This video was shown during a LUCAS device demonstration at our receiving hospital in 2008. It’s a time lapse of a heart in VF (swine model).
The handout from Physio-Control had a diagram explaining that forward blood flow continues for several minutes after the onset of VF while arterial pressure (AP) and central venous pressure (CVP) merge together. During that time theÂ right ventricle becomes engorged as you can see in the time lapse video.
Diagram from Steen et al. The critical importance of minimal delay between chest compressions and subsequent defibrillation: a haemodynamic explanation. Resuscitation. 2003;58(3):249-258.
The handout states: “This leaves the heart distended and reduces the effectiveness of shocks on patients with shockable VF rhythms.” It was explained this is one possible reason that 2 minutes of CPR prior to the first shock is beneficial when no CPR has been performed prior to EMS arrival.
Subsequent researchersÂ have questioned this theory.
ConsiderÂ Magnetic Resonance Imaging During Untreated Ventricular Fibrillation Reveals Prompt Right Ventricular Overdistention Without Left Ventricular Volume Loss.Â Circulation 2005; 111: 1136-1140.
Background: Most out-of-hospital ventricular fibrillation (VF) is prolonged (>5 minutes), and defibrillation from prolonged VF typically results in asystole or pulseless electrical activity. Recent visual epicardial observations in an open-chest, open-pericardium model of swine VF indicate that blood flows from the high-pressure arterial system to the lower-pressure venous system during untreated VF, thereby overdistending the right ventricle and apparently decreasing left ventricular size. Therefore, inadequate left ventricular stroke volume after defibrillation from prolonged VF has been postulated as a major contributor to the development of pulseless rhythms.
Conclusion: In this closed-chest swine model of VF, substantial right ventricular volume changes occurred early and did not result in smaller left ventricular volumes. The changes in ventricular volumes before the late development of stone heart do not explain why defibrillation from brief duration VF (<5 minutes) typically results in a pulsatile rhythm with return of spontaneous circulation, whereas defibrillation from prolonged VF (5 to 15 minutes) does not.
I still think it’s interesting.