Adequate cardiac output is necessary in order to supply oxygen and other nutrients to all body tissues. Cardiac output is influenced by stroke volume and heart rate. Factors affecting the stroke volume includes PRELOAD, CONTRACTILITY and AFTERLOAD.
In the following conditions, indicate what factor/s influence the cardiac output: PRELOAD, CONTRACTILITY, AFTERLOAD, HEART RATE. Explain the why the factor/s affects cardiac output in 1 to 2 sentences.
- High blood pressure – this causes the heart to become stressed, and therefore constricted. As the arteries’ elasticity decreases, the pumping of the blood to the body and the heart in general, becomes less efficient and the heart rate decreases (Perez, 2022).
- Massive bleeding – as the body losses a large amount of blood, the heart tries to compensate for the fact that arterial pressure and blood volume drastically decreased. To achieve this, the body increases the heart rate and contractility, as well as constrict the blood vessels for the body to compensate the decreased arterial pressure and blood volume (Klabunde, 2021).
- Dopamine – this is a drug that is used to increase cardiac output, which can be caused by underlying conditions of the patient. Since the drug produces positive chronotropic and inotropic effects, this results in the increased heart rate, and contractility, therefore there is more blood flow.
- Running a spring – in any exercise, the more the body works and moves, the more it needs oxygen. To address this, the body increases the cardiac output by increasing the preload, which increases blood volume, which then leads to a higher contractility and afterload.
- Hyperthyroidism with increased secretion of thyroid hormones – this causes increased cardiac output because the hormone induces vasodilation of the circulatory beds that supply the muscle and skin (DeGroot & Leonard, 1970). This forces the increase in preload and consequently, afterload, it makes the heart work harder because of the amount of blood volume there is.
- Massive myocardial infarction (cardiac tissue death) – hear attack in layman’s terms, happens when there is a lack of blood in a certain part of the heart muscle, therefore a lack in oxygen. This is caused by the decrease in contractility, which causes the afterload to increase as well as heart rate (Akar et al., 2017)
- Hypothermia – this occurs when there is a drastic decrease in the core temperature of the body, which is highly fatal. To combat this, the body increases the cardiac output by increasing the contractility, which then leads to a higher stroke volume (Deussen, 2007).
- Emotional distress – this causes the cardiac output to increase because of the increase of contractility. Furthermore, the hormones created because of the emotional distress are what cause the increased heart rate and contractility, leading to increased stroke volume.
References
deGroot, W., & Leonard, J. (1970c). Hyperthyroidism as a high cardiac output state. American Heart Journal, 79(2), 265–275. https://doi.org/10.1016/0002-8703(70)90318-2
Deussen, A. (2007). Hyperthermie und hypothermie. Der Anaesthesist, 56(9), 907–911. https://doi.org/10.1007/s00101-007-1219-4
Dopamine: Uses, Interactions, Mechanism of Action | DrugBank Online. (n.d.). DrugBank. https://go.drugbank.com/drugs/DB00988
Klabunde, R. E. (2015). Cardiac Preload. Cardiovascular Physiology Concepts. https://cvphysiology.com/Cardiac%20Function/CF007
Klabunde, R. E. (2021). Hemorrhagic Shock. Cardiovascular Physiology Concepts. https://cvphysiology.com/Cardiac%20Function/CF007
Motloch, L. J., Ishikawa, K., Xie, C., Hu, J., Aguero, J., Fish, K. M., Hajjar, R. J., & Akar, F. G. (2017). Increased afterload following myocardial infarction promotes conduction-dependent arrhythmias that are unmasked by hypokalemia. JACC. Basic to translational science, 2(3), 258–269. https://doi.org/10.1016/j.jacbts.2017.02.002
Perez, R. (2022, April 8). What is the effect of high blood pressure on cardiac output? Stamina Comfort. Retrieved November 9, 2022, from https://staminacomfort.com/what-is-the-effect-of-high-blood-pressure-on-cardiac-output