Written informed consent was obtained from the patient for publication of this case report and any accompanying images. A 70-year-old man was scheduled for mitral valve (MV) replacement for severe mitral regurgitation (MR). Preoperative 2-dimensional (2D) transthoracic echocardiography revealed severe MR with bilaterally thickened leaflets, and a parachute MV (PMV) was suspected because the attachment of the mitral chords seemed to be unifocal, attaching to a single large papillary muscle (PM). Mitral stenosis (MS) was absent, as seen by the pressure half-time of 110 milliseconds and mean pressure gradient of 4 mm Hg.
Intraoperative transesophageal echocardiography (TEE) was performed using a 3-dimensional (3D) echocardiographic matrix-array probe (X7-2t transducer, Philips Healthcare, Andover, MA). The midesophageal (ME) 4-chamber view demonstrated a prominent PM extending toward the mitral annulus, with shortened chords attached to each thickened and slightly tethered MV leaflet (Figure 1A; Supplemental Digital Content 1, first part of Video 1, http://links.lww.com/AA/B437). Color flow Doppler analysis revealed a central jet of severe MR through the opening of both leaflet tips in systole (Supplemental Digital Content 1, second part of Video 1, http://links.lww.com/AA/B437). The ME MV commissural view at 60° demonstrated a large anterolateral PM (scanned in the ME 4-chamber view) and a relatively small posteromedial PM with thickened and shortened chords (Figure 1B; Supplemental Digital Content1, third part of Video 1, http://links.lww.com/AA/B437). Simultaneous orthogonal imaging at 150° revealed direct insertion of the large anterolateral PM to the anterior mitral leaflet (AML; Figure 1C; Supplemental Digital Content 1, third part of Video 1, http://links.lww.com/AA/B437). The transgastric (TG) midpapillary short-axis view revealed a prominent anterolateral PM (1.8 ×1.6 cm) and a relatively small-sized posteromedial PM (1.0 ×1.0 cm) with left ventricle (LV) hypertrophy (septal thickness: 1.8 cm at end-diastole; Figure 2A; Supplemental Digital Content 2, first part of Video 2, http://links.lww.com/AA/B438). By slightly withdrawing the probe, the area of transition from both the PMs to the mitral leaflets was scanned (Figure 2B; Supplemental Digital Content 2, second part of Video 2, http://links.lww.com/AA/B438). Further, by slightly withdrawing the probe and turning the multiplane angle to 35°, the TG basal short-axis view just below the mitral leaflet demonstrated the cross section of both PMs at that level (Figure 2C; Supplemental Digital Content 2, third part of Video 2, http://links.lww.com/AA/B438). Simultaneous orthogonal imaging based on the view shown in Figure 2B revealed a longitudinal plane of thickened and shortened chords attaching to both PMs, which in turn were extended toward the mitral annulus (Supplemental Digital Content 2, fourth part of Video 2, http://links.lww.com/AA/B438). Next, the 3D TEE view was scanned for further morphological evaluations. The live 3D zoom was scanned from a ME MV commissural view at 60° and manipulated to provide en face views of the MV from the left atrium (LA; Supplemental Digital Content 3, first part of Video 3, http://links.lww.com/AA/B439). A prominent anterolateral PM and a relatively small posteromedial PM were observed just below the thickened MV leaflets in diastole. For further investigation of the sub-MV apparatus, the 4 beat gated 3D zoom was scanned from a TG LV 2-chamber view at 90° and manipulated to provide en face views from the LV outflow tract perspective (Figure 3A; Supplemental Digital Content 3, second part of Video 3, http://links.lww.com/AA/B439) and septal perspective (Supplemental Digital Content 3, third part of Video 3, http://links.lww.com/AA/B439). This view simultaneously demonstrated an almost complete view of the MV apparatus, together with morphological characteristics of the MV and subvalvular apparatus, particularly the 2 PMs, both of which extended toward the mitral annulus, and the asymmetrically dominant distribution of the chords from the hypertrophied anterolateral PM (Figure 3A; Supplemental Digital Content 3, Video 3, http://links.lww.com/AA/B439). The results of surgical inspection and the resected specimen are displayed in Figure 3, B and C, these being consistent with the TEE views.
The MV and associated tissue, other than both PMs, were resected, as shown in Figure 3C, and replaced with a mechanical mitral prosthetic valve. Postcardiopulmonary bypass TEE assessment demonstrated normal mitral prosthetic valve function with good mobilization of both leaflets and normal LV inflow. The patient’s postoperative course was uneventful.
PMV is a rare congenital malformation of the mitral apparatus, characterized by unifocal attachment of the chords of both leaflets to a single or fused PM, resulting in subvalvular obstruction (MS).2 It is often diagnosed in infants and young children, usually as part of Shone complex, consisting of a PMV, supravalvular ring of the LA, subaortic stenosis, and coarctation of the aorta, or associated with other congenital anomalies, including atrial septal defect, ventricular septal defect, aortic valve stenosis, and LV hypoplasia, while isolated PMV also exists.2 Further, adult PMV is extremely rare and is generally associated with mild MS.2
Although a true PMV is identified by the presence of a single PM, the parachute-like asymmetrical MV is classified separately from PMV because of different morphogenetic development of the valvular apparatus and consists of 2 separate PMs, one of which extends toward the mitral annulus, and this reportedly being frequently observed in the anterolateral PM on autopsy.3,4 Further, the main morphological characteristics are unequal distribution of the chords, the majority of which attach to 1 dominant PM, whereas the other PM that extends toward the mitral annulus seems to be recessive, attaching to fewer or no chords.3,4 MS is also typical of a parachute-like asymmetrical MV and occurs because of obstruction by the parachute itself, commissural fusion, or an excess of valve tissue between the chords, whereas severe MR because of an anterior MV cleft has been reported in a parachute-like asymmetrical MV,5 suggesting possible variable lesions of the MV. The differences between true PMV and parachute-like asymmetrical MV are demonstrated in Table 1.
Transthoracic echocardiography and TEE are useful tools for diagnosing PMV.2 The echocardiographic characteristics of PMV include (1) a single centrally located PM, (2) funnel-shaped MV, (3) doming of the elongated chords in diastole, and (4) a pear-like shape of the LA.2 Conversely, in a parachute-like asymmetrical MV, a very prominent and thickened anterolateral PM and coincident anterior leaflet cleft and atrial septal defect were demonstrated by 2D TEE,5 although other echocardiographic features were not described.
In our case, an isolated lesion of the mitral apparatus with severe MR was demonstrated with intraoperative 2D and 3D TEE. ME views demonstrated 2 asymmetric PMs, both of which extended to the mitral annulus, with thickened and shortened chords, each attached to both the thickened mitral leaflets and pulled into the LV, indicating complex mechanisms of MR, while shadowing, and echo dropout partially affected visualization of the subvalvular tissue. Conversely, TG short-axis views showed the cross section of the mitral apparatus at each depth without artifacts. Also, TG 2-chamber views obtained from simultaneous orthogonal imaging clearly revealed subvalvular tissue because of the perpendicular incidence of the ultrasound. Further, 3D views of the mitral apparatus demonstrated all the morphologic characteristics in 1 plane, including both prominent and relatively small-sized PMs, extending toward the mitral annulus, appearing to be directly attached to the mitral leaflets in some parts, and continuous lesions of the thickened and agglutinated chords, which were asymmetrically attached to about two-thirds of the AML from the hypertrophied dominant anterolateral PM. These morphological changes were better seen with TG-based scanning. Abnormal tangled chords with obliterated interchordal spaces have also been demonstrated in a case of PMV,6 although in our case, more extreme changes were observed on surgical inspection and in the resected specimen (Figure 3, B and C). In this case, hypertrophy of the LV and 1 dominant PM were also seen, with an interventricular thickness of 1.8 cm at end-diastole and a PM diameter of >1.1 cm, defined as the upper limit of PM hypertrophy.1 Further, anomalous insertion of the hypertrophied PM directly onto the AML was seen, as previously described.7 Although it was not clear whether the dominant PM hypertrophy in our case was congenital or acquired, congenital asymmetrical distribution of the chords from the prominent hypertrophied anterolateral PM extending to the mitral leaflet level would suggest a diagnosis of parachute valve; however, the presence of 2 PMs precluded a diagnosis of “true PMV.” Conversely, the tip of the other relatively small-sized posteromedial PM would remain in the mitral leaflet level with congenitally underdeveloped and fewer chords. Therefore, the appropriate diagnosis of this mitral lesion would be parachute-like asymmetrical MV with hypertrophy of the LV and dominant PM. Intraoperative TEE depicted the abnormal appearance of the extremely denatured mitral complex, which not only suggested the probability of difficult repair using autologous MV apparatus because of the severely thickened degenerated leaflet itself and possible stenotic condition after ring annuloplasty because of the restricted subvalvular space with extreme paucity of interchordal spaces, prominent PMs, and tethered mitral leaflets but also directed attention toward the possibility of an immobilized leaflet because of excess subvalvular remnants after prosthetic valve replacement.6
In conclusion, detailed 2D and 3D TEE analyses complement each other in evaluating the morphologic features of a parachute-like asymmetrical MV with hypertrophy of the LV and a dominant PM. Three-dimensional TEE would be useful for complete understanding of the morphologic characteristics of the mitral complex.
Clinician’s Key Teaching Points
By Nikolaos J. Skubas, MD, Kimberly Howard-Quijano, Martin J. London, MD
- A parachute mitral valve (MV) is a rare congenital malformation characterized by attachment of the chordae tendineae to a single papillary muscle (PM) and a funnel-shaped MV orifice. It may be part of other congenital syndromes such as Shone complex and is commonly associated with mitral regurgitation or stenosis.
- A variant of this malformation is the parachute-like asymmetrical MV, with 2 PMs: a hypertrophic anterolateral PM, which usually extends toward the mitral annulus and is directly attached to the anterior mitral leaflet, and a smaller, hypotrophic posterior PM.
- In this case of an adult male with mitral regurgitation, a parachute MV was suspected, based on transthoracic echocardiography imaging. With intraoperative 2-dimensional transesophageal echocardiographic (TEE), a prominent and thickened anterolateral PM was imaged to directly attach to the anterior mitral leaflet (midesophageal and transgastric views with simultaneous orthogonal imaging). In the midesophageal mitral commissural and equivalent 3-dimensional TEE full-volume views, the 2 unequally sized PMs were imaged in a longitudinal perspective.
- Echocardiography can be used to diagnosis parachute MV, differentiate variants, and detect associated clinical sequelae. The abundance of subvalvular tissue in this congenital malformation may prohibit successful MV repair or complicate MV replacement surgery. Complimentary 2-dimensional and 3-dimensional TEE analyses provide a complete description of the MV complex and may aid in surgical management.
Name: Masataka Kuroda, MD, PhD.
Contribution: This author helped design, conduct and perform the study, analyze the data, and prepare the manuscript.
Name: Sohtaro Miyoshi, MD, PhD.
Contribution: This author helped analyze the data and prepare the manuscript.
Name: Shigeru Saito, MD, PhD.
Contribution: This author helped design the study and prepare the manuscript.
Name: Shingo Taguchi, MD, PhD.
Contribution: This author is the primary sugeon and helped analyze the data the prepare the manuscript.
This manuscript was handled by: Martin J. London, MD.
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