The higher peaks in free calcium have greater potential to cause store-overload induced calcium release from the sarcoplasmic reticulum, leading to afterdepolarisations.In addition to its role as a calcium buffer, calsequestrin also regulates the release of calcium from the sarcoplasmic reticulum by directly modulating ryanodine receptors. When the concentration of calcium is low, calsequestrin monomers form a complex with the proteins triadin and junctin, which inhibit ryanodine receptors. However, at high calcium concentrations, calsequestrin forms polymers that dissociate from the ryanodine receptor channel complex, removing the inhibitory response and increasing the sensitivity of the ryanodine receptor to spontaneously releasing calcium.Decreased CASQ2 is also associated with high levels of calreticulin, a protein which among other roles regulates the reuptake of calcium into the sarcoplasmic reticulum by SERCA. In the absence of CASQ2, calreticulin levels increase and provide some compensatory calcium binding within the sarcoplasmic reticulum. It is possible that calreticulin may contribute to the generation of arrhythmias seen in association with CASQ2 mutations. Diagnosis
CPVT may be challenging to diagnose as the structure of the heart appears normal in those affected by the condition when assessed using an echocardiogram, cardiac MRI scan or cardiac CT scan, while the electrical function of the heart also appears normal at rest when assessed using a standard 12-lead ECG. However, in response to exercise or catecholamines such as adrenaline, abnormal heart rhythms such as bidirectional ventricular tachycardia or frequent polymorphic ventricular ectopic beats may be seen.
Acute volvulus often requires immediate surgical intervention to untwist the affected segment of bowel and possibly resect any unsalvageable portion.Volvulus occurs most frequently in middle-aged and elderly men. Volvulus can also arise as a rare complication in persons with redundant colon, a normal anatomic variation resulting in extra colonic loops.Sigmoid volvulus is the most-common form of volvulus of the gastrointestinal tract. and is responsible for 8% of all intestinal obstructions. Sigmoid volvulus is particularly common in elderly persons and constipated patients. Patients experience abdominal pain, distension, and absolute constipation. Cecal volvulus is slightly less common than sigmoid volvulus and is associated with symptoms of abdominal pain and small bowel obstruction. Volvulus can also occur in patients with Duchenne muscular dystrophy due to smooth muscle dysfunction.Gastric volvulus causes nausea, vomiting, and pain in the upper abdomen. The Borchardt triad is a group of symptoms that help doctors to identify gastric volvulus. The symptoms are intractable retching, pain in the upper abdomen and inability to pass nasogastric tube into the stomach. Complications
Strangulation
Gangrene
Perforation
Faecal peritonitis
Recurrent volvulus

Causes
Midgut volvulus occurs in people (usually babies) that are predisposed because of congenital intestinal malrotation. Segmental volvulus occurs in people of any age, usually with a predisposition because of abnormal intestinal contents (e.g. meconium ileus) or adhesions. Volvulus of the cecum, transverse colon, or sigmoid colon occurs, usually in adults, with only minor predisposing factors such as redundant (excess, inadequately supported) intestinal tissue and constipation.