Cardiac output definition

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Cardiac output is the amount of blood the heart pumps in 1 minute, and it is dependent on the heart rate, contractility, preload, and afterload. Understanding of the applicability and practical relevance of each of these four components is important when interpreting cardiac output values. In the present article, we use a simple analogy comparing cardiac output with the speed of a bicycle to help appreciate better the effects of various disease processes and interventions on cardiac output and its four components. Cardiac output, expressed in liters/minute, is the amount of blood the heart pumps in 1 minute. Cardiac output is logically equal to the product of the stroke volume and the number of beats per minute (heart rate). Easy enough, one may think, but the term cardiac in cardiac output is potentially misleading – with clinician's sometimes assuming that to interpret cardiac output they must focus on the heart. The heart is just one part of the much larger cardiovascular system, however, and the amount of blood it pumps is dependent on both cardiac and extracardiac factors. Although most clinicians should/will be able to recite the four determinants of cardiac output – heart rate, contractility, preload, and afterload – understanding of the applicability and practical relevance of each of these four components is all too often less well ingrained. To try to clarify the individual roles and the combined roles of these four factors in generating cardiac output, and...

\( \newcommand\) • • • • • • • Key Points • Cardiac output, a measure of how much blood the heart pumps over the course of a minute, is calculated by multiplying heart rate by stroke volume. • The heart rate is increased by sympathetic nervous stimulation and decreased by parasympathetic nervous stimulation. • Stroke volume is end diastolic volume (venous return) minus end systolic volume, the amount of blood left over in the heart after systole. • The ejection fraction is stroke volume divided by end diastolic volume. • Mean arterial blood pressure is cardiac output multiplied by total peripheral resistance. A twofold change in vascular size will cause a 16-fold change in resistance in the opposite direction. • Starling’s mechanism states that changes in venous return (preload) to the heart will change cardiac output, which will also change mean arterial blood pressure in the same direction. This means that blood volume and blood pressure are directly related to one another. Key Terms • mean arterial blood pressure: A measure of blood pressure based on cardiac output and vascular resistance. • cardiac output: The volume of blood pumped by the heart, in particular by the left or right ventricle, in the time interval of one minute. Cardiac output (CO) is a measure of the heart’s performance. While there are many clinical techniques to measure CO, it is best described as a physiological and mathematical relationship between different variables. When one of the variables chan...

Although cardiac output is a primary determinant of global O 2 transport there are no absolute values that reflect circulatory adequacy, though very low values are of negative prognostic use. There is no agreement as to what constitutes a clinically relevant change in cardiac output. A recent clinical trial suggests that early goal-directed therapy aimed at increasing cardiac output improves survival. Thus, in some patients, measurement of cardiac output is indicated as an aid to prognosis, diagnosis and to monitor the adequacy of therapy. Gonzalez et al. compared PAC thermodilution cardiac output with indirect Fick measures of cardiac output. They found that at lower cardiac outputs (< 5 l/min) the agreement between the two techniques is good, whereas at higher flows increased differences exist between the two measures. As discussed in this commentary, this study did not address the three potential questions related to PAC monitoring of cardiac output. These questions are: can the PAC cardiac output data be used to monitor cardiac output? Do technical and physiological constraints limit the accuracy of PAC cardiac output? And; are PAC cardiac output measurement errors due to respiratory variation in pulmonary blood flow? Ways of answering each question are given. Cardiac output is a primary determinant of global oxygen transport from the heart to the body. Also, because the major function of the cardiovascular system is to supply sufficient amounts of oxygen to meet the m...

What is cardiac drift and how does it affect heart rate training? Sports scientist, marathon runner and Ironman finisher Benjamin Garcia gives us the nitty-gritty. Before we take a dive into the deep end, let’s get started byfirstdefining the key terms related to cardiac drift. What is Cardiac output? The volume of blood pumped by the heart in one minute. What is Stroke volume? Thevolumeof blood pumped from the left ventricle per beat. What is Heart rate? The number of heart beats per unit of time, usually per minute. cardiac output Formula Cardiac output is the product of stroke volume and heart rate. Cardiac output can be expressed by the below formula: Cardiac output = stroke volume (SV) X heart rate (HR) Why does this matter? The human cardiovascular system is responsible for delivering a continuous supply of oxygen and nutrients to active muscles, which maintains a high level of energy transfer, while also removing metabolites. Compared to static or dynamic resistance exercise, aerobic exercise demands an increase in energy and therefore an increase in oxygen (hence ‘aerobic exercise’). The bodies oxygen requirements are mainly dependent upon exercise intensity and duration. Heart rateresponse to exercise The body’s • • The PNS is mainly responsible for managing homeostasis and SNS is mainly responsible for causing action, such as the fight or flight response. At the beginning of exercise there is a depression of the PNS and stimulation of the SNS, which causes a rapi...

Decreased cardiac output is when your heart can no longer pump enough oxygen to meet the demands of your body. A rapid heart rate is a common symptom of decreased cardiac output, but there are other signs and symptoms, too. Your heart is responsible for pumping oxygenated blood to all the tissues and organs in your body. The amount of blood your heart can pump in a minute is referred to as your “cardiac output.” The amount of oxygen your body needs increases during periods of physical activity. A healthy heart can adjust the amount of blood it pumps to meet the demands of your activity. Decreased cardiac output is when your heart can’t pump enough blood to meet the needs of your body. It can develop as a side effect of heart surgery or a complication of This article will take a closer look at the typical symptoms of decreased cardiac output as well as how it’s diagnosed and managed. Sometimes your cardiac output is measured relative to your body surface area in square meters (m 2). Medical professionals estimate your body surface area from your height and weight. Your cardiac output is influenced by two factors: • Stroke volume: • Heart rate: The amount of oxygen your body needs increases when you’re physically active. A healthy heart can meet this increased demand by increasing its cardiac output. Decreased cardiac output is a state in which your heart can no longer pump enough oxygen to meet your body’s demands. If your heart can’t pump adequate blood to your organs and ...