Unstable Angina

Unstable angina is regarded as an extremely dangerous stage of exacerbation of coronary heart disease, threatening the development of myocardial infarction or sudden death. In terms of clinical manifestations and prognostic value, unstable angina takes an intermediate place between stable angina and acute myocardial infarction, but, unlike a heart attack, the degree and duration of ischemia are not sufficient for the development of myocardial necrosis in unstable angina.

What causes unstable angina?

It happens so that myocardial infarction develops suddenly, without any precursors. But more often within a few days or even weeks, patients experience symptoms that can be regarded as signs of the onset or exacerbation of coronary insufficiency. This may be a change in the nature of existing angina, that is, attacks can increase, increase, change or expand the area of irradiation, occur with less stress. Night attacks or episodes of arrhythmia can join.

The development of unstable angina is usually associated with a rupture of an atherosclerotic plaque and subsequent intracoronary thrombus formation. In some cases, the cause is an increase in the tone of the coronary arteries or their spasm.

Sometimes the pre-infakt period is characterized by symptoms of type of fatigability or general weakness, which are relatively nonspecific for coronary insufficiency. It is more than difficult to interpret such signs, unless they are accompanied by electrocardiographic changes in myocardial ischemia.

How does unstable angina manifest?

Unstable angina include:

• first-time angina pectoris (within 28-30 days from the moment of the first painful attack);
• progressive angina (conditionally - during the first 4 weeks). Painful attacks occur more often, become more severe, reduce tolerance to stress, appear angina attacks at rest, reduce the effectiveness of previously used antianginal drugs, increases the daily need for nitroglycerin;
• early post-infarction angina pectoris (within 2 weeks from the development of myocardial infarction);
• spontaneous angina pectoris (the appearance of severe painful attacks at rest, often lasting more than 15–20 minutes and accompanied by sweating, a sense of lack of air, rhythm disturbances and conduction, decreased blood pressure).

For the first time, angina does not require additional definition. Progressive angina refers to a sudden worsening of the clinical course of angina pectoris: the onset of stress angina attacks with a lighter load, an increase in their duration, the onset of rest angina pectoris, and the appearance of ECG changes that persist after stopping angina pectoris. With progressive angina, seizures often last more than 20 minutes, occur at night, additional symptoms appear: fear, sweat, nausea, palpitations).

Angina, which appears in the early period after myocardial infarction (ranging from 2 weeks to 1 month from the onset of myocardial infarction) or after coronary artery bypass surgery, is isolated as a separate variant.

The guidelines for the diagnosis and treatment of unstable angina, developed in the United States (1994), proposed to distinguish the following clinical options for unstable angina:

1. Quiescent angina (usually attacks lasting longer than 20 min;
2. For the first time the arising angina of exertion (not less than the III functional class);
3. Progressive angina is an increase in the severity of angina from grade 1 to grade III or IV.

The classification of unstable angina, proposed by J. Braunwald (1989) is well known:

Degree of risk	Option
I - severe exertional angina (first arisen or progressive)	A - secondary
II - subacute rest angina (remission in the last 48 hours)	B - primary
III - acute angina pectoris (seizures in the last 48 hours)	C - after myocardial infarction

The secondary unstable angina include cases where the cause of instability is non-cardiac factors (anemia, infection, stress, tachycardia, etc.)

With unstable angina, the risk of myocardial infarction sharply increases. The maximum likelihood of myocardial infarction is in the first 48 hours of unstable stenocardia (class III - acute unstable stenocardia of rest).

[1], [2], [3], [4], [5]

How is unstable angina detected?

Usually, with unstable angina on the electrocardiogram, there are no persistent ST segment elevations, there is no release of biomarkers of myocardial necrosis (cardiospecific enzymes) into the bloodstream. In some cases, with unstable angina, there are no changes at all indicating ischemia and myocardial damage. Adverse prognostic signs for unstable angina:

• ST-segment depression;
• short-term ST-segment elevation;
• inversion of teeth of T (polarity change).

An echocardiographic study in patients with unstable angina may be impaired mobility of the ischemic myocardial regions. The extent of these changes is directly dependent on the severity of the clinical manifestations of the disease.

ECG registration during seizures and in the interictal period is very important. Although the absence of ECG changes does not exclude the presence of ischemia, the risk of myocardial infarction in such patients is usually relatively small. On the other hand, the registration of any changes on the ECG and the preservation of ECG changes after the cessation of attacks indicates a high risk of myocardial infarction and complications. Most often in patients with unstable angina, ST segment depression or negative T teeth are observed. In some patients, unstable angina pectoris manifests itself in the form of spontaneous angina pectoris attacks with ST segment elevation. It should be noted that for the first time arising stenocardia can be stable (or “conditionally stable”) in clinical course, for example, for the first time arising angina pectoris of II FC.

[6], [7], [8], [9], [10], [11]