Percutaneous Balloon Dilation of Discrete Subaortic Stenosis: A Futile Exercise

J INVASIVE CARDIOL 2017;29(9):E107-E108.

Key words: subaortic membrane, discrete subaortic stenosis, balloon dilation

Discrete subaortic stenosis (DSS) is a progressive obstruction of left ventricular outflow tract (LVOT) resulting in the development of aortic regurgitation in its natural course. Hence, early intervention is recommended.¹ Surgery is the primary treatment and involves a circumferential resection of the fibrous ring and parts of the muscular base along the left septal surface. Surgical results are good, but restenosis may occur.² Percutaneous balloon dilation has been attempted in a few cases with variable results.

A 30-year-old male presented with gradually progressive dyspnea and chest pain of 3-year duration. Two-dimensional echocardiogram confirmed the presence of a discrete subaortic membrane (2.5 mm thick) located 8 mm below the aortic valve (Figure 1A; Video 1). Pulsed and continuous-wave Doppler interrogation revealed a peak systolic gradient of 93 mm Hg across the membrane (Figure 1B) with trivial aortic regurgitation. 

Left ventricular angiography showed discrete thick subaortic membrane forming a triangular chamber just below the aortic valve (Figure 2A; Video 2); therefore, balloon dilation was planned. Baseline gradient across the membrane was 118 mm Hg and aortic annulus measured 24 mm. The first attempt to dilate the membrane failed due to insufficient length of coiled wire and Inoue balloon. The membrane was then crossed with a Terumo wire, which was exchanged with an Amplatzer extra-stiff wire. The membrane was dilated with an 18 x 40 mm NuMed Tyshak balloon (B. Braun) (Figure 2B; Video 3). Following the first inflation, the residual systolic gradient across the LVOT was 80 mm Hg, so subsequent dilation was done with a 22 x 40 mm NuMed Tyshak balloon. Residual LVOT gradient after two dilations was 5 mm Hg. There was no evidence of aortic regurgitation. Repeat transthoracic echocardiography at 24 hours showed recurrence of severe LVOT gradient. There was no aortic regurgitation. However there was grade 2-3 mitral regurgitation (Figure 3; Video 4) secondary to chordal rupture. Surgical membrane resection and repair of ruptured chordae were advised.

Percutaneous balloon dilation of DSS has been reported and can substantially reduce LVOT pressure gradient. The results indicate that transluminal balloon dilation can be a safe, effective treatment for thin subaortic membrane with polyethylene fixed-size balloons^3-5 or Inoue balloon.⁶ Inoue balloon failed in our patient; hence, the subaortic membrane was serially dilated with fixed-size balloons. Although the residual gradient was negligible after balloon dilation, it reappeared within 12 hours.

 Percutaneous balloon dilation can cause papillary muscle rupture, resulting in severe mitral regurgitation and pulmonary edema.⁷ In our patient, the balloon dilation caused rupture of chordae, resulting in grade 2-3 mitral regurgitation. The relief of subaortic stenosis was transient and the initial result could be due to stretching of subaortic membrane, which recoiled later resulting in recurrence of stenosis.

The response to balloon dilation of DSS is transient and may complicate with chordal or papillary muscle rupture. Hence, balloon dilation of DSS should be discouraged.

References

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3.    Lababidi Z, Weinhaus L, Stoekle H Jr, Walls JT. Transluminal balloon dilatation for discrete subaortic stenosis. Am J Cardiol. 1987;59:423-424.

4.    Arora R, Goel PK, Lochan R, Mohan JC, Khalilullah M. Percutaneous transluminal balloon dilatation in discrete subaortic stenosis. Am Heart J. 1988;116:1091-1092.

5.    Sharma S, Bhagwat AR, Loya YS. Transitional balloon dilatation for discrete subaortic stenosis in adults and children: early and intermediate results. J Intervent Cardiol. 1991;4:105-109.

6.    Bahl VK, Bhargava B, Chandra S. Percutaneous balloon dilatation of subaortic membrane using an Inoue balloon. Int J Cardiol. 1996;54:81-84.

7.    Frutos A, Sobrino N, Gallego P, et al. Papillary muscle rupture during subaortic membrane balloon dilatation. Rev Esp Cardiol. 1996;49:146-148.

From the Department of Cardiology, Sri Jayadeva Institute of Cardiovascular Sciences and Research, Bangalore, India.

Disclosure: The authors have completed and returned the ICMJE Form for Disclosure of Potential Conflicts of Interest. The authors report no conflicts of interest regarding the content herein.

Manuscript accepted January 11, 2017.

Address for correspondence: Nagaraja Moorthy, MD, DM, Department of Cardiology, Sri Jayadeva Institute of Cardiovascular Sciences and Research, Bangalore, India 560069. Email: drnagaraj_moorthy@yahoo.com