Transcript Ischemic Heart Disease

Ischemic Heart
Disease
M M Elmazar
BUE
Ishemic heart disease
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Definition:
Ishemic heart disease
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Ischemic heart disease (IHD) is also known as coronary
heart disease (CAD).
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It is the lack of oxygen and decreased or no blood flow to the
myocardium resulting from coronary artery narrowing or
obstruction.
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It may present in many different forms: eg.
ACS (Acute coronary syndrome),
AMI (Acute myocardial infarction) with ECG changes, STEMI
or NSTEMI
Chronic stable exertional angina or unstable angina
Ischemia without symptoms
Ischemia due to coronary artery vasospasm (variant or
Prinzmetal’s angina)
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Pathophysiology:
Ishemic heart disease
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Major determinants of myocardial oxygen demand (MVo2)
heart rate, contractility and intramyocardial wall tension
during systole.
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A useful indirect estimate of MVo2 is the double product (DP)
DP = HR X SBP (heart rate x systolic blood pressure)
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Prime determinants in occurrence of ischemia are:
MVo2 and the caliber of resistance vessel delivering
blood to the myocardium.
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The coronary system
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large epicardial vessel (R1)
intramyocardial arterioles (R2)
Normally, resistance in R2 > R1.
Myocardial blood flow α coronary driving pressure
α 1 / arteriolar resistance
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Ishemic heart disease
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Atherosclerotic lesions occluding R1 increase arteriolar
resistance, and R2 can vasodilate to maintain coronary blood
flow.
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With greater degrees of obstruction, this response is inadequate
and R2 vasodilation is insufficient to meet O2 demand
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Severe stenosis (>70%)
stenosis (50 – 70%)
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- ischemia & symptoms at rest.
- coronary reserve is
diminshed due to vasoconstriction
- obstruction is non consistent
- reduces blood flow
Abnormalities of ventricular contraction can occur resulting in
heart failure, increased MVo2.
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Clinical presentation:
Ishemic heart disease
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Characteristics of angina pectoris include: sensation of
pressure, tightness over the sternum or near to it
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Pain may radiate to the left arm, shoulder or other areas.
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Duration: between 30 seconds – 30 minutes.
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Precipitating factors: exercise, cold, anger, fright.
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Patients with Prinzmetal’s angina are more likely to experience
pain at rest and in the early morning hours.
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Unstable angina is stratified into categories of low, intermediate
or high risk for short-term death or non-fatal MI.
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Episodes of ischemia may also be painless or “silent” due to a
higher threshold and tolerance for pain.
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Diagnosis :
Ishemic heart disease
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Important aspects of the clinical history: nature and duration
of pain, precipitating factors, response to nitroglycerine,…..
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Existing personal risk factors for coronary heart disease:
smoking, HT, DM
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A detailed family history should be obtained
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Physical examination including cardiac and noncardiac
examinations (aortic aneurysms, peripheral vascular diseases)
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Laboratory tests eg. Hemoglobin, ECG, FBG, lipoprotein(a),
Troponin T or I, myoglobin, CK-MB
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Exercise tolerance (stress) testing (ETT) is recommended
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Radionuclide angiocardiography (EF), ultrarapid computed
tomography, echocardiography may be considered.
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Desired outcome:
Ishemic heart disease
The goals of treatment to relieve the patient’s symptoms, maintain
functional capacity, minimize adverse effects of treatment, and prevent
progression to MI.
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Treatment:
I) Modification of risk factors:
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Primary prevention by modification of risk factors will reduce
the prevalence of IHD.
Secondary intervention is effective in reducing morbidity and
mortality.
Risk factors are additive and can be classified as
- alterable: smoking, HT, hyperlipidemia, stress, etc…..
- unalterable: gender, age, (DM), etc….
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II) Pharmacologic Therapy:
Ishemic heart disease
a) B-Adrenergic Blocking Agents:
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Ideal candidates for B blockers include patients with chronic
exertional stable angina, those with coexisting HT,
supraventricular arrhythmias, angina and HF.
B blockers are first line drugs in chronic angina. They can be
used as monotherapy or in combination with Ca channel
blockers and nitrates.
If B blockers not tolerated or ineffective, then monotherapy
with Ca channel blockers or combination therapy may be
used.
Initial doses of B blockers should be at the lower end of the
usual dosing range and titrated to response.
There is little evidence to suggest superiority of any particular B
blocker..eg. propanolol
Adverse effects: hypotension, bradycardia, bronchospasm….
Tapering of therapy over 2 days if it is to be discontinued to
minimize withdrawal reactions.
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B) Nitrates:
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Ishemic heart disease
Action of nitrates: indirectly, through reduction of myocardial
O2 demand 2ry to venodilation and directly, through dilation of
coronary arteries and relief of spasm.
Used to terminate an acute anginal attacks, prevent
effort/stress induced attacks or for prophylaxis.
Pharmacokinetic charecteristics : short half lives. eg.
Nitroglycerin:1-5 min (exception isosorbide mononitrate half life 5
hours).First-pass effect of hepatic metabolism.
Different dosage forms include: sublingual, buccal, spray,
chewable and transdermal products.
Adverse effects: postural hypotension, reflex tachycardia,
headaches.
A daily nitrate-free interval of 8-12 hours is necessary to
prevent nitrate tolerance which is of quick onset and offset.
Combination therapy is used in pts with more frequent
symptoms ,or if B blockers / Ca channel blockers are ineffective
or not tolerated.
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C) Ca Channel blockers:
Ishemic heart disease
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Actions: - vasodilation of systemic arterioles & coronary arteries.
- depression of myocardial contractility and conduction
velocity of AV and SV nodes.
- decrease MVo2
- improve coronary blood flow in areas of obstruction.
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Eg. Verapamil and deltiazem, which cause less peripheral
vasodilation than nifidepines but greater decreases in AV node
conduction.
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Ideal candidates for Ca channel blockers include patients with
contraindications or intolerance to B blockers, coexisting
conduction system disease (excluding verapamil), severe
ventricular dysfunction (best Amlodipine)
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Ishemic heart disease
Treatment of stable exertional
angina pectoris:
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Regular exercise program should be undertaken improve C &
M fitness.
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Nitrate therapy should be the first step in managing acute
attacks of chronic stable angina if episodes are infrequent.
(sublingual nitroglycerin tablets or sprays or buccal products)
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For prophylaxis when undertaking activities that lead to attacks,
nitroglycerin sublingually or spray may be used.
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If angina occurs more frequently than once a day, chronic
prophylactic therapy should be instituted. B adrenergic
blocking agents are preferred esp. in patients with a fixed
anginal threshold
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Ishemic heart disease
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Ca channel antagonists can be used instead of B blockers for
chronic prophylactic therapy . They are used in: patients with a
variable threshold for exertional angina and pts with
contraindications to B blockers.
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Verapamil not used in pts with conduction abnormalities and LV
dysfunction, whereas amlodipine may be used.
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Deltiazem not be used in pts with pre-existing conduction disease or
with other drugs with negative chronotropic effect.
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Nifidepine may cause excessive heart rate elevation and is best
combined with B blocker.
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Chronic prophylactic therapy with long-acting forms of
nitroglycerin may also be effective if angina occurs more than once
daily. Monotherapy with nitrates should not be first line therapy
unless B blockers and Ca channel blockers are contraindicated or
not tolerated.
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Chest pain
-probability of coronary
artery disease
-high risk CAD unlikely
Anti-anginal
Drug treatment
Education and risk factor
Ishemic heart disease
modification
Initiate educational
program
Sublingual NTG
History suggests vasospastic
Angina?
yes
Side
effect
Or CI
Aspirin if no
contraindication
Ca channel blocker,
Long acting nitrate therapy
Clopidogrel
yes
no
Medications or conditions
That provoke angina
Treat
yes
appropriately
yes
Cigarette
smoking
Successful
treatment
yes
Smoking
Cessation
program
no
no
B-blocker therapy
If no contradiction
Yes
Successful
treatment
Cholesterol
high
yes
Add long acting
Nitrate therapy
If no CI
yes
Successful
treatment
yes
no
Serious Cont Ind
Successful
teatment
see NCEP
guidelines
Blood Pressure
yes
high
See JNC-VI
guidelines
no
Serious Cont Ind
no
Add or substitute Ca channel yes
Blocker if no Contraindication
yes
no
Consider
Revascularization
therapy
Routine follow up including
Diet, exercise program,
Diabetes management
= treatment
yes
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Ishemic heart disease
Treatment of unstable angina pectoris &
NSTEMI:
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Immediate management involves risk stratification (Histroy, PhE, ECG,
Biomarkers) to assign pts into one of the following categories (1) noncardiac
diagnosis (2) chronic stable angina (3) possible ACS (4) definite ACS
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Anti-ischemic therapy for unstable angina includes:
- bed rest with continuous monitoring for ischemia and arrhythmia
- supplemental oxygen if cyanotic
- immediate sublingual nitroglycerin followed by IV nitroglycerin
- aspirin , heparin
- IV B blockers followed by oral B blockers
- if pain not relieved by nitrates: morphine sulphate IV.
-ACE I should be given if hypertension or LV dysfunction persists after
nitroglycerin and B blockers
- long acting Ca channel blocker may be added if necessary or
substituted for B blockers, if B blockers are contraindicated.
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Ishemic heart disease
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Antithrombotic therapy is used based on the likelihood of ACS:
- patients with possible ACS should receive only aspirin
- patients with definite ACS should be treated initially with non-enteric
coated aspirin followed by enteric coated aspirin and subcutaneous
low molecular weight heparin (LMWH) (eg. Enoxaparin) or IV
unfractionated heparin (UFH)
- patients with definite ACS with continuing ischemia, other high risk
factors or planned percutaneous coronary intervention (PCI) should
receive aspirin plus LMWH or UFH and an IV platelet glycoprotein
IIb/IIIa receptor antagonist ( eg. Abciximab)
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Patients intolerant to aspirin may receive clopidogrel, or ticlopidine.
If PCI is planned , aspirin plus clopidogrel is used.
Coronary angiography can be considered in certain cases.
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Treatment of coronary artery spasm and
variant angina pectoris:
Ishemic heart disease
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Nitrates are the mainstay of therapy, mainly sublingual nitroglycerin or
ISDN. IV nitroglycerin may be useful if patient not responding to
sublingual preps.
Calcium channel blockers may be considered as agents of choice
because they are more effective, have fewer side effects, and can be
given less frequently than nitrates.
Combination therapy may be useful in unresponsive pts (nitrates+ Ca
channel blockers)
B blockers have no role as they may induce coronary vasospasm.
Evaluation of therapeutic outcomes:
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Subjective and objective measures of drug response.
Monitoring for major adverse effects should be undertaken.
ECG, ETT can be used to evaluate response to therapy.
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Certain laboratory tests can be useful.
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