Hearing Heartbeat Over the Back with a Stethoscope
Hearing cardiac sounds over the posterior thorax, particularly around the left scapular region, most commonly indicates either aortic coarctation with collateral vessel formation or posterior/posterolateral myocardial pathology, though it may also represent normal sound transmission in thin individuals.
Primary Diagnostic Considerations
Aortic Coarctation with Collateral Circulation
A murmur or bruit heard in the left interscapular position is a classic finding in aortic coarctation, caused either by turbulent flow through the narrowed aortic segment itself or by blood flowing through extensive collateral vessels that develop to bypass the obstruction 1.
Continuous murmurs may be present over the parasternal areas (from mammary arteries) and around the left scapula when collateral vessels are present 1.
Occasionally, periscapular collaterals can be palpated in addition to being audible 1.
Look for associated findings: hypertension in the right arm relative to lower extremities, pulse delay between the right arm and femoral arteries, and hyperdynamic carotid pulsations 1.
Posterior Wall Myocardial Infarction
Posterior chest leads (V7, V8, V9) should be placed when posterior MI is suspected, with V7 at the posterior axillary line, V8 below the scapula, and V9 at the paravertebral border 2, 3.
The American Heart Association recommends recording these posterior leads when isolated ST depression ≥0.05 mV appears in leads V1-V3, as this represents reciprocal changes from posterior ST elevation 2.
ST elevation ≥0.05 mV in any of V7-V9 confirms posterior STEMI and warrants immediate reperfusion therapy 2.
Critical pitfall: Approximately 4% of acute MI patients have ST elevation isolated to posterior leads that is "hidden" from the standard 12-lead ECG 4.
Valvular Heart Disease Considerations
Radiation Patterns of Cardiac Murmurs
Cardiac murmurs can radiate to various locations based on the direction of turbulent blood flow 1.
The location and radiation of murmurs, combined with their timing, configuration, pitch, and intensity, help determine their origin 1.
Right-sided murmurs generally increase with inspiration, while left-sided murmurs are usually louder during expiration 1.
Associated Valvular Lesions in Coarctation
When coarctation is present, auscultation should specifically assess for bicuspid aortic valve (BAV), which commonly coexists 1.
Listen for a parasternal and apical systolic ejection sound (suggesting BAV), a systolic crescendo-decrescendo murmur (indicating left ventricular outflow tract obstruction), or an early diastolic decrescendo murmur (indicating aortic regurgitation) 1.
Diagnostic Algorithm
Step 1: Characterize the Sound
Determine if you are hearing a murmur, bruit, or normal heart sounds that are simply transmitted posteriorly 1.
Assess timing: systolic, diastolic, or continuous 1.
Diastolic murmurs virtually always represent pathological conditions and require further cardiac evaluation 1.
Step 2: Assess Blood Pressure and Pulses
Measure blood pressure in both arms and at least one leg 1.
Palpate for pulse delay between the right arm and femoral/popliteal arteries 1.
A difference suggests coarctation, especially if upper extremity hypertension is present 1.
Step 3: Perform Complete Cardiac Examination
Palpate the precordium for left ventricular dilatation 1.
Assess carotid pulsations for hyperdynamic quality 1.
Attempt to palpate periscapular collateral vessels 1.
Step 4: Obtain Appropriate Imaging
Echocardiography with Doppler is essential to evaluate for coarctation (suprasternal notch view of aortic arch), assess aortic valve anatomy, measure left ventricular size and function, and rule out associated lesions 1.
Chest X-ray may show rib notching (ribs 3-9) from collateral vessels, a "3 sign" at the coarctation site, or a dilated ascending aorta 1.
If posterior MI is suspected based on ECG findings, obtain posterior leads V7-V9 immediately and measure cardiac troponin 4, 2.
Common Pitfalls to Avoid
Do not dismiss posterior cardiac sounds as insignificant without systematic evaluation, as they may represent serious pathology requiring urgent intervention 1, 2.
In suspected inferior MI with anterior ST depression, failure to record posterior leads V7-V9 may miss a posterior STEMI that requires immediate reperfusion rather than NSTEMI management 2.
When coarctation is identified, all available family members should be screened, as it has a strong likelihood of being inherited 1.
Abundant collateral vessels may reduce the gradient across a coarctation and mask the severity of obstruction, so the absence of a loud murmur does not exclude significant disease 1.