Question 6 from the second paper of 2004 and Question 2d from the first paper of 2000 both asked the candidates to recall the non-shockable arm of the advanced life support algorithm. PEA is a situation where one is presented with organised electrical activity (i.e. a potentially perfusing rhythm) in the absence of cardiac output. The old term (electro-mechanical dissociation) is no longer in use.
Causes of cardiac arrest in general are discussed elsewhere. In brief, the same "Four Hs and four Ts" mnemonic applied to non-shockable rhythms, even though some Hs and Ts are more associated with some and less with others. For instance, PEA is more often the consequence of some sort of restriction on eitehr preload or afterload (i.e. an empty heart pumping) - for instance, obstructive shock, or massive hypovolemia. On the other hand, the arrhythmic causes of arrest are more likely to be due to a cardiac ischaemic event or some sort of metabolic disturbance, like hyperkalemia. Either way, the end result of VF or VT is usually still asystole.
The college answer refers to the 10-step zigzag mnemonic introduced into popular thinking by Walter Kloeck in 1995; the more recent trainees will probably be more familiar with the 4Hs and 4 Ts which is the modern "8-step" version. The "zigzag" refers to the pattern of physical examination, following a jagged course from airway to carotid to auscultation of the chest and praecordium, then to the cubital fossa (toxins? meaning trackmarks?) and so on.
People keep submitting these case reports. There are thousands of different weird asystoles every year. This selection includes only the reports published in 2015, just as an example.
Myerburg, ROBERT J. "Sudden cardiac death: epidemiology, causes, and mechanisms." Cardiology 74.Suppl. 2 (1987): 2-9.
Benditt, David G., Gert van Dijk, and Roland D. Thijs. "Ictal Asystole Life-Threatening Vagal Storm or a Benign Seizure Self-Termination Mechanism?." Circulation: Arrhythmia and Electrophysiology 8.1 (2015): 11-14.
Miyoshi, Hirotsugu, Ryuji Nakamura, and Hiroshi Hamada. "Asystole following skull clamp to Chiari malformation." Journal of anesthesia 29.2 (2015): 317-317.
Kafrouni, Hazem, et al. "Asystole Due to Saline Irrigation during a Posterior Fossa Surgery: A Case Report." Journal of Anesthesia & Clinical Research 2015 (2015).
Desbiens, Norman A. "Simplifying the diagnosis and management of pulseless electrical activity in adults: A qualitative review*." Critical care medicine 36.2 (2008): 391-396.
Kloeck, Walter GJ. "A practical approach to the aetiology of pulseless electrical activity. A simple 10-step training mnemonic." Resuscitation 30.2 (1995): 157-159.