Quantitative waveform measures of the electrocardiogram as continuous physiologic feedback during resuscitation with cardiopulmonary bypass

Abstract

Background: There are few if any real-time physiologic measures that currently provide feedback during resuscitation from cardiac arrest. Such measures could be used to guide therapy not simply based on process guidelines but on the physiologic response of the patient from moment to moment. To this end, we applied an existing technology - quantitative waveform measures (QWMs) of the ventricular fibrillation (VF) electrocardiogram (ECG) - as a continuous measure of myocardial response to reperfusion with cardiopulmonary bypass (CPB) after prolonged cardiac arrest.

Methods: Sixteen domestic, mixed-breed swine were sedated, anesthetized and paralyzed. Mechanical ventilation with room air was provided. Large diameter bypass catheters were placed in the right external jugular vein and right femoral artery for cardiopulmonary bypass (CPB). VF was induced with a 3-s 100mA transthoracic shock and left untreated for 15, 20, 25, or 30min, followed by 10min of centrifugal pump CPB (Bard CPS). Continuous Lead II ECG was recorded with an electronic data acquisition system (Power Lab, ADInstruments). Four QWMs representing 4 signal characteristics of the VF ECG were calculated in 5-s windows throughout the course of untreated VF and resuscitation with CPB.

Results: Four animals were assigned to each VF duration group. QWM recovery was inversely correlated with untreated VF duration, and was drastically reduced above 20min of untreated VF. Return of spontaneous circulation (ROSC) was highly unlikely after 20min of untreated VF.

Conclusion: QWMs of the VF ECG provided a real-time metric of myocardial electrophysiologic response to reperfusion with CPB. Resuscitation from greater than 20min of untreated cardiac arrest was unlikely. QWMs may be useful for titrating CPB duration before defibrillation and assessing CPR quality independently of process guidelines.

Figure 1. Sample ECG Traces at Key Experimental Time Points

A. Early coarse VF converts over 15 minutes to lower amplitude, lower frequency VF. B. Early coarse VF converts over 20 – 30 minutes to asystole. C. 15-minute VF converts over 10 minutes of CPB resuscitation to coarse VF. D. 20-minute asystole converts over 10 minutes of CPB resuscitation to coarse VF. E. 25–30 minute asystole converts over 10 minutes of CPB resuscitation to asystole with visible atrial artifact. F. 25–30 minute asystole converts over 10 minutes of CPB resuscitation to irregular, wide complex PEA.

Figure 2. Continuous Time Course of QWMs Throughout Untreated VF and Subsequent Resuscitation with CPB

15VF – Animals with 15 minutes of untreated VF, 20VF – Animals with 20 minutes of untreated VF, 25VF – Animals with 25 minutes of untreated VF, 30VF – Animals with 30 minutes of untreated VF.

Figure 3

Recovery Proportion of Median Slope QWM Over Time for 10 minute Resuscitation with CPB