Types of syncope occurring during a tilt-table test (TTT) include vasodepressor-type, cardioinhibitory-type, or a mixed-type according to heart rate and blood pressure responses. Long asystole responses during cardioinhibitory-type syncope, as induced by the TTT, require careful intervention to prevent convulsive syncope. The purpose of this study was to analyze the clinical characteristics of patients with long asystole induced by the TTT. In total, 195 patients (106 man, 89 women, age 47.0 ± 20.4 years) underwent a TTT from October 2013 to March 2017. A long asystole response was defined as no detectable heartbeat for more than 3 seconds. Seventeen patients (nine men, eight women, age 37.5 ± 16.1 years) exhibited cardioinhibitory-type reflex syncope with long asystole. The average asystole time was 10.0 ± 6.0 s, and the maximum was 25.4 s. Three patients with long asystole appeared to experience convulsions but did not require additional treatments, including any drugs. The patients with periods of long asystole were significantly younger than those without periods of long asystole.
Individuals exhibiting dwarfism with shortened limbs appeared in a colony of Sprague-Dawley rat strains maintained at the Institute for Animal Experimentation, St. Marianna University Graduate School of Medicine. Rats with dwarfism were identified as having insufficient calcification during bone growth due to endochondral ossification and named “cartilage calcification insufficient (CCI) rats.” The expression of FGF18 mRNA in CCI rat growth plates was significantly higher than that in normal rats, whereas the expression of Ihh, osteopontin, osteocalcin, bone-type alkaline phosphatase (BAP) and dentin matrix protein-1 mRNA was significantly lower. From these results, it has been speculated that the increased expression of FGF18 in the growth plate suppressed Ihh expression, causing suppression of the expression of the calcification factors osteocalcin and BAP and resulting in calcification failure, which potentially might have contributed to abnormalities in endochondral ossification in CCI rats. Based on these facts, CCI rats are expected to be useful disease model animals for studying bone system diseases exhibiting short-limbed dwarfism, such as achondrogenesis and hypochondrosis. Furthermore, cartilage and bone formation involves a large number of bioactive factors, so CCI rats exhibiting insufficient cartilage calcification in the cartilage growth plate are considered to be useful experimental animals for elucidating the factors involved in cartilage and bone formation and the mechanisms thereof.