Part VII continues the discussion on the second subdivision of bioelectromagnetism, i.e. electro- and magnetobiology, with applications to cardiology. The electric stimulation of cardiac tissue has two very important clinical applications: cardiac pacing and cardiac defibrillation.
The purpose of cardiac pacing is to maintain the heart rate at a sufficient level even though the activity of the sinus node may not reach the ventricular muscle because of an interrupt in the conduction system. Too low a heart rate cannot provide a high enough blood pressure to maintain the body with sufficient oxygen concentration.
The purpose of cardiac defibrillation is to stop continuous and uncontrolled multiple re-entrant activation circuits causing fibrillating muscular contractions. Fibrillation of the ventricular muscle causes a total loss of the blood pumping action and thus leads to a dramatically decreased blood pressure, lack of oxygen in the brain tissue and death, unless the fibrillation can be stopped with a defibrillator within a few minutes.
In clinical practice, both cardiac pacing and cardiac defibrillation are achieved solely with electric methods. Some experiments in accomplishing these with magnetic stimulation have been perfotmed. They are, however, so limited that a separate chapter on magnetic stimulation of the heart muscle is not included but these experiments are referred to in the appropriate chapters on (electric) cardiac pacing and defibrillation.