The Heart in Cystic Fibrosis
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JOURNAL OF THE ROYAL SOCIETY OF MEDICINE Supplement No. 41 Volume 95 2002 The heart in cystic fibrosis Rowland J Bright-Thomas MRCP AKevinWebb FRCP J R Soc Med 2002;95(Suppl. 41):2–10 SECTION OF PAEDIATRICS & CHILD HEALTH, 27 NOVEMBER 2001 INTRODUCTION 5 PAO2 of approximately 60 mmHg . The predominant site of Cor pulmonale in a patient with fibrocystic disease of the HPV is the small pulmonary arteries, with only a small pancreas was reported by Wiglesworth in 19461. Since this contribution from the pulmonary veins6. This response is time there have been many case reports and articles important in diverting blood away from poorly ventilated to detailing cor pulmonale in cystic fibrosis (CF), although the better ventilated areas, improving the ventilation/perfusion reported prevalence varies. The World Health Organization (V/Q) matching and minimizing arterial hypoxaemia. HPV have defined cor pulmonale as ‘hypertrophy of the right probably regulates blood flow in small units of the healthy ventricle resulting from diseases affecting the function and/ lung where there may be underventilated areas. The or structure of the lung, except when these pulmonary reactivity of the pulmonary circulation to acute hypoxia has alterations are the result of diseases that primarily affect the been shown to vary between individuals in both healthy left side of the heart or of congenital heart disease’2. The subjects and patients with chronic obstructive pulmonary term does not necessarily imply right heart failure but disease (COPD)7,8. the definition is frequently not adhered to. Right ventricular enlargement (which includes right ventricular hypertrophy Remodelling of pulmonary vasculature and dilatation) and right ventricular dysfunction, which may progress to ‘true’ right heart failure are more specific Remodelling of the peripheral pulmonary arterial tree terms3. The aetiology of right ventricular disease in CF is occurs in the presence of chronic alveolar hypoxia. thought to be raised pulmonary artery pressure (PAP) Whether or not HPV is a stimulus for these vascular secondary to chronic or acute-on-chronic hypoxia from the changes is unknown. These changes occur in both chronic progressive lung destruction. hypoxic lung disease and in native healthy subjects exposed This article will focus primarily on pulmonary to the hypobaric hypoxia of high altitudes9. They consist of hypertension (PH) and the subsequent effects on the right muscularization of pulmonary arterioles (less than 80 mmin ventricle (RV) in CF. The studies carried out, investiga- diameter) which normally consist of single elastic lamina tions, treatment options and the questions which remain and are devoid of a muscular coat, proliferation of smooth unanswered in this area will be addressed. Other reported muscle in intima of small pulmonary arteries (80–500 mm cardiac lesions in CF will also be discussed. in diameter), progressive intimal fibrosis and proliferation of vascular smooth muscle in pulmonary veins and venules10,11. RESPONSE OF PULMONARY CIRCULATION TO HYPOXIA Hypoxic pulmonary vasoconstriction Response of the pulmonary circulation in CF The pulmonary circulation responds to alveolar hypoxia by The morphological pulmonary vascular changes in CF are increasing PAP and vascular resistance. Von Euler and similar to that of other hypoxic lung diseases. Symchych Liljestrand first described the phenomenon of hypoxic described muscularization of pulmonary arterioles (Figure pulmonary vasoconstriction (HPV) in the feline pulmonary 1)12. Ryland and Reid studied the hearts and lungs of 36 circulation in 19464. The response, which is present in all children with quantitative morphometric techniques. All mammals, begins within seconds of the onset of hypoxia, patients had some degree of pulmonary artery muscle reaches a maximum within minutes and can be sustained for hypertrophy with peripheral extension of the arterial hours. Graded decreases in alveolar partial pressure of smooth muscle, arterial subintimal fibrosis and thickening oxygen (PAO2) produce similar increases in pulmonary of the wall of pulmonary veins. They also noted the vascular resistance with a threshold for vasoconstriction at disappearance of small branches of the pulmonary arterial system as the disease progresses. In this study the thickness of the muscular wall correlated with the degree of RV Manchester Adult Cystic Fibrosis Unit, North West Lung Centre, Wythenshawe 13 Hospital, Manchester M23 9LT, UK hypertrophy . Correspondence to: R J Bright-Thomas Expansion of the bronchial circulation and the late 2 E-mail: [email protected] development of bronchopulmonary shunts have also been JOURNAL OF THE ROYAL SOCIETY OF MEDICINE Supplement No. 41 Volume 95 2002 Nadas and Shwachman reported on 35 postmortems and, using different criteria, found evidence of overt RV failure in only two cases (6%). At all ages patients with pancreatic fibrosis had a greater cardiac weight relative to body weight than controls and the ratio of RV to left ventricular (LV) wall thickness was higher in the CF group16. The incidence and prognosis of clinical RV failure has varied between studies but a review of necropsies of 37 patients with clinically overt right heart failure found that all patients had RV hypertrophy, 19 had unequivocal RV dilatation and 13 had LV dilatation17. Haemodynamic studies in CF Figure 1 Pulmonary arteriole in cystic fibrosis patient showing muscularization Because of their invasive nature there are few haemo- dynamic studies of the pulmonary circulation and heart in cystic fibrosis. Pulmonary artery hypertension is defined as a resting mean pulmonary artery pressure (mPAP) exceeding 20 mmHg or a systolic pulmonary pressure (sPAP) exceeding 30 mmHg18. Goldring et al. carried out right heart catheterization in 21 CF patients who breathed ambient air and differing oxygen mixtures. They demon- strated that mPAP was abnormally high (22–60 mmHg) in eight of 21 patients. The PAP was correlated with the degree of hypoxia and oxygen returned PAP toward or to normal, without any consistent changes in pulmonary blood flow, wedge pressure or minute ventilation19. Other studies have shown similar results correlating PAP with disease severity and noting a poor prognosis in patients with PH17,20. Pulmonary capillary wedge pressure (PCWP) has been reported as normal in CF patients with PH19,21, but one study of 30 patients with overt RV failure reported a PCWP greater than 12 mmHg in 40%17; and an increase in PCWP has been reported in patients at the time of transplanta- tion22, suggesting that LV dysfunction may occur in end- stage disease. Echocardiographic studies in CF Figure 2 Heart of a cystic fibrosis patient showing right ventricle hypertrophy Echocardiographic studies of both the left and right heart in CF have used various echocardiographic techniques and have frequently only involved small numbers of patients. described in CF, but the significance of this in the 14 Early investigators used M-mode and two-dimensional development of PH is unclear . imaging techniques. More recently, Doppler echocardio- graphy has been used to non-invasively assess right STUDIES OF CARDIAC FUNCTION AND PULMONARY ARTERY PRESSURE IN CF ventricular and PAPs (Table 1). Postmortem studies in CF Pulmonary artery pressure There are few postmortem studies of the heart in cystic sPAP can be estimated using Doppler echocardiography by fibrosis and the reported prevalence of RV dysfunction is measuring the peak velocity of regurgitant blood across the conflicting. Royce examined postmortems of 34 infants and tricuspid valve23,24. This method has been shown to children with CF and found evidence of cor pulmonale correlate closely with invasively measured sPAP24. Another (defined as RV hypertrophy) at necropsy in over 70%15. echocardiographic technique which has been used to 3 JOURNAL OF THE ROYAL SOCIETY OF MEDICINE Supplement No. 41 Volume 95 2002 Table 1 Echocardiographic studies in cystic fibrosis Authors Number of patients Echo method Variables measured Rosenthal et al. 1976 (Ref. 32) 94 M-mode RV dimensions Ryssing 1977 (Ref. 33) 31 2D RV dimensions Gewitz et al. 1977 (Ref. 31) 25 M-mode RV dimensions RV wall thickness Chipps et al. 1979 (Ref. 39) 21 M-mode RV and LV function Septal motion PAP Allen et al. 1979 (Ref. 35) 34 M-mode RV and dimensions RV wall thickness Hirschfeld et al. 1979 (Ref. 91) 30 M-mode RV and LV dimensions PAP Lester et al. 1980 (Ref. 92) 76 M-mode RV and LV function RV wall thickness PAP Jacobstein et al. 1981 (Ref. 40) 10 2D Septal motion Panidis et al. 1985 (Ref. 34) 17 M-mode RV and LV function 2D RV wall thickness Doppler PAP Johnson et al. 1991 (Ref. 41) 25 Doppler LV diastolic function Kucukosmanoglu et al. 1998 (Ref. 36) 26 M-mode RV and LV systolic and 2D diastolic function Doppler RV wall thickness Nedlukova et al. 1999 (Ref. 29) 12 2D RV and LV systolic and Doppler diastolic function PAP Fraser et al. 1999 (Ref. 30) 33 M-mode RV and LV systolic and 2D diastolic function Doppler PAP Florea et al. 2000 (Ref. 27) 103 M-mode Long axis motion 2D RV and LV systolic and Doppler diastolic function PAP Mannarino et al. 2000 (Ref. 28) 42 M-mode RV and systolic and 2D diastolic function Tissue Doppler PAP Ionescu et al. 2001 (Ref. 37) 21 M-mode Long axis motion 2D RV and LV systolic and diastolic function Tissue Doppler RV wall thickness RV=Right ventricle; LV=left ventricle; PAP=pulmonary artery pressure indirectly assess PAP, is the characteristics of flow in the Right ventricular function right ventricular outflow tract where a shortening of the Studies using two-dimensional imaging of the RV in CF pulmonary flow acceleration time is consistent with have given conflicting results. While some authors have PH25,26. PH has been demonstrated in CF patients with reported increased right ventricular dimensions in CF and severe disease by both of these methods27–29 and correlated this with the patients’ clinical score31–33, others patients with PH have been found to have a worse have reported normal RV dimensions in patients with prognosis in one study30.