Improvements in 25 Years of Implantable Cardioverter Defibrillator Therapy

In 1980, Dr. Michel Mirowski and his team inserted the first implantable cardioverter defibrillator (ICD) in a patient. Initially, ICD therapy was not widely accepted, and many physicians actually considered this therapy unethical. Large secondary and primary prevention trials, demonstrating a beneficial effect of ICD therapy in selected patients not only on arrhythmic death but also on all-cause mortality, stimulated a rapid growth in the number of implants and increased patient’s and physician’s acceptance. Improvements in size and weight, arrhythmia discrimination capabilities, battery technology, shock waveform and output, monitoring capabilities and defibrillator electrode technology eventually resulted in the current large number of yearly implants. Today, almost 40 years after the conception of the ICD and 25 years after the first human implant, ICD therapy is the treatment of choice for patients at risk for life-threatening arrhythmias either as secondary or primary prevention. Furthermore, with the more recent addition of resynchronisation therapy to standard ICD therapy, it became possible to treat selected patients with advanced symptoms of heart failure and to lower the risk of sudden death

Left Bundle Branch Block, an Old–New Entity

Left bundle branch block (LBBB) is generally associated with a poorer prognosis in comparison to normal intraventricular conduction, but also in comparison to right bundle branch block which is generally considered to be benign in the absence of an underlying cardiac disorder like congenital heart disease. LBBB may be the first manifestation of a more diffuse myocardial disease. The typical surface ECG feature of LBBB is a prolongation of QRS above 0.11 s in combination with a delay of the intrinsic deflection in leads V5 and V6 of more than 60 ms and no septal q waves in leads I, V5, and V6 due to the abnormal septal activation from right to left. LBBB may induce abnormalities in left ventricular performance due to abnormal asynchronous contraction patterns which can be compensated by biventricular pacing (resynchronization therapy). Asynchronous electrical activation of the ventricles causes regional differences in workload which may lead to asymmetric hypertrophy and left ventricular dilatation, especially due to increased wall mass in late-activated regions, which may aggravate preexisting left ventricular pumping performance or even induce it. Of special interest are patients with LBBB and normal left ventricular dimensions and normal ejection fraction at rest but who may present with an abnormal increase in pulmonary artery pressure during exercise, production of lactate during high-rate pacing, signs of ischemia on myocardial scintigrams (but no coronary artery narrowing), and abnormal ultrastructural findings on myocardial biopsy. For this entity, the term latent cardiomyopathy had been suggested previously

IMPROVED SURVIVAL WITH AN IMPLANTED DEFIBRILLATOR IN PATIENTS WITH CORONARY DISEASE AT HIGH RISK FOR VENTRICULAR ARRHYTHMIA.

FOR THE MULTICENTER AUTOMATIC DEFIBRILLATOR IMPLANTATION TRIAL INVESTIGATOR