Article X - Management of Heart Attack

The immediate management of heart attack called acute myocardial infarction, entails accurate and prompt diagnosis of heart attack based on history, ECG and blood test for release of cardiac enzymes. For monitoring and definitive treatment, quick assessment and early referral to a coronary care unit (CCU) is required. Management includes general measure and drugs – pharmacotherapy. Effort has been made to describe various strategies and drugs under the headings of rationale and evidence, indications, protocol and dosage and precaution.

MOBILITY:

Patient is confined to bed for the first 24 hours being monitored in CCU. Patients with persistent chest pain, irregular beating of heart called arrhythmias or heart failure are immobilized for longer duration. In uncomplicated heart attack gradual mobilization according to a set protocol should be followed.

OXYGEN:
Rationale and Evidence
Increased oxygen concentration is helpful at the time of heart attack to protect jeopardized heart muscle. It is helpful in reducing ventilation and perfusion mismatch. Administration of 100% oxygen has been shown to reduce ECG changes and have some effect on reduction of heart attack severity and size in animal and human models.

Who should get it?
Supplemental oxygen to all patients with overt breathlessness and those who have low oxygen saturation. Routinely it may be administered to all the patients with uncomplicated heart attack during the first 2-3 hours. There is no convincing evidence of any significant benefit in uncomplicated heart attack beyond 3 hours. Oxygen may be administered by nasal prongs or mask. The rate may be adjusted in arterial desaturation guided by repeat estimation. Nasal prongs may cause nasal irritation and mask may cause claustrophobia.

PAIN KILLERS
Rationale and Evidence:
Heart attack pain is very severe and capricious accompanied with impending feeling of death. Pain increased sympathetic activity hence increasing oxygen metabolic demand. This has to be relieved in shortest possible time with effective analgesics in appropriate dosage through proper route and repeated at proper intervals.

Who should get it?
Every patient with severe chest pain with ECG evidence should receive adequate analgesics. Those patients presenting after pain resolution may not be candidates for analgesics.

Precaution:
Morphine and analogues may depress breathing and extra caution must be exercised in old patients and those with chronic chest problems. Morphine and analogues cause vomiting, so anti-emetics should be given prophylactically.

CLOT DISSOLVING TREATMENT (Thrombolytic therapy):
Rationale and Evidence:
Last decade has been the decade of clot dissolving drugs called Thrombolytics. Convincing evidence from many large trials involving large patient population has secured a steady place for Thrombolytic therapy in the management of heart attack. This has revolutionized the management of acute heart attack. There has to be a solid reason for withholding Thrombolytic therapy. Dewood studies showed that a clot is involved in hart attack in more than 85% of cases.

This aim is early, complete and sustained blood flow to heart muscle. Cloth dissolving strategy involving intracoronary and intravenous administration of various agents has eventually reached a state of consensus. Clot dissolving therapy to reperfuse reduces death rate by 21% in patients with heart attack that means saving 21 lives per 1000 patients. The effects are time dependent as evidence suggests maximal benefit within two hours, optimal within six hours though definite benefit lasts till 12 hours. An estimated 35 lives per 1000 are saved when initiated within one hour as against 16 lives per 1000 when given 7 – 12 hours after the onset of symptoms.

Who should get it?
Clot dissolving drugs benefit all patients irrespective of age, gender, and presences of other conditions like diabetes mellitus. All patient presenting with heart attack within six hours of onset of symptoms must be administered clot dissolving Thrombolytics. Patients presenting within 6-12 hours should be considered for Thrombolytics. Patients presenting with symptoms suggestive of heart attack with left bundle branch block an ECG finding, should be candidates for Thrombolysis. Patients presenting after 12 hours with persisting pain and ECG changes should be considered for reperfusion theraphy after weighing pros and cons. More aggressive approach is desirable in younger patients and those with large heart attacks. It is, however, the elderly who get more benefit from Thrombolytic therapy.
Concerted efforts should be made that maximum number of patients benefit from this therapy. Initial evaluation in casualty department and CCU should be prompt and should not take more than twenty minutes in total. Consolidated data shows that 1.6 lives can be saved per hour per 1000 patients. Time is muscle, and every effort should be made to administer Thrombolytics as soon as possible.

Precautions:
Patients with contraindications to clot dissolving thrombolytics, like active internal bleeding, history of stroke, brain tumour, suspected aortic dissection, prolonged resuscitation, proliferative retinopathy, acute pancreatitis, fixed accelerated high blood pressure and bleeding disorders should not be given Thrombolytics. Streptokinase should not be used after 7 days and before 6 months of first administration due to the presence of antibodies.

ANGIOPLASTY:
Rationale and Evidence:
Coronary angioplasty provides the distinct advantage of not only opening the occluded artery by taking care of the superimposed clot but also dilating the primary lesion. The success rate of opening the infarct related artery is 95%. With the employment of stents the results are getting better. Infarct related artery has to be opened quickly, with lower rates of acute and subacute occlusion and restenosis. A pioneer study showed higher patency rates of coronary artery with reduced morbidity and mortality rates. It can be employed as the first and only procedure called primary angioplasty. In case of failure of clot dissolving treatment it is used as a rescue procedure called rescue angioplasty. Primary angioplasty should be performed by skilled operators backed by experienced personnel.

Who should get it:
The evidence from different trials support better outcome in terms of morbidity and mortality with anagioplasty as compared to thrombolytics. This mode of reperfusion is preferable wherever the facilities and expertise are available. It is the treatment of choice for patients presenting with low blood pressure called cardiogenic shock associated with large infarcts. It is of great importance for patients who cannot receive clot dissolving thrombolytic therapy. Patients who have received thrombolytic therapy in the last six months or who are allergic to it can derive benefit from angioplasty. Patients who fail to respond to thrombolytic therapy should be subjected to angioplasty.

The time taken from reporting to hospital to inflation of balloon in patients undergoing angioplasty should be comparable to the time taken in patients receiving clot dissolving drugs. This requires prompt assessment and management in the casualty department and CCU. Quick and in time referral to the Catheterization laboratory is mandatory. Round the clock availability of skilled operators and experienced staff and a well stocked Catheterization laboratory are very essential for the success of any programme. Cardiac surgical team should be available in case of emergency.

Precautions:
This mode of reperfusion involves high cost due to high cost of catheterization laboratory and hardware involved. It is subject to the availability of highly skilled and experienced operator and staff round the clock. Very few hospitals have such facilities so this can be offered to a very small segment of society.

ASPIRIN:
Rationale and Evidence:
Very few treatment modalities have been so well and widely received and practiced as aspirin in heart attack. Aspirin in does of 40 mg can reduce the aggregation property of platelets. In a summary of 33 trials, heart attack in patients on Aspirin was reduced from 25% to 11%. Many trials have shown remarkable beneficial effect.

Who should get it?
Every patient with no contra-indication to aspirin should be given aspirin as soon as possible. Administration of beta blocker, ACE inhibitors, reperfusion with thrombolytic therapy or primary PTCA, presence of hypotension, hypertension, bundle branch block, complete heart block, diabetes pose no contraindication to aspirin.

Every patient with suspicion of heart attack should be given aspirin 300 mg to chew as soon as possible and continued indefinitely in dosage of 75 mg per day. Various enteric coded brands are available in the market to reduce hyperacidity.

Precautions:
Patients with proven ulcer on endoscopy or barium meal, history of gastic bleeding or those receiving antiulcer treatment should not be given aspirin. Patients with known allergy should not be given aspirin. Other platelet inhibitors may be considered in patients who have allergy or who cannot tolerate aspirin.
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VESSEL DILATOR – NITRATE:
Rationale and Evidence:

Nitrates have muscle relaxation effect hence causing dilation of all vessels. This causes reduction in load on heart hence reducing oxygen demand. Intravenous therapy has been shown in animal and human models to reduce infarct size.

Who should get it?
Patients presenting, with heart attack in the first 24-48 hours, specially in large anterior heart attack, persistent chest pain and high blood pressure. It may be continued beyond 48 hours in patients with persistent chest pain or recurrent angina and breathlessness. Routine use after 24-48 hours is not recommended.

Nitroglycerine or Nitrate infusion is started and titrated while monitoring heart rate and blood pressure. Blood pressure reduction by 10% or heart rate increase by 10% should warrant reduction in dosage and closer monitoring. Long term oral therapy has not been found to have any significant effect on morbidity and mortality.

Precautions:
Patients presenting with blood pressure less than 90 mmHg, or slow heart rate should not be given Nitrate infusion. Lowering of blood pressure and increase in heart rate should be closely monitored.

BETA BLOCKERS:
Rationale and Evidence:
Beta blockers reduce heart rate and contractility hence decreasing oxygen demand. This has been shown to reduce heart attack size in animal and human models. Beta blockers decrease fatty acids. They have a well established role in ischaemia – reduce blood supply, arrhythmia – irregular heart beating and high blood pressure. Large trial and meta analysis have shown impressive reduction of morbidity and mortality with oral and intravenous beta blockers.

Who should get it?
Every patient regardless of age, gender, reperfusion strategy and therapy, time period, type of heart attack, associated comorbid condition should get it. It is of particular importance in patients with recurring chest pains, fast heart rate and high blood pressure.
Evolving heart attack should be given intravenous beta blocker watching blood pressure and heart rate closely. Oral therapy in appropriate dosage should be instituted at the earliest and continued preferably for two years. Perhaps all beta blockers in proper dosage confer similar effects. Beta blockers with longer half life have the advantage of convenience of dosage and lesser side effects.

Precautions:
Patients with asthma, chronic chest problems, low blood pressure – hypotension, overt heart failure, slow heart rate, uncontrolled or brittle diabetes should not be given beta blockers. Mild heart failure may be challenged with beta blockers under close supervision. Controlled diabetes is not a contraindication to beta blockers as the benefits outweigh the hazards.

ACE INHIBITORS:
Rationale and Evidence:
Dead – infracted segments stop contracting following a heart attack, other segments become hyperactive to maintain heart function. Heart undergoes remodeling in which it enlarges in size with increased wall tension on non infracted segments. Studies have shown that higher volumes are associated with higher chances of heart failure and increased morbidity and mortality. ACE inhibitors (ACEI) have been shown to reduce load on heart hence reducing wall tension and help is not increasing heart volumes. Use of ACE inhibitors in patients with symptoms of heart failure or evidence of reduced function derive maximal benefit with significant reduction of mortality and morbidity as shown in many large well conducted trials.

Who should get it?
All patients without contra indications to ACE inhibitors should be considered for it. It is particularly helpful in patients with symptoms and signs suggestive of heart failure or who have evidence of heart dysfunction – large dimensions and poor contraction even in absence of symptoms.

ACE inhibitors should be started with small dosage to obviate any low blood pressure episodes. The dose has to be built up gradually if patient can tolerate it. Systolic blood pressure should be mentioned closely. Optimal effects can only be expected at appropriate dosage Determined efforts should be made to optimize the dosage during hospitalization.

Precautions:
Patients with systolic blood pressure less than 90 mmHg should not be given ACEI. Those showing marked decrease in blood pressure, ACEI should be withheld and restarted at small dosage after some time. Those having persistent cough or intolerance to ACEI may be considered for Angiotensin receptor blockers like Losartan, Valsartan, Candesartan etc.

ANTI COAGUTANT – HEPARIN:
Rationale and Evidence:
Clot dissolving Drugs can open up the infarct related artery but for sustained patency Heparin had been advocated for a long time. Recent evidence from a large trial analysis does not support the regular use of Heparin following Streptokinase unless patient is at high risk for clot formation and dislodgement. Those patients who do not receive Thrombolytics may derive some benefit from Heparin. In the setting of unstable angina, intravenous Heparin has been shown to reduce morbidity and mortalilty.

Who should get it?
Patients presenting with unstable angina should get Heparin. Patients presenting late for thrombolytics should be considered for Heparin. In patients at high risk for clot formation and dislodgement like large or anterior infarction, irregular heart beat, or left ventricular clot, intravenous Heparin is preferred. Intravenous (IV) Heparin in patients receiving selective thrombolytics like tpa or alteplase is recommended.

Precaution:
Strick regimen should be followed as under dosage leads to treatment failure and overdosage causes bleeding complications.

FURTHER MANAGEMENT
This depends on the further course of disease. Uncomplicated heart attack patients are mobilized and discharged on 4th to 7th days of admission. An exit exercise tolerance test is favoured by some groups to identify patients at high risk requiring early angiography and intervention. Any mechanical, electrical or ischaemic complication is dealt with according to its merit.

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Ref: Heal Thy Heart written by Prof: Dr. Muhammad Hafizullah