Lecture on treatment of myocardial ischemia

2021-08-06 10:02 PM

Myocardial ischemia is a multifactorial condition that shares an imbalance between myocardial oxygen supply and demand, which is a manifestation of a temporary or prolonged decrease in oxygenation

Define

Myocardial ischemia is a multifactorial condition that shares an imbalance between myocardial oxygen supply and demand, which is a manifestation of a temporary or prolonged decrease in oxygenation, relative or absolute. chemistry of the heart.

Cause

Coronary artery disease

Coronary atherosclerosis: accounts for the majority of cases of myocardial ischemia.

Coronary artery embolism.

Coronary artery spasm.

Dissecting aortic aneurysm.

Takayasu aortic inflammation.

Congenital coronary artery malformation: coronary artery fistula.

Heart valve and myocardial disease

Aortic valve stenosis.

Severe regurgitation of the aortic valve.

Hypertrophic cardiomyopathy.

Factors that increase myocardial oxygen demand

Heart palpitations increased myocardial contractility.

Auxiliary elements

Anemia.

Hypotension.

Risk factors for coronary artery disease

Family history of premature coronary artery disease

Smoking

Increased blood cholesterol.

Hypertension.

Diabetes.

Fat.

Less physical activity.

If these risks are avoided, it will slow or regress the process of coronary atherosclerosis.

Cause

Treatment of stable angina

Treatment of coronary atherosclerosis risk factors.

Treat predisposing factors.

Drug treatment.

Nitrate:

Mechanism of action:

The main effect is vasodilatation => increased venous blood capacity => decreased volume and diastolic pressure in the ventricular chambers => improved myocardial perfusion.

Secondary mechanism: is arterial dilation:

Improves coronary collateral circulation

Reduced afterload pressure => reduced myocardial contractility => less oxygen consumption and easier perfusion.

Short-acting nitrates:

Nitroglycerine tablets 0.3mg 0.4mg 0.6mg.

Isosorbide dinitrate 5mg.

Nitroglycerine aerosol 0.4mg/dose (2 sprays).

Only used to treat pain, the time begins to work after 2 minutes and lasts 20-30 minutes, can be repeated with an interval of 5 minutes if the pain has not gone.

Long-acting nitrates:

Oral nitrates are mostly broken down in the liver => use higher doses.

It is recommended to use drugs that leave time for Nitrate emptying so that the body can recover SH radicals to create NO => avoid nitrate tolerance (tolerance) or replace it with Molsidomine that provides NO radicals directly.

Isosorbide mononitrate should be used in people with cirrhosis because it is less metabolized in the liver.

Amount: 

ISDN 10 - 40mg x 2 - 3 times/day.

Isosorbide 5 mononitrate (Imdur 30; 60mg) orally once a day at a dose of 30-60mg

Transdermal Nitroglycerine 5 -15 mg once daily for 12 hours.

Nitrate side effects: headache, mild hypotension.

Beta-Blocker:

Mechanism of action:

Decreased myocardial contractility ® reduces myocardial oxygen consumption.

Prolongs diastolic time ® increases myocardial perfusion.

Choice of drugs:

Should use selective beta 1 blocker (Metoprolol, Atenolol) => fewer side effects causing aggravation of peripheral vascular disease and bronchospasm.

If the heart rate is slightly bradycardia, a beta-blocker with sympathomimetic activity (ISA (+)) such as pindolol, acebutolol should be used.

It is recommended to start with a low dose and gradually increase until the target is reached:

Heart rate at rest # 50 - 60 beats/min

During exercise, heart rate < 100 beats/min

For example: Propranolol 10mg x 2 times/day => 20-80mg x 2 times/day

Metoprolol 12.5 mg x 2 times/day => 50-100mg x 2 times/day

Main contraindications:

Heart failure.

Atrioventricular block.

Obstructive lung disease.

The bradycardia is evident at rest.

Severe peripheral vascular disease.

Calcium Inhibitors:

Cardizem:

Function:

Decreased myocardial contractility.

Reduces heart rate and slows atrioventricular conduction.

Dilation of arteries > veins should lower blood pressure => reduce the work of the heart and reduce left ventricular systolic pressure.

Dosage: 120 - 360 mg/day divided into 1-3 times depending on the long- or short-acting product.

Contraindications:

Severe heart failure.

Hypotension.

Slow heart rate.

Verapamil:

Effects: Similar to Cardiazem but stronger in reducing heart rate, atrioventricular block.

Dosage: 120 - 480mg / day divided 1-3 times depending on the preparation.

Contraindications:

Severe heart failure.

Hypotension.

Slow heart rate.

Nifedipine:

The drug has a direct vasodilator effect, without affecting atrioventricular conduction and myocardial contractility.

Side effects: increased heart rate is detrimental to myocardial perfusion, so it is only used in cases of myocardial ischemia with high blood pressure. Should be combined with beta-blockers to reduce heart rate

Dosage: 30 - 60mg/day divided 1 - 3 times depending on the preparation.

Ex: Nifedipine retard 10 - 20mg x 2 or 3 times/day.

Adalate LA 30 mg once a day only 1 tablet.

Anti-platelet adhesion:

Long-term use of low-dose aspirin 80-160 mg/day can be used.

If the patient has peptic ulcer, use Ticlopidine 250 x 2 times/day or Clopidogrel 75mg (Plavix, Deplatt, infartan) x 1 time/day

Treatment of trauma:

With the aim of re-establishing myocardial blood flow, there are many methods currently applied.

Bypass surgery (CABG).

Angioplasty (PTCA).

Endoscopic resection of atheroma.

Coronary artery drilling

Treatment of angina pectoris

The use of nitrates and calcium channel blockers should not be used with beta-blockers.

Treatment of unstable angina/non-ST-elevation myocardial infarction

Rule:

Hospitalization to coronary care unit, bed rest, sedation, treatment of predisposing factors such as high blood pressure, anemia, hypoxemia, etc. Treatment goals include symptom relief of anemia with antianginal and antithrombotic drugs.

Treatment of ischemia:

Should combine ³ 2 drug groups: nitrate, beta-blocker, calcium channel blocker if there are no contraindications.

Nitrate can also be administered intravenously.

Anticoagulation (see myocardial infarction with ST-elevation):

The use of Heparin reduces the incidence of myocardial infarction complications.

Using antiplatelets (Aspirine, clopidogrel ...) to reduce mortality and complications of myocardial infarction.

Pain relief:

Morphine may be used if other pain relievers are ineffective.

Prognosis:

With aggressive treatment under adequate conditions, there is about 10-20% leading to myocardial infarction.