Heart Sounds

Anatomy of the Thoracic Cage for Cardiac Landmarks

• To understand heart sounds, one must master the superficial anatomy of the chest and its relation to the underlying structures.
• The Jugular Notch: This is the visible dip at the top of the sternum, between the clavicles.
• The Manubrium: The superior portion of the sternum, shaped roughly like a handle.
• The Sternal Angle (Angle of Louis):
  • This is the point where the manubrium joins the body of the sternum.
  • Identification: Place fingers in the jugular notch and slide downward until you feel a distinct ridge or "hang up."
  • Significance: The sternal angle is the landmark for the attachment of rib number 2. This allows clinicians to count ribs and identify intercostal spaces accurately.
• The Sternal Body: The long, flat portion of the sternum extending downward from the sternal angle.
• The Xiphoid Process: The small, cartilaginous/bony process at the inferior end of the sternum.
• Rib Attachments and True Ribs:
  • There are 7 "true ribs" that attach directly to the sternum via costal cartilages.
  • Rib 1: Attaches above the sternal angle.
  • Rib 2: Attaches at the sternal angle.
  • Ribs 3, 4, 5, 6, and 7: Attach sequentially to the body of the sternum.
  • Rib 7 may share cartilage with rib 6 and attaches just before or near the xiphoid process.

Heart Orientation and the Apical Pulse

• General Positioning: For most individuals, approximately $\\frac{2}{3}$ of the heart's mass is located on the left side of the body.
• Spatial Orientation (The Top Metaphor):
  • Standard illustrations show the heart sitting upright, but in reality, the atria are located behind the ventricles.
  • Imagine an acorn spinning like a top; as it wobbles and falls back, it orients to the left and tips backward. This is how the heart sits in the chest.
• The Apex of the Heart:
  • The pointed "bottom" of the heart (the apex) is found in the 5th intercostal space on the left side of the body.
  • Intercostal Spaces ($ICS$): These are the spaces between the ribs. The 1st $ICS$ is between ribs 1 and 2, the 2nd $ICS$ between ribs 2 and 3, and so on.
• The Apical Pulse:
  • This is the physical sensation of the left ventricle contracting and striking the chest wall.
  • It is located at the 5th $ICS$ on the left.
  • Clinical Distinction: The apical pulse is different from peripheral pressure points (radial, brachial, carotid, inguinal, pedal, or femoral). While peripheral pulses measure blood pressure waves, the apical pulse measures actual physical heart contraction.
  • Significance in Emergencies: In cases of extreme bradycardia, very fast heart rates, or low blood pressure, peripheral pulses may be undetectable. The apical pulse allows a clinician to determine if the heart is actually beating or fibrillating.
  • Personal Anecdote: The speaker recounts a student collapsing on campus. While peripheral pulses were absent, the speaker felt the apical pulse and identified that the heart was fibrillating. The student was also receiving internal shocks from an implanted pacemaker.

Clinical Auscultation of Heart Valves

• Auscultation: The act of listening to sounds from the heart, lungs, or other organs, typically using a stethoscope.
• Stethoscope Practicality:
  • Head Rotation: Many stethoscopes have a rotating head that must be "turned on" to the correct side. Test this by tapping gently on the diaphragm; do not tap hard as it can injure the ears.
  • Earpiece Orientation: Earpieces should be inserted "counterintuitively," angled forward toward the nose to better align with the ear canals.
• Valve Listening Locations (Sites of Echoing):
  • Because the great vessels (aorta and pulmonary trunk) dive back behind the heart, the sounds of their valves echo to specific areas on the chest.
  • Aortic Semilunar Valve: Listened to at the 2nd intercostal space to the right of the sternum.
  • Pulmonary Semilunar Valve: Listened to at the 2nd intercostal space to the left of the sternum.
  • Mitral (Bicuspid/Left AV) Valve: Listened to at the 5th intercostal space to the left of the sternum (the apex area).
  • Tricuspid (Right AV) Valve: Listened to at the 5th intercostal space to the right of the sternum.

Pathological Heart Sounds and Mechanisms

• The Silent Heart: In a healthy system, blood flow is silent as it strikes the slippery endothelium. Sound only occurs during collisions or turbulence.
• 1. Whooshing or Swishing Sound (Regurgitation):
  • Cause: An "incompetent" or weak/flimsy valve.
  • Mechanism: The valve fails to prevent the backflow of blood (regurge). When the ventricles contract, blood bubbles back into the atria.
  • Metaphor: A piece of cardboard or a raisin box lid that has been soaked in water. When you blow into it, it makes a wet, gurgling sound because it is flimsy.
  • Example: Mitral valve prolapse, where the valve bends the wrong way, allowing blood to leak back into the left atrium during ventricular contraction.
• 2. Screeching or Clicking Sound (Stenosis):
  • Cause: A "stenotic" or stiff valve.
  • Mechanism: The valve is narrowed or hardened. When blood is forced through, the stiff leaflets vibrate at a high frequency.
  • Metaphor: A dry, stiff piece of paper or a reed on a clarinet that is overtightened. It produces a sharp, high-pitched screech or click.
• 3. Creaking Sound (Friction Rub):
  • Cause: Inflammation of the pericardium (Pericarditis).
  • Mechanism: The heart or the visceral pericardium rubs against the fibrous pericardium (the ligament of the heart).
  • Metaphor: A rusty hinge on a door or the sound of joints creaking when walking up stairs due to ligaments rubbing.

Inflammation and Cardiac Tamponade

• Pericarditis: Inflammation of the pericardium which causes friction rub.
• Cardiac Tamponade:
  • A condition where Fluid (often blood from damage caused by friction) accumulates in the pericardial space.
  • Effect: The accumulated fluid prevents the heart from expanding and filling properly, disrupting cardiac dynamics.
• Pericardiocentesis (Aspirating Fluid):
  • Fluid is often removed via a needle in the 5th intercostal space.
  • Precautions: The clinician must go above the 6th rib rather than below the 5th rib.
  • Anatomical Reasoning: In the subcostal groove (underneath each rib), there is a vein, an artery, and a nerve ($VAN$). Sticking a needle under a rib risks hitting these structures; going above the rib (in the space) avoids them.

Physiology of Normal Heart Sounds (Lub-Dup)

• Healthy Sound: A healthy heart only produces the "Lub-Dup" rhythm and is otherwise silent.
• Lubb ($S_1$):
  • Character: A longer, duller sound (ending in a 'b').
  • Timing: Occurs when the ventricles contract.
  • Mechanism: Blood is ejected and collides with the closing AV valves (tricuspid and bicuspid/mitral).
  • Metaphor: It is not the "slamming of the doors" but the "wind hitting the doors."
• Dupp ($S_2$):
  • Character: A sharper, snapping sound (ending in a 'p').
  • Timing: Occurs when the ventricles begin to relax.
  • Mechanism: Ventricular pressure drops, and pressure in the elastic arteries (aorta/pulmonary trunk) remains high. Blood tumbles back down toward the heart and is caught by the semilunar valves.
  • Structure: Semilunar valves lack chordae tendineae and are thicker/sturdier to maintain integrity against the cascading blood, resulting in the sharper snap.
• Sounds of Korotkoff: Tapping sounds heard specifically when measuring blood pressure in the peripheral vessels, not to be confused with primary heart sounds.