Validity of myocardial oxygen consumption parameters

Area of Science:

• Cardiovascular Physiology
• Hemodynamics
• Myocardial Metabolism

Background:

• Accurate estimation of myocardial oxygen consumption (MVO2) is crucial for understanding cardiac health.
• Existing indices for MVO2 estimation vary in reliability under different hemodynamic conditions.

Purpose of the Study:

• To evaluate reported indices for estimating myocardial oxygen consumption (MVO2).
• To identify the most reliable index for MVO2 estimation across a wide range of hemodynamic states and MVO2 variations.

Main Methods:

• Direct measurement of myocardial blood flow in canine models using a coronary sinus catheter.
• Comparison of directly measured MVO2 with indirect MVO2 values calculated from 24 different indices.
• Analysis of 162 steady states under varied hemodynamic and MVO2 conditions.

Main Results:

• The additive parameter E1 demonstrated the highest correlation (r=0.96) with directly measured MVO2 across all tested hemodynamic states.
• Indices neglecting myocardial contractility and ventricular dimensions, such as Tension-Time Index (TTI), showed poor correlation (r=0.63).
• Pressure-heart rate product (P x HR) showed moderate correlation (r=0.86), improving at normal/moderate inotropic states (r=0.91).

Conclusions:

• The additive parameter E1 is the most reliable index for indirect estimation of myocardial oxygen consumption (MVO2).
• Clinical application of MVO2 indices should consider their performance across diverse hemodynamic and inotropic states.
• Indices must account for myocardial contractility and ventricular dimensions for accurate MVO2 estimation.