Ann Thorac Surg 1998;65:537
© 1998 The Society of Thoracic Surgeons
Case Reports
Tricuspid Valve Repair in a Mountaineer
Adrian J. Marchbank, FRCS,
Dinah V. Parums, MRCPath,
Stephen Westaby, FRCS
Oxford Heart Centre, John Radcliffe Hospital, Oxford, United Kingdom
Accepted for publication September 11, 1997.
Mr Marchbank, Oxford Heart Centre, John Radcliffe Hospital, Headley Way, Headington, Oxford, OX3 9DU, United Kingdom (e-mail: 100407.1052@compuserve.com).
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Abstract
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Lord Hunt of Everest presented with aortic stenosis but predominant right ventricular failure. He was found to have signs of pulmonary hypertension with a dilated right ventricle, severe tricuspid regurgitation, and right atrial hypertrophy in the absence of elevated pulmonary artery pressures. He is a lifelong mountaineer and we attribute these findings to intermittent prolonged exposure to high altitude.
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Introduction
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Acclimatization to high altitude is associated with transient elevation of pulmonary arterial pressure. This is reversible upon return to low altitude, allegedly with no long-term sequelae. We report the case of Lord Hunt of Everest, the team leader for the first successful ascent of Mount Everest in 1953 (Fig 1), who spent long periods of his life at high altitude. We suggest that intermittent exposure to chronic hypoxia for much of his life led to permanent structural changes in the right heart. These findings are similar to those of chronic pulmonary hypertension, but without elevated pulmonary artery pressures at sea level.
Lord Hunt presented at 85 years of age with rapidly worsening breathlessness on exertion, paroxysmal nocturnal dyspnea, and peripheral edema despite treatment with digoxin, diuretics, and warfarin (New York Heart Association class III). There was no history of angina or syncope. He was in chronic atrial fibrillation and had been diagnosed as suffering from myelodysplasia on bone marrow biopsy. On examination he was in atrial fibrillation, blood pressure was 105/80 mm Hg, jugular venous pressure was elevated with a prominent v wave, and there was bilateral peripheral edema to the tops of his thighs. He had easily palpable peripheral pulses, although the carotid pulse had a slow upstroke. There was cardiac enlargement and auscultatory signs consistent with aortic stenosis and tricuspid regurgitation. He had bilateral basal crepitations and tender hepatomegaly. The serum creatinine level was elevated at 182 µmol/L. Echocardiography confirmed aortic stenosis with a Doppler-derived gradient of 50 mm Hg. There was left ventricular hypertrophy but with good overall function. The right ventricle was grossly enlarged with severe tricuspid regurgitation through a dilated annulus. Cardiac catheterization showed aortic stenosis with mild regurgitation. The valve was not crossed. Pulmonary artery pressures were 32/14 mm Hg (mean, 22 mm Hg) and the mean pulmonary wedge pressure was 20 mm Hg (v wave, 28 mm Hg).
At operation, there was only moderate aortic stenosis with a bicuspid aortic valve. The right atrium and right ventricle were greatly enlarged and dilated. Pulmonary artery pressures were not elevated, but there was severe tricuspid regurgitation. The aortic valve was replaced with a bioprosthesis, and a tricuspid annuloplasty was performed. The right atrium was hypertrophic and heavily trabeculated.
Postoperatively oliguria developed, but he recovered uneventfully. Six months later he had returned to New York Heart Association class I and was able to walk 6 to 8 km. Mild to moderate tricuspid regurgitation persisted, but with minimal peripheral edema. Echocardiography showed a persistently dilated right heart and well-preserved left ventricular function.
A right atrial biopsy demonstrated myocyte hypertrophy with cells measuring up to 25 µm in diameter (normal, 12 to 15 µm). There was myocytolysis without necrosis and diffuse interstitial fibrosis, which was predominantly pericellular. Although occasional mononuclear cells were seen there was no myocarditis. No amyloid, fatty change, or iron was present. Vessels were normal without vasculitis, medial changes, occlusion, or thrombus. The appearances were those of chronic right atrial hypertrophy, dilatation, and ischemia, and were consistent with chronic pulmonary hypertension.
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Comment
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At high altitude, the atmospheric pressure is reduced proportionally to the elevation. Correspondingly the partial pressure of oxygen is reduced so that at 8,840 m (equivalent to the summit of Mount Everest) the atmospheric pressure is 240 mm Hg, with an oxygen tension of 50 mm Hg. Acclimatization to altitude occurs over a period of days to weeks and involves a series of physiologic changes to adapt to the reduced oxygen tension and minimize consequent circulatory disturbances. Oxygen carriage capacity is augmented by stimulation of erythrocyte production and ventilation is stimulated to increase the minute volume. Circulatory changes include an increase in cardiac output and pulmonary artery pressure.
These physiologic changes were elegantly demonstrated during Operation Everest II, when a team of volunteers underwent a prolonged period at simulated high altitude with comprehensive invasive monitoring. Serial hemodynamic measurements were obtained at altitudes of up to 8,840 m (atmospheric pressures of 240 mm Hg) and showed pulmonary artery pressure and pulmonary vascular resistance increased both at rest and during exercise. The elevation in pulmonary artery pressure was unresponsive to inspired oxygen in the short term, suggesting that some structural alteration in the pulmonary vasculature had occurred [1]. Animal experiments have shown that the degree of elevation of pulmonary artery pressure is proportional to the increase in altitude and that the changes are reversible upon removal from the hypoxic environment [2].
Changes in the pulmonary vasculature have been proposed to account for this finding. There is a marked species variation in the development of pulmonary arterial smooth muscle hypertrophy during acclimatization to altitude. The degree of pulmonary artery wall thickening is proportional to the level of pulmonary artery hypertension [3]. Residents of great altitude have thicker pulmonary arterial musculature than those of low altitude [4]. Interestingly the yak [5] and llama [6], which are both indigenous to high altitude, have thin-walled vessels with little muscle in their walls. It is also likely that the age at which subjects are first exposed to high altitude is related to the eventual degree of pulmonary artery smooth muscle hypertrophy. Infant rats show greater pulmonary vascular changes than adults, although the degree of developed pulmonary artery hypertension is the same [7]. Natives of high altitude also have greater right ventricular mass than those from sea level, but this phenomenon may be reversible [8].
Lord Hunt presented with moderate aortic stenosis but with gross right-sided changes and severe tricuspid regurgitation with normal pulmonary artery pressure. There was histologic evidence of right atrial hypertrophy, suggesting that the pulmonary artery pressure may have been elevated previously. There was no angiographic evidence to suggest pulmonary thromboembolism or chronic vascular occlusion. There was no suggestion of chronic mountain sickness, which is known to be associated with persistently elevated pulmonary artery pressure. The severity of his aortic stenosis (and left ventricular hypertrophy) was insufficient to account for the tricuspid regurgitation and right atrial hypertrophy. Lord Hunt had lived intermittently at high altitude during the preceding 60 years, and there can be few white men who have spent so much time at such considerable altitude. It is our hypothesis that he must have sustained periods of pulmonary hypertension during repeated acclimatization, and that this led to tricuspid regurgitation and right atrial hypertrophy. The coincidentally bicuspid aortic valve and the onset of biventricular failure led to operation. Although hypoxia-induced pulmonary hypertension is usually reversible, we suggest that intermittent prolonged exposure can lead to irreversible changes in the right heart.
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References
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- Groves BM, Reeves JT, Sutton JR, et al. Operation Everest II: elevated high-altitude pulmonary resistance unresponsive to oxygen. J Appl Physiol 1987;63:521-530.[Abstract/Free Full Text]
- Widimsky J, Ostadal B, Urbanova D, Ressl J, Prochazka J, Pelouch V Intermittent high altitude hypoxia. Chest 1980;77:383-389.[Abstract/Free Full Text]
- Tucker A, McMurtry IF, Reeves JT, Alexander AF, Will DH, Grover RF Lung vascular smooth muscle as a determinant of pulmonary hypertension at high altitude. Am J Physiol 1975;228:762-767.[Abstract/Free Full Text]
- Moret P, Covarrubias E, Coudert J, Duchosal F Cardiocirculatory adaptation to chronic hypoxia. 3. Comparative study of cardiac output, pulmonary and systemic circulation between sea level and high altitude residents. Acta Cardiol 1972;27:596-619.[Medline]
- Heath D, Williams D, Dickinson J The pulmonary arteries of the yak. Cardiovasc Res 1984;18:133-139.[Medline]
- Harris P, Heath D, Smith P, et al. Pulmonary circulation of the llama at high and low altitudes. Thorax 1982;37:38-45.[Abstract/Free Full Text]
- Tucker A, Migally N, Wright ML, Greenlees KJ Pulmonary vascular changes in young and aging rats exposed to 5,486 m altitude. Respiration 1984;46:246-257.[Medline]
- Sizemore DA, McIntyre TW, Van Liere EJ, Wilson MF Regression of altitude-produced cardiac hypertrophy. J Appl Physiol 1973;35:518-521.[Free Full Text]
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Abstract
Introduction
