Chagas' Disease: Clinical course, chronic phase

on 11.12.08 with 0 comments

Gradually the patient develops symptoms. These vary greatly from region to region. Lesions of the heart, oesophagus and colon are the most common.

Chronic heart problems

Chronic damage to the heart muscle cells and the cardiac conduction system (including that caused by auto-immune mechanisms) leads to heart failure. There is dyspnoea during exertion, orthopnoea and sometimes paroxysmal nightly dyspnoea, oedema of the feet and ankles, congestion of the neck veins, enlarged liver, crepitations over the base of the lungs. Cheyne-Stokes respiration may occur in advanced heart failure. This phenomenon is characterised by periodic respiration in which apnoea episodes alternate with hyperventilation. It is assumed that the prolonged lung-to-brain circulation time plays a role in Cheyne-Stokes with a long cycle (e.g. 3 minutes) [Other causes of this phenomenon are for example brain stem lesions or compression]. Sometimes there is pulsus alternans: the peripheral arterial pulsations are alternately strong and weak.

The precise physiopathological mechanism is not fully known. The apex of the heart, which is normally situated on the midclavicular line, is displaced to the left. The heart sometimes becomes enormous, which may lead to clot formation in the heart. If blood clots break loose, there may be embolic complications: CVA, ischaemia of limbs, renal infarction. Apical lesions in the left ventricle (wall thinning, intramural bleeding, aneurysms) are typical and occur in approximately 50% of patients. Unlike arteriosclerotic post-infarction aneurysms, in Chagas’ disease the apical cardiac tissue does not consist of scar tissue, the wall is simply thinned. Right ventricular lesions occur in 10 to 20%. Cardiac arrhythmias may cause palpitations, dizziness, syncope and sudden death. On the electrocardiogram a right bundle branch block is often seen, together with a left anterior hemiblock, ventricular extrasystoles, abnormal Q-waves and/or AV-conduction disturbances.

The coronary arteries are normal. A complete left bundle branch block is exceptional, unlike in idiopathic dilated cardiomyopathy. Sudden death is common in people with Chagas’ disease. Probably this is due to ventricular tachycardia which changes suddenly into ventricular fibrillation.

In advanced heart failure, typical radiographic signs may be observed on a chest X-ray: cardiomegaly, prominent hili and distended pulmonary veins in the upper fields, pleural fluid, interstitial pulmonary oedema (fluid in the interlobular septa with Kerley B lines), peribronchial cuffing and finally alveolar pulmonary oedema ("butterfly oedema").

Oesophagus and colon problems

Due to involvement of the small nerves in the oesophagus and colon, peristalsis is reduced and these organs are distended. This occurs in 5 to 10% of seropositive people south of the Amazon, and is virtually absent further north. Trypanosoma cruzi I and II are both associated with cardiac lesions, but apparently intestinal lesions only occur in infection with T. cruzi II (the southern area).

Mega-oesophagus is characterised by difficulty in swallowing (dysphagia), choking, hiccups, nocturnal cough. This often leads to under-nourishment and loss of weight. A clinical aid for detecting delayed oesophageal emptying is to measure the time between swallowing a mouthful of water, and observing the abdominal noises (stethoscope on the epigastrium). Normally this is less than 10 seconds. A distended oesophagus may also be shown on X-ray. The parotid gland may hypertrophy and lead to so-called “cat’s face”.

Mega-colon can lead to pronounced constipation, meteorism, abdominal pain and functional intestinal obstruction (involvement of Auerbach’s myenteric plexus). The abdomen is often distended. Faecaloma, volvulus and peritonitis are complications.

The nervous system

In no other infectious disease is the involvement of the autonomous nervous system so important as in Chagas’ disease. Denervation of the parasympathetic nervous system is better documented and is much more pronounced than denervation of the orthosympathetic system. There can be sensorimotor polyneuritis. There is some hypoaesthesia and paresthesia, but chiefly a reduction or loss of tendon reflexes. The EMG is disturbed. In the central nervous system there is meningo-encephalitis in the acute phase, but the abnormalities in the chronic phase need to be better defined. In flare-up (e.g. AIDS) there may be intracranial hypertension, lesions of the cerebral nerves, paresis, plegia, stupor and convulsions.

The cerebrospinal fluid exhibits a normal number of cells or pleocytosis with predominant lymphocytes and an elevated protein content. At times T. cruzi may even be detected in the cerebrospinal fluid. A CT scan of the brain shows one or more necrotising lesions which may or may not be ring-shaped, with haemorrhages, usually subcortical in the brain hemispheres and occasionally in the cerebellum or the brain stem. T. cruzi lesions rarely occur in the basal nuclei. These clinical pictures should be differentiated from cerebral toxoplasmosis, abscesses, mycoses, tuberculomata or other mycobacterial lesions, metastases or lymphoma.

Category: Medicine Notes



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