dP/dt(max)--a measure of 'baroinometry'

Area of Science:

• Cardiovascular Physiology
• Hemodynamics
• Cardiac Mechanics

Background:

• Maximal rate of rise of left ventricular pressure (dP/dt(max)) is commonly used to assess myocardial contractility.
• However, dP/dt(max) is significantly affected by ventricular loading conditions, making it an imperfect indicator of the inotropic state.

Purpose of the Study:

• To highlight the limitations of dP/dt(max) as a sole measure of myocardial contractility.
• To introduce the concept of 'baroinometry' to describe the multifactorial determinants of dP/dt(max).

Main Methods:

• Discussion of the influence of preload (ventricular end-diastolic volume) on dP/dt(max).
• Proposal of adjusting dP/dt(max) for preload or calculating it as a function of left ventricular pressure (LVP) during isovolumetric contraction.
• Recommendation to evaluate dP/dt(max) under conditions of altered venous return.

Main Results:

• dP/dt(max) is dependent on both myocardial contractility and loading conditions (aortic pressure and preload).
• dP/dt(max) accurately reflects the inotropic state only when loading conditions remain constant.
• The term 'baroinometry' is proposed to encompass the influence of pressure (baro), inotropic state (ino), and ventricular volume (meter) on dP/dt(max).

Conclusions:

• dP/dt(max) is an unreliable index of myocardial contractility when loading conditions vary.
• Understanding the interplay between preload, afterload, and contractility is crucial for interpreting dP/dt(max) values.
• Baroinometry offers a more comprehensive framework for understanding the determinants of dP/dt(max).