Random fluctuations of ventricular fibrillation (VF) affect defibrillation; in addition, the heart is more susceptible to defibrillation at a higher absolute VF voltage (AVFV). Shocks delivered at higher A VFV waveforms from a single lead of the electrocardiogram (ECG) are more effective than conventional shocks. The authors investigated a new sensing method using multiple leads for better representation of the depolarization state of the heart. In this non-thoracotomy defibrillation study, a vector waveform derived from three orthogonal surface leads X, Y, and Z was analyzed in real time using two distinct defibrillation lead configurations, P1: RV- coil electrode (-) mutually implies (SVC-coil electrode + SCP) (+); and P2: RV-coil electrode (+) mutually implies (SVC-coil electrode + SCP) (-), where (-) represents cathode and (+) anode for the first phase of biphasic shock (RV - right ventricle, SVC = superior vena cava, SCP = subcutaneous patch). A PC-based closed-loop waveform-processing system, the peak-shock method (PSM), was developed to analyze the vector waveforms and trigger a biphasic shock at an A VFV peak. In using this defibrillation technique, an empirical threshold was applied to a weight function consisting of short-term and long-term moving averages of the vector VF waveform. A total of 340 shock trials in nine canine studies resulted in a significantly higher defibrillation success rate for the PSM compared with the conventional random-shock method (RSM), which involved shocking after a fixed VF time (54% for the PSM versus 42% for the RSM, p < 0.03). This further confirms that a susceptible period for defibrillation occurs during VF. The hardware/software design satisfied the requirements for processing the VF vector waveform in real time, and with the help of signal-processing techniques the high VF voltage could be detected as it occurred in real time. In addition, the P2 defibrillation lead configuration was significantly better than the P1 (p < 0.006).
|Original language||English (US)|
|Number of pages||14|
|Journal||Biomedical Instrumentation and Technology|
|State||Published - Jan 1 1998|
ASJC Scopus subject areas
- Biomedical Engineering
- Computer Networks and Communications