Dean MacCarter, Ph.D. Addressed Differentiation of Responder vs Non-Responder CRT Status with Low Level Exercise at the Heart Failure Society of America 13th Annual Scientific Meeting
By Elise Schadauer

Introduced new objective method for optimizing CRT in heart failure patients

during exercise that may significantly impact outcomes for non-responders


Minneapolis-St. Paul, MN (September 17, 2009) – Speaking at the recent Heart Failure Society of America 13th Annual Meeting, September 13 to 16, Dean MacCarter, Ph.D., Vice President Clinical Affairs for Shape Medical Systems, Inc., addressed how breathing efficiency measurements during low level exercise may offer a better discriminator for CRT responder and non-responder outcomes. He also introduced the audience to a new patented method for optimizing therapy in patients with implanted cardiac resynchronization pacemakers. This new method involves using the FDA-approved Shape-HF™ Cardiopulmonary Testing System to measure changes in patient breathing efficiency as cardiac resynchronization therapy (CRT) pacemaker settings are adjusted. In this way, physicians are able to assess the physiological effect of therapy in real time while the patient is exercising at a level consistent with normal daily activity.   

CRT is used in severe cases of heart failure to restore synchrony between the heart chambers during the heartbeat. In patients with advanced heart failure the heart may not beat strongly or efficiently enough to supply adequate oxygen to peripheral tissues (such as active skeletal muscles), and poor blood flow to the lungs disrupts the process of exchanging needed oxygen for carbon dioxide, a waste product of normal metabolism. Combined, these effects lower the amount of oxygen in the blood, which decreases the patient’s ability to exercise and causes inefficient, labored breathing.“Shortness of breath on even mild exertion is a key symptom in heart failure,” says Dr. MacCarter. “We know that a positive response to CRT improves breathing efficiency during exercise, so it makes sense that parameters that can measure patient breathing efficiency can be used to define patient response and determine the proper pacemaker settings for CRT.”


The test involves measuring ventilation parameters while the patient exercises on a treadmill at a very low intensity of one mile per hour with the treadmill set at a minimal 1% to 2% grade. “This is a level of exercise that is consistent with normal daily activity in this patient population,” notes MacCarter. As the patient exercises at a steady state heart rate, the physician adjusts 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 CRT response rate in heart failure patients is about 70%. By using the Shape-HF™ System, physicians may be able to help the remaining 30%—the non-responders—feel better,” says Clarence Johnson, President and COO of Shape Medical Systems. “Because patient breathing efficiency is so sensitive to changes in CRT delay settings, using gas exchange parameters to assess these changes provides a completely objective method for defining response to CRT.”


The Shape-HF System is the only device that objectively measures CRT response in real time while the patient is exercising. The System is cost-effective, easy to use, and the test is easy on the patient. “CRT patients generally believe they should spend most of their time lying on the couch,” said Dr. MacCarter. “Our objective is to get them off the couch, back on their feet and enjoying life again.”


About the Heart Failure Society of America -   The Heart Failure Society of America (HFSA) is a nonprofit educational organization, founded in 1994 as the first organized association of heart failure experts. Today HFSA has over 1,500 members and provides a forum for all those interested in heart function, heart failure research and patient care. The HFSA Annual Scientific Meeting is designed to highlight recent advances in the development of strategies to address the complex epidemiological, clinical and therapeutic issues of heart failure. Additional information on HFSA can be found at


About Shape Medical Systems, Inc. - 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 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.


# # #