Cardiovascular Disease in Less-Developed Countries
Burden of cardiovascular disease in less-developed countries
Approximately 80% of the world’s people reside outside Western Europe and Canada/USA. Although cardiovascular diseases (CVD) occur throughout the world, their form and the burden change as a country undergoes economic development. Less-developed countries begin with a disease burden dominated by infectious, perinatal, and nutritional diseases and, in the process of development, make the transition to one dominated by non-communicable disease (NCD), particularly CVD. The four stages of transition are shown in Table 14.1.
Table 14.1 Deaths caused by cardiovascular disease at different stages of development1 | ||||||||||||||||||||||||
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Many less-developed countries have a triple burden of disease, encompassing disorders that characterize the first three phases of the epidemiologic transition.
In 2000, CVD accounted for 16.7 million deaths globally; 31% of all global deaths are due to CVD. Coronary heart disease (CHD) and stroke account for 71% of CVD deaths. Low- and middle-income countries contribute 78% of all CVD deaths, and 86% of disability-adjusted life years’ (DALYs’) loss attributed to CVD. The relative importance of CHD and stroke varies across regions and countries. For example, more than twice
as many deaths from stroke occur in the less developed countries as in developed countries.
as many deaths from stroke occur in the less developed countries as in developed countries.
NCDs rank first in most less-developed countries, in developed countries, and worldwide as a cause of death. CVD accounts for about half of all NCD deaths. In 1990, CVDs were the leading cause of death for all major geographic regions of the developing world except India and sub-Saharan Africa.
There is an early age of CVD deaths in less-developed countries compared to developed countries. In 1990, the proportion of CVD deaths occurring below the age of 70 years was 26.5% in developed countries, compared to 46.7% in less-developed countries. Therefore, the contribution of the less-developed countries to the global burden of CVD, in terms of DALYs lost, was nearly three times higher than that of developed countries.
Rheumatic heart disease (RHD) is the most common cause of CVD in children and young adults in less-developed countries. At least 15.6 million persons are estimated to be to be affected with RHD globally. More than 2 million require repeated hospitalization and 1 million will need heart surgery over the next 20 years. Annually, 233 000 deaths occur as a result of RHD. Many poor persons, who are preferentially affected, are disabled because of lack of access to the expensive medical and surgical care demanded by the disease. The prevalence of RHD in less-developed countries ranges from 20 to 40 per 1000 (by echocardiographic screening of schoolchildren). The incidence of rheumatic fever ranges from 13 to 374 per 100 000, and the rate of recurrence is high.
Managing with limited resources
The management of CVD is often technology intensive and expensive. Procedures for diagnosis or therapy, drugs, hospitalization, and frequent consultations with healthcare providers all contribute to the high cost. The high expenditure on tertiary care in most less-developed countries probably has a large contribution from CVD. This may divert scarce resources from developmental needs and from the unfinished agenda of infectious and nutritional disorders. Thus there is an urgent need for costeffective preventive strategies and case-management approaches that are based on the best available evidence, and generalized to the context of each developing country.
Infectious disease and the heart
Numerous infectious diseases may involve the endocardium (see 
Infective endocarditis, Chapter 4, pp. 187-209), myocardium (see 
Heart muscle diseases, Chapter 8, pp. 417-457), and the pericardium (see 
Pericardial diseases, Chapter 9, pp. 459-476). This section deals with a miscellaneous group of infectious diseases that are of particular relevance to cardiology practice outside Western Europe, e.g. human immunodeficiency virus (HIV) infection, Chagas’ disease, diphtheria, syphilis, and tetanus. Although occasional examples have been reported, myocardial involvement is so rare as to be of little clinical significance in tuberculosis (apart from pericarditis), typhoid fever, scrub typhus, poliomyelitis, infective hepatitis, virus pneumonias, and other respiratory tract infections.
Infective endocarditis, Chapter 4, pp. 187-209), myocardium (see Heart muscle diseases, Chapter 8, pp. 417-457), and the pericardium (see Pericardial diseases, Chapter 9, pp. 459-476). This section deals with a miscellaneous group of infectious diseases that are of particular relevance to cardiology practice outside Western Europe, e.g. human immunodeficiency virus (HIV) infection, Chagas’ disease, diphtheria, syphilis, and tetanus. Although occasional examples have been reported, myocardial involvement is so rare as to be of little clinical significance in tuberculosis (apart from pericarditis), typhoid fever, scrub typhus, poliomyelitis, infective hepatitis, virus pneumonias, and other respiratory tract infections.Diphtheria
Cardiac damage in diphtheria is due to a circulating exotoxin that inhibits protein synthesis in target tissues, with a high degree of affinity for the conduction system. Myocarditis occurs in up to 25% of cases of diphtheria and carries a mortality of approximately 60%.
Pathological examination shows a flabby dilated heart with a ‘streaky’ appearance of the myocardium. Microscopy reveals characteristic fatty infiltration of the myocytes, and other features of myocarditis.
Sinus tachycardia, gallop rhythm, cardiomegaly, and hypotension typically appear in the second week of illness.
The electrocardiogram (ECG) abnormalities are useful in diagnosis and fall under two headings:
tracings showing evidence of diffuse myocardial damage: low voltage, prolongation of the QT interval, and T-wave flattening or inversion
tracings showing evidence of damage to the conduction system with all degrees of atrioventricular (AV) block. The development of bundle branch block or complete heart block is a particularly ominous finding, and the reported mortality rates vary from 54% to 100% despite the insertion of transvenous pacing. The presence of myocardial damage is confirmed by marked elevation of the serum creatine kinase (CK) level; a high level is associated with poor prognosis.
The ECG eventually returns to normal but conduction abnormalities may persist for years.
Treatment
Treatment consists of supportive measures for heart failure, antibiotics (procaine penicillin G 600 000 U IM 12 hourly for 10 days or erythromycin 250-500 mg PO 6 hourly for 7 days) to prevent secondary infection and eliminate the diphtheria organisms in the throat, and temporary pacing in cases of AV heart block. Antitoxic serum should not be given at this stage because the exotoxin is already fixed and because of the risk of fatal serum reactions. Intubation and ventilation may be required for those patients with evidence of respiratory failure.
HIV and the cardiovascular system
The clinical effects of HIV on the heart are relatively uncommon, relative to the impact of HIV infection on the lungs, gastrointestinal tract, central nervous system, and skin. There are similarities in the pattern of CVD involvement in people living in developed and less-developed countries, but differences in the causative organisms implicated. The main presentations are (1) pericardial effusion; (2) cardiomyopathy; (3) pulmonary hypertension; (4) large vessel aneurysms; and (5) metabolic complications associated with anti-retroviral drug use.
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