ABC | Volume 112, Nº1, January 2019

Original Article Regional QT Interval Dispersion as an Early Predictor of Reperfusion in Patients with Acute Myocardial Infarction after Fibrinolytic Therapy Gabriel Dotta, Francisco Antonio Helfenstein Fonseca, Maria Cristina de Oliveira Izar, Marco Tulio de Souza, Flavio Tocci Moreira, Luiz Fernando Muniz Pinheiro, Adriano Henrique Pereira Barbosa, Adriano Mendes Caixeta, Rui Manoel Santos Póvoa, Antônio Carlos Carvalho, Henrique Tria Bianco Universidade Federal de São Paulo, São Paulo, SP – Brazil Mailing Address: Henrique Tria Bianco • Disciplina de Cardiologia -Universidade Federal de São Paulo - Rua Loefgren, 1350. Postal Code 04040-001, Vila Clementino, São Paulo, SP - Brazil Email: henriquetria@uol.com.br Manuscript received February 10, 2018, revised manuscript July 13, 2018, accepted August 02, 2018 DOI: 10.5935/abc.20180239 Abstract Background: Patients with ST-elevation acute myocardial infarction attending primary care centers, treated with pharmaco- invasive strategy, are submitted to coronary angiography within 2-24 hours of fibrinolytic treatment. In this context, the knowledge about biomarkers of reperfusion, such as 50% ST-segment resolution is crucial. Objective: To evaluate the performance of QT interval dispersion in addition to other classical criteria, as an early marker of reperfusion after thrombolytic therapy. Methods: Observational study including 104 patients treated with tenecteplase (TNK), referred for a tertiary hospital. Electrocardiographic analysis consisted of measurements of the QT interval and QT dispersion in the 12 leads or in the ST-segment elevation area prior to and 60 minutes after TNK administration. All patients underwent angiography, with determination of TIMI flow and Blush grade in the culprit artery. P-values < 0.05 were considered statistically significant. Results: We found an increase in regional dispersion of the QT interval, corrected for heart rate (regional QTcD) 60 minutes after thrombolysis (p = 0.06) in anterior wall infarction in patients with TIMI flow 3 and Blush grade 3 [T3B3(+)]. When regional QTcD was added to the electrocardiographic criteria for reperfusion (i.e., > 50% ST-segment resolution), the area under the curve increased to 0.87 [(0.78-0.96). 95% IC. p < 0.001] in patients with coronary flow of T3B3(+). In patients with ST‑segment resolution >50% and regional QTcD> 13 ms, we found a 93% sensitivity and 71% specificity for reperfusion in T3B3(+), and 6% of patients with successful reperfusion were reclassified. Conclusion: Our data suggest that regional QTcD is a promising non-invasive instrument for detection of reperfusion in the culprit artery 60 minutes after thrombolysis. (Arq Bras Cardiol. 2019; 112(1):20-29) Keywords: ST Elevation Myocardial Infarction; Electrocardiography; Myocardial Reperfusion; Percutaneous Coronary Intervention; Biomarkers. Introduction Despite advances in its treatment, acute myocardial infarction (AMI) rates are still high. In this regard, reperfusion of the culprit artery has become the main objective of ST‑elevation acute myocardial infarction (STEMI) treatment. Early reperfusion with preservation of arterial permeability is responsible for mortality reduction in the acute phase, and in medium and long term. 1,2 Nevertheless, once arterial flow is reestablished, myocardial stunning is not resolved due to the injury-reperfusion process. 3,4 Primary percutaneous coronary intervention (PCI) is considered the gold standard for the treatment of STEMI. 5 Nevertheless, when PCI is not available or cannot be performed in a timely manner, pharmaco-invasive strategy (PIS) is an alternative for reperfusion, consisted of intravenous fibrinolysis, conducted in primary or prehospital care. 6-8 Classical criteria for reperfusion include improvement of ischemic symptoms and ST-segment resolution (> 50% in the highest lead within 60–90 min of fibrinolytic administration). 9,10 There is some controversy about the behavior of the heart rate-corrected QT interval (QTc) after STEMI. While some studies have reported an increase in QTc in the acute phase followed by its decrease after reperfusion, others reported increased QTc, which was associated with non-reperfusion. 11,12 QTc dispersion (QTcD) was reduced in patients with successful fibrinolytic therapy and decreased in non-revascularized patients. A reduction in QTcD after fibrinolysis was predictive of coronary reperfusion. 13 There is evidence that recanalization after an acute event is associated with a decrease in QTcD, as observed in the TEAM-2 and TEAM-3 studies. 14,15 To our knowledge, there is no study on QTcD after PIS combined with angiographic perfusion imaging (TIMI flow and Blush grade) after tenecteplase (TNK) administration. Therefore, our study aimed to evaluate the behavior of QTcD in electrocardiography (ECG) before and 60minutes after thrombolysis according to PIS, as an early marker of reperfusion after thrombolytic therapy when added to classical criteria. 20