Cardiac Output (CO) and Stroke Volume
Cardiac Output and Stroke Volume
Cardiac Output (CO)- the average volume of blood the heart’s left ventricle ejects into the systemic circulation each minute, measured in liters per minute (L/min); equals Stroke Volume times Heart Rate.
CO = Stroke Volume (SV) x Heart Rate (HR)
• Typical CO Range: 5 - 8 L/min
• Atypical CO Range: <2 and > 10 L/min
• Clinical Relevance: indicates increased risk for cardiovascular complications and failure.
• Interpretation: CO varies by patient parameters and is used to calculate AF/ CO ratio. SV is determined by a heart’s preload, afterload and contractility.
Preload is the filling volume of left ventricle at diastole. Preload is used to assess the fluid conditions that help clinicians make proper decisions on whether or not to infuse fluids. Preload depends on the amount of myocardial fiber stretch at the end of diastole (heart is full of blood and ready to contract). It is the pressure stretching the ventricle of the heart, after passive filling and atrial contraction. Preload is affected by venous blood pressure and the rate of venous return. Two preload parameters are Central Blood Volume (CBV) and Total End Diastolic Volume (TEDV) each of which is normalized as an index CBVI and TEDVI. Afterload is the resistance, impedance, or pressure that the ventricle must overcome to eject its blood volume or the tension produced by a heart’s chamber in order to contract.
Afterload is largely dependant on aortic pressure. The most sensitive measure of afterload for the left ventricle is Systemic Vascular Resistance (SVR). Active Circulating Volume (ACV) correlates to SVR Contractility is the intrinsic ability of a cardiac muscle fiber to contract at a given fiber length.
Contractility is difficult to measure directly in the clinical setting. Inotropes are pharmacologic agents that affect contractility. If Preload and Afterload remain constant, then Stroke Volume is explained by Contractility.
URL: Ithaca Marketing Dispatch Jan 2020
Cardiac Output (CO)- the average volume of blood the heart’s left ventricle ejects into the systemic circulation each minute, measured in liters per minute (L/min); equals Stroke Volume times Heart Rate.
CO = Stroke Volume (SV) x Heart Rate (HR)
• Typical CO Range: 5 - 8 L/min
• Atypical CO Range: <2 and > 10 L/min
• Clinical Relevance: indicates increased risk for cardiovascular complications and failure.
• Interpretation: CO varies by patient parameters and is used to calculate AF/ CO ratio. SV is determined by a heart’s preload, afterload and contractility.
Preload is the filling volume of left ventricle at diastole. Preload is used to assess the fluid conditions that help clinicians make proper decisions on whether or not to infuse fluids. Preload depends on the amount of myocardial fiber stretch at the end of diastole (heart is full of blood and ready to contract). It is the pressure stretching the ventricle of the heart, after passive filling and atrial contraction. Preload is affected by venous blood pressure and the rate of venous return. Two preload parameters are Central Blood Volume (CBV) and Total End Diastolic Volume (TEDV) each of which is normalized as an index CBVI and TEDVI. Afterload is the resistance, impedance, or pressure that the ventricle must overcome to eject its blood volume or the tension produced by a heart’s chamber in order to contract.
Afterload is largely dependant on aortic pressure. The most sensitive measure of afterload for the left ventricle is Systemic Vascular Resistance (SVR). Active Circulating Volume (ACV) correlates to SVR Contractility is the intrinsic ability of a cardiac muscle fiber to contract at a given fiber length.
Contractility is difficult to measure directly in the clinical setting. Inotropes are pharmacologic agents that affect contractility. If Preload and Afterload remain constant, then Stroke Volume is explained by Contractility.
URL: Ithaca Marketing Dispatch Jan 2020
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