Utility of Global Registry of Acute Coronary Event Score (GRACE) and Thrombolysis in Myocardial Infarction Risk Score (TIMI Score) in predicting 30-day Mortality in patients undergoing primary angioplasty at a Tertiary care center – A record-based study

Introduction

ST-segment elevation myocardial infarction (STEMI) is a distinct form of acute myocardial infarction primarily triggered by the formation of a blood clot, resulting in the abrupt obstruction of coronary arteries at the site of a rupture. This rupture typically occurs in conjunction with pre-existing atheromatous deposits, often causing structural damage to the plaque and the presence of calcified deposits.¹ Patients who present with STEMI, the most suitable approach is primary percutaneous coronary intervention with the deployment of a stent at the lesion site. This helps to reopen the obstructed coronary artery and immediately restore the coronary blood flow. PCI aims to achieve restoration of coronary blood flow and prevent myocardial salvage.²

The TIMI Risk Score tailored for STEMI patients, predicts an increased mortality rate within 30 days of intervention. This score is drawn based on eight clinical indicators that includes age, angina, hypertension, presence of diabetes, systolic blood pressure < 100 mmHg, heart rate exceeding 100 beats per minute, Killip class II to IV, weight less than 67 kg, new left bundle branch block (LBBB) or anterior wall MI (AWMI), and time to fibrinolytic therapy exceeding 4 hours) which are recorded at the time of admission. Their cumulative values ranges from 0 to 14. Based on the scoring system, the patients are categorized into distinct risk tiers: low-risk (0-5 points), medium-risk (6-7 points), and high-risk (>7 points). This classification helps healthcare providers to assess and stratify the level of risk associated with 30-day mortality in STEMI patients based on objective clinical information recorded at the time of admission.³

The GRACE score is widely used for forecasting inpatient mortality. It uses eight key factors: age, cardiac arrest, BP, cardiac biomarkers, Killip class, serum creatinine, ST segment deviation, and heart rate. The patients were categorized as low (0-95), medium (96-125), or high (>125) based on their scores.⁴

The current research aims to evaluate the effectiveness of the GRACE and TIMI risk scores in predicting death within 30 days from receiving primary PCI.

Methods

Participants

The study included 94 participants who presented with STEMI. These patients received primary PCI at the Department of Cardiology, Kasturba Medical College Hospital, Mangalore. STEMI is defined as ST-segment elevation ≥ 1 mm in 2 contiguous electrocardiographic leads or ≥ 2 mm in precordial leads V₁ to V₃. Individuals with a history of ischemic heart disease were excluded from this study (Figure 1).

Figure 1. Flow diagram showing recruitment of participants for the study.

Results

Baseline parameters: This research encompassed 94 STEMI patients within a specific age range (average age of 59.4 ± 9.0 years). Among the 94 participants, 75 (80%) were male and 19 (20%) were female. The patient’s baseline characteristics were thoroughly examined and discussed in detail in the table below (Table 1).¹⁰

The baseline LVEF average for the PCI cohort was 47.5 ± 5.7. Post-follow-up, the mean LVEF was 49.0 ± 7.0, the p-value was 0.09. SVD was diagnosed in 50 (53%) patients, DVD in 29 (31%), and TVD in 15 (16%).

Based on the TIMI score, 50 patients (53.1%) were categorized as low risk, 25 patients (26.5%) as medium risk, and 19 patients (20.1%) as high risk. The average TIMI score was 5.3 ± 2.4. The GRACE score classification resulted in 27 patients (28.7%) ranked in the minimal-risk category, 37 (39.3%) in the intermediate-risk category, and 30 (31.9%) in the high-risk category. The mean GRACE score was calculated at 119.5 ± 37.4.

The 30-day mortality was considered as the state variable. Also, this study employed the ROC-curve-AUC-analysis to examine the distinguishing outcomes of both TIMI scores and GRACE scores. A ROC curve shows the relationship between the true positive rate displayed on the vertical axis and the complement of the true negative rate on the horizontal axis even as one adjusts the classification threshold. The ROC curve area was established at 95% confidence level. In Figure 2, the TIMI score yielded an AUC of 0.80, whereas in Figure 3, the GRACE score resulted in an AUC of 0.81.

Figure 2. ROC curve for TIMI Scores for predicting 30-day mortality.

ROC curve area for the TIMI score =0.008.

Figure 3. ROC curve for GRACE scores for predicting 30-day mortality.

ROC curve area for the GRACE score = 0.006.

Both TIMI and GRACE scores showed strong diagnostic performances. Each score exhibited 99% specificity and 85% sensitivity, and their p-values (TIMI, p = 0.008; GRACE, p = 0.006) were statistically significant. During the follow-up period of 1 month, the outcome events indicated 4% reinfarction, 6% re-hospitalization, 1% heart failure, and 14% death.

Discussion

The observations from the study indicated that with age, the degree of acute coronary events also increases; the incidence is higher among males than in females. In this study, the presence of hypertension and diabetes were directly associated with advancing age and risk factors like hypertension and diabetes. The above findings were seen in agreement with research by Elizabeth RC Millet et al.⁵; this study investigated gender differences among the risk factors for MI and concluded that the incidence of MI was higher in men than in women for all the predicted risk factors and the gender difference in the risk factors reduced with advancing age.

The results from the current study documented 13 case fatalities following primary PCI; this included 6 in-hospital deaths and 7 out-of-hospital deaths. Upon evaluating their TIMI and GRACE scores, it was noted that 5 participants belonged to the High-Risk category, indicating the comparable predictive value of both scores. Further investigation revealed that the results were similar to the findings of the study by Correia, LC et al.¹ which concluded that the discriminatory capacity of both scores was similar for in-hospital death.

In the current study, researchers calculated the sensitivity and specificity of the scores by using the ROC curve. The TIMI Risk Score showed an 85% true-positive rate and a 99% true-negative rate, with a p-value of 0.008. Similarly, the GRACE Score exhibited a true positive rate of 85%, a true negative rate of 99%, and a p-value of 0.006. These results indicated that the discriminatory capacity of both GRACE and TIMI scores were similar. Thus, these findings were noted to align with the research findings by Correia et al.¹

In a previous study by J.M. Poldervaart et al.,⁶ the HEART, TIMI, and GRACE scores exhibited different levels of true positive rate and true negative rate, with values of 0.36 and 0.95, 0.96 and 0.50, and 0.78 and 0.56, respectively. The AUC values were 0.80 for TIMI and HEART was 0.70 GRACE. Indirect comparison findings indicate that TIMI and HEART scores outperformed the GRACE score in predicting MACEs. However, there were no noteworthy disparities between HEART and TIMI scores for predicting MACEs.

In another study by Jun Ke et al.,⁷ both TIMI and HEART scores demonstrated higher effectiveness than GRACE scores in predicting the risk of Major adverse cardiovascular events (MACE) among selected participants with sudden chest discomfort.

In the current study, LVEF was recorded at the time of presentation and re-assessed during follow-up. In the course of 30-day follow-up, those patients who received primary PCI exhibited improvement in the left ventricular performance. In another study by Eslami et al.⁸; the results concluded that recovery of LV after STEMI assessed by LVEF took as long as 2 months after primary PCI and not immediate, but early recovery of LV was noted in global longitudinal strain (GLS). The current study findings showed improvement in left ventricular ejection fraction by >2% (47% to 49%) within a period of 30 days. Therefore, the current study concluded that left ventricular recovery was not immediate after PCI, but improves gradually over time following successful revascularization.

During the follow-up, patients experienced cardiovascular complications, with mortality being more frequent. A smaller proportion of patients reported instances of reinfarction, and in all four cases, the cause was attributed to the omission of antiplatelet drugs. These findings align with a study conducted by Jafri SM et al.,⁹ which emphasizes the strong recommendation for continuing Aspirin for secondary prevention after myocardial infarction unless contraindications are present. The various causal factors for hospitalization includes reinfarction, chest pain, pulmonary edema, contrast-induced nephropathy, lower respiratory tract infection (LRTI), ischemic myocarditis, pedal edema, and left ventricular apical clots.

Conclusion

The study’s findings suggest that the discriminatory capabilities of both GRACE and TIMI scores were akin. The TIMI Risk Score demonstrated a sensitivity of 85% and specificity of 99%, whereas the GRACE Score exhibited a sensitivity of 85% and specificity of 99% in predicting 30-day mortality among patients presenting with STEMI. Notably, both scores assorted 60% of patients into the same risk category.

Over a one-month follow-up period, patients who underwent PCI displayed an enhancement in left ventricular function. This indicates that recovery of left ventricular function following PCI was not immediate, but rather exhibited a gradual improvement.