TIMI Myocardial Perfusion Grade and ST-segment resolution in the assessment of coronary reperfusion after primary angioplasty

Abstract

Angiographic coronary flow parameters and resolution of ST segment changes play an important role in the evaluation of reperfusion in patients with acute ST segment elevation myocardial infarction (STEMI). In previous studies on the relation between angiographic and electrocardiographic (ECG) parameters of coronary reperfusion, several alternative methods to assess ST segment resolution were used. Thus, the relation between the TIMI Myocardial Perfusion Grade (TMPG) and different methods to evaluate ST segment resolution seems to be of interest. To evaluate the relationship between TMPG and absolute and relative ST segment resolution after successful primary percutaneous coronary intervention (pPCI). We studied a population of STEMI patients successfully treated with pPCI. Reperfusion of the coronary microcirculation was determined using 4-grade TMPG scale in coronary angiography performed after successful pPCI. ST segment resolution was analysed in two manners: 1) by calculating the sum of ST segment elevation in infarct leads and depression in reciprocal leads after pPCI (absolute resolution, SSTD); 2) as a percent reduction of summed ST segment deviation from the baseline value (relative resolution, SSTD%). Maximum ST segment elevation in a single lead on the postprocedural ECG was measured to categorise the risk of death. ST segment elevation > 1 mm for an inferior infarct or > 2 mm for an anterior infarct was considered the criterion of high risk (high risk ECG). The study population included 183 patients treated with pPCI. We found a significant but weak negative correlation between TMPG and SSTD (r = -0.27, p = 0.0002). Significant differences in median SSTD were observed between TMPG 0 vs. TMPG 2 and TMPG 3 groups (p = 0.0034 and 0.0121, respectively) and also between TMPG 1 and TMPG 2 (p = 0.02). A significant but very weak positive correlation was found between TMPG and SSTD% (r = 0.16,p = 0.0286). However, further analyses showed that differences in median SSTD% between patients with different TMPG values were statistically insignificant (p = 0.1756). In patients with TMPG 2/3, a high risk ECG was absent considerably more often (p = 0.0007). However, angiographic features of successfully vs. unsuccessfully reperfused microcirculation did not correspond to the presence of a high risk ECG in about 34% of cases. TMPG is more closely related to absolute compared to relative ST segment resolution. A high risk ECG was absent in most patients with TMPG 2 or 3. However, in about one third of cases TMPG did not correspond to the presence of ECG high risk features. These data suggest that TMPG is complementary to ST segment resolution in the assessment of coronary reperfusion.