Download Commentaries on Viewpoint: Is left ventricular volume during

J Appl Physiol 105: 1015–1016, 2008;
doi:10.1152/japplphysiol.zdg-8134-vpcomm.2008.
Letters To The Editor
Commentaries on Viewpoint: Is left ventricular volume during diastasis the
real equilibrium volume, and what is its relationship to diastolic suction?
TO THE EDITOR:
REFERENCES
1. Kenner HM, Wood EH. Intrapericardial, intrapleural, and intracardiac
pressures during acute heart failure in dogs studied without thoracotomy.
Circ Res 19: 1071–1079, 1966.
2. Vogel WM, Apstein CS, Briggs LL, Gaasch WH, Ahn J. Acute alterations in left ventricular diastolic chamber stiffness. Role of the “erectile”
effect of coronary arterial pressure and flow in normal and damaged heart.
Circ Res 51: 465– 478, 1985.
3. Zhang W, Chung CS, Shmuylovich L, Kovacs SJ. Viewpoint: Is left
ventricular volume during diastasis the real equilibrium volume, and
what is its relationship to diastolic suction? J Appl Physiol; doi:10.1152/
japplphysiol.00799.2007.
Erik L. Ritman, MD, PhD
Professor, Physiology and Medicine
Mayo Clinic
TO THE EDITOR: Functional imaging (FI) combines imaging
datasets and computational fluid dynamics to simulate cardiac
flows (2). It has revealed previously inaccessible subtleties in
ventricular filling dynamics (2– 4). Their important implications for measuring filling pressures and demonstrating “suction” were overlooked by Zhang et al. (5).
During the E-wave upstroke, flow is confluent between atrial
endocardium and atrioventricular orifice (AVO) and diffluent
between AVO and ventricular walls. There is convective acceleration up to AVO and deceleration beyond it (3); flow
velocity decreases from AVO to apex, creating a convective
pressure rise. The measured time-dependent total transvalvular
gradient (䡠PT) depends strongly on the exact placement of
upstream and downstream measurement sites (3), which bears
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on its local (䡠PL) and convective (䡠PC) components, and on
whether “suction” is demonstrable.
FI has revealed the mutually opposed effects on intraventricular 䡠PT of local acceleration and convective deceleration during
the E-wave upstroke (2– 4), when 䡠PC counterbalances 䡠PL. The
smallness of nonobstructive early diastolic 䡠PTs renders catheter
measurements unreliable (3) and confounds filling “suction” demonstrations. During ejection, both components act synergistically
(1, 3) yielding larger 䡠PTs. At E-wave peak, 䡠PL vanishes and the
whole 䡠PT is convective. During the E-wave downstroke, the
strongly adverse intraventricular 䡠PT embodies pressure augmentations along the flow (3) from both convective and
local decelerations.
Soon after the onset of E-wave downstroke, the adverse
pressure causes flow separation and inception of recirculation
with a vortex surrounding the central inflow, and facilitating
filling by robbing kinetic energy that would otherwise contribute to a convective pressure rise (4).
REFERENCES
1. Pasipoularides A. Clinical assessment of ventricular ejection dynamics with
and without outflow obstruction. J Am Coll Cardiol 15: 859 – 882, 1990.
2. Pasipoularides AD, hu M, Womack MS, Shah A, von Ramm O, Glower
DD. RV functional imaging: 3-D echo-derived dynamic geometry and flow
field simulations. Am J Physiol Heart Circ Physiol 284: H56 –H65, 2003.
3. Pasipoularides A, Khandheria BK, KorineA, Shu M, Shah A, Tucconi
A, Glower DD. RV instantaneous intraventricular diastolic pressure and
velocity distributions in normal and volume overload awake dog disease
models. Am J Physiol Heart Circ Physiol 285: H1956 –H1965, 2003.
4. Pasipoularides A, Khandheria BK, KorineA, Shu M, Shah A, Womack
MS, Glower DD. Diastolic right ventricular filling vortex in normal and volume
overload states. Am J Physiol Heart Circ Physiol 284: H1064–H1072, 2003.
5. Zhang W, Chung C, Shmuylovich L, Kovacs SJ. Viewpoint: Is left
ventricular volume during diastasis the real equilibrium volume, and
what is its relationship to diastolic suction? J Appl Physiol; doi:10.1152/
japplphysiol.00799.2007.
Ares Pasipoularides, MD, PhD, FACC
Emeritus Research Professor of Surgery
Duke University
DOES LEFT VENTRICULAR SUCTION EXIST?
TO THE EDITOR:
A vacuum chamber does not attract matter, but
matter is pushed out of regions with high pressure (Wikipedia,
item “suction”).
Mitral flow is energized by the summed action of left atrium
(LA) and left ventricle (LV). At initiation of mitral flow, the
LA contributes energy by push (pLA-pPERI)䡠dVLV. Following the ideas of Nikolic, the LV sucks when during filling the
cavity pressure (pLV) is below intrapericardial pressure
(pPERI), which was atmospheric in his open chest preparations. The LV contributes energy by (pPERI-pLV)䡠dVLV,
which value is practically always negative, i.e., the LV does
not suck, but is weakly pushing.
Why talking about suction? LV energy is the sum of elastic
recoil by the passive matrix and active contraction. At initiation of
mitral flow, passive recoil delivers energy to filling. The still
partly activated myocardium however generates stress while being stretched, implying consumption of mechanical energy. Ap-
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The Viewpoint by W. Zhang et al. (3) advances
our understanding of the age-old question about the meaning of
end diastole of the left ventricle as well as its corollary,
diastolic suction. The discussion omits several additional
mechanisms that may also be contributing to left ventricular
(LV) filling. One plausible explanation of the recoil generated
by the myocardial muscle is the erectile effect of the intramyocardial microcirculation being distended as blood enters it
again after the systolic “blanching” ceases (2). Another plausible mechanism is that the recoiling LV myocardium merely
advances over the stationary blood in the ventricle and atrium—
much like a sock pulled (or in this case pushed) over a foot.
Given these multiple plausible mechanisms, the question
arises as to how much of the ventricular filling is due to
suction. Suction generated by the ventricle should be reflected
by negative transmural pressure during early diastolic relaxation. That this is true only in the late systolic phase was
suggested by Kenner and Wood (1) using simultaneous percutaneous measurement of pericardial and intracardiac pressures.
Their data show that although pericardial pressure is transiently
more negative during systole, that pressure is essentially constant at pleural pressure after the aortic valve closes, suggesting
return to a positive transmural pressure during diastole.
In summary, while I do not disagree with the observations
and conclusions drawn from them as presented in this Viewpoint, I believe that these other mechanisms should also be
considered as possible contributors to this elusive issue.
Letters To The Editor
1016
LETTERS TO THE EDITOR
parently, the weak passive suction component is overruled by the
effect of stretching of still partly activated myocardium.
A consistent definition of suction is supply of mechanical
energy by the LV wall during filling, implying negative transmural pressure. If we would accept the proposed definition of
suction by dpLV/dVLV ⬍ 0, with increasing LA pressure
together with LV dilatation, suction would stay high, whereas
a dilated LV is accepted to have less or no suction at all.
In summary, the left ventricle can suck, but it never does.
Doppler and ultrasonic digital particle imaging velocimetry. J Am Coll
Cardiol 49: 899 –908, 2007.
4. Sengupta PP, Khandheria BK, Korinek J, Wang J, Jahangir A, Seward
JB, Belohlavek M. Apex-to-base dispersion in regional timing of left ventricular shortening and lengthening. J Am Coll Cardiol 47: 163–172, 2006.
5. Zhang W, Chung CS, Shmuylovich L, Kovacs SJ. Viewpoint: Is left
ventricular volume during diastasis the real equilibrium volume, and
what is its relationship to diastolic suction? J Appl Physiol; doi:10.1152/
japplphysiol.00799.2007.
Partho P. Sengupta, MBBS
Bijoy K. Khandheria
A. Jamil Tajik, MD
Division of Cardiovascular Diseases
Mayo Clinic Arizona
Scottsdale, Arizona
REFERENCE
1. Zhang W, Chung CS, Shmuylovich L, Kovacs SJ. Viewpoint: Is left
ventricular volume during diastasis the real equilibrium volume and
what is its relationship to diastolic suction? J Appl Physiol; doi:10.1152/
japplphysiol.00799.2007.
IS DIASTASIS REALLY A PHASE OF HEMODYNAMIC STASIS?
TO THE EDITOR: The Viewpoint by Zhang et al. (5) reiterates
diastasis as a period of zero-motion (static) condition over a
finite time interval where left ventricular (LV) wall mechanics
and transmitral flow are both absent. The following observations, however, would suggest that diastasis may be more
complex than just a period of equilibrium and stasis.
1) First, changes in LV volume and deformation during
diastasis does not reveal a halted phase of mechanical relaxation, rather, LV continues relaxing and lengthening, attaining
progressively higher volumes (1).
2) Volume change in diastasis result from large-scale intracavitary vortical motions that develop during the down stroke
of E-wave (3). Large vortices never unwind smoothly. Rather,
they break up into smaller eddies, dissipating and maintaining
a steady outward force on the LV endocardial surface. This
facilitates continued filling and an increase in LV volume.
3) Indeed filling mechanisms in diastasis are heightened in
some failing hearts. Flow in diastasis may be augmented,
leading to genesis of mid-diastolic filling wave, also referred to
as “L-wave” (2).
There are practical limitations, therefore, in separating early
diastolic suction from diastasis because LV volume changes
during both phases occur on a continuum. Recent studies have
redefined suction as an active state wherein postsystolic regional
shortening (beyond aortic valve closure) produces dynamic shortening-relaxation gradients within LV wall that hasten the process
of diastolic restoration (4). The cross-over point of postsystolic
shortening into relaxation may therefore better define the period in
diastole when active LV suction ceases to operate.
REFERENCES
1. Carlsson M, Cain P, Holmqvist C, Stahlberg F, Lundback S, Arheden
H. Total heart volume variation throughout the cardiac cycle in humans.
Am J Physiol Heart Circ Physiol 287: H243–H250, 2004.
2. Ha JW, Oh JK, Redfield MM, Ujino K, Seward JB, Tajik AJ. Triphasic
mitral inflow velocity with middiastolic filling: clinical implications and associated echocardiographic findings. J Am Soc Echocardiogr 17: 428 – 431, 2004.
3. Sengupta PP, Khandheria BK, Korinek J, Jahangir A, Yoshifuku S,
Milosevic I, Belohlavek M. Left ventricular isovolumic flow sequence
during sinus and paced rhythms: new insights from use of high-resolution
J Appl Physiol • VOL
TO THE EDITOR: The definition of diastolic suction is most often
based on intraventricular pressure and volume changes. In
clinical echocardiography, Doppler indexes used to study diastolic function, reflect changes in the regional pressure gradients. The causal mechanism for diastolic suction is the conformational change occurring during diastole. During this period,
the heart lengthens in the longitudinal direction, thins in the
radial direction, and lengthens its circumference. In addition,
torsion is observed between the base and apex. LV systolic
torsional deformation (twisting) is one mechanism by which
potential energy is stored during ejection, to be later released
during diastole (untwisting) and contributes to the creation of
suction. The diastasis volume summarizes the combination of
all forces (trans-mural, between-cavities gradients, torsionnal)
acting to adapt a chamber volume to its load (blood content).
Recently, new ultrasonographic technologies such as strain
echocardiography have been introduced to assess myocardial
deformation. It has been demonstrated that global diastolic
strain rate during the isovolumic relaxation period, is well
related to hemodynamic indices of LV relaxation (2). Furthermore, Notomi et al. (1) highlighted that ventricular untwisting
provided a temporal link between relaxation and diastolic
suction. Consequently, and as underlined by Zhang et al. (3),
the definition of the diastolic suction should not be limited to
changes in pressure and volume, but should also integrate the
heart deformations leading to the restoration of a nonstressed
LV shape (equilibrium volume).
REFERENCES
1. Notomi Y, Popovc ZB, Yamada H, Wallick DW, Martin MG, Oryszak
SJ, Shiota T, Greenberg NL, Thomas JD. Ventricular untwisting: a
temporal link between left ventricular relaxation and suction. Am J Physiol
Heart Circ Physiol Heart Circ Physiol 294: H505–H513, 2008.
2. Wang J, Khoury DS, Thohan V, Torre-Amone G, Nagueh SF. Global
diastolic strain rate for the assessment of left ventricular relaxation and
filling pressures. Circulation 115: 1376 –1383, 2007.
3. Zhang W, Chung CS, Shmuylovich L, Kovacs SJ. Viewpoint: Is left
ventricular volume during diastasis the real equilibrium volume, and
what is its relationship to diastolic suction? J Appl Physiol; doi:10.1152/
japplphysiol.00799.2007.
105 • SEPTEMBER 2008 •
Alain Boussuges,1 MD, PhD
Jacques Regnard,2 MD, PhD
1
Université de la Méditerranée
Marseille, France
2
Université de Franche Comté
Besançon, France
www.jap.org
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Theo Arts, Professor
Tammo Delhaas
Cardiovascular Research Institute Maastricht
Maastricht, The Netherlands