Lutembacher Syndrome

Introduction
Background

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. 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. Because the mitral stenosis was, in fact, rheumatic in etiology, the syndrome was defined eventually as a combination of congenital ASD and acquired, almost always rheumatic, mitral stenosis.

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. 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.

Pathophysiology

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

Similarly, understanding of the etiology of 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.

Frequency
United States

The true incidence of the syndrome is not clearly known. Although mitral stenosis is encountered in 4% of patients with an 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

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

No definite data are available. Mortality and morbidity rates are related to the relative severity of the individual lesions.
Race

No data are available regarding racial distribution of the condition.
Sex

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.
Age

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.
Clinical
History

Patients may remain asymptomatic for many years. Symptoms are mainly due to the ASD, and signs and symptoms vary according to the size of the ASD. With a large ASD, symptoms of pulmonary congestion, typical of isolated mitral stenosis, do not appear until late in the course of the disease. Conversely, these symptoms may appear early if the patient has an associated small ASD or develops pulmonary hypertension for other reasons. Patients with large ASD and moderate-to-severe mitral stenosis have signs and symptoms due mainly to right ventricular overload and right-sided heart failure, while patients with a small ASD and moderate-to-severe mitral stenosis have signs and symptoms of pulmonary congestion typical of mitral stenosis.

The patient may or may not have a history of rheumatic fever.
Fatigue and reduced exercise tolerance result from decreased systemic blood flow. The presence of mitral stenosis and left-to-right blood flow in diastole through the ASD reduces the forward flow of blood into the left ventricle, thereby reducing systemic blood flow and leading to fatigue and poor exercise tolerance.
Palpitations are a common presenting symptom. Because of the augmented left-to-right shunt caused by higher left atrial pressure and mitral stenosis, both atria are dilated. This predisposes patients to atrial arrhythmias; atrial fibrillation is very common.
Weight gain, ankle edema, right upper quadrant pain, and ascites are seen more commonly in patients with large ASD. Such symptoms are manifestations of the development of right-sided heart failure. A chronically increased left-to-right blood flow at the atrial level can eventually lead to right-sided heart failure.
Paroxysmal nocturnal dyspnea, orthopnea, and hemoptysis are signs of pulmonary venous congestion. Such symptoms are caused by mitral stenosis and are seen less frequently in Lutembacher syndrome than in isolated mitral stenosis. They are more common in patients with small ASD and are probably more common in patients who develop reverse Lutembacher syndrome. In some patients with large pulmonary blood flow due to a large left-to-right shunt, orthopnea can develop because of decreased compliance of the lungs.

Physical

Physical examination reveals signs due to the ASD and mitral stenosis, which are modified because of the presence of both lesions in the same patient.

Arterial pulse
Small volume
Rhythm regular or irregular -Atrial fibrillation most common arrhythmia
Jugular venous pulse
Distended jugular veins, even in the absence of right heart failure
Large a waves when sinus rhythm is present
Increased right ventricular pressure a more important determinant than equalization of atrial pressures in increasing jugular venous pressure
Precordial examination
Left parasternal lift, caused by transmitted right ventricular and pulmonary artery impulse, is common.
Left ventricular impulse is unimpressive, owing to reduced filling of the left ventricle secondary to mitral stenosis.
A tapping apex impulse due to the palpable, loud first heart sound of mitral stenosis may be present.
A diastolic thrill at the apex is unusual.
Heart sounds
Loud first heart sound, opening snap, and a mitral early-to-mid diastolic murmur are the classic auscultatory findings of mitral stenosis and are variably present.
Reduced transmitral pressure gradient resulting from decompression of the left atrium through the ASD and displacement of the left ventricular apex due to a large right ventricle attenuate these classic findings of mitral stenosis.
Development of pulmonary hypertension and, consequently, an increase in right atrial and left atrial pressures may increase transmitral pressure gradient and bring out these auscultatory findings, but this phenomenon is canceled by further dilatation of the right ventricle, thus obscuring the left ventricular apex.
The second heart sound (S2) may be widely split for 2 reasons. Increased right heart flow of ASD can result in late closure of the pulmonary component of the S2, and decreased left ventricular and aortic flow, secondary to mitral stenosis and ASD, can cause early closure of the aortic component of S2.
Additional heart sounds and murmurs
Third and fourth heart sounds of right ventricular origin may be audible at the left sternal border and are louder with inspiration.
Systolic murmurs are due to the following:
ASD along the upper left parasternal area - Typically a flow murmur due to increased flow across the pulmonic valve
Tricuspid regurgitation along the lower left parasternal area - Due to the displaced tricuspid valve secondary to right ventricular dilatation; common
Holosystolic murmur at the left parasternal area due to tricuspid regurgitation - Usually increases with inspiration (Carvallo sign), which differentiates it from ASD and mitral regurgitation
Mid diastolic murmurs are due to the following:
Increased flow across the tricuspid valve due to ASD or accompanying tricuspid stenosis, best heard at left lower sternal border or at apex for reasons already mentioned
Mitral stenosis, best heard with stethoscope bell at apex after exercise and with patient in left lateral position
Continuous murmur in the lower right sternal area is due to continuous shunting of blood across a small ASD in the presence of severe mitral stenosis. This is an unusual finding on physical examination.
Abdomen: Ascites and hepatomegaly may be noted in the presence of right heart failure.
Extremities: Ankle edema may be present in the presence of right-sided heart failure.

Causes
Mitral stenosis is mostly rheumatic in origin.
Congenital mitral stenosis is very rare.
ASD is either congenital or iatrogenic.

http://emedicine.medscape.com/article/162312-overview