ECG Quiz Answer
Chest Pain and a 'Normal' Exercise ECG in a 44-Year-Old Runner
John D. Cantwell, MD
THE PHYSICIAN AND SPORTSMEDICINE - VOL 26 - NO. 9 - SEPTEMBER 98
Because the patient continued to have chest pain, his internist obtained a CT scan of the chest that showed an enlarged thoracic aorta with no evidence of aortic dissection.
Cardiac catheterization demonstrated a 90% occlusion of the proximal left anterior descending (LAD) artery. The distal LAD and the second diagonal branch exhibited retrograde filling from collaterals of the right coronary artery. The aortic root was mildly dilated.
The patient underwent angioplasty of the LAD lesion and placement of a stent, and he tolerated the procedures well.
Reading the Signs
Three factors in this case pointed to the likelihood of significant coronary artery disease: the persisting chest pain, the exercise ECG, and the blood pressure response to exercise. Chest pain resembling angina pectoris during treadmill testing should always raise the suspicion of underlying coronary disease, even when the treadmill ECG appears to be normal.
Though this patient's exercise ECG was interpreted as normal, this was not in fact the case (figure 3). Two important clues to a significant proximal LAD lesion were ST-segment elevation in the anterior precordial leads and left axis deviation that developed during or after the test (1,2).
ST-segment elevation in leads without pathologic Q waves tends to be vessel specific; elevations in leads V1 through V3 likely imply an LAD lesion. (This contrasts with ST-segment depression with exercise, which has poor correlation between the ECG leads involved and the artery implicated; ST depression in the inferior leads could reflect an LAD lesion.) It's important to be sure that ST elevations are not just early repolarization, a common finding in normal athletes, seen at rest and during or immediately after exercise (figure 4).
Another subtle clue to an LAD lesion, inversion of U waves with exercise, was not observed in this patient (3).
In addition to the subtle ECG signs, the patient had exercise-induced hypotension. This is diagnosed when the systolic blood pressure falls 20 mm Hg or more after an initial rise, even if it doesn't drop below the standing baseline reading. This usually implies underlying myocardial ischemia and is a marker for an increased risk of cardiac events over the next 2 years (4).
The EBCT scan in this case, with a calcium score of 19.2 and mild amount of calcium seen in the LAD coronary artery, suggested only mild coronary artery disease (CAD) (mild, one-vessel CAD, calcium score, 1-20; moderate one- to three-vessel CAD, 20-150; extensive two- to four-vessel CAD, greater than 150). This tool can underestimate or miss disease in younger patients who have single-vessel lesions and risk factors such as cigarette smoking and diabetes mellitus (5). (See "A New Cardiac Test for an Older Doctor," June, page 87.)
Dr Cantwell is a cardiologist at Cardiology of Georgia, PC, and clinical professor of medicine at Morehouse School of Medicine, both in Atlanta. He is an editorial board member of The Physician and Sportsmedicine. Address correspondence to John D. Cantwell, MD, Cardiology of Georgia, PC, 95 Collier Rd NW, Suite 2075, Atlanta, GA 30309.
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