The vast majority of ventricular fibrillation arrest can be traced back to cardiac etiology (ie CAD, HOCM, myocarditis, etc). However there have been rare cases of v fib arrest secondary to nontraumatic SAH; one recently in our own backyard (Elmhurst)!
Aneurysmal SAH is a relatively common cause of PEA, but VF arrest is almost unheard of. Inamasu et al reports that, among 315 patients with nontraumatic SAH over 6 years, VF as initial cardiac rhythm was only observed in 1 patient (0.3%). One proposed pathophysiology is that SAH increases ICP reducing CPP particularly in the brainstem thereby resulting in respiratory arrest; severe hypoxia induces V fib. Another possible pathophysiology is excessive sympathetic response unchecked by inadequate parasympathetic response. Case reports have described appearance of J waves immediately prior to VF secondary to SAH. Prognosis is abysmal with 1/3 of SAH-VF patients dying within the first 24hrs of hospitalization. Transient return of brainstem function is most favorable in patients with v fib arrest that attain ROSC within 5-10 minutes. Unfortunately there are no differences in mortality between SAH-VF patients who regain transient brainstem function and those who do not.
Inamasu J, Nakagawa Y, Kuramae T, Nakatsukasa M, Miyatake S. Subarachnoid hemorrhage causing cardiopulmonary arrest: resuscitation profiles and outcomes. Neurol Med Chir (Tokyo). 2011;51(9):619-23.
Mitsuma W, Ito M, Kodama M, Takano H, Tomita M, Saito N, Oya H, Sato N, Ohashi S, Kinoshita H, Kazama JJ, Honda T, Endoh H, Aizawa Y. Clinical and cardiac features of patients with subarachnoid haemorrhage presenting with out-of-hospital cardiac arrest. Resuscitation. 2011 Oct;82(10):1294-7. doi: 10.1016/j.resuscitation.2011.05.019. Epub 2011 Jul 20.
Kukla P, Jastrzebski M, Praefort W. J-wave-associated ventricular fibrillation in a patient with a subarachnoid haemorrhage. Europace. 2012 Jul;14(7):1063-4. doi: 10.1093/europace/eur410. Epub 2012 Jan 2.