Heart Sounds: S1, S2, and S3

Normal Auscultation Findings: S1

• Closure of the mitral and tricuspid valves during the cardiac cycle produces the S1 sound.
• The S1 sound is best auscultated at the mitral listening area on the chest.

Normal Auscultation Findings: S2

• S2 corresponds to the closure of the aortic and pulmonic valves.
• A2 is the aortic valve closing and typically occurs first due to higher pressure.
• P2 is the pulmonic valve closing.
• The S2 sound is best heard at the left upper sternal border.

Normal Auscultation Findings: S3

• S3, also known as a "Gallop," occurs during early diastole.
• Rapid ventricular filling in a dilated left ventricle causes blood to bounce off the walls.
• The phenomenon then creates turbulence and a murmur.
• This sound is best heard at the apex of the heart when the patient is lying on their left side.
• S3 can be normal in young athletes, or associated with systolic heart failure, dilated cardiomyopathy, and dilated ventricles.

Normal Auscultation Findings: S4

• S4, referred to as "Atrial kick," occurs in late diastole while blood enters into a stiff left ventricle.
• The atrium has to contract harder due to the increased pressure to facilitate ventricular filling.
• S4 is associated with diastolic heart failure, left ventricular hypertrophy (LVH), aortic stenosis, and chronic hypertension.

Bedside Maneuvers and Murmur Changes

• Various bedside maneuvers such as inspiration, hand grip, Valsalva, and squatting aid in diagnosing valvular disease by altering murmurs.
• A basic understanding of echocardiographic representation of cardiac events helps to identify valvular lesions.

Systolic vs. Diastolic Murmurs

• Murmurs vary in timing, intensity, location, and frequency
• Systolic murmurs occur between S1 and S2
• They can be crescendo-decrescendo or holosystolic murmurs
• Diastolic murmurs occur between S2 and S1, after S2
• These murmurs are typically decrescendo in nature
• Continuous murmurs are associated with patent ductus arteriosus (PDA)

Functional (Benign) Murmurs

• Functional murmurs are soft, systolic, short, and symptomless.
• Special tests reveal it, and S1/S2 sounds are normal on auscultation while standing or sitting.

Aortic Stenosis

• Aortic stenosis is a systolic murmur due to narrowed, stiffened aortic valve impeding blood flow from the left ventricle.
• A crescendo-decrescendo ejection murmur and a click are characteristic.
• It is loudest at the right upper sternal border (RUSB).
• Aortic stenosis is common in older individuals with early calcifications.
• The murmur can radiate to the carotid arteries.

Aortic Regurgitation

• Aortic regurgitation is a diastolic murmur where blood flows backward through the aortic valve during early diastole.
• It presents as a long, high-pitched, "blowing" decrescendo murmur.
• The murmur is best heard around Erb's point, and severe cases may cause bobbing of the head.

Mitral Regurgitation

• Mitral regurgitation is a systolic murmur.
• It presents as a holosystolic, high-pitched "blowing" murmur occurring between S1 and S2.
• Carvallo’s sign helps to differentiate between tricuspid and mitral regurgitation.
• Mitral regurgitation is loudest at the cardiac apex, can radiate to the axilla, and is common after myocardial infarction (MI).
• Tricuspid regurgitation is loudest at the lower left sternal border (LLSB) and commonly caused by right ventricular dilation.

Mitral Stenosis

• Mitral stenosis presents as a diastolic murmur.
• The valve becomes stiffened or stenotic thus impeding blood flow from the left atrium (LA) to the left ventricle (LV).
• An opening "snap" is auscultated after the S2 sound.
• The murmur is heard at the apex of the heart and can radiate to the axilla.
• It presents as a rumbling mid-to-late diastolic decrescendo murmur.
• Ortner syndrome can occur, where LA enlargement leads to compression of the esophagus and laryngeal nerve causing dysphagia and hoarseness.

Physiological Splitting of S2

• S1 precedes S2: A2 then P2 during expiration
• During inspiration, intrathoracic pressure decreases, which increases filling time in RA and RV
• There is an ↑ in venous return/ SV of RV, delaying closure of the pulmonic valve, with the P2 sound coming later due to the delay

Wide Splitting

• This is when A2/P2 can be differentiated because the right side of the heart isn't working properly
• During expiration, the A2/P2 split is slight
• During inspiration, the A2/P2 split is much more pronounced
• Conditions that delay emptying the RV due to the increase in the overload: RBBB, pulmonic stenosis, RV not contracting well, or pulmonary HTN

Fixed Splitting

• Fixed splitting involves a right venous return
• There is the same split between A2 and P2 during both expiration and inspiration
• Common in atrial septal defect

Paradoxical Splitting

• P2 precedes A2.
• It is wider during expiration because more blood flow is coming to the left side of the heart.
• Less wide during inspiration because more blood flow is coming to the right side of the heart.
• Common when there is a delayed closure of the aortic valve due to delay in left ventricular expulsion.
• Associated with aortic stenosis, LBBB, hypertrophic cardiomyopathy, and hypertension because anything that causes the afterload to be high.