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PATRON Dr.A.M.ShamimCHAIRMAN,EDITORIAL
COMMITTEEDr.M.Jalaluddin,FCPSEDITORIAL BOARDDr.Abduz
Zaher,FRCPDr.A.K.Miah,PhDDr.A.R M.Sohrabuzzaman,FCPS Dr.Fakrul
Islam,FACCDr.Reyan Anis,FRCPDr.Arun Kumar Sharma,FACC Dr.Md.Elias
Ali,MDDr.Lutfor Rahman,MSDr.Md.Lokman Hossain,MSDr.Salauddin Ahmed
Selim,DA Dr.A.H.M.Abul Monsur,D CardEDITOR Dr.Baren
Chakraborty,FRCPASSISTANT EDITOR Dr.Mahbubor Rahman,FRCP Dr.Fahmida
Zaman,FACCCHIEF EXECUTIVEDr.(Brig Gen) Manz0orA.Mollah (Retd.
)SECRETARY,PUBLICATION COMMITTEEAIEmran ChowdhuryEDITORIAL STAFF
Kuddus Hawladar Nipun Md.Mizanur RahmanThe world's rst successful
heart valve surgery was performed 90 years ago by Elliot
Cutler.Forty years later,Albert Starr and Lowell Edwards,an
engineer,collaborated to pioneer the development of the rst
successful,Food and Drug Administration (FDA) approved,mechanical
caged-ball heart valve.Since then,more than 80 mechanical heart
valve models have been developed.Patients undergoing mechanical
mitral valve replacement require lifelong
anticoagulation.Contributing to the long-standing success of these
interventions,anticoagulation remains a key step in the prevention
of valve thrombosis and thromboembolic stroke.The best approach in
anticoagulant optimization is debatable.Still warfarin is the drug
of choice.The search for alternative prophylaxis often pushes
clinicians to off-label options.Novel anticoagulant, dabigatran has
been approved in the United States for patients with nonvalvular
atrial brillation.Due to its perceived convenience,some physicians
have begun to prescribe it off label for mechanical valves. In this
issue of journal Rahman et al published their experience of
treating prosthetic valve thrombosis with prolonged streptokinase
infusion in 15 cases of documented valve thrombosis and outcome of
this modality of treatment appears to be execellent in this series
of patients.Out of 15 patients treated only 1 patient died.Warfarin
is also the drug of choice in pregnant women with prosthetic
mechanical valve.In this issue of journal Ganguly et al presented
their experience of treating 11 pregnant women with warfarin.There
was no documented warfarin embryopathy in their series.The authors
opined that warfarin appears to be the anticoagulant of choice for
the pregnant women with mechanical prosthetic heart valves during
pregnancy. Although coronary artery bypass graft (CABG) has been
considered the "gold standard" for unprotected left main coronary
artery disease (CAD) revascularization,more recently percutaneous
coronary intervention (PCI) has emerged as a possible alternative
mode of revascularization in carefully selected patients.In the
present issue of the journal Momenuzzaman et al published their
experience of unprotected Left main (LM) angioplasty on 79
consecutive patients in their hospital and the outcome appears
encouraging.No death was noted during the procedure.Out of these 79
patients only 1 patient (1.3%) needed emergency CABG for LM
dissection and another 4 patients (5.1%) died during limited
followup.In this cohort of LM disease 34% patients presented with
stable angina,32% with unstable angina,22% with post MI angina and
12% with post PCI angina.In stable patients with signicant LM
disease still CABG is considered as the gold standard (Class 1
indication) from the survival point of view (ACC/ AHA Guideline
Circulation.2012; 126: e354-e471) and PCI to improve survival is
reasonable as an alternative to CABG in selected stable patients
with signicant (250%) diameter stenosis) unprotected left main CAD
(Class Ila indication). lain: . ;i'l= Iiifl. '=Z I 1 , i'iI'iIig'
1.::Ti our I 1:-iiiuiaitilsi Igkjii -11-15 V - -I I -II/0' = +
'-I!Iii:iii-iiiiII, !lii:1t18 years who underwent an elective,non-
outpatient,open surgical procedure were enrolled.Subcutaneous
enoxaparin 1 mg/ kg,twice daily,was used asbridging
anticoagulation.The demographics,co- morbidities,and preoperative
(medications,echocardiographic ndings,laboratory results)
andpostoperative data were evaluated for their association with the
occurrence of perioperative adverse events.The incidence of
perioperative adverse cardiovascular (10.8% vs 10.7%,p= O.985) and
noncardiovascular (11.9% vs 11.4%,p= O.989) events was similar in
those patients with and without PHVs.Bleeding (18.6% vs 14.2%,p=
O.989),thromboembolism (3.6% vs 2%,p=0.989),and mortality at 3
months (1.4% vs 1.3%,p=0.825) were also similar for the 2
groups.This study concluded that with close follow-up and strict
adherence to the guidelines,patients with PHVs and patients with
native heart valves undergoing noncardiac and nonvascular surgery
have a similar risk of mortality and morbidity*. Unfractionated he
arin (UFH) versus low molecular weight eparins (LMWH)The management
of anticoagulation in patients with a PHVs can be especially
difcult in two clinical situations:in patients who must withhold
antithrombotic treatment before and after a surgery/ invasive
procedure,and in those
10. _pr9i_': *;i_i, v I ; .:i_uJiui_m;,'; m_1r; lsa1u526
ZaherA,Rahman M,KhayerA,Zaman R,et alwho have a bleeding
complication while receiving warfarin/acenocumarol.Although low
molecular weight heparins (LMWH) are an attractive alternative to
other anticoagulant strategies because of their pharmacokinetic and
pharmacodynamic properties,there is not enough clinical evidence to
consider their effectiveness and safety to be denitive in both
mentioned settings.One observational prospective study was carried
out on a cohort of patients with PHVs and various thromboembolic
risk factors.These patients were admitted in a hospital in several
clinical situations that led to interruption of treatment with
acenocumarol and were treated with enoxaparin as an alternative to
other methods.All consecutive patients with mechanical heart valves
were admitted in a hospital between May 1999 and January 2002 who
had to interrupt treatment with acenocumarol and were treated with
enoxaparin as an alternative to other methods were enrolled.All
patients were followed up through clinical history during the
hospitalization and by telephone after discharge to detect
thromboembolic events.82 patients were identied and followed up for
a mean of 2.8 months (range 1.5-3.5 months) after discharge.61 of
them (74%) had one or more associated thromboembolic risk
factors.Acenocumarol was interrupted to perform an invasive
procedure in 74 patients and because of haemorrhagic complication
in another 8 patients.Most patients received the standard
enoxaparin dose (1 mg/ kg at 12 hour intervals).There were 8 minor
and 1 major bleeding events during enoxaparin treatment.No
thromboembolic complications were clinically detected during
hospitalization or during follow up. The authors of the study
opined that enoxaparin may be an effective and relatively safe
substitute anticoagulant for patients with mechanical heart valves
who must withhold acenocumarol.This study showed that enoxaparin in
the high risk postoperative period is at least as safe and
effective as UFH5.Clinical outcomes were not statistically
different for patients receiving LMWH or UFH in another reported
series.Nevertheless,there is a widely held notion that LMWH is not
safe to use as bridge therapy for patients with mechanical
PHVs.Recent prospective bridge studies do not support that
view,demonstrating that LMWH used as bridge therapy is associated
with low risks for thromboembolism and major bleeding even in
patients with mechanical valves.Accordingly,the latest ACCP
guidelines for perioperative management of patients on
antithrombotic therapy recommend therapeutic-dose LMWH over IV UFH
for bridge therapy,including in patients with mechanical heart
valves7. Likewise latest guidelines from the American College of
Cardiology and American Heart Association on management of patients
with valvular heart disease endorse LMWH as an option for bridge
therapys. Management is complicated by the absence of randomized
trials examining peri-operative anticoagulation
management.Thromboembolic risk increases substantially when oral
anticoagulation is discontinued and valve thrombosis may be
inapparent for 1-2 months.This delayed diagnosis makes it difficult
to identify the incitingBangladesh j Cardiol,2013;
04-05(1):525-29event,either clinically or in experimental
trials.Furthermore,the absence of early postoperative events may
falsely suggest that peri-operative anticoagulation was safe and
adequate.The approach to management therefore remains
controversial.Seamless oral anticoagulation is preferred whenever
possible and this is safe for a range of minor procedures,including
cardiac catheterisation,dental and ophthalmic surgery"5'.Major
surgical procedures require withdrawal of oral anticoagulation
before surgery to lower the INR to 12 months n= l99 n=47 n=282
Streptococci 4 (2) 6 (13) 84 (30) Enterococci 16 (8) 5 (l l) 31
(11) Staphylococcus aureus 56 (28) 6 (13) 62 (22) Coagulase
negative staphylococci 60 (30) I7 (36) T 34 (I2) HACE K Group 11
(4) Gram negative bacilli 23 (12) 2 (4) 13 (5) Fungi (Candida
species) 17 (8) 4 (8) 3 (1) Polyrnicrobial/ miscellaneous 7 (3) 4
(8) l2 (4) Diphtheroids 9 (4) 5 (2) Culture negative 7 (3) 3 (6) 27
(I 0) PathologyInfection of mechanical prosthesis starts at the
interface between sewing cuff and the native tissue which can lead
to loosening of sutures,periprosthetic leaks,ring abscesses and
fistulous tracks into surrounding tissues.Valvular incompetence
with congestive heart failure,heart block,systemic embolization of
vegetations and multiorgan infections with sepsis are important
complications. With bioprosthetic valves,infection is often
restricted to the cusps.The thrombotic vegetations in the
biosynthetic material can lead to cusp rupture and perforation.If
the sewing cuff is involved,the pathologic process is similar to
that of mechanical prosthesis.
15. /Iklilaruzzanran M,Nawaz TEarly Onset and Late Onset
Prosthetic Valve EndocarditisProsthetic valve endocarditis (PVE) is
categorized as early onset (EOPVE) and late onset (LO-PVE).However
there is no general agreement on time and some authors consider 60
days,7 less than 6 month or 1 year2 after valve replacement as
EO-PVE and thereafter as LO-PVE.V The risk of developing PVE is
highest within the initial 12 months after replacement surgery with
a peak during the rst 2 months.9Clinical presentationOne or more of
the followingV Fever V Embolism with stroke and peripheral
involvement' Heart failure ' Metastatic infection V New or changing
murmurV SplenomegalyV New conduction abnormalities Most common
causes of death are heart failure,arrhythmias,multi organ failure
in the setting of severe sepsis and brain emboli.Infection with low
virulence organisms manifest with a subacute or chronic course.
DiagnosisRevised Duke criteria may be used as a diagnostic scheme
when PVE is suspected. They are based on identication of causative
organism and results of Transesophageal Echocardiography (TEE). ~
Culture and susceptibility testingGrowth of causative organism in
culture is currently the only method to determine antibiotic
sensitivity.Susceptibility testing is performed with isolates from
blood,surgical specimens including embolic fragments,periprosthetic
tissues,vegetations and tissue fragments obtained from
bioprosthetic valves or abscess debribement.Positive blood cultures
have been found between 78% to 91% of PVE.9~' Serologic methods and
PCR are also available for the detection of some organisms. TEE is
mandatory in all cases of suspected PVE.TEE is superior to
Transthoracic Echocardiography for the detection of valvular
vegetations,abscesses and perivalvular extension of infection.
TreatmentThe appropriate therapy approach is medical treatment
which may require combination with surgical treatment.Surgical
treatment approachACC/ AHA guideline summary:Surgery forHm:2 1
prosthetic valve endocarditis (PVE)2Class I There is evidence and/
or general agreement that surgery is indicated in patients with PVE
who develop one of the following: 1 Valve dysfunctionV Dehiscence
seen by cine uoroscopy or echocardiographyV Evidence of increasing
valve obstruction or worsening regurgitationI Complications such as
abscess formation531 Bangladesh J Cardiol,2013;
04-05(1):530-33Class Ila - The weight of evidence or opinion is in
favor of the usefulness of surgery in patients with PVE who develop
one of the following: V Persistent bacteremia or recurrent emboli
despite appropriate antibiotic therapyV Relapsing infectionClass
III - There is evidence and/ or general agreement that surgery is
NOT indicated in patients with PVE in the following setting: V
Uncomplicated IE caused by a rst infection with a sensitive
organismOther clinical situations in which surgical intervention
should be considered are fungal PVE,S.aureus PVE,Pseudomonas and
probably multi-resistant Enterococcus PVE. Surgery involves valve
replacement with perivalvular tissue reconstruction. Medical
treatment approachIn patients with no indication for
surgery,antibiotics with close monitoring is necessary. In patients
without indication for urgent surgery,antibiotics with monitoring
is often adequate initial treatment. In patients with haemodynamic
stability,surgery may be postponed until completion of antibiotic
therapy.Early valve replacement without an urgent indication can
increase the chance of mortality. Bactericidal agents with
synergistic action should be given in combination.These regimens
are displayed in Table 3. ~ ACCP guidelines 2012 suggest that in
patients on vitamin K antagonist (VKA) with PVE,VKA may be
discontinued at the time of initial presentation until it is clear
that invasive procedures will not be required and patient has
stabilized without signs of CNS involvement.When patient is stable
without contraindications or neurologic complications,VKA therapy
may be restarted.The risk of thromboembolism in PVE is higher than
native valve endocarditis,with reports between 50% and 88% of
patients.Antimicrobial therapy is the mainstay of prevention of
embolisation and should be started without delay.'4Antimicrobial
therapy of PVE in adults1kl"m :4.with normal renal functionPVE
caused by Staphylococci Oxacillin/ Methicillin susceptible strains~
Nafcillin or Oxacillin or Flucloxacillin 12 g per 24 h IV in 4 to 6
equally divided doses for 26 wks or Vancomycin 30 mg/ kg per 24 h
IV in 2 equally divided doses for 36 wks plus~ Rifampin 900 mg per
24 h IV or P0 in 3 equally divided doses for 26 wks plus~
Gentamicin 3 mg/ kg per 24 h IV or IM in 2 or 3 equally divided
doses for the rst 2 wks
16. .2 .9 -o E u >.in {'5 5-:o 9' =U 4-5 :o L) 532/ Il
0.12ug/ mL0 Aqueous penicillin G 24 million units per 24 h IV
either continuously or in 4 or 6 equally divided doses for 6 wks
or0 Ceftriaxone 2 g/24 h IV or IM in 1 dose for 6 wksplus0
Gentamicin 3 mg/ kg per 24 h IV or IM in 1 dose or 3 equally
divided doses for 6 wksCulture negative PVE Early onset (31 year)0
Vancomycin 30 mg/ kg per 24 h IV in 2 equally divided doses 6 wks
plus0 Gentamicin sulfate 3 mg/ kg per 24 h IV/ IM in 3 equally
divided doses 2 wks plus0 Rifampin 900 mg/24 h PO/ IV in 3 equally
divided doses 6 wks plus0 Cefepime 6 g/24 h IV in 3 equally divided
doses 6 wksLate (>1 year) 0 Vancomycin 30 mg/ kg per 24 h IV in
2 equally divided doses 6 wks plus0 Gentamicin sulfate 3 mg/ kg per
24 h IV/ IM in 3 equally divided doses 2 wks plus0 Rifampin 900
mg/24 h PO/ IV in 3 equally divided doses 6 wks plus0 Ciprooxacin
1000 mg/24 11 P0 or 800 mg/24 h IV in 2 equally divided doses 6
wksPVE caused by Enterococci Strains susceptible to penicillin and
Vancomycin;high- level resistance to gentamicin and streptomycin
must be determined: 0 Aqueous penicillin G 18-30 million units per
24 h IV either continuously or in 6 equally divided doses for 6 wks
or Ampicillin 12 g per 24 h IV in 6 equally divided doses for 6 wks
or0 Vancomycin 30 mg/ kg per 24 h IV in 2 equally divided doses for
6 wks;not to exceed 2 g per 24 h unless concentrations in serum are
inappropriately lowplus0 Gentamicin 3 mg/ kg per 24 h IV or IM in 3
equally divided doses for 6 wksIntrinsic penicillin resistance
(penicillin/ ampicillin MIC 232 uglmL)0 Vancomycin 30 mg/ kg per 24
h IV in 2 equally divided doses for 6 wks plus0 Gentamicin 3 mg/ kg
per 24 11 IV or IM in 3 equally divided doses for 6 wksPVE caused
by Fungi0 Initial phase surgery plus amphotericin B (0.7 to 1mg/ kg
per day) along with 5-ucytosine (1501ng/ kg per day in 4 divided
doses) for 2 6 weeks.Liposomal amphotericin is an alternative drug.
0 For Candida PVE,this should be followed with suppressive second
phase of oral therapy with uconazole (200 to 400 mg daily or
another triazole) forPVE caused by HACEK 0 Ceftriaxone 2 g per 24
11 IV or IM in 1 dose for 6 wks or0 Ciprooxacin 1000 mg per 24 h P0
or 800 mg per 24 h IV in 2 equally divided doses for 6 wksprolonged
periods. Prevention0 Patients with prosthetic valves are at
relatively high risk of PVE. 0 Antibiotic prophylaxis is reasonable
for all dental procedures that involve manipulation of gingival
tissues or periapical region of teeth or perforation of oral
mucosa. 0 Antibiotic prophylaxis is reasonable for procedures on
respiratory tract or infected skin,skin structures,or
musculoskeletal tissue. 0 In patients scheduled for elective
cystoscopy and/ or other urinary tract manipulation who have
enterococcal urinary tract infection or colonization,antibiotic
therapy to eradicate enterococci from the urine before procedure
may be reasonable.If procedure is not elective,it may be reasonable
to give antimicrobial regimen active against enterococci. 0
Prophylaxis during dental procedures may be given with single dose
oral amoxicillin 2 gms 30-60 minutes before the
procedure.Alternatives are oral clarithomycin,azithromycin or
ceftriaxone 1gm IV/ IM. 0 Common diagnostic procedures such as
bronchoscopy,gastrointestinal endoscopy,imaging studies with
contrast and TEE carry minimal risk and are not recommended for
prophylaxis. -15
17. Aklitaruzzainan M,Nawaz TReferences1. Mylonakis
E,Calderwood SB.lnfective endocarditis in adults.N EnglJ Med
2001;345:1318-30.2. Rivas P,Alonso J,Moya J,et al.The impact of
hospital acquired infections on the microbial etiology and
prognosis of late-onset prosthetic valve endocarditis.Chest
2005;128:764-71.3. Pibarot P,Dumesnil JG.Prosthetic heart
valves.Selection of the optimal prosthesis and long term
management.Circulation 2009;119:1034-484. Karchmer AW.Antimicrobial
therapy of prosthetic valve endocarditis.Uptodate 20135.
Jegatheeswaran A,Butany J.Pathology of infectious and inammatory
diseases in prosthetic heart valves.Cardiovasc Pathol
2006;15:252-55.6. Anguera I,Miro JM,San Roman JA,et al.Periannular
complications in infective endocarditis involving prosthetic aortic
valves.AmJ Cardiol 2006;98: 1261-68.7. Sandre RM,Shafran
SD.lnfective endocarditis:review of 135 cases over 9 years.Clin
Infect Dis 1996;22:276-86.8. Tornos B,lung B,Permanyer-Miralda G,et
al.lnfective endocarditis in Europe:lessons from Euro heart
survey.Heart 2005;91:571-75.9. Wang A,Athan E,Pappas PA,et
al.International Colloboration on Endocarditis- Prospective Cohort
Study Investigators.Contemporary clinical prole and outcome533
Bangladesh J Cardiol,2013; 04-05(1):530-33of prosthetic valve
endorcarditis.JAMA 2007;297:1354-61. 10. LiJS,Sexton DJ,Mick
N,Nettles R,Fowler VG Jr,Ryan T,Bashore T,Corey GR.Proposed
modications to the Duke criteria for the diagnosis of infective
endocarditis.Clin Infect Dis 2000;30:633-38.11. Lopez J,Revilla
A,Vilacosta I,et al.Denition,clinical prole,microbiologic spectrum
and prognostic factors of early onset prosthetic valve
endocarditis.Eur HeartJ 2007;28:760-5.12. Bonow R0, Carabello
BA,Chatterjee K,et al.ACC/ AHA 2006 guidelines for the management
of patients with valvular heart disease.A report of the American
College of Cardiology/ American Heart Association Task Force on
Practice Guidelines (Writing committee to revise the 1998
guidelines for the management of patients with valvular heart
disease). J Am Coll Cardiol 2006; 48:e1.13. Baddur LM,Wilson
WR,Bayer AS,et al.AHA/ IDSA.lnfective endocarditis.Circulation
2005;111;e394-e434.14. Whitlock RP,Sun JC,Fremes SE.Antithrombotic
and thrombolytic therapy for valvular disease.Chest 2012 Feb;141(2
Suppl): e576S-600S. 15. Wilson W,Taubert KA,Gewitz M,et
al.Prevention of infective endocarditis.Guidelines from the
American Heart Association.Circulation 2007;116:1736-54.16.
National Institute of Clinical Excellence.Prophylaxis against
infective endocarditis.2008. NICE Clinical Guideline 64CH-,
l!1i|1!, lE! l!1t31,. /93,123 1111-Jkall/ I
18. 534 Hossain L,Ahmed / I, Ahsan 5Bangladesh J Cardiol,2013;
04-05(1):534-38IChoice of Prosthetic Valves:iviechonicolValves
Versus Tissue ValvesL Hossain,A Ahmed,S Ahsan Labaid Cardiac
Hospital,Dhaka,Bangladesh. The ideal prosthetic heart valve (PHV)
that combines excellent hemodynamic performance and long-term
durability without increased thromboembolic risk or the need for
long-term anticoagulation does not exist.Hence,patients and their
physicians need to choose between a mechanical and a tissue
(bioprosthetic) valve.In general,the advantageous durability of
mechanical valves is offset by the risk of thromboembolism and the
need for long- term anticoagulation and its associated risk of
bleeding.In contrast,bioprosthetic valves do not require long-term
anticoagulation yet carry the risk of structural failure and
reoperation. There is an extensive variety of prosthetic valves.The
two most commonly used are the mechanical valve and the stented
tissue valve.The two common types of mechanical valves,tilting-disc
and bileaet valves have comparable durability and both require
life-long anticoagulation therapy due to their associated
thrombotic risk.Mechanical valves have advantages and
disadvantages,the most important of which is their greater
durability (20-30 years) than tissue bioprosthetic valves (10-15
years).Their greater durability translates into lower reoperation
rates among these patients,compared with patients with
bioprosthetic valves.Although mechanical valves are more durable
than bioprosthetic valves,mechanical valves also have several
disadvantages that a provider and patient must consider.Blood ow
around the mechanical valve results in high sheer stresses,which
can result in platelet activation and a higher risk for thrombosis
on the valve surface and a subsequent risk for embolism.Given this
risk,all patients with mechanical heart valves require lifelong
anticoagulation,most commonly with a vitamin K antagonist (VKA)
such as warfarin.Although warfarin use is efcacious in reducing
thrombosis risk,it heightens hemorrhagic risk2 For example,a
60-year-old male with a mechanical valve replacement has a lifetime
risk of bleeding of 41% compared with a 12% risk in a
similarDr.Md.Lokman Hossain,M5 (CTS),Senior Consultant,Cardiac
Surgery.Dr.Amran Ahmed,MD,Consultant Cardiac Surgeon Dr.Md.Shameem
Ahsan,MBBS,Registrar,Cardiac SurgeryCorrespondence:Dr.Md.Lokman
Hossain MS (CTS), Senior Consultant,Cardiac Surgery. Labaid Cardiac
Hospital,House-I,Road-4, Dhanmondi,Dhaka-I205, Bangladesh.Tel-
880-2-8610793-8. e-mail- Iokman54@hotmail. compatient with a
bioprosthetic valve replacement3.Two historic randomized clinical
trials compared outcomes after valve replacement with a
rst-generation porcine heterograft and the original Bjork-Shiley
tilting-disc mechanical valve:the Edinburgh Heart Valve
Trial,conducted between 1975 and 1979 with an average follow- up of
12 years and the Veteran Affairs (VA) Cooperative Study on Valvular
Heart Disease,conducted between 1979 and 1982 with an average
follow-up of 15 years"'5.The Edinburgh trial alone showed a small
survival advantage associated with a mechanical valve in the aortic
but not in the mitral position;both trials showed increased
bleeding associated with mechanical valves and increased
reoperation with tissue valves;and both showed that structural
failure of tissue valves and overall thromboembolic complications
were greater after mitral than after aortic valve
replacement.Although these trials are notable for their
prospective,randomized design,their major limitation is that
comparisons were made between rst-generation porcine heterografts
and the Bjork-Shiley mechanical valve,all of which are now
obsolete.Thus,the ability to extrapolate these data to decisions
made in modern practice is limited. The ideal valve substitute
should mimic the characteristics of a normal native valve.In
particular,it should have excellent hemodynamics,long
durability,high thromboresistance,and excellent
implantability.Unfortunately,this ideal valve substitute does not
exist,and each of the currently available prosthetic valves has
inherent limitations.Three basic types of mechanical valve design
exist:bileaet,monoleaet,and caged ball valves. Caged ball
valves,which consist ofa silastic ball with a circular sewing ring
and a cage formed by 3 metal arches,are no rarely
implanted.Monoleaet valves are composed of a single disk secured by
lateral or central metal struts.Bileaet valves are made of2
semilunar disks attached to a rigid valve ring by small hinges.The
opening angle of the leaets relative to the annulus plane ranges
from 75 to 90,and the open valve consists of 3 orices:a small,slit-
like central orice between the 2 open leaets and 2 larger
semicircular orices laterally7. The original mechanical prosthesis
was the ball-and-cage (StarrEdwards) valve,in which a silastic ball
was housed in a metal cage.This was followed by second-generation
tilting disc valves (eg Bjork- Shiley) where a single disc opens
and closes on a hinged strut.The current generation comprises
bileaet valves
19. Hossain L,/Iluned / I, / ll1S(1l1 S Choice of the aortic/
mitral prosthesis.In favour of a mechanicalprosthesis535
Bangladesh] Cardiol,2013; 04-05(1):534-38A mechanical prosthesis is
recommended according to the desire ofthe informed patient and
ifthere are no contraindications for long-term
anticoagulationClassadeterioration! A mechanical prosthesis is
recommended in patients at risk ofaccelerated structural valveA
mechanical prosthesis is recommended in patients already on
anticoagulation as a result ofhaving a mechanical prosthesis in
another va Ive position. inthe aortic position and