Influence of the elevation of the left ventricular diastolic pressure on the values of the first temporal derivative of the ventricular pressure (dP/dt)

Abstract

Purpose -To assess the effects of the elevation of the left ventricular end-diastolic pressure (LVEDP) on the value of the 1 st temporal derivative of the ventricular pressure (dP/dt). Methods (128±18.3mmHg and 150±21.5mmHg), diastolic blood pressure (98±16.9mmHg and 115±19.8mmHg), LVEDP (5.5±2.49 and 9.3±3.60mmHg), and dP/dt (4,855 ± 1,082 mmHg/s and 5,149±1,242mmHg/s) The rate of change in pressure with time (dP/dt), usually known as the 1 st temporal derivative of ventricular pressure, is one of the parameters employed for the assessment of the left ventricular function.In the 60's and 70's, the maximal values of dP/dt (dP/ dtmax) were largely employed to assess the inotropic capacity of the heart 1-4 . From the studies conducted at that time, it was suggested that dP/dt did not reliably reflect the inotropic state. The concept that finally prevailed was that dP/dtmax had limited practical applications as an indicator of the inotropic capacity 5 . The major limitation 6,7 was the lack of specificity of this parameter, since other factors, in addition to myocardial inotropic capacity, interfered with the maximal value of dP/dt. The factors capable of interfering with the values of the dP/dtmax include: the afterload 7,8 , the preload 9,10 and the presence of myocardial hypertrophy 2,11 . The correct interpretation of the relationship between the degree of myocardial stretching (preload) and dP/dt is particularly complex. According to the most traditional version of the concepts related to ventricular function, the inotropic capacity of the heart and the variation of the performance of the heart as a result of change in the muscular length during rest (Frank-Starling mechanism) were considered independent myocardial characteristics. Yet, the influence of the Frank-Starling mechanism on dP/dtmax would not be related to changes in the inotropic capacity of the heart. For this reason, variations in the ventricular volume occurring during the evaluation of dP/dt max would preclude an exact definition of the inotropic state.Advances in the knowledge of the physiological basis of myocardial contraction make this traditional view questionable, currently allowing alternative explanations. More recent information 12-17 about the subcellular adjustments involved in the relationship between the ventricular stretching during rest and the mechanical performance of the ventricles indicate that myocardial stretching interferes with the degree of activation of the contractile phenomenon, i.e., with myocardial contractility. The identification of

Myocardial protection by continuous, blood, antegrade-retrograde cardioplegia in rabbits

“…There are, in the literature, established relationships between animal and heart weight. The frequency and the rhythm influence the contractile state of the myocardium 10 . This action, known as Bowdicht effect, settles down at the level of the membrane of the miocardic cell.…”