Erythropoietin Levels in Cardiac Resynchronization Patients

Cardiac resynchronization therapy (CRT) is indicated in patients with advanced heart failure secondary to severe systolic impairment and refractory symptoms despite optimized medical treatment and evidence of electro- mechanical dyssynchrony with a QRS complex greater than 120 milliseconds (msec). Approximately 20%-30% of patients who receive CRT fail to respond with little improvement in subjective symptoms, functional capacity, and left ventricular indices. To date, there fails to be a serologic marker to adequately assess the degree of ventricular dyssynchrony and electro-mechanical dissociation. Increased levels of erythropoietin (EPO), a hematopoietic cytokine, has been demonstrated in patients with more advanced stages of heart failure and is associated with an increase in mortality and hospital re-admission. A recent study demonstrated a significant response to CRT in patients with higher baseline EPO levels (> 25mU/mL) with improvements in cardiac function and reduced heart failure symptoms. The presence of elevated EPO levels in addition to traditional determinants of cardiac dyssynchrony may effectively predict those that will benefit from CRT. LETTER TO THE EDITOR Cardiac resynchronization therapy (CRT) is indicated in patients with advanced heart failure secondary to severe systolic impairment and refractory symptoms despite optimized medical treatment and evidence of electro- mechanical dyssynchrony with an ECG QRS complex greater than 120 msec. Simultaneous pacing of both the right and left ventricle (BiV pacing) has been shown to restore electro-mechanical synchrony, improve overall cardiac function, reduce hospitalizations, and confer a mortality benefit (1). Despite the cardiovascular benefits of BiV pacing demonstrated in recent trials, approximately 20%- 30% of patients who receive CRT fail to respond with little improvement in subjective symptoms, functional capacity, and left ventricular functional indices (2). Absence of electro-mechanical dyssynchrony despite prolonged QRS duration (>120ms), pre-existing right bundle branch block (RBBB), inappropriate lead placement and continued disease progression have been shown as causes for non-response to CRT. To date, there fails to be a serologic marker to adequately assess the degree of ventricular dyssynchrony and electro-mechanical dissociation. Erythropoietin (EPO), a hematopoietic cytokine, has traditionally been associated with erythropoiesis in response to anemic stress. Several studies have indicated the positive effects of EPO treatment in heart failure patients with concomitant anemia resulting in reductions in hospital re- admission, improved cardiac and renal function, as well as