Outcomes after coronary computed tomography angiography of patients at low to intermediate risk for acute coronary syndrome
Correspondence Address: Source of Support: None, Conflict of Interest: None DOI: 10.4103/2322-5327.250545
Keywords: Computed tomography angiography, risk stratification, prognosis
Vascular atherosclerosis is a major cause of mortality worldwide,[1] creating a high economic burden for the diagnosis and treatment of coronary artery disease.[2] Usually 20% to 25% of cases with chest pain are due to coronary heart disease, but this disease is underdiagnosed in 2% to 10% and, on the other hand, there are some cases of overestimation and unnecessary treatment.[3],[4] In recent years, the frequency of acute coronary syndrome (ACS) has increased because of the increased rate of its risk factors.[5],[6] Recent guidelines subdivide patients according to their risk scores into 3 groups of mild, moderate, and severe.[7] The Global Registry of Acute Coronary Syndrome (GRACE) is a prospectively studied scoring system for the risk stratification of patients with diagnosed ACS with a view to estimating in-hospital and 6 months' to 3 years' mortality. In the mild group, only conservative treatment is indicated, whereas in the moderate and severe groups, early invasive treatment is indicated.[8] In patients with non-ST-elevation myocardial infarction, early invasive approaches are recommended with early angiography in the first 72 hours.[9] Since 60% to 70% of the cases presenting to the emergency department with chest pain are likely to have high troponin levels—with only a few cases due to myocardial infarction, the selection of an appropriate noninvasive method is of vital importance to reduce the application of invasive approaches. Coronary computed tomography angiography (CTA) has recently been demonstrated to enjoy a high negative predictive value for ruling out coronary heart disease and risk stratifying patients suffering from ACS.[10],[11],[12],[13],[14],[15],[16],[17],[18],[19],[20] CTA is recommended in patients at low to moderate risk for ACS presenting to the emergency department. Accordingly, we conducted the present study to assess the 1-year outcome associated with a CTA-guided strategy in patients presenting to the emergency department with low to intermediate risk for ACS according to the GRACE score.
This case-series study prospectively evaluated 77 consecutive patients (mean age = 49.7 ± 10.1 [standard deviation] and 53.2% female) who presented to the Emergency Department of Rajaei Cardiovascular, Medical, and Research Center, Tehran, Iran, with ischemic-type chest pain and low to intermediate risk for ACS. The patients were divided into 3 groups on the basis of the GRACE score as follows: mild (1-88), intermediate (89-118), and high (119-263). In this study, the low-and intermediate-risk groups were evaluated. The patients underwent coronary CTA after the measurement of troponin I. Those with nonobstructive plaques and mild stenoses (<50% luminal narrowing) were discharged with optimal treatment without further evaluations, those with moderate stenoses (50%-70% narrowing) were discharged with optimal treatment and close follow-ups, and those with severe stenoses (>70% narrowing) underwent coronary angiography. The discharged patients were contacted and their medical records were reviewed to determine the rates of major adverse cardiovascular events (MACE)—consisting of death, myocardial infarction, stroke, hospital admission, and revascularization—at the admission time or within the follow-up duration. Additionally, the correlations between the severity of coronary artery stenoses and plaque characterization and MACE and the GRACE score were assessed. High-risk plaque characterization was defined as a plaque density of less than 30 Hounsfield units, small punctate calcification, napkin-ring signs, and positive remodeling. Patients with a glomerular filtration rate of less than 30 or a history of anaphylaxis to contrast media were excluded. Prospective electrocardiography (ECG) gating was used with 35 mL of Omnipaque contrast media in the patients with heart rates of fewer than 75 bpm and a regular heart rate, while retrospective ECG gating was applied in those with arrhythmias or heart rates of more than 75 bpm. The study protocol was approved by the local ethics committee. The device utilized for CTA was multiple-detector computed tomography Siemens definition force (2 × 192) for coronary CTA. The heart rate was controlled with oral metoral (50-100 mg), and the obtained images were assessed with the Syngo. via software. Coronary arteries were assessed according to the 17-segment model of the American Heart Association. Data analysis was performed among the 77 patients using the SPSS software, version 21.0 (Statistical Procedures for Social Sciences; Chicago, Illinois, USA). The χ2, Fisher, and independent sample t tests were employed, and a P value of less than 0.05 was considered statistically significant. All the patients discharged from the emergency department were contacted via telephone a median of 12 months after the procedure to determine the rates of death, myocardial infarction, stroke, revascularization, and hospital admission for recurrent chest pain. The findings were corroborated by reviewing the medical records.
The mean age of the study population was 49.7 ± 10.1, ranging from 25 to 70 years, and the mean GRACE score was 65.3 ± 19.4, ranging from 23 to 109. There were 41 (53.2%) female patients. A history of hypertension, diabetes, dyslipidemia, and smoking was reported in 39%, 13%, 20%, and 14.3% of the study population, respectively, and a family history of coronary artery disease was reported in 26%. The serum troponin level was abnormal in 15.6% and ST deviation was seen in 31.2% of the patients. A total of 89.6% of the patients were in the low-risk ACS group, and 10.4% of the patients were in the intermediate-risk ACS group based on the GRACE score. There were no significant associations between MACE and the subscales and the GRACE score [Table 1]. The severity of coronary artery stenoses was not associated with the GRACE score (P > 0.05) [Table 2], and nor was there a relationship between the high-risk plaques and the GRACE score [Table 3].
As is demonstrated in [Table 4], the severity of stenoses in the proximal part of the left anterior descending artery (LAD) (P = 0.00), the mid part of the LAD (P = 0.004), and the first part of the obtuse marginal artery (P = 0.004) was associated with MACE. In addition, there were no relationships between MACE and the high-risk plaques [Table 5] and the risk factors (P > 0.05).
In this prospective observational study on 77 patients at low to intermediate risk for ACS, the rate of MACE was 5% (4 of 77 patients). Of those with MACE, 1 patient underwent revascularization at his first admission and the other 3 had readmissions to the hospital due to ACS within our 1-year follow-up. All these 4 events occurred among the patients at a low risk for ACS; there was, however, no significant association between MACE and the subscales and the GRACE score. The severity of coronary artery stenoses was not associated with the GRACE score, while there was a statistically significant association between the severity of coronary artery stenoses and MACE in the proximal part of the LAD (P = 0.00), the mid part of the LAD (P = 0.004), and the first part of the obtuse marginal artery (P = 0.004). Furthermore, we evaluated plaque characterization in the whole study population and found no relationships between the high-risk plaques and either MACE or the GRACE score [Figure 1-1], [Figure 1-2], [Figure 2-1] and [Figure 2-2].
In the current study, we risk-stratified patients at low to intermediate risk for ACS presenting to the emergency department according to their CTA results and those who were treated had good prognoses. In recent years, multiple studies on the role of coronary CTA have been performed among patients with coronary heart disease, whether stable angina or ACS.[10],[11],[12],[13],[14] Initially, the focus of these studies was on cases with stable angina before they turned their attention to patients at low risk for ACS. In the most recent studies, the characteristics of the plaques detected on CTA were studied. In a study by Rubinshtein et al.[12] on 400 patients at low risk for ACS, CTA had a negative predictive value of 97% for the prediction of ACS and MACE in the upcoming 3 months. Hollander et al.[13] showed that patients at low risk for ACS presenting to the emergency department with nonsignificant stenoses (<50%) on CTA had not experienced cardiovascular death or nonfatal myocardial infarction during their 30-day follow-up period. Pundziute et al.[15] reported that plaque composition both on multi-slice computed tomography (MSCT) and virtual histology intravascular ultrasound was identical between the culprit and non-culprit vessels of their patients with ACS and concluded that MSCT might be useful for the noninvasive identification of atherosclerotic plaque patterns associated with a higher risk. Previous research has shown that coronary artery plaques with positive remodeling have a higher lipid content and macrophage count, both of which are markers of plaque vulnerability.[16],[17],[18] Recent years have witnessed multiple studies on the relationship between high-risk plaque characterization and cardiovascular events.[19],[20],[21] Motoyama et al.[19] showed that patients demonstrating positively remodeled coronary segments with low-attenuation plaques on CTA were at a high risk for ACS development over time when compared with patients having lesions without these characteristics. In a study on a large US population of outpatients with stable chest pain, Ferencik et al.[20] reported that high-risk plaques found on coronary CTA were associated with a future MACE and posited that this imaging modality might be an additional risk stratification tool, especially in patients with nonobstructive coronary artery disease, younger patients, and women. In our study on patients at low to intermediate risk for ACS, there was no association between high-risk plaques and MACE. However, the importance of this finding is limited by our low absolute MACE rates.
In the present study on patients at low to intermediate risk for ACS presenting to the emergency department, CTA ruled out significant lesions and optimal treatment was accompanied by good prognoses. Thus, CTA may be deemed an optimal cost-benefit modality for the determination of the diagnosis and therapeutic modality in this group of patients. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.
[Figure 1], [Figure 2], [Figure 3], [Figure 4]
[Table 1], [Table 2], [Table 3], [Table 4], [Table 5]
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