212: Ultrasound cardiac output monitor measurements in pediatric cardiac transplant patients

Abstract

Purpose: The ultrasound cardiac output monitor (USCOM) is an FDA approved non-invasive device that can quickly determine cardiac output based on outflow tract velocity measured by continuous doppler and outflow valvular surface area deduced by patients’ height and weight. This investigation examines USCOM measurements in pediatric cardiac transplant patients. Methods and Materials: Following IRB approval and informed consent, USCOM readings were obtained during routine outpatient visits from June to August 2006. Measurements included cardiac index (CI), aortic valve diameter (AVD) and velocity through the aortic valve (VAV). Aortic valve velocities were compared to readings obtained by echocardiogram (ECHO) performed using the paired t-test with statistical significance at p-value 0.05. Results: 16 boys and 15 girls met study entry criteria. Mean age was 11.5 years and mean weight was 42.2 kg (range 12.3 to 146 kg). A single USCOM reading was obtained on each patient. Each USCOM measurement took less than 10 minutes to perform. USCOM derived mean CI was 4.42 L/min/m( /1.74). Mean USCOM VAV (1.13 /0.36 m/sec) was no different than that measured by ECHO (1.14 /0.16 m/sec), p 0.46. However, mean USCOM derived AVD (1.69 cm) was smaller than that measured by ECHO (2.32 cm). This is attributable to fact that the cardiac grafts are typically larger than the recipients’ expected AVD calculated using height and weight. All children appeared healthy and active on discharge from clinic. One child later requiring ICU admission for sepsis had a 50% decrement in CI from his USCOM baseline which also correlated with moderate to severe decrease in graft function on ECHO. Conclusions: VAV in children undergoing heart transplantation obtained by the USCOM device appeared no different from that measured by ECHO, though measured and calculated AVD may vary. USCOM derived CI appears to reasonably portray these patients’ clinical condition. USCOM may be a useful rapid screening tool to assess deviations from the baseline in pediatric heart transplant recipients.