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(Circulation. 2005;111:1136-1140.)
© 2005 American Heart Association, Inc.

Imaging

Magnetic Resonance Imaging During Untreated Ventricular Fibrillation Reveals Prompt Right Ventricular Overdistention Without Left Ventricular Volume Loss

Robert A. Berg, MD, FCCM; Vincent L. Sorrell, MD; Karl B. Kern, MD; Ronald W. Hilwig, DVM, PhD; Maria I. Altbach, PhD; Melinda M. Hayes, MD; Kathryn A. Bates, DO; Gordon A. Ewy, MD

From the University of Arizona College of Medicine, Steele Memorial Children’s Research Center and Department of Pediatrics (R.A.B.), Sarver Heart Center (R.A.B., V.L.S., K.B.K., R.W.H., M.M.H., K.A.B., G.A.E.), Department of Medicine (V.L.S., K.B.K., K.A.B., G.A.E.), Department of Radiology (M.I.A.), and Department of Anesthesiology (M.M.H.), Tucson.

Reprint requests to Robert A. Berg, MD, University of Arizona, Department of Pediatrics/3302, PO Box 245073, Tucson, AZ 85724-5073. E-mail rberg{at}peds.arizona.edu

Received July 2, 2004; revision received October 18, 2004; accepted November 5, 2004.

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.

Methods and Results— Ventricular dimensions were determined by MRI for 30 minutes of untreated VF in a closed-chest, closed-pericardium model in 6 swine. Within 1 minute of untreated VF, mean right ventricular volume increased by 29% but did not increase thereafter. During the first 5 minutes of untreated VF, mean left ventricular volume increased by 34%. Between 20 and 30 minutes of VF, stone heart occurred as manifested by dramatic thickening of the myocardium and concomitant substantial decreases in left ventricular volume.

Conclusions— 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.

Key Words: cardiopulmonary resuscitation • heart arrest • hemodynamics • magnetic resonance imaging • ventricular fibrillation