According to the guidelines of the European Society of Cardiology (ESC), the risk stratification and determination of the prognosis of the PE patients is necessary and can be helpful in choosing the best therapeutic strategy (1). However, the applicability of ECG changes for determining the prognosis of PE patients is under debate. Inverted T wave in precordial leads, S1Q3T3, and ST elevation in aVR were the most common ECG parameters in PE patients. These findings were also previously remarked as the most common ECG abnormalities in PE patients (9, 13–15). Furthermore, the results of the current study showed that some changes in ECG, including RBBB, iRBBB, S1Q3T3 sign, ST elevation in leads V1 and III, QR wave in lead V1, and inverted T wave in precordial leads were significantly more frequent in the MACE group than the control group. ST elevation in lead aVR and S1Q3T3 sign were associated with a higher risk of MACE during hospitalization. Although the sensitivity and positive predictive value of these changes were low, the specificity and negative predictive value were high. Therefore, these parameters in ECG can be considered as a cheap and widely available tool for rolling out the PE patients who are not at high risk of MACE. A similar study by Kukla et al. on 292 acute PE patients also reported that atrial fibrillation, S1Q3T3 sign, negative T waves in leads V2–V4, ST-segment depression in leads V4–V6, ST-segment elevation in leads III, V1 and aVR, QR in lead V1, RBBB, higher number of leads with negative T waves, and higher sum of the amplitude of negative T waves were more frequent in patients who experienced PE complications (7). Moreover, in multivariate analysis, ST-segment elevation in leads aVR (OR 2.49; p = 0.011) was identified as an independent predictor of complications during hospitalization. Nevertheless, this study did not report the sensitivity and specificity of these parameters for predicting the occurrence of complications during hospitalization (7). Also, Janata et al. investigated 396 PE patients and revealed that ST elevation in aVR was the only significant predictor of mortality in the intermediate-risk group. However, this association was not detected in high-risk patients (16). In a larger study conducted on 508 PE patients, Geibel et al. demonstrated that the presence of at least one of the following ECG findings, besides hemodynamic instability, syncope, and pre-existing chronic pulmonary disease, was a significant independent predictor of early (30-day) mortality. These ECG findings were atrial arrhythmias, complete RBBB, peripheral low voltage, Q waves in leads III and aVF, and ST-segment elevation or depression over the left precordial leads. In this study, the association of ECG findings with in-hospital mortality was not evaluated individually (17). Moreover, some prior studies used a combination of different ECG signs to develop a scoring system. Toosi et al. investigated a 21-point system based on ECG changes in 159 acute PE patients and reported that having a score of ≥ 3 in this scale can predict the occurrence of right ventricular dysfunction with high sensitivity and specificity of 76 and 82 percent, complicated disease course with moderate sensitivity and specificity of 58 and 60 percent, and mortality incidence with moderate sensitivity and specificity of 59 and 58 percent, respectively (10). Iles et al. evaluated a similar 21-point scoring system based on ECG changes on 229 PE patients and reported that an ECG score of ≥ 3 predicted those with > 50% perfusion defect with a sensitivity of 70% (95% confidence interval [CI], 59 to 81%), and a specificity of 59% (95% CI, 51 to 67%) (18). Another study also used a 21-point ECG score to predict right ventricular dysfunction, and reported a sensitivity of 92% and a negative predictive value of 97%; similarly, complications during hospitalization were predicted with sensitivity and negative predictive value of 75% and 92%, respectively (19). These studies suggested that ECG can be considered as s useful tool for the determination of the prognosis of PE patients; however, none of them investigated the association of the ECG findings individually with PE prognosis.
As far as we investigated, our study was the largest study that evaluated the prognosis of PE patients based on their ECG findings. Moreover, we reported sensitivity, specificity, and predictive value as well as OR and 95% CI for each ECG abnormalities individually in order to better clarify the association of ECG findings with the occurrence of MACE to be used in the clinical setting. However, our study had some limitations. We did not evaluate the laboratory data, medical and drug history, clinical presentation, echocardiographic findings, and medications administered during hospitalization for all the patients. This was partially due to some missing data of the patients’ files. As a result, we did not adjust the outcome for these confounding variables, which can be considered as a possible source of bias for our findings.
Moreover, we excluded the patients who had a positive history of taking antiarrhythmic medication such as digoxin, severe metabolic disease such as hypokalemia, myocardial infarction, heart failure, angina pectoris, sepsis, congenital heart disease, cor pulmonel, LBBB in admission ECG, and permanent pacemaker. These patients were excluded due to the possibility of ECG changes caused by these abnormalities that could interfere with the ECG changes due to PE. However, the exclusion of these patients can partially limit the generalizability of our findings as a considerable proportion of the PE patients have at least one of these abnormalities.