Murmur Localization on Step 1: Systolic vs Diastolic
Cardiovascular · 8 min read · 2026-05-16
Introduction
Murmur identification is a recurring Step 1 theme because it forces integration of cardiac cycle physiology, valve anatomy, and hemodynamics into a single testable moment. Questions rarely just ask "name the murmur." They ask you to predict how a maneuver changes intensity, or to connect a murmur to a downstream complication. The fastest way to get these right is to stop memorizing sounds in isolation and instead build a reasoning chain: timing, location, radiation, then maneuver response.
Step 1: Fix the Timing
Every murmur question starts with systole vs diastole relative to S1 and S2.
- Systolic murmurs occur between S1 and S2 (ventricles contracting). Common causes: aortic stenosis, mitral regurgitation, tricuspid regurgitation, ventricular septal defect, hypertrophic cardiomyopathy.
- Diastolic murmurs occur between S2 and the next S1 (ventricles filling). Common causes: aortic regurgitation, mitral stenosis, pulmonic regurgitation.
Mnemonic reasoning: stenosis of the semilunar valves (aortic, pulmonic) and regurgitation of the AV valves (mitral, tricuspid) are both systolic, because both processes obstruct forward flow or leak backward during ventricular contraction. Conversely, semilunar regurgitation and AV stenosis are diastolic.
Step 2: Localize by Auscultation Point
Use the standard four-point map, then let radiation confirm the diagnosis.
- Aortic area (right 2nd intercostal space): aortic stenosis, radiates to carotids
- Pulmonic area (left 2nd intercostal space): pulmonic stenosis or flow murmurs
- Tricuspid area (left lower sternal border): tricuspid regurgitation, VSD
- Mitral area (apex, 5th intercostal space midclavicular line): mitral regurgitation, mitral stenosis, radiates to axilla for MR
Step 3: Apply Maneuvers to Confirm
Maneuvers alter preload, afterload, or venous return, and the murmur response is diagnostic.
- Inspiration increases venous return to the right heart, so right-sided murmurs (tricuspid regurgitation, pulmonic stenosis) get louder. This is the Carvallo sign.
- Valsalva strain phase decreases venous return and preload. Most murmurs soften, but hypertrophic cardiomyopathy and mitral valve prolapse get louder because a smaller ventricle worsens outflow obstruction or leaflet prolapse.
- Squatting increases venous return and afterload. Hypertrophic cardiomyopathy and mitral valve prolapse soften, while aortic stenosis becomes more prominent as stroke volume increases.
- Handgrip increases systemic vascular resistance and afterload. Murmurs of regurgitation (mitral regurgitation, aortic regurgitation, VSD) get louder because more blood is pushed backward; aortic stenosis softens slightly since forward flow is relatively favored less.
Worked Example
A 19-year-old college athlete has a systolic murmur that increases with Valsalva and standing, and decreases with squatting. This pattern points away from aortic stenosis (which would soften with Valsalva) and toward hypertrophic cardiomyopathy, where reduced ventricular volume worsens dynamic outflow obstruction. The clinical stakes are high because this is a leading cause of sudden cardiac death in young athletes.
Comparison Table: Classic Murmurs
Common Pitfall
Students often confuse the direction of maneuver effects between hypertrophic cardiomyopathy and aortic stenosis because both are systolic murmurs heard near the left sternal border. Remember that hypertrophic cardiomyopathy is a dynamic obstruction that worsens with a smaller left ventricular cavity (Valsalva, standing) and improves with a larger cavity (squatting, handgrip), which is the opposite pattern from fixed valvular aortic stenosis.
Clinical Pearl
A widened pulse pressure with a diastolic decrescendo murmur at the left sternal border should immediately suggest aortic regurgitation. Look for associated signs in vignette stems such as bounding pulses, head bobbing, or a history of bicuspid aortic valve or aortic root dilation from conditions like Marfan syndrome or tertiary syphilis.
Summary
Approach every murmur question in three steps: determine timing relative to S1 and S2, localize using the four auscultation points and radiation pattern, then confirm using the predictable direction of preload and afterload maneuvers. This structured reasoning converts a memorization-heavy topic into a repeatable algorithm that holds up even for unfamiliar vignette phrasing on test day.
Additional High-Yield Associations
Beyond the four classic auscultation points, Step 1 vignettes often layer in complications and associated findings to test deeper understanding.
- Aortic stenosis: syncope, angina, and heart failure symptoms form the classic triad; a calcified bicuspid valve is the most common cause under age 65, while degenerative calcification dominates in older patients. Watch for acquired von Willebrand disease and angiodysplasia (Heyde syndrome) as a testable complication.
- Mitral regurgitation: acute MR from papillary muscle rupture after inferior MI presents with sudden pulmonary edema and a new systolic murmur; chronic MR can be due to myxomatous degeneration, rheumatic disease, or ischemic dysfunction.
- Mitral stenosis: almost always rheumatic in origin; look for a history of pharyngitis, atrial fibrillation from left atrial enlargement, and an opening snap whose interval from S2 shortens as severity increases.
- Aortic regurgitation: causes include bicuspid valve, endocarditis, aortic root dilation, and rheumatic disease; chronic severe AR produces a hyperdynamic circulation with wide pulse pressure.
- VSD: a harsh holosystolic murmur at the left lower sternal border in a newborn suggests a congenital VSD; in an adult with recent MI, a new murmur in this location suggests septal rupture, a surgical emergency.
Why Maneuvers Work: The Physiology Behind the Answer
Rather than memorizing which maneuver goes with which murmur, understand the underlying volume and pressure changes so you can derive the answer even for unfamiliar combinations.
- Increased preload (leg raise, squatting) increases ventricular volume, which stretches a stenotic valve orifice relatively less than it increases flow, so most stenotic and regurgitant murmurs get louder, while hypertrophic cardiomyopathy improves because the outflow tract widens.
- Decreased preload (Valsalva strain, standing) shrinks ventricular volume, worsening dynamic outflow obstruction in hypertrophic cardiomyopathy and mitral valve prolapse (earlier, longer click and murmur), while softening most other murmurs.
- Increased afterload (handgrip, phenylephrine) makes the ventricle work harder against resistance, which augments regurgitant murmurs (blood preferentially flows backward against a leaky valve) and softens the aortic stenosis murmur slightly because relative forward flow decreases.
Practice Approach for Exam Day
When a vignette describes a murmur, resist the urge to jump straight to a diagnosis. Instead, extract the four data points in order: timing, location, radiation, and maneuver response. Cross-check all four against the table below before committing to an answer. This habit prevents common errors such as confusing mitral regurgitation with tricuspid regurgitation, both holosystolic murmurs that are distinguished mainly by location and the inspiratory maneuver.