exactly 30 - Dynamics of heart contraction- the cardiac cycle. Opening and closing of the heart valves during the cardiac cycle. Function of the heart valves. Heart sounds. Methods of examination. Stenosis and insufficiency of valves. Correlation between a synchronous phonocardiographic and electrocardiographic record.

sections

Av valves

semilunar valves

valves of heart

heart sounds

phonocardiography

stenosis

Av valves (tricuspid and mitral)

• prevent backflow of blood from the ventricles to the atria during systole

• These valves close and open passively due to the pressure differences in front of and behind the valve

• Due the AV valves being relatively thin they close without the need of heavy backflow

semilunar valves

• prevent backflow from the aorta and pulmonary arteries into the ventricles during diastole

• the high pressures in the arteries at the end of systole cause the semilunar valves to snap to the closed position

• The much heavier semilunar valves require rather rapid backflow for a few milliseconds for closure.

• Due to the rapid closure and rapid ejection, the edges of the aortic and pulmonary valves are subjected to much greater mechanical abrasion than the A-V valves

• Constructed with an especially strong yet very pliable fibrous tissue base to withstand the extra physical stresses.

valves of heart

• aortic valve - right 2nd intercostal space parasternal

• Pulmonary valve - left 2nd interostal space parasternal

• Tricuspid - left 4th intercostal- parasternal

• Mitral - left 5th intercostal space midclavicular

heart sounds

• We can only hear valves closing

• 1st Lub = when the ventricles contract (QRS complex) we can hear the AV Valves closing.

• 2nd Dub = when semilunar valves (aortic and pulmonary ) at the end of systole BEST heard at ERB’S point

• Listening to heart sounds with the stethoscope is auscultation

phonocardiography

In Phonocardiography- The heart sounds can be amplified and recorded by a high-speed recording apparatus. The recording is called a phonocardiogram, and the heart sounds appear as waves and can be used to detect murmurs

stenosis

• stenosis- narrowing of a channel

• Aortic valve stenosis — occurs when the heart's aortic valve narrows.

• Decreased cardiac output

• does not close fully

• So valves do not open properly which reduces or blocks blood flow from your heart into the main artery to your body (aorta) and onward to the rest of your body.

• valve stenosis due to old age build up of calcium deposits on the aortic valve

• caused by rheumatic disease

sections

7 phases of cardiac cycle

times for atrial systole, diastole, isovolumetric relaxation, ventricular systole and diastole

PQRST

7 phases of cardiac cycle

1. Isovolumetric ventricular relaxation - as ventricles relax pressure in ventricles drop, blood flows back into cups of semilunar valves and snaps them close

2. late diastole - both sets of chambers relaxed. passive ventricular filling

3. Atrial systole - atrial contraction forces a small amount of additional blood into ventricles

4. EDV= end-diastolic volume - the maximum amount of blood in ventricles occurs at end of ventricular relaxation. EDV= 135 mL

5. Isovolumetric ventricular contraction - first phase of ventricular contraction pushes AV valves closed but does not create enough pressure to open semilunar valves

6. Ventricular ejection - as ventricular pressure rises and exceeds pressure in arteries, semilunar valves open and blood is ejected

7. ESV= end-systolic volume - or minimum amount of blood in ventricles. ESV = 65 mL

times for:

• atrial systole

• atrial diastole

• isovolumetric relaxation

• ventricular systole

• volumetric diastole

• Atrial systole- 0.1s

• Atrial diastole-0.7s

• Isovolumetric relaxation- 0.08s

• Ventricular systole- 0.3 s

• Ventricular diastole- 0.5 s

PQRST

1. P - wave = depolarisation of atria in response to SA node triggering

2. PR interval = delay of AV node to allow filling of ventricles

3. QRS complex = deploarisation of ventricles, triggers main pumping contractions

4. ST segments = beginning of ventricle replarisation should be flat

5. T wave = Ventricular repolarisation