A 74-year-old female with a past medical history of hypertension, diabetes, hyperlipidemia, and tobacco use disorder presents with chest discomfort and indigestion ongoing for the past 2 weeks. She reports radiation to the jaw and left upper extremity. Recently, she has been feeling short of breath and has experienced some exercise intolerance, limiting her mobility to just half a block, which she partially attributes to her osteoarthritis. She has been compliant with her home medications, which include antihypertensives, metformin, and a statin. On presentation at rest, her pain is less than it has been in the last couple weeks but is still present. An ECG is obtained (Figure 1).
Interpretation
Rate: 75 bpm; Rhythm: Normal sinus rhythm; Axis: Normal axis, most positive in I and AVL; Intervals: PR normal; QRS: Q waves in III; QRS duration: Normal; ST Segment/ T-Waves: T wave inversions in III, AVF.
A point-of-care (POCUS) echocardiogram performed by the emergency physician at bedside demonstrated a grossly normal systolic function with an apparent regional wall motion abnormality (RWMA; highlighted in yellow) with hypokinesis of the infero-septal posterior wall (Figure 2). No pericardial effusion or signs of right heart strain are noted, and the size of the inferior vena cava (IVC) is in an indeterminate range.
Figure 2. POCUS image with RWMA highlighted in yellow.
As labs begin to result, they demonstrate a point-of-care troponin of 0.306 and troponin-I of 0.384. Thus, a repeat ECG is obtained (Figure 3).
Figure 3. Repeat ECG obtained at 11:15 AM.
Interpretation
Rate: 85 bpm; Rhythm: Normal sinus rhythm. Axis: Normal axis, most positive in I and AVL; Intervals: PR normal; QRS: Q wave now present in both III and AVF; QRS duration: Normal; ST Segment/ T-Waves: More coved appearance of mildly elevated ST segment of III and AVF, still with persistent T wave inversions, and depressed ST segments in V2-V3, 1-mm ST-depression in V6 and sub-1-mm concave depression in AVL.
In this case, this patient’s ECG findings were by no means obvious for an occlusive myocardial infarction (OMI). However, when taken in conjunction with the patient’s risk factors, history, positive troponin, and RWMA on POCUS echocardiogram, these findings yield high suspicion for NSTEMI secondary to a true OMI. Cardiology was consulted urgently, evaluated the patient at bedside, and reviewed the POCUS and ECG findings. They agreed that these symptoms were likely secondary to occlusive cardiac ischemia. The patient was admitted to the Cardiac ICU and taken for a left heart catheterization procedure. The catheterization findings were notable for 90-99% stenosis of the mid right coronary artery (RCA), and the patient had a single drug-eluting stent placed. A comprehensive transthoracic echocardiogram (TTE) noted a similar hypokinesis of the basal mid inferior and inferoseptal myocardium. The patient was discharged two days after admission on dual antiplatelet therapy with outpatient Cardiology follow-up scheduled.
Expected findings in incomplete RCA stenosis:
ST elevation in the inferior leads (II, III, AVF)
Reciprocal ST depression in the lateral leads (1, aVL)
ST depression in V2, signifying posterior wall involvement
T wave inversions in inferior leads if occlusion spontaneously re-opened
Note that an RCA occlusion can be very subtle on ECG and does not always meet criteria for a STEMI
Take Away Points:
Always take ECG findings in the context of the clinical case and other diagnostic tools at your disposal.
If you think you see a RWMA, particularly in a patient with a positive troponin and active chest pain, get Cardiology involved early, as they may elect for quicker intervention.
Authored by Lucas Ferreira, MD and Ari Edelheit, MD.
References:
Grauer, Ken. A Practical Guide to ECG Interpretation. Second Edition. Mosby 1998.