Coronary sinus diameter by echocardiography to differentiate atrioventricular nodal reentrant tachycardia from atrioventricular reentrant tachycardia

BACKGROUND: Coronary sinus (CS) has been shown to be larger in patients with atrioventricular nodal reentrant tachycardia (AVNRT). We sought to determine if echocardiographically measured CS diameter can help identify the mechanism of tachycardia in patients with narrow complex tachycardia without preexcitation before the invasive electrophysiology study. METHODS: Forty four patients with documented narrow complex, short RP tachycardia who were scheduled for an electrophysiology study were included. Based on the electrophysiology study, patients were divided into those with AVNRT and those with a concealed accessory pathway and atrioventricular reentrant tachycardia (AVRT). Proximal CS diameter (CSp) measured at the ostium and mid CS diameter (CSm) 1 cm distal to the ostium using transthoracic echocardiography. RESULTS: CSp was significantly larger in patients with AVNRT than AVRT (14.1 ± 5 vs. 9.9 ± 2 mm, p < 0.0001). CSm diameter was not significantly different between the two groups. A cut-off of CSp > 11.2 mm identified AVNRT with a sensitivity of 92.6% and specificity of 76.9%. CSp was a better discriminant (AUC 0.89, 95% CI 0.75-0.97) compared to age (AUC 0.74, 95% CI 0.58-0.87) or tachycardia rate (AUC 0.60, 95% CI 0.44-0.76). CONCLUSIONS: Echocardiographic measurement of the diameter of CS ostium can help in identifying the mechanism of the tachycardia before the invasive electrophysiology study.