European Journal of Cardiovascular Medicine

Preservation of left ventricular (LV) systolic function through timely medical or interventional therapy remains a key priority in the management of coronary artery disease (CAD) ^[1]. Conventional two-dimensional (2D) echocardiography primarily detects CAD by identifying regional wall motion abnormalities or by demonstrating a reduction in left ventricular ejection fraction (LVEF). However, these changes often appear late in the disease process and may not be evident in the early stages ^[2]. This limitation highlights the need for more sensitive and reliable parameters to diagnose subtle LV dysfunction at an earlier phase.

Speckle tracking echocardiography (STE) has emerged as an advanced imaging modality that allows detailed evaluation of both global and regional myocardial function. Among the indices derived from STE, global longitudinal strain (GLS) has proven to be the most accurate and sensitive marker for early systolic dysfunction ^[3]. Unlike conventional echocardiographic indices, GLS quantifies myocardial deformation, providing precise insights into myocardial mechanics. Its advantage lies in being angle-independent, thereby enabling reproducible assessment of myocardial strain and torsion, even in subtle disease states ^[4].

In CAD, longitudinal function is typically affected before radial or circumferential function. Thus, impairment of longitudinal strain can serve as the earliest indicator of ischemia. Particularly in patients with significant coronary stenosis, where recurrent episodes of ischemia may cause subclinical myocardial stunning, GLS can unmask dysfunction that conventional echocardiography may miss ^[5-7]. This makes GLS a powerful tool for the non-invasive evaluation of myocardial performance, with potential applications in both resting and stress conditions to assess myocardial viability.

In parallel, angiographic scoring systems are widely used to estimate the severity and complexity of CAD. The Synergy between Percutaneous Coronary Intervention with Taxus and Cardiac Surgery (SYNTAX) score (SS) is one of the most recognized indices for quantifying atherosclerotic burden and describing coronary anatomy. It incorporates lesion characteristics, site, and complexity, thereby providing both prognostic and therapeutic guidance ^[8]. Higher SYNTAX scores are typically associated with complex coronary anatomy and poorer outcomes in patients undergoing percutaneous coronary intervention (PCI).

Although both GLS and the SYNTAX score offer valuable insights—one from functional and the other from anatomical perspectives—their correlation has not been adequately studied in the Indian population. Understanding the relationship between GLS, as a sensitive functional marker, and SYNTAX score, as an established anatomical measure, may allow clinicians to integrate non-invasive imaging with angiographic findings for better risk stratification.

Given the limited literature from India, this study was designed to evaluate the association between GLS measured by 2D STE and the SYNTAX score in patients presenting with stable angina pectoris who had preserved LV systolic function

This hospital-based prospective cross-sectional observational study was conducted in the Department of Cardiology at our tertiary care hospital. A total of 57 patients aged >18 years with stable angina pectoris, preserved left ventricular ejection fraction (LVEF ≥55%), and scheduled for elective coronary angiography following a positive treadmill stress test were included. The sample size was calculated at a 95% confidence interval and 5% α error using the formula N = [(Z 1-α/2)² × pq] / d², based on the accuracy of GLS in predicting high SYNTAX score reported by Hardas S et al., which yielded 57 patients.

Patients with acute myocardial infarction, unstable angina, congestive heart failure, atrial fibrillation, bundle branch blocks, persistent arrhythmias, frequent ectopics, connective tissue disease, thyroid dysfunction, chronic renal failure (GFR <60 mL/min/1.73 m²), pericarditis, myocarditis, valvular heart disease, or <50% luminal obstruction in vessels ≥1.5 mm on angiography were excluded.

All participants underwent detailed history, physical examination, electrocardiography, and echocardiography. Echocardiographic evaluation was performed using a PHILIPS EPIQ CVx cardiovascular ultrasound system (Philips Medical Systems, Andover, USA) with an X5-1 matrix array transducer. Conventional 2D echocardiography and 2D speckle tracking echocardiography (STE) were carried out, and global longitudinal strain (GLS) was obtained from digitally stored images at rest.

All patients underwent coronary angiography via femoral or radial access. Quantitative coronary angiography (QCA) was performed, and the SYNTAX score (SS) was calculated using the online calculator(http://www.syntaxscore.com/calc/start.htm). Patients were stratified into three groups: no CAD/low SS (0–22), moderate SS (23–32), and high SS (≥32).

Data were analyzed using SPSS software version 24.0. Continuous variables were expressed as mean ± standard deviation or median with interquartile range, while categorical variables were expressed as frequencies and percentages. Comparisons between groups were made using independent t-tests for continuous variables. Spearman’s correlation coefficient was calculated between GLS and SYNTAX score, and receiver operating characteristic (ROC) curve analysis was used to determine the predictive accuracy of GLS for critical CAD. A p-value <0.05 was considered statistically significant.

Ethical approval was obtained from the Institutional Ethics Committee, and written informed consent was obtained from all participants prior to enrollment

The study population comprised 57 patients with stable angina pectoris, with a mean age of 56.8 ± 8.9 years and male predominance (59.6%). Hypertension was the most common comorbidity (47.4% either alone or in combination with diabetes), while 43.9% had no comorbidities. All patients had preserved left ventricular ejection fraction (mean 56.3 ± 2.6%), with mean global longitudinal strain of 18.0 ± 2.7%. Diastolic dysfunction was present in 63.2% of patients as assessed by tissue Doppler.

The majority of patients (77.2%) had low SYNTAX scores (0-22), while 19.3% had intermediate scores (22.1-32) and 3.5% had high scores (>32). Most echocardiographic parameters showed no significant differences across SYNTAX score categories. However, global longitudinal strain demonstrated a statistically significant progressive deterioration with increasing SYNTAX score severity (18.7 ± 2.4% in low, 15.5 ± 1.8% in intermediate, and 14.3 ± 0.6% in high SYNTAX score groups; p<0.001).

Global longitudinal strain showed a strong negative correlation with SYNTAX score (r = -0.650, p<0.001), indicating that worsening strain values were associated with higher coronary complexity. Additionally, GLS demonstrated a significant positive correlation with left ventricular ejection fraction (r = 0.357, p = 0.006). No significant correlations were observed between GLS and other clinical or echocardiographic parameters.

ROC curve analysis revealed that global longitudinal strain had excellent diagnostic accuracy for predicting critical coronary artery disease, with an area under the curve of 0.884 (95% CI: 0.785-0.982, p<0.001). The optimal cut-off value of ≤16.9% yielded a sensitivity of 79.5% and specificity of 92.3%. At this threshold, the positive predictive value was 84.6% and negative predictive value was 89.3%, with an overall diagnostic accuracy of 87.7%.

Table 1: Demographic and Clinical Profile of the Study Population (N=57)

Table 2: Distribution of Mean Echo Parameters According to SYNTAX Score Categories

Table 3: Correlation Between Global Longitudinal Strain and Study Variables

Significant correlations (p<0.05) are shown in bold

Table 4: ROC Characteristics of Global Longitudinal Strain for Predicting Critical CAD

Figure 1: ROC curve characteristics

Our study population characteristics, with a mean age of 56.8 years and male predominance (59.6%), are representative of typical stable angina cohorts. The preserved LVEF in all patients (mean 56.3%) emphasizes the clinical relevance of strain imaging in detecting early myocardial dysfunction when conventional parameters remain normal. This finding supports the concept that GLS can identify subclinical left ventricular impairment related to ischemic burden before the development of wall motion abnormalities detectable by visual assessment.

The present study demonstrates a strong negative correlation between global longitudinal strain and SYNTAX score (r = -0.650, p<0.001) in patients with stable angina pectoris, establishing GLS as a valuable non-invasive predictor of coronary artery disease complexity. These findings align with previous research while offering unique insights into the clinical utility of strain imaging in cardiovascular risk assessment.

Our correlation coefficient of -0.650 falls within the range reported by other investigators, though with notable variations. Abdelrazek et al.^[8] reported a stronger correlation (r = -0.83), while Vrettos et al.^[9] found a more modest association (r = 0.62). The differences in correlation strength may be attributed to variations in study populations, imaging protocols, and SYNTAX score categorization methods. Our intermediate correlation value suggests a robust but not absolute relationship, which is clinically realistic given the multifactorial nature of coronary artery disease.

The progressive deterioration of GLS values across SYNTAX score categories in our study (18.7% in low, 15.5% in intermediate, and 14.3% in high-risk groups) demonstrates a clear dose-response relationship. Hardas et al.^[10] reported similar findings with GLS values of 18.7%, 16.4%, and 12.4% across their respective SYNTAX categories. The consistency of these findings across different populations reinforces the validity of GLS as a graded marker of coronary disease severity. However, our high-risk group showed less severe impairment (14.3%) compared to Hardas et al.^[10] (12.4%), possibly due to our smaller sample size in the high SYNTAX category (n=2) or differences in patient selection criteria.

Our ROC analysis revealed an area under the curve of 0.884, indicating excellent diagnostic accuracy for predicting critical coronary artery disease. This performance is comparable to Hardas et al.^[10] (AUC = 0.985) and superior to the systematic review by Norum et al.,^[11] which reported AUCs ranging from 0.68 to 0.80. The higher diagnostic accuracy in our study and that of Hardas et al.^[10] may reflect more homogeneous study populations with stable angina, whereas systematic reviews often include diverse patient cohorts with varying clinical presentations.

The optimal cut-off value of ≤16.9% in our study yielded high sensitivity (79.5%) and excellent specificity (92.3%). This threshold differs from other reported values, which range from 13.95% to 19.7%. Hardas et al.^[10] used a cut-off of 16.0% with 100% sensitivity but lower specificity (64.0%), while Vrettos et al. [9] reported a cut-off of 13.95% with 71% sensitivity and 90% specificity. The variation in optimal cut-off values across studies likely reflects differences in population characteristics, imaging equipment, and analytical software. Our cut-off provides a balanced approach with high specificity, making it particularly useful for ruling in significant coronary disease.

The diagnostic performance characteristics in our study showed promising clinical utility, with a positive predictive value of 84.6% and negative predictive value of 89.3%. These values compare favorably with those reported by Madhavan et al. [12] (PPV 84%, NPV 90%) and are superior to some other studies. The high negative predictive value is particularly valuable in clinical practice, as it suggests that patients with GLS values above the cut-off threshold are unlikely to have critical coronary artery disease.

An important finding in our study was the independent association between GLS and coronary disease severity, with minimal correlation observed between GLS and other clinical or echocardiographic parameters except for LVEF. This contrasts with Hardas et al.,^[10] who found significant correlations between GLS and left ventricular dimensions. The independence of GLS from traditional echocardiographic parameters suggests its unique value as a marker of subclinical myocardial dysfunction before the development of overt systolic impairment.

The limitations of our study include the relatively small sample size, particularly in the high SYNTAX score category, which may limit the generalizability of our findings

In conclusion, our findings demonstrate that global longitudinal strain is a reliable non-invasive marker for assessing coronary artery disease complexity in patients with stable angina pectoris. The excellent diagnostic accuracy and independence from conventional echocardiographic parameters support its clinical utility as an adjunctive tool in risk stratification. The consistency of our results with previous research, despite some methodological differences, reinforces the robustness of strain imaging in contemporary cardiovascular practice

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