Influence of cardiomegaly on disordered breathing during exercise in chronic heart failure

AimsHeart failure (HF) patients breathe with a rapid shallow pattern during exercise. This study examined the relationship between cardiac size and tachypnoeic breathing in HF patients during exercise.Methods and resultsThirty-seven HF patients [age 55 ± 13 years, ejection fraction (EF) 27 ± 10, New York Heart Association (NYHA) class 2.3 ± 1.2] and 42 controls (CTL) (age 56 ± 14 years, EF 63 ± 8) were recruited. Participants underwent maximal exercise testing, pulmonary function testing, and chest radiography for calculation of total thoracic cavity volume (TTCV), diaphragm, heart, and lung volumes. Heart failure patients were divided into two groups: Group A cardiac volume < median (n 18) and Group B cardiac volume < median of the HF patients (n 19). There was no difference between groups for TTCV (CTL 8203 ± 1489 vs. Group A 8694 ± 1249 vs. Group B 8195 ± 1823 cm³). Cardiac volume was different between groups for both absolute (CTL 630 ± 181 vs. Group A 894 ± 186 vs. Group B 1401 ± 382 cm³, P< 0.001 for all comparisons) and TTCV (CTL 8 ± 2 vs. Group A 10 ± 1 vs. Group A 18 ± 5, P< 0.001 for all comparisons). Similarly, total lung volume as a TTCV was significantly different among the groups (CTL 70 ± 4 vs. Group A 65 ± 5 vs. Group A 58 ± 7, P< 0.01 for all comparisons). In HF patients, there was a trend (P 0.10) towards an independent association between cardiac size and tidal volume (VT) at 75 of VO₂ peak whereas this relationship was statistically significant at VO₂ peak (P= 0.02) as patients with larger cardiac size had reduced VT.ConclusionThis study demonstrates the close relationship between cardiac size and breathing pattern during exercise in HF patients. These results suggest cardiac size may pose a significant constraint on the lungs during exercise and may contribute to tachypnoeic breathing.