of breath.. I had a atrial arythmia once brought on by extreme exertion and that started the process of investigation.
Google it up. Actually it's not at all uncommon to pass standard stress tests only to have a problem later discovered with one of the more extensive tests. (ie. SPECT analysis, angiogram etc.)
My response to the original post is based on treadmill-ECG testing and nuclear perfusion with standard Bruce protocol and is based on the following. Exercise will be continued until one or more of the following end points was reached:
1) one or more ECG leads demonstrated >0.1 mV of flat or downsloping ST-segment depression consistent with ischemia;
2) achievement of greater than 85% of maximum predicted heart rate;
3) inability of the patient to continue to exercise because of fatigue, dyspnea or chest pain;
4) failure of systolic blood pressure to increase 120 mm Hg or a sustained decrease in systolic blood pressure 10 mm Hg or a decrease to below the systolic blood pressure obtained prior to exercise;
or 5) significant arrhythmias. You had arrhythmia.
A positive test was defined as >0.1 mV of flat or downsloping ST-segment depression 0.08 s from the J point,(( >0.01 mV ST-segment elevation in a non-Q-wave lead or the development of anginal chest pain.... You had no pain!
"In addition, approximately 10% of symptomatic (you had no symptims?) patients with obstructive CAD by angiography have a negative electrocardiographic response to exercise The addition of myocardial imaging agents such as technetium improves the sensitivity and specificity, but substantially increases the cost and prolongs the time required for testing".
Electrical blind spots may account for this in some of these patients and other possibilities listed in my other post.and . episodes of ischemia in focal myocardial segments may be missed by the conventional stress test lead system (electrode misplacement, machine not properly calibrated etc.). Cancellation of ST segment vectors arising from two parallel simultaneous ischemic segments (noise and movement) is known to play a role in the normalization of ST segment during stress.
An abnormal EKG at REST, which may be due to abnormal serum electrolytes, abnormal cardiac electrical conduction, or certain medications, such as digitalis;
Heart conditions not related to CAD, such as mitral valve prolapse or hypertrophy (increased size) of the heart; or an inadequate increase in the heart rate and/or blood pressure during exercise.
I'm not persuaded If a coronary arterial blockage results in decreased blood flow to a part of the heart during exercise, and no certain changes are observed in the EKG, as well as in the response of the heart rate and blood pressure.
The accuracy of the stress test in predicting significant coronary artery disease (CAD) depends in part on the "pre-test likelihood" of CAD (also known as Bayes' theorem). In a patient at high risk for CAD (for example, because of advanced age or multiple coronary risk factors), an abnormal stress test is quite accurate (over 90% accurate or approximately 10% false negative) in predicting the presence of CAD. I agree a relatively normal stress test may not mean there is an absence of significant coronary artery disease in a patient with the same high risk factors ( "false negative") stress test.... In a patient at low risk for CAD, a normal stress test is quite accurate (OVER 90%). By adding a nuclear perfusion study to the stress test, this limitation is minimized, and the diagnostic functionality of the stress test is greatly improved.