BIV pacing in moderate-to-severe HF
For patients with moderate-to-severe HF (NYHA class III– IV), CRT has
been shown in 4 trials (MUSTIC SR, MIRACLE, CONTAK-CD,
MIRACLEICD1,2,22,23) to provide improvements in NYHA
functional class, exercise capacity (measured by the 6-minute hall walk
distance) and peak oxygen consumption and quality of life.
The CARE-HF study randomized patients to either CRT plus optimal medical
therapy or CRT alone. It was the first trial showing that CRT without an
ICD prolonged survival and reduced both morbidity and mortality, with
the effect sustained over 37 months of follow up24.
Similarly, in the COMPANION trial, Bristow et al have shown that BiVP
decreased the combined risk of death from any cause or first
hospitalization and, when combined with an implantable cardioverted
defibrillator (ICD), significantly reduces mortality7.
A meta-analysis of 6 randomized, controlled trials of CRT for more
severe, chronic, symptomatic LV systolic dysfunction found that CRT was
associated with a 28% reduction in all-cause mortality and a 37%
reduction in new hospitalizations for exacerbation of
HF25.
In the COMPANION trial, patients with advanced heart failure (NYHA III
or IV) due to ischemic or nonischemic cardiomyopathies and a QRS
interval of at least 120 msec were randomly assigned to receive optimal
pharmacologic therapy alone or in combination with CRT with either a
pacemaker or a pacemaker–defibrillator. The primary composite end point
was the time to death from or hospitalization for any cause. As compared
with optimal pharmacologic therapy alone, CRT with a pacemaker or a
defibrillator significantly decreased the risk of the primary end point.
The risk of the combined end point of death from or hospitalization for
heart failure was also significantly reduced in the pacemaker and the
defibrillator groups7. The CARE-HR trial enrolled
patients with NYHA class III or IV heart failure due to left ventricular
systolic dysfunction and cardiac dyssynchrony to receive standard
pharmacologic therapy alone or with cardiac resynchronization. The
primary end point was the time to death from any cause or an unplanned
hospitalization for a major cardiovascular event. The principal
secondary end point was death from any cause. As compared with medical
therapy alone, CRT significantly decreased the risk of the primary
endpoints. Also, CRT significantly reduced the interventricular
mechanical delay, the end-systolic volume index, and the area of the
mitral regurgitant jet; increased the left ventricular ejection
fraction; and improved symptoms and the quality of
life8.