A rapid ultrasonic cardiac output monitor method for optimization of ventriculo-ventricular interval (VVI) in cardiac resynchronization therapy.

Abstract

OBJECTIVES: Ventriculo-ventricular Interval Optimization (VVO) is critical for cardiac resynchronization therapy (CRT). However, this is usually a labor-intensive, expensive and time consuming procedure. The Ultrasonic Cardiac Output Monitor (USCOM Ltd, Australia) is a portable, 2D independent hemodynamic monitor that uses a special 2.2 MHz transducer over the supra-sternal notch to measure aortic flow to compute minute distance (MD, a reflection of cardiac output, CO). PATIENTS (PTS) AND METHODS: We studied 7 pts with CRT (mean age 70±8) with the mean EF (24±9%) at recruitment. AVO was first performed by an echo physician using the Ritter’s formula. After determining the optimal AV interval, the highest Doppler trans-aortic flow determined CO and the highest MD from the aortic Doppler at 11 VV intervals (RV80, RV60, RV40, RV20, RV12, 0, LV12, LV20, LV40, LV60 and LV80) in random sequence by the same echo physician and a nurse who were blind to the sequence. RESULTS: The Doppler and USCOM determined VVI were all within 20ms. 5 pts (71%) had 100% concordant in VV interval, the remaining 2 pts had VVI difference within 20ms. The USCOM determined VVI were well correlated with the Doppler determined VVI. (r2 0.92, p<0.01) However, the mean durations USCOM was significantly shorted than trans-aortic Doppler determined CO. (47±14 min vs 89±8 min p <0.001). CONCLUSION: Echo-independent USCOM determined MD allows rapid VVO without the need of specialized echo-machine and personnel. USCOM may be a cost-effective device for hemodynamic optimization of VV interval for CRT pts.