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What to prescribe after a man has an MI

PillsA British National Formulary (BNF) case study presents prescribing issues that need consideration after a heart attack

 

A 59-year-old man is admitted to hospital — he has had severe, crushing chest pain for 90 minutes. His electrocardiogram shows a 3mm ST segment elevation in leads V1 to V4, consistent with an acute anterior myocardial infarction. He is given loading doses of aspirin and clopidogrel.

Forty-five minutes later, a primary percutaneous coronary intervention (PCI) is performed, with the insertion of a drug-eluting stent (sirolimus, paclitaxel or everolimus are often used in such stents) into the patient’s critically narrowed left anterior descending coronary artery.

By the time he is returned to the coronary care unit 30 minutes after the successful procedure, he is pain free and there is partial resolution of his ECG changes.

His urea, electrolytes, full blood count, blood glucose, and renal, hepatic and thyroid function are all normal.

His fasting lipid profile is as follows:

  • Cholesterol 6.8mmol/L (normal value <4mmol/L)
  • High-density lipoprotein cholesterol 1.2mmol/L (>1mmol/L)
  • Low-density lipoprotein cholesterol 4.0mmol/L (<2mmol/L)
  • Triglycerides 3.5mmol/L (<1.7mmol/L)

 

Although the patient has a history of asthma, it is well controlled and he has never been admitted to hospital for it and he rarely uses his salbutamol inhaler. He also has a history of gastro-oesophageal reflux — oesophagitis was confirmed by endoscopy two years ago.

He smokes 20 cigarettes a day and consumes about 35 units of alcohol each week. His body mass index is 26kg/m2. His father died of a myocardial infarction at 62 years of age, but there is no other adverse family history.

The patient is to continue with the medicines he was using before his admission; Flixotide Evohaler 100mg bd, salbutamol inhaler 200mg prn and omeprazole 20mg od. In addition, he is prescribed:

  • Aspirin 75mg od
  • Clopidogrel 75mg od
  • Atorvastatin 80mg on

 

An intravenous infusion of abciximab is to continue for 12 hours. The patient will also be risk assessed for venous thromboembolism.

Key points

Angiotensin-converting enzyme inhibitors help to reduce mortality after ST segment elevation myocardial infarction. The starting dose of lisinopril is influenced by the patient’s systolic blood pressure.

The aldosterone antagonist eplerenone can be used after ST segment elevation myocardial infarction in patients with left ventricular dysfunction and evidence of heart failure (note that risk of hyperkalaemia is increased with ACE inhibitors).

Early use of beta-blockers reduces mortality and recurrence of heart attack but should usually be avoided in patients with a history of asthma. If it is necessary for a patient with well controlled asthma to receive a beta-blocker, a cardioselective drug (eg, bisoprolol) may be started at a low dose by a specialist and the patient monitored.

Clopidogrel should be used for 12 months after percutaneous coronary intervention with a drug eluting stent but patients at high risk of late stent thrombosis might require longer treatment.

Omeprazole can reduce the antiplatelet effect of clopidogrel.

Six hours after the PCI, the patient becomes breathless and a chest X-ray reveals pulmonary oedema. Echocardiography shows hypokinesis of the interventricular septum and apex. The left ventricular ejection fraction is 32 per cent, indicating heart failure. He is given furosemide 40mg by slow intravenous injection. His blood pressure is 115/85mmHg and his heart rate is 95bpm.

Angiotensin-converting enzyme inhibitors help to reduce mortality after ST segment elevation myocardial infarction. When can an ACE inhibitor be started in this patient?

The prescribing notes on management of ST segment elevation myocardial infarction (section 2.10.1, BNF 61) advise that, in the absence of contraindications and hypotension, an angiotensin-converting enzyme inhibitor can be started within 24 hours of a heart attack and continued for at least five weeks.

Longer-term treatment with an ACE inhibitor will be particularly beneficial in this patient with evidence of heart failure.

Lisinopril is prescribed. What is the dosage regimen?

According to the lisinopril monograph in BNF 61, when systolic blood pressure is 100–120mmHg the drug should be initiated at 2.5mg once daily.

A relatively high dose of ACE inhibitor is required to produce prognostic benefit (both post myocardial infarction and in heart failure) so, if tolerated, the dose of lisinopril should be increased to 5mg once daily and then increased in steps of no greater than 10mg at intervals of at least two weeks, to a maximum of 35mg daily. Blood pressure, renal function, and electrolytes should be monitored during treatment.

Should this patient be given eplerenone (Inspra)?

According to the eplerenone monograph in BNF 61, the drug can be used within three to 14 days after a heart attack in patients with left ventricular dysfunction and evidence of heart failure. However, appendix 1 warns of an increased risk of severe hyperkalaemia when eplerenone is given with an ACE inhibitor.

The patient’s plasma-potassium concentration should be monitored during treatment and at dose changes, and he should be advised about a low-potassium diet.

 

After starting lisinopril and eplerenone, the patient is stable and no longer complaining of breathlessness.

Should he also receive a beta-blocker or a calcium-channel blocker?

Following an ST segment elevation myocardial infarction, early administration of a beta-blocker reduces mortality and the recurrence rate of myocardial infarction, and should be given to patients without contraindications.

Bisoprolol and carvedilol reduce mortality in any grade of stable heart failure. However, according to the prescribing notes on beta-adrenoceptor blocking drugs (section 2.4, BNF 61), beta-blockers can cause bronchospasm and should, therefore, usually be avoided in patients with a history of asthma.

When there is no suitable alternative, it may be necessary for a patient with well controlled asthma to receive treatment with a beta-blocker for a coexisting condition (eg, heart failure or following myocardial infarction).

In this situation, a cardioselective beta-blocker should be chosen (ie, bisoprolol rather than carvedilol) and initiated at a low dose by a specialist; the patient should be monitored closely for adverse effects.

The prescribing notes on management of ST segment elevation myocardial infarction also advise that diltiazem or verapamil can be considered if a beta-blocker cannot be used, but each drug is contraindicated in this patient because of his left ventricular dysfunction. Other calcium channel blockers have no place in routine long-term management after a myocardial infarction.

In this patient with stable heart failure as well as well controlled mild asthma, the bisoprolol should be started by a specialist.

How should bisoprolol be initiated in this patient?

According to the prescribing notes on heart failure (section 2.5.5, BNF 61), bisoprolol should be started at a very low dose and titrated slowly (over weeks or months). Symptoms can deteriorate initially, calling for adjustment of concomitant therapy.

The patient’s heart rate, blood pressure, respiratory function and clinical status should be monitored frequently during treatment and after each dose titration (full details of the dosage regimen can be found in the drug monograph). In particular, he should be asked to report any need to use his salbutamol inhaler more than twice a week, and any increasing breathlessness, cough or chest tightness.

How long should aspirin and clopidogrel be continued?

According to the prescribing notes on antiplatelet drugs (section 2.9,
BNF 61), low-dose aspirin should be continued indefinitely after PCI involving the placement of a coronary stent.

Clopidogrel is recommended for 12 months following the placement of a drug eluting stent. Clopidogrel should not be discontinued prematurely because there is an increased risk of stent thrombosis as a result of the eluted drug slowing the re-endothelialisation process.

Patients considered at high risk of developing late stent thrombosis with a drug eluting stent might require a longer duration of treatment with clopidogrel; in some cases therapy may need to be life-long.

Is it appropriate for the patient to continue to take omeprazole for his gastro-oesophageal reflux disease?

According to Appendix 1, BNF 61, the antiplatelet effect of clopidogrel is reduced by omeprazole and this is classified as a serious drug interaction but recent studies have questioned the clinical importance of this effect. A similar drug interaction also occurs between esomeprazole and clopidogrel.

The antiplatelet effect of clopidogrel might possibly be reduced by lansoprazole, pantoprazole or rabeprazole. If it is essential, however, to continue a proton pump inhibitor, any of these three drugs should be used in preference to omeprazole. Alternatively, an H2 receptor antagonist (but not cimetidine, which also interacts with clopidogrel) can be used.

What risk factors does this patient have for statin related myopathy?

According to the prescribing notes on statins (section 2.12, BNF 61), the patient is at increased risk of myopathy because he is receiving high-dose atorvastatin and he has a high intake of alcohol.

The patient should be advised to report any unexplained muscle pain and to reduce his alcohol intake. (Department of Health recommendations for men are no more than 21 units a week and that they should not regularly drink more than four units a day.)

He should also be advised to modify his lifestyle to reduce his cardiovascular risk, which would include changes to diet, exercise and weight management. He should be encouraged to stop smoking and given access to smoking cessation products and services. His dose of atorvastatin should be reviewed after six to 12 weeks.

Details

Based on a case study from the BNF/BNFC e-newsletter, September 2010

Citation: The Pharmaceutical Journal URI: 11072225

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