1027-42 Usefulness of T wave ″Humps″in the Diagnosis of Long QT Syndrome

Abstract

Family members of long QT syndrome (LQTS) prebands, who present with QTc ≥0.47 sec 1/2 , are diagnosed as LQTS affected. It remains unclear, however, how to evaluate family members with borderline QTc value (0.42–0.46 see 1/2 ). Recent ECG and genetic linkage correlation studies suggest that T wave ″humps″ (defined as bulges or protuberances just beyond the apex on the downslope of the T wave) in left precordial or limb leads may represent an ECG marker of the LQTS genotype. Therefore, the aim of this study was to investigate the clinical significance of T wave humps (in at least 1 limb or 2 left precordial leads) in 427 family members with borderline QTc in their rust ECG. The occurrence of cardiac events (syncope, cardiac arrest) or QTc≥0.47 sec 1/2 during a mean 46 ± 28 mo. follow-up was used as a basis to diagnose family member as LQTS-affected. The presence of T wave humps, recorded in 45 (11%) family members, was significantly associated with younger age (for ≤15 vs > 15 years old, odds ratio [OR] = 6.0; p < 0.001), longer QTc (0.45–0.46 vs 0.42–0.44, OR = 3.8; p < 0.001) and higher heart rate (>80 vs ≤80 bpm, OR = 2.8; p < 0.02). The diagnosis of LOTS was attained in 36% of family members with and in 14% without T wave humps (p < 0.001). Multivariate logistic regression revealed an independent contribution of T wave humps to the LQTS diagnosis: ECG Variable OR 95%CI pValue T wave humps (yes vs no) 3.1 (1.5;6.6) 0.003 QTc(>0.44–0.46 vs≤0.44) 5.6 (3.2;9.9) <0.001 Bradycardia (age-adjusted) 3.6 (1.8;7.3)≤ <0.001 In LQTS family members with borderline QTc: (1) T wave humps are more likely to occur in individuals at young age, with longer QTc and at higher heart rates. (2) The diagnosis of LQTS is enhanced by identification of T wave humps for the entry ECG.