A previously undescribed case of right ventiricular aneurysm (RVA) associated with hypertrophic cardiomyopathy in an advanced stage is reported. The diagnosis was established by noninvasive (cardiac two-dimensional echocardiogram and nuclear MRI) and invasive (cardiac catheterization, angiography, and biventricular endomyocardial biopsy) cardiac examinations, which documented hypertrophied, dilated and hypokinetic biventricular chambers associated with typical histologic findings (histologic hypertrophic cardiomyopathy index of 66%). A prominent narrowing of myocardial arterioles, extended to the right ventricular myocardium, has been identified and has been hypothesized as being responsible for RVA formation.
(CHEST 1998; 113:552-54)
Key words: hypertrophic cardiomyopathy; right ventricular aneurysm
Abbreviations: HCM=hypertrophic cardiomyopathy; LV=left ventricular; RV=right ventricular; RVA=right ventricular aneurysm
Right ventricular aneurysm (RVA) is a rare pathologic entity occurring mostly in association with arrhythmogenic right ventricular (RV) cardiomyopathy1 and, less commonly, as a congenital anomaly[2] or as a result of ischemic,[3] traumatie,[4] or inflammatory events.[5]
Hypertrophic cardiomyopathy (HCM) has not yet been recognized as a possible cause of RVA, although the RV myocardium is commonly affected by the disease,[6] which may present with an obstruction of RV outflow.[7]
The authors report a case of anteroapical RVA associated with HCM in an advanced stage as suggested by the presence of hypertrophied, dilated, and hypoldnetic biventricular chambers with a typical histologic pattern at biventricular endomyocardial biopsy.
Case Report
A 63-year-old man was admitted to the hospital because of chest discomfort associated with dyspnea on moderate effort (New York Heart Association II). These symptoms had started 6 months earlier. A family history was negative for sudden death or hypertrophic cardiomyopathy. At the time of admission, results of a physical examination were normal. In particular, during heart auscultation no murmurs or abnormal sounds were heard. BP was 130/80 mm Hg. Results of routine laboratory tests (hematologic and biochemical studies and urine analysis) were within normal limits. A chest x-ray film showed a moderate prominence of the third left arch of the cardiac silhouette. The ECG showed sinus rhythm with left ventricular hypertrophy and diffuse nonspecific abnormalities of the ST-T wave.
The two-dimensional echocardiogram showed a moderate degree of concentric left ventricular (LV) hypertrophy (interventricular septum, 15 mm; LV free wall, 13 mm). The left ventricle was moderately dilated (LV end diastolic, 60 mm) with mild diffuse reduction of LV contractility (LV ejection fraction, 0.45). The right ventricle was mildly dilated, and the anteroapical wall was thin and showed an aneurysm with a maximum diameter of 40 mm. Inside the aneurysm a stratified thrombus was present. These data were confirmed by a transesophageal echocardiogram (Fig 1). No abnormalities of a valvular pattern were found. Cardiac magnetic resonance scanning was performed at 0.5 T (Vectra; GEMS; Milwaukee) in vertical and horizontal long and short axis, with a multislice spin echo sequence (TR/ TE=R-R/40 ms; 3 NEX; matrix, 160X256; slice thickness, 10 mm, slice gap, 1 mm) and cine-MRI, both ECG-triggered. The study confirmed the presence of an apical RV aneurysm (Fig 2), with a subtle mural thrombus, and demonstrated the presence of myocardial segmental hypertrophy, particularly in the right ventricle where thickened segments (end-diastolic [ED] thickness, 7 mm) alternated with thinned segments (ED thickness, 2.5 mm); interventricular septum and left ventricular lateral wall were homogeneously thickened (ED thicknesses, 16 and 13 mm, respectively). No focal inhomogeneity of myocardium signal intensity suggesting areas of macroscopic fatty infiltration was documented. At cine-MRI, the midventricular and apical RV free walls appeared dyskinetic.
[FIGURES 1 & 2, ILLUSTRATION OMITTED]
Cardiac catheterization showed a mildly increased pulmonary pressure (systolic value, 40 mm Hg) with moderately elevated LV and RV end-diastolic pressure (18 and 15 mm Hg, respectively). Angiography confirmed the biventricular dilatation and the presence of an apical aneurysm in the right ventricle. LV systolic function was mildly reduced (LV ejection fraction, 0.45; cardiac index, 2.36 L/min/[m.sup.2]), and no atrioventricular or intraventricular gradients were documented. Coronary angiography showed normal epicardial coronary arteries. Catheterization was followed by biventicular endomyocardial biopsy, with the extraction of three fragments from each chamber which were processed for histologic studies according to standard techniques and stains (hematoxylin-eosin, Miller's elastic, van Gieson, and Masson's trichrome stain). Specimens from the right ventricle were taken from the interventricular septum and RV free wall because of the presence of the apical aneurysm.
Histologic findings showed similar changes in the R and LV specimens, consisting of severely hypertrophied myocardial fibers (cell diameter at nuclear level being up to 60 [Mu]m) often in total disarray (Fig 3). The myocytes showed some perinuclear halo, vacuolar degeneration, and occasional myocytolysis. Interstitial and replacement fibrosis were present to an extensive degree. Several arterioles were included, even in the RV specimens showing pronounced thickening of the muscular coat with remarkable lumen narrowing (Fig 4). The endocardium was thickened to a severe degree showing clear prominence of the smooth muscle component. The histologic hypertrophic cardiogmyopathy index[8] was 66%, which is well within the diagnostic values ([is greater than] 50%) for HCM in the dilated phase.
[FIGURE 3 & 4, ILLUSTRATION OMITTED]
The patient was treated with digitalis (digoxin, 0.25 mg daily), diuretics (furosemide, 25 mg daily), angiotensin-converting enzyme inhibitors (enalapril maleate, 20 mg daily), and anticoagulants (dicumarol to maintain international normalized ratio between 2.5 and 3.5). The patient's symptoms improved; however, due to the poor prognosis of the disease, he was considered for heart transplantation.
Discussion
RVA is a rare clinicopathologic entity that may result from several causes[1-5] but has not previously been described in association with hypertrophic cardiomyopathy. The diagnosis of HCM in an advanced stage in the case reported here was established by noninvasive (cardiac two-dimensional echocardiogram and MRI scan [Fig 1, 2, respectively]) and invasive (cardiac catheterization, angiography, and biventricular endomyocardial biopsy) examinations which showed hypertrophied, dilated, and hypokinetic ventricles exhibiting typical histologic findings. These features were similar in biopsy samples from both ventricles and consisted of severe hypertrophy with disarray of myocardiocytes (Fig 3) associated with extensive replacement fibrosis and arteriolar narrowing from medial hypertrophy (Fig 4). With regard to the pathogenetic mechanism of aneurysm formation, when such an event occurs in a left ventricle with HCM, severe intraventricular obstruction or coronary artery disease due to atherosclerosis or epicardial bridges usually is recognized.[9]
In the patient reported here, the epicardial coronary arteries were normal, and no intraventricular gradient was detected; systolic pulmonary artery pressure was mildly elevated (40 mm Hg). Nevertheless, RV histologic findings (even in the specimens from the RV free wall) revealed the presence of narrowed arterioles (Fig 4) with extensive replacement fibrosis. Such a small-vessel abnormality is common in HCM, being present in over 80% of patients[10] but usually is localized in the interventricular septum while it is less frequent in the LV free wall and rare in the RV myocardium. We can speculate that in our patient, in addition to a myopathic alteration, chronic ischemic damage could have occurred in the RV myocardium, which is thinner and more vulnerable than the LV myocardium, resulting in extensive fibrosis and aneurysm formation. Indeed, Maron et al[10] stress the ischemic potential of narrowed small vessels in HCM and attribute to them a pathogenetic role when found in scar tissue. Furthermore, in a quantitative analysis of lumen narrowings in intramyocardial arteries of HCM hearts, Tanaka et al[11] report an inverse relationship between vessel obstruction and severity of cardiac dysfunction, the luminal narrowings being more pronounced in dilated cardiomyopathy-like HCM.
Conclusion
From a therapeutic point of view, the recognition of an RVA implies treatment with anticoagulants or antiplatelet drugs, or both, in order to prevent a pulmonary embolism which could be devastating in an already compromised heart. In addition it indicates that the myocardial disease has overcome the limits of conservative treatment and suggests that the patient be considered for heart transplantation. In conclusion, RVA, although rare, can occur in association with HCM in an advanced stage, and its mechanism may be a chronic ischemic insult from small-vessel disease extending to the RV myocardium.
References
[1] Basso C, Thiene G, Corrado D, et al. Arrhythmogenic right ventricular cardiomyopathy: dysplasia, dystrophy, or myocarditis? Circulation 1996; 94:983-91
[2] Hornberger LK, Dalvi B, Benacerraf BR. Prenatal sonographic detection of cardiac aneurysms and diverticula. J Ultrasound Med 1994; 13:967-70
[3] Antonelli Incalzi R, Capparella O, Gemma A, et al. Right ventricular aneurysm: a new prognostic indicator after a first acute myocardial infarction. Cardiology 1991; 79:120-26
[4] Stinson EB, Rowles DF, Shumway NE. Repair of right ventricular aneurysm and ventricular septal defect caused by nonpenetrating cardiac trauma. Surgery 1968; 64:1022-26
[5] Nielsen Kudsk JE. Ventricular fibrillation and cardiac aneurysms caused by sarcoidosis. Ugeskr Laeger 1993; 155(41): 3299-3301
[6] McKenna WJ, Kleinebenne A, Nihoyannopoulos P, et al. Echocardiographic measurement of right ventricular wall thickness in hypertrophic cardiomyopathy: relation to clinical and prognostic features. J Am Coll Cardiol 1988; 11:351-58
[7] Maron BJ, McIntosh CL, Klues HG, et al. Morphologic basis for obstruction to right ventricular outflow in hypertrophic cardiomyopathy. Am J Cardiol 1993; 71(12):1089-94
[8] Van Noorden S, Olsen EGJ, Pearse AGE. Hypertrophic obstructive cardiomyopathy: a histological, histochemical and ultrastructural study of biopsy material. Cardiovasc Res 1971; 5:118-31
[9] Matsuura H. Hypertrophic cardiomyopathy complicated with ventricular aneurysm and myocardial necrosis. J Nucl Med 1993; 34:2227-35
[10] Maron BJ, Wolfson JK, Epstein SE, et al. Intramural ("small vessel") coronary artery disease in hypertrophic cardiomyopathy. J Am Coll Cardiol 1986; 8:545-57
[11] Tanaka M, Fujiwara H, Onodera T, et al. Quantitative analysis of narrowings of intramyocardial small arteries in normal hearts, hypertensive hearts, and hearts with hypertrophic cardiomyopathy. Circulation 1987; 75:1130-39
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