Oxygen Utilization by The Heart Flashcards
What is the principle bioenergetic source of the cardiac muscle?
Fatty acid metabolism: 70 to 90% of the energy required.
What does the external work in volume- pressure curve represent?
Oxygen consumption of the heart and chemical energy expended during contraction.
What is Cardiac tension- time index ?
Cardiac muscle tension at the time of contraction X the duration of the contraction.
Heart muscle tension during contraction is proportional to ___?
Ventricular pressure X the ventricular diameter.
What is known as the efficiency of cardiac contraction?
It is the ratio of cardiac work output to total chemical energy expenditure.
Maximum efficiency of the normal heart?
20 to 25%
What is the maximum efficiency of the heart in heart failure?
5 to 10 percent
In heart failure even if the systolic pressure is normal heart spends more energy why?
Because the tension of cardiac contraction is proportional to the ventricular pressure X the ventricular diameter. In heart failure the ventricles are dilated which increases the diameter component of the tension time index leading to more chemical energy expenditure and oxygen requirement.
