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Abnormally long papillary muscles of the human heart
ABNOR~'[ALLY L O N G P A P I L I J A R Y I\.IUSCLE~ OF T H E HUMAN HEART ~ WALLACE M. YATER,t M.D. ROCI~IESTER, ~ ' [ I N N .
R D I N A R I L Y the p a p i l l a r y muscle of the h u m a n h e a r t is a t t a c h e d to the valve leaflet b y a n u m b e r of fibrous ehordae tendineae which are ahnost as long as, or even longer than, the muscle. Occasionally, however, macroscopic muscle b a n d s extend u p w a r d into these cords and m a y even t r a v e r s e their whole length, or more rarely, the p a p i l l a r y muscle itself m a y replace several ehordae tendineae and be a t t a c h e d directly to the valve. In the l i t e r a t u r e I have been able to find only two references to such anomalies, although they must eertainly occur in the experience of every pathologist whose m a t e r i a l f r o m necropsies is a b u n d a n t , in 1896 P r z e w o s k i described f o u r eases. I n three cases the tip of the n o r m a l p a p i l l a r y muscle in the left ventricle was p r o l o n g e d into a thin extension which took the place of a cord. This f o r m of the a n o m a l y he did not consider altogether rare. He p r o n o u n c e d his f o u r t h ease to be more unusual; in this, a large a n t e r i o r p a p i l l a r y muscle sent out a large m u s c u l a r extension which entirely replaced several chordae tendineae a n d was inserted into the v e n t r i e u l a r surface of the m R r a l valve up to the fibrous ring. P r z e w o s k i laid down the criterion t h a t only the p a p i l l a r y muscles whose tip extended up to the valve should be considered a b n o r m a l l y long. In 1910 Ors6s-P6es described twelve cases of anomalies of this type and mentioned another. I n four of the described eases a cylindrical muscular b e a m f r o m the anterior p a p i l l a r y muscle was inserted iuto the posterior leaflet of the tricuspid valve up to the a t t a c h m e n t of the cusp. The lamella of insertion was relatively large. I n the other eig'ht eases m u s e u l a r beams f r o m the anterior p a p i l l a r y muscle of the left ventricle were inserted in the v e n t r i c u l a r surface of the a n t e r i o r leaflet of the m i t r a l valve. W h e n the muse!e bundle was inserted into the middle of the valve leaflet, the plate of insertion was s y m m e t r i c and t r i a n g u l a r . W h e n the bundle originated f r o m the r i g h t side of the a n t e r i o r p a p i l l a r y muscle, it fused with the corresponding p a r t of the a n t e r i o r cusp with a spade-shaped lamella of insertion which t u r n e d laterally and eventually connected with the v e n t r i c u l a r wall. Ors6s-Pdes explained the f a c t t h a t the lamella of insertion of these bundles in the r i g h t ventriele always ended at the a t t a c h e d edge of the v a l v e on the basis t h a t the venous orifice of the r i g h t ventricle
O
* W o r k done in t h e Section on P a t h o l o g i e A n a t o m y , T h e M a y o Clinic. t F e l l o w in Medicine, T h e 1Vfayo F o u n d a t i o n . 72
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e n t i r e l y b y m u s c l e , w h i l e in t h e l e f t v e n o u s orifice t h e
m u s c l e o v e r the a n t e r i o r v a l v u l a r cusp is m i s s i n g . One of his p a t i e n t s w a s t h e son of a n o t h e r p a t i e n t r e p o r t e d , a c i r c u m s t a n e e w h i c h a r g u e d t h a t t h e a n l a g e m i g h t be h e r e d i t a r y . I n one case t h e r e was a calcified p l a q u e a t the p o i n t of i n s e r t i o n a n d in a n o t h e r on t h e a u r i c u l a r side of t h e p o i n t of i n s e r t i o n of t h e m u s c l e b u n d l e w a s a s u b e n d o c a r d i a l tubercle. Ors6s-P~es t h o u g h t t h e s e f e a t u r e s c o u l d be e x p l a i n e d b y t h e s t r e s s of a b n o r m a l p u l l of t h e m u s c l e . I h a v e f o u n d five eases of a n o m a l i e s of t h i s t y p e .
These occurred
in a b o u t 550 n e e r o p s i e s , a n i n c i d e n c e of 0.91 p e r cent.
Fig. l.--(Case I) Left anterior papillary muscle is inserted directly into the anterior cusp of the mitral valve just beneath the noncoronary cusp of the aortic valve.
REPORT OF CASES CASE 1.--The subject was a man, aged sixty years, who died from uremia following an acute exacerbation of ehroaie pyelonephritis. The systolic blood pressure was 220 mm. and the diastolic, 110 ram. The heart weighed 476 gin. (body weight, 61.4 kg., or 135 pounds). There was coronary sclerosis graded 2. With the exception of moderate hypertrophy, moderate coronary sclerosis and the anomaly, the heart appeared normal. The anterior papillary muscle of the left ventricle was 5.0 cm. long on its free inner surface and 2.5 cm. long on its mural surface (Fig. 1). It was 1.6 cm. broad at its base, which was formed by several fused trabeeulae
74 earneae.
THE AMERICAN ~{EART JOURNAL Fl-om its base it tapered gradually upward into the velltrieuiut' surface
uf the anterior leaflet o~ the mltral valve with which it fused, extending in the valve to within 0.3 era. of the line of attachment of the et, sp to the m e m b r a n o u s septum beneath the noneorenary cusp of the aortic wdve, it was 0.5 em. b r e a d and quite fiat.
At its upper extremity
F r o m tile posterior and lateral aspects of
the papillary muscle the usual ehordae tendinae were given off and were attached to the valve leaflets in the usual maturer. One of the ehordae tendineae was r a t h e r thick in its u p p e r portion~ but there was no evidence of preexisting endoearditis unless this thickened s t r a n d m i g h t be so considered. The posterior papillary bundles were of the usual form. The functional capability of the m i t r a l valve was app a r e n t l y normal.
Fig. :L--(Case 2) The large le£t anterior papillary muscle comes to a point at the margin of the anterior cusp of the mitral valve. The apex, a is attached directly to the valve and short ehordge tendineae are given off laterally from the muscle bundle. CASE 2.---The subject was a woman, aged f o r t y m i n e .~ears~ who died ~f calxliac decompensation following hypertension. The h e a r t weighed 744 gin. (body weight, 73 kg., or 160 p o u n d s ) . The left ventricle was col~siderably h y p e r t r o p h i e d and dilated and the r i g h t ventricle was moderately h y p e r t r o p h i e d and nmch dilated. The large anterior papillary muscle of the left ventricle was formed mainly by fusion of three trabeculae carueae, the middle nmseular projecti(m being the largest (Fig. 2). Above and on the right side the fuse(] bundles c;~me to a b l u n t point, ~).2 em. broad, which was inserted into the free edge of the anterior leaflet of the mitral valve near its extreme r i g h t cnd~ but the muscle did not penetrate f a r into the leaflet nor connect with the vetrlcu]ar muscle. The insertio~t was more tendinous than muscular. Chordae tendinae, which were shorter t h a n usual~ arose f r o m the sides of the papillary muscle and were inserted into the valve leaflets normally.
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i n t h i s case the m u s c u l a r a t t a c h m e n t of tlle p a p i l l a r y muscle held the r i g h t end of the a n t e r i o r leaflet in a r a t h e r fixed position, so t h a t r e g u r g i t a t i o n would perh a p s have been m o r e m a r k e d i f the m i t r a l r i n g h a d become dilated. CASE 3 . - - T h e s u b j e c t was a m a n , a g e d t w e n t y - n i n e years, who died of electric shock. The h e a r t a p p e a r e d n o r m a l except for a few s u b e p i c a r d i a l petechiae. The left a n t e r i o r p a p i l l a r y muscle consisted of one large, cone-shaped b u n d l e with two smaller ones on the left a n d an a n o m a l o u s b u n d l e above a n d on t h e r i g h t ( F i g . 3). T h e l a t t e r was connected with the m a i n p a p i l l a r y muscle b y n a r r o w cords of muscle a n d with t r a b e c u l a e carneae medial to it. I t t a p e r e d as it a s c e n d e d a n d was i n s e r t e d iIlto t h e v e n t r i e u l a r s u r f a c e of t h e a n t e r i o r cusp of t h e m i t r a l valve into which it e x t e n d e d h a l f w a y to t h e m e m b r a n o u s a t t a c h m e n t of the cusp close to its r i g h t side. I t t h e n connected with the muscle of t h e wall of t h e ventricle. N e a r
Fig. 3 . - - ( C a s e 3) A n o m a l o u s muscle bundle, b, associated with the left anterior papillary muscle is inserted into the anterior cusp of the mitral valve. t h e valve it sent off a small cylindrical b e a m of muscle u p w a r d a n d to the r i g h t which also joined the muscle of t h e wall of t h e ventricle. The lamella of i n s e r t i o n of the a n o m a l o u s bundle was 0.4 em. wide. CASE 4 . - - T h e s u b j e c t was a m a n , aged t h i r t y - e i g h t years, who died of p u h n o n a r y complications following g a s t r o e n t e r o s t o m y for duodenal ulcer. The m i t r a l valve showed acute v e g e t a t i v e endocarditis. A n m n b e r of chordae t e n d i n e a e of the posterior p a p i l l a r y muscle of the l e f t ventricle c o n t a i n e d cylindrical b a n d s of m u s c l e wifich e x t e n d e d as f a r as the i n s e r t i o n of the cords into tile m i t r a l leaflets ( F i g . 4). T h e m o s t l a t e r a l muscle bundle of the p a p i l l a r y m u s e l e g a v e rise to a m u s c u l a r beam, 0.2 era. in d i a m e t e r in the middle, which e x t e n d e d into the posterior cusp of the m i t r a l valve, b e c o m i n g thleker as it appro'~ched t h e valve. I t contained some t e n d i n o u s s t r a n d s a n d at t h e u p p e r e x t r e m i t y divided into two m a i n m u s c u l a r
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b e a m s a n d several small chordae tendineae. A t a b o u t the m i d d l e it 'and a small m u s c u l a r b e a m c o n n e e t l n g it to one of t h e frabeeulae earneae of t h e wall of the ventricle. CASE 5 . - - T h e s u b j e c t was a boy~ a g e d f o u r t e e n years~ who died of suffocation due to i n h a l a t i o n of food into the bronchi. The h e a r t was s o m e w h a t hypertrophied~ w e i g h i n g 271 gin. a n d b o t h ventricles were considerably dilated. On t h e a n t e r i o r wall of the r i g h t ventricle was t h e u s u a l l a r g e p a p i l l a r y muscle, b u t i n s t e a d of h a v i n g the c o m m o n a t t a c h m e n t of chordae t e n d i n e a e to the a d j a c e n t halves of t h e medial a n d a n t e r i o r cusps of t h e t r i c u s p i d valve it p a s s e d directly up u n d e r t h e v e n t r i e u l a r s u r f a c e of the a n t e r i o r cusp ( F i g . 5). I t gave off a few chordae
-~ig. 4.--(Case 4) !~luscle bundles, b, are in the chordae tendineae of the !eft posterior papillary muscle traversing the whole length and extending to the mitral cusps, especially the posterior.
t e n d i n e a e a n d became a fiat lame]l% 0.7 era. wid% which was i n s e r t e d in a s t r a i g h t line into t h e fibrous cusp, 0.55 cm. f r o m t h e a t t a c h m e n t of the valve; several s t r a n d s of m u s c l e could be seen b y t r a n s i l t u m i n a t i o n of t h e cusp p a s s i n g f r o m this line of insertion to t h e muscle a t t h e a t t a c h e d edge of t h e valve. The free p o r t i o n of t h e p a p i l l a r y muscle was 2.7 cm. long. J u s t to t h e l e f t side of t h i s p a p i l l a r y muscle was a s m a l l one which h a d chordae t e n d i n e a e a t t a c h e d to t h e a d j a c e n t edges of the m e d i a l a n d a n t e r i o r cusps of the t r i c u s p i d valve b u t which also s e n t a n a r r o w m u s c u l a r lamella up u n d e r t h e valve to be i n s e r t e d b y a fiat t r i a n g u l a r e n l a r g e m e n t into t h e cusp n e a r i t s line of a t t a c h m e n t ; between this t r i a n g u l a r l a m e l l a of insertion a n d the p a p i l l a r y m ~ ¢ l e proper was a small fibrous area in which muscle
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was n o t visible maeroseopieally. On the r i g h t side of the m a i n p a p i l l a r y muscle was ailother s m a l l p a p i l l a r y muscle, t h e ehordae t e n d i n e a e of whleh were a t t a c h e d to t h e a d j a c e n t edges of the medial a n d posterior cusps of the valve. Several very s m a l l p a p i l l a r y muscles gave rise to ehordae t e n d i n e a e which were a t t a c h e d to the posterior cusp. COMMENT
This type of anomaly is undoubtedly congenital. Early in the development of the atrio-ventrieular valves muscular tissue f r o m the myoe a r d i u m invades the endocardial tissue of the eusps and replaces it. The m u s c u l a r tissue of the cusps becomes elosely blended with the
Fig. 5.--(Case 5) The papillary muscles of the right ventricle (retouched) are cut loose and turned upward to expose their ventricular surfaces. The large papillary muscle, b, is inserted into the anterior cusp of the tricuspid valve. The smaller papillary muscle, b', also has a muscular lamella of insertion.
subjacent nmsculature of the walls of the ventricles. This stage in the development of the cusps is soon followed by replacement of the muscular tissue by collagenous connective tissue, the process evidently taking place mainly from above downward. The subjacent trabeculate musculature also is replaced by collagenous connective tissue. The fibrous cords so developed are the ehordae tendineae. Muscular tissue persists at the p a r i e t a l ends of the cords and f o r m s the p a p i l l a r y muscles. I n eases such as those just described the rep l a c e m e n t b y collagenous eonnective tissue ceases too soon or is imperfect, and m u s c u l a r tissue is left in plaee of chordae tendineae.
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The only other expianati(m would be that ]ocalized. m~docarditis had p r o d u e e d thiekening and r e t r a c t i o n of the ehordae ten(tineae, causing the cusp of the valve and the p a p i l l a r y muscle to be (lraw~'~ together. All the faets, however, are opposed to this eoneeption and point r a t h e r to the d e v e l o p m e n t a l origin of the condition. The instanees of this a n o m a l y previously r e p o r t e d and those described in this p a p e r have ~ot a p p e a r e d to possess an); clinical significance. In Case 2 of this series it seemed t h a t the eondition m i g h t have increased the insufficiency of a dilate(] mitral ring had sueh been present, but the mitral orifice was a p p a r e n t l y not v e r y incompetent. REFERENCES
l()rsSs-P6cs: Abnornle )fuskelbiindc{ und Lamellen der venSsen Klappenapparate des Herzensj -Verhandl. d. deutsch. ~ath. Gesel]sch, 1910, xiv~ 321. 2Prezewoski, E.: [Excessively Long. Papillary Muscles of the Heart.] Pare. Towarz. Lek., Warsaw, 1896~ xcii, 423; Abstr. Centralbl. f. ~llg. Path. ll. path. Anat., 1897, viii, 152.
R D I N A R I L Y the p a p i l l a r y muscle of the h u m a n h e a r t is a t t a c h e d to the valve leaflet b y a n u m b e r of fibrous ehordae tendineae which are ahnost as long as, or even longer than, the muscle. Occasionally, however, macroscopic muscle b a n d s extend u p w a r d into these cords and m a y even t r a v e r s e their whole length, or more rarely, the p a p i l l a r y muscle itself m a y replace several ehordae tendineae and be a t t a c h e d directly to the valve. In the l i t e r a t u r e I have been able to find only two references to such anomalies, although they must eertainly occur in the experience of every pathologist whose m a t e r i a l f r o m necropsies is a b u n d a n t , in 1896 P r z e w o s k i described f o u r eases. I n three cases the tip of the n o r m a l p a p i l l a r y muscle in the left ventricle was p r o l o n g e d into a thin extension which took the place of a cord. This f o r m of the a n o m a l y he did not consider altogether rare. He p r o n o u n c e d his f o u r t h ease to be more unusual; in this, a large a n t e r i o r p a p i l l a r y muscle sent out a large m u s c u l a r extension which entirely replaced several chordae tendineae a n d was inserted into the v e n t r i e u l a r surface of the m R r a l valve up to the fibrous ring. P r z e w o s k i laid down the criterion t h a t only the p a p i l l a r y muscles whose tip extended up to the valve should be considered a b n o r m a l l y long. In 1910 Ors6s-P6es described twelve cases of anomalies of this type and mentioned another. I n four of the described eases a cylindrical muscular b e a m f r o m the anterior p a p i l l a r y muscle was inserted iuto the posterior leaflet of the tricuspid valve up to the a t t a c h m e n t of the cusp. The lamella of insertion was relatively large. I n the other eig'ht eases m u s e u l a r beams f r o m the anterior p a p i l l a r y muscle of the left ventricle were inserted in the v e n t r i c u l a r surface of the a n t e r i o r leaflet of the m i t r a l valve. W h e n the muse!e bundle was inserted into the middle of the valve leaflet, the plate of insertion was s y m m e t r i c and t r i a n g u l a r . W h e n the bundle originated f r o m the r i g h t side of the a n t e r i o r p a p i l l a r y muscle, it fused with the corresponding p a r t of the a n t e r i o r cusp with a spade-shaped lamella of insertion which t u r n e d laterally and eventually connected with the v e n t r i c u l a r wall. Ors6s-Pdes explained the f a c t t h a t the lamella of insertion of these bundles in the r i g h t ventriele always ended at the a t t a c h e d edge of the v a l v e on the basis t h a t the venous orifice of the r i g h t ventricle
O
* W o r k done in t h e Section on P a t h o l o g i e A n a t o m y , T h e M a y o Clinic. t F e l l o w in Medicine, T h e 1Vfayo F o u n d a t i o n . 72
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73
e n t i r e l y b y m u s c l e , w h i l e in t h e l e f t v e n o u s orifice t h e
m u s c l e o v e r the a n t e r i o r v a l v u l a r cusp is m i s s i n g . One of his p a t i e n t s w a s t h e son of a n o t h e r p a t i e n t r e p o r t e d , a c i r c u m s t a n e e w h i c h a r g u e d t h a t t h e a n l a g e m i g h t be h e r e d i t a r y . I n one case t h e r e was a calcified p l a q u e a t the p o i n t of i n s e r t i o n a n d in a n o t h e r on t h e a u r i c u l a r side of t h e p o i n t of i n s e r t i o n of t h e m u s c l e b u n d l e w a s a s u b e n d o c a r d i a l tubercle. Ors6s-P~es t h o u g h t t h e s e f e a t u r e s c o u l d be e x p l a i n e d b y t h e s t r e s s of a b n o r m a l p u l l of t h e m u s c l e . I h a v e f o u n d five eases of a n o m a l i e s of t h i s t y p e .
These occurred
in a b o u t 550 n e e r o p s i e s , a n i n c i d e n c e of 0.91 p e r cent.
Fig. l.--(Case I) Left anterior papillary muscle is inserted directly into the anterior cusp of the mitral valve just beneath the noncoronary cusp of the aortic valve.
REPORT OF CASES CASE 1.--The subject was a man, aged sixty years, who died from uremia following an acute exacerbation of ehroaie pyelonephritis. The systolic blood pressure was 220 mm. and the diastolic, 110 ram. The heart weighed 476 gin. (body weight, 61.4 kg., or 135 pounds). There was coronary sclerosis graded 2. With the exception of moderate hypertrophy, moderate coronary sclerosis and the anomaly, the heart appeared normal. The anterior papillary muscle of the left ventricle was 5.0 cm. long on its free inner surface and 2.5 cm. long on its mural surface (Fig. 1). It was 1.6 cm. broad at its base, which was formed by several fused trabeeulae
74 earneae.
THE AMERICAN ~{EART JOURNAL Fl-om its base it tapered gradually upward into the velltrieuiut' surface
uf the anterior leaflet o~ the mltral valve with which it fused, extending in the valve to within 0.3 era. of the line of attachment of the et, sp to the m e m b r a n o u s septum beneath the noneorenary cusp of the aortic wdve, it was 0.5 em. b r e a d and quite fiat.
At its upper extremity
F r o m tile posterior and lateral aspects of
the papillary muscle the usual ehordae tendinae were given off and were attached to the valve leaflets in the usual maturer. One of the ehordae tendineae was r a t h e r thick in its u p p e r portion~ but there was no evidence of preexisting endoearditis unless this thickened s t r a n d m i g h t be so considered. The posterior papillary bundles were of the usual form. The functional capability of the m i t r a l valve was app a r e n t l y normal.
Fig. :L--(Case 2) The large le£t anterior papillary muscle comes to a point at the margin of the anterior cusp of the mitral valve. The apex, a is attached directly to the valve and short ehordge tendineae are given off laterally from the muscle bundle. CASE 2.---The subject was a woman, aged f o r t y m i n e .~ears~ who died ~f calxliac decompensation following hypertension. The h e a r t weighed 744 gin. (body weight, 73 kg., or 160 p o u n d s ) . The left ventricle was col~siderably h y p e r t r o p h i e d and dilated and the r i g h t ventricle was moderately h y p e r t r o p h i e d and nmch dilated. The large anterior papillary muscle of the left ventricle was formed mainly by fusion of three trabeculae carueae, the middle nmseular projecti(m being the largest (Fig. 2). Above and on the right side the fuse(] bundles c;~me to a b l u n t point, ~).2 em. broad, which was inserted into the free edge of the anterior leaflet of the mitral valve near its extreme r i g h t cnd~ but the muscle did not penetrate f a r into the leaflet nor connect with the vetrlcu]ar muscle. The insertio~t was more tendinous than muscular. Chordae tendinae, which were shorter t h a n usual~ arose f r o m the sides of the papillary muscle and were inserted into the valve leaflets normally.
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i n t h i s case the m u s c u l a r a t t a c h m e n t of tlle p a p i l l a r y muscle held the r i g h t end of the a n t e r i o r leaflet in a r a t h e r fixed position, so t h a t r e g u r g i t a t i o n would perh a p s have been m o r e m a r k e d i f the m i t r a l r i n g h a d become dilated. CASE 3 . - - T h e s u b j e c t was a m a n , a g e d t w e n t y - n i n e years, who died of electric shock. The h e a r t a p p e a r e d n o r m a l except for a few s u b e p i c a r d i a l petechiae. The left a n t e r i o r p a p i l l a r y muscle consisted of one large, cone-shaped b u n d l e with two smaller ones on the left a n d an a n o m a l o u s b u n d l e above a n d on t h e r i g h t ( F i g . 3). T h e l a t t e r was connected with the m a i n p a p i l l a r y muscle b y n a r r o w cords of muscle a n d with t r a b e c u l a e carneae medial to it. I t t a p e r e d as it a s c e n d e d a n d was i n s e r t e d iIlto t h e v e n t r i e u l a r s u r f a c e of t h e a n t e r i o r cusp of t h e m i t r a l valve into which it e x t e n d e d h a l f w a y to t h e m e m b r a n o u s a t t a c h m e n t of the cusp close to its r i g h t side. I t t h e n connected with the muscle of t h e wall of t h e ventricle. N e a r
Fig. 3 . - - ( C a s e 3) A n o m a l o u s muscle bundle, b, associated with the left anterior papillary muscle is inserted into the anterior cusp of the mitral valve. t h e valve it sent off a small cylindrical b e a m of muscle u p w a r d a n d to the r i g h t which also joined the muscle of t h e wall of t h e ventricle. The lamella of i n s e r t i o n of the a n o m a l o u s bundle was 0.4 em. wide. CASE 4 . - - T h e s u b j e c t was a m a n , aged t h i r t y - e i g h t years, who died of p u h n o n a r y complications following g a s t r o e n t e r o s t o m y for duodenal ulcer. The m i t r a l valve showed acute v e g e t a t i v e endocarditis. A n m n b e r of chordae t e n d i n e a e of the posterior p a p i l l a r y muscle of the l e f t ventricle c o n t a i n e d cylindrical b a n d s of m u s c l e wifich e x t e n d e d as f a r as the i n s e r t i o n of the cords into tile m i t r a l leaflets ( F i g . 4). T h e m o s t l a t e r a l muscle bundle of the p a p i l l a r y m u s e l e g a v e rise to a m u s c u l a r beam, 0.2 era. in d i a m e t e r in the middle, which e x t e n d e d into the posterior cusp of the m i t r a l valve, b e c o m i n g thleker as it appro'~ched t h e valve. I t contained some t e n d i n o u s s t r a n d s a n d at t h e u p p e r e x t r e m i t y divided into two m a i n m u s c u l a r
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b e a m s a n d several small chordae tendineae. A t a b o u t the m i d d l e it 'and a small m u s c u l a r b e a m c o n n e e t l n g it to one of t h e frabeeulae earneae of t h e wall of the ventricle. CASE 5 . - - T h e s u b j e c t was a boy~ a g e d f o u r t e e n years~ who died of suffocation due to i n h a l a t i o n of food into the bronchi. The h e a r t was s o m e w h a t hypertrophied~ w e i g h i n g 271 gin. a n d b o t h ventricles were considerably dilated. On t h e a n t e r i o r wall of the r i g h t ventricle was t h e u s u a l l a r g e p a p i l l a r y muscle, b u t i n s t e a d of h a v i n g the c o m m o n a t t a c h m e n t of chordae t e n d i n e a e to the a d j a c e n t halves of t h e medial a n d a n t e r i o r cusps of t h e t r i c u s p i d valve it p a s s e d directly up u n d e r t h e v e n t r i e u l a r s u r f a c e of the a n t e r i o r cusp ( F i g . 5). I t gave off a few chordae
-~ig. 4.--(Case 4) !~luscle bundles, b, are in the chordae tendineae of the !eft posterior papillary muscle traversing the whole length and extending to the mitral cusps, especially the posterior.
t e n d i n e a e a n d became a fiat lame]l% 0.7 era. wid% which was i n s e r t e d in a s t r a i g h t line into t h e fibrous cusp, 0.55 cm. f r o m t h e a t t a c h m e n t of the valve; several s t r a n d s of m u s c l e could be seen b y t r a n s i l t u m i n a t i o n of t h e cusp p a s s i n g f r o m this line of insertion to t h e muscle a t t h e a t t a c h e d edge of t h e valve. The free p o r t i o n of t h e p a p i l l a r y muscle was 2.7 cm. long. J u s t to t h e l e f t side of t h i s p a p i l l a r y muscle was a s m a l l one which h a d chordae t e n d i n e a e a t t a c h e d to t h e a d j a c e n t edges of the m e d i a l a n d a n t e r i o r cusps of the t r i c u s p i d valve b u t which also s e n t a n a r r o w m u s c u l a r lamella up u n d e r t h e valve to be i n s e r t e d b y a fiat t r i a n g u l a r e n l a r g e m e n t into t h e cusp n e a r i t s line of a t t a c h m e n t ; between this t r i a n g u l a r l a m e l l a of insertion a n d the p a p i l l a r y m ~ ¢ l e proper was a small fibrous area in which muscle
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was n o t visible maeroseopieally. On the r i g h t side of the m a i n p a p i l l a r y muscle was ailother s m a l l p a p i l l a r y muscle, t h e ehordae t e n d i n e a e of whleh were a t t a c h e d to t h e a d j a c e n t edges of the medial a n d posterior cusps of the valve. Several very s m a l l p a p i l l a r y muscles gave rise to ehordae t e n d i n e a e which were a t t a c h e d to the posterior cusp. COMMENT
This type of anomaly is undoubtedly congenital. Early in the development of the atrio-ventrieular valves muscular tissue f r o m the myoe a r d i u m invades the endocardial tissue of the eusps and replaces it. The m u s c u l a r tissue of the cusps becomes elosely blended with the
Fig. 5.--(Case 5) The papillary muscles of the right ventricle (retouched) are cut loose and turned upward to expose their ventricular surfaces. The large papillary muscle, b, is inserted into the anterior cusp of the tricuspid valve. The smaller papillary muscle, b', also has a muscular lamella of insertion.
subjacent nmsculature of the walls of the ventricles. This stage in the development of the cusps is soon followed by replacement of the muscular tissue by collagenous connective tissue, the process evidently taking place mainly from above downward. The subjacent trabeculate musculature also is replaced by collagenous connective tissue. The fibrous cords so developed are the ehordae tendineae. Muscular tissue persists at the p a r i e t a l ends of the cords and f o r m s the p a p i l l a r y muscles. I n eases such as those just described the rep l a c e m e n t b y collagenous eonnective tissue ceases too soon or is imperfect, and m u s c u l a r tissue is left in plaee of chordae tendineae.
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The only other expianati(m would be that ]ocalized. m~docarditis had p r o d u e e d thiekening and r e t r a c t i o n of the ehordae ten(tineae, causing the cusp of the valve and the p a p i l l a r y muscle to be (lraw~'~ together. All the faets, however, are opposed to this eoneeption and point r a t h e r to the d e v e l o p m e n t a l origin of the condition. The instanees of this a n o m a l y previously r e p o r t e d and those described in this p a p e r have ~ot a p p e a r e d to possess an); clinical significance. In Case 2 of this series it seemed t h a t the eondition m i g h t have increased the insufficiency of a dilate(] mitral ring had sueh been present, but the mitral orifice was a p p a r e n t l y not v e r y incompetent. REFERENCES
l()rsSs-P6cs: Abnornle )fuskelbiindc{ und Lamellen der venSsen Klappenapparate des Herzensj -Verhandl. d. deutsch. ~ath. Gesel]sch, 1910, xiv~ 321. 2Prezewoski, E.: [Excessively Long. Papillary Muscles of the Heart.] Pare. Towarz. Lek., Warsaw, 1896~ xcii, 423; Abstr. Centralbl. f. ~llg. Path. ll. path. Anat., 1897, viii, 152.