Author + information
- N. Kumar,
- S. Chaudhry,
- A. Bagai,
- N. Kumar,
- D. Popovic and
- R. Arena
Cardiac resynchronization therapy (CRT) is a valuable approach to improving clinical status in patients with heart failure (HF). Given the changes in cardiac function and geometry, parallel improvements in cardiorespiratory fitness (CRF) can also be expected. The current analysis assesses: 1) Improvement in peak oxygen consumption (VO2); 2) the ability of peak oxygen consumption (VO2) to predict and correlate with echocardiographic improvements in HF patients who underwent CRT.
Twelve subjects (age = 64.3 ±13.1 years, 10 male/2 female) diagnosed with HF underwent cardiopulmonary exercise testing (CPET) on a cycle ergometer and Doppler echocardiography prior to and following CRT. Mean time between assessments was 6.5 ±4.1 months. Peak VO2 and peak respiratory exchange ratio (RER) were the primary endpoints for CPET while left ventricular ejection fraction (LVEF), left atrial (LA) size and right ventricular systolic pressure (RVSP) were primary endpoints for Doppler echocardiography.
Following CRT, there were statistically significant (p<0.05) improvements in: 1) peak VO2 (12.2 ±3.0 vs. 15.5 ±2.5 mlO2·kg-1·min-1); 2) LVEF (28.3 ±6.0 vs. 40.0 ±7.1%); 3) LA size (38.4 ±19.6 vs. 34.1 ±15.6 mm); and RSVP (31.3 ±15.5 vs. 25.2 ±11.9 mmHg). Peak RER was not significantly different between CPETs (1.01 ±0.10 vs. 1.04 ±0.10), indicating similar effort between tests. There was a significant negative correlation between baseline peak VO2 and both with change in LA size (r=-0.72) and change in RSVP (r=-0.63) post CRT. Change in peak VO2 post CRT significantly correlated with change in LVEF (r=0.60) and LA size (r=0.82). Peak VO2 at baseline significantly correlated with change in peak VO2 (r=-0.59) post CRT.
CRF has recently been proposed as a vital sign. The results of the current study indicate peak VO2 holds value in predicting the magnitude of echocardiographic improvement in patients with HF undergoing CRT. Patients with a lower peak VO2 at baseline appear to derive greater benefit. Assessment of peak VO2 in patients being considered for CRT may provide beneficial clinical information with respect to likelihood of therapeutic impact.