Editing Cardiac output (section)

== Clinical significance ==
When ''Q'' increases in a healthy but untrained individual, most of the increase can be attributed to an increase in heart rate (HR). Change of posture, increased [[sympathetic nervous system]] activity, and decreased [[parasympathetic nervous system]] activity can also increase cardiac output. HR can vary by a factor of approximately 3—between 60 and 180 beats per minute—while stroke volume (SV) can vary between {{convert|70|and|120|mL|abbr=on}}, a factor of only 1.7.<ref>{{cite book |last1=Levy |first1=Matthew N. |last2=Berne |first2=Robert M. |name-list-style=vanc |title=Cardiovascular physiology |publisher=Mosby |location=St. Louis |year=1997 |isbn=978-0-8151-0901-3 |edition=7th |url-access=registration |url=https://archive.org/details/cardiovascularph0000bern }}{{page needed|date=October 2014}}</ref><ref>{{cite book |author=Rowell, Loring B. |title=Human cardiovascular control |publisher=Oxford University Press |location=Oxford |year=1993 |isbn=978-0-19-507362-1 }}{{page needed|date=October 2014}}</ref><ref>{{cite book |last=Braunwald |first=Eugene |name-list-style=vanc |title=Heart disease: a textbook of cardiovascular medicine |publisher=Saunders |location=Philadelphia |year=1997 |isbn=978-0-7216-5666-3 |edition=5th |url-access=registration |url=https://archive.org/details/heartdiseasetext0000unse_k3g7 }}{{page needed|date=October 2014}}</ref>

Diseases of the cardiovascular system are often associated with changes in ''Q'', particularly the pandemic diseases [[hypertension]] and [[heart failure]]. Increased ''Q'' can be associated with cardiovascular disease that can occur during infection and sepsis. Decreased ''Q'' can be associated with [[cardiomyopathy]] and heart failure.<ref name="pmid18771592">{{cite journal | vauthors = Vincent JL | title = Understanding cardiac output | journal = Critical Care | volume = 12 | issue = 4 | page = 174 | year = 2008 | pmid = 18771592 | pmc = 2575587 | doi = 10.1186/cc6975 | doi-access = free }}</ref> Sometimes, in the presence of ventricular disease associated with [[Dilated cardiomyopathy|dilatation]], EDV may vary. An increase in EDV could counterbalance LV dilatation and impaired contraction. From equation ({{EquationNote|3}}), the resulting cardiac output Q may remain constant. The ability to accurately measure ''Q'' is important in clinical medicine because it provides for improved diagnosis of abnormalities and can be used to guide appropriate management.<ref name="pmid12226045">{{cite journal | vauthors = Dhingra VK, Fenwick JC, Walley KR, Chittock DR, Ronco JJ | title = Lack of agreement between thermodilution and fick cardiac output in critically ill patients | journal = Chest | volume = 122 | issue = 3 | pages = 990–97 | date = September 2002 | pmid = 12226045 | doi = 10.1378/chest.122.3.990 }}</ref>