Effects of cardiac resynchronization therapy on disease progression in patients with congestive heart failure

Cardiac resynchronization therapy (CRT) represents a new therapeutic modality of proven efficacy for selected patients with heart failure and ventricular asynchrony. The aim of this study was to assess the effects of CRT on clinical variables and cardiac remodeling in patients with moderate-to-severe congestive heart failure and inter/intraventricular conduction delays.

Thirty-seven patients (32 males, 5 females, mean age 73 +/- 7 years), in NYHA functional class III-IV, with left ventricular ejection fraction (LVEF) < or = 35%, QRS > or = 150 ms, and left ventricular end-diastolic diameter (LVEDD) > or = 55 mm, underwent CRT by biventricular pacing (InSync, InSync III, InSync ICD; Medtronic Inc.). Fourteen (37.8%) had a previous pacemaker, and 11 (29.7%) were in permanent atrial fibrillation. The QRS width, NYHA functional class, LVEDD, left ventricular end-systolic diameter (LVESD), left ventricular end-diastolic volume (LVEDV), left ventricular endsystolic volume (LVESV), and LVEF were retrospectively evaluated in the period before CRT. For the purposes of the present study, the pre-CRT period was divided in two: T(-2) (from 6 to 3 years) and T(-1) (from 3 years to CRT). Moreover, these parameters were measured at the time of CRT (T0) and prospectively in the post-CRT follow-up (Tp).

Before CRT, a progressive worsening of the parameters was observed. The QRS duration steadily increased from T(-2) to T(-1) and T0 (both p = 0.000). The NYHA functional class increased from T(-2) to T(-1) and T0 (both p = 0.000). LVEDD and LVESD also increased and were higher at T(-1) (p = 0.001 and p = 0.000, respectively) and at T0 (both p = 0.000) compared to T(-2). Similar results were observed for LVEDV and LVESV. Finally, LVEF was higher at T(-2) than T(-1) and T0 (both p = 0.000). After CRT, there was a reduction in the QRS duration and an improvement in the NYHA functional class compared to T0 (both p = 0.000). LVEDD and LVESD were also reduced (p = 0.005 and p = 0.016, respectively), LVEDV and LVESV decreased (both p = 0.000), and LVEF increased (p = 0.000) with respect to T0. A highly significant correlation was found between LVEDD and LVESD both in the pre- and post-CRT time intervals, with a non-significant difference between the two linear regression lines. Similar results were obtained for the correlations between LVEDV and LVESV.

Congestive heart failure is associated with a progressive widening of the QRS complex and a worsening of the clinical status and results in anatomic remodeling with deterioration of the left ventricular function. CRT induces opposite changes in QRS duration, clinical status, and left ventricular remodelling.