P5271Non-invasive monitoring of peripheral and cardiac influence on exercise limitation in patients with heart failure with preserved ejection fraction

Abstract

Background: Heart failure (HF) is a major reason for mortality and morbidity in societies all over the world and will gain importance in an aging society. About half of HF patients suffer from heart failure with preserved ejection fraction (HFpEF) which is till now neither fully understood nor treatable. The main symptom of these patients is exercise limitation. Current data provides evidence that this limitation is caused by both cardiac and peripheral influences. Monitoring of these influences in cardiopulmonary exercise testing (CPET) can therefore be of big interest, e.g. when assessing effects of a yet to develop HFpEF therapy. Methods: To provide an insight into the limitations caused by HFpEF, we recruited 51 subjects of same gender and BMI distribution that suffered from either arterial hypertension (HT) without any sign of HF (n=24, 58% male, BMI 29.3±6.4) or HFpEF (n=27, 56% male, p=1.000, BMI 28.2±4.1, p=0.455) for the ENDO-CEC trial. To assess their individual grade of exercise limitation all subjects performed a standardized six minute walking test (6-MWT) and completed CPET protocol in which non-invasive cardiac output monitoring (NICOM) by bioreactance was conducted simultaneously. Results: As expected, HFpEF subjects were significantly limited in all exercise related parameters. They reached a lower maximum power stage at CPET (HT: 121±10, HFpEF: 100±20 Watt, p=0.001), had a lower maximum cardiac index (HT: 6.8±1.3, HFpEF 6.0±1.2 l/min/m2, p=0.029), a lower VO2 at maximum exertion (HT: 22.7±5.9, HFpEF: 17.9±2.0 ml/kg/min, p=0.001) and a higher VE/VCO2 slope (HT: 29.8±4.1, HFpEF: 33.0±4.8, p=0.019). Additionally they covered a shorter distance in 6-MWT (HT: 538±81, HFpEF 470±67m, p=0.005). Non-invasive monitoring of cardiac function shows us that the lower maximum cardiac index in HFpEF patients is not caused by reduction in stroke volume recruitment (HT: 151±16, HFpEF 176±53, percentage of maximum stroke volume compared to minimal stroke volume, p=0.036) but only by a reduced peak heart rate (HT: 81±10, HFpEF: 71±14 percent of predicted maximum heart rate, p=0.011). HFpEF subjects were furthermore slightly but insignificantly limited peripherally, meaning in their arteriovenous oxygen difference (AVDO2) calculated using the Fick principle (HT: 134±33, HFpEF 121±28, milliliter oxygen difference per liter blood flow per minute p=0.155). When looking at the AVDO2 alone one finds that 57% of all HFpEF subjects had an AVDO2 below average with only 33% of HT subjects respectively. The lowest AVDO2 values were all reached by HFpEF subjects while the highest values were reached by HT subjects. Conclusion: NICOM during CPET can show that HFpEF subjects are both centrally and to a certain extent peripherally limited during exercise compared to HT subjects. This is why a combined CPET and NICOM assessment can be of use for monitoring changes in HFpEF patients, e.g. in interventional pharmacological trials.