title: Early Changes in QRS Frequency Following Cardiac Resynchronization Predict Hemodynamic Response in Left Bundle Branch Block Patients.
abstract: QRS characteristics are the cornerstone of patient selection in cardiac resynchronization therapy (CRT) and the presence of left bundle branch block (LBBB) and baseline QRS ≥150 milliseconds portends a good outcome. We previously showed that baseline QRS frequency analysis adds predictive value to LBBB alone and have hypothesized that a change in frequency characteristics following CRT may produce additional predictive value.
  
  
  
  We examined the QRS frequency characteristics of 182 LBBB patients before and soon after CRT. Patients were assigned to responder and nonresponder groups. Responders were defined by a decrease in left ventricular end-systolic volume (LVESV) ≥15% following CRT. We analyzed the QRS in ECG leads I, AVF, and V3 before and soon after CRT using the discrete Fourier transform algorithm. The percentage of total QRS power within discrete frequency intervals before and after CRT was calculated. The reduction in lead V3 power <10 Hz was the best indicator of response.
  
  
  
  Baseline QRS width was similar between the responders and nonresponders (162.2 ± 17.2 milliseconds vs. 158 ± 22.1 milliseconds, respectively; P = 0.180). Responders exhibited a greater reduction in QRS power <10 Hz (-17.0 ± 11.9% vs. -6.6 ± 12.5%; P < 0.001) and a significant AUC (0.743; P < 0.001). A ≥8% decline in QRS power <10 Hz produced the best predictive values (PPV = 84%, NPV = 59%). Importantly, when patients with baseline QRS <150 milliseconds were compared, the AUC improved (0.892, P < 0.001).
  
  
  
  Successful CRT produces a significant reduction in QRS power below 10 Hz, particularly when baseline QRS <150 milliseconds. These results indicate that QRS frequency changes after CRT provide additional predictive value to QRS alone.
authors.affiliation: Cleveland Clinic, Cleveland, Ohio, USA.
authors.forename: Mark J
authors.initials: MJ
authors.lastname: Niebauer
authors.affiliation: Cleveland Clinic, Cleveland, Ohio, USA.
authors.forename: John
authors.initials: J
authors.lastname: Rickard
authors.affiliation: Cleveland Clinic, Cleveland, Ohio, USA.
authors.forename: Patrick J
authors.initials: PJ
authors.lastname: Tchou
authors.affiliation: Cleveland Clinic, Cleveland, Ohio, USA.
authors.forename: Niraj
authors.initials: N
authors.lastname: Varma
mesh_terms: D000200:Action Potentials; D000368:Aged; D000465:Algorithms; D019540:Area Under Curve; D002036:Bundle of His / Q000503:physiopathology*; D002037:Bundle-Branch Block / Q000175:diagnosis / Q000503:physiopathology / Q000628:therapy*; D058406:Cardiac Resynchronization Therapy; D004562:Electrocardiography; D005260:Female; D005583:Fourier Analysis; D006333:Heart Failure / Q000175:diagnosis / Q000503:physiopathology / Q000628:therapy*; D006339:Heart Rate; D006801:Humans; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D012372:ROC Curve; D012189:Retrospective Studies; D013318:Stroke Volume; D013997:Time Factors; D016896:Treatment Outcome; D016277:Ventricular Function, Left
keywords: biventricular pacing; cardiac resynchronization therapy; frequency analysis; heart failure; left bundle branch block