The constant interval between the sinus beat and PVC suggests a reentrant etiology rather than spontaneous automaticity of the ventricle.Premature atrial contractions by contrast do not have a compensatory pause, since they reset the sinus node, but atrial or supraventricular bigeminy can occur. If the PACs are very premature, the wavefront can encounter a refractory AV node and not be conducted. This can be mistaken for sinus bradycardia if the PAC is buried in the T wave since the PAC will reset the SA node and lead to a long P–P interval. Diagnosis
Rule of bigeminy
When the atrial rhythm is irregular (as in atrial fibrillation or sinus arrythmia) the presence of bigeminy depends on the length of the P–P interval and happens more frequently with a longer interval. As with post PVC pauses, a longer P–P interval leads to a higher chance of re-entrant circuits and thus PVCs. The term "rule of bigeminy" is used to refer to the dependence of bigeminy on the ventricular cycle length in irregular rhythms. Classification
There can be similar patterns depending on the frequency of abnormal beats. If every other beat is abnormal, it is described as bigeminal. If every third beat is aberrant, it is trigeminal; every fourth would be quadrigeminal. Typically, if every fifth or more beat is abnormal, the aberrant beat would be termed occasional.Bigeminy is contrasted with couplets, which are paired abnormal beats.
Simeticone (INN), also known as simethicone (USAN), is an anti-foaming agent used to reduce bloating, discomfort or pain caused by excessive gas. Medical uses
Simeticone is used to relieve the symptoms of excessive gas in the gastrointestinal tract, namely bloating, burping, and flatulence. While there is a lack of conclusive evidence that simeticone is effective for this use, ⁣ studies have shown that it can relieve symptoms of functional dyspepsia and functional bloating.It has not been fully established that simeticone is useful to treat colic in babies, and it is not recommended for this purpose. A study in the United Kingdom reported that according to parental perception simeticone helped infant colic in some cases.Simeticone can also be used for suspected postoperative abdominal discomfort in infants. Side effects
Simeticone does not have any serious side effects. Two uncommon side effects (occurring in 1 in 100 to 1 in 1,000 patients) are constipation and nausea. Pharmacology
Simeticone is a non-systemic surfactant which decreases the surface tension of gas bubbles in the GI tract. This allows gas bubbles to leave the GI tract as flatulence or belching. Simeticone does not reduce or prevent the formation of gas. Its effectiveness has been shown in several in vitro studies. Chemistry
Simethicone is a mixture of dimethicone and silicon dioxide. Names
The INN name is "simeticone", which was added to the INN recommended list in 1999.Simeticone is marketed under many brand names and in many combination drugs; it is also marketed as a veterinary drug. == References ==