1. 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.
a. High Blood Pressure
High blood pressure makes our heart work harder, therefore affecting the afterload. This is due to the constriction of blood vessels, making it harder for the blood to travel throughout the body (How High Blood Pressure Can Lead to Heart Failure, 2022).
b. Massive Bleeding
The reduction in blood volume causes a reduced afterload due to a fall in central venous pressure and cardiac filling. Therefore, in order to make up for the blood loss, the heart rate is increased (Klabunde, 2021).
c. The Drug Dopamine
Positive chronotropic and inotropic effects are produced by dopamine, which increases heart rate and cardiac contractility (Dopamine: Uses, Interactions, Mechanism of Action | DrugBank Online, n.d.).
d. Running a Sprint
When exercising, like running a sprint, our body needs more oxygen, making our heart beat faster and stronger to get more blood out of our body. This increases our heart rate and cardiac output to get enough oxygen supply for the body (Healthwise Staff, n.d.).
e. Hyperthyroidism with Increased Secretion of Thyroid Hormones
Hyperthyroidism causes hemodynamic changes, including an increase in preload and contractility, contributing to increased cardiac output (Ertek & Cicero, 2013).
f. Massive myocardial infarction (cardiac tissue death)
Myocardial infarction causes changes in our heart's ventricular size and shape, which increases systolic wall stress. This stress increases contractility to compensate for the reduced number of working myocardial cells (H. Zhang et al., 2010).
g. Hypothermia
Hypothermia decreases arterial pressure by constricting the blood vessels, which results in bradycardia. This pressure increase contractility, leading to increased cardiac output (Deussen, 2010).
h. Emotional distress
Stress causes an increased demand for oxygen and spasm in our heart's blood vessels. With that, our heart rate and blood pressure are increased (Torpy, 2007).
References:
Deussen, A. (2010). Hyperthermia and hypothermia. Effects on the cardiovascular system. National Library of Medicine. https://pubmed.ncbi.nlm.nih.gov/17554514/
Dopamine: Uses, Interactions, Mechanism of Action | DrugBank Online. (n.d.). DrugBank. https://go.drugbank.com/drugs/DB00988
Ertek, S., & Cicero, A. F. (2013, November 5). Hyperthyroidism and cardiovascular complications: a narrative review on the basis of pathophysiology. National Library of Medicine. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3832836/
Healthwise Staff. (n.d.). My Health Alberta. Cardiac Output. Retrieved November 11, 2022, from https://myhealth.alberta.ca/Health/Pages/conditions.aspx?hwid=tx4080abc
How High Blood Pressure Can Lead to Heart Failure. (2022, March 4). www.heart.org. https://www.heart.org/en/health-topics/high-blood-pressure/health-threats-from-high-blood-pressure/how-high-blood-pressure-can-lead-to-heart-failure
Klabunde, R. E. (2021, February 2). Hemorrhagic Shock. Cardiovascular Physiology Concepts. https://www.cvphysiology.com/Blood%20Pressure/BP031#:~:text=Hemorrhagic%20shock%20is%20a%20clinical,cardiac%20output%20and%20organ%20perfusion.
Torpy, J. M., MD. (2007, October 10). Chronic Stress and the Heart. Cardiology | JAMA | JAMA Network. https://jamanetwork.com/journals/jama/fullarticle/209139
Zhang, H., Chen, X., Gao, E., MacDonnell, S., Wang, W., Kolpakov, M., Nakayama, H., Zhang, X., Jaleel, N., Harris, D. M., Li, Y., Tang, M., Berretta, R., Leri, A., Kajstura, J., Sabri, A., Koch, W. J., Molkentin, J. D., & Houser, S. R. (2010, July 29). Increasing Cardiac Contractility After Myocardial Infarction Exacerbates Cardiac Injury and Pump Dysfunction. Circulation Research. https://www.ahajournals.org/doi/10.1161/CIRCRESAHA.110.219220