What does a CRT-P pacemaker do?

A CRT-P pacemaker, or Cardiac Resynchronization Therapy-Pacemaker, primarily functions to pace both ventricles simultaneously, which helps in resynchronizing the heartbeat. This is particularly important for patients who suffer from heart failure and have a condition known as ventricular dyssynchrony, where the ventricles do not contract at the same time. By pacing both ventricles simultaneously, the CRT-P device can improve the efficiency of the heart’s contractions, enhance cardiac output, and ultimately alleviate symptoms associated with heart failure.

The other options focus on different pacing behaviors that do not apply to the CRT-P function. For instance, pacing the left atrium independently or only the right ventricle does not address the synchronization of both ventricles, which is the critical function of a CRT-P device. Additionally, while increasing heart rate under stress is a function associated with other types of pacemakers or cardiac devices, it does not accurately describe the primary role of a CRT-P pacemaker. Thus, the defining capability of a CRT-P is its ability to pace both ventricles together to ensure a coordinated and effective cardiac contraction.