Correlation between diastolic seismocardiography variables and echocardiography variables.

Aims: Echocardiography is a key diagnostic tool for assessment of myocardial performance and haemodynamics. Seismocardiography (SCG) can potentially provide fast and reliable assessments of key components related to myocardial performance. The aims of this study were to investigate the correlation between SCG and echocardiographic measures, and a decrease in preload by raising the subjects to a 30° head-up tilt position would be detected by both echocardiography and SCG. Methods and results: A total of 45 subjects were included in the study. SCG and electrocardiogram were recorded simultaneously and afterwards echocardiography was recorded. The SCG signals were divided into individual heart beats using a duration-dependent Markov model. Using a fiducial point detection algorithm, the diastolic fiducial points were identified. The amplitudes from the SCG showed a high correlation, especially with the variable e' from the echocardiography. The peak-to-peak amplitude of the diastolic SCG complex and e' had a high correlation of 0.713 (P < 0.001). The second minimum in diastolic occurring after the closing of the aortic valve was the only amplitude showing a high correlation when comparing supine with head-up tilt in the SCG. All the echocardiography variables but E/e' showed a high correlation when comparing supine with head-up tilt. Conclusion: The results found in this study showed a high correlation between the amplitudes from the diastolic SCG and the diastolic variable e' from the echocardiography, thus indicating that the SCG could potentially be utilized to evaluate the diastolic function.

Differential effects of thioridazine enantiomers on action potential duration in rabbit papillary muscle.

The antipsychotic drug thioridazine has potential for treatment of multidrug-resistant microbes including tuberculosis but also causes cardiotoxic QT interval prolongation. Both thioridazine enantiomers have potent antimicrobial effects, but the neuroleptic effect primarily resides with (+)-thioridazine. In this study we for the first time investigate the cardiotoxicity of the isolated thioridazine enantiomers and show their effects on ventricular repolarization. The effects of (+)-thioridazine, (-)-thioridazine, and racemate on the rabbit ventricular action potential duration (APD) were investigated in a randomized controlled blinded experiment. Action potentials were measured in papillary muscles isolated from 21 female rabbits, and the drug effect on 90% APD in comparison with control (ΔΔ-APD90) was evaluated. Increasing concentrations of (+)-thioridazine and the racemate caused significant dose-dependent ΔΔ-APD90 prolongation, while (-)-thioridazine did not. At 0.5 and 2Hz pacing, (+)-thioridazine caused 19.5% and 20.1% ΔΔ-APD90 prolongation, the racemate caused 8.0% and 12.9%, and (-)-thioridazine caused 1.5% and 1.1%. The effect of (-)-thioridazine on APD90 was significantly less than that of the other drugs at both pacing rates (P<0.01 in all cases), and there was no significant difference between (-)-thioridazine and control. The results of this study indicate that the APD prolonging effect of thioridazine is primarily due to the (+)-thioridazine enantiomer. If these results are valid in humans, (-)-thioridazine may be a safer drug for treatment of multidrug-resistant tuberculosis and other microbes.