Defibrillator: Mechanisms of Ventricular Fibrillation

BREAKING NEWS: 10.15.07--Medtronic, Inc., the world's largest maker of electronic heart devices, announced they are suspending sales of Sprint Fidelis leads. According to the FDA, these wires, used to connect defibrillators to the heart, may break or erode and may increase chance of injury. Learn more about the Medtronic Sprint Fidelis Recall.

Zipes divides the mechanisms of arrhythmia genesis into disorders of impulse formation and disorders of impulse conduction or both [Zipes DP 1994]. Zipes reminds us of the caveat that the present diagnostic tools do not permit definite determination of the electrophysiological mechanisms responsible for most clinically occurring arrhythmias or their ionic basis.

This he states is especially true for ventricular arrhythmias. Generally it is almost impossible to separate re-entry and automaticity. In most circumstances we are only able to suggest that such an arrhythmia is consistent with a particular underlying mechanism.

Due to the practical problems involved with mapping large areas of the heart, for many years, simultaneously ventricular fibrillation has been difficult to study. Most observers have confined their interests and efforts to the induction and termination of ventricular fibrillation.

Much of the current data on the dynamic electrophysiological changes during cardiac arrhythmias comes either from computer modeling, electrode studies, or the use of high resolution optical mapping.

In optical mapping, the emitted fluorescence caused by transmembrane potential changes of cardiac cells is documented by a video camera. The video images of the epicardial surface can be analysed pixel by pixel through image processing techniques. A typical high-resolution image may consist of 200 by 200 pixels giving data on 40,000 epicardial sites [Gray RA et al. 1999].

Mathematical models such as the Panfilov and Keener model also exist which facilitate our comprehension of the relationships between the electrocardiogram and the underlying spread of patterns of depolarisation throughout a three dimensional myocardium.

The Panfilov and Keener model particularly incorporates a realistic anatomical representation of the right and left ventricular structure. In addition, there is an accurate representation of myocardial fibre orientation and distribution of the dispersion of action potential dynamics [Panfilov AV et al. 1993, Nielson PMF et al. 1991].

If your or a loved has had an implantable cardioverter-defibrillator such as the recalled Guidant:

1. CONTAK RENEWAL 2, Model H155

2. CONTAK RENEWAL, Model H135, or

3. PRIZM 2 DR, Model 1861

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see also:

Re-entry Re-entry - "disorders of impulse conduction": Guidant Lawsuit Information, FREE
Re-entry -disorders of impulse conduction, FREE Guidant Defibrillator Lawsuit info

Abnormal automaticity Did your defibrillator cause abnormal automaticity?Get free legal help
Get free legal help for your defibrillator abnormal automaticity case

Sudden Cardiac Death Guidant CONTAK RENEWAL 2 H155: Sudden Cardiac Death
Sudden Cardiac Arrest and Guidant CONTAK RENEWAL 2 H155