What question did this study set out to answer?

To highlight the significance of the shark fin pattern on electrocardiograms as an indicator of serious cardiac conditions.

March 22, 2026Open Access

Recognizing the Shark Fin Pattern: An Ominous Electrocardiographic Diagnosis

Key Result

The shark fin electrocardiographic pattern in antero-lateral leads strongly suggests left main coronary occlusion and indicates high risk of ventricular fibrillation and mortality.

Key Points

To highlight the significance of the shark fin pattern on electrocardiograms as an indicator of serious cardiac conditions.
Patient presented with acute chest pain and examination revealing hypotension and tachycardia.
ECG recorded showing shark fin pattern with ST-segment elevation in specific leads.
Immediate coronary angiography performed following initial medical management.
Complete thrombotic occlusion of the left main coronary artery observed.
Initial TIMI I flow achieved after balloon dilatation but improved with intracoronary vasodilators.
Patient's left ventricular ejection fraction improved from 25% to 40% at 6-month follow-up.

Structured PICO

Population

1 middle-aged male in his 40s presenting with acute-onset chest pain of 6 hours duration, cardiogenic shock, and a 'shark fin' electrocardiographic pattern.

Intervention

Urgent coronary angiography and percutaneous coronary intervention with two overlapping drug-eluting stents from the left main coronary artery to the mid left anterior descending artery, along with antiplatelets, statin, and inotropic support.

The 'shark fin' ECG pattern is an ominous sign indicating a large myocardial territory at risk, such as left main coronary occlusion, and requires early recognition and urgent intervention.

Main Result

Absolute Event Rate: 0% vs 0%

Abstract

A middle-aged male in his 40s presented to our emergency department with acute-onset chest pain of 6 h duration. On examination, he was hypotensive with blood pressure of 80/50 mm Hg, tachycardic, and had bilateral basal crepitations. A 12-lead electrocardiogram showed a “shark fin” or “triangular” pattern (fusion of QRS complexes with ST segment and T wave), with ST-segment elevation in the anterior chest leads (V2–V4) and lateral leads (I and aVL augmented vector left) Figure 1a. Transthoracic echocardiography revealed anterior wall hypokinesia with a left ventricular ejection fraction of 25%.Figure 1: (a) Showing 12 lead electrocardiogram with ST segment elevation with shark fin appearance from V2-V4 and I, aVL. (b) Depicting coronary angiogram of the left coronary system in the left anterior oblique caudal view showing complete thrombotic occlusion of the left main coronary artery. (c) Showing poor distal perfusion after balloon dilatation of the lesion. (d) Demonstrates good flow in both left anterior descending and circumflex arteries after deployment of 2 drug eluting stentsAfter loading with antiplatelets, statin, and initiating inotropic support, the patient underwent urgent coronary angiography which revealed complete thrombotic occlusion of the left main coronary artery Figure 1b. Despite multiple balloon dilatations, only TIMI I flow could initially be achieved Figure 1c. Intracoronary vasodilators improved the flow and two overlapping drug-eluting stents were deployed from the shaft of the left main artery to the mid left anterior descending (LAD) artery with good result Figure 1d. The patient remained well at a 6-month follow-up, with recovery of left ventricular ejection fraction to 40%. The shark fin pattern is an ominous electrocardiographic marker and reflects a large myocardial territory at risk due to left main coronary involvement or triple-vessel disease and indicates increased risk of ventricular fibrillation and in-hospital mortality.1 It is interesting to note that there are subtle differences between the tombstoning pattern (short R-wave duration, large amplitude convex ST-segment elevation which is greater than R-wave height, and ST-segment fusion with ascending limb of T-wave) and triangular wave form and lambda wave form patterns (both of these patterns have very prominent R waves with merging of QRS complexes and descending limb of T waves, but lambda wave form has a distinct J point which differentiates it from triangular wave form). In our case, the presence of new onset right bundle branch block (RBBB) and ST elevations in the anterior precordial leads point to proximal LAD involvement as the right bundle is supplied by the first septal perforator of the LAD.2 However, there is conspicuous absence of ST elevation in V1 and (aVR) augmented vector right which is atypical of proximal LAD involvement. This ECG finding can be explained by the concurrent left circumflex (LCX) involvement when the left main coronary is occluded, and the reciprocal ST depression caused due to LCX involvement nullifies the ST elevation expected in V1 and aVR due to proximal LAD involvement.2 To summarize, shark fin ST elevation in antero-lateral leads with new-onset RBBB and lack of ST elevation in V1 and aVR strongly suggests left main coronary involvement.2 Early recognition of this pattern and timely use of mechanical circulatory support may improve the outcomes in such patients.1 Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.