Artificial attenuation of ECG voltage produces shortening of the corresponding QRS duration: Clinical implications for patients with edema

Background: Prolonged QRS duration (QRSd) is a useful index for the management of patients with congestive heart failure (CHF). QRSd is affected by changes in the ECG voltage (ECGV) in the context of development and amelioration of peripheral edema (PERE), independent of underlying pathology. Nowadays, physicians accept QRSd measured by computer techniques. The latter offers the possibility of testing the hypothesis that artificial alteration of the ECGV, simulating effects of PERE, could lead to changes in the QRSd. Methods: To this end, voltage was attenuated by 25%, 50%, and 75% in 100 digital ECGs recorded from normal subjects and in 20 patients with complete left bundle branch block (LBBB), by merely increasing the calibration strength by 4/3, 2, and 4, respectively, and by using the same data. Results: All ECGs were analyzed by the same computer program and this led to a reduction of global QRSd by 2.3 ± 2.9%, 5.7 ± 4.0%, and 11.9 ± 6.2%, respectively, in the normal subjects, and 1.6 ± 1.4%, 3.4 ± 1.7%, and 8.2 ± 3.6%, respectively, in the patients with LBBB. Correlation of the percent change in the global QRSd and the percent change in ECGV was good with an r = 0.65, and P = 0.00005 in the normal subjects, and an r = 0.74 and P = 0.00005 in the patients with LBBB. Conclusions: Apparent shortening in QRSd as a function of ECGV attenuation due to PERE could have implications in the follow-up of patients with CHF, and their selection for implantable cardioverter/ defibrillators, or cardiac resynchronization therapy.