If fainting spells occur often without a triggering event, syncope may be a sign of an underlying heart disease. In the case where syncope is caused by cardiac disease, the treatment is much more sophisticated than that of vasovagal syncope and may involve pacemakers and implantable cardioverter-defibrillators depending on the precise cardiac cause. Risk tools
The San Francisco syncope rule was developed to isolate people who have higher risk for a serious cause of syncope. High risk is anyone who has: congestive heart failure, hematocrit <30%, electrocardiograph abnormality, shortness of breath, or systolic blood pressure <90 mmHg. The San Francisco syncope rule however was not validated by subsequent studies.The Canadian syncope risk score was developed to help select low-risk people that may be viable for discharge home. A score of <0 on the Canadian syncope risk score is associated with <2% risk of serious adverse event within 30 days. It has been shown to be more effective than older syncope risk scores even combined with cardiac biomarkers at predicting adverse events. Epidemiology
There are 18.1–39.7 syncope episodes per 1000 people in the general population. Rates are highest between the ages of 10–30 years old. This is likely because of the high rates of vasovagal syncope in the young adult population. Older adults are more likely to have orthostatic or cardiac syncope. Syncope affects about three to six out of every thousand people each year. It is more common in older people and females. It is the reason for 2–5% of visits to emergency departments and admissions to hospital.
This failure of ornithine transport causes an interruption of the urea cycle and the accumulation of ammonia, resulting in the signs and symptoms of ornithine translocase deficiency.This disorder is inherited in an autosomal recessive pattern, which means the defective gene is located on an autosome, and two copies of the gene - one from each parent - are required to be born with the disorder. The parents of an individual with an autosomal recessive disorder each carry one copy of the altered gene but do not show signs and symptoms of the disorder. Diagnosis
Clinical findings in HHH syndrome are non-specific. If the disorder is suspected, laboratory testing can provide diagnostic information. Plasma amino acid analysis will show elevated ornithine levels, and urine amino acids will detect homocitrulline. Orotic acid may also be elevated. Ammonia levels can be variably elevated. If these findings are present, molecular testing may provide additional confirmatory information. Treatment
Treatments include discontinuation of protein intake, intravenous infusion of glucose and, as needed, infusion of supplemental arginine and the ammonia removal drugs, sodium phenylacetate and sodium benzoate. See also
Ornithine transcarbamylase deficiency
Inborn errors of metabolism
Ornithine aminotransferase deficiency (gyrate atrophy of the choroid and retina)

References
Charles Scriver, Beaudet, A.L., Valle, D., Sly, W.S., Vogelstein, B., Childs, B., Kinzler, K.W. (accessed 2007). New York: McGraw-Hill. Summaries of 255 chapters, full text through many universities. There is also the OMMBID blog. Further reading
Ornithine translocase deficiency at NLM Genetics Home Reference


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