Abnormal Heart Sounds and Murmurs

Introduction

Understanding abnormal heart sounds and murmurs is crucial for success in the Medical Council of Canada Qualifying Examination Part I (MCCQE1). This comprehensive guide will help Canadian medical students prepare for questions related to cardiac auscultation, a key skill in the CanMEDS Medical Expert role.

Normal Heart Sounds

Before diving into abnormalities, let's review normal heart sounds:

1. S1: "Lub" - Closure of mitral and tricuspid valves
2. S2: "Dub" - Closure of aortic and pulmonic valves

Abnormal Heart Sounds

Extra Heart Sounds

1. S3 (Third Heart Sound)

   • Occurs in early diastole
   • Associated with volume overload or heart failure
   • More common in children and young adults (can be normal)

2. S4 (Fourth Heart Sound)

   • Occurs in late diastole
   • Associated with decreased ventricular compliance
   • Always pathological

3. Opening Snap

   • High-pitched, early diastolic sound
   • Indicates mitral stenosis

Clicks

• Systolic Click: Associated with mitral valve prolapse
• Ejection Click: Associated with aortic or pulmonic stenosis

Heart Murmurs

Heart murmurs are abnormal sounds produced by turbulent blood flow. They are classified based on timing, location, intensity, and quality.

Common Heart Murmurs

Canadian Guidelines for Heart Murmur Evaluation

The Canadian Cardiovascular Society (CCS) provides guidelines for the evaluation and management of patients with heart murmurs. Key points include:

1. All patients with newly discovered murmurs should undergo a thorough history and physical examination.
2. Echocardiography is recommended for patients with:
   • Symptoms suggestive of cardiac disease
   • Abnormal ECG findings
   • Murmurs grade 3/6 or higher
3. Referral to a cardiologist is advised for:
   • Complex or uncertain diagnoses
   • Symptomatic patients
   • Patients with severe valvular disease

Key Points to Remember for MCCQE1

• 🔑 Understand the timing and characteristics of normal and abnormal heart sounds
• 🔑 Be able to differentiate between systolic and diastolic murmurs
• 🔑 Know the common causes of heart murmurs in the Canadian population
• 🔑 Familiarize yourself with the Canadian guidelines for heart murmur evaluation
• 🔑 Recognize when to refer patients to a cardiologist based on CCS recommendations

MCCQE1 Practice: Mnemonics for Heart Murmurs

To help with MCCQE1 preparation, here's a Canadian-focused mnemonic for remembering systolic murmurs:

"MAPS of Canada"

• Mitral regurgitation
• Aortic stenosis
• Pulmonic stenosis
• Systolic flow murmurs (e.g., in pregnancy or anemia, common scenarios in Canadian healthcare)

Sample Question

A 65-year-old woman presents to her family physician in Toronto with increasing shortness of breath on exertion over the past 6 months. On physical examination, a harsh systolic murmur is heard at the right upper sternal border, radiating to the carotids. The murmur intensifies with squatting and decreases with standing. Which of the following is the most likely diagnosis?

• A. Mitral regurgitation
• B. Aortic regurgitation
• C. Mitral stenosis
• D. Aortic stenosis
• E. Hypertrophic cardiomyopathy

Explanation

The correct answer is:

• D. Aortic stenosis

This patient's presentation is classic for aortic stenosis:

1. Age and gender: Aortic stenosis is common in older adults, particularly women.
2. Symptoms: Exertional dyspnea is a typical symptom of aortic stenosis.
3. Murmur characteristics:
   • Harsh systolic murmur
   • Located at the right upper sternal border
   • Radiates to the carotids
4. Dynamic changes: The murmur intensifies with squatting (increased venous return) and decreases with standing (decreased venous return), which is characteristic of aortic stenosis.

In the Canadian context, it's important to note that aortic stenosis is a common valvular heart disease in the elderly population. Early recognition and appropriate referral for echocardiography and specialist assessment are crucial in the Canadian healthcare system to ensure timely intervention when necessary.

References

1. Baumgartner, H., Falk, V., Bax, J. J., De Bonis, M., Hamm, C., Holm, P. J., ... & Vahanian, A. (2017). 2017 ESC/EACTS Guidelines for the management of valvular heart disease. European heart journal, 38(36), 2739-2791.

2. Canadian Cardiovascular Society. (2004). The 2004 Canadian Cardiovascular Society consensus conference update for the management of heart failure. Canadian Journal of Cardiology, 20 Suppl A, 7A-19A.

3. Nishimura, R. A., Otto, C. M., Bonow, R. O., Carabello, B. A., Erwin, J. P., Fleisher, L. A., ... & Thompson, A. (2017). 2017 AHA/ACC focused update of the 2014 AHA/ACC guideline for the management of patients with valvular heart disease: a report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines. Journal of the American College of Cardiology, 70(2), 252-289.

4. Pellikka, P. A., Sarano, M. E., Nishimura, R. A., Malouf, J. F., Bailey, K. R., Scott, C. G., ... & Tajik, A. J. (2005). Outcome of 622 adults with asymptomatic, hemodynamically significant aortic stenosis during prolonged follow-up. Circulation, 111(24), 3290-3295.

5. Teo, K. K., Corsi, D. J., Tam, J. W., Dumesnil, J. G., & Chan, K. L. (2011). Lipid lowering on progression of mild to moderate aortic stenosis: meta-analysis of the randomized placebo-controlled clinical trials on 2344 patients. Canadian Journal of Cardiology, 27(6), 800-808.