This is especially true for heart transplant, which transmits T. cruzi 75–100% of the time, and less so for transplantation of the liver (0–29%) or a kidney (0–19%). An infected mother can pass T. cruzi to her child through the placenta; this occurs in up to 15% of births by infected mothers. As of 2019, 22.5% of new infections occurred through congenital transmission. Pathophysiology
In the acute phase of the disease, signs and symptoms are caused directly by the replication of T. cruzi and the immune systems response to it. During this phase, T. cruzi can be found in various tissues throughout the body and circulating in the blood. During the initial weeks of infection, parasite replication is brought under control by production of antibodies and activation of the hosts inflammatory response, particularly cells that target intracellular pathogens such as NK cells and macrophages, driven by inflammation-signaling molecules like TNF-α and IFN-γ.During chronic Chagas disease, long-term organ damage develops over years due to continued replication of the parasite and damage from the immune system. Early in the course of the disease, T. cruzi is found frequently in the striated muscle fibers of the heart. As disease progresses, the heart becomes generally enlarged, with substantial regions of cardiac muscle fiber replaced by scar tissue and fat. Areas of active inflammation are scattered throughout the heart, with each housing inflammatory immune cells, typically macrophages and T cells.
Compounding effects of independent conditions:In persons with epilepsy, the hypoxia caused by apnea may be powerful enough to trigger seizures even in the presence of medication that otherwise controls those seizures well. In adults with coronary artery disease, a severe drop in blood oxygen level can cause angina, arrhythmias, or heart attacks (myocardial infarction). Longstanding and recurrent episodes of apnea may, over months and years, have the cumulative effect of increasing blood carbon-dioxide levels to the point that enough carbon dioxide dissolves in the blood to form carbonic acid in overall proportions sufficient to cause respiratory acidosis. In persons who have either or both forms of sleep apnea, breathing irregularities during sleep can be dangerously aggravated by taking respiration-depressing drugs, especially sedative drugs that operate by depressing the central nervous system generally; respiratory depressants include opiates, barbiturates, benzodiazepines, and, in large quantities, alcohol, the last three of which are broad-spectrum CNS depressants. Quantities that are normally considered safe may cause the person with chronic sleep apnea to stop breathing altogether. Should these individuals have general anaesthesia, for example, they require prolonged monitoring after initial recovery, as compared against a person with no history of sleep apnea, because apnea is likely to occur with even low levels of the drugs in their system.