Papillary Muscle Insertion Directly into the Anterior Mitral Leaflet in HypertrophicCardiomyopathy, Its Identification and Cause of Outflow Obstruction by Cardiac

Magnetic Resonance Imaging, and Its Surgical Management

Ethan J. Rowin, MDa, Barry J. Maron, MDb, John R. Lesser, MDb, Hassan Rastegar, MDa,and Martin S. Maron, MDa,*

This case presents an uncommon but important mechanism of muscular left ventricular

aHypertrophicMedical Center, Bmyopathy Center,Minnesota. Manureceived and acce

See page 1678*CorrespondinE-mail addres

0002-9149/13/$ -http://dx.doi.org/1

outflow obstruction in hypertrophic cardiomyopathy due to anomalous and direct papillarymuscle insertion into the anterior mitral leaflet, a finding reliably identified clinically bycardiac magnetic resonance imaging. The identification of this left ventricular outflow tractmorphology is important before invasive ventricular septal reduction therapy because itdictates a specific surgical strategy. These findings further support the role of cardiacmagnetic resonance imaging in the early evaluation of hypertrophic cardiomyopathypatients. � 2013 Elsevier Inc. All rights reserved. (Am J Cardiol 2013;111:1677e1679)

Anomalous and direct papillary muscle insertion intoanterior mitral leaflet is an uncommon but importantmechanism of muscular left ventricular (LV) outflow tractobstruction in hypertrophic cardiomyopathy (HC), leadingto progressive heart failure symptoms.1 Recognition of thisunique structural anomaly before invasive ventricular septalreduction therapy is crucial because it dictates a specificsurgical approach for septal myectomy with a deep,extended muscular resection well beyond the contact pointof the mitral valve and ventricular septum.2,3 Alcohol septalablation is unlikely to be effective in relieving LV outflowobstruction in patients with this anomaly,4 given that thepercutaneous procedure is inflexible with the operator isconfined to the fixed anatomic distribution of the first majorseptal perforator coronary artery. For this vignette, westudied 575 consecutive HC patients with cardiac magneticresonance imaging (CMR) presenting to 2 major HCcenters: 14 patients (2.4%) were identified with anomalousanterolateral papillary muscle insertion directly into anteriormitral leaflet (Figure 1). In 13 of the 14 patients, outflowgradients of 30 to 150 mm Hg were present at rest; 4 ofthese patients underwent successful surgical myectomy withrelief of obstruction and symptoms (including the patientpresented here). Preoperative identification of this morpho-logic abnormality by CMR altered surgical myectomystrategy to include an extended septal resection as well asreduction in papillary muscle thickness.

Case Report

A 52-year-old man with obstructive HC and progressiveheart failure was referred for invasive septal reduction

Cardiomyopathy Center, Division of Cardiology, Tuftsoston, Massachusetts; and bThe Hypertrophic Cardio-Minneapolis Heart Institute Foundation, Minneapolis,

script received December 28, 2012; revised manuscriptpted January 24, 2013.for disclosure information.g author: Tel: (617) 636-8066; fax: (617) 636-7667.s: mmaron@tuftsmedicalcenter.org (M.S. Maron).

see front matter � 2013 Elsevier Inc. All rights reserved.0.1016/j.amjcard.2013.01.340

therapy to relieve outflow tract obstruction. He was diag-nosed with HC at age 42 (10 years earlier) after a pre-cordial systolic ejection murmur was heard on physicalexamination. Over the previous 2 years, he experiencedprogressive exertional dyspnea (New York Heart Associ-ation functional class III) refractory to medical therapywith beta blockers and disopyramide. At the time ofevaluation, a 2-dimmensional transthoracic echocardio-gram demonstrated asymmetric septal hypertrophy witha maximal LV wall thickness of 17 mm (in the basalseptum), mild systolic anterior motion (SAM) of theanterior mitral leaflet without septal contact (Figure 2), andpeak outflow gradient of 150 mm Hg. The absence of thetypical mechanism of subaortic obstruction in HC (i.e.,prolonged SAM-septal contact) triggered advancedimaging with CMR to further characterize the morphologyof the outflow tract.

CMR identified outflow obstruction due to anomalousanterolateral papillary muscle insertion directly into anteriormitral valve leaflet (in the apparent absence of chordaetendineae), forming a single rigid structure contacting theventricular septum in systole and resulting in an elongated12-mm area of muscular apposition causing impedance toblood flow and the large outflow gradient (Figure 2, onlinevideo supplement 2B).

On the basis of the mechanism of outflow obstructionidentified only by CMR, surgical ventricular septal myec-tomy was selected to relieve outflow obstruction (givenknown previous failure of percutaneous alcohol septalablation to relieve obstruction in patients with thisanomaly).4 The surgical septal myectomy was performed atTufts Medical Center by one of the authors (HR) witha deep, extended muscular resection beyond the contactpoint of the papillary muscle and ventricular septum, as wellas a longitudinal partial resection of papillary muscle toreduce its thickness (Figure 2).

At the 6-month postoperative follow-up visit, the patientreported virtually complete resolution of heart failuresymptoms (New York Heart Association functional class I).Echocardiography demonstrated absence of obstructionwith normal outflow velocity (1.5 m/s at rest). CMR

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Figure 2. Septal myectomy for muscular mid-cavity obstruction. (A)Transthoracic 2-dimensional echocardiogram (apical 5-chamber view inmid-systole) from a 52-year-old man with HC and New York HeartAssociation functional class III symptoms demonstrates SAM of themitral valve without septal contact (arrow) but a peak systolic gradientof 150 mm Hg. (B) In the same patient, CMR LV outflow tract view inmid-systole demonstrates anomalous anterolateral papillary muscle(arrows) inserting directly into anterior mitral leaflet (small arrow-heads), forming a single rigid structure contacting the ventricular septum(large arrowheads) and creating a long 12-mm area of muscular outflowobstruction. (C) Surgical septal myectomy was performed and includeddeep, extended muscular resection (i.e., beyond the contact point of thepapillary muscle and ventricular septum, in the area demarcated bydotted line 1); removal of an accessory LV muscle bundle judged ascontributing to outflow obstruction because of its proximity to theanomalous papillary muscle during systole (area within dotted line 2);longitudinal partial resection of anterolateral papillary muscle was alsoperformed to reduce its thickness (area within dotted line 3); and addi-tional resection performed at the base of the papillary muscle (asterisk)to allow increased mobility of the papillary muscle away from theoutflow area during systole. (D) CMR LV outflow tract view in mid-systole obtained 6 months after surgical myectomy demonstratingwidening of the LV outflow tract diameter and absence of systoliccontact between papillary muscle (arrows) and septum, which resultedin complete elimination of outflow gradients. Ao: aorta; LA: left atrium;VS: ventricular septum.

Figure 1. CMR 3-chamber long-axis images (A) at end-diastole and (B) atmid-systole showing anomalous insertion of anterolateral papillary muscledirectly into anterior mitral leaflet in 2 patients with obstructive HC. (A) A42-year-old man with anterolateral papillary muscle (arrows; dotted linesrepresent continuation of papillary muscle, which extends out of theimaging plane) inserting directly into anterior leaflet of the mitral valve(arrowheads). (B) A 60-year-old man with relatively mild heart failuresymptoms due to mid-systolic apposition (large arrowheads) of ventricularseptum and anomalous papillary muscle (arrows) inserting into anteriormitral leaflet (small arrowheads). Ao ¼ Aorta; LA ¼ left atrium; VS ¼ventricular septum.

1678 The American Journal of Cardiology (www.ajconline.org)

demonstrated widening of the LV outflow tract area andabsence of systolic contact between the anomalous papillarymuscle and ventricular septum (Figure 2, online videosupplement 2D).

Discussion

In this case, preoperative identification of anomalousanterolateral papillary muscle insertion directly into ante-rior mitral leaflet by CMR altered surgical myectomystrategy to include an extended septal resection as well asreduction in papillary muscle thickness. Although thisanomaly can be detected using 2-dimensional echocardi-ography, our case demonstrates that the portion of papil-lary muscle inserting into the mitral leaflet will not alwaysbe in the long-axis imaging plane and therefore is notreliably visualized with 2-dimensional echocardiography.

Unique imaging strengths of CMR, including the oppor-tunity to acquire stacked contiguous tomographic imagesthrough the LV chamber, reliably identified this importantstructural anomaly evident in a subgroup of HC patients(Figure 3).

Disclosures

The authors have no conflicts of interest to disclose.

Supplementary Data

Supplementary data related to this article can be foundonline at http://dx.doi.org/10.1016/j.amjcard.2013.01.340

Figure 3. Anomalous papillary muscle visualized by CMR but not detected by 2-dimensional echocardiography. (A) End-diastolic apical 3-chamber2- dimensional echocardiographic images from an asymptomatic 50-year-old man showing only mild systolic anterior motion of the mitral valve. (B) In thesame patient, standard end-diastolic CMR 3-chamber long-axis image at virtually the identical cross-sectional imaging plane as that of the echocardiogramin panel A. In neither panel A nor B is the anomalous papillary muscle evident. (C) Additional end-diastolic long-axis stack image anterior to andcontiguous with that in panel B, demonstrating the anterolateral papillary muscle (arrows) inserting directly into anterior mitral leaflet (arrowheads; dottedlines represents continuation of the papillary muscle distally out of the imaging plane). (D) Midventricular short-axis CMR image in the same patient withbroken dashed lines indicating orientation of the stacked long-axis cross-sectional images shown in panels B and C. Ao ¼ aorta; LA ¼ left atrium; LV ¼ leftventricle; VS ¼ ventricular septum.

Case Report/Implications of Anomalous Papillary Muscle Insertion in HCM Identified by CMR 1679

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