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Case Reports
. 2025 Mar 30;17(3):e81468.
doi: 10.7759/cureus.81468. eCollection 2025 Mar.

The South African Flag Sign: A Key Indicator of Acute D1 Occlusion

Johannes Luckmann  1 , Soe Win  2 , Temitope Ajagbe  3 , Thisara Samarawickrama  2
Affiliations
Case Reports

The South African Flag Sign: A Key Indicator of Acute D1 Occlusion

Johannes Luckmann et al. Cureus. .

Abstract

The South African flag sign (SAFS) on an ECG suggests an occlusion in the first diagonal branch of the left anterior descending (LAD) coronary artery, particularly in the context of acute chest pain. Due to its unique findings, it is often overlooked or misidentified. We present four cases in which this finding was identified on ECG, along with the corresponding angiographic images and clinical details. Two of these had an acute diagonal branch occlusion, which was treated with stent insertion. The other two cases had some angiographic changes but had no stent inserted. All of these cases showed a varying degree of left ventricular dysfunction and troponin rise, highlighting the importance of recognition and prompt management. On subsequent cardiac MRI, one patient was determined to have an aborted infarct, and another was suspected of the same. The urgency with which the SAFS should be expedited to invasive imaging should match that of other acute signs of occlusion, such as the new left bundle branch block (LBBB) in the context of chest pain. Increased awareness of the SAFS can prevent these cases from being overlooked and improve patient outcomes by ensuring they receive timely care.

Keywords: acute coronary syndrome; d1 occlusion; ecg patterns; interventional cardiologist; south african flag sign.

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Conflict of interest statement

Human subjects: Consent for treatment and open access publication was obtained or waived by all participants in this study. Conflicts of interest: In compliance with the ICMJE uniform disclosure form, all authors declare the following: Payment/services info: All authors have declared that no financial support was received from any organization for the submitted work. Financial relationships: All authors have declared that they have no financial relationships at present or within the previous three years with any organizations that might have an interest in the submitted work. Other relationships: All authors have declared that there are no other relationships or activities that could appear to have influenced the submitted work.

Figures

Figure 1
Figure 1. a) ECG of Patient 1 superimposed with the South African flag. b) The same ECG showing ST elevation in leads I, aVL, and V2, and ST depression in lead III. These changes align with the green band of the South African flag, providing a classic yet subtle example of SAFS.
SAFS, South African flag syndrome; ECG, electrocardiogram
Figure 2
Figure 2. ICA images of Patient 1, showing 40-50% obstruction in D1.
ICA, invasive coronary angiogram
Figure 3
Figure 3. ECG of Patient 2 showing ST elevation in leads I, aVL, and V2, along with ST depression in lead III, highlighted by the arrows, the SAFS.
SAFS, South African flag sign; ECG, electrocardiogram
Figure 4
Figure 4. ICA images of Patient 2 revealing severe disease in the LAD and D1, as well as an image post-stent insertion. The occlusion in this case was diagnosed through the identification of the SAFS, highlighting its diagnostic potential.
ICA, invasive coronary angiogram; SAFS, South African flag sign
Figure 5
Figure 5. ECG of Patient 3 showing ST elevation in leads I, aVL, and V2, along with ST depression in lead III, highlighted by the arrows, the SAFS.
SAFS, South African flag sign; ECG, electrocardiogram
Figure 6
Figure 6. ICA images showing severe stenosis of the LAD and complete occlusion of D1 in the context of SAFS. Subsequent images demonstrate stent insertion into the aforementioned vessels.
ICA, invasive coronary angiogram; SAFS, South African flag sign; LAD, left anterior descending
Figure 7
Figure 7. a) ECG of Patient 4 showing ST elevation in leads I, aVL, and V2, along with ST depression in lead III, highlighted by the arrows, the SAFS. b) ICA images show unimpaired D1 flow, highlighting the low specificity of the SAFS, as not all who exhibit the sign have acute occlusions in D1.
ICA, invasive coronary angiogram; SAFS, South African flag sign; ECG, electrocardiograms
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References

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