Therefore, the oxygen extraction level of coronary blood is 70% (100% -30%, assuming 100% saturation for coronary arterial blood).
How much oxygen does the myocardium extract from the coronary arteries?
At rest, approximately 60% to 70% of oxygen is extracted from blood in the coronary arteries.
How is the myocardium supplied with oxygen?
Oxygen is supplied to the heart muscle (myocardium) by the coronary circulation. Coronary blood flow is determined by hemodynamic factors such as perfusion pressure and vascular resistance.
What is the most important factor in myocardial oxygen demand?
Heart rate is thought to be the most important factor affecting myocardial oxygen demand. With an increased heart rate, the myocardium must work harder to complete the cardiac cycle more efficiently. With a shortened cardiac cycle, the time spent in diastole decreases.
Is blood flow through the coronary circulation greatest during systole or diastole explain quizlet?
Major coronary flow is during diastole: During exercise systolic blood pressure increases but diastolic is mostly unchanged. The coronary arteries receive the great majority of their blood flow during diastole (this will be explained in detail in the next objective).
How much oxygen does the myocardium?
Myocardial oxygen consumption and demand
|Tissue type||Oxygen consumption in ml/100g/min|
|Myocardium in cardiac arrest||2|
|Myocardium contracting at rest||6-8|
|Myocardium at maximum inotropy||90|
How do you calculate oxygen extraction ratio?
In order to calculate this, one requires the cardiac output (from the PA catheter) and the oxygen content of the blood.
The simple O2ER equation can be expressed as follows:
- O2ER = VO2 / DO. …
- VO2 = CO ×(CaO2 – CvO2) … this is the global oxygen consumption.
- DO2 = CO ×CaO2 … this is the global oxygen delivery.
How oxygen gets from a coronary artery to heart muscle cells?
The aorta (the main blood supplier to the body) branches off into two main coronary blood vessels (also called arteries). These coronary arteries branch off into smaller arteries, which supply oxygen-rich blood to the entire heart muscle.
What happens when the myocardium requires more oxygen?
Acute Coronary Syndrome. When myocardial oxygen demand is higher than supply, the myocardium must use anaerobic metabolism to meet energy demands. This system can be maintained for only a short period of time before tissue ischemia will occur, which typically results in angina (chest pain).
In which disease there is balance between oxygen supply and the oxygen demand of the myocardium?
Under certain pathologic states such as coronary artery disease, the supply of oxygen may be exhausted and an imbalance between supply and demand occurs which is translated into ischemia. The area of myocardium most susceptible to ischemia is the subendocardium due to mechanical and metabolic forces.
What percentage of cardiac output does the myocardium receive when the body is at rest?
The resting coronary blood flow is ∼250 ml min−1 (0.8 ml min−1 g−1 of heart muscle); this represents 5% of cardiac output.
How do you calculate myocardial oxygen demand?
Myocardial oxygen consumption (MVO2) is defined by the equation: MVO2 = coronary blood flow x arteriovenous difference in O2 content. The average value for a heart of 300 g is 30 to 35 ml/min.
Which factors reflect the oxygen demands of the myocardium?
Three main factors contribute to the myocardial oxygen requirements of the LV: heart rate, ventricular systolic pressure, and size of the LV.
During which phase of the cardiac cycle does blood flow through the coronary circulation quizlet?
The heart sound S2 is due to closing of the aortic and pulmonic valves. Most blood flow through the coronary arteries occurs during ventricular diastole. Stroke volume is reduced when afterload is increased. The a wave on an atrial pressure tracing occurs during atrial systole.
During which phase of the cardiac cycle do the coronary arteries fill?
Blood flow into the coronary arteries is greatest during ventricular diastole when aortic pressure is highest and it is greater than in the coronaries.