Use of the 12-Lead Electrocardiogram in Risk Assessment and in Selecting Thrombectomy for ST-Elevation Myocardial Infarction

Joonas Leivo

Research output: Book/ReportDoctoral thesisCollection of Articles

Abstract

Different tools have been proposed for risk assessment in ST-elevation myocardial infarction, but they may not be optimally implemented in clinical practice. The Global Registry of Acute Coronary Events (GRACE) score is a recommended tool for assessing the risk of an adverse outcome in patients with STEMI. The GRACE score, however, utilizes only one crude ECG finding, ST elevation (STE), while it has been shown that the use of the ECG in the risk assessment of patients with a STEMI extends beyond STE. Along with STE, ECG findings contributing to an adverse outcome include pathological Q waves, T wave inversion (TWI) and the grade of ischemia (GI). STEMI patients can be stratified into different temporal stages with the use of Q waves and TWI. The ECG finding of STE without Q waves and TWI signifies preinfarction syndrome (PIS), and STE with Q waves and/or TWI signifies an evolving myocardial infarction (EMI). An EMI is thought to represent a later stage of the infarction process, and patients with an EMI have a poorer outcome than do patients with PIS. On the other hand, the severity of myocardial ischemia could be assessed from the ECG with different GIs. Grade 1 ischemia (G1I) is considered to be the first sign of myocardial ischemia in an acute total coronary artery occlusion and is defined as a positive, tall and peaked T wave. As the myocardial ischemia progresses, STE becomes evident, constituting G2I, and, finally, in a minority of patients, a distortion of the terminal portion of the QRS complex develops, marking the most severe form, G3I.

Aspiration thrombectomy has been used in conjunction with a primary percutaneous coronary intervention (pPCI) as a treatment for STEMI. Earlier studies indicated a benefit from aspiration thrombectomy in reducing the thrombus burden and preventing distal embolization and the no-reflow phenomenon. The trial of Routine Aspiration Thrombectomy with PCI versus PCI Alone in Patients with STEMI (TOTAL) showed that routine aspiration thrombectomy did not lower the risk of an adverse outcome in the whole STEMI patient population. A safety concern was also raised with reference to the finding of an elevated risk of stroke associated with the use of the technique. Consequently, the current guidelines do not recommend routine use of thrombectomy.

The aims of the current study were to evaluate the prognostic significance of the PIS and EMI findings in an ECG (Study I); to assess the prognostic significance of the G2I and G3I findings in an ECG (Study II); to determine the joint and separate effect of Q waves and TWI on the outcome (Study III); and to determine whether any STEMI patients, as stratified into different risk groups according to Q waves, TWI and GI, would benefit from routine aspiration thrombectomy (Studies I, II and III).

Study I comprised 7,860 patients from the TOTAL trial, who were divided into PIS and EMI groups according to the ECG changes. It was shown that patients with EMI had a higher risk of the primary outcome, defined as a composite of cardiovascular (CV) death, cardiogenic shock, New York Heart Association (NYHA) class IV heart failure (HF), and recurrent MI, when compared to patients with PIS within 1-year follow-up, and the ECG classification (EMI vs PIS) was an independent predictor of an adverse outcome (adjusted HR 1.54; 95% CI 1.30–1.82; p < 0.001). Compared to the GRACE score alone, the EMI and PIS ECG patterns combined with the GRACE score were found to have significant incremental prognostic value. There was no difference in the effect of treatments (thrombectomy vs PCI alone) on the outcome among either EMI or PIS patients.

In study II, 7,211 patients from the TOTAL trial were included in the analysis. The patients were stratified into two groups based on their GI ECG classification (G2I and G3I). During 1-year follow-up, the patients with G3I had a higher risk of a primary outcome compared to the patients with G2I (9.8% vs 6.4%; aHR, 1.27; 95 % CI 1.04–1.55; p = 0.022), but there was no benefit from routine aspiration thrombectomy for either of the patient groups.

Study III enrolled 7,831 patients from the TOTAL trial. The patients were divided into four groups according to the findings of pathological Q waves and TWI: Q-TWI- (no Q waves and no TWI), Q+TWI-, Q-TWI+, and Q+TWI+. Q waves and TWI were also analysed separately. Patients with the Q+TWI+ pattern were at the highest risk of a primary outcome compared to patients with the Q-TWI- pattern, but this was only seen within the time period of 40 days’ follow-up (aHR 2.10; 95% CI 1.45–3.04; p < 0.001). In patients with the Q+TWI- and Q+TWI+ patterns, there was no additive risk of a primary outcome after 40 days of follow-up. In contrast, patients with the Q-TWI+ pattern had a higher risk of a primary outcome than did patients with the Q-TWI- pattern only after 40 days (aHR 1.82; 95% CI 1.06–3.14; p = 0.031). In the separate analysis of Q waves and TWI, patients with Q waves had a higher risk of a primary outcome only within 40 days (aHR 1.80; 95% CI 1.48–2.19; p < 0.001), while patients with TWI had a higher risk of a primary outcome only after 40 days (aHR 1.63; 95% CI 1.04–2.55; p = 0.033). There was no benefit from routine aspiration thrombectomy in any of the Q/TWI patient groups, not even when patients with Q waves and TWI were analysed separately.

In conclusion, risk assessment in patients with a STEMI can be achieved reliably based on the ECG at presentation by analysing the presence of Q waves, TWI and QRS distortion (G3I). The implementation of Q waves and TWI in addition to the GRACE score improves prognostic assessment compared to the GRACE score alone. The routine use of aspiration thrombectomy in conjunction with pPCI does not lower the risk of an adverse outcome even in high-risk subgroup of patients assessed according to the ECG changes. There is currently no effective way outside of the guideline-based therapeutic measures to influence the outcome of STEMI patients who are at the highest risk of an adverse outcome. Future studies should consider an ECG-based risk stratification when assessing potential treatment tailoring for patients with a STEMI.
Original languageEnglish
Place of PublicationTampere
ISBN (Electronic)978-952-03-3361-4
Publication statusPublished - 2024
Publication typeG5 Doctoral dissertation (articles)

Publication series

NameTampere University Dissertations - Tampereen yliopiston väitöskirjat
Volume987
ISSN (Print)2489-9860
ISSN (Electronic)2490-0028

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