Predictors of cardiac resynchronization therapy response: the pivotal role of electrocardiogram

Abstract

Heart failure affects millions of patients all over the world, and its treatment is a major clinical challenge. Cardiac dyssynchrony is common among patients with advanced heart failure. Resynchronization therapy is a major advancement in heart failure management, but unfortunately not all patients respond to this therapy. Hence, many diagnostic tests have been used to predict the response and prognosis after cardiac resynchronization therapy. In this paper we summarize the usefulness of different diagnostic modalities with special emphasis on the role of surface electrocardiogram as a major predictor of response to cardiac resynchronization therapy.

Figure 1

Baseline Tc-99m SPECT myocardial perfusions scan from CRT candidate demonstrating a fixed perfusion defect involving anterior and anterolateral wall consistent with transmural scar. Intraoperative testing demonstrated a high pacing threshold at anterolateral LV lead position; excellent pacing threshold was obtained from a posterolateral coronary sinus branch.

Figure 2

Baseline ECG from CRT super responder showing several predictors of good response including sinus rhythm, long PR interval, typical LBBB with mid-QRS slurring in lateral leads, QRS duration >200 ms, and long LVAT_max⁡ measured by subtracting RVAT from the QRS duration. Arrow indicates the end of RVAT.