Cyanosis is caused by a bidirectional or reversed shunt due to an anatomical communication between the systemic and pulmonary circulation at the atrial, ventricular or arterial level. Cyanotic patients comprise a heterogenous group of lesions with different underlying anatomy and pathophysiology, normal or restricted pulmonary blood flow in the presence of an obstruction across the pulmonary outflow tract or increased pulmonary blood flow in the absence of such an obstruction which then in results in development of pulmonary artery hypertension and eventually Eisenmenger syndrome. They may present without or with prior palliative intervention.
Cyanosis induce adaptive mechanisms to improve oxygen transport and delivery to the tissue: secondary erythrocytosis, rightward shift of the oxyhaemoglobin dissociation curve and increase in cardiac output. Erythrocytosis secondary to erythropoetin stimulus is the physiological response to chronic hypoxaemia. Compensated erythrocytosis reflects an equilibrium (stable haemoglobin in an iron replete state) and decompesated erythrocytosis indicates failure of an aquilibrium (rising haematocrit)
Cyanosis and secondary erythrocytosis imply profound consequence on the entire organ system:
- Blood viscosity is increased and is directly related to red blood cell mass
- Haemostatic abnormalities are common and complex, and are attributed to abnormalities in platelets (thrombocytopenia and thromboasthenia), coagulation pathway, and other abnormal coagulation mechanism. Vitamin K-dependent clotting factors (factor II,VII,IX and X) and factor V are reduced, fibrinolytic activity is increased and the largest von Willebrand multimers are depleted.
- Increased turnover of red blood cells/haemoglobin and impaired urate filtration lead to hyperuricaemia. The increased concentration of unconjugated bilirubin puts cyanotic patients at risk for calcium billirubinate gallstones.
- Severe endothelial dysfunction is evident by the striking impairment of endothelium-dependent vasodilatation
- Chronic hypoxaemia, increased blood viscosity, and endothelial dysfunction affect microcirculation, myocardial function and the function of other organ systems
Clinical presentation include central cyanosis, a result of an increased quantity of reduced haemoglobin, clubbing and frequently scoliosis. Cardiac findings vary and are characterized by the underlying anatomy/pathophysiology.
Mortality is significant higher in cyanotic patients than in acyanotic patients. outcome is determined by the underlying anatomy, pathophysiology, palliative procedures, complications of cyanosis and preventive measures. Low platelet count, severe hypoxia, cardiomegaly, and elevated haematocrit during childhood are useful parameters to predict premature death and adverse events in both patients with and without pulmonary vascular disease.
- Hyperviscosity symptoms include headache, faintness, dizziness, fatigue, tinnitus, blurred vision, paraesthesia of fingers, toes and lips, muscle pain and weakness.
- Bleeding and thrombotic diathesis occur and both caused a therapeutic dilemma as patients are at risk from thrombosis and bleeding. Spontaneous bleeding usually minor and self-limiting (dental bleeding, epistaxis, easy bruising and menorrhagia).Haemoptysis is the most common major bleeding event and is an external manifestation of an intrapulmonary haemorrhage not reflecting the extent of parenchimal bleeding (reported in up to 100% of Eisenmenger patients). Thrombosis is caused by coagulation abnormalities, stasis of blood in dilated chambers and vessels, atherosclerosis and/or endothelial dysfunction, the presence of thrombogenic materials (e.g. conduits), and arrhythmias.
- Cerebrovascular accidents may caused by thrombo-embolic events (paradoxical emboli), rheological factors (microcytosis), endothelial dysfunction and “traditional” atherosclerotic risk factors.
- Paradoxical emboli may caused by supraventricular arrhythmias or transvenous lead catheters.
- Iron deficiency is frequently caused by inappropriate phlebotomies
- Arrhytmias-supraventricular and ventricular
- Infectious complications include endocarditis, cerebral abcess and pneumonia.
- Renal dysfunction
- Rheumatological complication include gouty arthritis, hyperthrophic osteoarthropathy and kyphoscoliosis