Increased beat-to-beat QRS amplitude variability in patients with congestive cardiac failure.

In patients with ischemic heart disease, dobutamine provoked-stress increases beat-to-beat QRS amplitude variability, which may be due to an electrical instability of the myocardium. Our results in this pilot study showed that patients with congestive heart failure had significantly higher beat-to-beat QRS amplitude variability compared to controls in resting supine posture. This may partly be due to myocardial disease or irregular respiration in this patient group.