Increase in the QRS duration after amelioration of peripheral edema and after hemodialysis.

Association among weights, amplitude of QRS complexes, and QRS duration in patients with peripheral edema has been described. This study explored whether increase in QRS duration occurs with amelioration of peripheral edema or after hemodialysis. Sums of the amplitudes of the 12 electrocardiographic leads and corresponding QRS duration were measured in 12 patients with peripheral edema before and after loss of weight, in 28 patients with a critical illness but without change in their weight ("controls"), and in 1 patient before and after hemodialysis. QRS duration increased from 90.1+/-25.0 milliseconds to 101.7+/-25.8 milliseconds (P=.001) in patients with peripheral edema, was unchanged in the controls, and increased from 87.8+/-5.9 milliseconds before to 92.7+/-6.7 milliseconds after hemodialysis (P=.007). It is proposed that these increases in QRS duration are only apparent (not electrophysiologically real), representing an extracardiac phenomenon mediated by alterations in the composite impedance of the passive body volume conductor, resulting in measurement of augmented QRS complexes after fluid removal. The clinical implications for patients with congestive heart failure are discussed.