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Ann Thorac Surg 1995;59:263-264
© 1995 The Society of Thoracic Surgeons
Institute of Clinical Medicine, University of Tsukuba, Tsukuba 305, Japan
To the Editor:
Idiopathic enlargement of the right atrium (IERA) generally is considered to be congenital in origin [1–5]. In the previously reported cases, the most common rhythm is normal sinus rhythm with some cases of atrial arrhythmias reported [2–6]. Here we describe a case of IERA associated with dermatomyositis of adult onset in which the right atrium was at a complete standstill and unexcitable. We also discuss the relations between IERA and dermatomyositis.
A 51-year-old housewife was admitted to the hospital because of progressive weakness of the proximal limb muscles for 15 years. At the age of 37 years she underwent pacemaker implantation for bradycardia. She complained of dysphagia and difficulty in walking, and noticed dyspnea even with slight exertion for the last several years.
The clinical features, muscle biopsy, and electromyogram were consistent with the diagnosis of primary idiopathic dermatomyositis. A biopsy specimen obtained from the biceps brachi revealed degeneration and necrosis of muscle fibers, interstitial infiltration with monocytes, and perivascular infiltrates of inflammatory cells such as lymphocytes and plasma cells (Fig 1
).
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The diagnoses were IERA, atrial standstill, and primary idiopathic dermatomyositis. To increase cardiac output, dual-chamber pacing and excision of the right atrium were performed on November 27, 1986. Through a median sternotomy, the pericardium was adherent to the markedly enlarged and dilated right atrium. The other chambers were not remarkable. Atrial electrical activity measured with epicardial electrodes was absent. Atrial pacing was attempted at multiple sites as high as 10 V and 20 mA with no response. A large portion of right atrial wall was excised, and two epicardial leads were placed on the right ventricle for ventricular pacing. Section of the wall of the right atrium revealed that the epicardium was fibrotic diffusely and muscle fibers were scarce. Infiltration of inflammatory cells was not observed (Fig 2).
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Idiopathic enlargement of the right atrium generally is considered a congenital abnormality [1–5]. Pathohistologic appearance has been variable; the findings have included hypertrophy of muscle fibers, irregular thickness and loss of striation of muscle fibers, widely separated muscle fibers with no other abnormalities, and lipomatous degeneration [2, 4]. Electrophysiologically, the P waves usually were normal in IERA [1]. Supraventricular arrhythmias such as coronary sinus rhythm, atrial flutter, paroxysmal atrial tachycardia, and atrial premature beats also existed on some occasions [2–5]. The case presented herein is of interest in that the atrial electrical activity was absent with fibrotic atrial myocardium.
We speculate that fibrotic myocardium in IERA in this case may be the result of postinflammatory fibrosis in the atrium. This case adds to a fairly sizable preexisting literature on the clinical entity of right atrial standstill. Atrial standstill has been noted in three clinical settings, one of which is underlying neuromuscular disease [7]. The association between heart disease including atrial standstill and muscular dystrophy also has been documented [8]. The dermatomyositis and the postinflammatory fibrosis in the atrium may be a related syndrome that affected different organ systems at different times. The fact that the patient's clinical symptomatology of muscle weakness dated back 15 years and actually preceded the implantation of a pacemaker also supports our speculation.
We conclude that the etiology of IERA may not be uniform. In this case IERA presented a clinical feature of permanent atrial standstill associated with dermatomyositis. Excision of the enlarged right atrium and ventricular pacing controlled the heart failure well.
References
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