Sudden Cardiac Death Due to an Anomalous Posterior Papillary Muscle

CASE REPORT

Sudden Cardiac Death Due to an Anomalous Posterior Papillary Muscle Francesca Cittadini, MD, PhD,* Antonio Oliva, MD, PhD,* Vincenzo Arena, MD,† Natalia Minelli, MD,* and Vincenzo L. Pascali, MD, PhD*

Abstract: Anomalies of the mitral subvalvular apparatus can include differing types of papillary muscles and chordae tendinae. Direct insertion of the anomalous papillary muscle or chordae tendinea into the anterior mitral leaflet and fusion to the ventricular septum are common findings related to these anomalies. Anomalous papillary muscles or chordae, especially those that insert directly into the mitral leaflets, play a role in obstructing left ventricular outflow by restricting the mobility of the leaflets and/or tethering them toward the septum, thus narrowing the left ventricular outflow tract (LVOT). The incidence of mitral valve anomalies associated with LVOT is probably underestimated. This topic is frequently studied, however, especially in the pediatric cardiac surgery milieu, because LVOT obstruction could have a surgical solution. We report a case of an 18-year-old woman affected by epilepsy since 5 months of age who was found dead in her bedroom. An uncommon anomalous papillary muscle/chordae was the main autopsy finding. This malformation causes direct continuity between an accessory papillary muscle and a mitral leaflet, resulting in a long rigid area that can cause dynamic late-systolic intraleft-ventricular obstruction. In our case, in the absence of any other pathologic findings or major structural abnormalities, we speculate that a malignant cardiac arrhythmia provoked by the accessory papillary muscle could be the cause of death. Key Words: sudden death, anomalies of mitral subvalvular apparatus, left ventricular outflow obstruction (Am J Forensic Med Pathol 2010;31: 000 – 000)

C

ardiac anomalies have been extensively investigated since they are among the most frequent causes of sudden death. Dynamic left ventricular outflow tract (LVOT) obstruction caused by anomalous insertion of the papillary muscle (PM) or chordae tendinae into left ventricular structures are particulary well studied. Anomalies of the mitral subvalvular apparatus include differing types of PMs and chordae tendinae. Direct insertion of the PM or chordae tendinae into the anterior mitral leaflet and fusion of the PM or chordae tendinae to the ventricular septum are common findings related to these anomalies. Reports of anomalous PMs have also included other presentations, such as a single PM with a parachute mitral valve1,2 Shone’s anomaly2 with an associated parachute mitral valve and aortic stenosis or coarctation and an anomalous PM associated with hypertrophic cardiomyopathy (HCM) that inserts directly into the base of the anterior mitral valve leaflet.3,4 Anomalous PMs or chordae, especially those that insert directly into the mitral leaflets, play a role in obstructing left

Manuscript received January 23, 2009; accepted August 5, 2009. From the *Institute of Forensic Medicine, and †Institute of Pathology, Catholic University, School of Medicine, Rome, Italy. Reprints: Francesca Cittadini, MD, PhD, Institute of Forensic Medicine, Catholic University, School of Medicine, Rome, Italy. E-mail: francesca.cittadini@rm. unicatt.it. Copyright © 2010 by Lippincott Williams & Wilkins ISSN: 0195-7910/10/3102-0001 DOI: 10.1097/PAF.0b013e3181d3ca7e

Am J Forensic Med Pathol • Volume 31, Number 2, June 2010

ventricular outflow by restricting the mobility of the leaflets and/or tethering them toward the septum, thus narrowing the LVOT.1,3 Anomalous insertion of a PM into the anterior mitral leaflet represents a mechanism of obstruction to left ventricular outflow in patients with HCM, and differs considerably from the typical dynamic obstruction caused by mitral valve systolic anterior motion that occurs in many other patients with HCM. Recognition of this malformation emphasizes the diverse morphologic expression of HCM, and also has important clinical implications for patients requiring an operation because the gradient is likely to persist even after adequate myotomy/myectomy. Consequently, mitral valve replacement would appear to be the operation of choice in the majority of such patients. Here we report a case of sudden death in an 18-year-old woman affected by epilepsy. An uncommon anomalous PM/chordae was the main autopsy finding, and therefore we hypothesized that a malignant cardiac arrhythmia provoked by an anomalous insertion of the PM was the cause of death.

CASE REPORT An uncommon anomalous PM/chordae was the main finding in an 18-year-old woman found dead in her bedroom, who had been affected by epilepsy since she was 5 months of age. She had a clinical history of mild mental retardation and nonspecific symptoms such as precordial palpitations, asthenia, vertigo, and a 2/6 systolic murmur heard at the cardiac apex. Syncopal episodes were also reported. She did not have a family history of cardiovascular disease. The earlier syncopal episodes occurred several years before her death, during infancy, and they were presumably attributed to the seizures and were not further investigated. An electrocardiogram taken some years before revealed a sinus rhythm with normal voltage; no echocardiogram was reported. We did not receive scene findings of note. At the time of death, the woman had been taking valproic acid and lamotrigine for her seizures. Toxicological analysis revealed therapeutic levels of these drugs in her peripheral blood. Postmortem toxicology screening excluded a toxic cause of death. However, vitreous was not analyzed. A complete autopsy was performed and at the external examination any tongue bites were observed. Gross examination of the heart and coronary arteries was unremarkable, heart weight was 260 g. Interestingly, the only finding during cardiac examination was an anomalous posterior PM consisting of 3 different fascicles of unequal size. The thinnest one was attached to the ventricular face of the mitral valve cusps by the chordae tendinae. Moreover, this auxiliary branch of the posterior PM was also connected to the heart apex by thin muscular trabeculae (Fig. 1). At gross examination, the left ventricular wall demonstrated deep recesses that were most prominent toward the apex, suggesting a partial ventricular noncompaction5 (Fig. 2). Histologic examination of left ventricular myocardium revealed irregular myocardial hypertrophy and occasional vacuolar degeneration. Focal endocardial fibrosis was also noted. The brain showed a bland swelling of convexities, but no other macroscopic abnormalities were found. Histopathological examination of the brain excluded significant pathology. www.amjforensicmedicine.com | 1

Am J Forensic Med Pathol • Volume 31, Number 2, June 2010

Cittadini et al

FIGURE 1. A, Section of the heart showing the left ventricle with a posterior PM composed of 3 different branches of unequal size. B, The thinnest branch is attached to the trabeculae carneae of the heart apex and to the ventricular face cusps of the mitral valve by the chordae tendinae.

FIGURE 2. Gross examination of the ventricular apex demonstrating myocardial recesses with interlacing small muscle bundles that form irregular branching at the endocardial surface.

DISCUSSION The incidence of mitral valve anomalies associated with LVOT is probably underestimated. The topic is frequently studied, however, in the pediatric cardiac surgery milieu, as LVOT obstruction could have a surgical solution. Such anomalies are grouped into 5 categories: insertion of a PM into the aortic leaflet, insertion of a PM into the ventricular wall, “muscularization” of the subaortic portion of the aortic leaflet, anomalous insertion of the valvular tissue into the ventricular wall, and accessory valvular tissue.6 PM anomalies accompany LV hypertrophies of various etiologies and may play a significant role in producing dynamic late-systolic intra-LV obstruction in HCM and other hyperdynamic hypertrophied LV chambers.7 Multiple modifications in the anatomy of the mitral valvular apparatus can lead to complex effects besides LVOT obstruction, such as left ventricular inlet and outlet obstruction.8 Most of the previous studies have reported that malformations with direct continuity between an anomalous PM and a mitral valve leaflet result in a long rigid area of midcavity narrowing that appears to be solely or largely responsible for the outflow obstruction.3,9 In our case, the anomalous PM, producing modifications in the anatomy of the mitral valvular apparatus, could be responsible of 2/6 2 | www.amjforensicmedicine.com

systolic murmur at the cardiac apex reported in the clinical history of the woman. The LVOT obstruction produced by an anomalous PM can gradually produce left ventricular hypertrophy and, after a long subclinical period, the obstruction can become severe enough to cause syncopal attacks.4 In fact, the LVOT obstruction can occur during the early period of life as or it can develop gradually due to continued deposition of fibrous tissue within the LVOT. Thus, clinical signs can appear even in older patients.10 Klues et al related anomalous insertion of PMs to obstructive HCM,3 reporting that 10 of 78 (13%) mitral valve specimens from patients with obstructive HCM showed direct insertion of one or both left ventricular PMs into the anterior mitral leaflet. In the present case, histologic examination was not characteristic of HCM, and thus we consider the etiology of the LVOT obstruction to be the anomalous insertion of the accessory PM. The intraleft ventricular hypertension from the Venturi effect11 then caused secondary bland myocardial hypertrophy. It is readily apparent in the present case that the chordae tendinae were inserted on the undersurface of the anterior mitral leaflet. This finding is the most plausible cause of the severe left ventricular outflow obstruction, as confirmed by the patient’s clinical history of a systolic murmur at the cardiac apex, suggesting a mild degree of obstruction. Finally, we believe that in our case, the anomalous insertion of the accessory PM caused a LVOT obstruction producing a secondary bland myocardial hypertrophy, observed at the autopsy. Recent remarkable advances have occurred in our understanding of the pathophysiology of syncope and ventricular tachyarrhythmias or bradyarrhythmias in HCM12 and in LV obstruction.13,14 In the current case, in light of our findings, we believe that a malignant cardiac arrhythmia is a possible explanation for the patient’s death, in the absence of any other pathologic findings or major structural abnormalities, although seizure cannot be ruled out on the basis of grossly and/or microscopically. In conclusion, we believe that clinicians and forensic pathologists should be aware of this entity both for a more detailed pathologic and anatomic studies of anomalous insertion classification and for differential diagnoses. REFERENCES 1. Draulans-Noc HA, Wenink AC, Quaegebeur J. Single papillary muscle (“parachute valve”) and double-orifice left ventricle in atrioventricular septal defect convergence of chordal attachment: surgical anatomy and results of surgery. Pediatr Cardiol. 1990;11:29 –35.

© 2010 Lippincott Williams & Wilkins

Am J Forensic Med Pathol • Volume 31, Number 2, June 2010

2. Prunier F, Furber AP, Laporte J, et al. Discovery of a parachute mitral valve complex (Shone’s anomaly) in a adult. Echocardiography. 2001;18:179 –182. 3. Klues HG, Roberts WC, Maron BJ. Anomalous insertion of papillary muscle directly into anterior mitral leaflet in hypertrophic cardiomyopathy; significance in producing left ventricular outflow obstruction. Circulation. 1991;84:1188–1197. 4. Nomura T, Harada Y, Suzaki Y, et al. Left ventricular outflow tract obstruction due to anomalous insertion of papillary muscle. Circ J. 2004;68:1219–1222. 5. Burke A, Mont E, Kutys R, et al. Left ventricular noncompaction: a pathological study of 14 cases. Hum Pathol. 2005;36:403– 411. 6. Cohen L, Bennani R, Hulin S, et al. Mitral valvar anomalies and discrete subaortic stenosis. Cardiol Young. 2002;12:138 –146. 7. Madu EC, D’Cruz IA. The vital role of papillary muscles in mitral and ventricular function: echocardiographic insights. Clin Cardiol. 1997;20:93–98. 8. Albertucci M, Lang RM, Karp RB, et al. Double-chambered left ventricle: submitral accessory valvular tissue causing inlet and outlet obstruction. J Am Soc Echocardiogr. 1994;7:67–71.

© 2010 Lippincott Williams & Wilkins

Cardiac Death Due to Papillary Muscle

9. Klues HG, Maron BJ, Dollar Al, et al. Diversity of structural mitral valve alterations in hypertrophic cardiomyopathy. Circulation. 1992;85:1651–1660. 10. Uslu N, Gorgulu S, Yildirim A, et al. Accessory mitral valve tissue: report of two asymptomatic cases. Cardiology. 2006;105:155–157. 11. Roldan CA, Gurule FT, Shively BK. Anomalous papillary muscle producing dynamic left ventricular outflow tract obstruction. J Am Soc Echocardiogr. 1991;4:267–270. 12. Schiavone WA, Maloney JD, Lever HM, et al. Electrophysiologic studies of patients with hypertrophic cardiomyopathy with syncope of undetermined etiology. Pacing Clin Electrophysiol. 1986;9:476 – 481. 13. Douglas WE, Harry R, Brian PK, et al. Hypertrophic cardiomyopathy: clinical spectrum and treatment. Circulation. 1995;92:1680 –1692. 14. McAreavey D, Dilsizian V, Panza J, et al. Favorable prognosis in 88 young hypertrophic cardiomyopathy patients during therapy based on hemodynamic electrophysiologic and thallium scintigraphy findings. Circulation. 1993; 88(suppl I):I–209.

www.amjforensicmedicine.com | 3