Susan Parker, MD. T he literature on mitral valve prolapse .... Griffith JPC: Mid systolic and late systolic mitral murmurs. Am J Med Sci 1892; 104: 285-294. 5.
I Editorials
Mitral valve prolapse: clinical and echocardiographic perspective Charles Pollick, MB Susan Wilansky, MD Susan Parker, MD
T he literature on mitral valve prolapse (MVP) continues to grow, with some authors emphasizing its benign nature and others the dire complications.L12 Because of this confusion physicians are understandably perplexed and even frightened by MVP, and these feelings are often transmitted to their patients. Now that 25 years have passed since MVP was first recognized,3 it is time to put it into perspective.
Historical background The association of midsystolic click and late systolic murmur was reported first in 18924 and again in 1903.5 While these reports attributed the murmur to the mitral valve, Gallavardin6 in 1913 attributed it to pleuropericardial adhesions, and this explanation was accepted for the next 50 years. In the 1960s the mitral valve was again implicated as the cause of the click and murmur,3'78 and this was substantiated by the concomitant angiographic findings of bulging of the mitral leaflets into the left atrium (prolapse) and mitral regurgitation.9 In the 1970s echocardiography brought with it both good and bad news. The good news was that typical patterns could be seen by M-mode echocardiography10-12 and later by two-dimensional echocardiography'3-15 in most patients with a midsystolic click and late systolic murmur; thus, an objective test replaced the stethoscope. The bad news was that such patterns could also be seen in "normal" subjects; this led to the term "silent prolapse", which also applies to prolapse detected by angiography but without auscultatory findings. A recent study suggested that silent prolapse may
be present in as many as 73% of normal subjects.'6
From the Division of Cardiology, Department of Medicine, Toronto Westem Hospital and University of Toronto
Reprint requests to: Dr. Charles Pollick, Division of Cardiology, Toronto Western Hospital, 399 Bathurst St., Toronto, Ont. M5T 2S8 -
For prescribing information see page 402
Articles on MVP in the 1960s and 1970s also focused on the complications. One study suggested no increase in risk for complications in patients with MVP,'7 whereas others reported an 8% incidence of infective endocarditis over a 13-year period18 and a 12.5% incidence of sudden death over a 10-year period.19 Taking the extreme figures,16"9 we could reach a facetious conclusion that 73% of the population has MVP, with a 1.25% annual incidence rate of sudden death. Clearly this is not the case; the diagnostic criteria and risk of complications of MVP must be reassessed.
Diagnosis of MVP The diagnosis of MVP is based on the presence of typical auscultatory or echocardiographic findings, or both. The electrocardiogram (ECG), patient history and associated conditions may lead to a suspicion of MVP but not, by themselves, to a
diagnosis. Auscultation
Typical auscultatory findings include a single midsystolic nonejection click, two or more mid- to late systolic clicks, a midsystolic click and murmur or a pansystolic murmur. An opening snap is rare. A split first heart sound is commonly mistaken for a nonejection click. For differentiation, the patient should be made to stand and squat. Standing decreases the left ventricular end-diastolic volume; thus, the click occurs earlier in systole, and the murmur is longer. Squatting increases the left ventricular end-diastolic volume; thus, the click occurs later in systole, and the murmur is shorter. Despite these considerations, auscultation is not always so precise, and the click and murmur may not behave so clearly. Also, typical auscultatory findings can be found in conditions other than MVP (e.g., papillary muscle dysfunction and aneurysm of the membranous septum).' CMAJ, VOL. 135, AUGUST 15, 1986
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Echocardiography The proportion of patients with typical auscultatory findings in whom echocardiography demonstrates prolapse depends on the type of auscultatory findings and the criteria used in analysing the echocardiogram. Patients who have isolated clicks and no murmurs seldom meet any echocardiographic criteria for prolapse.20 A normal echocardiogram in the presence of an obvious click may mean that the ultrasonic beam did not pass through all parts of the valve and missed the small areas that prolapsed or that the click reflects chordal stretching alone3 and not prolapse. Patients with an obvious murmur may have a normal echocardiogram as mitral regurgitation does not produce a demonstrable echocardiographic abnormality. The current consensus for criteria21'22 seems to be that MVP is present either when M-mode echocardiography shows posterior midsystolic or pansystolic movement at least 3 mm below the line of closure or when two-dimensional echocardiography in the parastemal long-axis view shows that any part of the mitral leaflets passes superior to the plane of the mitral anulus. At Toronto Western Hospital we studied 100, healthy volunteers by echocardiography and auscultation; in 5, prolapse was identified by auscultation. In this group, these criteria provided a sensitivity of 80%, a specificity of 96%, a positive predictive value of 50% and a negative predictive value of 99% for prolapse detected by auscultation. Like others16'22 we found that the apical four-chamber view of two-dimensional echocardiography was very sensitive (100%) but less specific (77%), and it had a low positive predictive value (19%) for prolapse detected by auscultation. Of the 95 volunteers with normal auscultatory findings, 21 (22%) had prolapse identified in the apical four-chamber view; this high proportion suggests that the so-called prolapse was actually normal "billowing". Such billowing is often not seen in the parasternal view of twodimensional echocardiography in the same subject, perhaps because the normal shape of the mitral anulus is a "hyperbolic paraboloid".23 On our echocardiography reports we refer to this abnormality of solitary "prolapse" in the apical fourchamber view as "nonspecific billowing".24
Electrocardiography
Ninety-five percent of patients who have MVP diagnosed by M-mode echocardiography have a normal ECG.25 The remaining 5Y% have the socalled typical changes of T-wave inversions in the inferior leads.26 Patient history
Atypical chest pain has frequently been de278
CMAJ, VOL. 135, AUGUST 15, 1986
scribed as a common manifestation of MVP. However, in the Framingham study25 atypical chest pain was found to be no more common in subjects who had MVP than in those who did not. Physicians should be discouraged from using propranolol or other fl-blockers for such chest pain; these drugs are usually not effective anyway in these cases.27 Another misconception is that patients with MVP are neurotic; a recent article has dismissed this notion.28 Associations MVP is sometimes associated with other conditions that may thus bring attention to the possibility of MVP or vice versa.29 The reasons for such associations are purely speculative.
Complications There are four main complications of MVP described in the literature: thromboembolism (stroke) in patients under the age of 45 years, mitral regurgitation requiring mitral valve replacement, infective endocarditis and sudden death. The annual risk of these complications to each person with MVP can be approximated with the frequency data from large clinical or pathological studies.30-33
Risk of complications The annual incidence rate of stroke in the total population under the age of 40 years is 1 in 33 000; 1 out of 3 such cases may be due to MVP. Therefore, a total population of 99 000 is required for one case of MVP-related stroke; since 5% of the total population has MVP (as detected by auscultation), the annual risk of stroke for people with MVP is approximately 1 in 5000 (according to Bayes' formula). A similar analysis can be performed for mitral regurgitation and infective endocarditis: the approximate annual incidence rate in the total population is 1 in 20 000 and 1 in 100 000 respectively; 1 out of 5 and 1 out of 4 respective cases may be due to MVP. Therefore, total populations of 100 000 and 400 000 respectively are required for one MVP-related case. Assuming a 5% prevalence rate of MVP the annual risk of mitral regurgitation and infective endocarditis for those with MVP is approximately 1 in 5000 and 1 in 20 000 respectively. MVP is so rare as the sole cause of sudden death that when it does occur it still warrants a case report. Pocock and colleagues33 identified only 42 cases of MVP-related sudden death in the world literature over a 10-year period, during which time approximately 350 000 people per year in North America died suddenly. If one presumes that 1 in 1000 cases of sudden death per year is due to
MVP, then with an approximate 5% prevalence rate of MVP the annual risk of sudden death for people with MVP is 1 in 40 000.
Risk of death The mortality rates of thromboembolism, mitral regurgitation and infective endocarditis are approximately 20%, 5% and 20% respectively. When these figures are applied to the already calculated complication rates, the mortality rates are 1 in 25 000, 1 in 100 000 and 1 in 100 000 respectively. Together with the estimate for sudden death, the annual mean risk of death from any one of these four complications is 1 in 12 000. This number by itself appears alarming, but not when compared with everyday risks.34 For example, the annual risk of dying from injuries suffered in a motor vehicle accident is 1 in 4500; the risk of death of a professor who flies regularly is 1 in 10 000. The risk of fatal penicillin anaphylaxis is 1 in 50 000, greater than the estimated risk of death from infective endocarditis (1 in 100 000). While some argue that this questions the use of antibiotic prophylaxis35 the official recommendation is that all patients who have MVP with a murmur should receive such prophylaxis.36 Finally, the quoted risk for MVP reflects a 5% incidence of auscultatory signs. If one included those with "silent prolapse", the calculated risk would be even less.
Recommendations MVP has traditionally been diagnosed by auscultation. When the auscultatory diagnosis is secure, echocardiography may add little, if anything, to patient care. We suggest that echocardiography be performed only in patients who have a characteristic murmur (not just a click), to determine chamber size for comparison with the results of later studies should mitral regurgitation increase and to confirm the diagnosis so as to justify lifelong antibiotic prophylaxis. If the echocardiogram is normal, a second auscultation may be justified before prophylaxis is recommended. Echocardiography for MVP is not indicated in the absence of auscultatory signs, except for subjects under the age of 45 years who have had an unexplained stroke, in whom there is a higher incidence of silent prolapse.37 There is certainly no evidence to suggest that subjects with atypical chest pain, palpitations or neurosis should undergo echocardiography for the diagnosis of MVP in the absence of auscultatory signs.
References 1. Cheitlin MD, Byrd RC: Prolapsed mitral valve: the commonest valve disease? Curr Probi Cardiol 1984; 8: 1-54 2. Oakley CM: Mitral valve prolapse: harbinger of death or
variant of normal? Br Med J 1984; 288: 1853-1854 3. Reid JVO: Mid systolic clicks. S Afr Med J 1961; 35: 353355 4. Griffith JPC: Mid systolic and late systolic mitral murmurs. Am J Med Sci 1892; 104: 285-294 5. Hall JN: Late systolic mitral murmurs. Am J Med Sci 1903; 125: 663-666 6. Gallavardin L: Pseudo-dedoublement du deuxieme bruit du coeur simulant le dedoublement mitral: par bruit extra cardiaque tdlesystolique surajoute. Lyon Med 1913; 121: 409-422 7. Barlow JB, Pocock WA, Marchand P et al: The significance of late systolic murmurs. Am Heart J 1963; 66: 444-452 8. Hancock EW, Cohn K: The syndrome associated with mid systolic click and late systolic murmur. Am J Med 1966; 41: 183-196 9. Criley JM, Lewis KB, Humphries JO et al: Prolapse of the mitral valve: clinical and cineangiographic findings. Br Heartj 1966; 28: 488-496 10. Shah PM, Gramiak R: Echocardiographic recognition of mitral valve prolapse [abstr]. Circulation 1970; 42: II45 11. Kerber RE, Isaeff DM, Hancock EW: Echocardiographic patterns in patients with the syndrome of systolic click and late systolic murmur. NEnglJMed 1976; 284: 691-693 12. Popp RL, Brown OR, Silverman JF et al: Echocardiographic abnormalities in the mitral valve prolapse syndrome. Circulation 1974; 49: 428-433 13. Sahn DJ, Allen HD, Goldberg SJ et al: Mitral valve prolapse in children. A problem defined by real time cross sectional echocardiography. Circulation 1976; 53: 651-666 14. Gilbert BW, Schatz RA, VonRamm OT et al: Mitral valve prolapse. Two-dimensional echocardiographic and angiographic correlation. Circulation 1976; 54: 716-723 15. Morganroth J, Jones RH, Chen CC: Two dimensional echocardiography in mitral, aortic and tricuspid valve prolapse. Am J Cardiol 1980; 46: 1164-1177 16. Gavin WA, Pearlman AS, Saal AK et al: Abnormal mitral leaflet coaptation: a non specific two dimensional echo finding [abstr]. Circulation 1983; 68: III365 17. Appelblatt NH, Willis PW, Lewhart JA et al: Ten to 40 year follow-up of 69 patients with systolic click with or without apical late systolic murmur [abstr]. Am J Cardiol 1975; 35: 119 18. Mills P, Rose J, Hollingsworth J et al: Long-term prognosis of mitral-valve prolapse. N Engl J Med 1977; 297: 13-18 19. Koch FH, Hancock EW: Ten-year follow-up of forty patients with the midsystolic click/late systolic murmur syndrome [abstr]. Am J Cardiol 1976; 37: 149 20. Wann LS, Grove JR, Hess TR et al: Prevalence of mitral prolapse by two dimensional echocardiography in healthy young women. Br HeartJ 1983; 49: 334-340 21. Levine RA, Weyman AE: Mitral valve prolapse: a disease in search of, or created by, its definition. Echocardiography 1984; 1:1-14 22. Warth DC, King ME, Cohen JM et al: Prevalence of mitral valve prolapse in normal children. J Am Col] Cardiol 1985; 5:1173-1177 23. Levine RA, Triulzi MO, Harrigan P et al: Mitral valve prolapse: another aspect of the "disease" created by the definition [abstr]. Circulation 1985; 72: III41 24. Pollick C, Wilansky S: Echocardiography reports and database by microcomputer. Echocardiography 1985; 2: 393400 25. Savage DD, Devereux RB, Garrison RJ et al: Mitral valve prolapse in the general population: 2. Clinical features: the Framingham study. Am HeartJ 1983; 106: 577-581 26. Jeresaty RM: Mitral Valve Prolapse, Raven, New York, 1979 27. Winkle RA, Lopes MG, Goodman DJ et al: Propranolol for patients with mitral valve prolapse. Am Heart J 1977; 93: 422-427 28. Uretsky BF: Does mitral valve prolapse cause non specific symptoms? IntJ Cardiol 1982; 1: 435-442 29. Malcolm AD: Mitral valve prolapse associated with other
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disorders. Br Heart J 1985; 53: 353-362 30. Hart RG, Easton JD: Mitral valve prolapse and cerebral infarction. Stroke 1982; 4: 429-430 31. Waller BF, Morrow AG, Maron BJ et al: Etiology of clinically isolated severe chronic pure mitral regurgitation: analysis of 97 patients over 30 years of age having mitral valve replacement. Am HeartJ 1982; 104: 276-288 32. Clemens JD, Horwitz RI, Jaffe CC et al: A controlled evaluation of the risk of bacterial endocarditis in persons with mitral-valve prolapse. N Engi J Med 1982; 307: 776781 33. Pocock WA, Bosman CK, Chesler E et al: Sudden death in
primary mitral valve prolapse. Am Heart 1 1984; 107: 378-
382 34. Hutt PB: Individual freedom and government control of food safety. Ann NYAcad Sci 1979; 329: 221-241 35. Bor H, Himmelstein DU: Endocarditis prophylaxis for patients with mitral valve prolapse. Am J Med 1984; 76: 711-720 36. Shulman ST, Amren DP, Bisno AL et al: Prevention of bacterial endocarditis. Circulation 1984; 70: 1123A-1 127A 37. Jackson AC, Boughner DR, Barnett HJM: Mitral valve prolapse and cerebral ischemic events in young patients. Neurology (NY) 1984; 34: 784-787
Midwifery and home births Robert A.H. Kinch, MD, FRCSC, FRCOG T hose of us who qualified in obstetrics in Commonwealth or European medical schools learned midwifery, or practical obstetrics, from experienced midwives. Traditionally, the midwife has been an autonomous professional. She works within certain limitations that in Britain are imposed by an autonomous board of midwives that grants state certification for midwifery. The article by Catherine McCourt in this issue of CMAJ (starting on page 285) points out that the issue of home births is quite separate from that of legalizing midwifery. At a recent symposium sponsored by the Society of Obstetricians and Gynaecologists of Canada, Professor Jelte de Haan, director of one of the three midwifery training schools in the Netherlands, highlighted the Dutch experience. He prefers that midwives be trained for 3 years in midwifery rather than be nurses with added midwifery training. Enthusiasts for domiciliary midwifery consider the Dutch experience to be the pinnacle of excellence, but de Haan stated categorically that planned home births are more dangerous for both the mother and the infant than births in hospital. He claimed that the selection process used to identify women at low risk of complications cannot predict the outcome very well, and in any case its use is not mandatory, so many twins, babies in breech presentation and babies weighing less than 2500 g are still delivered at home. Roughly 50% of these women need to be referred to hospital, usually during labour or delivery. De Haan prefers the idea of "outpatient" delivery, in which the patient delivers in hospital and is discharged home very soon after the birth of Dr. Kinch is obstetrician/gynecologist-in-chief at the Montreal General Hospital.
Reprint requests to: Dr. Robert A.H. Kinch, Department of Obstetrics and Gynaecology, Montreal General Hospital, 1650 Cedar Ave., Montreal, PQ H3G 1A4 280
CMAJ, VOL. 135, AUGUST 15, 1986
the infant. This system is being looked at in several units in Canada. The autonomous midwife - frequently selftrained - is a major anomaly in Canadian health care. the Association of Ontario Midwives has about 135 members. Cheryl Anderson,1 who before she became a physician was a self-taught midwife, feels that home births should be implicit in the revival of midwifery. Over 200 midwives, many self-taught, have provided care for thousands of women in their homes over the past 15 years in Canada. This is a situation that organized medicine, nursing and properly trained midwives should not contemplate with satisfaction. Midwifery is legal in the United States, but many practitioners are nurse-midwives who act as handmaidens to family physicians and obstetricians and rarely have complete responsibility. However, there are exceptions: the University of Southern California has good facilities for training midwives, and there is excellent cooperation between midwives and residents in obstetrics. The midwives handle a large volume of patients, most of them indigent.2 What do adequately trained Canadian midwives want? McCourt defines midwifery accurately in her article: the midwife will settle for nothing less than being trained to be responsible for prenatal care, delivery of the low-risk patient and postpartum care. This is her right and her proper objective. I believe that midwifery should be legalized in Canada, and that the self-taught midwife should cease to exist. If midwives are to be recognized they must first set up a board of accreditation along the lines of the British system, preferably in cooperation with obstetricians. This board should produce a curriculum and a complete training experience. The midwives will then have to persuade provincial governments to recognize their validity and accredit them as a group of professionals. This will
