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ECG Reciprocal Depression for ACS Decision Support in the COVID-19 Era

New information regarding COVID-19 continues to emerge daily. This content was based on the sources available at the time of writing.

Related Articles: Diagnostic ECG

Patients with COVID-19 often present with signs and symptoms that suggest significant cardiovascular disease. For these patients, COVID-19-related ECG abnormalities—including ST-segment elevation (STE) and depression—can complicate the accurate diagnosis of acute coronary syndrome (ACS).

Given the importance of timely differentiation of myopericarditis due to COVID-19 from a type 1 STEMI, a closer look at ECG changes, including reciprocal depression, is warranted.

Observed RSTD Patterns in Type 1 STEMI

Foundational studies from the 1980s, still referenced today, correlated ECG findings with angiographic findings in patients presenting with STEMI. They identified ST depression occurring in leads remote from the infarct site, so-called reciprocal ST-segment depression (RSTD).

A study in the Journal of the American College of Cardiology found that patients with a first acute STEMI showed RSTD present in 100% of inferior infarctions and 70% of anterior infarctions. Patients who have ST-segment depression or a combination of ST-segment depression and elevation have the highest incidence of cardiac death, re-infarction, and recurrent chest pain, as an article in the Bratislava Medical Journal observes.

Three different explanations for RSTD were proposed early on and have remained a topic of controversy:

  1. RSTD is just an electrophysiological phenomenon in which the observed ST depression is the "rear view " or mirror image of the classic STE.
  2. RSTD is a product of myocardial necrosis or ischemia remote from the infarct site.
  3. RSTD is a result of the extension of the infarct beyond the index site.

A review published in the American Heart Journal suggests patients with RSTD are a heterogeneous group, with coexistent anterior ischemia being present in some. In others, anterior RSTD is a passive reflection of inferior STE, sometimes reflecting either a larger infarct size or more extensive septal or posterolateral involvement. The review also notes that patients with posterolateral wall extension can be identified by the presence of reciprocal depression in the right precordial leads.

These foundational studies indicate that the presence and location of RSTD remain useful in accurate diagnosis of ACS, particularly in inferior myocardial infarctions.

Analyzing RSTD to Determine STE Etiology

Can RSTD help differentiate COVID-19 patients with STE due to STEMI from those with myopericarditis or other nonspecific causes of STE? Earlier studies on patients with STE but without type 1 MI may be useful as a foundation in viewing COVID-19 patients with similar ECG patterns.

A study published prior to COVID-19 in the Scandinavian Cardiovascular Journal examined ECG changes in 85 patients with STEMI and 94 patients with nonischemic STE, with the following findings:

  • Significant RSTD (defined as ≥0.025 mV in lead II) was noted in 40% of the anterior STEMI group but none of the nonischemic anterior STE group (p<.001).
  • RSTD in aVR was not predictive of STEMI as ST depression ≥0.025 mV in aVR was present in 80% of the nonischemic cases but only 30% of STEMI patients (p < .001).
  • RSTD (ST depression ≥0.025 mV in lead I) in patients with inferior STE occurred in 83% of STEMI cases, but in none of the nonischemic cases (p < .001).
  • Multivariate analysis showed RSTD "was the strongest independent predictor of ischemic STE etiology, whereas chest-lead PR depression and ST depression in aVR were associated with a nonischemic etiology."

RSTD has been described in nonspecific causes of STE but can usually be differentiated from ischemic STEMI. According to a paper in the Journal of Electrocardiology, in early repolarization and acute pericarditis, reciprocal changes are commonly seen only in aVR. In patients with left ventricular hypertrophy, cardiomyopathy, and/or LBBB, the characteristic changes are STE in V1-V2 with ST depression in I, aVL, and V5-V6.

Characteristics of RSTD in COVID-19 Patients

What have we learned about RSTD in COVID-19 patients who present with STE?

A case series of eighteen patients presenting with cardiac enzyme evidence for myocardial injury and STE published in the New England Journal of Medicine provides insights into the management of COVID-19 patients with potential acute coronary syndrome. Half of these patients underwent coronary angiography, and two-thirds of those studied invasively were believed to have had obstructive coronary disease.

The 12-lead ECG on all eighteen patients can be viewed in the supplementary appendix along with still frames from the coronary angiograms. Five patients underwent percutaneous coronary intervention. After review of all clinical information, 8/18 were believed to have MI (STEMI group) and 10/18 to have "noncoronary" myocardial injury (NCMI group).

A review of the published ECGs for these patients shows RSTD present in 7 of the 8 STEMI patients (87.5%), versus only 4 of the 10 (40%) NCMI patients.

The ECG below was from a STEMI patient found to have 100% RCA at angiography. The RSTD is quite significant in both leads I and aVL, consistent with STEMI etiology.

ECG Reciprocal Depression - Image 1.jpeg

The ECG below is from a NCMI COVID-19 patient who underwent urgent catheterization on presentation with STE. The RSTD is prominent in lead aVR, with only subtle up-sloping ST depression in leads III, aVF, and V1.

ECG Reciprocal Depression - Image 2.jpeg

Overall Value of RSTD

Differentiating type 1, plaque rupture STEMI from other myocardial complications of COVID-19 is essential. Informed ECG interpretation can provide important contributions to the rapid triage of patients to angiography when appropriate. The presence of RSTD in leads other than aVR is a helpful marker for patients who would benefit from early revascularization.

In this regard, it should be noted that UpToDate has recommended performing a 12-lead ECG at the time of entry into the hospital for patients in whom COVID-19 is suspected to allow for "documenting baseline QRS-T morphology should the patient develop signs/symptoms suggestive of myocarditis or an acute coronary syndrome," underscoring the importance of ECG for timely diagnostic insights.