Editing Blood pressure (section)

==Disorders of blood pressure==
Disorders of blood pressure control include [[Hypertension|high blood pressure]], [[Hypotension|low blood pressure]], and blood pressure that shows excessive or maladaptive fluctuation.

===High blood pressure===
{{Main|Hypertension}}
[[File:Main complications of persistent high blood pressure.svg|thumb|right|300px|Overview of main complications of persistent high blood pressure.<ref name=aha23/>]]

[[Arterial hypertension]] can be an indicator of other problems and may have long-term adverse effects. Sometimes it can be an acute problem, such as in a [[hypertensive emergency]] when blood pressure is more than 180/120 mmHg.<ref name="aha23">{{cite web |title=The facts about high blood pressure |url=https://www.heart.org/en/health-topics/high-blood-pressure/the-facts-about-high-blood-pressure |publisher=American Heart Association |access-date=14 May 2023 |date=2023 |archive-date=14 May 2023 |archive-url=https://web.archive.org/web/20230514190952/https://www.heart.org/en/health-topics/high-blood-pressure/the-facts-about-high-blood-pressure |url-status=live }}</ref>

Levels of arterial pressure put mechanical stress on the arterial walls. Higher pressures increase heart workload and progression of unhealthy tissue growth ([[atheroma]]) that develops within the walls of arteries. The higher the pressure, the more stress that is present and the more atheroma tend to progress and the [[Myocardium|heart muscle]] tends to thicken, enlarge and become weaker over time.

Persistent [[hypertension]] is one of the risk factors for [[stroke]]s, [[myocardial infarction|heart attacks]], [[heart failure]], and [[arterial aneurysm]]s, and is the leading cause of [[chronic kidney failure]].<ref name=aha23/> Even moderate elevation of arterial pressure leads to shortened [[life expectancy]].<ref name=aha23/> At severely high pressures, mean arterial pressures 50% or more above average, a person can expect to live no more than a few years unless appropriately treated.<ref>{{cite book | vauthors = Guyton AC |title=Textbook of Medical Physiology |date=2006 |publisher=Elsevier Saunders |location=Philadelphia |isbn=978-0-7216-0240-0 |edition=11th | page = 220 }}</ref> For people with high blood pressure, higher [[heart rate variability]] (HRV) is a risk factor for [[atrial fibrillation]].<ref name="pmid35260686">{{cite journal | vauthors = Kim SH, Lim KR, Chun KJ | title=Higher heart rate variability as a predictor of atrial fibrillation in patients with hypertensione | journal= [[Scientific Reports]] | volume=12 | issue=1 | pages=3702 | year=2022 | doi= 10.1038/s41598-022-07783-3 | pmc=8904557 | pmid=35260686 | bibcode=2022NatSR..12.3702K }}</ref>

Both high [[Systole (medicine)|systolic]] pressure and high [[pulse pressure]] (the numerical difference between systolic and diastolic pressures) are risk factors.<ref name=aha23/> Elevated pulse pressure has been found to be a stronger independent predictor of cardiovascular events, especially in older populations, than has systolic, diastolic, or mean arterial pressure.<ref name="Cleveland Clinic 2021"/><ref name="Mitchell Izzo Lacourcière Ouellet 2002 pp. 2955–2961"/><ref name="Benetos Safar Rudnichi Smulyan 1997 pp. 1410–1415"/><ref name="Franklin Khan Wong Larson 1999 pp. 354–360">{{cite journal | last1=Franklin | first1=Stanley S. | last2=Khan | first2=Shehzad A. | last3=Wong | first3=Nathan D. | last4=Larson | first4=Martin G. | last5=Levy | first5=Daniel | title=Is Pulse Pressure Useful in Predicting Risk for Coronary Heart Disease? | journal=Circulation | publisher=Ovid Technologies (Wolters Kluwer Health) | volume=100 | issue=4 | date=27 Jul 1999 | issn=0009-7322 | doi=10.1161/01.cir.100.4.354 | pages=354–360| pmid=10421594 | doi-access=free }}</ref> In some cases, it appears that a decrease in excessive diastolic pressure can actually increase risk, probably due to the increased difference between systolic and diastolic pressures (ie. widened pulse pressure). If systolic blood pressure is elevated (>140&nbsp;mmHg) with a normal diastolic blood pressure (<90&nbsp;mmHg), it is called [[isolated systolic hypertension]] and may present a health concern.<ref name=aha23/><ref name="urlIsolated systolic hypertension: A health concern? – MayoClinic.com">{{cite web |url=https://www.mayoclinic.org/diseases-conditions/high-blood-pressure/expert-answers/hypertension/faq-20058527 |title=Isolated systolic hypertension: A health concern? |website=MayoClinic.com |access-date=2018-01-25 |archive-date=2013-12-28 |archive-url=https://web.archive.org/web/20131228153711/http://www.mayoclinic.com/health/hypertension/AN01113 |url-status=live }}</ref> According to the 2017<ref>{{cite book | vauthors = Tan JL, Thakur K | chapter = Systolic Hypertension |date=2022 | chapter-url = http://www.ncbi.nlm.nih.gov/books/NBK482472/ | title = StatPearls |place=Treasure Island (FL) |publisher=StatPearls Publishing |pmid=29494079 |access-date=2022-10-03 }}</ref> American Heart Association blood pressure guidelines state that a systolic blood pressure of 130–139 mmHg with a diastolic pressure of 80–89 mmHg is "stage one hypertension".<ref name=aha23/>

For those with [[heart valve]] regurgitation, a change in its severity may be associated with a change in diastolic pressure.  In a study of people with heart valve regurgitation that compared measurements two weeks apart for each person, there was an increased severity of [[aortic insufficiency|aortic]] and [[mitral regurgitation]] when diastolic blood pressure increased, whereas when diastolic blood pressure decreased, there was a decreased severity.<ref name='Gottdiener2002'>{{cite journal | vauthors = Gottdiener JS, Panza JA, St John Sutton M, Bannon P, Kushner H, Weissman NJ | title = Testing the test: the reliability of echocardiography in the sequential assessment of valvular regurgitation | journal = American Heart Journal | volume = 144 | issue = 1 | pages = 115–121 | date = July 2002 | pmid = 12094197 | doi = 10.1067/mhj.2002.123139 }}</ref>

===Low blood pressure===
{{Main|Hypotension}}
Blood pressure that is too low is known as [[hypotension]]. This is a medical concern if it causes signs or symptoms, such as dizziness, fainting, or in extreme cases in medical emergencies, [[shock (circulatory)|circulatory shock]].<ref name="NHLBI2008">{{cite web|url=http://www.nhlbi.nih.gov/health/dci/Diseases/hyp/hyp_whatis.html|title=Diseases and conditions index – hypotension|date=September 2008|publisher=National Heart Lung and Blood Institute|access-date=2008-09-16|archive-date=2012-04-27|archive-url=https://web.archive.org/web/20120427145640/http://www.nhlbi.nih.gov/health/dci/Diseases/hyp/hyp_whatis.html|url-status=live}}</ref> Causes of low arterial pressure include [[sepsis]], [[hypovolemia]], [[bleeding]], [[cardiogenic shock]], [[reflex syncope]], [[hormone|hormonal]] abnormalities such as [[Addison's disease]], [[eating disorder]]s – particularly [[anorexia nervosa]] and [[bulimia]].<ref>{{Cite book|title=Braunwald's heart disease : a textbook of cardiovascular medicine|date=2012|publisher=Saunders| vauthors = Braunwald E, Bonow RO |isbn=978-1-4377-0398-6|edition= 9th |location=Philadelphia|oclc=671465395}}</ref>

====Orthostatic hypotension====
{{Main|Orthostatic hypotension}}
A large fall in blood pressure upon standing (typically a systolic/diastolic blood pressure decrease of >20/10&nbsp;mmHg) is termed [[orthostatic hypotension]] (postural hypotension) and represents a failure of the body to compensate for the effect of [[gravity]] on the circulation. Standing results in an increased [[Hydrostatics|hydrostatic]] pressure in the blood vessels of the lower limbs. The consequent distension of the veins below the [[Thoracic diaphragm|diaphragm]] (venous pooling) causes ~500 ml of blood to be relocated from the chest and upper body. This results in a rapid decrease in central blood volume and a reduction of ventricular [[Preload (cardiology)|preload]] which in turn reduces stroke volume, and mean arterial pressure. Normally this is compensated for by multiple mechanisms, including activation of the [[autonomic nervous system]] which increases [[heart rate]], [[myocardial contractility]] and systemic arterial [[vasoconstriction]] to preserve blood pressure and elicits [[Vein|venous]] vasoconstriction to decrease venous [[Compliance (physiology)|compliance]]. Decreased venous compliance also results from an intrinsic [[Myogenic mechanism|myogenic]] increase in venous [[smooth muscle]] tone in response to the elevated pressure in the veins of the lower body.

Other compensatory mechanisms include the veno-arteriolar [[axon reflex]], the '[[Skeletal-muscle pump|skeletal muscle pump]]' and '[[respiratory pump]]'. Together these mechanisms normally stabilize blood pressure within a minute or less.<ref name=":4">{{cite journal | vauthors = Ricci F, De Caterina R, Fedorowski A | title = Orthostatic Hypotension: Epidemiology, Prognosis, and Treatment | journal = Journal of the American College of Cardiology | volume = 66 | issue = 7 | pages = 848–860 | date = August 2015 | pmid = 26271068 | doi = 10.1016/j.jacc.2015.06.1084 | doi-access = free }}</ref> If these compensatory mechanisms fail and arterial pressure and blood [[rate of fluid flow|flow]] decrease beyond a certain point, the [[perfusion]] of the brain becomes critically compromised (i.e., the blood supply is not sufficient), causing [[lightheadedness]], [[dizziness]], weakness or [[Syncope (medicine)|fainting]].<ref>{{cite journal | vauthors = Franco Folino A | title = Cerebral autoregulation and syncope | journal = Progress in Cardiovascular Diseases | volume = 50 | issue = 1 | pages = 49–80 | year = 2007 | pmid = 17631437 | doi = 10.1016/j.pcad.2007.01.001 }}</ref> Usually this failure of compensation is due to disease, or drugs that affect the [[sympathetic nervous system]].<ref name=":4" /> A similar effect is observed following the experience of excessive gravitational forces (G-loading), such as routinely experienced by aerobatic or combat pilots '[[G-force|pulling Gs]]' where the extreme hydrostatic pressures exceed the ability of the body's compensatory mechanisms.

===Variable or fluctuating blood pressure===
{{Main|Labile hypertension}}
Some fluctuation or variation in blood pressure is normal. Variation in blood pressure that is significantly greater than the norm is known as [[labile hypertension]] and is associated with increased risk of cardiovascular disease<ref>{{cite journal | vauthors = Stevens SL, Wood S, Koshiaris C, Law K, Glasziou P, Stevens RJ, McManus RJ | title = Blood pressure variability and cardiovascular disease: systematic review and meta-analysis | journal = BMJ | volume = 354 | pages = i4098 | date = August 2016 | pmid = 27511067 | pmc = 4979357 | doi = 10.1136/bmj.i4098 }}</ref> brain small vessel disease,<ref>{{cite journal | vauthors = Tully PJ, Yano Y, Launer LJ, Kario K, Nagai M, Mooijaart SP, Claassen JA, Lattanzi S, Vincent AD, Tzourio C | display-authors = 6 | title = Association Between Blood Pressure Variability and Cerebral Small-Vessel Disease: A Systematic Review and Meta-Analysis | journal = Journal of the American Heart Association | volume = 9 | issue = 1 | pages = e013841 | date = January 2020 | pmid = 31870233 | pmc = 6988154 | doi = 10.1161/JAHA.119.013841 }}</ref> and dementia<ref name=":6"/> independent of the average blood pressure level.  Recent evidence from [[clinical trial]]s has also linked variation in blood pressure to mortality,<ref>{{cite journal | vauthors = Chiriacò M, Pateras K, Virdis A, Charakida M, Kyriakopoulou D, Nannipieri M, Emdin M, Tsioufis K, Taddei S, Masi S, Georgiopoulos G | display-authors = 6 | title = Association between blood pressure variability, cardiovascular disease and mortality in type 2 diabetes: A systematic review and meta-analysis | journal = Diabetes, Obesity & Metabolism | volume = 21 | issue = 12 | pages = 2587–2598 | date = December 2019 | pmid = 31282073 | doi = 10.1111/dom.13828 | s2cid = 195829708 | hdl = 11568/996646 }}</ref><ref>{{cite journal | vauthors = Nuyujukian DS, Newell MS, Zhou JJ, Koska J, Reaven PD | title = Baseline blood pressure modifies the role of blood pressure variability in mortality: Results from the ACCORD trial | journal = Diabetes, Obesity & Metabolism | volume = 24 | issue = 5 | pages = 951–955 | date = May 2022 | pmid = 35014154 | pmc = 8986598 | doi = 10.1111/dom.14649 | s2cid = 245896131 }}</ref> stroke,<ref>{{cite journal | vauthors = Muntner P, Whittle J, Lynch AI, Colantonio LD, Simpson LM, Einhorn PT, Levitan EB, Whelton PK, Cushman WC, Louis GT, Davis BR, Oparil S | display-authors = 6 | title = Visit-to-Visit Variability of Blood Pressure and Coronary Heart Disease, Stroke, Heart Failure, and Mortality: A Cohort Study | journal = Annals of Internal Medicine | volume = 163 | issue = 5 | pages = 329–338 | date = September 2015 | pmid = 26215765 | pmc = 5021508 | doi = 10.7326/M14-2803 }}</ref> heart failure,<ref>{{cite journal | vauthors = Nuyujukian DS, Koska J, Bahn G, Reaven PD, Zhou JJ | title = Blood Pressure Variability and Risk of Heart Failure in ACCORD and the VADT | journal = Diabetes Care | volume = 43 | issue = 7 | pages = 1471–1478 | date = July 2020 | pmid = 32327422 | pmc = 7305004 | doi = 10.2337/dc19-2540 | hdl-access = free | hdl = 10150/641980 }}</ref> and cardiac changes that may give rise to heart failure.<ref>{{cite journal | vauthors = Nwabuo CC, Yano Y, Moreira HT, Appiah D, Vasconcellos HD, Aghaji QN, Viera A, Rana JS, Shah RV, Murthy VL, Allen NB, Schreiner PJ, Lloyd-Jones DM, Lima JA | display-authors = 6 | title = Association Between Visit-to-Visit Blood Pressure Variability in Early Adulthood and Myocardial Structure and Function in Later Life | journal = JAMA Cardiology | volume = 5 | issue = 7 | pages = 795–801 | date = July 2020 | pmid = 32293640 | pmc = 7160747 | doi = 10.1001/jamacardio.2020.0799 }}</ref> These data have prompted discussion of whether excessive variation in blood pressure should be treated, even among normotensive older adults.<ref>{{cite journal | vauthors = Parati G, Ochoa JE, Lombardi C, Bilo G | title = Assessment and management of blood-pressure variability | journal = Nature Reviews. Cardiology | volume = 10 | issue = 3 | pages = 143–155 | date = March 2013 | pmid = 23399972 | doi = 10.1038/nrcardio.2013.1 | s2cid = 22425558 }}</ref>

Older individuals and those who had received blood pressure medications are more likely to exhibit larger fluctuations in pressure,<ref name="ncbi.nlm.nih.gov">{{cite journal | vauthors = Brickman AM, Reitz C, Luchsinger JA, Manly JJ, Schupf N, Muraskin J, DeCarli C, Brown TR, Mayeux R | display-authors = 6 | title = Long-term blood pressure fluctuation and cerebrovascular disease in an elderly cohort | journal = Archives of Neurology | volume = 67 | issue = 5 | pages = 564–569 | date = May 2010 | pmid = 20457955 | pmc = 2917204 | doi = 10.1001/archneurol.2010.70 }}</ref> and there is some evidence that different antihypertensive agents have different effects on blood pressure variability;<ref name=":6">{{cite journal | vauthors = Messerli FH, Hofstetter L, Rimoldi SF, Rexhaj E, Bangalore S | title = Risk Factor Variability and Cardiovascular Outcome: JACC Review Topic of the Week | journal = Journal of the American College of Cardiology | volume = 73 | issue = 20 | pages = 2596–2603 | date = May 2019 | pmid = 31118154 | doi = 10.1016/j.jacc.2019.02.063 | doi-access = free }}</ref> whether these differences translate to benefits in outcome is uncertain.<ref name=":6" />