Abstract 16871: Microscopic Systolic Pressure Alternans in Human Cardiomyopathy: Noninvasive Evaluation of a Novel Risk Marker and Correlation with Microvolt T wave Alternans
Introduction: In patients with severe LV dysfunction, visible pulsus alternans accompanies visible T wave alternans, possibly due to abnormal intracellular calcium cycling. However, it is not known if a similar relationship exists between nonvisible microscopic systolic pressure alternans (mSPA) and microvolt TWA (mTWA).
Objective: Our aims were to (i) develop a noninvasive method to measure mSPA, and (ii) determine the prevalence of noninvasive mSPA and its relationship to mTWA in patients with cardiomyopathy.
Methods: Using the spectral method, noninvasive mSPA was measured from finger pressure (Finometer) during incremental atrial pacing, and then validated against invasive mSPA measured from the LV pressure in 12 patients (Controls, LVEF>60%, n=7; Cardiomyopathy, LVEF 31±8%, n=5). In 23 other patients (age 55±10 y, LVEF 29±6%), finger mSPA and ECG-based mTWA were measured simultaneously during incremental atrial pacing.
Results: LV mSPA was detected in 80% of patients with cardiomyopathy and 43% of controls. The presence of finger mSPA showed 100% positive concordance with LV mSPA, however finger MSPA was 20% larger due to peripheral augmentation. Finger mSPA was highly concordant (96% positive and 90% negative concordance) with mTWA. The magnitudes of finger mSPA (SPalt) and mTWA (Valt) showed a linear correlation (R=0.66, p<0.001) with increasing pacing rate (see table). The k value, a measure of signal to noise ratio, was significantly larger for finger mSPA vs. mTWA. Premature beats resulted in concordant and coincident changes in finger mSPA and mTWA. In followup (454±274 days), 2 (8.6%) patients experienced ventricular tachycardia, and both manifested finger mSPA and mTWA during pacing at 100 bpm.
Conclusions: mSPA (< 1 mmHg) can be detected noninvasively in patients with cardiomyopathy and is coupled to mTWA, suggesting a common mechanism. The high signal to noise ratio of mSPA may provide a novel robust metric of sudden cardiac death risk in these patients.
- © 2010 by American Heart Association, Inc.