Lutembacher Syndrome

Lutembacher syndrome is defined as a combination of mitral stenosis and a left-to-right shunt at the atrial level. Typically, the left-to-right shunt is an atrial septal defect (ASD) of the ostium secundum variety. Both these defects, ASD and mitral stenosis, can be either congenital or acquired.

The definition of Lutembacher syndrome has undergone many changes. The earliest description in medical literature is found in a letter written by anatomist Johann Friedrich Meckel to Albrecht von Haller in 1750. ^{[1, 2]} In 1916, Lutembacher described his first case of this syndrome, involving a 61-year-old woman, and he attributed the mitral valvular lesion to congenital mitral stenosis. ^{[1, 3]} Because the mitral stenosis was, in fact, rheumatic in etiology, the syndrome was defined eventually as a combination of congenital ASD and acquired, frequently rheumatic, mitral stenosis.

Thus, causes of mitral stenosis include the following:

• Mitral stenosis, often but not always rheumatic in origin ^[4]

• Congenital mitral stenosis (very rare)

• ASD, either congenital or iatrogenic

In the current era of mitral valvuloplasty for acquired mitral stenosis, however, residual iatrogenic ASD secondary to transseptal puncture is more common than congenital ASD, as is the combination of ASD and mitral stenosis. ^[3] Although this syndrome is generally defined as mitral stenosis in combination with ASD, some have argued to define the syndrome as a combination of ASD and any mitral valve lesion, ie, mitral stenosis, mitral insufficiency, or mixed lesion. Currently, any combination of ASD, congenital or iatrogenic, and mitral stenosis, congenital or acquired, is referred as Lutembacher syndrome.

Mitral stenosis can be either congenital, as initially described, or acquired in origin, often due to rheumatic mitral valve disease. Isolated mitral stenosis is now known to be a rare congenital disorder, and many cases of mitral stenosis initially thought to be congenital were, in fact, caused by rheumatic mitral valve disease.

Similarly, understanding of the etiology of atrial septal defect (ASD) as associated with Lutembacher syndrome has evolved over time. Initially, high left atrial pressure due to mitral stenosis was thought to stretch open the patent foramen ovale (PFO), causing left-to-right shunt and providing another outlet for the left atrium. Now ASD in this syndrome, like mitral stenosis, is recognized as being either congenital or acquired, as already described.

Acquired ASD is almost always iatrogenic, either intentional or as a complication of a percutaneous interventional procedure. The incidence of left-to-right atrial shunt following mitral valvuloplasty is estimated at 11-12%. Although most of these ASDs are small and hemodynamically insignificant, some can be large enough to have hemodynamic consequences, especially in patients who develop restenosis of the mitral valve.

The hemodynamic effects of this syndrome are a result of the interplay between the relative effects of ASD and mitral stenosis. In its initial description, the ASD was typically large in Lutembacher syndrome, thus providing another route for blood flow. Iatrogenic ASDs tend to be smaller but still may be hemodynamically significant. The direction of blood flow is determined largely by the compliance of left and right ventricles. Normally, the right ventricle is more compliant than the left ventricle.

As a result, in the presence of mitral stenosis, blood flows to the right atrium through the ASD instead of going backward into the pulmonary veins, thus avoiding pulmonary congestion. This happens at the cost of progressive dilatation and, ultimately, failure of the right ventricle and reduced blood flow to the left ventricle. Development of Eisenmenger syndrome or irreversible pulmonary vascular disease is very uncommon in the presence of large ASD and high left atrial pressure because of mitral stenosis.

The term reverse Lutembacher syndrome is sometimes used to describe those rare cases in which a predominant right-to-left shunt develops owing to development of severe tricuspid stenosis.

United States statistics

The true incidence of Lutembacher syndrome is not clearly known. Although mitral stenosis is encountered in 4% of patients with an atrial septal defect (ASD), congenital mitral stenosis itself is very rare, accounting for only 0.6% of congenital heart disease cases at autopsy. The incidence of ASD in patients with mitral stenosis is 0.6-0.7%. In one US study, the combination was found in 5 of 25,000 autopsies. The syndrome was diagnosed more frequently in the past for the following reasons:

• Without echocardiography, the combination of mid diastolic murmur, actually due to increased blood flow across the tricuspid valve, and systolic murmur of ASD led to a mistaken diagnosis of Lutembacher syndrome.

• The prevalence of both rheumatic heart disease and mitral stenosis was higher in western developed countries before the antibiotic era. With the decline in the frequency of rheumatic fever, the prevalence of mitral stenosis has decreased and so has diagnosis of the syndrome. A history of rheumatic fever is frequently absent.

• Even though ASD may be underdiagnosed in the United States, the combination of ASD and mitral stenosis may not be evident on physical examination and for that reason is best confirmed by echocardiography.

International statistics

Although the exact prevalence of Lutembacher syndrome is not known, it is probably higher in areas where rheumatic heart disease is still common.

Race-, sex-, and age-related demographics

No data are available regarding racial distribution of the condition.

Lutembacher syndrome is more common in females than males. Part of the reason is the higher incidence of both congenital ASD and rheumatic mitral stenosis in females.

This syndrome can present at any age. Cases have been diagnosed in the seventh decade of life. Lutembacher's original case was a 61-year-old woman who had been pregnant 7 times. In the current era of balloon mitral valvuloplasty and development of ASD, the age of presentation may change.

The overall prognosis is good for Lutembacher syndrome, especially in patients diagnosed early and without pulmonary hypertension. Patients with this condition have lived into their ninth decade without developing any cardiac symptoms, and women have had multiple pregnancies without complications.

Morbidity/mortality

No definite data are available regarding morbidity and mortality. Boths are related to the relative severity of the individual lesions.

Complications

Complications may include the following:

• Pulmoary hypertension and right-sided heart failure

• Atrial arrhythmias

• Pulmonary congestion

• Subacute bacterial endocarditis (SBE_

Educate patients regarding the basic anatomic defects and physiological consequences of Lutembacher syndrome.

Heart failure education should include the following:

• Low-salt diet

• Daily weighing

• Early warning signs of worsening right or left heart failure

Educate patients regarding the role of bacterial endocarditis prophylaxis.