While there was a statistically significant improvement in NYHA class, a secondary endpoint, there was no improvement in quality-of-life, six-minute walk or echocardiographic measures in the patients who received cardiac resynchronization therapy (CRT).
The resynchronization therapy in normal QRS (RethinQ) study, which followed 172 patients for six months, was designed to determine whether CRT can help heart failure patients with a narrow QRS complex and left ventricular mechanical dyssynchrony. Patients with a wide QRS already are indicated for CRT therapy. In the RethinQ study, narrow QRS was defined as 130 milliseconds or less (120 milliseconds or less is considered normal).
The subgroup of patients with QRS duration between 120 and 130 milliseconds showed a statistically significant benefit from CRT, as measured by the primary endpoint of exercise duration.
Mark Carlson, chief medical officer and senior vice president of clinical affairs and cardiac rhythm management division at St. Jude Medical, said: “RethinQ will help guide future studies to identify patients who may benefit from ICD and CRT therapy, and adds valuable information to enhance our ability to improve patient outcomes.”