P-Wave Morphology in Focal Atrial Tachycardia

OBJECTIVES: The purpose of this study was to perform a detailed analysis of the P-wave morphology (PWM) in focal atrial tachycardia (AT) and construct and prospectively evaluate an algorithm for identification of the anatomic site of origin. BACKGROUND: Although smaller studies have described the PWM from particular anatomic locations, a detailed algorithm characterizing the likely location of a tachycardia associated with a P-wave of unknown origin has been lacking. METHODS: The PWMs for 126 consecutive patients undergoing successful radiofrequency ablation of 130 ATs are reported. P waves were included only when the onset was preceded by a discernible isoelectric segment. P waves were classified as positive (+), negative (-), isoelectric, or biphasic. Sensitivity, specificity, and predictive values were calculated. On the basis of these results, an algorithm was constructed and prospectively evaluated in 30 new consecutive ATs. RESULTS: The distribution of ATs was right atrial (RA) in 82 of 130 (63%) and left atrial (LA) in 48 of 130 (37%). Right atrial sites included crista (n = 28), tricuspid annulus (n = 29), coronary sinus (CS) ostium (n = 14), perinodal (n = 7), right septum (n = 1), and RA appendage (n= 3). Left atrial sites included pulmonary veins (n = 32), mitral annulus (n = 8), CS body (n= 3), left septum (n = 3), and LA appendage (n = 2). In electrocardiographic lead V1, a negative or +/- P-wave demonstrated a specificity of 100% for a RA focus, and a + or -/+ P-wave demonstrated a sensitivity of 100% for a LA focus. A characteristic PWM was associated with high sensitivity and specificity at common atrial sites for tachycardia foci. A P-wave algorithm correctly identified the focus in 93%. CONCLUSIONS: Characteristic PWMs corresponding to known anatomic sites for focal AT are associated with high specificity and sensitivity. A P-wave algorithm correctly identified the site of tachycardia origin in 93%.