For ische-mic patients who have heart failure symptoms but minimal angina, the combination of good target vessels with more than 25% myocardial viability suggests potential to benefit fro
Trang 1those who have known coronary disease and
severe left ventricular dysfunction (LVEF less
than 0.35) with breathlessness but only mild
angina Viability testing is redundant in patients
who have unstable angina, postinfarction angina,
or chronic stable angina, because
revasculariza-tion is indicated for relief of symptoms For
ische-mic patients who have heart failure symptoms but
minimal angina, the combination of good target
vessels with more than 25% myocardial viability
suggests potential to benefit from CABG [46]
For those who have less than 25% viability or
poor target vessels, or are reoperative candidates,
surgery is unlikely to provide benefit
Observational studies have documented
sub-stantial improvements in LV regional and global
function following revascularization of
hibernat-ing myocardium[47,48] This procedure provides
relief from heart failure symptoms, improved
sur-vival, and important quality-of-life benefit A
comprehensive meta-analysis of largely
retrospec-tive data has been performed by Allman and
col-leagues [49] In 24 studies reporting patient
survival after viability testing, annual death rates
were analyzed to produce a risk-adjusted
relation-ship between the severity of LV dysfunction,
pres-ence of viability, and survival benefit associated
with revascularization The study included 3088
patients who had LVEF 32% 8% followed
for 25 10 months For patients who had
stunned or hibernating myocardium
revasculari-zation was associated with a 79.6% reduction in
the annual mortality rate (16% versus 3.2%,
P ! 0001) compared with medical treatment
In contrast, patients who did not have viability
had intermediate mortality, tending to higher
rates with CABG versus medical therapy (7.7%
versus 6.2%) Patients who had viability showed
a direct relationship between the severity of LV
dysfunction and magnitude of benefit with
revas-cularization No benefit was associated with
revascularization in patients who did not have
vi-ability at any level of LVEF The perioperative
mortality rates were impressively high in patients
who did not have viability (around 10%) but
negligible in those who had viability This
differ-ence in mortality is curious given the time frame
of improvement in wall motion following
revascularization
Histopathologic studies have indicated a
grad-ual increase in ultrastructural damage and degree
of myocardial fibrosis as the ischemic process
progresses through stunning, hibernation,
non-transmural scar, and full-thickness scar [47]
Obviously scar never improves in function after revascularization even if covered with a veneer
of healthy epicardial muscle following thromboly-sis Bax and colleagues[50]prospectively studied patients who had ischemic cardiomyopathy and left ventricular dysfunction using preoperative as-sessment of regional perfusion, glucose use, and contractile function Of the dysfunctional seg-ments, 22% were stunned, 23% were hibernating, and 55% were scar tissue In stunned myocardium contractile function improved significantly at
3 months but without further improvement at
14 months Some 30% of stunned segments did not improve In hibernating segments 31% had improved by 3 months and 61% had recovered fully by 14 months In a similar study using intra-operative myocardial biopsy from dysfunctional myocardium, Haas showed only 31% of stunned segments and 18% of hibernating segments to ob-tain complete functional recovery after 1 year[47] Failure to improve was associated with more se-vere degenerative changes in the myocyte, includ-ing depletion of sarcomeres, accumulation of glycogen, loss of sarcoplasmic reticulum, and cel-lular sequestration Using gadolinium-enhanced contrast MRI, Kim and colleagues [21] showed that 78% of dysfunctional segments identified as completely viable showed improvement in con-tractility after revascularization In contrast, 90% of segments with 50% to 75% of wall thick-ness scar did not improve after revascularization The realization that the globular ischemic cardiomyopathy ventricle can be surgically re-stored to an elliptic shape by exclusion of scar is largely attributable to Dor [51] Dor’s endoven-tricular circular patch plasty followed pioneering attempts at physiologic reconstruction by Jatene and Cooley [52] Dor’s major contribution was
to remove endocardial scar, exclude akinetic sep-tum, restore the curvature of the anterolateral wall, and undertake complete myocardial revascu-larization and correction of mitral regurgitation
In the event of spontaneous or inducible ventricu-lar tachycardia, cryotherapy was also applied to the edges of the resection (50% of cases) Between development of the surgical principles in 1984 and
2002, the Dor group operated on 1050 patients who were predominantly NYHA III or IV with LVEF less than 35%, LVESVI greater than 50 mL/m2, LVEDVI greater than 100 mL/m2, and mean pulmonary arterial pressure greater than
25 mm Hg[53] One third of the cases had mitral regurgitation requiring repair A balloon inflated
to the theoretic diastolic capacity of the patient
149
SURGERY FOR HEART FAILURE
Trang 2Maximizing Survival Potential in Very
High Risk Cardiac Surgery
L Balacumaraswami, MBBS, FRCS (C-Th), R Sayeed, PhD, FRCS
Oxford Heart Centre, John Radcliffe Hospital, Oxford, UK
The mean age and risk profile of patients
referred for cardiac surgery is constantly
increas-ing Surgeons are now inclined to accept high-risk
patients because interventional cardiology
pro-vides less invasive alternatives for an overlapping
patient cohort As risk profile increases so does
hospital mortality A survey of 8641 patients who
underwent coronary artery bypass operations in
New England showed an overall mortality of
4.48%, of which 65% could be directly attributed
to postcardiotomy myocardial failure [1] In
the PURSUIT trial, which randomized patients
who had coronary bypass and unstable angina
to a glycoprotein IIb/IIIa inhibitor or placebo,
the 7-day mortality or myocardial infarction rate
was 22.3% in almost 700 patients in the control
arm[2] A collective review of 279 patients who
had dialysis-dependent coronary bypass reported
a 12.2% hospital mortality [3] Similarly the
Mayo Clinic Group reported a 14% perioperative
mortality for patients who had aortic valve
replacement with a left ventricular ejection
fraction (LVEF) less than 35% and a borderline
transvalvular gradient [4] Intraoperative
myocardial injury remains prevalent in the
in-creasingly elderly surgical population because
tolerance to ischemia is reduced in aged
myocar-dium[5]
Patients who are difficult to wean from
car-diopulmonary bypass (CPB) and those who
sub-sequently deteriorate into a low cardiac output
state have mortality rates between 50% and 80%
[6] In established cardiogenic shock, conventional treatment with inotropes, the intra-aortic balloon pump (IABP), or temporary circulatory support devices has not substantially improved survival
In an analysis of risk factors and outcomes for postcardiotomy mechanical support in 19,985 Cleveland Clinic patients, 0.5% received circula-tory support with overall survival of 35%[7] In-cluded were patients who were converted to the HeartMate I implantable system and bridged to transplantation with 72% survival In the absence
of the transplant option, more innovative circula-tory support strategies are required to improve survival in the postcardiotomy setting
Mechanisms of postcardiotomy myocardial dysfunction
Efforts to improve surgical results in patients who have heart failure depend on myocardial protection and preservation of contractile func-tion in the postoperative period The clinical scenario is well known The patient who has myocardial ischemia or chronically impaired left ventricular function undergoes combined valve and coronary bypass surgery The ischemic time exceeds 90 minutes and despite myocardial pro-tection with blood cardioplegia, inotropic support
is required to separate from CPB The vaso-constricted patient returns to the intensive care unit with borderline cardiac index and a blood pressure of 110/70 mm Hg Over the next 4 hours the blood pressure remains acceptable on inotro-pic support but the urine output dwindles and the ankles are cold An IABP is deployed, seems to function well, and optimism returns until the blood gases reveal lactic acidosis and a pH of
* Corresponding author Oxford Heart Centre, John
Radcliffe Hospital, Headley Way, Headington, Oxford
OX3 9DU, UK.
E-mail address: swestaby@ahf.org.uk (S Westaby).
1551-7136/07/$ - see front matter Ó 2007 Published by Elsevier Inc.
Heart Failure Clin 3 (2007) 159–180