"This study represents the first major breakthrough in the management of heart failure in nearly a decade,” said William Abraham, one of the co-principal investigators of the study from the Division of Cardiovascular Medicine at The Ohio State University Medical Centre (Columbus, Ohio). “For the first time instead of managing symptoms or weight gain the device allows us to directly manage patient’s pulmonary pressures.”
Despite current drug and device therapies, the rate of hospitalisation from heart failure remains unacceptably high, indicating the need for better tools to manage heart failure patients.
The CardioMEMS pulmonary artery pressure measurement system utilises catheter based delivery systems, involving right heart catheterization, to introduce the pressure sensor (which is about the size of a small paper clip) into the pulmonary artery. Using radiofrequencies, the sensors transmit real time pressure data to external electronic readers, which then electronically communicate information to the doctor. One of the innovative features of the pressure sensor is that it does not require a battery, since it is powered by radiofrequency communication from the external electronic reader.
“Identifying early rises in pulmonary arterial pressure is important because it’s the most direct sign of congestion,” said Abraham, adding that until now the only available approach was for patients to monitor weight gain, which has a low sensitivity in predicting heart failure hospitalisations of only 10 to 20 %. “The idea is that if we identify elevated pressures we can quickly treat patients proactively, titrating their medications to bring them back into the normal range, thereby overting episodes of heart failure decompensation where patients often need emergency room admissions.”
The phase III CardioMEMS Heart Sensor Allows Monitoring of Pressure to Improve Outcomes in NYHA Class III Heart Failure Patients (CHAMPION) Trial randomised 550 subjects, with NYHA Class III heart failure, who had been hospitalised for heart failure within the past 12 months, to the treatment arm, where management was based on hemodynamics and traditional information (n=270), and the control arm where management was based solely on traditional info (n=280). All patients in the study had the device implanted, but in the control arm clinicians were blinded to the resulting data. The trial, which was conducted at 63 sites in the US, started in October 2007, and recruited its final patient in September 2009.
The primary safety results showed zero sensor failures over six months, and eight device or system related complications, a number considered by the investigators to be extremely low.
The primary efficacy results show that in the first six months there were 83 hospitalisations in total for heart failure in the treatment arm in comparison to 120 hospitalisations in total in the control arm (relative risk reduction 30%, p<0.0001). Over the entire period of the study (averaging 15 months) there were 154 hospitalisations in total in the treatment arm in comparison to 254 in the control arm (annualized relative risk reduction 38%, P<0.0001). “This suggests a progressive improvement in results with time. This is a new approach to treating heart failure, and clinicians need to go through a learning curve. Furthermore there is a cumulative beneficial effect – fewer hospitalisations in the early stages of the trial mean that patients are less likely to have subsequent hospitalisations,” explained Abraham.
Further results show that the change from baseline in mean pulmonary artery pressure over six months was substantially reduced in the treatment group versus the control group, which demonstrated increases in pulmonary pressures (P=0.008). The number of individual patients hospitalised over the course of six months was 54 in the treatment group versus 80 in the control group (P=0.022). The mean number of days alive outside hospital at six months was 177.1 in the treatment group versus 175.9 in the control group (p=0.024). Furthermore at six months answers to the Minnesota Living with Hearth Failure Questionnaire ( a way to score quality of life) produced mean scores of 45 in the treatment group versus 51 in the control group (P=0.024), indicating a better quality of life in treatment patients.
Conclusion:Results of the trial are currently being used for regulatory approval of the CardioMEMS device around the world.