Efficacy and Comparison of 256-Slice Dual Source CT Angiography with Catheter Coronary Angiography at Different Heart Rates without using Beta Blockers

Abstract

Introduction: Coronary Artery Disease (CAD) is a leading cause of morbidity and mortality in India as well as worldwide. CT angiography is an excellent imaging modality for evaluation of CAD. Previous studies with 64 or lesser slice CT scanner have failed to show consistent and optimal Image Quality (IQ) at Heart Rate (HR) more than 70 bpm and required beta blockers. Aim: To evaluate the diagnostic accuracy of 256-slice Dual Source CT Angiography (DSCTA) in comparison with Catheter Coronary Angiography (CCA) in evaluation of Coronary Arteries (CA) in patients with clinical suspicion of CAD and to study its effectiveness at higher HR without using beta blockers. Materials and Methods: This cross-sectional study was conducted on patients (n=46) with suspected CAD using ECG triggered 256-slice Dual Source Computed Tomography (DSCT) over a period of nine months. Patients were sub grouped according to HR (Group I: 50-70 (18 patients), Group II: 71-90 (24 patients) and Group III ≥91 (8 patients). A total of 48% patients had HR of 71-90 bpm while 16% had HR ≥91 bpm. Scan protocols included prospective ECG triggering (HR <75 bpm) and retrospective spiral scan protocols (HR >75 bpm). CA segments were analysed for IQ on a 4 point scale (1 is worst while 4 is best) by two independent readers who were blinded to the patient details. Accuracy to detect significant luminal stenosis was correlated with CCA (gold standard). Statistical significance of the study was established by Chi-square test (p<0.05). Results: The mean HR and Standard Deviation (SD) in the study was 76±13.7 bpm (range 54-105). Out of 675 CA segments analysed mean IQ score and SD in medium (71-90 bpm) and high HR (≥91 bpm) groups were 3.55±0.62 and 3.25±0.62 which were comparable to IQ in low HR group (3.84±0.36). This indicates excellent IQ even at HR of ≥91 bpm (p<0.05). The mean IQ score of entire study group was 3.88±0.33. Right Coronary artery (RCA) showed best IQ score in each category followed by Left Anterior Descending (LAD) and Left Circumflex (LCX). Inter-observer agreement analysis was performed using Kappa analysis to determine agreement between DSCTA readers. Kappa values for low, medium and high HR groups were 0.866, 0.842 and 0.836. The sensitivity, specificity, Positive Predictive Value (PPV), Negative Predictive Value (NPV) and accuracy for detecting significant stenosis in medium and high HR groups were 95%, 99.2%, 98.4%, 98.7%, 98.9% and 94.3%, 98.9%, 96.9%, 97.6%, 97.9%, respectively. Conclusion: 256-slice DSCTA is a reliable technique with high sensitivity, specificity, PPV and NPV for assessment of CA even at higher HR without using beta blockers.