Assessment of AAIR Pacing Treatment for Heart Failure Patients With Chronotropic Incompetence

CI is the inability of the heart to increase its rate in response to increased physical activity or metabolic demand, leading to exercise intolerance and poor quality of life. Studies have demonstrated that patients with CI have a high risk of cardiac morbidity and mortality. Recent studies further demonstrate a high incidence of CI in patients with heart failure, which is also confirmed by CI in Heart Failure Study Phase I. However, clinical attention is often paid to heart failure symptoms instead CI-related symptom. Thus, patients with heart failure are often not tested for CI, even though the CI incidence is high in these patients. Moreover, such patients could gain significant improvements in exercise tolerance and quality of life once they get diagnosed followed by effective therapy for CI and long-term management. This study is designed to establish clinical evidence that AAIR pacing is beneficial to treat CI-caused symptoms in heart failure patients, which will improve the life quality of such patients and further support the expansion of Brady therapy indications to the population of HF with CI in existing markets and also potential markets. CI is rarely seen and has different definition among various animal species. It is impossible to use animals to get wanted data for AAIR pacing treatment to CI. Thus, a human clinical study is necessary. Furthermore, exercise testings, such as 6 minutes hall walk (6MHW) and treadmill, allow objective evaluation of exercise capacity and exertional symptoms, which have been suggested as other investigations for HF in "ESC Guidelines for the diagnosis and treatment of acute and chronic heart failure 2012". Therefore, exercise testings will be applied upon physicians' need or judgment. Firstly, this study is to assess the effect of AAIR pacing treatment for HF patients with CI in terms of exercise tolerance and quality of life. Specifically, the study will assess the changes in cardiac function associated with changes of physical exercise intensity and heart rate in AAIR pacing mode compared with AAI pacing mode. Secondly, the study will look at clinical outcomes in terms of NYHA class, 6MHW, blood BNP, Echo measurements following pacemaker therapy for 1 year. 6MHW and treadmill tests have been suggested as other investigations for HF in "ESC Guidelines for the diagnosis and treatment of acute and chronic heart failure 2012" and will be performed upon physicians' need or judgment. The study will enroll up to 30 subjects that meet the indication for pacing therapy. Consented subjects will receive pacing therapy and two follow-ups in the following one year.