Hemodynamics in off-pump surgery: normal versus compromised preoperative left ventricular function.
ABSTRACT Off-pump coronary surgery (OPCABG), avoiding cardiopulmonary bypass and cardioplegic arrest, seems to be a better choice in patients with poor baseline cardiac function. Since cardiocirculatory collapse could be induced by heart displacement in this group of patients at high risk, a greater pathophysiologic understanding of the hemodynamic derangements occurring in such patients is needed.
Twenty-eight elective OPCABG patients were evaluated for hemodynamic changes induced by heart displacement, using arterial thermodilution to measure cardiac output and global end-diastolic volume. Hemodynamic parameters were recorded: at baseline; during proper exposure and stabilization of each vessel; and at the end of surgery. Patients were divided into two groups, according to baseline ejection fraction (EF): group A (EF>30%; N=16), group B (EF< or =30%; N=12).
Heart displacement induced a significant drop in the cardiac and stroke index, with a lesser decrease of mean arterial pressure because of raised systemic vascular resistance. Preload, measured as global end diastolic volume, significantly decreased in group A, while it remained unchanged or increased in group B. Linear regression between the preload index and left ventricular stroke work was significant only in group A.
Patients with poor baseline cardiac function can well tolerate OPCABG. However, the pathophysiologic modifications underlying the hemodynamic changes are different compared to those in patients with good preoperative cardiac performance.
- SourceAvailable from: Ahmed A Arifi[Show abstract] [Hide abstract]
ABSTRACT: Coronary artery disease is one of the leading causes of illness for both men and women. However, women are 3 times more likely to die for coronary artery disease as they are of breast cancer. There are an increasing prevalence of coronary artery disease in women and thus facing the need for surgical revascularization. It has long being accepted that women carry a high risk of coronary surgery than men. Many investigators have suggested that female itself is predictive of poor outcome after on pump coronary surgery. We thought to search the litlature to investigate whether women who undergo off-pump surgery receive any benefits compared with women undergoing on-pump surgery.Journal of the Saudi Heart Association. 10/2009; 21(4):199-207.
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ABSTRACT: Nach der Etablierung der chirurgischen Revaskularisation ohne Verwendung der Herz-Lungen-Maschine (HLM) zur Behandlung der koronaren Mehrgefäßerkrankung konnte in vielen prospektiv-randomisierten Studien sowie in Metaanalysen zumeist kein signifikanter Überlebensvorteil der Off-Pump-Chirurgie („off-pump coronary artery bypass“ [OPCAB]) gegenüber der konventionellen Bypasschirurgie (CCAB) mit Einsatz der HLM und kardioplegischem Herzstillstand belegt werden. Daneben waren insbesondere die perioperative Myokardinfarkt- und Schlaganfallrate für beide Verfahren vergleichbar. Diesen Untersuchungen gemeinsam war, dass sie nahezu ausnahmslos an Patienten mit vergleichsweise geringem perioperativen Risiko oder an Mischpopulationen vorgenommen wurden. In den letzten Jahren wird nun auch zunehmend auf den Stellenwert der Beating-Heart-Chirurgie bei unterschiedlichen Risikopopulationen wie Patienten mit schlechter kardialer Pumpfunktion, hohem Alter, vorbestehender Niereninsuffizienz, akutem Myokardinfarkt oder Hauptstammstenose fokussiert. Für die einzelnen Subpopulationen mit spezifischen extrakardialen und kardialen Risiken liegt heute eine Vielzahl von mono- und multizentrischen Studien sowie Metaanalysen vor, die allerdings aufgrund ihres meist nichtrandomisierten Designs die Kriterien einer Level-AEvidenz nicht erreichen. Dennoch erlauben sie es, an Patienten mit spezifischen Operationsrisiken eine Zwischenbilanz vorzunehmen. So zeigte sich, dass insbesondere Multirisikopatienten und Patienten mit präoperativ eingeschränkter kardialer Pumpfunktion bei Anwendung der OPCAB-Chirurgie eine signifikant geringere perioperative Mortalität und Morbidität aufwiesen. Zudem war die Inzidenz perioperativer Schlaganfälle für die meisten Subpopulationen mit extrakardialen Risikofaktoren reduziert. Für Patienten mit präoperativ bestehender pulmonaler oder renaler Funktionsstörung war die Häufigkeit einer entsprechenden postoperativen Organkomplikation signifikant verringert. Bei nahezu allen Risikogruppen war die Transfusionspflichtigkeit reduziert. Für keine der Risikopopulationen zeigte die Beating-Heart-Strategie ein im Vergleich zur CCAB-Chirurgie erhöhtes Risiko. Dies belegt den hohen Stellenwert der OPCAB-Chirurgie insbesondere für Patienten mit einem überdurchschnittlich erhöhten perioperativen Risiko. Since the introduction of off-pump coronary artery bypass grafting (OPCAB) for coronary multivessel disease there was growing interest to evaluate the impact of OPCAB surgery compared to conventional coronary artery bypass grafting (CCAB) with cardiopulmonary bypass and cardioplegic arrest. However, subsequent prospective randomized studies and meta-analyses comparing OPCAB and CCAB surgery were performed on low-risk patients or mixed-risk populations. They usually failed to demonstrate a significant benefit of OPCAB surgery on early mortality or perioperative major cardiac and cerebrovascular events. In recent years, efforts were made to analyze the meaning of beating-heart concepts for patients with specific cardiac and extracardiac risks like ischemic cardiomyopathy, older age, renal failure, acute coronary syndrome, left main stenosis and others. For these subsets of patients several mono- and multicenter studies are available today. Even if most of them were nonrandomized and thus failed to reach evidence level A according to the AHA/ACC (American Heart Association/American College of Cardiology) definition, they still allow analyzing interim results for each specific perioperative risk factor. Particularly multi-risk patients and patients with severely reduced left ventricular function seem to benefit in terms of perioperative mortality and major morbidity by avoiding cardiopulmonary bypass and cardioplegic arrest. Analyzing early results and long-term follow-up of 364 patients with severely reduced ejection fraction < 20%, the authors found a long-term benefit for patients when using OPCAB strategies particularly due to reduced perioperative mortality (Figure 1). Moreover, for most subsets of patients with significant extracardiac risk factors the incidence or perioperative stroke was reduced. In patients with preoperative renal and pulmonary dysfunction a decrease of corresponding organ failure was found for OPCAB strategy. For most risk populations transfusion requirements were significantly lower in OPCAB compared to CCAB surgery. In none of the patients an unfavorable outcome of beating-heart surgery compared to CCAB was shown (Table 1). For emergency patients with an acute coronary syndrome presenting stable and unstable hemodynamics the authors found a clinical benefit by using beating-heart strategies. Particularly in patients with cardiogenic shock, cardiopulmonary bypass was often required to guarantee adequate perioperative organ perfusion. However, these patients seemed to benefit from avoiding global cardiac ischemia and maintaining native coronary blood flow. Follow-up results were comparable for these patients (Figure 2). In conclusion, beating-heart coronary artery bypass grafting seems to be advantageous in various risk populations and should be considered for patients with more than average risks for cardiopulmonary bypass and cardioplegic arrest.Herz 32(6):483-490. · 0.78 Impact Factor
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ABSTRACT: Many new surgical technologies are being developed, with the overall aim of improving outcomes. One common feature of many new technologies is that they offer a safer approach than previous techniques; one of the greatest forces for change over the last 30 years is risk reduction. Cardiac surgery risk has been effectively undercut by percutaneous-based procedures, which have offered dramatic reductions in risk--at least in the short term. Beating heart techniques, whether minimally invasive direct coronary artery bypass (MIDCAB), off-pump coronary artery bypass surgery (OPCAB), or in other forms, such as percutaneous valve replacement, are likely to dramatically increase over the next decade. What role OPCAB and MIDCAB techniques will play in this new era is anyone's guess.Anesthesiology Clinics 10/2008; 26(3):437-52.
Hemodynamics in off-pump surgery: normal versus compromised
preoperative left ventricular function
Giuseppe Fiore*, Maria Elena Latrofa, Pasquale Tunzi, Maria Traversa, Corrado Fondacone,
Nicola Marraudino, Luigi de Luca Tupputi Schinosa, Tommaso Fiore
Department of Emergency and Transplantation, University of Bari, U.O. Anestesia e Rianimazione I, U.O. Cardiochirurgia, A.O. Policlinico,
Giuseppe Fiore, via A. De Ferraris 16, I-70124 Bari, Italy
Received 2 July 2004; received in revised form 9 November 2004; accepted 17 November 2004
Objective: Off-pump coronary surgery (OPCABG), avoiding cardiopulmonary bypass and cardioplegic arrest, seems to be a better choice in
patientswith poor baselinecardiacfunction.Since cardiocirculatory collapsecould be inducedby heart displacement in thisgroupof patients at
high risk, a greater pathophysiologic understanding of the hemodynamic derangements occurring in such patients is needed. Methods: Twenty-
eight elective OPCABG patients were evaluated for hemodynamic changes induced by heart displacement, using arterial thermodilution to
measure cardiac output and global end-diastolic volume. Hemodynamic parameters were recorded: at baseline; during proper exposure and
stabilization of each vessel; and at the end of surgery. Patients were divided into two groups, according to baseline ejection fraction (EF): group
A (EFO30%; NZ16), group B (EF%30%; NZ12). Results: Heart displacement induced a significant drop in the cardiac and stroke index, with a
lesser decrease of mean arterial pressure because of raised systemic vascular resistance. Preload, measured as global end diastolic volume,
significantly decreased in group A, while it remained unchanged or increased in group B. Linear regression between the preload index and left
ventricular stroke work was significant only in group A. Conclusions: Patients with poor baseline cardiac function can well tolerate OPCABG.
However, the pathophysiologic modifications underlying the hemodynamic changes are different compared to those in patients with good
preoperative cardiac performance.
q 2004 Published by Elsevier B.V.
Keywords: Beating heart; Coronary artery bypass surgery; Hemodynamics; Left ventricular function; Off-pump
Off-pump coronary artery bypass surgery (OPCABG) by
median sternotomy is becoming increasingly popular, as in
most patients it allows complete myocardial revasculariza-
tion with excellent short term results. The hemodynamic
modifications induced by heart displacement are usually
transient and reversible, and the technique seems to be safe
even in patients with poor left ventricular function,
improving myocardial preservation and leading to successful
results . However, some patients develop significant
intraoperative hemodynamic instability requiring intra-
aortic balloon counterpulsation (IABP) or cardiopulmonary
bypass (CPB) , and recently Mishra  identified very
low ejection fraction (!25%), recent myocardial infarction
(!1 month), congestive heart failure and preoperative
hemodynamic instability as risk factors for cardiocirculatory
collapse during OPCABG. Because of the potentially cata-
strophic effects of an emergent CBP in a patient in acutely
deteriorating conditions, an in-depth knowledge of the
hemodynamics occurring during cardiac displacement,
along with careful monitoring, is of paramount importance
for the safe management of patients at risk.
Assessment of cardiac preload permits a better patho-
physiologic evaluation of hemodynamic derangements.
Arterial thermodilution, besides measurement of cardiac
output (CO), allows calculation of the global end diastolic
volume (GEDV), proven to be a reliable preload measure-
ment . The aim of the present study is to evaluate the
hemodynamic changes induced by cardiac displacement for
multivessel off-pump coronary grafting in patients with both
normal and poor preoperative left ventricular function using
arterial thermodilution for CO and preload assessment.
2. Material and methods
Twenty-eight patients scheduled for elective multivessel
OPCABG were prospectively enrolled. Informed consent was
obtained from all patients, and the study was approved by
our ethics committee.
European Journal of Cardio-thoracic Surgery 27 (2005) 488–493
1010-7940/$ - see front matter q 2004 Published by Elsevier B.V.
* Corresponding author. Tel.: C39 080 5614 221.
E-mail address: email@example.com (G. Fiore).
Exclusion criteria were: evolving myocardial infarction,
preoperative hemodynamic instability and preoperative
IABP. Unlike other studies , high risk patients, defined
as patients with low ejection fraction (!30%) or recent
myocardial infarction (!1 month), were not excluded.
According to the preoperative left ventricular function,
patients have been divided in two groups:
– Group A: normal to moderately depressed left ventricular
function (preoperative EFO30%).
– Group B: poor left ventricular function (preoperative
All patients were hemodynamically stable in the morning
of surgery, with no need of IABP or other intravenous
pharmacologic support but nitroglycerin and heparin.
Patients received oral Diazepam 0.015 mg/kg 1 h before
surgery as premedication. Preoperative b-blockers, nitrates
and/or calcium-channel-blockers were continued until the
morning of surgery. General anesthesia was induced with
Thiopental (1–3 mg/kg), and maintained with Isoflurane
(0.5–1%) and incremental doses of Fentanil. Vecuronium
Bromide was used for neuromuscolar blockade. Patients
were mechanically ventilated with an oxygen/air mixture
(FiO2Z0.4), setting a respiratory rate of 10 per minute and a
minute volume adjusted to allow normocapnia.
The right radial artery was cannulated in all patients to
monitor arterial blood pressure. A triple-lumen central
venous catheter was inserted into the right internal jugular
vein. The femoral artery was cannulated with a 4F
thermistor-tipped catheter (Pulsion PV2014, Pulsion,
Germany) connected to the PiCCO device (Pulsion Medical
Systems, Munich, Germany) for transpulmonary thermodilu-
tion and continuous CO monitoring by pulse-contour tech-
nique. Leads II and V5 were continuously displayed to ensure
ischemia detection. Cautious volume expansion was used, as
required, to normalize volemia before cardiac displace-
ment. No patient was given intraoperative b-blockers or
calcium-channel-blocker infusion. It was planned to use
inotropic and/or vasoconstrictor agents to treat significant
hypotension (MAP!60 mmHg) or low cardiac output (CI!
2 l/min/m2) outlasting the time of cardiac displacement.
Exposure and stabilization of the target coronary vessels
were achieved by a modified Lima stitch  and a suction
type stabilizer (Octopus III Tissue Stabilizer, Medtronic, Inc.,
Minneapolis, MN). A gentle right decubitus Trendelenburg
position yielded better surgical conditions and improved
venous return . Right hemisternum elevation and exten-
sive right pleurotomy were performed to limit cardiac
compression . The strategy was to always graft first the
left anterior descendent coronary artery (LAD) with the left
internal mammarian artery (LIMA), to restore blood flow as
soon as possible to the anterior wall with minimal displace-
ment of the heart. The distal anastomoses on the diagonal
(DG), ramus intermedius (RI), obtusa marginalis (OM) and
posterior descendent (PDA) arteries were performed without
returning the heart to its resting position between the
successive anastomoses, firstly bypassing the more severe
stenosis to allow collateral flow.
The following hemodynamic parameters were analyzed:
mean arterial pressure (MAP), central venous pressure
(CVP), heart rate (HR), cardiac index (CI), stroke index
(SI), global end-diastolic volume index (GEDVI), systemic
vascular resistance index (SVRI), and left ventricular stroke
work index (LVSWI).
Measurements were performed according to the following
(a) Baseline, with the chest and pericardium open.
(b) Five minutes into the construction of each distal
(c) Final (with the heart back in its anatomical position).
Arterial thermodilution measurements were performed
injecting boluses of 15 ml cool 5% glucose in water in the
central venous catheter and recording the thermal dilution
curves by the termistor-tipped catheter inserted in the
femoral artery and connected to PiCCO.
CO was calculated from the thermodilution curve by the
Two other parameters were calculated from the analysis
of the thermal dilution curve:
– Mean Transit Time (MTt), which is the mean difference
between the time until the first indicator particle has
arrived at the point of detection and the time of arrival of
all the following particles
– Downslope Time (DSt), which is the time of the
exponential decay of the thermodilution curve.
The product of CO and MTt is the the so called ‘needle to
needle volume’, that is the volume between the point of
injection and the point of detection of the thermal
indicator. This volume represents the intrathoracic total
volume (ITTV) . The product of CO and DSt is the volume
of the largest mixing chamber between the site of injection
and the site of detection , that is, for temperature, the
pulmonary total volume (PTV). The difference between ITTV
and PTV is GEDV, the sum of blood volumes in both right and
left cardiac chambers at end diastole.
LVSWI has been calculated by the formula: LVSWI
2.1. Statistical analysis
All values have been indexed to body surface area. All
A 2 Levels Between Group by 7 Levels Within Subjects
Repeated Measures ANOVA with post-hoc Tukey’s testing for
multiple comparisons was used to analyse the hemodynamic
changes induced by heart displacement.
The relationship between GEDVI and LVSWI was analysed
by linear regression. A P value of !0.05 was considered
Preoperative and intraoperative characteristics of the
two groups of patients are summarized in Table 1.
G. Fiore et al. / European Journal of Cardio-thoracic Surgery 27 (2005) 488–493489
A total of 150 hemodynamic measurements were
The hemodynamic modifications induced by heart dis-
placement in each group of patients are shown in Table 2.
At baseline, patients in group B had a significantly lower
CI, SI, and LVSWI and higher SVRI and GEDVI compared to
patients in group A.
In both groups there was a significant drop of CI and SI
(Fig. 1) in all grafting set-up, with an increase in SVRI
(significant only in group A) (Fig. 2) and a decrease of MAP
(Fig. 3). CVP significantly increased in both groups. LVSWI
significantly decreased in each heart position in group A and
in group B. The main hemodynamic changes were recorded
during RI and OM grafting.
In both groups heart displacement induced similar
hemodynamic changes in all parameters except GEDVI
(Fig. 4). In patients with EF O30% (group A), GEDVI uniformly
decreased during cardiac manipulation, remaining lower at
the end of surgery compared to baseline. On the contrary, in
patients with an EF %30% GEDVI was unchanged during LAD
and DG anastomosis, increasing at the time of RI, OM and
PDA grafting. Final values of GEDVI in patients of group B
remained at a higher level compared to baseline, although
this was not statistically significant.
Patients in group B received an overall amount of fluids
significantly lower than patients in group A, and the two
groups were comparable for fluid balance at the end of
No patient developed significant hypotension (MAPO
60 mmHg) prompting administration of vasoconstrictor
agents, and CI reduction rapidly resolved with the heart
back in its anatomic position, never requiring inotropic
Both CI and MAP returned to baseline values at the end of
surgery, except even though a moderate increase of HR
caused a lower final SI especially in group A.
The linear regression between GEDVI and LVSWI (Fig. 5)
was significant only in group A patients, with no significant
correlation in patients of group B.
Both groups of patients in our study show a significant
drop of CI and SI during cardiac displacement, with a better
preserved MAP due an increase of SVRI. These changes
reversed promptly when the heart was back in its anatomic
position. At the end of surgery, CI and MAP returned to
baseline values, with a significantly increased HR which led
to a slight final reduction of SI.
Most studies, both experimental and clinical, report a
drop in CO and SV in response to heart displacement during
OPCABG, which is usually more evident while grafting the
posterior and inferior wall vessels. These hemodynamic
changes are related to many factors (heart displacement,
compression by the stabilizer, occlusion of the coronary
artery), vary according to the location of the vessel to be
Preoperative and intraoperative patients characteristics
Group A (nZ16)Group B (nZ12)
IMA !1 month
History of CHF
Number of grafts
39/56 (69.6%)30/38 (78.9%) n.s.
2253.6G718.9 ml 1084.1G415.3 mlP!0.05
EF, ejection fraction; IMA, myocardial infarction; CHF, congestive heart
Hemodynamic changes induced by heart displacement in the two groups
SVRI (dyn s m2/cm5)
LVSWI (g m/m2)
SVRI (dyn s m2/cm5)
LVSWI (g m/m2)
Values are meanGSD; BSL, baseline; LAD, left anterior descending artery; DG, diagonal artery; RI, ramus intermedius; OM, obtusa marginalis; PDA, posterior
descendent arteries; CI, cardiac index; SI, stroke index; HR, heart rate; MAP, mean arterial pressure; SVRI, systemic vascular resistance index; GEDVI, end-diastolic
global volume index; CVP, central venous pressure; LVSWI, left ventricular stroke work index. Statistical analysis (ANOVA): within groups:aP!0.05;bP!0.01;
cP!0.001 compared to baseline, Between groups:dP!0.05;eP!0.01;fP!0.001 group A compared to group B.
G. Fiore et al. / European Journal of Cardio-thoracic Surgery 27 (2005) 488–493490
grafted, and depend also on preoperative ventricular
function, heart size and coronary anatomy . However,
the precise mechanisms compromising cardiac function are
not fully understood.
In an experimental model on pig, using a suction-type
stabilizer (Octopus), Gruendemann found that lifting the
heart to expose the infero-lateral wall caused a decrease of
MAP and CO, with markedly increased right ventricular end-
diastolic pressure coupled to echocardiographic evidence of
marked compression of the right ventricle and an elliptically
shaped left ventricle. Interestingly, a 208 Trendelenburg
position normalized MAP, CO and SV at the expense of a
further rise in right and also left filling pressure, correspond-
ing to an increased biventricular preload shown by echo-
cardiography . These findings suggest that a severe
reduction in venous return to the folded and crumpled
right ventricle is the main mechanism of hemodynamic
impairment during inferolateral wall exposure. By increasing
venous return, Trendelenburg pushes open the right ven-
tricle, improving left ventricular filling. However, exper-
imental findings on healthy animals should be applied
cautiously in coronary artery disease patients, who often
suffer from poor left ventricular function. Actually, in a
clinical study on 44 OPCABG patients , which reported
hemodynamic and TEE modifications similar to those in
Gruendemann’s study, the Trendelenburg position did not
reliably normalize CO. In another clinical study on 17
OPCABG patients, using transesophageal echodoppler, Bis-
was  showed a significant decline of regional left
ventricular function during circumflex anastomosis com-
pared to LAD and right coronary artery grafting, with a
significant reduction of left ventricular compliance (a
restrictive diastolic filling pattern on transmitral and
pulmonary venous flow velocimetry).
A similar decrease of all measured indices of left
ventricular systolic function in response to heart displace-
ment was reported by Torracca , using an intraventri-
cular conductance catheter to evaluate hemodynamics in
eight OPCABG patients, two of whom had an EF!30%. In this
study exposure of the inferolateral vessels, especially after
stabilizer positioning, caused a drop in CI with an unchanged
left ventricular end-diastolic volume and a clear-cut,
although not statistically significant, left ventricular end-
systolic volume increase (from 48G22 to 61G26 ml/m2).
Such a disagreement between an unchanged preload and a
reduced SI further point out the role of reduced systolic
function in the hemodynamic compromise due to cardiac
All these findings suggest that probably hampered
diastolic filling is not the sole cause of hemodynamic
compromise during heart displacement and stabilization,
and various mechanisms, such as right ventricular failure
, left ventricular regional wall motion abnormalities
Fig. 1. Change of the stroke volume index during and after coronary artery
anastomosis in groups A and B. Abbreviation are the same as defined in
Table 2.* P!0.05 between group.
Fig. 4. Change of the end-diastolic global volume index during and after
coronary artery anastomosis in group A and group B. Abbreviation are the
same as defined in Table 2. *P!0.05 between group, **P!0.01 between
group, ***P!0.001 between group.
Fig. 3. Change of the mean arterial pressure during and after coronary artery
anastomosis in groups A and B. Abbreviation are the same as defined in
Fig. 2. Change of the systemic vascular resistance index during and after
coronary artery anastomosis in groups A and B. Abbreviation are the same as
defined in Table 2. *P!0.05 between group.
G. Fiore et al. / European Journal of Cardio-thoracic Surgery 27 (2005) 488–493491
, and mitral valve annulus distortion  all contribute,
leading to a more complex disturbance of global heart
function, especially in patients with a baseline poor cardiac
Because of the central role of preload in hemodynamic
modifications induced by heart displacement, methods
yielding an on line evaluation a ventricular filling are of
paramount importance to a correct pathophysiologic
assessment during OPCABG. Filling pressures are not useful,
because markedly influenced by changes in ventricular
distensibility, due to compression and possibly ischemia,
and by hydrostatic effect, due to cardiac verticalization.
The intrathoracic blood volume (ITBV), measured by
double-dilution technique, has been described as a new
approach to the estimation of cardiac preload . The
ITBV is a more reliable indicator of cardiac preload than
pulmonary occlusion pressure in critically ill  and CABG
patients , and it correlates to thermodilution CO and SVI
during acute experimental hemorrhage . Recently,
GEDV has been shown to be linearly related to ITBV,
allowing preload assessment by simple thermal dilution in a
peripheral artery .
In the present study, GEDVI, used as an index of preload,
underwent significantly different modifications in patients
with poor baseline left ventricular function (group B),
compared to patients with normal or moderately depressed
left ventricular function (group A). This finding gives possible
insights about different pathophysiologic mechanisms under-
lying hemodynamic modifications induced by heart displace-
ment. First of all, patients in group B show a significantly
higher GEDVI compared to group A, as a reflection of their
lower EF. A far more important finding is the behaviour of
preload, measured as GEDVI, inside each group, in response
to cardiac displacement. Actually, facing a similar CI and SI
reduction, GEDVI is significantly reduced in group A but
remains unchanged or significantly increases (at the time of
inferolateral and inferior wall exposure) in group B, in
agreement to what reported by Torracca . Such a
different behaviour is not the expression of the lower EF in
patients of group B. In fact, patients with different EF should
respond in a fairly similar way to similar preload changes,
whereas our two groups of patients respond in a similar way
(reduction of SV) to opposite changes of preload. These
findings suggest a different mechanism underlying CI
reduction induced by heart displacement in the two groups.
In other words, cardiac displacement behaves as a challenge
to ventricular pumps, and different hearts adapt to this
challenge in a different way, according to their baseline
function. In our study, patients of group A, with a fairly good
myocardial performance, suffer only the effects of the
reduced venous return to the restricted ventricles, and show
a reduced SV as a consequence of the decreased preload. On
the other hand, in patients of group B, in whom a recent
acute myocardial infarction was complicated by a severely
compromised ventricular performance, the restrictive
effect on venous return is in some way overwhelmed by
the ventricular dilatation due to a further decrease of an
already low EF. That is to say, cardiac displacement acts not
only hindering venous return by an increase of biventricular
rigidity; in some cases its effect might be a (further) reduced
systolic performance and/or hampered ventricular ejection
resulting in a decreased SV along with a dilated ventricle.
To better assess cardiac performance in our two groups of
patients, we evaluated the relationship between preload,
measured as GEDVI, and LVSWI. This relationship, called
preload recruitable stroke work (PRSW), has been shown to
be linear and independent of loading, geometry and heart
rate ; its slope has been proposed as a potential measure
of myocardial performance . In our study, linear
regression between GEDVI and LVSWI was significant only
in group A patients, whereas the regression points were
widely scattered of in our group B patients (Fig. 5). This
finding confirms that in patients of group A heart displace-
ment causes mainly a preload reduction with an unchanged
myocardial performance, mimicking the effects of vena
caval occlusion used in experimental models. The lack of
correlation between the index of preload and LVSWI in group
B is more difficult to explain. The most obvious explanation
is a depressed left ventricular contractility during cardiac
manipulations, changing the slope of PRSW relationship, so
that individual points cannot be aligned on the same curve.
Actually, a non linear PRSW relationship has been hypoth-
esized  in ventricles with a baseline depressed function
due to a greater afterload sensitivity, and Ryan  reported
simultaneous changes both in slope and in x-axis intercept of
PRSW line in ischemic ventricles, due to the so called ‘creep
phenomenon’, making the evaluation of such ventricles
difficult by this model. Moreover, a decreasing LVSWI
together with a rising preload could also be the expression
of deficient length-dependent activation related to
exhaustion of the physiologic preload recruitment mechan-
ism in disfunctional ischemic left ventricles, as reported by
De Hert .
All these findings seemingly point to a different patho-
physiologic mechanism of the hemodynamic changes
induced by heart displacement in the two groups of patients.
Our findings should prompt different considerations when
treating low CO during OPCABG. In fact, if postural
manoevers and volume expansion seems to be all what is
needed in patients with a good baseline cardiac performance
(REF), this could be less than optimal, or even deleterious, in
subgroups of patients whose baseline myocardial perform-
ance is severely compromised by a recent acute myocardial
infarction. These patients require more strict hemodynamic
monitoring by techniques allowing ventricular volume
Fig. 5. Linear regression between global end diastolic volume (GEDVI) and left
ventricular stroke work index (LVSWI).
G. Fiore et al. / European Journal of Cardio-thoracic Surgery 27 (2005) 488–493492