Therapeutic monitoring of class I antiarrhythmic agents using high-resolution electrocardiography instead of blood samples

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.

Effect of sodium channel blocker, pilsicainide hydrochloride, on net inward current of atrial myocytes in thyroid hormone toxicosis rats

To investigate effect of pilsicainide hydrochloride (pilsicainide) on electrocardiogram (ECG) signals and action potentials (APs) of atrial myocytes, levo-thyroxine (T4, 500 microg/kg body weight) was daily injected into peritoneal cavity of Sprague-Dawley rats for 14 days. T4-treatment significantly shortened RR interval, P wave, and QRS complex durations on ECG. Although pilsicainide did not affect the heart rate, P wave and corrected QT interval (QTc) was increased in T4-treated rats. AP recordings revealed that AP durations at 20%, 50%, and 90% repolarization were significantly shortened and maximal rate of rise (Max dV/dt) was significantly increased in T4-treated rat atrial cells. Pilsicainide significantly decreased AP amplitude (APA) and Max dV/dt in both control and T4-treated rat atrial cells. Concentration-inhibition study demonstrated that pilsicainide significantly inhibited net inward current of T4-treated rats at lower concentration (IC50 of 29.2 microg/mL) than that of control rats (133 microg/mL). In conclusion, pilsicainide could decrease the conduction velocity in T4-treated rat atrium by decreasing the Max dV/dt and net inward current, which could be a possible treatment of thyrotoxicosis-induced arrhythmia.

An Approach to Complete the Manual for Determination of Serum Pirmenol Levels

In order to complete TDM manual for pirmenol in Sapporo Medical Center NTT East, we developed HPLC method and pretreatment procedure for pirmenol samples obtained from patients. Serum (250 microliters) was alkalinized and pirmenol was extracted into n-hexane, and then the drug was again extracted into an acidic solvent, 0.044 M KH2PO4 (pH 2.6) including 0.5% triethylamine. The aqueous extract was used for quantitative determination of the drug by HPLC. The mobile phase consisted of the above acidic solvent-acetonitrile (5:1, v/v) was delivered at 45 degrees C with a flow rate of 1 ml/min through a 4.6 mm x 25 cm ODS-3, a reversed-phase column. Detection of pirmenol and the internal standard (disopyramide) was achieved at 263 nm. Pirmenol and disopyramide was eluted at 5 and 11 min, respectively. Assay limit (25 ng/ml) and accuracy of the analytical method were satisfactory for TDM of pirmenol. During the HPLC analysis of patient samples, no substances that interfered with pirmenol detection were found. It was shown that 1) hemolysis did not affect pirmenol assay at all, 2) pirmenol was stable in the blood samples for at least 24 h even if they were stood at room temperature, and 3) pirmenol was stable for at least 3 days in frozen serum but there significant decrease was observed in pirmenol concentration after 7 days.