12.02.1 Typical Angina

Angina pectoris means “choked chest”, which is a description of the symptoms in angina pectoris. Angina pectoris is a heavy, pressing, substernal discomfort with pain that often radiates to the left shoulder. Subjects with angina pectoris describe a feeling of suffocation and impending death. Angina pectoris is due to an imbalance between oxygen supply and oxygen demand due to coronary artery disease. Thus, the diseased coronary arteries are unable to supply enough oxygen to meet the demands of the heart. The coronary artery disease limits the blood supply. In coronary artery disease lipids including cholesterol contribute to the thickening of the artery walls, and with platelets and other blood components form plaques (Figure 12.2.1). The reduced lumen of the blood vessel reduces blood flow.

Figure 12.2.1 Coronary artery disease (Copyright QUT, Sheila Doggrell)

Angina pectoris is a progressive disease. In the initial stable phase, attacks of angina do no occur at rest, but occur with exercise and stress. Stable angina is associated with thickening, but not usually with plaque in the coronary arteries.

The mechanism underlying the attack of typical angina is that during stress or exercise, there is activation of the sympathetic nervous system with increased release of noradrenaline and increase stimulation of cardiac β₁-adrenoceptors (Figure 12.2.2). This stimulation leads to an increased heart rate, heart force, and, consequently, of the work done by the heart (Figure 12.2.2). To support this work, the heart has an increased demand for oxygen and nutrients, which are supplied by the coronary circulation (Figure 12.2.2). In stress or during exercise, the reduced blood flow in diseased coronary is inadequate to meet the oxygen and nutrient demand, and this gives an attack of angina.

Figure 12.2.2 Mechanism of typical angina (Copyright QUT, Sheila Doggrell)

Unstable typical angina is worsening of stable angina, so that angina attacks occur when the subject is at rest. Unstable angina is associated with thickening of the blood vessels and plaque formation in the coronary arteries. This is a very precarious position to be in, as plaque rupture with the subsequent blockade of smaller vessels leads to myocardial infarction (heart attack).

The drugs used to treat typical angina are divided into those used during an attack and those to prevent an attack of angina.