Not all spider bites involve injection of venom, and the amount of venom injected can vary based on the type of spider and the circumstances of the encounter. The mechanical injury from a spider bite is not a serious concern for humans. However, it is generally the toxicity of spider venom that poses the most risk to human beings; several spiders are known to have venom that can cause injury to humans in the amounts that a spider could inject when biting. While venoms are by definition toxic substances, most spiders do not have venom that is directly toxic (in the quantities delivered) to require medical attention and, of those that do, severity is typically mild. Spider venoms work on one of two fundamental principles; they are either neurotoxic (attacking the nervous system) or necrotic (attacking tissues surrounding the bite). In some cases, the venom affects vital organs and systems. The venoms of the widow spiders, Brazilian wandering spider and Australian funnel-web are neurotoxic. Heart muscle damage is an unusual complication of widow venom that may lead to death. Pulmonary edema, which is fluid accumulation in the lungs, is a feared and potentially serious but uncommon complication of funnel-web venom. Recluse and South African sand spider venoms are necrotic. Recluse venom may also cause severe hemolysis (destruction of red blood cells), though this is typically uncommon.
Ectopia cordis (Greek: "away / out of place" + Latin: "heart") or ectopic heart is a congenital malformation in which the heart is abnormally located either partially or totally outside of the thorax. The ectopic heart can be found along a spectrum of anatomical locations, including the neck, chest, or abdomen. In most cases, the heart protrudes outside the chest through a split sternum. Pathology
Ectopia cordis results from a failure of proper maturation of midline mesoderm and ventral body wall (chest) formation during embryonic development. The exact etiology remains unknown, but abnormalities in the lateral body wall folds are believed to be involved. Normally, the lateral body walls are responsible for fusion at the midline to form the ventral wall. Corruption of this process may underlie ectopia cordis.Defective ventral body wall formation yields a heart unprotected by the pericardium, sternum, or skin. Other organs may also have formed outside the skin, as well. Many cases of ectopia cordis have associated congenital heart defects, in which the heart has failed to properly form.Defects more commonly associated with ectopia cordis include:
Intracardiac defects
Atrial septal defect
Ventricular septal defect
Tetralogy of Fallot
Tricuspid atresia
Double outlet right ventricle
Non-cardiac malformations
Pentalogy of Cantrell
Omphalocele
Anterior diaphragmatic hernia
Cleft palate

Diagnosis
The Diagnosis of ectopia cordis is found with a routine ultrasound as early as the first trimester or the beginning of the second trimester. Treatment
Due to the rarity and rapid postpartum mortality of ectopia cordis, limited treatment options have been developed. Only some successful surgeries have been performed as of now, and the mortality rate remains high.