Please click here to obtain permission to reproduce this image.
Click on image to view larger version.
Figure 1 Ventricular AP Alternans
This 59-year-old man had ischemic cardiomyopathy and left ventricular ejection fraction (LVEF) of 20%. (A) Pacing at 109 beats/min; (B) action potential duration (APD) shows minimal oscillations over time. However, when 64 consecutive beats were superimposed, (C) action potential (AP) amplitude shows marked alternans, shown by the separation of even (blue line) and odd (red line) beats. (D) AP amplitude alternans (k-score = 10.4, absolute voltage of alternation [Valt] = 175 µV) is depicted on this spectrum across beats, as peak magnitude at 0.5 cycles/beat. (E) T-wave alternans (TWA) is positive at this time (gray areas) in X, Y, and vector magnitude (Vm) leads, with low levels of bad beats and noise, and no confounding respiratory (Resp), heart rate (HR), or RR-interval alternans. FFT = fast-Fourier transform; MAP = monophasic action potential; RV = right ventricle.
|
