Initial electrocardiography showed 2nd-degree AV block with a 2:1 AV conduc- ... A temporary ventricular pacemaker, placed via the right internal jugular vein,.
Case Reports
Hypertroph ic Card iomyopathy Presenting with 3rd-Degree Atrioventricular Block
Kerry L. Rosen, MD Robert W. Cameron, MD Peter J. Bigham, MD Steven R. Neish, MD
A 15-year-old boy presented with exercise intolerance and near syncope. Electrocardiography showed 3rd-degree atrioventricular block. He was treated emergently with temporary transvenous ventricular pacing. Two-dimensional echocardiography revealed hypertrophic cardiomyopathy Subsequently, a permanent, transvenous, dual-chamber pacemaker was implanted. Hypertrophic cardiomyopathy rarely causes complete atrioventricular block. It is particularly unusual for the presenting symptoms of hypertrophic cardiomyopathy to be caused by atrioventricular block. The case report is followed by a review of the pediatric literature on hypertrophic cardiomyopathy with atrioventricular block. (Tex Heart Inst J 1997;24:372-5)
momplete atrioventricular (AV) block, although a rare complication of hypertrophic cardiomyopathy (HCM), has been reported in patients of all ages with HCM.'7 The reports include cases of familial HCM in which affected family members have developed spontaneous, complete AV block.3'4 While the etiology of AV conduction disorders in HCM is unclear, some patients require permanent pacemaker implantation to treat them. Most cases of AV block associated with HCM are reported as complications of the patient's known cardiomyopathy. The following case report describes a previously healthy adolescent whose presentation with complete AV block led to the diagnosis of HCM.
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Case Report Key words: Arrhythmia! etiology; atrioventricular block; cardiac pacing, artificial; cardiomyopathy, hypertrophic; case report; heart block/etiology; heart block/therapy; pacemaker, artificial From: The departments of Pediatrics and Cardiology Service, Fitzsimons Army Medical Center, Aurora, Colorado 80045 The views expressed in this article are those of the authors and do not reflect the official policy of the Department of Defense or other departments of the U.S. Government. Address for reprints: Kerry L. Rosen, MD, MC 2-2280, Division of Cardiology, Texas Children's Hospital, 6621 Fannin Street, Houston, Texas 77030 372
A 15-year-old boy presented to an outlying emergency room with a 2-month history of worsening exercise intolerance and a 2-week history of near syncope, exertional dyspnea, and palpitations. His family history was free of cardiac dis-
and his past medical history was unremarkable. Initial electrocardiography showed 2nd-degree AV block with a 2:1 AV conduction ratio (Fig. 1) before transport to our hospital. On arrival, the patient was markedly short of breath. He was afebrile with a pulse of 40 beats/min, a respiratory rate of 24 breaths/min, and blood pressure of 104/67 mmHg. Physical examination revealed diaphoresis, with marked perioral and peripheral cyanosis. A 2nd electrocardiogram performed at our facility showed 3rd-degree AV block with a ventricular rate of 40 beats/min (Fig. 2). A temporary ventricular pacemaker, placed via the right internal jugular vein, immediately improved the patient's peripheral perfusion and shortness of breath. Echocardiography showed biventricular hypertrophy and biatrial enlargement. In diastole, the interventricular septum was 18 mm thick, while the left ventricular posterior wall measured 9 mm. Because of the unusual presentation and severity of symptoms, cardiac catheterization was performed. The right ventricular systolic pressure was 62 mmHg and the end-diastolic pressure was 16 mmHg. Pulmonary artery pressure was 62/ 37 mmHg, with a mean pressure of 43 mmHg. Mean pulmonary artery wedge pressure was 26 mmHg. Left ventricular systolic pressure was 126 mmHg and enddiastolic pressure was 24 mmnHg. On catheter pullback, there was no systolic gradient between the left ventricle and the aorta. Coronary arteriography was normal. Right ventricular endomyocardial biopsy was performed, and histologic examiease
Hypertrophic Cardiomyopathy and Atrioventricular Block
Volume 24, Number 4, 1997
Fig. 1 Lead V, demonstrates atrioventricular block with a 2:1 conduction ratio and wide ventricular complexes. Large, bi-phasic
p-waves are noted.
Fig. 2 Lead V, during 3rd-degree atrioventricular block demonstrates atrioventricular dissociation and a wide QRS ventricular rhythm.
nation revealed myocardial hypertrophy without myofibril disarray or evidence of acute inflammation. A permanent, dual-chambered pacemaker was implanted and programmed in the DDD mode. Oral verapamil therapy was begun, and at 6-month follow-up the patient was without dyspnea. He had no further near syncope, but continued to have limited exercise tolerance. All of his available immediate family members were screened for HCM, and all had normal echocardiograms.
Discussion Hypertrophic cardiomyopathy is difficult to diagnose by presenting signs and symptoms alone. Children and adolescents usually present with an asymptomatic heart murmur. While as many as 40% of patients with HCM have symptoms at the time of presentation, the symptoms are usually mild. Occasionally, HCM is discovered during the screening of relatives of a patient diagnosed with HCM.8 The incidence of arrhythmias in HCM is well documented. In a review by the Pediatric Electrophysiologic Society9 of 135 children and adolescents with HCM, routine electrocardiography showed arrhythmias in 39/o of the patients. These arrhythmias included atrial fibrillation/flutter, supraventricular tachycardia, AV conduction disease, sinus node disease, and ventricular arrhythmias. Holter monitoring revealed uniform premature ventricular contractions (PVCs) in 31% of the patients, as well as multiform Texas Heart Instituteiournal
PVCs (7%), couplets (7%), and ventricular tachycardia (7%). Maron and associates10 reported the incidence of arrhythmias in 84 patients ages 9 to 65 years with HCM. Fifty-five (65%) of the patients had ventricular couplets, multiform PVCs, or ventricular tachycardia. Also, 10 (12%) of the patients had more than 100 supraventricular premature depolarizations during a 24-hour monitoring period, including 6 patients who had paroxysms of supraventricular tachycardia. McKenna and colleagues'1 studied 6 infants, 14 children, and 33 adolescents with HCM. They found that, while all of the patients had sinus rhythm, 4 of the adolescents had paroxysmal supraventricular tachycardia, 5 of the adolescents had asymptomatic nonsustained ventricular tachycardia, and 1 of the children had Wolff-Parkinson-White syndrome and re-entrant tachycardia. None of these series reported AV-conduction disease. Although the association of AV block and HCM has been reported in adults, it is rare.' In addition, to the best of our knowledge, there are only 6 other reports in the literature of HCM associated with complete AV block in children, adolescents, or young adults (Table I).24-7 In 4 of these cases, the HCM appears to be familial. The lst report of AV block associated with HCM is from Luisada5 in 1965. During a clinic follow-up for headaches, a 10-year-old boy was found to have bradycardia and a systolic ejection murmur. Electrocardiography revealed complete AV block with a ventricular rhythm of 45 beats/min. Catheterization with administration of isoproterenol produced a 27Hypertrophic Cardiomyopathy and Atrioventricular Block
373
TABLE 1. Pediatric Cases of Complete Atrioventricular Block and Hypertrophic Cardiomyopathy Case No.
Year
1
1965
Luisada5
10 y, M
2
1977
Spilkin6
3
1981
4
Author
Age & Sex
Conduction Prior to CAVB
Symptoms
HCM Known*
Catheterization Gradient (mmHg)
Pacemaker
Sinus
Headache
No
0/27**
No
No
20 y, M
Sinus
Dizziness
Yes
64
Yes
Yes***
Maron2
1 day, F
Congenital CAVB
Congestive heart failure
No
0
Yes
Yes
1991
Thongtang4
20 y, M
Sinus
Orthopnea, dyspnea
Yes
ND
Yes
Yes
5
1991
Thongtang4
16y, M
Sinus
Syncope
Yes
70
Yes
Yes
6
1995
Tamura7
10y, F
Sinus
Syncope
Yes
28
Yes
No
7
1997
Rosen
15y, M
2oAVB
Dyspnea, syncope, shortness of breath
No
0
Yes
No
Familial HCM
AVB = atrioventricular block; CAVB = complete atrioventricular block; HCM = hypertrophic cardiomyopathy; ND = no data * HCM known before diagnosis of CAVB. ** Provoked gradient. *Likely familial (16-year-old brother with sudden death).
mmHg provoked gradient from the left ventricle to the aorta, which led to the diagnosis of "subaortic muscular stenosis." At the time of the case report, the patient was without syncope, chest pain, palpitations, or exertional dyspnea. A pacemaker was not implanted. In 1977, Spilkin and associates6 described the case of a 20-year-old man with HCM who subsequently developed complete AV block. The patient presented with a 3-year history of chest pain and dyspnea. His family history included a father with a known heart murmur and a brother whose sudden death at age 16 was attributed to a "leaky heart valve." Initial electrocardiography showed the patient to be in sinus rhythm with a PR interval of 0.2 seconds. Echocardiography revealed hypertrophy of the interventricular septum and systolic anterior movement of the mitral valve. Catheterization findings included a 64-mmHg subaortic gradient and left ventricular "cavity obliteration" on angiography. Six months after initial presentation, the patient was reevaluated for dizzy spells and electrocardiography showed complete AV block with an idioventricular rate of 32 beats/min. A permanent, unipolar, ventricular, inhibited pacemaker was implanted and his symptoms improved. Maron and colleagues2 reported a case of congenital complete AV block and HCM in 1981. The patient was a full-term neonate born to a non-insulin-dependent diabetic mother. The infant had congenital complete AV block, with a heart rate of 40 374
Hypertrophic Cardiomyopathy and Atrioventricular Block
beats/min. The infant developed congestive heart failure at 3 days of age, necessitating placement of an epicardial ventricular pacemaker. Despite ventricular pacing and therapy with digitalis and furosemide, congestive failure worsened and progressed to respiratory failure and eventual death at 2 months. At autopsy, the heart weighed 62 grams (normal weight: 23 grams) and the ventricular septum was disproportionately thickened relative to the left ventricular free wall. Microscopic examination showed marked disorganization of cardiac muscle cells in the ventricular septum and interruption of the penetrating portion of the AV bundle as it coursed through the central fibrous body. Through echocardiographic screening, the infant's father was found to have asymmetric hypertrophy of the ventricular septum. In 1991, Thongtang and coworkers4 described familial HCM associated with spontaneous complete AV block. Brothers, ages 16 and 20 years, with known HCM developed syncope and were found to have complete AV block requiring permanent pacemaker implantation. In 1995, Tamura and associates7 reported a case of a 10-year-old girl with HCM, who received 5 years of follow-up. Her family history was negative for HCM and sudden death. An electrocardiogram recorded 2 months before she presented with AV block showed sinus rhythm at 63 beats/min with a PR interval of 0.16 seconds and a QRS duration of 0.16 seconds. Subsequently, she presented with a 1-day history of a heavy feeling in her chest. ExamiVolume 24, Number 4, 1997
nation revealed an irregular pulse and electrocardiography showed a 2nd-degree AV block with a 2:1 conduction ratio. The patient rapidly lost consciousness as her rhythm degenerated to complete AV block. An emergent temporary ventricular pacemaker was inserted, and she regained consciousness. After stabilization, a permanent dual-chambered pacemaker was implanted, and the patient's symptoms improved markedly. Although the cause of AV block in HCM is unknown, histopathologic reports describe possible causes for the development of conduction abnormalities. In Maron's case2 of congenital AV block and HCM, histopathologic examination of AV nodal tissue was normal. However, continuity of the conduction system was interrupted in the bundle of His as it coursed through the central fibrous body. Other histopathologic reports in patients with HCM and advanced AV conduction disorders have shown interstitial fibrosis or myocardial necrosis in the conduction system,12 and abnormally small intramural coronary arteries with thickened walls and luminal narrowing. 13 This review of the literature shows that the association of AV block and HCM is rare, and that most cases of AV block develop in patients with known HCM. Our case describes a patient whose presentation with AV block led to the diagnosis of HCM. The recognition of HCM in association with AV block is important, as it alters the approach to the treatment of each condition. During long-term follow-up of patients with HCM, it is prudent to monitor for the development of abnormal AV conduction. Atrioventricular block may precipitate congestive heart failure or syncope throughout the course of the disease. Rarely, as in our case, do these symptoms prompt the initial evaluation from which the diagnosis of HCM can be made.
7. 8.
9.
10.
11.
12.
13.
noninvasive correlates with the timing of atrial systole. Circulation 1977;55:418-22. Tamura M, Harada K, Ito T, Enoki M, Takada G. Abrupt aggravation of atrioventricular block and syncope in hypertrophic cardiomyopathy. Arch Dis Child 1995;73:536-7. Paquet M, Hanna BD. Cardiomyopathy. In: Garson A Jr, BrickerJT, McNamara DG, editors. The science and practice of pediatric cardiology. Vol 3. Philadelphia: Lea & Febiger, 1990:1617-46. Garson A Jr. Ventricular arrhythmias. In: Garson A Jr, Bricker JT, McNamara DG, editors. The science and practice of pediatric cardiology. Vol 3. Philadelphia: Lea & Febiger, 1990: 1864-1904. Maron BJ, Savage DD, Wolfson JK, Epstein SE. Prognostic significance of 24 hour ambulatory electrocardiographic monitoring in patients with hypertrophic cardiomyopathy: a prospective study. Am J Cardiol 1981;48:252-7. McKenna WJ, Franklin RC, Nihoyannopoulos P, Robinson KC, Deanfield JE. Arrhythmia and prognosis in infants, children and adolescents with hypertrophic cardiomyopathy. J Am Coil Cardiol 1988;11:147-53. Gavrilescu S, Gavrilescu M, Streian C, Luca C. Hypertrophic obstructive cardiomyopathy associated with complete heart block. Pathologic correlations in a case studied with His bundle electrography. Acta Cardiol 1974;29:241-9. Bharati S, McAnulty JH, Lev M, Rahimtoola SH. Idiopathic hypertrophic subaortic stenosis with split His bundle potentials. Electrophysiologic and pathologic correlations. Circulation 1980;62:1373-80.
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1981;101:857-60. 3. Louie EK, Maron BJ. Familial spontaneous complete heart block in hypertrophic cardiomyopathy. Br Heart J 1986;55:
469-74. 4. Thongtang V, Panchavinin P, Chaithiraphan S. Familial hypertrophic cardiomyopathy associated with spontaneous complete heart block. J Med Assoc Thai 1991;74:301-5. 5. Luisada AA. Sub-aortic muscular stenosis and complete heart block in an adolescent. Pediatric-surgical-cardiac conference case presentation. Chicago Medical School Quarterly 1965;
25(3):169-75. 6. Spilkin S, Mitha AS, Matisonn RE, Chesler E. Complete heart block in a case of idiopathic hypertrophic subaortic stenosis: Texas Hear-t InstituteJournal
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