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This is a clinician-written, evidence-based guide aligned to the MCC Examination Objectives. It is structured by clinical presentation — the way the MCCQE tests and the way patients actually present. Management reflects current Canadian guidelines (CMA, CFPC, CPS). Always cross-reference with institutional protocols and clinical judgment.
Key points
- Systolic murmurs are common and often benign; diastolic murmurs are ALWAYS pathological and require echo
- Innocent (flow) murmurs: soft (grade 1-2/6), systolic, midpeaking, no radiation, no associated symptoms, no abnormal heart sounds, change with position
- Key murmur descriptions: crescendo-decrescendo at RUSB radiating to carotids (AS), holosystolic at apex to axilla (MR), early diastolic decrescendo at LUSB (AR), low-pitched diastolic rumble at apex with opening snap (MS)
- Dynamic manoeuvres: Valsalva/standing increases HCM and MVP murmurs, decreases most others. Squatting/hand grip increases most murmurs, decreases HCM
- Echocardiogram is indicated for: any diastolic murmur, any symptomatic murmur, grade >=3/6 systolic, associated abnormal heart sounds (S3, S4, clicks), or clinical suspicion of valvular/structural disease
Approach to the Presentation
The approach to a cardiac murmur begins with: (1) Timing — systolic, diastolic, or continuous? (2) Location — best heard where? (3) Radiation — to carotids (AS), axilla (MR), back? (4) Character — crescendo-decrescendo (ejection), holosystolic (regurgitant), early diastolic (AR), rumbling (MS)? (5) Grade — 1-6/6 for systolic, 1-4/4 for diastolic. (6) Response to dynamic manoeuvres — Valsalva, squatting, hand grip, standing. (7) Associated findings — abnormal heart sounds, thrills, symptoms. The clinical context matters enormously: a soft systolic murmur in an asymptomatic young person is almost always innocent, while a new murmur in a febrile patient with risk factors for endocarditis is pathological until proven otherwise.
Differential Diagnosis
| diagnosis | likelihood | key features | distinguishing test |
|---|---|---|---|
| Endocarditis (new/changing murmur) | must-not-miss | New regurgitant murmur + fever + risk factors (IVDU, prosthetic valve, poor dentition). Vegetations cause valvular destruction | Blood cultures x3 + TTE (or TEE if prosthetic valve or TTE negative). Modified Duke criteria |
| Innocent (Flow) Murmur | common | Grade 1-2/6, midsystolic, no radiation, no associated symptoms, normal S1/S2, changes with position. Common in children, pregnancy, anaemia, febrile states, athletes | Clinical diagnosis. Echo only if features atypical or clinical doubt |
| Aortic Stenosis | common | Crescendo-decrescendo systolic at RUSB radiating to carotids. Late-peaking = more severe. Pulsus parvus et tardus, S4, narrow pulse pressure. Exertional symptoms (dyspnoea, angina, syncope) | Echo: AVA, mean gradient, peak velocity. Severe = AVA <1.0 cm2, gradient >=40, Vmax >=4 m/s |
| Mitral Regurgitation | common | Holosystolic at apex radiating to axilla. S3 if severe, displaced PMI. Chronic: dyspnoea, fatigue. Acute (papillary rupture post-MI): sudden pulmonary oedema | Echo: jet area, vena contracta, EROA, LVEF, LVESD |
| Mitral Valve Prolapse | common | Mid-systolic click + late systolic murmur. Standing/Valsalva = earlier click, longer murmur. Squatting = later click, shorter murmur. Usually benign | Echo: leaflet prolapse >= 2mm above annular plane. Most MVPs need no treatment |
| Aortic Regurgitation | less common | Early diastolic decrescendo at LUSB/Erb point, best sitting forward in expiration. Wide pulse pressure, bounding pulses, Austin Flint murmur | Echo: AR jet, vena contracta, holodiastolic flow reversal in descending aorta |
| Mitral Stenosis | less common | Low-pitched diastolic rumble at apex with opening snap (best in left lateral decubitus with bell). Rheumatic aetiology. Malar flush, loud S1 | Echo: MV area, mean gradient, leaflet morphology (Wilkins score) |
| Hypertrophic Cardiomyopathy | less common | Harsh systolic at LLSB. INCREASES with Valsalva and standing (opposite of most murmurs). Decreases with squatting. Young patient, family Hx SCD | Echo: asymmetric septal hypertrophy, SAM, LVOT gradient |
| VSD | less common | Harsh holosystolic at LLSB with thrill. Congenital or post-MI (ventricular septal rupture). Small restrictive VSD = loud murmur, large VSD = softer murmur + HF | Echo with colour Doppler: interventricular shunt |
| PDA | less common | Continuous "machinery" murmur at left infraclavicular area. Bounding pulses, wide pulse pressure. In neonates: may present as HF | Echo: continuous ductal flow. CXR: increased pulmonary vascularity |
Red Flags & Key History
Symptoms
New murmur + fever = endocarditis until proven otherwise
Murmur + exertional syncope = AS, HCM, or pulmonary HTN
Murmur + acute dyspnoea/pulmonary oedema = acute valvular pathology (papillary rupture, flail leaflet)
New murmur post-MI (day 2-7) = papillary muscle rupture (MR) or VSD
Any diastolic murmur = always pathological, requires echo
Asymptomatic grade 1-2 systolic murmur in young person, normal exam = likely innocent
Signs
Thrill (palpable vibration) = grade >=4/6 (always pathological)
Abnormal S2 (fixed split = ASD, paradoxical split = LBBB/severe AS, absent A2 = calcific AS)
S3 gallop (volume overload — HF, severe MR)
S4 gallop (non-compliant ventricle — LVH, diastolic dysfunction)
Opening snap before diastolic rumble (mitral stenosis)
Mid-systolic click (MVP)
Approach to Investigation
First-line
Transthoracic echocardiogram (TTE)Indications: any diastolic murmur, continuous murmur, grade >=3/6 systolic, holosystolic, any murmur with symptoms (dyspnoea, syncope, chest pain, HF), associated abnormal sounds (S3, S4, click), suspected endocarditis (fever + new murmur). NOT needed for a clearly innocent murmur in an asymptomatic patient with normal exam
ECGLVH (AS, HCM), LAE (MS, MR), RVH (pulmonary HTN, ASD), arrhythmia (AF common in MS/MR)
Second-line
CXRCardiomegaly, pulmonary congestion, valvular calcification, rib notching (coarctation)
TEEIf TTE inadequate, suspected endocarditis with negative TTE, prosthetic valve assessment, pre-operative evaluation for mitral repair
Management Principles
CCS Valvular Heart Disease Position Statement + ACC/AHA VHD Guideline (adapted for Canadian practice)1
Innocent murmur
- Reassurance — no treatment, no restriction, no follow-up imaging needed
- Ensure the murmur meets ALL criteria for innocent: systolic, soft, no radiation, no symptoms, no abnormal sounds, normal exam
2
Pathological murmur — general approach
- Echocardiogram to characterise and quantify
- Serial surveillance with echo at intervals based on severity (e.g., moderate AS: q1-2 years, severe asymptomatic AS: q6-12 months)
- Refer to cardiology for moderate-severe valvular disease or any symptomatic valvular lesion
- Intervention thresholds vary by valve and pathology — see specific condition guides
3
Endocarditis prophylaxis (current Canadian/AHA guidelines)
- Only for HIGHEST-RISK patients: prosthetic valve, prior endocarditis, certain unrepaired congenital heart disease, cardiac transplant with valvulopathy
- Only for DENTAL procedures involving gingival manipulation or periapical region
- Amoxicillin 2 g PO 30-60 min before procedure (clindamycin if penicillin allergy)
- NOT indicated for native valve disease (AS, MR, MVP), GI procedures, or GU procedures
MCCQE1 Exam Tips
- 1ALL diastolic murmurs are pathological — always order echo. Most systolic murmurs in young people are innocent
- 2The MCC tests murmur identification by description: crescendo-decrescendo at RUSB → carotids = AS. Holosystolic apex → axilla = MR. Early diastolic decrescendo LUSB = AR. Diastolic rumble at apex = MS
- 3Dynamic manoeuvres: HCM is the outlier — Valsalva/standing INCREASES the murmur (less preload = smaller LV = more obstruction). For nearly all other murmurs, Valsalva decreases the murmur
- 4Fixed split S2 = ASD. This is one of the most tested auscultation findings on the MCCQE1
- 5New murmur + fever: get 3 sets of blood cultures and an echo BEFORE starting antibiotics if possible (but do not delay antibiotics >1h)
- 6Endocarditis prophylaxis: only for highest-risk patients before dental procedures. Native valve disease (even severe AS) does NOT qualify
- 7MVP: mid-systolic click that moves earlier with standing/Valsalva. Most MVP is benign — reassure
- 8Post-MI murmur (day 2-7): new holosystolic murmur = papillary muscle rupture (MR) or VSD. Both are surgical emergencies
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