P‐wave Morphology Is Associated with Echocardiographic Response to Cardiac Resynchronization Therapy in MADIT‐CRT Patients

BACKGROUND: In this study we hypothesized that signs of atypical atrial activation would be associated with cardiac resynchronization therapy (CRT) response in patients with mildly symptomatic heart failure (CHF), left ventricular dysfunction, and wide QRS complex. METHODS: Patients included in the CRT-D arm in MADIT-CRT were studied (n = 892). Unfiltered signal-averaged P waves were analyzed to determine orthogonal P-wave morphology (typical morphologies were predefined as having positive signals in Leads X and Y and a negative or negative-positive signal in Lead Z. All other patterns were classified as atypical). The association between P-wave morphology and data on echocardiographic response at 1 year was analyzed. RESULTS: Atypical P-wave morphology was found in 21% (n = 186) of the patients at baseline. Patients with atypical P-wave morphology were more often female (31% vs. 24%, P = 0.025), had lower BMI (28 ± 5 kg/m(2) vs. 29 ± 5 kg/m(2) , P = 0.008), had more ischemic CHF (60% vs. 52%, P = 0.026) and had smaller left atrial volumes (90 ± 20 mL vs. 94 ± 22 mL, P = 0.034). Atypical P-wave morphology at baseline was associated with superior response to CRT at 1 year with a larger reduction in left ventricular end-diastolic volume (-23 ± 12% vs. -20 ± 11%, P = 0.009), left ventricular end-systolic volume (-36 ± 16% vs. -31 ± 16%, P = 0.006), and left atrial volume (-31 ± 12% vs. -27 ± 12%, P = 0.005), with a slightly larger absolute increase in left ventricular ejection fraction (LVEF) (12 ± 5% vs. 11 ± 5%, P = 0.009). These associations were found to be independent of traditional predictors. CONCLUSION: The presence of atypical P-wave morphology recorded is independently associated with a favorable echocardiographic cardiac remodeling response to CRT.