Auscultation

The heart occupies a midline position in the thoracic cavity between the sternum anteriorly and the thoracic vertebrae posteriorly. The easiest landmark of the heart to locate is the lower left angle which is at the fifth left intercostal space in the midclavicular line. This also marks where the apex beat of the heart can be auscultated with a stethoscope. The sound generated at this position, is produced by the closure of the left atrioventricular valve as the left ventricle contracts. The apex beat is usually rendered as a ‘lub dub’.

Atrioventricular Valves

The following are some notes on the atrioventricular valves:

  • The base of these valves are attached to a fibrous ring which maintains the orifice patency of the valve

  • Chordae tendinae from the apices of the papillary muscles attach to its cusps

  • During ventricular systole, the papillary muscles contract which in turn tightens the tendinous cords and prevents the prolapse of the valves as ventricular pressure rises

Semilunar Valves

The following are some notes on the semilunar valves:

  • There are three semilunar valves

  • Their edges are thickened to form lunule, with a further thickened apex as a nodule

  • During systole they are pressed towards the arterial walls while during diastole they snap shut

Auscultation or listening to the internal sounds of the body, is done to examine heart beats at the following surface markings:

  1. Aortic valve - right second intercostal space at the sternal border

  2. Pulmonary valve - left second intercostal space at the sternal border

  3. Tricuspid valve - left fourth/fifth intercostal space at the sternal border

  4. Mitral valve - left fifth intercostal space at the midclavicular line. This is where you hear the heart apex beat.

 

Clinical Notes:

  1. Stenosis occurs when there is a narrowing and therefore the valve fails to open completely, this in turn slows blood flow.

  2. Incompetence occurs when a valve fails to close completely therefore producing regurgitation and compromising cardiac output.

  3. Prolapse occurs when the atrioventricular valve extends back into the atrium during systole and produces regurgitation of blood.

  4. A collapsing pulse may result from aortic valve insufficiencies.

  5. Audible heart murmurs can be heard if there is turbulence with the valves.

  6. Echocardiography allows visualization of blood flow.