The 24-lead ECG display for enhanced recognition of STEMI-equivalent patterns in the 12-lead ECG

In a patient with chest pain and suspected acute coronary syndrome, the electrocardiogram (ECG) is the only readily available diagnostic tool. It is important to maximize its usefulness to detect acute myocardial ischemia that may evolve to myocardial infarction unless the patient is treated expediently with reperfusion therapy. Since diagnostic guidelines have usually included only ST-elevation myocardial infarction (STEMI) as the entity that should be diagnosed and treated urgently, a patient with coronary occlusion represented on ECG as ST depression is likely not to be considered a candidate for receiving immediate coronary angiography and coronary intervention. ECG criteria for STEMI detection require that ST elevation meet predetermined millivolt thresholds and appear in at least two spatially contiguous ECG leads. The typical ECG reader recognizes only three contiguous pairs: aVL and I; II and aVF; aVF and III. However, viewing the “orderly sequenced” 12-lead ECG display, two more contiguous pairs become obvious in the frontal plane: + I and − aVR; − aVR and + II. The 24-lead ECG is a display of the standard 12-lead ECG as both the classical positive leads and their negative (inverted) counterparts. Leads + V1, + V2, + V3, + V4, + V5, and + V6 and their inverted counterparts are used to generate a “clock-face display” for the transverse plane. Similarly, + aVL, + I, − aVR, + II, + aVF, + III in the frontal plane and their inverted counterparts are used to generate a clock-face display for the frontal plane. Optimum results, 78% sensitivity and 93% specificity, were obtained using the following 19 ECG leads: frontal plane: + aVR, − III, + aVL, + I, − aVR, + II, + aVF, + III, − aVL; transverse plane: + V1, + V2, + V3, + V4, + V5, + V6, − V1, − V2, − V3.