1. Archive
2. Vol.55, No.2

Predictability of O₂ Consumption from Contractility and Mechanical Energy of Absolute Arrhythmic Beats in Canine Heart

Abstract: Left ventricular (LV) O₂ consumption (Vo₂) per minute is measurable for both regular and arrhythmic beats. LV Vo₂ per beat can then be obtained as Vo₂ per minute minute divided by heart rate per minute minute for regular beats, but not for arrhythmic beats. We have established that Vo₂ of a regular stable beat is predictable by Vo₂ = a PVA + b E_max + c, where PVA is the systolic pressure-volume area as a measure of the total mechanical energy of an individual contraction and E_max is the end-systolic maximum elastance as an index of ventricular contractility of the contraction. Furthermore, a is the O₂ cost of PVA, b is the O₂ cost of E_max, and c is the basal metabolic Vo₂ per beat. We considered it theoretically reasonable to expect that the same formula could also predict LV Vo₂ of individual arrhythmic beats from their respective PVA and E_max with the same a, b, and c. We therefore applied this formula to the PVA - Emax data of individual arrhythmic beats under electrically induced atrial fibrillation (AF) in six canine in situ hearts. We found that the predicted Vo₂ of individual arrhythmic beats highly correlated linearly with either their Vo₂ (r = 0.96 ± 0.01) or E_max (0.97 ± 0.03) while both also highly correlated linearly with each other (0.88 ± 0.04). This suggests that the above formula may be used to predict LV Vo2 of absolute arrhythmic beats from their Emax and PVA under AF.

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