Comparative Evaluation of Ankle–Brachial Index, Thrombolysis in Myocardial Infarction, and SYNTAX Scores in Predicting the Severity of Coronary Artery Disease

INTRODUCTION

Coronary artery disease (CAD) remains a major global cause of morbidity and mortality. Early identification of disease severity is essential for optimizing management and improving outcomes. The ankle–brachial index (ABI) is a simple, non-invasive indicator of peripheral arterial disease (PAD) and systemic atherosclerosis, while the thrombolysis in myocardial infarction (TIMI) risk score predicts adverse cardiovascular events in acute coronary syndromes (ACS) using clinical parameters. The Synergy Between Percutaneous Coronary Intervention with Taxus and Cardiac Surgery score (SYNTAX), derived from coronary angiography, quantifies lesion complexity and guides revascularization decisions. Although each tool offers distinct prognostic value, few studies have compared their relative performance in predicting angiographic severity. This study aimed to evaluate and correlate ABI, TIMI, and SYNTAX scores in patients with angiographically proven CAD to determine their association with the extent of coronary vessel involvement.

MATERIAL AND METHODS

RESULTS

A total of 80 patients with angiographically confirmed CAD were analyzed. The majority were male (67.5%), with the most common age group being 51–60 years (43.75%), followed by 61–70 years (27.5%). Major cardiovascular risk factors included diabetes mellitus (60%), hypertension (56.25%), dyslipidemia (61.25%), and smoking (62.5%). A family history of CAD was noted in 3.25% of cases.

As summarized in Table 1, the left anterior descending artery was the most frequently involved vessel (68.75%), followed by the left circumflex (63.75%) and right coronary artery (61.25%). Based on angiographic assessment, 31 patients (38.75%) had SVD, while 49 patients (61.25%) had MVD, including double (27.5%) and triple-vessel disease (33.75%). This distribution indicates a substantial burden of diffuse atherosclerosis in the study population.

Patients were grouped based on TIMI scores (<4 and ≥4) [Table 2]. Among those with a TIMI score <4, 29 patients (67.4%) had SVD, while 14 (32.6%) demonstrated MVD. Conversely, in the TIMI ≥ 4 group, only 2 patients (5.4%) had SVD, whereas 35 (94.6%) exhibited MVD. The association between the TIMI score and angiographic disease pattern was highly significant (χ² = 29.68, P < 0.001), indicating that higher TIMI scores correlate strongly with more extensive coronary involvement. Higher TIMI scores were significantly associated with MVD (P < 0.001).

Table 3 shows that among 80 patients, 45 (56.3%) had an ABI > 0.9 and 35 (43.7%) had an ABI ≤ 0.9. Among patients with TIMI < 4, 69.8% had normal ABI (>0.9), whereas among those with TIMI ≥ 4, 59.5% had reduced ABI (≤0.9). The association between ABI and TIMI score was statistically significant (χ² = 6.903, P < 0.01), indicating that lower ABI values were significantly associated with higher TIMI scores, reflecting greater cardiovascular risk.

Table 4 shows that ABI ≤ 0.9 was strongly associated with multivessel involvement (91.4%), compared to 37.8% among those with ABI > 0.9 (χ² = 21.67; P < 0.001). Only 8.6% of patients with low ABI had SVD, indicating that reduced peripheral perfusion mirrors widespread coronary atherosclerosis.

When ABI and SYNTAX scores were analyzed together, a significant association was found. Among patients with ABI > 0.9, 32 (56.8%) had SYNTAX > 22, whereas among those with ABI ≤ 0.9, 17 (43.2%) had SYNTAX > 22. This relationship (χ² = 9.40, P < 0.001) highlights that patients with low ABI are more likely to have higher SYNTAX scores, indicating that peripheral atherosclerosis parallels coronary lesion complexity [Table 5].

The TIMI risk score has a sensitivity of 93.5% and a specificity of 71.4%; ABI has a sensitivity of 90.3% and specificity of 65.3% in predicting MVD.

DISCUSSION

This study provides a comparative evaluation of three well-established indices, the ABI, TIMI risk score, and SYNTAX score in assessing the extent and severity of CAD. ABI represents systemic atherosclerotic burden, TIMI indicates the severity of clinical and ischemic presentation, and SYNTAX measures coronary lesion complexity, together providing a comprehensive assessment of cardiovascular risk from vascular, clinical, and anatomical standpoints.

In this cohort, majority of the patients were male (67.5%), and in the 51–60-year age group, consistent with global data indicating an earlier and higher prevalence of CAD in men.^[1,2] Traditional cardiovascular risk factors such as diabetes mellitus (60%), hypertension (56%), dyslipidemia (61%), and smoking (62%) were highly prevalent, in line with the observations of many earlier studies emphasizing the multifactorial atherosclerotic background of CAD.^[3-5]

The ABI, a simple, inexpensive, and non-invasive tool, has been extensively validated as a surrogate marker of systemic atherosclerosis. ABI is not merely a marker of PAD, but reflects global atherosclerotic load and endothelial dysfunction, both of which contribute directly to more extensive coronary involvement. Because ABI captures chronic arterial remodeling, impaired perfusion, and arterial stiffness, it provides insight into long-standing vascular pathology, which is not confined to peripheral arteries but represents systemic vascular pathology. Multiple epidemiological studies, including those by Criqui et al.,^[6] the cardiovascular health study^[7] and the Edinburgh artery study,^[8] demonstrated that ABI ≤ 0.9 is associated with significantly increased cardiovascular mortality and morbidity. In the present study, ABI ≤ 0.9 was found in 43.7% of patients and was significantly associated with multivessel CAD (91.4%, P < 0.001). These findings corroborate the results of Papamichael et al.,^[9] Myslinski et al.,^[10] and Sarangi et al.,^[11] who reported that low ABI values predict a greater burden of coronary atherosclerosis. The high sensitivity (90.3%) and acceptable specificity (65.3%) of ABI in predicting multivessel CAD in the current study further reinforce its diagnostic utility as a marker of systemic vascular compromise, which is also consistent with previous studies.^[1,12]

The TIMI risk score, although designed primarily for outcome prediction in ACSs, has demonstrated strong associations with angiographic findings.^[13,14] In this study, patients with TIMI ≥ 4 had a markedly higher prevalence of MVD (94.6%) compared with those with TIMI < 4 (32.6%, P < 0.001). These results are consistent with those of Khandelwal et al.,^[15] Hussein et al.,^[2] and Namazi et al.,^[16] who also reported significant correlations between TIMI score and the anatomical extent of CAD. García et al.^[17] found that higher TIMI scores were associated with a greater likelihood of left main or three-vessel disease, reinforcing the utility of this score as a quick bedside predictor of disease burden.

The SYNTAX score, which quantifies the complexity of coronary lesions based on angiographic parameters, also showed significant associations with both ABI and TIMI scores in this study (P < 0.001). Patients with higher SYNTAX scores (>22) were more likely to have low ABI and high TIMI values, indicating a parallel relationship between systemic atherosclerosis and coronary lesion complexity. Similar observations were made in earlier studies^[18,19] that demonstrated a correlation between higher SYNTAX scores and low ABI with more diffuse and complex coronary involvement. However, Pettracco et al.,^[20] and Benyakorn et al.^[21] found only modest correlations, possibly due to differences in population characteristics and the prevalence of comorbidities.

While both ABI and TIMI scores showed significant correlation with the angiographic severity of disease, the TIMI score demonstrated slightly better sensitivity and specificity, likely due to its inclusion of dynamic clinical, electrocardiogram, and biomarker indicators of coronary ischemia. In contrast, ABI reflects peripheral arterial status and can be affected by non-coronary factors such as arterial calcification, limiting its precision. Nonetheless, ABI continues to serve as a useful screening and prognostic tool, especially in settings with limited access to advanced diagnostic testing due to its simplicity and objectivity, enabling early identification of high-risk individuals even before invasive testing.^[22] While ABI measures long-term vascular burden, TIMI measures the dynamic physiological impact of coronary obstruction during ACSs.^[23]

CONCLUSION

From a clinical perspective, the current results indicate that integrating clinical (TIMI), non-invasive (ABI), and angiographic (SYNTAX) evaluations provides a more thorough assessment of CAD severity. Integrating these three scoring systems could strengthen risk stratification and guide therapeutic planning. In resource-limited settings, ABI provides an easily obtainable estimate of systemic atherosclerotic burden and can help identify high-risk patients even before invasive testing. Patients showing low ABI (≤0.9), elevated TIMI (≥4), and high SYNTAX (>22) constitute a high-risk subgroup requiring aggressive management strategies.