42Dialogues
in Cardiovascular Medicine - Vol 1.N° 1
.1996Summaries
of Ten Seminal Papershis
landmark paper by Bolli on the clinicalrelevance
of myocardial stunning is the firstattempt
to build a bridge between laboratoryand
real clinical conditions. Clinically, stunning
is the mechanical dysfunction thatpersists
after reperfusion despite the absence of irrever-sible
damage and restoration of normal or near-normal coronary
flow. Implicit in this definition is that stunningis
fully reversible provided the myocardium has sufficienttime
to recover. Thus, the contractile abnormality mustbe
reversible and the dysfunctional myocardium have anormal
or near-normal flow, points not always easy todetermine
in the clinical setting. Major clinical situationsin
which myocardial stunning may occur:a)
Stunning after ischemia induced by percutaneous transluminalcoronary angioplasty (PTCA). This
clinical condition bestresembles
the experimental setting for stunning. Briefischemia
associated with simple, uncomplicated PTCAis
usually not sufficient to cause long-lasting systolicabnormalities,
even after multiple balloon inflations,but
it may induce persistent diastolic abnormalitiesresulting
in decreased left ventricular compliance. The
exact incidence, severity, and duration of thesediastolic
abnormalities are unknown, but they are welltolerated
provided the contractile reserve is intact.However,
myocardial stunning can occur in less favorable
situations, eg, in patients with baseline leftventricular
dysfunction, unstable angina, severesimple-vessel
disease, and complicated PTCA.b)
Stunning in unstable angina is often associated with
reversible
wall motion abnormalities. Although consistent
with stunning, these abnormalities couldalso
be caused by hibernation and/or ongoing silentischemia.
Precise diagnosis of stunning requiresconcomitant
measurement of regional function andflow
and determination of the time course of thecontractile
abnormalities. As patients with proximalleft
anterior descending coronary artery lesions andpersistently
negative T waves on precordial leads oftenexhibit
improvement in wall motion, this could beconsidered
good evidence for stunning in unstable angina.c)
Stunning in variant angina. Single episodes of variantangina promptly treated with vasodilators
usually donot
cause stunning, probably because they are tooshort.
However, if coronary spasm persists, stunningresults,
which, if not resolved, can pose a threat to life. d)
Stunning after acute myocardial infarction (AMI). In
AMI,improvement
of systolic and diastolic function or myocardial
salvage by reperfusion does not occurimmediately
after reflow - a good demonstration ofstunning.
Sequential measurements of regional leftventricular
function are thus needed to clearly definethe
time course of stunning in AMI.e)
Stunning after exercise-induced angina. Although
someechocardiographic
observations suggest that exercise-induced
ischemia may result in prolonged contractileabnormalities,
this does not appear to be clinicallysignificant.
The occurrence and severity of postexercisestunning
probably depend on the intensity and durationof
exercise and on the severity of the coronary inflowrestriction.f) Stunning after cardiac surgery. Transient
depression of ventricular
contractility due to stunning is very commonafter
cardiopulmonary bypass, and is usually reversiblewithin
24 to 38 hours. In high-risk patients subjected tocardiac
surgery, stunning can pose a crucial clinical problemwhich
needs treatment and, if possible, prevention.g)
Stunning after cardiac transplantation. There is
considerableevidence
that cardiac function is reversibly depressed inthe
first hours or days after transplantation, which maycomplicate
the postoperative management of theserather
unstable patients.In
conclusion, Bollis hypotheses about myocardial stunningin humans have all been proven in clinical
practice.Though
he also hinted that repetitive stunning might causea
chronic condition similar to hibernation, the clinicaldistinction may not be vital, as in
both cases reperfusionis
required - to improve flow in hibernation and coronaryreserve
in repetitive stunning. Thus, the real clinical issue iswhether the left ventricular abnormality
is reversible or not.TMyocardial stunning in
manR. BolliCirc Res. 1992;86:1671-1691.