Abstract 17184: An Increase in the Respiratory Effort Immediately Intensifies the Hemodynamic Congestion; a Mechanism for Progressive Cardiac Decompensation

Introduction: An increase in the pulmonary wedge pressure (PCWP) is associated with an increase in the respiratory effort and the sensation of dyspnea. Hypothesis: We investigated the inverse cause and effect relationship, whether an increase in the respiratory effort can by itself aggravate the hemodynamic congestion. Methods: We scrutinized the cardiopulmonary interactions by simultaneously measuring hemodynamic and respiratory indices in heart failure (HF) patients undergoing right heart catheterization. The immediate effects of the respiratory effort on the hemodynamic indices were analyzed by asking the patients to perform short events of apnea and intentional vigorous breathing. The cardiac waves are superimposed on the respiratory waves in the PCWP. To quantify the respiratory effort, the PCWP was decomposed into cardiac and respiratory waves. The respiratory effort (PRESP) was defined as the peak to peak swing in the respiratory wave that modulated the PCWP. Results: HF patients (n=38) exhibited a high PRESP of 9.0±3.2 mmHg, ~3.5-fold higher than the reported normal respiratory effort. The end-expiratory PCWP rose with PRESP, by 0.83±0.06 mmHg for every 1 mmHg of PRESP (p<0.01). The pulmonary artery pressure (PAP) rose with PRESP by 1.40±0.09 mmHg for every 1 mmHg of PRESP. The changes in the respiratory effort had immediate effect on PCWP, within a single breathing-cycle (t =1.67±0.40 s) in all patients. Interestingly, similar changes in the PCWP with PRESP were obtained in all the patients, independently of the HF etiology. Conclusions: An increase in the respiratory effort is not just a result of cardiac decompensation. The respiratory effort has immediate detrimental effects on the PCWP, PAP and the workloads of the heart. The results highlight the existence of a cardiopulmonary vicious cycle the can lead to progressive decompensation, where the respiratory effort plays a pivotal role.