Abstract
Background
To our knowledge, no study so far investigated the importance of post‐procedural frontal QRS‐T angle f(QRS‐T) in ST segment elevation myocardial infarction (STEMI). The aim of our study was to investigate the role of baseline and post‐procedural f(QRS‐T) angles for determining high risk STEMI patients, and the success of reperfusion.
Methods
A total of 248 patients with first acute STEMI that underwent primary percutaneous coronary intervention (pPCI) or thrombolytic therapy (TT) between 2013 and 2014 were included in this study. Baseline f(QRS‐T) angle was defined as the angle which measured from the first ECG at the time of hospital admission. Post‐procedural (QRS‐T) angle was defined according to the treatment strategy as follows: the angle which measured from the post‐PCI ECG in patients treated with pPCI; the angle which measured from the ECG taken 90 min after onset of therapy in patients treated with TT.
Results
The baseline (101.9° ± 48.0 vs. 72.1° ± 49.1, p = 0.014) and post‐procedural f(QRS‐T) angles (95.7° ± 48.1 vs. 58.1° ± 47.1, p = 0.002) were significantly higher in patients who developed in‐hospital mortality than the patients who did not develop in‐hospital mortality. Also, f(QRS‐T) angle measured at 90 min was significantly lower in patients with successful thrombolysis group compared to failed thrombolysis group (53.2° ± 42.8 vs. 77.3° ± 52.9, p = 0.033), whereas baseline f(QRS‐T) angle was similar between two groups (78.6° ± 53.4 vs. 78.9° ± 54.0, p = 0.976). Multivariate analysis showed that post‐procedural f(QRS‐T) angle ≥89.6° (odds ratio: 3.541, 95% confidence interval: 1.235–10.154, p = 0.019), but not baseline f(QRS‐T) angle, was independent predictor of in‐hospital mortality.
Conclusion
f(QRS‐T) angle may be used as a beneficial tool for determining high risk patients in acute STEMI. Unlike previous studies, we showed for the first time that that post‐procedural f(QRS‐T) can predict in‐hospital mortality and TT failure.
Keywords: baseline f(QRS‐T) angle, post‐procedural f(QRS‐T) angle, risk assessment, ST elevated myocardial infarction
1. INTRODUCTION
Acute ST segment elevation myocardial infarction (STEMI) is still associated with increased risk of death and recurrent cardiovascular events despite considerable progress in therapy options. Therefore, early risk stratification in patients with acute STEMI is very important for determining their optimal management (Hudzik, Lekston, & Gasior, 2016). To date, several electrocardiographic (ECG) parameters have been used for stratifying patients on hospital admission (Schweitzer & Keller, 2001). However, novel ECG parameters have recently emerged to identify high risk patients in acute STEMI. One of these novel ECG parameters is the frontal plane QRS‐T angle.
Frontal plane QRS‐T [f(QRS‐T)] angle which defined as the angle between the directions of ventricular depolarization (QRS axis) and repolarization (T axis), was described as a novel marker of ventricular repolarization heterogeneity (Macfarlane, 2012; Oehler, Feldman, Henrikson, & Tereshchenko, 2014). It can be easily measured from surface ECG by subtracting the QRS axis from the T axis, because QRS and T‐wave axes are usually available in the automatic reports of many 12‐lead ECG devices (Macfarlane, 2012; Oehler et al., 2014; Pavri et al., 2008; Zhang, Rautaharju, Prineas, Tereshchenko, & Soliman, 2017). Previous studies had shown the prognostic value of the f(QRS‐T) angle in the different populations (Aro et al., 2012; Gotsman et al., 2013; Oehler et al., 2014). In addition to these studies, a previous study (Raposeiras‐Roubin et al., 2014) showed that a wide f(QRS‐T) angle (>90°) is a good discriminator of long‐term mortality in patients with left ventricular systolic dysfunction after an acute myocardial infarction.
Although the relationships between the baseline f(QRS‐T) angle and the mortality of patients with acute STEMI has been investigated in previous studies (Raposeiras‐Roubin et al., 2014; Sawant, Narra, Mills, & Srivatsa, 2013), to our knowledge, there is no study investigating the association of both baseline f(QRS‐T) and post‐procedural f(QRS‐T) angles with poor prognostic events in patients with acute STEMI undergoing revascularization therapy (primary percutaneous coronary intervention, pPCI + thrombolytic therapy, TT). The aim of our study was to evaluate the prognostic importance of baseline and post‐procedural f(QRS‐T) angles in patients with acute STEMI. In addition, the clinical usefulness of baseline and post‐procedural f(QRS‐T) angles for predicting reperfusion success in patients who received TT will be investigated.
2. METHODS
2.1. Patient selection
We retrospectively investigated the archived records of 301 consecutive patients with the diagnosis of first acute STEMI who were admitted to Dokuz Eylul University and were treated with pPCI or TT between 2013 and 2014. All patients had the following criteria: age over 18 years, presenting with first acute STEMI, being treated with coronary angiography (CAG) in our catheter laboratory. Major exclusion criteria were the occurrence of complete and incomplete right or left bundle brunch block, pacemaker rhythm, history of coronary artery bypass graft (CABG) and coronary artery disease. In addition, 15 patients could not undergo CAG were also excluded. Consequently, 248 patients with the diagnosis of first acute STEMI were included in our study. The diagnosis of acute STEMI was based on the European Society of Cardiology (ESC) 2012 STEMI guideline of “Third Universal Definition of Myocardial Infarction” (Thygesen et al., 2012).
2.2. Electrocardiography
A 12 lead ECGs were recorded for all patients at hospital admission, immediately after pPCI and 90 min after thrombolytic treatment. ECG recordings were taken using a 0.16–100 Hz filter range, 25 mm/s speed, and 10 mm/mV height. All of the ECG recordings were analyzed by two independent physicians. Frontal QRS and T‐wave axes were available in the automatic reports of the ECG machine. The f(QRS‐T) angle was calculated from these axes as absolute difference between frontal plane QRS axis and frontal plane T axis. If the angle exceeds 180°, it was calculated by subtracting from 360o (Jogu et al., 2017; Macfarlane, 2012; Oehler et al., 2014; Zhang et al., 2017). Because our calculation of f(QRS‐T) angle was based on automatic report of ECG machine, the subjective component of the individual measurements have been eliminated. Baseline f(QRS‐T) angle was defined as the angle which measured from the first ECG at the time of hospital admission. Post‐procedural f(QRS‐T) angle was defined according to the treatment strategy as follows: the angle which measured from the post‐PCI ECG in patients treated with pPCI; the angle which measured from the ECG taken 90 min after onset of therapy in patients treated with TT. ST segment resolution (STR) was calculated as the baseline sum of ST segment elevation minus the sum of ST segment elevation at the end of thrombolytic treatment ECG divided by the initial ST segment elevation (De Lemos et al., 2000). Successful thrombolysis was defined as ≥50% decrease in ST elevation and the loss of chest pain after TT. Failed thrombolysis was defined as <50% decrease in ST elevation after TT (De Lemos et al., 2001).
2.3. Coronary angiography
The PCI procedures were performed according to standard clinical protocols via the femoral route. Standard left or right Judkins diagnostic and guiding catheters were used in all procedures. All angiographic data of patients were assessed from the catheterization laboratory records and evaluated by two independent interventional cardiologists. The angiographically critical lesion was defined as the presence of ≥50% stenosis in the left main coronary artery and ≥70% in the other major epicardial coronary arteries. Each culprit lesion in the epicardial coronary artery was classified as proximal, mid, and distal according to the definition by American College of Cardiology and American Heart Association (Austen et al., 1975; Serruys et al., 1999).
2.4. Statistical analysis
SPSS for Windows version 21.0 (SPSS Inc., IL, USA) was used for statistical analysis. Continuous variables were expressed as means ± standard deviations and categorical variables were expressed as percentages. Continuous data were compared using Student's t test. Categorical data were compared using the chi‐square test. Pearson's correlation coefficient was used for correlation analysis. Receiver operating characteristic (ROC) curve analysis was performed to determine the optimal cut‐off value of baseline and post‐procedural f(QRS‐T) angles for predicting in‐hospital mortality. Variables entered into multivariate model included those with p values <0.1 from the univariate analysis. Multivariate logistic regression analysis was performed to determine the independent predictors of in‐hospital mortality. A value of p < 0.05 was considered statistically significant.
3. RESULTS
3.1. Baseline characteristics of patients
The mean age of the patients was 58.8 ± 12.7, with 77.4% men. One hundred and forty‐two patients underwent pPCI, whereas 106 patients underwent TT. In‐hospital mortality was developed in 20 patients. When pPCI group compared to TT group, it was found that basal demographic characteristics, baseline and post‐procedural f(QRS‐T) angles, MI localization, and in‐hospital mortality rate were similar between two groups. However, STR was significantly higher in TT group than in pPCI group (Table 1).
Table 1.
Comparison of clinical characteristics, laboratory, and angiographic variables according to treatment modality
| Primary PCI (n = 142) | Thrombolytic therapy (n = 106) | p‐value | |
|---|---|---|---|
| Age, years | 57.9 ± 13.4 | 59.9 ± 11.6 | 0.213 |
| Sex, male (%) | 114 (80.3) | 78 (73.6) | 0.212 |
| Hypertension (%) | 58 (40.8) | 51 (48.1) | 0.254 |
| Diabetes Mellitus (%) | 35 (24.6) | 29 (27.4) | 0.629 |
| Duration of chest pain on admission (min) | 141.0 ± 136.7 | 150.9 ± 188.6 | 0.647 |
| Medications | |||
| Beta‐blockers | 110 (77.5) | 77 (72.6) | 0.383 |
| ACE‐I or ARB | 118 (83.1) | 86 (81.1) | 0.688 |
| LVEF (%) | 46.9 ± 8.8 | 45.6 ± 10.2 | 0.267 |
| Creatinine (mg/dl) | 1.3 ± 0.4 | 1.2 ± 0.1 | 0.821 |
| Peak CK‐MB (ng/ml) | 142.7 ± 103.0 | 167.4 ± 104.4 | 0.064 |
| ST segment resolution (%) | 56.1 ± 40.2 | 67.0 ± 24.5 | 0.010 |
| Baseline f(QRS/T) (°) | 71.0 ± 46.6 | 78.7 ± 53.3 | 0.245 |
| Post‐procedural f(QRS/T) (°) | 62.1 ± 49.4 | 58.5 ± 46.0 | 0.571 |
| MI localization | |||
| Anterior MI (%) | 66 (46.5) | 37 (34.9) | 0.067 |
| Other MI (%) | 76 ()53.5 | 69 (65.1) | |
| Infarct‐related artery | |||
| LAD (%) | 75 (52.8) | 41 (38.7) | 0.087 |
| CX (%) | 22 (15.5) | 21 (19.8) | |
| RCA (%) | 45 (31.7) | 44 (41.5) | |
| Proximal vessels disease (%) | 79 (55.6) | 65 (61.3) | 0.369 |
| Three vessels disease (%) | 20 (14.1) | 25 (23.6) | 0.055 |
| In‐hospital mortality (%) | 9 (6.3) | 11 (10.4) | 0.248 |
Min, minute; SBP, systolic blood pressure; DBP, diastolic blood pressure; PCI, percutaneous coronary intervention; ACE‐I, angiotensin‐converting enzyme inhibitor; ARB, angiotensin receptor blocker; LVEF, left ventricular ejection fraction; BUN, blood urine nitrogen; CK‐MB, creatinine kinase‐ MB; MI, myocardial infarction; LAD, left anterior descending artery; CX, circumflex artery; RCA, right coronary artery.
3.2. Findings according to baseline f(QRS‐T) angle
The baseline f(QRS‐T) angle was significantly higher in patients who developed in‐hospital mortality than the patients who did not develop in‐hospital mortality (101.9° ± 48.0 vs. 72.1° ± 49.1, p = 0.014). ROC curve analysis was performed to determine the optimal cut‐off value of baseline f(QRS‐T) angle for predicting in‐hospital mortality. Baseline f(QRS‐T) angle ≥95.6° predicted in‐hospital mortality with a specificity 72.1% and a sensitivity of 66.7% (Figure 1a). Our study group was divided into two groups according to this cut‐off value: those with baseline f(QRS‐T) angle <95.6° (173 patients) and those with baseline f(QRS‐T) angle ≥95.6° (75 patients). Patients with baseline f(QRS‐T) angle ≥95.6° were older, had a higher frequency of diabetes mellitus, a lower left ventricular ejection fraction (LVEF), a lower rate of STR, higher levels of blood urea nitrogen and higher peak CK‐MB values compared to patients with baseline f(QRS‐T) angle <95.6°. These patients had also more frequent proximal vessels disease, more frequent three vessels disease, and higher rate of in‐hospital mortality. No significant differences were observed between two groups regarding other clinical features and infarct‐related artery localization (Table 2).
Figure 1.
(a) ROC curve analysis of baseline f(QRS‐T) angle for predicting in‐hospital mortality (b) ROC curve analysis of post‐procedural f(QRS‐T) angle for predicting in‐hospital mortality
Table 2.
Comparison of clinical characteristics, laboratory, and angiographic variables according to baseline f(QRS‐T) angle
| Baseline f(QRS‐T) <95.6° (n = 173) | Baseline f(QRS‐T) ≥95.6° (n = 75) | p‐value | |
|---|---|---|---|
| Age | 57.3 ± 11.8 | 62.2 ± 14.0 | 0.005 |
| Sex, male (%) | 139(80.3) | 53 (70.7) | 0.094 |
| Hypertension (%) | 69 (39.9) | 40 (53.3) | 0.050 |
| Diabetes Mellitus (%) | 37 (21.4) | 27 (36) | 0.016 |
| Duration of chest pain on admission (min) | 144.3 ± 168.3 | 147.2 ± 142.3 | 0.899 |
| Medications | |||
| Beta‐blockers | 132 (76.3) | 55 (73.3) | 0.618 |
| ACE‐I or ARB | 140 (80.9) | 64 (85.3) | 0.404 |
| LVEF (%) | 47.0 ± 9.6 | 43.6 ± 9.6 | 0.013 |
| Creatinine (mg/dl) | 0.9 ± 0.4 | 1.0 ± 0.5 | 0.122 |
| Peak CK‐MB (ng/ml) | 139.4 ± 102.4 | 196.1 ± 98.9 | <0.001 |
| ST segment resolution (%) | 64.3 ± 34.6 | 53.0 ± 33.8 | 0.020 |
| Baseline f(QRS‐T) (°) | 46.4 ± 26.5 | 137.1 ± 26.5 | <0.001 |
| Post‐procedural f(QRS‐T) (°) | 47.0 ± 42.4 | 91.8 ± 45.6 | <0.001 |
| MI localization | |||
| Anterior MI (%) | 67 (38.7) | 36 (48) | 0.174 |
| Other MI (%) | 106 (61.3) | 39 (52) | |
| Infarct‐related artery | |||
| LAD (%) | 73 (42.2) | 43 (57.3) | 0.089 |
| CX (%) | 33 (19.1) | 10 (13.3) | |
| RCA (%) | 67 (38.7) | 22 (29.3) | |
| Proximal vessels disease (%) | 93 (53.8) | 51 (68) | 0.037 |
| Three vessels disease (%) | 22 (12.7) | 23 (30.7) | 0.001 |
| In‐hospital mortality (%) | 8 (4.6) | 12 (16) | 0.003 |
Min, minute; SBP, systolic blood pressure; DBP, diastolic blood pressure; PCI, percutaneous coronary intervention; ACE‐I, angiotensin‐converting enzyme inhibitor; ARB, angiotensin receptor blocker; LVEF, Left ventricular ejection fraction; BUN, blood urine nitrogen; CK‐MB, creatinine kinase‐ MB; MI, myocardial infarction; LAD, left anterior descending artery; CX, circumflex artery; RCA, right coronary artery.
3.3. Findings according to post‐revascularization f(QRS‐T) angle
The post‐procedural f(QRS‐T) angle was significantly higher in patients who developed in‐hospital mortality than the patients who did not develop in‐hospital mortality (95.7° ± 48.1 vs. 58.1° ± 47.1, p = 0.002). ROC curve analysis was performed to determine the optimal cut‐off value of post‐procedural f(QRS‐T) angle for predicting in‐hospital mortality. Post‐procedural f(QRS‐T) angle ≥89.6° predicted in‐hospital mortality with a specificity of 77.8% and sensitivity of 62.5% (Figure 1b). Also, it was found that the area under curve (AUC) of the post‐procedural f(QRS‐T) angle (0.725) was higher than the AUC of the baseline f(QRS‐T) angle (0.678). Patients were divided into two groups according to this cut‐off value: those with post‐procedural f(QRS‐T) angle <89.6° (189 patients) and those with post‐procedural f(QRS‐T) angle ≥89.6° (59 patients). When patients with post‐procedural f(QRS‐T) angle ≥89.6° compared to post‐procedural f(QRS‐T) angle <89.6°, it was found that patients with post‐procedural f(QRS‐T) angle ≥89.6° had a lower left ventricular ejection fraction (LVEF), a lower rate of STR, and higher peak CK‐MB values compared to patients with post‐procedural f(QRS‐T) angle <89.6°. In addition, patients with post‐procedural f(QRS‐T) angle ≥89.6° had a higher rate of in‐hospital mortality (Table 3). Furthermore, as demonstrated in Figure 2a, post‐procedural f(QRS‐T) angle was not significantly changed in patients who developed in‐hospital mortality (from 101.9° ± 48.0 to 99.1° ± 47.3, p = 0.697), whereas it was significantly reduced in patients who did not develop in‐hospital mortality (from 72.1° ± 49.2 to 58.5° ± 47.3, p < 0.001).
Table 3.
Comparison of clinical characteristics, laboratory, electrocardiographic, and angiographic variables according to post‐procedural f(QRS‐T) angle
| Post‐procedural f(QRS‐T) <89.6° (n = 189) | Post‐procedural f(QRS‐T) ≥89.6° (n = 59) | p‐value | |
|---|---|---|---|
| Age, years | 58.3 ± 12.3 | 60.5 ± 13.8 | 0.249 |
| Sex, male (%) | 146 (77.2) | 46 (78) | 0.908 |
| Hypertension (%) | 86 (45.5) | 23 (39) | 0.378 |
| Diabetes Mellitus (%) | 47 (24.9) | 17 (28.8) | 0.545 |
| Duration of chest pain on admission (min) | 146.9 ± 162.1 | 139.8 ± 157.0 | 0.768 |
| Medications | |||
| Beta‐blockers | 146 (77.2) | 41 (69.5) | 0.227 |
| ACE‐I or ARB | 156 (82.5) | 48 (81.4) | 0.835 |
| LVEF (%) | 46.8 ± 9.8 | 43.3 ± 8.9 | 0.018 |
| Creatinine (mg/dl) | 0.93 ± 0.45 | 0.99 ± 0.47 | 0.388 |
| Peak CK‐MB (ng/ml) | 152.4 ± 107.3 | 169.6 ± 94.5 | 0.272 |
| ST segment resolution (%) | 64.0 ± 31.5 | 50.2 ± 42.4 | 0.009 |
| Baseline f(QRS‐T) (°) | 65.2 ± 45.5 | 102.6 ± 51.6 | <0.001 |
| Post‐procedural f(QRS‐T) (°) | 39.5 ± 29.0 | 130.2 ± 27.8 | <0.001 |
| MI localization | |||
| Anterior MI (%) | 79 (41.8) | 24 (40.7) | 0.879 |
| Other MI (%) | 110 (58.2) | 35 (59.3) | |
| Infarct‐related artery | |||
| LAD (%) | 89 (47.1) | 27 (45.8) | 0.524 |
| CX (%) | 30 (15.9) | 13 (22) | |
| RCA (%) | 70 (37) | 19 (32.2) | |
| Proximal vessels disease (%) | 104 (55) | 40 (67.8) | 0.083 |
| Three vessels disease (%) | 35 (18.5) | 10 (16.9) | 0.785 |
| In‐hospital mortality (%) | 10 (5.3) | 10 (16.9) | 0.011 |
Min, minute; SBP, systolic blood pressure; DBP, diastolic blood pressure; PCI, percutaneous coronary intervention; ACE‐I, angiotensin‐converting enzyme inhibitor; ARB, angiotensin receptor blocker; LVEF, Left ventricular ejection fraction; BUN, blood urine nitrogen; CK‐MB, creatinine kinase‐ MB; MI, myocardial infarction; LAD, left anterior descending artery; CX, circumflex artery; RCA, right coronary artery.
Figure 2.
(a) Comparison of baseline and post‐procedural f(QRS‐T) angles between in‐hospital mortality (+) and mortality (−) groups (b) Comparison of baseline and 90 min f(QRS‐T) angles in successful and failed thrombolysis groups in acute STEMI patients treated with thrombolytic therapy
3.4. Thrombolytic therapy subgroup
One hundred and six (42.7%) patients underwent TT in our study. Successful thrombolysis was observed in 78 patients after TT, whereas failed thrombolysis was observed in 28 patients after TT according to electrocardiographic criteria. Our study group was divided into groups according to the presence of STR on ECG after TT. f(QRS‐T) angle measured at 90 min was detected to be lower in patients with successful thrombolysis group compared to failed thrombolysis group. However, there was no significant difference in terms of baseline f(QRS‐T) angle between two groups (Table 4). More importantly, as showed in Figure 2b, 90th min f(QRS‐T) angle was significantly reduced in patients with successful thrombolysis (from 78.6° ± 53.4 to 53.2° ± 42.9, p < 0.001), whereas it was not reduced in patients with failed thrombolysis (from 76.7° ± 56.4 to 77.3° ± 52.9, p = 0.961).
Table 4.
Comparison of clinical characteristics, electrocardiographic, and angiographic variables according to success of thrombolysis
| Successful thrombolysis (n = 78) | Failed thrombolysis (n = 28) | p‐value | |
|---|---|---|---|
| MI localization | |||
| Anterior MI (%) | 27 (34.6) | 10 (35.7) | 0.917 |
| Other MI (%) | 51 (65.4) | 18 (64.3) | |
| Door‐to‐needle time (min) | 19.4 ± 3.2 | 19.8 ± 4.2 | 0.462 |
| Baseline f(QRS‐T) angle (°) | 78.6 ± 53.4 | 78.9 ± 54.0 | 0.976 |
| 90th min f(QRS‐T) angle (°) | 53.2 ± 42.8 | 77.3 ± 52.9 | 0.033 |
| ST segment resolution (%) | 74.5 ± 23.2 | 46.3 ± 14.3 | <0.001 |
MI, myocardial infarction; min, minute.
3.5. Correlation analysis of baseline and post‐procedural f(QRS‐T) angles with other parameters
Baseline f(QRS‐T) angle was positively correlated with number of vessel with critical stenosis (r = 0.244, p < 0.001), and peak CK‐MB (r = 0.206, p = 0.001) whereas negatively correlated with LVEF (r = −0.157, p = 0.014), and STR (r = −0.166, p = 0.010); even if they were weak. In addition, although they were weak, post‐procedural f(QRS‐T) angle was positively correlated with age (r = 0.152, p = 0.019), and peak CK‐MB (r = 0.198, p = 0.0012), whereas negatively correlated with LVEF (r = −0.239, p < 0.001), and STR (r = −0.173, p = 0.008).
3.6. Independent predictors of in‐hospital mortality
Univariate and multivariate logistic regression analysis were performed to determine the independent predictors of in‐hospital mortality. In univariate analysis, age, female gender, LVEF, baseline f(QRS‐T) angle ≥95.6°, post‐procedural f(QRS‐T) angle ≥89.6° and three vessels disease were found to be associated with in‐hospital mortality. Multivariate logistic regression analysis showed that age (OR: 1.080, 95% CI: 1.032–1.131, p = 0.001), LVEF (OR: 0,918, 95% CI: 0.863–0.976, p = 0.006), and post‐procedural f(QRS‐T) angle ≥89.6° (OR: 3.541, 95% CI: 1.235–10.154, p = 0.019) were the independent predictors of in‐hospital mortality (Table 5). It was found that patients with post‐procedural f(QRS‐T) angle ≥89.6° had a 3.54‐fold increased risk for in‐hospital mortality.
Table 5.
Univariate and multivariate analysis for determining the independent predictors of in‐hospital mortality
| Univariate analysis | Multivariate analysis | |||
|---|---|---|---|---|
| OR (95% CI) | p | OR (95% CI) | p | |
| Age | 1.103 (1.055–1.102) | <0.001 | 1.080 (1.032–1.131) | 0.001 |
| Female gender | 3.151 (1.234–8.046) | 0.016 | 2.280 (0.780–6.661) | 0.132 |
| Hypertension | 1.303 (0.522–3.253) | 0.571 | ||
| Diabetes Mellitus | 1.615 (0.615–4.246) | 0.331 | ||
| Duration of chest pain on admission | 1.000 (0.997–1.003) | 0.965 | ||
| Door‐to‐needle time | 1.004 (0.990–1.018) | 0.561 | ||
| LVEF | 0.900 (0.852–0.951) | <0.001 | 0.918 (0.863–0.976) | 0.006 |
| Peak CK‐MB (ng/ml) | 1.014 (1.001–1.028) | 0.039 | 1.010 (0.992–1.027) | 0.273 |
| MI localization | 1.807 (0.720–4.533) | 0.208 | ||
| ST segment resolution (%) | 1.007 (0.991–1.023) | 0.417 | ||
| Baseline f(QRS‐T) ≥95.6° | 3.929 (1.564–10.062) | 0.004 | 1.176 (0.365–3.785) | 0.786 |
| Post‐procedural f(QRS‐T) ≥89.6° | 3.653 (1.439–9.275) | 0.006 | 3.541 (1.235–10.154) | 0.019 |
| Proximal vessels disease (%) | 1.759 (0.653–4.742) | 0.264 | ||
| Three vessels disease (%) | 3.441 (1.316–9.000) | 0.012 | 2.258 (0.709–7.190) | 0.168 |
LVEF, left ventricular ejection fraction; MI, myocardial infarction.
4. DISCUSSION
In this study, we investigated the prognostic importance of the baseline and post‐procedural f(QRS‐T) angles for the early risk stratification in patients with acute STEMI. The main finding of our study was that wider post‐procedural f(QRS‐T) angle, but not baseline f(QRS‐T) angle, was an independent predictor of in‐hospital mortality in acute STEMI patients. In addition, we detected that the reduction of f(QRS‐T) angle after TT was associated with successful reperfusion. To our knowledge, this is the first study demonstrating the prognostic importance of post‐procedural f(QRS‐T) angle in patients with acute STEMI.
QRS‐T angle is a novel marker of myocardial depolarization and repolarization heterogeneity. It is defined as the angle between electrical directions of ventricular depolarization and repolarization (Macfarlane, 2012; Raposeiras‐Roubin et al., 2014; Zhang et al., 2017). Studies showed that the QRS‐T angle was more robust and reproducible, and less susceptible to noise and problems of definition than other traditional electrocardiographic myocardial repolarization parameters (Dilaveris, Antoniou, Gatzoulis, & Tousoulis, 2017; Raposeiras‐Roubin et al., 2014; Zhang et al., 2017) It can be calculated with two different methods: (a) three‐dimensional space, spatial QRS‐T angle, (b) a projection on the frontal plane in a standard 12‐lead ECG, frontal QRS‐T angle (Macfarlane, 2012; Oehler et al., 2014). The calculation of spatial angle is so complicated, required software programs and cannot be routinely calculated with daily used ECG devices ((Macfarlane, 2012; Oehler et al., 2014). Conversely, f(QRS‐T) angle can be easily calculated from surface ECG by subtracting the QRS axis from T axis, because most ECG devices report automatically QRS and T axes (Li et al., 2013). In addition, a previous study reported that f(QRS‐T) angle is a suitable clinical substitute for the spatial QRS‐T angle in risk prediction (Zhang, Prineas, Case, Soliman, & Rautaharju, 2007). We therefore used frontal QRS‐T angle in this study.
Normally, the directions of the myocardial depolarization axis and repolarization axis is in the similar orientation. Therefore, f(QRS‐T) angle often tend to be a narrow angle (<45°) (Gungor et al., 2017; Raposeiras‐Roubin et al., 2014; Tan et al., 2017). A wider f(QRS‐T) angle is associated with discordance between ventricular depolarization phase and repolarization phase and it was found to be associated with poor outcomes in different populations (Pavri et al., 2008; Raposeiras‐Roubin et al., 2014). However, limited data are available for evaluating the association of f(QRS‐T) angle with poor adverse events in patients with acute STEMI. In a recent study, Raposeiras‐Roubin et al., 2014, showed that f(QRS‐T) angle >90° is an independent predictor of long‐term mortality in acute STEMI patients. Similar to this study, we also found that patients with baseline f(QRS‐T) angle ≥95.6° had significantly higher in‐hospital mortality rate. These results suggest that acute STEMI patients with the higher baseline f(QRS‐T) angle have a higher cardiac risk. However, the most important novelty of our study is that we also evaluated the post‐procedural f(QRS‐T) angle in addition to baseline f(QRS‐T). We found that post‐procedural f(QRS‐T) angle was significantly higher in patients who developed in‐hospital mortality than in patients who did not develop in‐hospital mortality. In addition, post‐procedural f(QRS‐T) angle ≥89.6° was an independent predictor of in‐hospital mortality in multivariate analysis which including also baseline f(QRS‐T) angle. According to these results, we can conclude that post‐procedural f(QRS‐T) angle has a higher prognostic significance more than baseline f(QRS‐T) angle for predicting in‐hospital mortality. To our knowledge, this is the first study demonstrating the association of post‐procedural f(QRS‐T) angle with in‐hospital mortality in patients with acute STEMI. We think that the possible underlying mechanism for the association between wider f(QRS‐T) angle and in‐hospital mortality may be due to the presence of larger infarct area, poorer left ventricular function, and higher incidence three vessels disease in these patients.
Another important finding of our study was the relationship between f(QRS‐T) angle and the success of TT. We detected that although baseline f(QRS‐T) angle was similar between successful and failed thrombolysis groups, f(QRS‐T) angle measured at 90 min was significantly lower in successful thrombolysis group compared to failed thrombolysis group. In addition, f(QRS‐T) angle was significantly reduced in successful thrombolysis group, whereas it was not reduced in failed thrombolysis group. Moreover, baseline and post‐procedural f(QRS‐T) angles were negatively correlated with electrocardiographic STR. According to our findings, the lack of significant decrease in f(QRS‐T) angle after TT was associated with failed thrombolysis. Therefore, we suggest that the lack of decrease in f(QRS‐T) angle after TT in STEMI patients treated with TT may be used as a new parameter to predict failed thrombolysis. This is the first study showing the relationship between f(QRS‐T) angle and failed thrombolysis. We think that these findings will need to be validated in larger prospective studies.
The association of the f(QRS‐T) angle with the severity of coronary artery disease (CAD) have been investigated in previous studies. In a previous study, it was found that the prevalence of 2‐ or 3‐vessel obstructive CAD was significantly higher in patients with a planar QRS‐T angle >90° than in patients with a planar QRS‐T angle ≤90° (Palaniswamy et al., 2009). Similar to this study, we demonstrated that patients with baseline f(QRS‐T) angle ≥95.6° had significantly higher frequency of three vessels disease compared to patients with baseline f(QRS‐T) angle <95.6°. We think the possible underlying mechanism between the baseline f(QRS‐T) angle and three vessels diseases might be that the concomitant significant lesion in the noninfarct‐related coronary artery will result an increase in the frontal plane QRS‐T angle. In addition to this study, we also detected that patients with baseline f(QRS‐T) angle ≥95.6° had more frequent proximal vessels disease. However, post‐procedural f(QRS‐T) angle have not been found to be associated with the proximal vessels disease and three vessels disease in our study. These findings suggest that baseline f(QRS‐T) angle can be a useful parameter to demonstrate the severity of CAD, whereas post‐procedural f(QRS‐T) angle does not possess such quality. In contrast to these findings, Raposeiras‐Roubin et al., 2014, reported that there was no relationship between f(QRS‐T) angle and three vessels disease. This may be because that study included only acute STEMI patients who had depressed LVEF (≤40%). Further prospective studies with large number of patients are required to explain the association of baseline f(QRS‐T) angle with the severity of CAD.
Baseline characteristics, MI localization, and duration of chest pain were similar between groups in our study. However, we found that patients with baseline f(QRS‐T) angle ≥95.6° had a lower LVEF, and higher peak CK‐MB values. Also, as the baseline f(QRS‐T) angle increased, LVEF decreased and peak CK‐MB increased significantly. Similar to our study, previous studies have demonstrated that wider f(QRS‐T) angle is significantly related to lower LVEF and higher peak cardiac marker levels (Li et al., 2013; Lown et al., 2012). Moreover, we detected that wider post‐procedural f(QRS‐T) angle was associated with lower LVEF, and higher peak CK‐MB values. When all of this results were evaluated, we can suggest that both widened baseline f(QRS‐T) and widened post‐procedural f(QRS‐T) angles in STEMI patients associated with extent of myocardial scar tissue irrespective of MI localization. The association of f(QRS‐T) angle with larger scar tissue can be explained as follows: ischemic or infarcted myocardial zone is electrically inert resulting abnormal conduction occurs through infarct area due to regional cellular changes (Herweg, Marcus, & Barold, 2016). This condition may manifest heterogeneity between depolarization and repolarization waveform to result in widened post‐procedural f(QRS‐T) angle on surface ECG.
Early risk stratification in acute STEMI process is an important issue to determine high risk patients, and improve clinical outcomes. Because twelve lead ECG is a cheap and easily accessible tool, it have been used frequently to perform risk stratification. Recently, the most interested novel ECG parameter is f(QRS‐T) angle. However, all previous studies used the baseline f(QRS‐T) angle. Unlike other studies, we have showed for the first time that the concept of post‐procedural f(QRS‐T) angle can be a useful tool to determine high risk patients with STEMI in this study. Although we provided important information about the post‐procedural f(QRS‐T) angle, we think that these findings should be supported by larger prospective studies.
Our study's limitations included retrospective design and having relatively small number of patients. Another limitation is that we evaluated in‐hospital all cause mortality, but did not investigate causes of the in‐hospital mortality. To investigate the association between arrhythmic complications and f(QRS‐T) angle could provide additional contribution to this study. Third, both pPCI and TT patients were included and evaluated together in this study. Separate analysis may be useful, but when we compared two groups, we found that basal demographic characteristics, baseline and post‐procedural f(QRS‐T) angles, MI localization and in‐hospital mortality rate were similar between two groups. We think, this comparison strengths our results. Fourth, we did not record the time of in‐hospital mortality and long‐term follow‐up was not assessed. It could be interesting to investigate long‐term prognostic value of f(QRS‐T) angle in STEMI patients. Finally, although we used multivariate analysis to adjust for potential confounders, there may residual confounding from unmeasured covariates. Larger studies are needed to better elucidate the prognostic importance of post‐procedural f(QRS‐T) angle in patients with acute STEMI.
In conclusion, f(QRS‐T) angle is an inexpensive, noninvasive and easily detectable parameter on 12 lead ECG. In this study, we have shown for the first time that post‐procedural f(QRS‐T) angle has higher prognostic importance than baseline f(QRS‐T) angle for predicting high risk patients in acute STEMI. In addition, post‐procedural f(QRS‐T) angle can be used as a simple tool to determine failed reperfusion in acute STEMI patients receiving TT. Therefore, we think that the evaluation of f(QRS‐T) angle on surface ECG during acute STEMI may be an acceptable noninvasive electrocardiographic marker for cardiac risk assessment in future.
CONFLICT OF INTEREST
The authors declare that they have no conflicts of interest.
Colluoglu T, Tanriverdi Z, Unal B, Ozcan EE, Dursun H, Kaya D. The role of baseline and post‐procedural frontal plane QRS‐T angles for cardiac risk assessment in patients with acute STEMI. Ann Noninvasive Electrocardiol. 2018;23:e12558 10.1111/anec.12558
This study was presented as a poster presentation in ESC 2017 congress. European Heart Journal 38.suppl_1 (2017). https://doi.org/10.1093/eurheartj/ehx493.p5535
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