CARDIAC CYCLE HEART SOUNDS Dr. AmelEassawi
HEART SOUNDS • There are four heart sounds SI, S2, S3 & S4. • Two heart sound are audible with stethoscope S1 & S2 (Lub - Dub). • Ventricular systole is between first and second Heart sound. • Ventricular diastole is between second and first heart sounds. • S3 & S4 are not audible with stethoscope Under normal conditions because they are low frequency sounds. • S3 may be heard in children and young adults but usually pathological in old age.
HEART SOUNDS Important: Heart sounds are caused by vibrations set within the wall of the ventricles and major arteries during valve closure . Opening of the valve does not cause sound.
HEART SOUNDS First heart sound (S1): • Produced due to the closure of Atrioventricular valves (Mitral & Tricuspid) • Occurs at the beginning of the systole and sounds like LUB. • Frequency:50-60 Hz. • Time: 0.15 sec. Second heart sound (S2): • Produced due to the closure of Semilunar valves (Aortic & Pulmonary). • Occurs at the end of the systole and sounds like DUB. • Frequency:80-90 Hz (High pitch). • Time: 0.12 sec. • It is short and sharp.
HEART SOUNDS • Third heart sound (S3): • Occurs at the beginning of middle third of diastole. • Due to rush of blood from Atria to Ventricle during rapid filling phase of Cardiac Cycle. It causes vibration in the blood. • Frequency:20-30 Htz. • Time: 0.1 sec. • Fourth heart sound (S4) or Atrial Sound: • Occurs at the last one third of diastole (just before S1). • Due to Atrial contraction which causes rapid flow of blood from Atria to noncompliant ventricle and vibration in the blood. • Frequency: < 20 Htz
HEART SOUNDS 1 st Heart Sound 2 nd Heart Sound 3 rd Heart Sound 4 th Heart Sound HEART SOUNDS
The heart has a broad base at the top behind the 2ndintercostal space. The Apex is at the bottom in the 5th left intercostal space, slightly below the nipple towards mid line
Heart Murmurs • Murmurs are abnormal sounds produced due to abnormal flow of blood (turbulent blood flow) through abnormal heart valves e.g stenosis or incompetence (insufficient). • Most common cause of stenosis and incompetent valve is Rheumatic fever, an auto immune disease triggered by Streptococcus bacterial infection. • Systolic murmur are produced during the systole of the ventricle, between 1st and 2nd heart sound (Lub – Murmur – Dup). • Diastolic murmur are produced during the diastole of the ventricle, between 2nd and 1st heart sound (Lub – Dup – Murmur – Lub).
Heart Murmurs Stenosis: Means narrow or stiff, valve that does not open completely. When blood is forced through stenotic valve, it produces an abnormal whistling sound. Incompetent: Means a valve which does not close properly and remains open. When blood flows backward through incompetent valve, it produces swishing or gurgling murmur sound (backflow of the blood is known as regurgitation) is also called leaky valve. During aortic stenosis and mitral incompetence – systolic murmur. Aortic incompetence and mitral Stenosis – diastolic murmur.
Events of cardiac cycle for Lt. ventricular function showing changes in Lt. atrial pressure, Lt. ventricular pressure, aortic pressure, ventricular volume, ECG & phonocardiogram
References • Human physiology, Lauralee Sherwood, seventh edition. • Text book of physiology by Linda .S .Costanzo third edition • Text book physiology by Guyton &Hall,11th edition. • Physiology by Berne and Levy, sixth edition.