Clinical Electrophysiology -> SCA Risk Assessment: -> Signal Processing Techniques (SAECG/TWA, HRV, QT interval) D-AB11 - Emerging Innovations to Predict Sudden Death (ID 18) Abstract Plus

D-AB11-02 - Microvolt QRS Alternans Without Microvolt T Wave Alternans In Human Cardiomyopathy: A Novel Risk Marker Of Late Ventricular Arrhythmias (ID 740)


 A.M. Suszko: Nothing relevant to disclose.

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Background: Action potential alternans can induce VT/VF, and manifest on the surface ECG as T wave alternans (TWA) and QRS alternans (QRSA). Unlike microvolt TWA, microvolt QRSA has not been well characterized.
Objective: To evaluate microvolt QRSA in cardiomyopathy patients in relation to microvolt TWA and VT/VF outcomes.
Methods: Prospectively enrolled patients (n=100, age 62±11yrs, LVEF 27±7%) with primary ICDs had digital 12-lead ECGs recorded during ventricular pacing from 100-120 bpm. QRSA, TWA and noise were quantified in moving 128-beat segments using the spectral method. Each segment was categorized as QRSA+ and/or TWA+ based on ≥2 precordial leads having Valt>0 and k>3. Patient were similarly categorized based on having ≥3 segments with alternans. The clinical endpoint was appropriate ICD therapy or sustained VT/VF in follow up.
Results: In patients with low noise ECGs (n=95), 48% were TWA+ and 44% were QRSA+. TWA+ and QRSA+ occurred together in 31% of patients and alone in 18% and 14% of patients, respectively. TWA magnitude (1.4±0.4 vs 4.7±1.0µV, p<0.01) and proportion of TWA+ studies (16 vs 46%, p<0.01) increased with rate but QRSA did not change. At 3.5yrs follow up, 19% of patients had an event. The VT/VF event rate was greater in QRSA+ vs QRSA- patients but similar in TWA+ vs TWA- patients, with QRSA+/TWA- patients having the highest event rate (Figure 1). A Cox model including age, QRSd and QRSA+ revealed QRSA+ (4.0 [1.2-13.0], p=0.02) and QRSd (1.2 [1.0-1.4] per 10ms, p=0.02) to predict events.
Conclusion: Microvolt QRSA is prevalent in 44% of cardiomyopathy patients and does not exhibit rate dependence. QRSA can exist without TWA and is associated with a 4-fold increased risk of VT/VF.