GUEST LECTURES IN BRIEF
Dr. Jamil A. Tajik chair, Division
of Cardiovascular Diseases, MAYO CLINIC, USA
|
The clinical diagnosis of infective endocarditis
(IE) is based upon a combination of features such
as fever, a new regurgitant murmur, and positive
blood cultures.
The hallmark lesions of IE are vegetations. In
the past, visualization of these lesions was possible
only at surgery or at autopsy.
Echocardiography can detect infective vegetations
and the complications of endocarditis. Transesophageal
echocardiography (TEE) is superior to transthoracic
echocardiography in detecting vegetations and
the complications of IE. TEE can detect masses
as small as 1mm, with a sensitivity and specificity
of 98% and 96% respectively.
Thus, the diagnosis of IE can be made more promptly
in many cases based on a clinical suspicion and
a diagnostic echocardiogram, eliminating the need
to await blood-culture results. Therefore, antibiotic
therapy can be started early.
A negative TEE in a patient with suspected
IE makes this diagnosis unlikely, especially in
a patient without a prosthetic valve.
An alternative source of infection should be
searched for. Nonetheless it is important to remember
that no echocardiographic study can rule out IE
completely, especially if it is early in the course
of the disease when the vegetations are small
or when a prosthetic valve is present. In such
situations, repeat TEE should be considered if
no alternative diagnosis can be found and a clinical
course consistent with IE persists.
Although the rate of false negative TEE examinations
in patients with IE is only 5 percent or less,
all negative studies confer an obligation to the
physician to follow patients until a sustained
afebrile status is confirmed.
TEE is the best diagnostic tool currently available
in identifying complications of endocarditis.
It helps tremendously in the timing of surgical
intervention; it also gives valuable information
to the surgeon by accurately identifying pathologic
lesions such as abscesses, intracardiac fistulas,
valve destruction, extension of infection and
significant hemodynamic complications such as
regurgitation.
Large vegetations significantly increase the risk
of complications: embolization, surgery, CHF and
failure to respond to antibiotics.
Vegetations on the mitral valve were more
likely to embolize, as were mobile vegetations.
A rapid increase in size suggests active disease
and is an ominous sign. Vegetations of increasing
size had a significantly higher incidence of embolic
events, abscess formations, and valve replacement.
CHF is a definite indication for surgery in any
patient with IE. Prior to the routine use of valve
replacement or valve repair, CHF caused approximately
90 percent of deaths in patients with IE. At present,
heart failure is the indication for surgery in
two-thirds to three-fourths of patients with IE
who undergo surgery.
Moderate to severe heart failure caused
by IE confers a high mortality risk without corrective
surgery.
Medical therapy alone is associated with mortality
rates of approximately 75 percent; this can be
reduced to 25 percent or less with surgery.
Endocarditis-induced aortic insufficiency is more
likely to produce CHF than endocarditis-induced
mitral insufficiency.
Surgery should be undertaken as soon as
signs of heart failure appear, before extreme
or refractory hemodynamic deterioration occurs.
It is dangerous in such patients to wait for improvement
to occur with medical therapy.
Summary by: Rachel Hajar, MD
Dr. Ulrich Sigwart, Chairman,
Cardiology Department University of Geneva, Switzerland |
Stent or Surgery (SoS) was an international study involving 11 European countries and Canada, and was designed to compare CABG and Stent in more than 900 patients with multivessel disease.
The primary end point was need for additional revascularizations; secondary end points were composite of death or nonfatal Q-wave MI, and all-cause mortality.
The SoS trial result was compared to ERACI II and ARTS trials. In ERACI II,
Stent or Surgery (SoS) was an international study involving 11 European countries and Canada, and was designed to compare CABG and Stent in more than 900 patients with multivessel disease. The primary end point was need for additional revascularizations; secondary end points were composite of death or nonfatal Q-wave MI, and all-cause mortality.
The SoS trial result was compared to ERACI II and ARTS trials. In ERACI II, there was an unusually high mortality in the CABG group and that PTCA/stent was clearly superior to surgery. But the ARTS trial found similar mortality rates in both stent and CABG group. The SoS trial on the other hand showed that at one year, mortality in the CABG group was strikingly low, 0.8%; there was a higher overall mortality in the stent group, which could in part be explained by the higher number of cancer deaths in this group.
Thus, surgery will remain an excellent treatment strategy for patients who are not candidates for percutaneous coronary intervention (PCI) and probably for diabetic patients, particularly in those with advanced multivessel disease and impaired left ventricular dysfunction.
For the majority of patients, PCI will become the standard.
Summary by: Dr.Jassim Al-Suwaidi
Dr. Afksendiyos Kalangos, Chairman, Department Of Cardiovascular Surgery
University Of Geneva, Switzerland
|
The traditional indication for surgery in patients
with severe mitral regurgitation (MR) has been
the development of disabling symptoms, i.e., NYHA
class III/IV. However, patients with MR may remain
asymptomatic for many years.
In patients with severe symptomatic MR,
the clinical outcome is poor: survival rates are
as low as 33 percent at eight years in the absence
of surgical intervention.
The average mortality rate is approximately
5 percent per year; most deaths are related to
heart failure, but there is a substantial incidence
of sudden death.
Other complications include atrial fibrillation,
cerebral ischemic events, and endocarditis. The
optimal timing of corrective surgery is determined
by several factors: 1) the presence or absence
of symptoms; 2) the functional state of the left
ventricle; 3) the feasibility of valve repair;
4) the presence of atrial fibrillation or pulmonary
hypertension; and 5) the preference and expectations
of the patient. Recent data however, indicate
that surgery should not be delayed for a number
of reasons: 1) left ventricular (LV) dysfunction
progresses silently.
In patients with severe symptoms, LV dysfunction
may become manifest only after surgery, with consequent
excess mortality and morbidity; 2) the development
of LV dysfunction is difficult to predict and
may occur unexpectedly despite patient monitoring;
3) even minimally symptomatic patients with severe
MR have severe long-term mortality and morbidity;
4) valve repair has a low operative mortality
and good long-term outcome. In asymptomatic patients
with severe MR, the outcome is improved if surgery
is performed before the onset of irreversible
ventricular dysfunction. No randomized trials
have assessed the optimal timing of intervention
for asymptomatic severe MR. However, echocardiographic
parameters such as left ventricular end-systolic
dimension and ejection fraction can be used to
identify early systolic dysfunction.
Indicators of early systolic dysfunction are an
end-systolic dimension of 45 mm or more or an
ejection fraction of 0.60 or less. Systolic dysfunction
is most likely when both values are abnormal and
sequential studies show a progressive deterioration.
Corrective surgery is indicated in asymptomatic
patients with chronic severe MR if there is definite
and reliable evidence of LV systolic dysfunction
(ie, LVEF <55 percent).
In comparison, many patients with borderline LV
function (LVEF 55 to 60 percent) remain asymptomatic
and stable for years.
In such patients, surgical decisions often
depend upon other issues such as atrial size,
the presence or absence of atrial fibrillation,
evidence of pulmonary hypertension, and the desire
of the patient and his or her expectations. Among
those who are treated medically, any trend indicating
a further decline in LVEF can be taken as an indication
for surgery. Surgery should be considered in a
mildly symptomatic patient with normal or borderline
LV function if it appears that valve repair is
feasible, particularly if flail mitral valve is
present. In such patients, consideration should
also be given to such issues as atrial size and
rhythm, early pulmonary hypertension, and the
preference of the patient. If, however, the LVEF
is less than 55 percent, surgery should be recommended
even if valve replacement is necessary.
There are studies consistently linking severe
preoperative symptoms and excess operative and
long-term mortality. Patients with functional
class III or IV symptoms have significantly increased
short-and long-term mortality.
Therefore, early surgery in patients with no or
minimal symptoms has become a reasonable
consideration and appears to improve the outcome
of patients with significant MR. Mitral valve
repair rather than mitral valve replacement is
the preferred mode of correction. This is now
feasible in a high percentage of patients ( 84%).
Thus, to achieve the benefits of early repair,
there should be a strong likelihood of valve repair
and the surgeon should be highly skilled in mitral
valve surgery.
This aggressive approach is justifiable
only under strict conditions: 1) the diagnosis
of severe MR should be well-documented; 2) only
patients with organic MR are candidates; 3) the
likelihood of valve repair should be high; 4)
low operative mortality as determined by patient's
age and condition; and 5) the institution's operative
mortality should be very low. The operative risk
for patients with severe MR who are asymptomatic
or mildly symptomatic should be reviewed for each
institution.
The operative risk today is extraordinarily
low, 0.5% for all ages and 0% for patients less
than 75 years old.
Summary by: Summary by: Rachel Hajar, MD
Dr. John J. V. McMurray, University of Glasgow, UK
|
The two most important pathophysiological processes
in congestive heart failure (CHF) are remodeling
and contractile dysfunction. The presence of either
state activates abnormal signaling pathways such
as the rennin-angiotensin system (RAAS), neurotransmitter
epinephrine, proinflammatory cytokines, potent
vasoconstrictors such as endothelins, Ca, Na transport,
and tumor necrosis factor (TNF).
Once these abnormal feedback mechanisms are activated,
a vicious cycle ensues.
Any type of therapy that interrupts the
abnormal feedback pathway will reverse the progression
of myocardial dysfunction and remodeling. Drugs
that are currently used to block abnormal neurohumoral
pathways are beta-blockers, ACE inhibitors, and
aldosterone (spironolactone). Beta-blockers have
emerged as important agents in patients with heart
failure due to left ventricular systolic dysfunction.
The US carvedilol heart failure program,
MERIT-HF, and CIBIS-II have all demonstrated substantial
morbidity and mortality reductions when carvedilol
or metoprolol are added to ACE inhibitors, digoxin,
and diuretics.
The Carvedilol Prospective Randomized Cumulative
Survival Trial (COPERNICUS) demonstrated the efficacy
and safety of carvedilol in NYHA class IV patients.
In fact, the trial was stopped early because
of the marked benefit of carvedilol on mortality.
Both the CAPRICORN and COPERNICUS Trials confirm
the benefit of beta-blockade with carvedilol in
a broad range of patients, from those with left
ventricular dysfunction post-MI to those with
severe heart failure.
COPERNICUS showed a 35% decrease in all-cause
mortality in the carvedilol group Eplerenone is
a new specific aldosterone antagonist that is
currently under testing for CHF.
The Eplerenone Post-AMI Heart Failure Efficacy
and Survival Study (EPHESUS) is underway.
This trial is designed to see whether the
use of eplerenone will have a beneficial effect
on survival and morbidity in patients who have
suffered a myocardial infarction (MI) and also
have early complications of heart failure, as
identified by left ventricular dysfunction.
The ELITE-1 trial had previously suggested that
losartan, an angiotensin II receptor blocker (ARB),
might show greater benefit than captopril in heart
failure.
However, ELITE-1 was too small to reach any conclusions,
hence, ELITE-2 was designed and powered to determine
whether losartan would show a reduction in mortality.
In the ELITE-2 heart failure trial,Losartan did
not show significantly different effects from
the ACE inhibitor, captopril, on mortality or
any of the other major clinical endpoints.
The results showed non-significant trends in favor
of captopril, leading to the conclusion that ACE
inhibitors should remain the treatment of choice
for heart failure, with losartan reserved for
patients intolerant to these agents.
The RESOLVD trial also evaluated candesartan,
another ARB agent, in heart failure patients.
This was a remarkably complex clinical trial designed
to test feasibility of polypharmacy with ACE inhibitors,
angiotensin receptor blockers, and beta-blockers
in a wide spectrum of heart failure patients.
In the main trial, candesartan alone, enalapril
alone, or the combination of candesartan and enalapril
was evaluated with respect to exercise tolerance,
ventricular function, quality of life, neurohormonal
assay and drug tolerability.
The overall conclusion from this study was that
candesartan was as effective, safe and tolerable
when compared with enalapril in patients with
symptomatic congestive heart failure and that
the combination of candesartan plus enalapril
appeared to be more beneficial for preventing
left ventricular dilation and suppressing neurohormonal
activation than either candesartan or enalapril
alone.
The use of angiotensin receptor blocking drugs
in CHF has stirred a great deal of interest and
excitement. While both ARB and ACE-inhibitors
act by blocking the renin angiotensin system,
they do this in different ways and their actions
may be complementary.
More decisive answers to the ARB vs ACE
inhibitor questions should come with the pending
results of several trials.
These include the Valsartan in Acute Myocardial
Infarction (VALIANT) trial looking at the ARB
valsartan in comparison to, and in combination
with, captopril in post-MI patients with heart
failure or LV dysfunction.
The Val-HeFT trial is another ongoing study evaluating
the use of valsartan in combination with ACE inhibitors.
Another on going trial is the Candesartan in Heart
Failure-Assessment of Reduction in Mortality and
Morbidity (CHARM), looking at candesartan against
placebo in different treatment groups, including
one group taking ACE inhibitors and another on
the ARB alone. The results of these clinical trials
are expected in late 2003 and should help resolve
the definitive role of ARBs in the treatment of
CHF in particular as monotherapy in the absence
of ACE inhibitors, or as combination therapy with
ACE inhibitors. There are other several trials
that are currently evaluating promising new drugs
that specifically block a particular abnormal
pathway.
These are: Bosentan, which is an endothelin
inhibitor; anti-tumor necrosis factor antibodies;
Ranolazine, which is a pFOX inhibitor (partial
fatty acid oxidation inhibitor); and the neural
endopeptidase inhibitors. Neural endopeptidases
are natriuretic peptides that are endogenously
secreted in the atria and brain and are produced
in large amounts in CHF. They are beneficial because
they cause vasodilatation and decrease renin/aldosterone
secretion.
Since they exert a beneficial effect, the goal
is to prevent or inhibit their metabolism.
Nesiritide, a recombinant form of endogeneous
B-type natriuretic peptide (BNP), is another promising
new drug in CHF therapy.
It is a new venous and arterial vasodilator that
has been shown to increase cardiac output without
increasing heart rate, to decrease preload and
afterload, and to improve symptomatology in CHF
patients. In clinical studies, nesiritide reduced
pulmonary capillary wedge pressure, right atrial
pressure and systematic vascular resistance while
increasing cardiac output without affecting the
heart rate.
The PRECEDENT study found nesiritide, but not
dobutamine, to be free of proarrhythmic activity
in CHF management. A frequent dilemma in clinical
practice is distinguishing dyspnea due to CHF
from other causes.
BNP is a protein secreted from the cardiac
ventricles in response to pressure overload. Several
studies have demonstrated that the BNP blood concentration
of patients with CHF was much higher than in patients
without heart failure.
BNP concentration measurement appears to be a
sensitive and specific test to diagnose CHF. BNP
becomes elevated even before signs and symptoms
of CHF are manifested. Thus, BNP could be used
as a screening tool in CHF, enabling early initiatiation
of anti-heart failure therapy.
Summary by: Summary by: Rachel Hajar, MD
Dr. Edward Rowland, St. George’s Hospital & Medical School, London, United Kingdom
|
Interventional cardiac electrophysiology is a growing field over the last
fifteen years.
The first energy source used for catheter ablation
was direct current (DC).
However, DC shock ablation, or fulguration,
never achieved widespread use because of a high
incidence of complications related to the high
energy discharge.
Risks of the procedure included cardiac
rupture, depressed left ventricular function,
and death. Radiofrequency (RF) catheter ablation
has become an important therapy in the management
of patients with various types of tachyarrhythmia.
Delivered from the tip of a catheter to
the endocardial surface, RF energy produces controlled
focal tissue ablation, as compared with the more
extensive damage caused by DC fulguration. RF
catheter ablation is considered first-line therapy
for some arrhythmias and an important technique
for others that are refractory to pharmacologic
therapies.
RF ablation has been used in atrioventricular
reentrant tachycardia (AVRT) associated with the
WPW syndrome or a concealed accessory pathway,
AV nodal reentrant tachycardia, atrial tachycardia,
atrial flutter, idiopathic ventricular tachycardia
and bundle branch reentrant ventricular tachycardia.
It has also been used to establish rate control
in refractory atrial fibrillation. In this setting,
the technique involves catheter ablation of the
AV junction with permanent pacemaker implantation.
Complications of RF ablation include those related
to vascular access including bleeding, infection,
hematoma, vascular injury, and thromboembolism.
Other complications are: heart block requiring
permanent pacemaker, radiation exposure, pulmonary
hypertension due to pulmonary vein stenosis occurring
near the junction with the left atrium. Cardiac
trauma, including myocardial perforation, tamponade,
and infraction can occur. New arrrrhythmias have
been reported. New arrhythmias could occur since
radiofrequency lesions themselves might serve
as arrhythmogenic foci. Recent advances in mapping
techniques include activation mapping, and in
combination with conventional pace, and entrainment
mapping.
These are sophisticated and precise techniques
that help position the ablation electrode in the
proper site to treat the given arrhythmia.
The indications and advantages of each was
discussed Current research is focused on improving
mapping techniques, developing new imaging modalities,
creating new catheter designs for enhanced radiofrequency
energy delivery, and evaluating new energy sources
for catheter ablation. Together, these efforts
will undoubtedly extend the indications and improve
the efficacy of catheter ablation.
At present, they are concentrated on developing
better catheter ablation techniques for the treatment
of AF and VT related to chronic coronary artery
disease. Even though RF energy is vastly superior
to and safer than DC energy, efforts continue
to look for alternate energy sources for catheter
ablation such as cryothermal and laser ablation.
Summary by: Summary by: Dr. Mohammed Numan
Dr. Francois Lacour-Gayet, Head, Dept. of Pediatric Cardiac Surgery Eppendorf
University Hospital, Hamburg, Germany
|
There is growing pressure from many groups regarding quantification of results in surgery for congenital heart malformations. Institutions wish to monitor the quality of their surgical programs, parents want to know the chances of success for their children, and health care financers (insurance companies; governmental agencies) require evidence of return on their investment. However, the complexity of the subject makes comparison of results between surgeons, institutions or countries difficult. As a start to addressing this problem, a database was first developed by the European Congenital Heart Surgeons Foundation. In the absence of actual quantification of risks, a consensus was then obtained among surgeons regarding the difficulty of various procedures and the factors, which are thought to increase the hazards of the operation. This has now been used to provide a preliminary classification of risk, and by inference the expected outcome, for many common congenital heart operations.
Summary by: Summary by: Roxane Mckay, MD
Dr. Zuhair Youssef Al-Halees, Chairman Dept. of Cardiovascular Disease
King Faisal Specialist Hospital & Research Centre, Riyadh - Saudi Arabia
|
The pulmonary autograft offers the advantages of a viable tissue valve for young patients who need aortic valve replacement and it has been used extensively at the King Faisal Specialist Hospital in Riyadh, Saudia Arabia. All valves were implanted as complete aortic roots, often with extensive resection of subvalvar obstruction. Early survival has been excellent. Reoperation has been necessary for infection and failure of the autograft, but, in contrast to the experience of many institutions, failure of the homograft in the pulmonary position has been rare.
This may be related to the use of immunosuppression postoperatively.
Summary by: Roxane Mckay, MD
|
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