Lutembacher Syndrome

Etiology

Both the lesions in LS can be congenital or acquired. The incidence rate of congenital ASD in patients with MS is 0.6% to 0.7%. As the number of patients having MS undergoing trans-catheter BMV is increasing, the incidence of residual ASD is increasing resulting in a greater number of patients with iatrogenic LS. Congenital MS is a very rare entity accounting for only 0.6% of congenital heart disease. Mitral stenosis in LS is invariably due to RHD. Assuming a relatively uniform incidence of ASD worldwide, the incidence of co-existing rheumatic MS depends on the geographic prevalence of RHD.[4]

Epidemiology

The exact prevalence of LS is not known.[5] It is more likely to prevalent in areas with higher prevalence of rheumatic heart disease (RHD). For this reason, it is reported more often in Southeast Asia. Furthermore, in such developing countries, a history of rheumatic fever has been reported in 40% of patients with LS. The syndrome can present at any age but usually more common in young adults. There is a predilection for females because ASD and rheumatic MS are both more prevalent in females.

Pathophysiology

The hemodynamic effects of this syndrome are the result of the interplay between the relative effects of ASD and MS. The hemodynamic features and the natural history of the patients depend upon the size of the ASD, severity of MS, compliance of the right ventricle and the degree of pulmonary vascular resistance. When MS is severe, and ASD is non-restrictive, left atrium (LA) finds another exit through the septum in addition to the mitral valve (LA decompression). Therefore, LA pressure does not rise in proportion to the severity of MS. For this reason, pulmonary venous hypertension takes a long time to develop. However, this results in an increased left to right shunt across the ASD and progressive dilatation of right atrium (RA) and right ventricle (RV) with increased pulmonary blood flow. In untreated cases, the pulmonary vascular resistance continues to increase which eventually leads to right ventricular failure. The pulmonary artery hypertension (PAH) in these patients is usually hyperkinetic (because of increased left to right shunt) in comparison to patients with isolated severe MS where it develops due to direct back pressure transmission, reactive pulmonary vasoconstriction and obliterative changes in pulmonary arterioles. There occurs a reciprocal decrease in the left ventricular filling and stroke volume. In contrast, if the ASD is restrictive, the shunt across the defect will be less, and hence, the patient will follow the course of isolated MS.

In contrast to an isolated ASD, the susceptibility to infective endocarditis is increased by the presence of MS. However, the calcification of mitral valve is less common in LS, as there occurs decompression of LA, resulting in less turbulent flow across the mitral valve. Atrial dilatation in LS predisposes the patients to develop atrial fibrillation.

History and Physical

LS is well tolerated by patients for a long time because the blood is shunted through ASD to the Right Atrium. Symptoms of pulmonary venous hypertension, for example, hemoptysis, paroxysmal nocturnal dyspnea, and orthopnea are less frequent due to LA decompression. However, these symptoms are more common in patients with small ASD. The symptoms like palpitation and fatigability appear early in patients with LS due to the increased left to right shunt and decreased systemic cardiac output.

Presence of both ASD and MS, modify each other’s signs on physical examination. Since the LA and RA function as a common chamber in a non-restrictive ASD, jugular venous pressure (JVP) is raised without congestive heart failure, and ‘a’ waves in JVP are prominent in the absence of PAH. The pulse may be low volume because of reduced left ventricle stroke volume. The precordial examination may reveal a prominent left parasternal heave and a systolic thrill over the left upper parasternal area in patients with LS with a large ASD in comparison to an uncomplicated ASD because MS augments left to right shunt. The apex may be diffuse if the dilated RV occupies the apex instead of the left ventricle. The characteristic signs of MS on auscultation like loud first heart sound, opening snap, and a mid-diastolic rumbling murmur, are difficult to appreciate in patients with LS and may be missed. This is because the gradient across the mitral valve is not high because of LA decompression through ASD. Secondly, since the RV is enlarged and occupies the apex, the signs of LV inflow disease are less audible. On the contrary, the signs of large ASD like a fixed and wide split second heart sound and ejection mid-systolic murmur over the left upper parasternal region are more prominent. Holosystolic murmur due to tricuspid regurgitation (as a result of dilated RV) may be heard at the left parasternal area and may get transmitted to the apex as the RV is dilated. Increased intensity of this murmur with inspiration (Carvallo’s sign) differentiates this murmur from the murmur of MR.

Evaluation

The specific electrocardiographic (ECG) findings are tall and peaked P waves in the leads II, III, and avF and a deep prolonged terminal negative deflection of P wave in the lead V1, suggestive of biatrial enlargement. QRS shows right axis deviation, right ventricular hypertrophy (RVH), and complete or incomplete right bundle branch block. RVH and atrial fibrillation are disproportionately more common in LS when compared to an isolated ASD. Chest x-rays reveal enlarged RA, RV and main pulmonary artery with increased end-on pulmonary vascular markings suggesting increased left to right shunt. Pulmonary venous congestion is usually absent unless the ASD is restrictive. Two-dimensional echocardiography with color flow Doppler establishes the diagnosis of LS. [6]The severity of MS and the size and type of ASD are accurately estimated. Gradient across the mitral valve is less despite severe MS. Doppler pressure half-time usually overestimates the mitral valve orifice area because the ASD decompresses the LA and thus decreases the transmitral gradient. Planimetry is the more reliable method to assess the severity of MS in patients with LS. Transesophageal echocardiography outlines the site and size of ASD with its flow pattern. Cardiac catheterization is seldom required to make the diagnosis of LS in the current era. Physicians are sometimes required to assess the reversibility of PAH, measure the mitral valve area, and evaluate the coronary anatomy in high-risk patients.

Treatment / Management

Symptomatic treatment is done with diuretics to relieve the symptoms of right-sided heart failure or pulmonary venous congestion if present. Beta-blockers and calcium channel blockers are prescribed for rate control in atrial fibrillation. Prophylaxis for infective endocarditis is recommended.

Traditionally the gold-standard treatment has been open heart surgery. However, with the advancement of percutaneous interventional techniques, hardware, and more expertise, percutaneous transcatheter therapy in the form of BMV for MS and subsequently device closure for ASD, has become the preferred choice of treatment.[7][8] Surgical management is limited to large ASD not amenable to percutaneous device closure or MS which is not suitable for balloon mitral valvuloplasty (BMV).(B3)

Differential Diagnosis

ASD

Complications

Eisenmenger Syndrome