And Its Obstructive Form, Idiopathic Hypertrophic Subaortic Stenosis (IHSS), in Pediatrics
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Asymmetric septal hypertrophy (ASH) and its obstructive form, idiopathic hypertrophic subaortic stenosis (IHSS), in pediatrics ALBERT K. HARVEY, DD. Oklahoma City, Oklahoma IHSS. The father had no siblings, but two uncles had Although idiopathic hypertrophic died suddenly of heart disease at early ages. subaortic stenosis usually occurs in Case 1 adults, the possibility of its presence in children must not be overlooked. It An 18-year-old white girl said she had not experienced dyspnea, exercise intolerance, syncope, or chest pain. She has been reported even as early as was a senior in high school and had participated in dra- infancy and in stillborn fetuses. The matic and athletic activities. Physical examination condition appears to be genetically showed the pulse rate to be 74 and the blood pressure transmitted, with the natural history 110/64 mm. Hg. Pulses on the upper and lower ex- one of progressive disease. The tremities were strong and symmetric. The point of atypical location of an aortic stenosis maximum intensity (PMI) was not enlarged, and no type murmur is a clue to early thrill or precordial heave was perceptible. There was a diagnosis. Echocardiography is Grade 2/6 harsh systolic ejection murmur along the lower confirmative of a diagnosis. Four case left sternal border, which was transmitted well to the reports are presented. apex. No diastolic component was present. The phono- cardiogram showed an intermittent fourth heart sound. An x-ray film of the chest showed the heart size and vascularity of the lung field to be normal. An elec- trocardiogram (EKG) revealed left ventricular hyper- trophy with marked ST and T wave changes in the left precordial leads. The echocardiogram showed abnormal Idiopathic hypertrophic subaortic stenosis (IHSS) systolic anterior motion of the mitral leaflet, with partial is a subaortic obstruction of the left ventricular narrowing of the outflow tract, but septal thickness could outflow tract secondary to hypertrophy of the not be delineated well for measurement. Cardiac ventricular septum and systolic anterior motion of catheterization was performed, and a pressure gradient the mitral valve. The entity has been known also as of 10 mm. Hg between the left ventricle and the aorta at hypertrophic obstructive cardiomyopathy, func- rest was slightly elevated. When isoproterenol was used tional aortic stenosis, and muscular subaortic as a provocative agent, the patients heart rate increased stenosis, but a more appropriate term for the from the resting state of 82 to 143 per minute, and the anatomic abnormalities of IHSS is asymmetric sep- gradient increased from 10 to 59 mm. Hg with little tal hypertrophy (ASH). The condition usually is change in systemic blood pressure. Provocation testing seen in adults, but has been reported in stillborn with amyl nitrite inhalation did not show a change in gradient. The resting end-diastolic pressure was in the fetuses, infants, children, and adolescents. The four high normal range at 16 mm. Hg. Biplane cineangiog- cases of IHSS in adolescence to be presented here rams showed a hypercontractile left ventricle, with oblit- illustrate the wide variability in clinical presenta- eration of the apical portion of the ventricular cavity. The tion. aortic and mitral valves appeared normal. The left ventricular wall was considerably thickened, and there Report of cases was a conic, or funnel-like, area beneath the aortic valve Cases 1 and 2 which decreased symmetrically in caliber to the level of Two adolescent girls, sisters aged 13 and 18, were re- the mitral area. These observations pointed to IHSS with ferred to the Michigan State University Pediatric car- mild obstruction during rest and a significant obstruc- diology clinic because of a family history of IHSS. Their tive gradient on isoproterenol stimulation. father had had cardiac surgery for left ventricular out- flow tract obstruction at age 35 and had been able to Case 2 carry on his duties as a minister without serious symp- A 13-year-old white girl was the youngest of three chil- toms until his sudden death at age 49. Autopsy showed dren. She gave no history of chest pain, dyspnea, palpita- Idiopathic hypertrophic subaortic stenosis 176/57 tions, or syncope. Physical examination showed her blood father, now aged 65, had been hospitalized at age 26 for pressure to be 110/58 mm. Hg, with equal pulses on both what he called an enlarged heart. However, he went on to the upper and lower extremities. The lungs were clear to play professional football after hospitalization with no auscultation. The PMI was full and in the fourth inter- adverse effects. At the time of his sons admission, the costal space. No thrill was palpable. Cardiac ausculta- father said he had had occasional dizzy spells, syncopal tion revealed a Grade 3/6 high-pitched blowing regurgit- episodes, dyspnea, and chest pain, but had not seen a ant systolic murmur, which was heard best at the left physician for these symptoms. His echocardiogram was lower sternal border and apex, with radiation to the consistent with nonobstructive ASH and calcific aortic axilla and upper left sternal border. There was no di- stenosis. astolic murmur. An x-ray film of the chest showed a mild Physical examination of the patient at admission to enlargement of the cardiothoracic diameter and normal Ingham Medical Center showed his pulse rate to be 80, pulmonary vascularity. The EKG showed left ventric- respiration rate 30, and the blood pressure 104/60 mm. ular hypertrophy, left atrial hypertrophy, and ST and Hg. The patient was semicomatose and unresponsive to T wave changes. Cardiac catheterization was performed verbal stimulation, but responded appropriately to tac- and showed a gradient of 80 mm. Hg on pullback from tile and painful stimulation. His level of consciousness the left ventricle to the aorta. There was no gradient varied from severe CNS depression to agitation. His skin across the aortic valve. Moderate elevation of the left was pale and diaphoretic. The Grade 4/6 holosystolic ventricular end-diastolic pressure was present. No pro- murmur was still present. All peripheral pulses were vocative tests were performed. Cineangiography showed palpable, but weak and thready. There was no evidence moderate enlargement of the left ventricle, prominent of cyanosis, clubbing, or petechial hemorrhages of the papillary muscles, and reduction in the left ventricular nail beds. Deep tendon reflexes were equal and symmet- cavity during systole. A linear translucent area was ric. Babinskis signs were not present. There was no present along the left ventricular outflow tract below evidence of paralysis. The cranial nerves appeared to be the level of the aortic valve. Mild mitral regurgitation intact. The cardiac monitor showed markedly irregular was noted with dilatation of the left atrium. These rhythm, consisting mainly of junctional ectopic beats observations were consistent with a diagnosis of IHSS and occasional premature ventricular contractions with obstruction of the left ventricular outflow tract at (PVCs). Because it was difficult to maintain the blood rest and mild to moderate mitral regurgitation. Pro- pressure, a Neo-synephrine intravenous drip was given pranolol therapy was initiated. until the systolic blood pressure reached 110 mm. Hg. In an attempt to decrease myocardial contractility and pos- Case 3 sibly reduce the outflow obstruction, the patient was A 12-year-old white boy had lost consciousness while given propranolol intravenously in a dose of 4 mg. every playing basketball and started having generalized con- 6 hours. The following morning his vital signs, cardiac vulsions. He was transferred unconscious to Hurley Med- rhythm, and mental status were markedly improved. ical Center in Flint, Michigan. A complete blood count Approximately 36 hours after admission, the patient and measurement of arterial blood gases gave results started having bradycardia with frequent PVCs. The within normal limits. The pulse was regular at 28, and rhythm improved when atropine was given intrave- the blood pressure was 130/80 mm. Hg. Physical exam- nously. On the same day cardiac catheterization was ination showed a Grade 4/6 holosystolic murmur with a performed and showed marked bilateral ventricular quadruple rhythm, which was loudest on auscultation at hypertrophy with large pressure gradients between the the left lower sternal border and at the apex. The chest ventricles and outflow tracts bilaterally in the range of was asymmetric with prominence of the left chest wall 100 mm. Hg. In an attempt to relieve the obstruction of and a palpable heave and thrill over the left precordium. the left ventricle, 6 mg. of propranolol was injected intra- A chest x-ray film showed massive enlargement of the venously during the procedure, but this therapeutic trial heart with normal pulmonary vasculature. The EKG did not seem to relieve the outflow tract obstruction. showed marked left ventricular hypertrophy and bilat- Intravenous administration of Neo-Synephrine was nec- eral atrial hypertrophy. Echocardiography showed a essary to maintain systemic pressure. massive ventricular septum and marked systolic an- On the third day emergency surgical intervention was terior motion of the mitral valve. Premature closure of performed. Extracorporeal circulation and copotassium the aortic valve provided further evidence of severe cardioplegia were used during the procedure. Left obstructive IHSS. The patient was transferred to the ventricular septal myectomy by the transaortic route pediatric cardiology service at Ingham Medical Center, was done in an attempt to relieve obstruction of the left Lansing, Michigan. ventricular outflow tract. Relief of obstruction of the The pertinent past history included periodic chest pain right ventricular outflow tract was accomplished by and dyspnea for 2 years prior to admission. However, at right ventricular septal myectomy and reconstruction of no time had these symptoms been severe enough to pre- the outflow tract with a dacron patch. An intra-aortic vent him from being active in sports. Because of these balloon pump was inserted before the patient left the symptoms, a cardiovascular examination had been per- operating room.