Pulse Waves: How Vascular Hemodynamics Affects Blood Pressure

231 Pages·2017·15.65 MB·English

by  Paolo Salvi (auth.)

Paolo Salvi
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How Vascular Hemodynamics
Aff ects Blood Pressure
Second Edition
123
Pulse Waves
Paolo Salvi
Pulse Waves
How Vascular Hemodynamics
Affects Blood Pressure
Second Edition
PaoloSalvi
DepartmentofCardiovascular,
NeuralandMetabolicSciences
IstitutoAuxologicoItaliano
Milan,Italy
TranslatedbyNicolettaAbbondanza
ISBN978-3-319-40499-8 ISBN978-3-319-40501-8 (eBook)
DOI10.1007/978-3-319-40501-8
LibraryofCongressControlNumber:2016957170
#SpringerInternationalPublishing2017
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To my wife Marna
I thank my Lord for this wonderful gift
Foreword by Alberto Zanchetti
I am delighted to introduce this new updated edition of Paolo Salvi’s volume on
Pulse Waves, brilliantly summarizing the hemodynamics of hypertension and its
implications for treatment. The publication of the second edition at a relatively
short distance from the first one witnessed the success of the work and its timely
appearance.
The founding fathers of cardiovascular physiology were well aware of the
complexity of the hemodynamic mechanisms underlying arterial blood pressure,
andthemodelstheydevelopedtriedtokeepallknownmechanismsunderconsid-
eration. During the second half of the twentieth century, when blood pressure
became an object of increasing clinical interest and a target for therapeutic
intervention, the operational model being used was simplified and reduced to a
pump working against a peripheral vascular resistance. Although certainly
oversimplified, it cannot be denied that this model helped in achieving one of
thegreatestmedicalsuccessesofthepastcentury,thatistheabilitytoeffectively
lower the most important risk factor for cardiovascular disease, high blood
pressure.
With increasing attention being paid nowadays to hypertension in the elderly,
itwastooeasytounderstandthatthesimplifiedmodelthathadbeensobeneficial
in developing current antihypertensive therapy had obvious limitations, and that
in order to understand blood pressure increase with aging additional hemody-
namiccomplexitieshadtobeaddedtothemodel.PaoloSalvi,whohasbeenand
is in the forefront of new research in this area, deserves the highest appreciation
for calling the doctors’ attention to the reality of the complexities of hemody-
namics and for doing that in such a clear and efficacious way. Readers will find
here a clear explanation of the role of large arteries in addition to those of the
cardiac pump and vascular resistances, the role of pulse wave reflection, the
possible differences between peripheral and central blood pressure, the new
techniques and equipments allowing a more precise evaluation of hemodynamic
patterns.
Scientificprogress naturally generatesnotonly knowledgebut challenges. The
major challenge in front of hypertension experts is demonstrating that the new
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viii ForewordbyAlbertoZanchetti
models, the new equipments, and the new measurements can effectively improve
theway weare diagnosingandtreatinghypertensive patients andfurtherimprove
theirsurvival.
IstitutoAuxologicoItaliano AlbertoZanchetti
Milan,Italy
Foreword by Michel E. Safar
Ayoungclinicalresearchworkerinthefieldsofhypertensionduringthe1970shad
principally to focus on the etiological aspects of hypertension, namely the renin–
angiotensin–aldosterone system and the kidney structure and function, which
seemed, at this period, the dominant scientific problems of high blood pressure.
Drugtreatmentofhypertensionwasemerging,andthemostimportantoutcomesof
therapeutic trials were just becoming to be investigated. Hypertension was
describedasamosaicofvarious pathophysiological alterations,involvingnumer-
ous organs and/or functions, including kidney, adrenal glands, renin, sympathetic
nervous system, and arterioles. In fact, it seemed that any part of the body was
involvedinthemechanismsofhypertension.However,theconduitarteries,which
were the precise site where the diagnosis of high blood pressure was established,
werenotconsideredofprimaryinterest.Onlythearterioles,apartofthevascular
tree in which blood pressure was poorly measured, were considered of great
importance. Furthermore, the large arteries, i.e., the precise and specific site of
thecomplications(rupture,thrombosisandaneurysms)ofthedisease,wereconsid-
ered important only as the location of atherosclerosis, a specific process very
similarto,butinfactsubstantiallydifferentfromthatofhypertensionitself.
In that period, however, systemic hemodynamic studies were considered as a
necessary basis for any understanding of the mechanisms of hypertension. This
notionwaswidelyacceptedbothinclinicalandexperimentalsituations,butinboth
fields,thehemodynamicdescriptionofhypertensionreferredalmostexclusivelyto
linear models of circulation with simple measurements of steady flow. Only
Poiseuille’s and Laplace’s laws were considered to be relevant to investigate the
hemodynamicalterations.Theevolutionofthediseasewaspresentedassomekind
of “struggle” between two exclusive components of blood circulation: heart and
arterioles.Noothercomponentofthecirculationhadtobeextensivelyinvestigated.
Tobemorespecific,largearterieshadnosubstantialroletobeclarifiedwithinthe
mechanisms of hypertension. Nevertheless, at that time (1970), the weight of
evidencesuggestedthatconduitarterieswereclearlyinvolvedinboththediagnosis
of the disease and mainly its complications. It was evident that the description of
thisimportantaspectofcirculationinhypertensivesubjectsrequiredaconsiderable
modificationofourconceptualapproachofthisdisease.
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x ForewordbyMichelE.Safar
In the traditional approach, the vascular system is considered as a steady-flow
conduitnetwork,whichismainlycharacterizedbymeanbloodpressure.However,
this model focuses on the end product, the steady flow that is vital for tissue
perfusionand ignores the process thatcomesbefore it which regards the pulsatile
nature of the arterial system and the buffering function of large arteries and their
Windkessel function.This process is the conversion ofthe intermittent, high-flow
ejection by the left ventricle into the continuous peripheral flow and functions
through the elastic properties of the aorta and large arteries already described in
cardiovascularphysiology.Takingintoaccountbothsteadyandpulsatilehemody-
namics phenomena, the pressure waveform may be conceived as a fluctuation,
whosepeakissystolicbloodpressureandnadirthediastolicbloodpressure,around
ameanvalue,meanbloodpressure.Furthermore,largearteriesmaybeinvestigated
not only on the basis of viscoelastic properties of the arterial wall but also on the
basisofpresenceofwavereflections.
In fact, all these new properties of the cardiovascular system could not be
described without new goals in the development of hypertension: not only the
research for the causes of the disease but also the definition of its main purpose,
thereductionofcardiovascularrisk,conceivedbothwithinitssteadyandpulsatile
aspects. The association of hemodynamic development and of cardiovascular
epidemiology has now turned our concepts about hypertension towards several
major noninvasive investigations in men. First, aortic stiffness using aortic pulse
wavevelocity(PWV)measurementbecomesacommonevaluationofcardiovascu-
lar risk. Second, wave reflections may be explored using augmentation index and
pressure.Third,bloodpressurevariabilitybecomesanimportantstudyinthelong
term. Quarter, brachial artery blood pressure may be investigated in parallel with
centralbloodpressuremeasurements,whicharecloserfromorgansgeneratingthe
higher risk. All these determinations may be repeated using nowadays adequate
drug treatments. Finally, all these novel aspects are detailed in the present book,
PulseWaves,donebyPaoloSalvi.
Hoˆtel-DieuHospital,DiagnosisandTherapeuticsCenter MichelE.Safar
ParisDescartesUniversity
Paris,France
Preface to the Second Edition
Over the last 20 years, the outcomes of important clinical trials have pointed out
some peculiar aspects of vascular hemodynamics, stressing the importance of
the mechanical properties of the aorta and large arterial vessels, of central blood
pressure,oftheamplificationphenomenon,ofincrementalpressure,etc.Tounder-
stand these elements, the basics of cardiovascular pathophysiology are required,
particularlyvascularhemodynamics.
This bookaims tobeaclear and easy tool,providing the reader with the basic
principlesofvascularhemodynamicphysiopathology,toofferabetterapproachto
thehypertensivepatient.Sometimesthisteachingmethodneedstosimplifythings
inawaythatcouldseemevenbanal,butthepurposeisalwaystogiveintelligible
messagestoeverybody.
The author will try to take the reader by the hand, to describe the elements of
bloodpressure,startingfromthedefinitionofmeanarterialpressure,goingonwith
the analysis of the basic principles of pulse pressure, and familiarizing the reader
with a “dynamic” concept of blood pressure. Then, the forward and reflected
components of the central pressure wave will be analyzed, providing the reader
with self-study material to read the central blood pressure waveform and to
understandtherelationshipbetweenperipheralandcentralbloodpressure.
Therehavebeensignificantchangesinthissecondversion.Thisismainlydueto
thefactthatSpringerpreferredane-booktoapaperbook.Personally,Idonotagree
with this decision as I continue appreciating the direct relationship with the old
paperbook,whereonecantakenotesandunderlinesentences.Paperbookscanbe
readandzealouslystoredinabookcase.Theneweditionofthebookhasanumber
ofcolorimages.Allthechaptershavebeenupdated.Twonewchaptersconcerning
therelationshipbetweenarterialstiffnessandpressurevariabilityandtheinterrela-
tionbetweenarteriosclerosisandchronicrenaldiseasehavebeenadded.
Please point me out incomplete or unclear parts or even possible mistakes.
Thank you in advance for your suggestions and comments. Any suggestion will
betakenintoconsiderationinthenexteditions,alwaystoimprovethequalityofthe
book.Pleasesendthemtothise-mail:[email protected].
PaoloSalvi
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