Study Results Support Ventilatory Expired Gas Analysis at Low-Intensity Exercise
as Valuable Insight to Prognosis and Cardiac Stability in Heart Failure Patients
Minneapolis-St. Paul, MN (November 18, 2009) – The Journal of Cardiac Failure published results from a recent study showing that ventilatory expired gas analysis during a short bout of low-intensity exercise may provide insight into prognosis and cardiac stability in heart failure patients. Ventilatory efficiency and the partial pressure of end-tidal carbon dioxide, obtained during moderate to high levels of physical exertion, have been widely accepted to demonstrate prognostic value in heart failure. This study validates the method of testing at or below anaerobic threshold used with the Shape-HF™ Cardiopulmonary Exercise Testing System, a new non-invasive medical device that assesses heart-lung interaction and ventilation in patients with chronic heart failure and other cardiopulmonary disease’s method of testing at or below the anaerobic threshold.
“Cardiopulmonary exercise testing (CPX) has been used for many years to help doctors understand the pathophysiology of heart failure,” says Dean MacCarter, Ph.D., one of the study’s authors. “During maximal exercise testing key measurements can guide physicians in their clinical decision making. But conducting CPX tests at such levels comes with its own set of problems. The tests require a maximal physical effort by the patient, they require specialized training to conduct, and interpreting the results can be challenging. We wanted to determine the value of measuring key parameters during low-level, or submaximal, exercise,” MacCarter continued. “Our results show that important prognostic measures in heart failure are as good as, and in some cases superior to, similar measures obtained during peak exercise. What’s important about this research is that it shows that clinically relevant information can be obtained using a test that is more simple, less costly, and requires less staffing than standard tests. Importantly, the test is easier on the patient, and provides highly relevant clinical information related to a heart failure patient’s status and stability.”
The study involved testing 130 subjects diagnosed with heart failure. As part of the exercise protocol, each underwent a two-minute, constant-rate, treadmill session at two miles per hour. Both the ventilatory efficiency (VE/VCO2 ratio) and the partial pressure of end-tidal carbon dioxide (PETCO2) were recorded during low level exercise and their change (Δ) from rest. B-type and atrial natriuretic peptide (BNP and ANP) were also determined. Only PETCO2 and ∆ PETCO2 emerged from the multivariate Cox regression. Receiver operating characteristic curve analysis revealed the prognostic classification schemes were significant with thresholds of ETCO2 and ∆ PETCO2, respectively. Moreover, subjects with a PETCO2 of ≥ 34 mmHg had a significantly lower BNP (214.1 ± 1854.0 pg/mL, p=0.005) and ANP (108.2 ± 103.6 vs. 246.2 ±200.4 pg/mL, p< 0.001).
Shape-HF™ Cardiopulmonary Exercise Testing System
The Shape-HF™ System is the first gas exchange testing device specifically designed for cardiology. It is FDA-approved, easy to use, easy on the patient, and provides clinically relevant data that is easy to understand, reproducible and immediately useful to a cardiologist. Shape-HF™ quantifies the severity of dyspnea and fatigue on exertion and evaluates the interaction between the heart, lungs, and other organ systems involved in oxygen uptake and transport. This makes it possible for the physician to evaluate therapy options for the individual patient and track patient progress. In addition, cardiac resynchronization therapy (CRT) has become a mainstay in treating patients with advanced heart failure when alternative treatment options have been exhausted. The Shape-HF test takes 15 minutes and involves measuring ventilation parameters while the patient exercises on a treadmill at a very low intensity. As the patient exercises at a steady state heart rate, the physician adjusts the pacemaker therapy settings every two minutes, enough time for the adjustments to be reflected in breathing physiology. At the end of the test, during which four to five therapy settings are tested, the Shape-HF System uses a proprietary computer algorithm to rank the physiological response to exercise at each setting. The physician then reviews the results and chooses the therapy setting he or she believes is most appropriate for the patient.
The Shape test also quantifies the heart rate response to exercise to determine if it is appropriate and can unmask potential co-morbidities that may adversely affect heart failure prognosis or therapy response. The Shape-HF System is the only device that objectively measures cardiopulmonary gas exchange easily and quickly without undue strain on the patient. It can be used in the office setting and provides real-time physiological assessment to help physicians elucidate the physiological underpinnings of dyspnea, objectively assess patient functional classification, monitor therapy response and progress, identify potential co-morbidities, and optimize CRT at exercise levels consistent with patient daily activity. Importantly, Shape-HF exercise testing is cost-effective and easy to use.
Shape Medical Systems Inc. is a privately held, St. Paul, Minnesota-based medical device company whose core technology lies in the development and commercialization of products for assessing heart/lung interaction and ventilation in chronic heart failure and other cardiopulmonary disease. Shape's clear mission is to develop products that increase the quality of patients' lives by helping doctors quantify shortness of breath, assess patient functional capacity, optimize drug, device and rehabilitation therapy, and monitor patient progress. Shape testing provides evidence based outcomes. Shape Medical Systems was founded in 2004 and received FDA market clearance for the Shape-HF™ Cardiopulmonary Testing System in April 2009. The Shape-HF™ System, testing protocols and applications are protected by patent 7,225,022 and other U.S. and foreign patents issued and pending.
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