Modulation of cardiac ventricular conduction: Impact on QRS duration, amplitude and dispersion.

Alterations in cardiac impulse conduction may exert both beneficial and detrimental effects. The assessment of ventricular conduction properties is of paramount importance both in clinical and in experimental settings. Currently the duration of the QRS complex is regarded as hallmark of in-vivo assessment of global ventricular conduction time. In addition, the amplitude of the QRS complex has been suggested to reflect ventricular conduction time in man and in rats. Here, for the first time, we systematically investigated the relationship between QRS duration ("QRS") and QRS amplitude ("RS-height"; RSh) in the murine ECG obtained during anesthesia. In mice harbouring a homozygous knockout of the transmembrane protein podoplanin (PDPN-/-; n = 10) we found both a shorter QRS and a greater RSh than in wild-type animals (n = 13). In both genotypes cumulative i.p. administration of 5 mg/kg and 10 mg/kg of the Na channel blocker flecainide resulted in dose-dependent QRS increase and RSh decrease, whereby the drug-induced changes in RSh were greater than in QRS. In both genotypes the flecainide-induced changes in QRS and in RSh were significantly correlated with each other (R = -0.56, P = 0.004). Whereas dispersion of QRS and RSh was similar between genotypes, dispersion of the ratio QRS/RSh was significantly smaller in PDPN-/- than in wild-types. We conclude that in the murine ECG QRS is inversely related to RSh. We suggest that both parameters should be considered in the analysis of ventricular conduction time in the murine ECG.