Abstract 9792: Chrontropic Incompetence in Heart Failure and the Relationship of Minute Ventilation and Chronotropic Response During Exercise
BACKGROUND: Cardiac pulmonary mismatch is prevalent in heart failure patients that exhibit chronotropic incompetence (CI). Wilkoff’s model provides evaluation of metabolic chronotropic response (MCR) during exercise. In addition to CI we evaluated a new measure of the normalized heart rate to normalized minute ventilation relationship during exercise (HRn/VEn) which,in combination with the MCR slope, may provide discriminating information in regards to identifying those normal subjects and heart failure patients who would most likely benefit from adaptive rate pacing. Normalization allows comparison of subjects and identification of patients with CI regardless of Age, functional capacity, and during submaximal workloads.
METHOD: We studied the resulting MCR slopes and the HRn/VEn slopes in 40 normal subjects (N) (age 37±9) and 40 heart failure patients (HF) implanted with BiV CRT-D devices (age 62±9) during graded exercise testing by using standard cardiopulmonary exercise testing techniques. Exercise tests were performed to peak exercise (as quantified by the respiratory exchange ratio (RER) RER = 1.13±0.09 N and 1.11±0.07 HF) and the end stage heart rate and minute ventilation data was used in the calculations of the MCR slope and HRn/VEn slopes. RESULTS: Mean MCR slopes were 1.0±0.14 (N) and 0.52±0.23 (HF). The mean HRn/VEn slope were 1.34±0.26 (N) and 0.66±0.28 (HF). Details are presented in the table.
DISSCUSION/CONCLUSSION: When CI is present there is also a significant derangement in the heart rate to pulmonary relationship as shown by the HRn/VEn slopes. A MCR slope of 0.7 which is considered to be severely CI corresponds to a decreased HRn/VEn slope of 0.881 (95% confidence interval of the normal relationship). HF CI patients (MCR slopes <0.7) also exhibit low HRn/VEn measures (> 2 standard deviations from the mean of normal group).
- © 2012 by American Heart Association, Inc.