Filariasis

Bancroftian filariasis is common in some areas of Sri Lanka, causing severe pulmonary hypertension at 16-19 years of age, particularly in females. The capillary wedge pressures remain normal but as the right atrial and pulmonary arterial pressures rise (in some cases reading well over 120 mm Hg), the foramen ovale opens, leading to central cyanosis. If this release mechanism does not operate, fatal right-sided cardiac failure develops. The radiological features are those expected of any form of pulmonary hypertension. The cause is microembolization by circulating microfilaria, and/or the antigenic response this elicits. Fortunately, most filarial infections do not cause pulmonary hypertension at this young age, but pulmonary interstitial fibrosis can occur in the elderly as an end result of filariasis and, if sufficiently severe, pulmonary hypertension may result (See Chapter 26).

Schistosomiasis

Pulmonary hypertension from the pulmonary embolization of schistosome eggs (Fig. 25.2) is discussed in detail in chapter on Schistosomaisis. Some ova reach the lungs via the paravertebral plexus, but the large numbers needed to raise the pulmonary pressure can only reach the lungs after the development of cirrhosis and the resulting portal hypertension collaterals that bypass the liver. When the ova embolize, there is necrotizing arteritis, mediated by the mechanical impact of the eggs as well as by the antigenic response. The result is obstructive and thrombotic lesions in the pulmonary arterioles, which later recanalize and create angiomatoid shunts. These allow an increase in the bronchial circulation, leading to progressive right ventricular enlargement with prominence of the main pulmonary arteries. At the same time there can be damage to the walls of the main pulmonary arteries because the ova embolize and cause thrombosis in the vasa vasorum. The main pulmonary vessels become aneurysmal and are often asymmetrical. The large vessels in the hilum stand out in contrast to the poorly filled peripheral vasculature. Because of the damaged vessels, pulmonary angiography is very hazardous at this stage. CT or MRI scanning is preferable.

Ayerza's disease, described in 'cardiacos negros' (the Bolivian miners with cor pulmonale), is no longer attributed to schistosomiasis but rather to the combination of high altitude and silicosis.

Numerous other parasites have an obligatory or vicarious lung passage, but do not cause pulmonary hypertension. The radiological changes in the lungs, which may be transient and diffuse (often accompanied by eosinophilia), and may be extensive or more focal, do not indicate any change in the hemodynamics of the pulmonary circulation.

Fig. 25.2. Severe pulmonary hypertension with pruning of the peripheral vasculature in a patient with schistosomal pulmonary vascular disease.

Choriocarcinoma (Trophoblastic Disease)

There is a high prevalence of malignant trophoblastic disease in parts of West Africa, Ethiopia, the Philippines, and Southeast Asia. Because this tumor fragments and embolizes the venous system, lung metastases occur early. In some patients massive small emboli obstruct the vascular bed of the lungs sufficiently to cause acute dyspnea and severe pulmonary hypertension. This can be rapidly fatal.

Pyogenic Cholangitis

There may be showers of microemboli from the liver to the lungs as a complication of Oriental pyogenic cholangitis, with resulting pulmonary hypertension (see chapter on Clonorchisis).

Pulmonary Embolism

By contrast with these exotic causes of pulmonary hypertension, pulmonary venous embolism from leg or pelvic veins is infrequent in Africa and elsewhere. Thus, in Nigeria in 2,800 consecutive autopsies only 4.4% had evidence of pulmonary embolism, and of these emboli 21% were caused by choriocarcinoma. In Singapore, of 36,176 autopsies, only 0.08% had fatal pulmonary embolism and in a review of 52,861 major surgical cases there were only five with fatal emboli (0.009%). A similar survey of 5,000 consecutive major surgical procedures carried out on African patients in Bulawayo, Zimbabwe, recorded no postoperative pulmonary emboli. This is a hundredfold less than in some American and European studies.

Malnutrition

In kwashiorkor (severe protein deficiency in infancy - see Chapter 16) the transverse diameter of the heart as measured on radiographs is usually two standard deviations smaller than in age-matched controls; this is confirmed by the small hearts found at autopsy. With treatment and restoration of blood volume, the heart may rapidly enlarge and become normal in size. In kwashiorkor the frontal chest radiograph often also reveals a striking loss of subcutaneous fat, measured at the level of the ninth and tenth ribs. In one series of children it was totally absent in 45% and less than 1 mm thick in 79%, whereas in well-nourished controls the thickness of subcutaneous fat varied from 1.5 to 3 mm.

The classical Oriental beriberi cardiomyopathy, originally recorded from Indonesia, with large, high- output, hyperkinetic hearts and plethoric pulmonary vasculature, is no longer frequent in Southeast Asia. When it does occur it is usually associated with alcoholic malnutrition, and the heart rapidly reduces in size following specific vitamin therapy.

Severe Anemia

There are many causes of anemia which are particular to the tropics and in individual patients there is often more than one, such as malaria, folate deficiency, hookworm disease (Fig. 25.3), or hemoglobinopathy. When the anemia develops slowly, patients compensate even when the level of hemoglobin is 6 grams per 100 ml or lower, provided there is no increased cardiac workload, such as in pregnancy. Radiologically there are no specific features of anemic heart disease. Usually there is generalized cardiac enlargement so that the radiographic silhouette suggests a large pericardial collection of fluid. Cardiac dilatation is greater in children than in adults. There may be prominence of the pulmonary artery because of the high cardiac output, and also some increase in both the pulmonary arterial and venous vasculature. These radiographic features are helpful in excluding pericardial fluid, but sonography will accurately establish the diagnosis. With treatment the dilated heart rapidly returns to a normal transverse diameter, particularly in children.

...

Fig. 25.3. A,B. Severe hookworm anemia in a 7-year-old male, showing the marked change in cardiac shape and size following raising of the level of hemoglobin from 11.8% to 76.5% (see chapter on Ancylostomiasis).