Drugs commonly used in valvular heart
disease
The role of the pharmacist
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Sukhjinder Nijjer is specialty registrar,
cardiology, at the Royal Brompton Hospital, London
Jasdeep Gill is
a foundation
doctor, general medicine, at Southampton General Hospital
Sandeep
Nijjer is a clinical lecturer at the University of London School
of Pharmacy |
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Dr E. Walker/SPL
Bacterial endocarditis of an artificial heart
valve (ribbed) |
SUMMARY
Drug therapy in valvular heart
disease (VHD) is used to delay surgical intervention, to stabilise the
patient pre- and post-surgery, to control symptoms in those unsuitable
for surgery and to treat comorbidities. The drugs commonly used in VHD
are listed in Panel 1
Following valve replacement operations, patients are at risk of thrombosis
and endocarditis. This article focuses on the prevention of these conditions.
It is estimated that anticoagulant-related bleeding or thrombosis accounts
for 75 per cent of prosthetic valve complications.
Guidelines published
by the European Society of Cardiology and joint guidelines from the American
College of Cardiology and American Heart Association state that effective
thromboprophylaxis requires careful use of anticoagulation and antiplatelet
therapy, together with management of thrombosis risk factors such as
atrial fibrillation (AF), left ventricular dysfunction and previous thromboembolism.
Patients with mitral
valve stenosis (see p121) and AF should be anticoagulated
to reduce the risk of thromboembolism.
It is recommended that patients with mechanical valves, or with bioprostheses
and additional risk factors, take oral anticoagulants for life. The
ESC recommends that patients with bioprostheses and no additional risk
factors receive oral anticoagulation for the first three months after
their valve replacement operation (target INR 2.5), followed by life-long
treatment
with low dose aspirin (75–100mg daily). Patients with bioprostheses
without other risk factors may not need any anticoagulation.
Anticoagulation therapy is guided by the type of replacement valve (mechanical
or biological, see p121), the position of the implant, associated risk
factors (eg, AF), bleeding risk and the patient’s age.3 While a variety
of vitamin K antagonists have been used for oral anticoagulation following
valve replacement, the British Committee for Standards in Haematology recommends
warfarin.
Anticoagulation (usually with unfractionated heparin) should be started
as soon as possible after the operation. Once the risk of bleeding falls
below that of thrombosis, oral warfarin is introduced. The risk of thromboembolism
and bleeding is greatest during the first month post valve replacement
surgery, so the patient’s INR must be frequently monitored.
Previous
practice was to provide a target INR range (eg, 2–2.5). Now a precise
target is set to reduce the time during which the patient is outside
the optimal anticoagulation level.
Drugs commonly used in
valvular heart disease
• Anticoagulants
• Antibiotics (for endocarditis
prophylaxis)
• Angiotensin-converting enzyme inhibitors
• Dihydropyridine calcium channel blockers
• Beta-blockers
• Diuretics
• Nitroprusside
• Inotropic agents |
The role of the pharmacist
Pharmacists have an important role in ensuring the
safe and effective use of medicines in patients with VHD, monitoring
therapy, helping to prevent adverse effects, managing any interactions
and promoting compliance with anticoagulation and antiplatelet therapy.
Educating patients about antibiotics for the prophylaxis of endocarditis
and on the signs of suspected bleeding related to anticoagulation
therapy is important. Other warning symptoms include sudden dyspnoea
in prosthetic valve patients, in which case obstructive valve thrombosis
could be suspected. Pharmacists can also suggest compliance aids
to patients requiring life-long anticoagulation, and if appropriate,
use of home INR monitoring.
On the wards, it is essential to alert other members of the multidisciplinary
team to patients with prosthetic valve replacements, because these
patients will need measures such as heparin infusions and antibiotic
prophylaxis that may otherwise be forgotten. Pharmacists should also
ensure that appropriate drug regimens are used and that doses are
optimised. Drug interactions should also be recognised and managed.
Pharmacists should also recognise possible iatrogenic causes of VHD.
As described in the first
part of this feature (p124), people seeking
weight loss treatments may use unlicensed preparations containing
the appetite suppressants fenfluramine, dexfenfluramine and phentermine.
These can cause VHD by activation of valve 5-HT2B receptors.
It
would also be appropriate to counsel recreational users of methylenedioxymethamphetamine
(“ecstasy”) because this drug has been associated with
valvulopathy. Pharmacists should ensure that patients with Parkinson’s
disease using dopamine agonists (cabergoline and pergolide) for periods
longer than six months are monitored for clinically significant valvulopathy. |
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Hospital
Pharmacist