What conditions cause systolic murmurs that run through S2?

Conditions include the following:

• mitral insufficiency (pansystolic murmur);

• tricuspid insufficiency (pansystolic murmur)

• ventricular septal defect (pansystolic murmur); and

• mitral valve prolapse (late systolic murmur).

What is mitral valve prolapse?

Mitral valve prolapse is just what its name implies. The valvular apparatus with its chordae tendineae is too big for the ventricle, so one or both leaflets of the valve prolapse into the left atrium during systole. Common synonyms are prolapsed mitral valve, floppy mitral valve or Barlow’s syndrome.

Two variants of mitral valve prolapse are recognized and can be distinguished with two-dimensional echocardiography: a common benign form and a rare but serious variant. In the benign form, the cardiac valves are normal (normal variant mitral valve prolapse). The community prevalence rate is about 2.5%. In the serious variant (primary mitral valve prolapse), the cardiac valves are deformed. This form of the disorder is usually seen in older men or patients with connective tissue disorders (e.g., Marfan’s syndrome, Ehlers-Danlos syndrome or pseudoxanthoma elasticum).

What are the symptoms of normal variant mitral valve prolapse?

Aside from a possible increased incidence of palpitations, no symptoms are associated with normal variant mitral valve prolapse. The numerous earlier studies linking mitral valve prolapse to fatigue, anxiety, phobias, panic disorder, chest pain, etc., have been discredited due to design flaws.

What complications may ensue from mitral valve prolapse?

Patients with mitral valve prolapse may go on to develop clinically significant mitral valve regurgitation and congestive failure. While very few patients with mitral valve prolapse develop significant mitral regurgitation, about 25% of individuals with severe mitral valve regurgitation have mitral valve prolapse as a cause of their condition. Endocarditis may also complicate mitral valve prolapse, but only in those patients with deformed valves or those who have a clinically audible murmur.

Which patients with mitral valve prolapse require endocarditis prophylaxis?

Antibiotic prophylaxis is mandatory for patients with primary mitral valve prolapse. It is not required for those with normal variant mitral valve prolapse who do not have a murmur.

What are the physical signs of mitral valve prolapse?

The major clinical findings in patients with mitral valve prolapse are clicks and murmurs that may vary in intensity and timing with changes of position.

• A systolic murmur: Best heard with the diaphragm, it is the most characteristic finding of mitral valve prolapse. Classically, this murmur is a mid to late systolic murmur that runs through S2. In about 10% of cases, it is a pansystolic murmur. It is best heard at the apex or lower left sternal border. The loudness of the murmur is variable. In many patients it is relatively soft, but in a few it is loud and “honking” or “whooping” and may be heard by the patients themselves (it is grade 6/6). The timing and duration of the murmur may change according to the patient’s position (see below).

• Midsystolic click(s): One or more midsystolic clicks, best heard with the diaphragm, are a characteristic finding of mitral valve prolapse. Multiple clicks are common. Clicks are best heard at the apex and their character, number and timing may change according to the patient’s position. An important point to remember is that while many patients have both murmur and click(s), some have only the murmur and some only one or more clicks.

What manoeuvres will help diagnose mitral valve prolapse?

Any manouevre that decreases cardiac volume (venous return) will exaggerate the prolapse and cause it to occur earlier in systole. Typical manouevres that do this are sitting, standing or performing a Valsalva’s manoeuvre. When any of these are done, the murmur will start earlier and usually becomes louder. Clicks may only be audible with one of these manouevres, or a single click may become multiple. The click or clicks tend to move closer to the first sound.

What is the mechanism of production of clicks in mitral valve prolapse?

One theory is that as the valve prolapses, the chordae tendinae are pulled taut and vibrate. This seems unlikely. An alternative explanation is that one or more portions of a leaflet balloons back into the atrium and their sudden arrest makes the noise.

What are the characteristics of the murmur of mitral insufficiency?

The murmur of mitral insufficiency, or mitral regurgitation, is usually easily detected. It is high-pitched and blowing, and is best heard with the diaphragm. It is loudest at the apex, and radiates to the axilla and sometimes to the lower left sternal border and base. It is a pansystolic murmur that starts with S1 and runs through S2. It does not increase in intensity with inspiration, as does the murmur of tricuspid insufficiency.

Associated findings of mitral insufficiency are:

• a laterally displaced and augmented apical impulse;

• a diminished S1;

•an S3; and

• a bounding pulse (if there is a large volume of regurgitating blood).

What are the characteristics of the murmur of tricuspid insufficiency?

The murmur of tricuspid insufficiency is high-pitched and blowing, and best heard with the diaphragm. It is pansystolic and is loudest at the left lower sternal border. It may radiate to the right of the sternum and as far left as the midclavicular line but, unlike the murmur of mitral insufficiency, it does not radiate to the left axilla. It usually increases in intensity with inspiration because this causes an increased blood flow into the right side of the heart.

What are the associated findings in tricuspid insufficiency?

The associated findings are:

• an augmented right ventricular impulse; and

• giant v-waves in the jugular veins.

What are the characteristics of the murmur of ventricular septal defect?

The murmur of a ventricular septal defect is usually a loud (grade 4 or 5), pansystolic, high-pitched murmur loudest over the third, fourth and fifth interspaces just to the left of the sternal border. It is best heard with the diaphragm. It may radiate over the precordium, but not into the left axilla.

What are the associated findings in ventricular septal defect?

• Presence of a thrill over the lower left sternal border in many cases; and

• a bounding pulse (if there is a large left to right shunt).

References

1. Nishimura RA, McGoon MD. Perspectives on mitral valve prolapse (editorial). N Engl J Med 1999;341:48-50.

The late Dr. Kenneth Marshall was a former professor of family medicine at University of Western Ontario medical school.