Progress in Cardiac Arrythmia Research

Book Preface

Cardiac arrhythmia is a term that denotes a disturbance of the heart rhythm. Cardiac arrhythmias can range in severity from entirely benign to immediately life-threatening. A cardiac arrhythmia, also called cardiac dysrhythmia, is a disturbance in the regular rhythm of the heartbeat. Several forms of cardiac arrhythmia are life-threatening and a medical emergency.Cardiac arrhythmias sometimes are classified according to their origin as either ventricular arrhythmias (originating in the ventricles) or supraventricular arrhythmias (originating in heart areas above the ventricles, typically the atria). They also can be classified according to their effect on the heart rate, with bradycardia indicating a heart rate of less than 60 beats per minute and tachycardia indicating a heart rate of more than 100 beats per minute. This new book presents important research in the field from around the globe.

The chances for successful restoration of spontaneous circulation (ROSC) in cardiac arrest follwing ventricular fibrillation (VF) deteriorate rapidly with time. Improved myocardial reperfusion, e.g. by way of cardiopulmonary resuscitation (CPR), may improve the prospect for successful defibrillation. In addition, electrocardiographic (ECG) waveform analysis can help determine the optimal timing for defibrillation and thus prevent unnecessary damage caused to the myocardium by unsuccessful electric shocks. Computer-assisted ECG analysis with removal of CPR-associated noise and artifacts allows the outcome of defibrillation to be predicted without causing potentially detrimental interruptions in CPR. The likelihood that defibrillation in patients with sustained VF will be successful can be further improved by administering thrombolytics during CPR. While dissolution of coronary artery thrombosis resolves the underlying cause of myocardial infarction in the majority of patients, improved microcirculatory reperfusion and alteration of the electrical activity of the fibrillation process may increase the likelihood of restoring spontaneous circulation during resuscitation. An increase in fibrillation frequency, fibrillation amplitude or in amplitude spectrum area (AMSA) as calculated from electrocardiography (ECG) signals indicates that thrombolytic therapy is improving ventricular fibrillation status, thus improving the chances for successful defibrillation.

As presented in Chapter 1, contemporary preclinical in vitro and in vivo methods have been imperfect in predicting drug-induced Torsades de Pointes (TdP) arrhythmia in humans. A better understanding of additional relevant factors in the genesis of drug-induced TdP besides the relationships between hERG inhibition, action potential duration, and QT interval is necessary and supports the evolution of new methods to assess the cardiovascular safety of new drug candidates in the future.