Advances in cardiac electrophysiology and pacing

New technologies such as intracardiac echocardiography, nonfluoroscopic ele ctroanatomic mapping, and noncontact endocardial activation mapping have co ntributed significantly to the advancements in interventional cardiac elect rophysiology. Radiofrequency ablation is now consistently effective treatme nt for typical atrial flutter in addition to atrioventricular (AV) nodal an d AV reentrant tachycardias. Although atrioventricular junctional ablation plus pacemaker implantation is reported to be superior to drug therapy in c ontrolling symptoms caused by atrial fibrillation, some investigators have reported no significant improvement in cardiac performance or disease progr ession. These limitations have spurred efforts toward curative therapy. Cat heter-based radiofrequency ablative approaches, designed to create linear l esions or aimed at focal sources, are exciting new approaches for drug-refr actory atrial fibrillation patients. (17 44) (45, 68. 122) In experienced h ands, radiofrequency catheter ablation is able to eliminate spontaneous epi sodes of ventricular tachycardia (VT) in up to two thirds of patients after myocardial infarction.(116) At present, catheter ablation of VT is largely adjunctive to amiodarone and the implantable cardioverter defibrillator (I CD). Advances also have been made in device therapy. Clinical trials have demons trated that the ICD is more effective than antiarrhythmic drugs in primary and secondary prevention of sudden cardiac death in several clinical settin gs. Modern ICDs provide sophisticated algorithms for tachyarrhythmia therap y and dual-chamber, rate-responsive pacing.(91) A low-energy (less than 6 J ) atrial defibrillator (InControl METRIX Atrioverter, Redmond, WA) also has emerged. Initial studies indicate that the atrial defibrillator is able to recognize episodes of atrial fibrillation accurately and to restore sinus rhythm safely and effectively(126) There is increasing interest in multisit e ventricular pacing in patients with congestive heart failure. Preliminary experience has shown that biventricular pacing significantly improves card iac function and quality of life in patients with congestive heart failure and electrocardiographic (ECG) evidence of widened QRS duration. Noninvasive techniques such as assessment of heart rate variability(32). (3 3) and T wave alternans(22) have been documented to be useful tools for sud den cardiac death risk stratification. Abnormal heart rate variability(32) (33) and T wave alternans(38) have been shown to be strong independent pred ictors of arrhythmic death.