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JACC Vol. 5. No.6June 1985:1474-7

Unusual Distribution of Left Ventricular Hypertrophy in ObstructiveHypertrophic Cardiomyopathy: Localized Posterobasal Free WallThickening in Two Patients

BARRY J. MARON, MD, FACC, PAOLO SPIRITO, MD, FRANCESCO CHIARELLA, MD,

CARLO VECCHIO, MD

Bethesda, Maryland and Genoa, Italy

Two patients with hypertrophic cardiomyopathy and apreviously unreported distribution ofteft ventricular hy­pertrophy are described. Each patient showed sub­stantial wall thickening that was confinedto the postern­basal segment of the left ventricular free wall, as wellas evidence of dynamic subaortic obstruction. This ob­servation emphasizes the fact that hypertrophic cardio-

Two-dimensional echocardiography has been used to iden­tify a variety of patterns of left ventricular hypertrophy inpatients with hypertrophic cardiomyopathy (1-4). Ventric­ular wall thickening is most commonly present in substantialportions of both ventricular septum and anterolateral freewall (2,5). However, hypertrophy may often be localizedto relatively small areas of the left ventricular wall, usuallythe anterior basal septum (2). This report describes twopatients with hypertrophic cardiomyopathy and evidence ofsubaortic obstruction in whom a previously undescribed pat­tern of ventricular wall thickening was identified. In thesepatients, hypertrophy was confined to the posterobasal freewall, that portion of the left ventricle least frequently hy­pertrophied in patients with hypertrophic cardiomyopathy(2).

Case ReportsClinical findings. Clinical and echocardiographic find­

ings in the two patients are summarized in Table I. The

From the Cardiology Branch, Echocardiography Laboratory, NationalHeart, Lung, and Blood Institute, National Institutes of Health, Bethesda,Maryland and Divisione di Cardiologia, Ente Ospedaliero Ospedali Gal­liera, Genoa, Italy. Manuscript received October 9, 1984; revised manu­script received December 26, 1984, accepted January 11, 1985.

Address for reprints: Barry J. Maron, MD, National Heart, Lung, andBlood Institute, National Institutes of Health. Building 10. Room 7B-15.Bethesda, Maryland 20205.

© 1985 by the American College of Cardiology

myopathy is characterized by a broad morphologicspectrum. Furthermore, it demonstrates a uniquecircumstance in which left ventricular outflow tract ob­struction may occur in the absence of anterior and basalseptal hypertrophy.

(J Am Coli CardioI1985;5:1474-7)

patients differed with regard to symptomatic state, PatientI being virtually asymptomatic and Patient 2 demonstratingmarked functional limitation with dyspnea on exertion andfatigue, angina pectoris, lightheadedness, palpitation andsyncope. Electrocardiograms showed only a deep S wavein lead VI in Patient I and absence of an R wave in leadsVI and V2 in Patient 2.

Each patient had an ejection murmur (grade 4/6 in PatientI and grade 2/6 in Patient 2) at the lower left sternal borderand apex, which increased with standing and decreased withsquatting. Systemic blood pressure recordings were normalin each patient; Patient 2 had normal coronary artery anat­omy as demonstrated by coronary arteriography.

Echocardiographic findings. The echocardiographicfindings were quite similar in the two patients. Each patientshowed hypertrophy confined to only a small region of theleft ventricular wall, that is, the posterobasal free wall justbehind the posterior mitral leaflet (Fig. I to 3). The thicknessof this region was marked (19 mm in Patient I and 18 mmin Patient 2), but was limited to only about a 2 em segmentof the wall, resulting in the morphologic appearance of adiscrete mass. In each patient, all visualized portions of theventricular septum appeared to be of normal thickness. Inaddition, both patients showed reduced end-diastolic cross­sectional area of the left ventricular outflow tract as assessedby two-dimensional echocardiography (Table 1).

Both patients also showed systolic anterior motion of themitral valve on echocardiography under basal conditions

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Table 1. Clinical and Morphologic Data in Two Patients With Hypertrophic Cardiomyopathy and Isolated Posterobasal LeftVentricular Free Wall Hypertrophy

Echocardiographic Dimensions

LYID (mm) LYOTAge (yr) vs- PBLV* LA Areat

Case &Sex FC (mm) (mm) d (mm) (cnr')

1 36M I 9 19 47 27 41 3.82 33F 3 10 18 36 22 31 4.5

*Measurements made by convention at end-diastole (peak of the R wave on the electrocardiogram); [ cross-sectional area of the left ventricular outflowtract at end-diastole as determined by two-dimensional echocardiography (I I); the normal range is 9.0 to 12.6 em! and the range for patients withhypertrophic cardiomyopathy and basal subaortic pressure gradient is 1.5 to 5.0 ern", d = diastole; F = female; FC = functional class (New YorkHeart Association); LA = left atrium; LYID = left ventricular internal dimension; LYOT = left ventricular outflow tract; M = male; PBLV =posterobasal left ventricle; s = systole; VS = ventricular septum.

(Fig . 1, 2 and 4). In Patient I, the systolic anterior motionwas marked . and the distal tip of the anterior mitral leafletclosely approached the ventricul ar septum for a substant ialproportion of echo cardio graphic systole (Fig. 4); mild par­tial premature closure of the aortic valve was also evident.Patient 2 showed only mild systolic anterior motion . whichproved on two-dimensional echocardiographic study to be

Figure I. Patient I. Stop frame two-dimensional echocardiogramobtained in the apical four chamber view during systole. Thediscrete area of localized hypertrophy in the posterobasal segmentof the left ventricle (LV) is indicated by arrowheads . Note themarkedsystolic anterior motion of the anterior mitral leaflet (AML).Only the tip of the anterior leaflet comes in contact with the ven­tricular septum (VS). which is of normal thickness. LA = leftatrium.

produced preferentially by the posterior mitral leaflet (6 ,7);also , the anterior leaflet prolapsed during late systole intothe left atrium. Premature aortic valve closure was absent.

Hemodynamic data. At cardiac catheterization, Patient2 had a basal 20 mm Hg peak systolic pressure gradientacross the left ventricular outflow tract ; with isoproterenolinfusion the gradient increased to 105 mm Hg. Left ven­tricular end-diastolic pressure was 20 mm Hg . Patient I didnot undergo catheterization because there was no clinicalindication.

Figure 2. Patient I. Stop frame two-dimensional echocardiogramobtained in parasternal long-axis viewduringsystole. The localizedregion of posterobasal wall thickening is shown by the dotted line.Note the marked mitral systolic anterior motion in which the an­terior leaflet bends acutely, so that only the leaflet tip closelyapproaches the ventricular septum (VS) (arrowheads) . Ao ==aorta; LA = left atrium.

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Figure 3. Patient 2. M-mode echocardiogram showing postero­basalleft ventricular waIl(PW)thickening. The ventricular septum(VS) is of normal thickness. The posterobasal free waIl is abouttwice as thick as the septum. Calibration dots are 10 mm apart.MV = mitral valve.

Family studies. Hypertrophic cardiomyopathy was doc­umented by echocardiography in at least one first degreerelative of each study patient. The 34 year old asymptomaticsister of Patient 1 showed a pattern of hypertrophy moretypical of hypertrophic cardiomyopathy (4), involving pri­marily the anterior and posterior segments of the ventricularseptum (maximal thickness 30 mm). The 67 year old motherof Patient 2 had hypertrophy of the septum and posteriorfree wall, which was most marked in the apical half of theleft ventricle (maximal thicknesses 20 mm), in the absenceof other cardiac disease. Also, the 27 year old asymptomaticbrother of Patient 2 had discrete areas of hypertrophy in theposterior ventricular septum and posterolateral free wall(maximal thickness 22 mm).

DiscussionOur two patients with hypertrophic cardiomyopathy dem­

onstrate a unique pattern of left ventricular hypertrophy notpreviously described in two-dimensional echocardiographicstudies of more than 300 patients with this disease (1-4).

Figure 4. Patient 1. M-mode echocardiogram atthe level of the mitralvalve (MV). Systolic anteriormotion of the mitral valve is seen (arrow) as theanterior mitral leaflet comes into near appositionwith the ventricularseptum(VS). This echocardio­gram also suggests that mitral systolicanteriormo­tion is confined to the distal portion of the leaflet(see portion of recording to the left and comparewith that in Fig. 2), but is notproducedby the moreproximal portion of the leaflet (see portion of re­cording to the right and compare with that in Fig.2). Posterobasal free waIl (PW) hypertrophy is notwelldefinedin thisrecording. RV = rightventricle.

Indeed, these two patients with localized posterobasal wallthickening have hypertrophy in that region of left ventriclewhich is the site least frequently thickened in patients withhypertrophic cardiomyopathy. Therefore, our findings em­phasize the diverse morphologic expressions that may occurwithin the clinical spectrum of hypertrophic cardiomyopathy.

Differential diagnosis. The uniqueness of this patternof hypertrophy raises the possibility that our patients had acardiac disease process other than hypertrophic cardio­myopathy (for example, tumor, clot or cardiac manifestationof hypereosinophilia [8]). However, this possibility seemsunlikely for two reasons. First, we were able to confirm byechocardiography a more typical distribution of left ven­tricular hypertrophy in at least one first degree relative ofeach patient, indicative of the genetic transmission of hy­pertrophic cardiomyopathy (9) with a variable morphologicexpression (4). Second, each patient showed evidence ofdynamic obstruction to left ventricular outflow (measuredat cardiac catheterization in Patient 2 and estimated by echo­cardiography in Patient 1) due to systolic anterior motionof the mitral valve (6,7,10,11) and typical of hypertrophiccardiomyopathy. Furthermore, in each patient, clinical evi­dence of the hypereosinophilic syndrome was lacking; echo­cardiograms showed no cardiac morphologic changes overa period of about 1 year (Patient l) or 3 years (Patient 2),making the diagnosis of tumor or clot less likely.

Outflow tract morphology. Of note, in hypertrophiccardiomyopathy, subaortic obstruction and systolic anteriormotion of the mitral valve usually occur in the presence ofanterior basal septal hypertrophy and a small left ventricularoutflow tract (II). However, our patients showed a distinctlydifferent left ventricular configuration, in which the left ven­tricular outflow tract was small even though basal ventricularseptal hypertrophy was absent. This reduction in outflowtract size was probably due, in part, to the posterobasal wallthickening which caused the mitral valve to be positionedabnormally close to the septum, thereby predisposing to theVenturi phenomenon (12) and systolic anterior motion ofthe mitral valve (that is, subaortic obstruction).

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