Isometric Time-Tension Index((dp)/(dt)/IIT) に関する実験的,臨床的研究

抄録

1. Various kinds of the parameters for estimating the cardiac function or contractility have been advocated and their usefulness has been experimentally and clinically investigated by a number of investigators. The author has appreciated that Isometric Time-Tension Index (dp/dt/IIT) is one of the parameters of use for estimating the cardiac contractility. This parameter can be promptly and accurately obtained by means of an on-line real-time system, and which can not be affected by pre-load or after-load upon the ventricle. In this parameter dp/dt is the maximal value of a differentiated ventricular pressure (max dp/dt), and IIT is the total integrated systolic isometric pressure. Isometric systolic time is set 1.5 times Δt that is the time from the peak of the R wave of the ECG to the point of max dp/dt. 2. The AC apparatus (Type I) devised by the author for measuring dp/dt/IIT by an on-line real-time system was equipped with three-ply filters to remove noises mixed from a power source ; without filters the time constant is zero and infinite in a differentiator and integrator, respectively. the time constant of the remolded apparatus (Type II) operated by a direct current is 4.5 msec in the differentiator and 2.2 sec in the integrator. Both types of the apparatus can start integral calculation simultaneously with the triggering R wave of the ECG, while they are regulatable to stop calculation at any time. Calibration of differentiated value to the power input is done in the inside of the apparatus. For an accurate measurement of dp/dt/IIT, the time constant should ideally be zero in the differentiator and infinite in the integrator. The apparatus devised by the author apparently satisfies these requirements. 3. For an aim of studying the effects of the technique of pressure sampling upon the pressure curve and the differentiated one, the author used different 3 types of conduit : a blood transfusion needle, a Cournand's cardiac catheter F 10 or a polyethylene tube (120 cm long, inner diameter 1.6 mm). Every conduit was connected to the same transducer (Statham SP-37 Needle Type) and the apparatus Type II was used. This preliminary experiment revealed that a blood transfusion needle connected Statham SP-37 Needle Type best functioned as the technique of pressure sampling.