P5975Diminished LV systolic velocity on tissue Doppler imaging is linked to an amplified risk of lethal arrhythmias independently of LV ejection fraction

Abstract

Background
Life threatening arrhythmias (LTA) can trigger sudden cardiac death, or provoke implantable cardioverter defibrillator (ICD) discharges that escalate morbidity and mortality. Longitudinal myofibrils predominate in the subendocardium which is uniquely sensitive to arrhythmogenic triggers.

Objectives
To test the hypothesis that mitral annular systolic velocity (S'), a tissue Doppler index of LV long-axis systolic function, might predict lethal arrhythmias irrespective of LVEF.

Methods
We analysed data from diverse ICD and cardiac resynchronization therapy defibrillator (CRT-D) patients at 2 London centres. Channelopathies were excluded. S' was averaged from medial and lateral mitral annuli velocities. Primary outcome was time to sustained ventricular tachycardia (VT) or fibrillation (VF) needing device therapy.

Results
In 302 patients (mean age 68 years, LVEF 32%, 77% male, 52% ischemic, 35% primary prevention, and 53% CRT-D), median S' was 5.1 (IQR: 4.0–6.2) cm/s and lower in CRT-D than ICD subjects. After a median follow-up of 15 months, 56 (19%) subjects had LTA and those who did had a lower S' than those who did not (4.6±1.4 cm/s vs. 5.4±1.7 cm/s, P=0.003-Fig A). Each 1cm/s lower S' correlated to a 43% increased risk of LTA (HR: 0.70, 95% CI: 0.57–0.87, P=0.001) independently of age, gender, β-blocker use, centre, ICD use and LVEF. Adding S' to the baseline model improved net reclassification (P=0.02) implying incremental utility (Fig B). An S' ≤5.6cm/s was the best cut-off, conferring a 2.4-fold higher LTA risk than an S'>5.6 cm/s (95% CI: 1.17–4.37, P=0.02–Fig C).

Conclusion
A lower S' forecasts an enhanced probability of LTA in cardiac device recipients irrespective of LVEF, and could be used to titrate medical, device and ablative therapies to mitigate future arrhythmic risk.