Acute Myocardial Ischemia Without Necrosis

Introduction

Acute myocardial ischemia without necrosis is a clinical condition characterized by an insufficient oxygen supply to the myocardium without the cellular necrosis typical of myocardial infarction. It is a transient and reversible condition but can be an early warning sign of major cardiovascular events if not properly managed.

This form of ischemia often presents as unstable angina or with electrocardiographic changes suggestive of ischemia, without the release of cardiac biomarkers indicative of myocardial damage.

Pathophysiology

Myocardial ischemia occurs when the balance between myocardial oxygen demand and supply is disrupted. The main mechanisms involved include:

• Reduced oxygen supply: critical coronary stenosis, coronary spasm, or altered microcirculation.
• Increased myocardial demand: tachycardia, hypertension, or left ventricular hypertrophy.
• Autonomic imbalance: endothelial dysfunction and reduced coronary reserve.

Causes

Acute myocardial ischemia without necrosis can result from multiple factors:

• Atherosclerotic coronary disease: critical stenosis reducing blood flow.
• Coronary spasm (Prinzmetal's angina): transient vasoconstriction reducing oxygen supply.
• Coronary microvascular dysfunction: impaired microcirculation affecting perfusion.
• Metabolic stress conditions: anemia, hypoxia, or hyperthyroidism.
• Tachyarrhythmias: atrial fibrillation or non-sustained ventricular tachycardia.

Clinical Presentation

Patients may exhibit symptoms similar to myocardial infarction but without necrosis:

• Oppressive chest pain, often occurring at rest or triggered by stress.
• Dyspnea, related to transient ventricular dysfunction.
• Pallor and profuse sweating in more severe cases.
• Feeling of instability or near-syncope due to cerebral hypoperfusion.

Diagnosis

The diagnosis of myocardial ischemia without necrosis is based on:

1. Electrocardiogram (ECG)

   It may show transient ST-segment depression or T-wave inversion, without evidence of myocardial necrosis.

2. Cardiac biomarkers

   Troponins remain normal, differentiating this condition from myocardial infarction.

3. Imaging tests

   Stress echocardiography or myocardial scintigraphy may reveal perfusion abnormalities.

4. Coronary angiography

   Indicated in high-risk patients to assess significant stenosis or microvascular dysfunction.

Treatment

The management of myocardial ischemia without necrosis aims to prevent progression to myocardial infarction:

1. Pharmacological Therapy

• Antiplatelet agents: aspirin and clopidogrel to prevent thrombosis.
• Beta-blockers: reduce myocardial oxygen consumption.
• Nitrates: improve coronary blood flow and relieve symptoms.
• Calcium channel blockers: indicated for patients with coronary spasm.

2. Invasive Strategies

For high-risk patients, coronary angiography is recommended to evaluate the need for coronary angioplasty.

Complications

If untreated, acute myocardial ischemia without necrosis may progress to:

• Acute myocardial infarction, with documented necrosis.
• Transient ventricular dysfunction, increasing the risk of heart failure.
• Malignant arrhythmias, such as ventricular fibrillation or sustained ventricular tachycardia.

Prognosis

The prognosis depends on the underlying cause and the promptness of therapy. Patients with untreated critical coronary stenosis have a higher risk of future ischemic events. Secondary prevention, including risk factor modification and pharmacological therapy, is essential to improve long-term outcomes.

Bibliografia
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