Flashcards in Determinants and Cardiac basics Deck (100)
Determinants of Cardiac Output
Heart and Stroke Volume
What is SV?
SV is the amount of blood ejected by the ventricle with each contraction.
Preload is the
precontractile fiber length of myocardial fiber augmented
Preload can be augmented by
End diastolic volume
Venous return is directly proportional to
Some factors that affect venous return
Factors that affect venous return include blood volume, venous tone, intrathoracic pressure, pulmonary vascular resistance, and right heart function
What is afterload?
Afterload, the force against heart contraction,
What are the 3 determinants of afterload?
Ventricular wall stress
Systemic vascular resistance
Afterload and SV relationship is
Inversely proportional; As afterload increases, SV decreases.
Contractility is the
intrinsic ability of the myocardial fiber to contract.
What is the main role of Intracellular calcium
main mechanism which influences the binding strength of actin and myosin filaments that determine the force of myocardial contraction
Cardiac output (CO) is the
amount of blood delivered to the tissue in 1 min.
The stronger the stretch, the greater output
What is CI ?
2.5 to 3.5⋅L⋅min−1⋅m−2
CO formula is
HR x SV
What is the primary determinant of HR?
the rate of phase 4 depolarization of the SA node of pacemaker cells
Rate of discharge of SA node is a determinant of HR and determined by
humoral and neural (Epi, NE) mechanisms
In children how is the CO determinants different?
the myocardium is less contractile and less compliant; therefore HR is critically important for maintenance of CO
How does significant tachycardia affect CO?
significant tachycardia can negatively affect CO because increased HR (> 170 beats/min) disproportionately decreases diastolic ventricular filling time relative to decreases in systole, which then contributes to a lower CO.
Heart rhythm also is an important determinant of cardiac output because the atrial contraction inherent in sinus rhythm contributes of _______CO in normal hearts and up to in the case of reduced ventricular compliance or delayed relaxation.
20% to 25%; 40% to 50%
What is a normal SV?
70-80ml per contraction
What are determinants of SV?
Preload, afterload and contractility. and SOMETIMES 4th wall motion abnormalities
What is the formula of SV?
EDV - ESV
What are the determinants of EDV?
What are the determinants of ESV?
Afterload and contractility
3 determinants of Preload
Ventricular filling time
3 determinants of Afterload?