Explanatory Part for Cardiovascular Changes with Ageing.ppsx

Geriatrics

1. Explanatory Part for Cardiovascular
Changes with Ageing
By
Prof.Dr.AzzaFekry

2. Change in Cardiac Output, Stroke Volume & Blood
Pressure
Cardiacoutput:
•Cardiacoutputatrestisunaffectedbyage.
•Maximumcardiacoutputandaerobiccapacityarereducedwithage.
Strokevolume:
•Strokevolumeischangedlittlebyaging;atrestinhealthyindividuals,theremay
evenbeaslightincrease.
Bloodpressure:
•Bloodpressureisameasureofcardiovascularefficiency.
•Althoughbloodpressureischaracteristicallyheightenedamongolderadults,there
isevidencesuggestingthattherearenoeffectsofagingonthisindexof
cardiovascular.

3. ChangesinHeartRate:
•Asweage,oneofthemostnotablechangesinthecardiacsystem
isthedeclineinmaximalheartrate.
Oneofthecommonmeansofestablishingaguidelineforchange
inmaximalheartrateisthefollowingformula:
220 -age = max heart rate
•Thereforewhereasayoungadultof20canbeexpectedtohavea
maximalheartrateof200bpm(beatsperminute),ina70yearold
thiswillbeonly150bpm,inan80yearold140bpmandina90
yearold130bpm.

4. CausesofChangesinHeartRate:
Thereductioninmaximalheartrateisthoughttobeduetochangesinthe
autonomicnervoussystem,alongwithage-relateddecreaseinthenumberof
cellsinthesinoatrialnode.
Overallcardiovascularfunctionatrestinmosthealthyelderlyindividualsis
adequatetomeetthebody'sneedforpressureandflow.Therestingheartrate
isunchanged.Heartsizeisessentiallynotdifferentinyoungervsolderadults,
butheartwallthicknessincreasesmodestly,duelargelytoanincreasein
myocytesize.

5. Whiletheearlydiastolicfillingrateisreduced,anenhancedatrialcontribution
toventricularfillinginelderlyindividualsmaintainsfillingvolumeatanormal
level.
Althoughsystolicpressureatrestincreaseswithage,therestingend-systolic
volumeandelectionfractionarenotaltered,duepartlytotheincreaseinleft
ventricularthickness.
Physicalworkcapacitydeclineswithadvancingage,buttheextent
towhichthiscanbeattributedtoadecrementincardiacreserveisnotcertain.
Partoftheage-relateddeclineinmaximumoxygenconsumptionappearstobe
duetoperipheralratherthancentralcirculatoryfactors,e.g.toadecreasein
musclemasswithageduringexercise,theabilitytodirectbloodflowto
muscles,andtheabilityofmuscletoutilizeoxygen.

6. Someelderlyindividualsexhibitcardiacdilatationwhich
producesanincreasedstrokevolumesufficienttocounterthe
well-knownage-relateddecreaseinexerciseheartrate,such
thathighlevelsofcardiacoutputcanbemaintainedduring
exercise.
Still,intheseindividuals,theexercise-inducedreductioninend-
systolicvolumeandincreaseinejectionfractionislessthanin
youngerindividuals.
Asimilarhaemodynamicprofileoccursinindividualsofanyage
whoexerciseinthepresenceofbeta-adrenergicblockade.

7. Withuprightexercisethereisaslowerriseinheartrateintheelderly
comparedtotheyoungersubject.Strokevolumeismaintainedintheelderly
personbyanincreaseinend-diastolicvolumethroughtheFrank-Starling
mechanismateverylevelofexercise.Inyoungersubjectsthestrokevolume
isincreasedbyaprogressivedecreaseinend-systolicvolumeandlittlechange
inend-diastolicvolume.
Finally,thereisanincreaseincirculatingnorepinephrineandepinephrinein
theelderly.Thereisdecreasedresponsivenesstoadrenergicstimuli.Thiscan
beseenwiththediminishedheartrateresponsetoincreasingconcentrations
ofisoproterenolinelderlysubjectscomparedtoyoungersubjectsand
decreasedrelaxationofaorticmusclestripsfromyoungandsenescentanimals
inresponseto-adrenergicagonists,butnottonon-adrenergicrelaxantdrugs.

8. Thisdelayinarterialrelaxationinresponsetoexerciseincreases
vascularimpedancewithincreasingage.
Theincreasedplasmacatecholaminescanhelpcompensateforthe
decreaseof-adrenergicresponsiveness.Inmanyways,the
cardiovascularresponsetoexerciseinelderlysubjectsresembles
theresponsetoexerciseinyoungersubjectswhoaregiven-
adrenergicblockingdrugs.