Prospective Observation of Exercise Parameters in Advanced Heart Failure

Overview

To observe and document ventilation parameters in the advanced heart failure population, through the course of illness, which often includes cardiac resynchronization therapy (CRT), left ventricular assist device (LVAD), and transplant. Findings from this cohort are anticipated to be of sufficient interest to the scientific community to merit publication and are likely to provide preliminary data for future hypothesis generation and subsequent prospective, randomized controlled trials. A compact, inexpensive apparatus has recently become commercially available for performing sub-maximal exercise testing (SHAPE Medical, St Paul, MN), including gas exchange analysis and will be used in this study. This apparatus is not investigational.

Cardiopulmonary exercise testing (CPXT) has a long history in the evaluation and management of cardiovascular diseases, particularly in patients with advanced heart failure. Cardiovascular exercise testing is a safe, well-developed, and validated method for risk stratification and objective documentation of exercise capacity in patients with severe heart failure (1,2). Recent studies have also shown that exercise testing has prognostic power for heart failure hospitalization and mortality (3,4), but limited published data are available in a large group of advanced heart failure patients, such as those with cardiac resynchronization therapy (CRT) and left ventricular assist devices (LVAD) Advanced or suspected advanced heart failure. Typical patients screened for this study will be patients who have been referred to the University of Minnesota for evaluation for advanced heart failure options, such as cardiac transplant or mechanical circulatory support. This is a somewhat heterogeneous population, but all have been diagnosed by referring physician as having sufficiently severe heart failure to seek tertiary care. Most are anticipated to have severely depressed ejection fraction (\<30% and typically \<20%), but patients with preserved ejection fraction and either hypertrophy or restrictive cardiomyopathy will also be eligible. Patients pulmonary hypertension, on any therapy (other than diuretics alone), are also felt to be at high risk of developing right heart failure and may also be included. Patients who have already undergone LVAD or cardiac transplant are also considered to have advanced heart failure and are eligible to participate, regardless of the severity of their symptoms at the time of enrollment. Healthy volunteers may be included for comparison. This is a non-randomized, observational investigation of sub-maximal exercise ventilation parameters in patient diagnosed with, or suspected to have, advanced heart failure. Duration of follow-up will be up to five years. Some subjects will undergo only one exercise test. Patients who present with heart failure but subsequently undergo CRT implantation, LVAD implantation, or cardiac transplant will be asked to repeat the submaximal exercise test. The timing between any of these events is unpredictable, so the duration of follow-up cannot be predicted. Subjects will be followed for change of status for up to 5 years. The total number of tests that any one person could potentially have is 5 (baseline plus one after each therapy), although we expect that most participants would not be asked to undergo more than 3 tests. For patients without a device: Patients start at rest for 2 minutes and will wear a face mask and breathing parameters are recorded using the SHAPE-HF system (SHAPE Medical St. Paul, MN) that measures respiratory airflow and the constituent respiratory gases, oxygen and carbon dioxide. The SHAPE-HF system will continue to monitor and the patient then will start walking on a treadmill with a variable speed of 1-3 mph and a variable grade of 0-6%. The total treadmill time will be no more than 10 minutes. For patients with a device: patients will be at rest and the adjustments of their device will be made by a study physician or device coordinator, done routinely in clinical practice. This will take up to 15 minutes and during this time; participants will wear a face mask and breathing parameters are recorded using the SHAPE-HF system (SHAPE Medical St. Paul, MN) that measures respiratory airflow and the constituent respiratory gases, oxygen and carbon dioxide. Device parameters will be returned to baseline settings following this part of the test. Sub-maximal exercise testing approximately 30 minutes in duration will be performed on a treadmill at a slow and constant pace, the speed of the treadmill will range from 1-2 mph and the grade will range from 0-2% depending on the patient's exercise tolerance. The exercise will be split into two rounds of exercise up to 15 minutes each. Subjects may rest as long as they would like between the two tests. The first round, participants will wear a face mask and breathing parameters are recorded using the SHAPE-HF system. (See section 13B for sample report). In the second round, every two minutes, up to 15 minutes, participants will be asked to take 8 breaths using a breathing bag containing a standard mixture of gases (0.7% acetylene, 21% oxygen, 9% Helium and the balance of nitrogen)-this gas mixture is routinely used in pulmonary function laboratories to measure lung function and has the same amount of oxygen as room air. Acetylene mass spectroscopy is then used to measure cardiac output noninvasively. Neither the SHAPE-HF system, nor the methods of gas exchange during exercise are investigational. Participants who are treated with cardiac resynchronization therapy and/or ventricular assist device may have minor adjustments made to their device parameters every 2 minutes during the testing. The adjustments will be made by a study physician or device coordinator, as mentioned before, done in routine practice. Device parameters will be returned to baseline settings following the test.