The South African Flag Sign: An Electrocardiographic Flag for All Coronary Territories?

Abstract

The South African flag sign (SAFS) is an acute, dynamic electrocardiographic (ECG) finding typically associated with first diagonal (D₁) artery occlusion. We report the case of a 47-year-old woman who exhibited this pattern but subsequently revealed the dreaded “widow-maker” lesion (100% occluded proximal left anterior descending [LAD] artery) and severe multivessel disease (90% stenosis of the posterior left ventricular [PLV] artery and 80% stenosis of the left circumflex artery [LCx]).

Introduction

The electrocardiogram (ECG) is a pivotal diagnostic test that provides crucial information to the clinician. It is instrumental in evaluating patients with suspected acute coronary syndromes (ACS) and can reliably predict salient characteristics of coronary artery stenoses. It can also potentially estimate the amount of jeopardized myocardium. ¹

The South African flag sign (SAFS) refers to a specific pattern on a 12-lead ECG, displayed in a “4 × 3” lead format, where there is ST-segment elevation (STE) in leads I, aVL, V₂, and ST-segment depression in lead III. It is typically reflective of “high lateral” myocardial infarction (MI) due to the occlusion of the first diagonal (D₁) branch of the left anterior descending (LAD) coronary artery.^2,3

We describe the case of a 47-year-old woman who exhibited this pattern but subsequently revealed the dreaded “widow-maker” lesion (100% occluded proximal LAD artery) and severe multivessel disease (90% stenosis of the posterior left ventricular [PLV] artery and 80% stenosis of the left circumflex artery [LCx]).

Case Report

A 47-year-old Caribbean-black woman with a significant medical history of breast cancer in remission (2021) status post chemotherapy and radiotherapy presented to the emergency department with unstable angina. She was not previously diagnosed with conventional cardiovascular risk factors such as hypertension, diabetes, or dyslipidemia. She was a lifelong nonsmoker with no family history of premature coronary artery disease. She had no prior coronavirus-2019 (COVID-19) infection and was fully vaccinated.

Her vital signs on presentation revealed a blood pressure of 144/92 mm Hg, heart rate of 116 beats per minute and regular, with pulse oximetry of 97% on ambient air, temperature of 36.3 °C, and body mass index of 31.3 kg/m². On physical examination, she was neurologically intact without any overt abnormalities on the cardiopulmonary component. An emergent 12-lead ECG revealed sinus tachycardia with 3-mm STE in leads I, aVL, and V₂ with ST-segment depression (STD) in lead III (Figure 1). She was immediately administered an ACS protocol with aspirin, ticagrelor, and atorvastatin and proceeded directly to the cardiac catheterization laboratory (Allura Xper FD20; Philips Healthcare, Amsterdam, the Netherlands) for primary percutaneous coronary intervention.

Figure 1.

The patient’s 12-lead electrocardiogram (ECG): (A) The patient’s baseline 12-lead ECG with the subtle SAFS—challenging to interpret or recognize without the South African flag overlay. There is 3-mm ST-segment elevation in leads I, aVL, and V₂, with ST-segment depression in lead III. (B) The patient’s 12 lead ECG was superimposed over the South African national flag. The pattern of ST-segment elevation in leads I, aVL, and V₂ with ST-segment depression in leads III coincides with the green stripe on the flag (green triangles and yellow triangles, respectively).

Coronary cineangiography revealed a 100% occlusion of the proximal LAD artery, 90% stenosis of the PLV artery and 80% stenosis of the LCx (Figure 2). She successfully underwent PCI with a drug-eluting stent (Synergy Boston Scientific Corporation, Marlborough, Massachusetts) to her culprit lesion—the proximal LAD occlusion with an excellent angiographic result without complications. A bedside 2-dimensional transthoracic echocardiogram revealed a mild anterior hypokinesis with an estimated left ventricular ejection fraction of 40% to 45%. She was initiated on neurohormonal heart failure with reduced ejection fraction therapy with valsartan/sacubitril, carvedilol/ivabradine, eplerenone, and empagliflozin. There were no serious adverse events during her ensuing 48-hour hospitalization, and she was subsequently discharged with routine outpatient follow-up to discuss comprehensive, guideline-directed medical therapy versus staged PCI of residual CAD.

Figure 2.

The patient’s primary percutaneous coronary intervention (PPCI) series: (A) Left anterior oblique (LAO) cineangiography indicating a middle posterior left ventricular (PLV) artery 90% stenosis—encircled in red. (B) Right anterior oblique (RAO) caudal cineangiography indicating a middle left circumflex artery (LCx) 80% stenosis—encircled in red. (C) Left anterior oblique (LAO) caudal cineangiography indicating a thrombotic left anterior descending (LAD) artery occlusion, the so-called “widow-maker lesion”—encircled in red. (D) Right anterior oblique (RAO) cranial cineangiography indicating the segment which was predilated with a drug-coated balloon (DCB) and subsequently stented with a drug-eluting stent (DES) with an excellent angiographic result without complications—encircled in red. (E) Straight cranial cineangiography indicating a now patent left anterior descending (LAD) artery with Thrombolysis in Myocardial Infarction (TIMI) III antegrade flow and no evidence of perforation or dissection—encircled in red.

Discussion

The ECG is a decisive tool in the early identification of the culprit vessel in ACS and can guide key management strategies such as revascularization. ⁴ Studies have shown that lesions at different sites along the LAD demonstrate various characteristic ECG patterns. Two decades ago, Peter Zimetbaum and Mark Josephson suggested that STE of leads V₁, V₂, V₃, and aVL with associated STD of more than 1 mm in aVF is associated with proximal occlusion of the LAD. ⁴ In 2008, de Winter et al ⁵ also described an ECG pattern suggestive of acute proximal LAD occlusion, characterized by STD at the J point in leads V₁-V₆ with upsloping ST-segments leading to tall-positive symmetrical T-waves with concurrent STE in aVR in most patients. Wellens syndrome was initially described in 1982 by de Zwaan et al^6,7 in patients with unstable angina, which ascertained a correlation with significant proximal LAD disease. Wellens syndrome is subdivided into type A or type B; the former is typified by biphasic T-wave in leads V₂ and V₃, and the latter is characterized by deep T-wave inversion in the same leads. ⁸

The STE in 2 noncontiguous leads, aVL and V₂, was previously described as associated with occlusion of the D₁ branch.^9,10 In 2015, Durant et al ² reported an ECG pattern of STE in leads I, aVL, and V₂, with STD in the inferior leads being associated with occlusion of the D₁ artery. The patient described had no residual, obstructive CAD within the LAD artery. Later that year, Littman coined the term “South African flag sign” as a visual mnemonic or aid for this ECG pattern to facilitate earlier detection of “high lateral” MI due to D₁-LAD occlusion.^3,11 Traditionally, as V₂ is noncontiguous with I and aVL, STE in these leads can be misinterpreted as a “lateral wall” MI due to the occlusion of the LCx. The STD in leads III and aVF can also be misinterpreted as inferior ischemia due to the obfuscation of STE in mirror image leads.^3,12 This term was used as the South African national flag contains a green horizontal “Y” that parallels the ST-segment changes. In a 12-lead ECG, displayed in a conventional 4 × 3 format, leads I and III coincide with the upper and lower angled limbs of the horizontal “Y,” and the main, straight horizontal limb coincides with V₂ and aVL. ³ Since its initial description in 2015, other cases of D₁ artery occlusion using this sign have been reported.^11,12

Our patient presented with the SAFS on ECG; however, coronary angiography revealed the dreaded “widow-maker” lesion with multivessel coronary artery disease (MVD). ¹³ This case is novel and unique as these associations have not been previously described, and it is essential not to attribute SAFS to “high lateral wall” MI solely. This lesion is particularly distressing to the patient and heart team as it hinders perfusion to a large segment of viable myocardium and is life-threatening.^13,14 Women with STE-ACS have worse major adverse cardiovascular events, including mortality than men, attributed to older age, worse cardiovascular risk profiles, delayed GDMT, reperfusion, revascularization therapies, and different mechanisms in ACS pathophysiology. ¹⁵ As such, the term should be strongly reconsidered or even rendered obsolete in the lexicon due to its implicit bias and neglect of the current crisis of cardiovascular disease in women.

Conclusion

We report the case of a 47-year-old woman who exhibited this pattern but subsequently revealed a completely occluded proximal LAD artery) and severe multivessel disease (90% stenosis of the PLV artery and 80% stenosis of the LCx). The clinician should be aware that the South African flag ECG sign (SAFS) is not only reflective or pathognomonic of “high lateral” MI but may include other coronary territories, such as proximal LAD artery occlusion or even MVD.