Do the official guidelines for cardiac resynchronization therapy need to be changed?

Heart failure (HF) an ongoing epidemic that shows no signs of abating, despite many advances in medicine. Approximately 5 million Americans and a similar number of Europeans are currently diagnosed with heart failure. More than 500,000 new cases are diagnosed each year in the United States [1, 2]. As our treatment of coronary artery disease, sudden cardiac arrest, and hypertension improves, more patients survive to develop HF. The obesity epidemic, with the accompanying metabolic syndrome, diabetes and hypertension, also contributes to the increasing number of patients with HF. In addition, the advancing age of the population has led to an even further increase in the incidence and prevalence of HF. The incidence of HF approaches 10 per 1,000 population after age 65. HF is the most common Medicare diagnosis-related group, and more dollars are spent in the United States for the diagnosis and treatment of HF than for any other diagnosis. Over the past 15-20 years, the development of new pharmacologic therapy has lowered mortality by 30-40% in patients with advanced HF. However, despite the use of optimal pharmacologic therapy with betablockers, angiotensin converting enzyme inhibitors or angiotensin receptor blockers, and diuretics, many patients still have significant symptoms that affect functional capacity and quality of life. More recently, cardiac resynchronization therapy (CRT) has been added to the armamentarium of HF therapies on the basis of strong evidence from well-designed clinical trials. Patients with evidence of ventricular dyssynchrony by virtue of prolonged QRS durations, typically with left bundle branch block, who have New York Heart Association (NYHA) class III-IV symptoms despite optimal medical therapy have been treated with atrial-synchronous, biventricular pacing using right ventricular leads as well as coronary sinus leads for left ventricular pacing [3]. Clinical trials have shown improvement in exercise capacity, NYHA class, and quality of life with CRT compared with continued medical therapy [4,5,6,7,8,9]. Landmark clinical trials such as COMPANION [10] and CARE-HF [11] have also shown a survival benefit with CRT. This therapy has opened up a whole new modality in the treatment of HF, focusing on electromechanical assistance to the failing heart.