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 increases the afterload due to the reason that hypertension causes vasoconstriction, as well as decrease the elasticity of the arteries. Hence, efficient blood flow in the different parts of the body is difficult to accomplish (How High Blood Pressure Can Lead to Heart Failure, 2017).
b. Due to blood loss, massive bleeding or severe hemorrhage prevents oxygen and nutrients from reaching the organs, tissues, and many other areas. Resulting to the arterial pressure decreasing, and a series of cardiovascular responses in order to compensate for the blood loss and restore to normal the arterial pressure as well as sustain perfusion to the organs that did did not receive adequate blood (Osmosis - a Better Way to Learn - Cardiovascular Changes during Hemorrhage: Video | Osmosis, 2021).
c. the drug dopamine - Dopamine enhances cardiac contractility and heart rate by shifting perfusion to the vital viscera in a way that allows for pharmacological titration (Reid PR;Thompson WL, 2022). Shock and refractory heart failure are treated with this.
d. Running a sprint - Because our muscles are working hard during exercise, our bodies need twice (or even three times) as much oxygen as the average cardiac output. This is because of increase in preload, and contractile state, and reduced afterload. In order for blood and oxygen to flow, it is well known that our hearts beat more quickly when we are moving, let alone when we are running. (Cardiac Output, 2019).
e. Hyperthyroidism with increased secretion of thyroid hormones - Hyperthyroidism is present when the thyroid gland produces a lot of thyroxine hormone. According to Osuna et al. (2017), this causes a high cardiac output and left ventricular hypertrophy in the early stage while biventricular dilatation and congestive heart failure in the late stage.
f. Massive myocardial infarction (cardiac tissue death) - When plaque buildup in the coronary artery blocks blood flow, massive myocardial infarction (cardiac tissue death) occurs (atherosclerosis) (Myocardial Ischemia - Symptoms and Causes, 2021). Reduced coronary perfusion causes muscle hypoxia, which can affect myocardial contractility (Dhakam & Khalid, 2008).
g. Hypothermia - Skin reflexively contracts due to adrenergic vasoconstriction when body temperature is low. Due to the reduction in arterial pressure, bradycardia, and subsequent rise in contractility, there is an increase in cardiac output (Deussen, 2007).
h. Emotional distress - Stress typically manifests as a rise in heart rate and blood pressure, directing the heart to pump the necessary amount of blood to the body. Furthermore, while under stress, the coronary (heart) blood arteries spasm and the body requires more oxygen than usual (Torpy et al., 2007).
Source:
Cardiac Output. (2019). Alberta.ca. https://myhealth.alberta.ca/Health/Pages/conditions.aspx?hwid=tx4080abc#:~:text=During%20exercise%2C%20your%20body%20may,gets%20out%20to%20your%20body.
Deussen, A. (2007). Hyperthermie und Hypothermie. Der Anaesthesist, 56(9), 907–911. https://doi.org/10.1007/s00101-007-1219-4
Dhakam, S., & Khalid, L. (2008). A Review of Cardiogenic Shock in Acute Myocardial Infarction. Current Cardiology Reviews, 4(1), 34–40. https://doi.org/10.2174/157340308783565456
How High Blood Pressure Can Lead to Heart Failure. (2017, August 16). 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#:~:text=High%20blood%20pressure%20adds%20to,your%20heart%20to%20work%20harder.
Myocardial ischemia - Symptoms and causes. (2021). Mayo Clinic; https://www.mayoclinic.org/diseases-conditions/myocardial-ischemia/symptoms-causes/syc-20375417#:~:text=Myocardial%20ischemia%20occurs%20when%20blood,heart%20attack%20(myocardial%20infarction).
Osmosis - A Better Way To Learn - Cardiovascular changes during hemorrhage: Video | Osmosis. (2021). Osmosis; Osmosis. https://www.osmosis.org/learn/Cardiovascular_changes_during_hemorrhage
Osuna, P. M., Udovcic, M., & Sharma, M. D. (2017). Hypothyroidism and the Heart. Methodist DeBakey Cardiovascular Journal, 13(2), 60. https://doi.org/10.14797/mdcj-13-2-60
Reid PR;Thompson WL. (2022). The clinical use of dopamine in the treatment of shock. The Johns Hopkins Medical Journal, 137(6). https://pubmed.ncbi.nlm.nih.gov/1563/#:~:text=Because%20dopamine%20increases%20myocardial%20contractility,shock%20and%20refractory%20heart%20failure.
Torpy, J. M., Lynm, C., & Glass, R. M. (2007). Chronic Stress and the Heart. JAMA, 298(14), 1722. https://doi.org/10.1001/jama.298.14.1722