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Ann Thorac Surg 1999;68:100-104
© 1999 The Society of Thoracic Surgeons
a Division of Cardiovascular Diseases and Internal Medicine, and Section of Cardiovascular Surgery, Mayo Clinic and Mayo Foundation, Rochester, Minnesota, USA
Address reprint requests to Dr Nishimura, Division of Cardiovascular Diseases and Internal Medicine, Mayo Clinic, 200 First St SW, Rochester, MN 55905
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Abstract |
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 Top Abstract IntroductionPatients and methodsCommentReferences |
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Methods. Of patients referred for treatment of HOCM, 4 had fixed LVOT obstruction. Clinical and echocardiographic data and surgical findings were reviewed.
Results. In the 4 patients with clinical features consistent with HOCM or HOCM-like conditions, echocardiography showed fixed LVOT obstruction with an early-peaking LVOT Doppler signal or absence of severe systolic anterior motion of the mitral valve. The causes of fixed obstruction included accessory mitral tissue with associated fibrous ring (1 patient), fixed subaortic tunnel stenosis (2 patients), and a discreet subaortic ridge (1 patient). After surgical relief of the fixed LVOT obstruction, all patients had relief of the ventricular outflow tract gradient.
Conclusions. Not all patients with a presumed diagnosis of HOCM have isolated dynamic LVOT obstruction but may have isolated or additional fixed obstruction. Careful two-dimensional and Doppler echocardiography are needed to identify this subset of patients who are best treated surgically.
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Introduction |
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TopAbstractIntroductionPatients and methodsCommentReferences |
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Treatment modalities are aimed at decreasing this dynamic outflow obstruction [2]. Medical therapy includes ß-antagonists, calcium antagonists, and disopyramide, whose effect is due partly to depression of myocardial contractility [3, 4]. However, a subset of patients remains symptomatic despite intensive medical therapy. Recently, dual-chamber pacing has been proposed as a treatment for these patients. Implantation of a permanent pacemaker has been shown to decrease the outflow gradient and to relieve symptoms in selected patients [5–7]. Although the mechanism is not clear, it may be related acutely to dyssynchronous contraction of the septum and, long-term, to a remodeling effect, both of which interrupt the pathophysiologic sequence of events that lead to the dynamic LVOT obstruction. Traditionally, septal myectomy has been the definitive treatment for severely symptomatic patients whose condition is refractory to more conservative measures.
When initiating therapy for patients presenting with the presumed diagnosis of HOCM, it is important to recognize that a subset of patients may have fixed rather than dynamic LVOT obstruction. These patients are not expected to benefit from medical treatment or dual-chamber pacing, but rather require an operation to remove the anatomic obstruction. We describe 4 patients referred to our medical center with the presumed diagnosis of HOCM in whom fixed LVOT obstruction was present.
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Patients and methods |
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TopAbstractIntroductionPatients and methodsCommentReferences |
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On physical examination, a mid-peaking ejection systolic murmur (grade 4/6) was heard at the base and apex, increasing in intensity from a squatting to a sitting position.
Transthoracic echocardiography demonstrated LVOT obstruction due to accessory mitral valve tissue in association with a discrete subaortic stenosis (Figs 1A, 1B). The major proportion of the gradient was due to a fixed subaortic stenosis, with high velocity of an early- to mid-peaking contour. In addition, systolic anterior motion of the mitral valve was noted, and concomitant dynamic outflow obstruction was seen as a separate late-peaking velocity in the LVOT (Fig 1C). The total gradient was 130 mm Hg. In view of the severe fixed LVOT obstruction, operation was recommended.
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Histologic examination of the resected subaortic ring revealed dense white connective tissue. There was moderate myocyte hypertrophy and severe endocardial thickening associated with pericellular interstitial fibrosis in the tissue obtained from the septal myectomy. The mitral valve accessory tissue was dysplastic, with diffuse fibrosis and myxoid change.
The postoperative course was uneventful, and the patient was dismissed on the 7th postoperative day on a regimen of metoprolol indefinitely. At follow-up 6 months later, the patient was well; retrospectively, she admitted to moderate limitation of activity before the operation and was now completely asymptomatic. A mild residual 20 to 25 mm Hg gradient was present across the LVOT.
Patient 2
A 59-year-old woman was referred with a diagnosis of HOCM. She had had symptoms of exertional lightheadedness for several years and, more recently, had noted increasing shortness of breath. Initially, treatment with ß-blockers was instituted but withdrawn because of intolerance. A dual-chamber pacemaker was implanted, without improvement in symptoms.
On physical examination, an ejection systolic murmur (grade 2/6), which increased in intensity from a squatting to a standing position, was heard at the base and apex.
Transthoracic echocardiography demonstrated normal left ventricular size, with global hyperdynamic function. Although septal hypertrophy was prominent, there was no systolic anterior motion of the mitral leaflet, and only mild mitral regurgitation was identified. The mitral valve leaflets were thickened and densely calcified. The LVOT was narrowed. A high velocity of 5 m/s was found across the LVOT obstruction, yielding a gradient of 100 mm Hg. Transesophageal echocardiography demonstrated a fixed tunnel stenosis, with a secondary dynamic outflow gradient (Fig 2). An operation was recommended.
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The postoperative course was uneventful. Repeat echocardiography showed no residual LVOT gradient. The patient was dismissed on the 5th postoperative day. Cardiac medications at dismissal were procainamide and digoxin for 6 weeks. At follow-up, her symptoms had improved.
Patient 3
A 53-year-old woman was referred for consideration of dual-chamber pacing for HOCM. The diagnosis of HOCM had been made recently after an evaluation for a heart murmur. Although there was no previous history of cardiac disease, she had had a 20-year history of progressive dyspnea on exertion, attributed to severe chronic obstructive pulmonary disease. Work-up at her local hospital included transthoracic echocardiography, which revealed severe left ventricular hypertrophy with a 50-mm Hg LVOT gradient. Comorbid conditions included hypertension treated with a calcium blocker, significant chronic obstructive pulmonary disease, and obesity. The family history was unremarkable. Her medications included verapamil (240 mg daily), ß2-agonist and steroid inhalers, potassium supplementation, and estrogen. Clinical examination revealed an ejection systolic murmur (grade 3/6) present along the left sternal border.
A temporary dual-chamber pacing study was performed in the cardiac catheterization laboratory. The resting LVOT gradient was greater than 100 mm Hg, and there was no change in the gradient with dual-chamber pacing at any AV interval. The original transthoracic study was reviewed, and it was noted that the lack of systolic anterior motion of the mitral valve seemed inconsistent with the severity of the LVOT obstruction. Transesophageal echocardiography revealed the presence of a discrete tunnel subaortic stenosis and a discrete subvalvular ridge (Fig 3). An operation was recommended.
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The postoperative course was complicated by a complete heart block, for which a permanent pacemaker was implanted. The patient was dismissed on the 11th postoperative day with no cardiac medications prescribed. At follow-up, she was active and her symptoms had completely resolved.
Patient 4
A 44-year-old woman was referred for evaluation of HOCM. Six years previously, after evaluation for exertional chest tightness, a diagnosis of HOCM was made by echocardiography. Treatment with ß-blockade was limited by side effects, and calcium blockers did not control her symptoms. Consequently, treatment with disopyramide was instituted. During the preceding year, a significant and progressive increase in symptoms developed. Cardiac catheterization revealed an LVOT gradient of 120 mm Hg. There was no mitral regurgitation on ventriculography, and the results of coronary angiography were normal. The past medical history was unremarkable. Medications included disopyramide (150 mg daily), indapamide, and potassium supplementation.
On physical examination, a loud, harsh ejection systolic murmur (grade 3/6) was present at the base and apex. There was no change in intensity of this murmur from a squatting to a standing position.
Transthoracic echocardiography showed asymmetrical septal hypertrophy (measuring 20 mm). The mitral valve was redundant and thickened, with mild central mitral regurgitation. No systolic anterior motion of the mitral valve was detected. An echodense linear density was noted in the LVOT, and there was a high-velocity flow of 6 m/s, with an early-peaking contour (Fig 4). An operation was recommended.
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The postoperative course was uneventful. Repeat echocardiography confirmed no resting LVOT gradient and only mild mitral regurgitation. The patient was dismissed on the 7th postoperative day with no cardiac medications prescribed. At follow-up, her symptoms had resolved entirely and she had unlimited effort tolerance.
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Comment |
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TopAbstractIntroductionPatients and methodsCommentReferences |
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Two-dimensional and Doppler echocardiography may be useful in identifying fixed obstruction in patients with a diagnosis of HOCM or HOCM-like conditions. The absence of systolic anterior motion of the mitral valve or a disproportionately less degree of systolic anterior motion of the mitral valve for the degree of the left ventricular outflow gradient suggests a fixed rather than a dynamic cause for the obstruction. Another clue is the presence of an early- versus a late-peaking LVOT Doppler signal. In fixed obstruction, the obstruction to flow is maximal early on and constant throughout systole. Therefore, the velocity profile is early-peaking. This is in contrast to the late-peaking velocity profile seen in dynamic obstruction.
Not all patients with a presumed diagnosis of HOCM truly have isolated dynamic LVOT obstruction but may have fixed obstruction as a primary process (HOCM-like condition) or secondary to the fibrotic reaction at the systolic anterior motion of the mitral leaflet-septal contact (primary HOCM). Careful two-dimensional and Doppler echocardiography are essential in identifying this subset of patients. These patients with fixed obstruction need to be identified because the best treatment for them is surgical correction.
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References |
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TopAbstractIntroductionPatients and methodsCommentReferences |
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This article has been cited by other articles:
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  P. G. Masci, F. Rossi, and F. Chiarella Discrete subaortic stenosis in elderly women Eur J Echocardiogr, January 1, 2008; 9(1): 63 - 64. [Abstract] [Full Text] [PDF]
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 J. M. Oliver, A. Gonzalez, P. Gallego, A. Sanchez-Recalde, F. Benito, and J. M. Mesa Discrete subaortic stenosis in adults: increased prevalence and slow rate of progression of the obstruction and aortic regurgitation J. Am. Coll. Cardiol., September 1, 2001; 38(3): 835 - 842. [Abstract] [Full Text] [PDF]
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