- Cyanosis: occurs when the reduced hemoglobin concentration (unoxygenated) is (5 gm/dl) 50 gm/l or greater.
- If severe anemia is present (<15% PCV) than cyanosis cannot be detected
- Cyanosis may occur due to:
- Severe respiratory disease and the inability to oxygenate blood.
- Right to left shunt located:
- at the level of the atria
- at the level of the ventricles
- at the level of the aorta and pulmonary artery
- arterio-venous shunt in the lungs
- Weakness occurs when:
- Cardiac output to the skeletal muscles is reduced.
- Cardiac output may be normal but due to a shunt, the level of oxygen delivered to the skeletal muscles is reduced.
- Syncope: occurs for the same etiologies as weakness, however, it is defined as a transient loss of consciousness caused by a reduction in cerebral oxygen or glucose delivery that is due either to decreased amounts of these constituents in blood or, more commonly, to decreased cerebral blood flow. Syncope can be difficult to differentiate from a seizure. See more about syncope.
| Syncope | Seizure |
| + generalized muscle weakness | + aura |
| +/- ataxia | + loss of consciousness |
| + collapse | +/- tonic/clonic activity |
| +/- loss of consciousness | +/- defecation |
| +/- muscular activity | +/- hypersalivation |
| +/- flaccid muscle | +/- vomiting |
| +/- urination | +/- post ictal period |
| +/- defecation | +/- occurs during sleep |
| – vomiting | |
| +/- vocalization | |
| + rapid recovery | |
| – post ictal period | |
| + preceded by activity or excitement |
- Differential diagnosis for syncope includes:
- seizure, narcolepsy, cataplexy
- electrolyte disorders
- neuro-muscular junctional disorders
- Pulmonary vasculature as determined radiographically.
- Pulmonary overcirculation:
- An increased volume of blood flow through the pulmonary vasculature associated with left to right shunts.
- Pulmonary undercirculation:
- A reduced volume of blood flow through the pulmonary vasculature associated with right to left shunts.
- Pulmonary overcirculation:
- Polycythemia:
- is a compensatory response to an inadequate delivery of oxygen to the metabolizing tissues
- is seen primarily with right to left shunts
- The recirculation circuit:
- The recirculation circuit determines the vessels and intracardiac chambers that become enlarged (undergo dilation/eccentric hypertrophy) associated with congenital disorders or acquired disorders that cause volume overload.
- This involves disorders of valvular insufficiency or shunting.
- The recirculation circuit is the path that a red blood cell would take if it continuously traversed across the defect on every occasion when it encounters the defect.
- The structures within the recirculation circuit are subject to volume overload; that is they carry an increase in blood volume.
- The cardiac structures within the recirculation circuit respond to volume overload by eccentric hypertrophy (dilation).
- The arteries and veins within the recirculation circuit respond to volume overload by dilation.