Second Heart Sound Key to Auscultation

1. Second Heart SoundKey to Auscultation Dr. I. Sathyamurthy MD, DM, FACC FRCP (Edin), FRCP (Glas), DSc (Honoris Causa) Sr. Interventional Cardiologist Apollo Hospitals, Chennai.

2. Heart soundsS2 • Has 2 components Aortic (A2) Pulmonary (P2) • Each coincides with the incisura of its arterial pressure wave • Inspiratory splitting of S2 – Due to delay in P2 • During inspiration pulmonary arterial incisura moves away from the descending limb of RV pressure due to increase in capaciitance of pulmonary vascular bed which delays the P2 • Expiration has the opposite effect.

4. S 2 • A2 louder audible at base, LSB and apex • P2 softer confined to 2nd LICS • During expiration A2 and P2 are separated by < 30 ms and are heard as single sound • During inspiration the splitting interval widens and A2 & P2 are heard as two distinct sounds

5. Abnormal splitting of S2 3 categories • Wide split Fixed Non fixed • Paradoxically split (Reversed) • Persistently single

7. Wide splitting of the second heart sound Delayed Pulmonic closure Delayed electrical activation of the right ventricle Prolonged right ventricular mechanical systole Decreased impedence of the pulmonary vascular bed (increased “hang out”) Early Aortic closure Shortened LV mechanical systole(LVET)

8. Wide splitting of s2 Causes of audible expiratory splitting of s2 I. Increased Q - P2 (Prolonged RV systole) (a) Hemodynamic causes • PS with intact septum ( A2-P2 delay > 100msec indicates an RV-PA gdt of 100mmHg when there is no infundibular stenosis ) • Massive Pulmonary embolism • PAH with RV failure • Idiopathic dilatation of PA • ASD (b) Electrical causes • Complete RBBB • PVC of LV origin • LV pacing • WPW with LV pre excitation

9. (II) Decreased Q - A2 Interval (Shortened LV systole) • MR • VSD • Pericardial tamponade • LA Myxoma • Constrictive pericarditis

10. Wide split s2 in Cyanotic heart disease • TAPVC • Single atrium • Ebsteins anamoly of tricuspid valve • ASD Eisenmenger • ASD with left to rt shunt ASD with PS and right to left shunt at atrial level • Primary Pulmonary hypertension Miscellaneous • Pectus excavatum • Occasionally normal children • Straight back syndrome

11. Fixed S2 split Interval between A2 & P2 is wide and persistent and remains unchanged during respiratory cycle • Hallmark finding of ASD • Delay in P2 is due to  Pulmonary vascular bed capacitance – and  Hangout interval (  interval between descending limbs of PA and RV pressure pulses ) – Split is wide • No significant respiratory variations in RV filling due to reciprocal changes in volume of left to right shunt –Split is fixed

12. What is hangout interval? • Semilunar valve is expected to close at point of cross over of ventricular and arterial pressure. • In reality it is not so • Time interval from cross over of pressures to actual occurrence of sound is called HANGOUT interval. • Just like a rolling ball is stopped by the friction offered by the ground, the ejection of blood is stopped by the resistance offered by the pulmonary vasculature

13. Since the pulmonary vascular resistance is low compared to the systemic vascular resistance, it takes some time for the blood flow from the right ventricle to stop • This corresponds to the hangout interval. • On the left side of the heart because impedance is much greater, the hangout interval between the aorta and LV pressure curves is negligible • Hang out interval may vary from 30 to 120 msec in the pulmonary vascular bed.

15. Hangout interval depends on interrelated factors like : • pressure beyond the valve • dilatation of the artery • distensibility of arterial system • vascular impedance • phase of respiration.

17. Reverse Splitting of the second heart sound • Delayed Aortic closure Delayed electrical activation of the LV Complete LBBB (Proximal type) RV paced beat RV ectopic beats Prolonged left ventricular mechanical systole Complete LBBB LVOT obstruction Hypertensive heart disease Arteriosclerotic heart disease Chronic IHD

18. Contd, Decreased impedence of the systemic vascular bed (increased “hang out”) Post stenotic dilatation of the aorta secondary to AS or AR PDA Early pulmonic closure Early electrical activation of the RV WPW syndrome type B

19. TYPES OF REVERSE SPLIT • Type 1: Classical reverse split • During expiration prolonged LV systole causes A2 to follow P2.with inspiration Q-P2 increased normally but Q-A2 is unchanged or shorten resulting a single second sound • Type 2: S2 reversal only in expiration(P2-A2), • normal in inspiration(A2-P2) • In lesser degrees of Q-A2 delay ,inspiration may still result in normal A2-P2 relationship and audible splitting,although s2 reversal occurs in expiration.

20. Reversed or parodoxic splitting Type 3 paradoxical split :S2 single in both phases of respiration (reverse split not detected by human ear as interval is < 20 msec both in inspiration and expiration) • Pseudo Reverse Split Only Type I Paradoxic splitting can be detected bedside. Type II and Type III can be diagnosed only by Phonocardiography .

21. Aortic Stenosis Mild Moderate Severe

22. Single S2 • Absence of either component of S2 or fusion of A2P2 without inspiratory split give rise to single S2 Absent A2 • Severe AS • Aortic atresia Absent P2 • Truncusarteriosus • Severe TOF • Severe PS • CHD associated with PS or Pulmonary atresia

23. contd., Fusion of A2 and P2 • Eisenmenger VSD • Single Ventricle Inaudibility of P2 • Emphysema • Obesity • Pericardial effusion • Posterior location of PA. Eg.TGA

24. Pulmonary Stenosis

25. Single A2 • A2 is the louder component in the pulmonary area and is the only component heard over the cardiac apex in normal individuals. Determinant of intensity of A2 • Aortic pressure • Relative proximity of aorta to chest wall • Size of the aortic root • Degree of the opposition of the valve leaflets • Valve mobility

26. Increased intensity of A2 • Systemic hypertension • Coarctation of Aorta • Ascending Aortic aneurysm • Relative anterior placement of the aorta - TOF,TGA Decreased intensity of A2 • AR(Lack of apposition of leaflets) • Valvular & supravalvular AS(Decreased arterial diastolic pressure)

27. Single P2 Increased intensity of P2 • Normally P2 is not audible at the apex. If P2 is louder than A2 in 2nd LICS or if it is audible at the apex- It is termed loud and indicates PAH • In ASD P2 may be audible at the apex in the absence of PAH because of RV enlargement and RV occupies the apex. • If P2 is very loud and banging it correlates to approximate mean PA pressure of > 50mmHg

28. Single P2 Determinants of intensity of P2 • PA pressure especially the diastolic pressure • Size of PA • Degree of apposition of PV leaflets Loud P2 • Eisenmenger ASD - Wide splitting of S2 with ↑ P2 • Eisenmenger PDA - Narrow splitting of S2 with ↑ P2 • Eisenmenger VSD – S2 is generally single SoftP2 • Pulmonary stenosis • TOF(Mild form)

29. Cyanotic Congenital Heart Disease Anomaly P2 ECG  PBF CTGA  RAD, RVH TAPVC  RAD, RAE, RVCD Common atrium  RVH, RAD / Superior Axis Common ventricle  Variable Truncus  CVH, RVH / LVH  PBF : No PAH TOF  RAD, RVH TOF, Like anomaly  RAD, RVH PS, Intact IVS + ASD  RV Strain Tricuspid atresia  LAD, LV dominance Ebstein’s  RAD, Low Voltage, RVCD  PBF : PAH Eisenmenger’s  RAD, RVH

30. Phonocardiography • Single Vs Closed split • Confirmation P2 or A2 • Reversed Splitting • For teaching purpose

31. Thank You