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Lecture 18. PHYSIOLOGY OF BLOOD CIRCULATION. METHODS OF INVESTIGATION OF CARDIAC ACTIVITY. CARDIAC CYCLE

Plan

► Classification of events accompanying cardiac activity: mechanical, sound and electrical events.

► Methods of investigation of mechanical events accompanying the work of heart.

► Methods of investigation of sound events accompanying the work of heart.

► Methods of investigation of electrical events accompanying the work of heart.

► Concept of cardiac cycle. Structure of cardiac cycle.

Classification of Events Accompanying Cardiac Activity

All events that accompany cardiac activity, can be classified into three groups: mechanical, sound and electrical.

Manifestations of Mechanical Events Accompanying Work of Heart and Methods of their Investigation

1. Apex beat (apical impulse). Apex beat is recorded in the 5th intercostal space 1-1.5 cm left to the midclavicular line. The beat is manifested by a vibration of soft tissues of the chest during mechanical systole of the heart. The apex beat may be visible in people with a thin subcutaneous tissue layer. In people having excessive body mass, the apex beat is poorly expressed. The intensity of the apex beat can be estimated by palpation and instrumental-ly - by a method of apex cardiography.

Apex cardiography uses a transducer (to convert mechanical vibrations of soft tissues to electrical signals), an amplifier, and a recorder. This method is rarely used in everyday medical practice.

2. Variation in the orientation of the heart and other chest organs in different phases of cardiac cycle. Until recently positions of organs were defined using an X-ray method with a preliminary introduction of contrast substances. Nowadays these methods are replaced by more modern and informative ones: ultrasound examination of the heart (echocardiography), computed tomography, nuclear-magnetic resonance. These methods require use of expensive specialized equipment.

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