An idioventricular rhythm is a cardiac rhythm characterized by a rate of <50 beats per minute (bpm), absence of P waves and widening of the QRS complex. In cases where the heart rate is  between 50 and 110 bpm, it is known as accelerated idioventricular rhythm and ventricular tachycardia if the rate exceeds 120 bpm. Causes of idioventricular rhythms are varied and can include drugs or a heart defect at birth. It is typically benign and not life-threatening. Etiology
Various etiologies may contribute to the formation of an idioventricular rhythm, and include:
Heart block
Reperfusion after myocardial infarction
Electrolyte abnormalities
Heart diseases present at birth
Certain drugs (eg. digoxin, β-agonists, anaesthetics)

Pathophysiology
The physiological pacemaker of the heart is the sinoatrial node. If the sinoatrial node is rendered dysfunctional, the AV node may act as the pacemaker. If both of these fail, the ventricles begin to act as the dominant pacemaker in the heart. The ventricles acting as their own pacemaker gives rise to an idioventricular rhythm. Diagnosis
An ECG trace is required for diagnosis. Treatment
As this rhythm is not life-threatening, treatment has limited value for the patient. If underlying pathologies are identified, they should be treated appropriately. Antidysrhythmics may be utilised if the patient suffers from dysrhythmias. == References ==
A pinguecula is a common type of conjunctival stromal degeneration in the eye. It appears as an elevated yellow-white plaque in the bulbar conjunctiva near the limbus. Calcification may also seen occasionally. Etiology
The exact etiology is unknown, but it may be associated with aging and excessive exposure to UV light. Signs and symptoms
It is seen as a yellow-white deposit on the conjunctiva adjacent to the limbus (the junction between the cornea and sclera). (It is to be distinguished clinically from a pterygium, which is a wedge shaped area of fibrosis that may grow onto the cornea.) A pinguecula usually does not cause any symptoms. It is most common in tropical climates and there is a direct correlation with UV exposure. Histologically, there is degeneration of the collagen fibers of the conjunctival stroma with thinning of the overlying epithelium and occasionally calcification. Actinic exposure of the thin conjunctival tissue is thought to cause fibroblasts to produce more elastin fibers, which are more twisted than normal elastin fibers and may lead to the degradation of the collagen fibers. Alternatively, it has been postulated that the sub-epithelial collagen fibers undergo degradation and assume the qualities of elastic tissue while fragmenting and twisting in a different configuration from their normal state.It is thought that the high reflectivity of the solid white scleral tissue underlying the conjunctival tissue may result in additional UV exposure to the back side of the tissue. The side of the nose also reflects sunlight on to the conjunctiva.