Characterizing the Agonal Phase of the Non-Heart Beating Donor in Canines – Implications for Utilization of DCD Hearts for Transplantation

Abstract

Purpose Donation after cardiac death (DCD) has increased the donor pool for abdominal organ and lung transplantation but is not generally considered for cardiac transplantation. In the United States, the definition of cardiac death varies widely among hospitals but most commonly is defined as loss of pulse/heart sounds, loss of arterial wave form, or loss of electrical activity. The purpose of the current study was to investigate the agonal phase of DCD donation in a large animal model to evaluate the time to cardiac death using these definitions and assess potential implications for heart transplantation. Methods and Materials Adult mongrel dogs (n=5) were anesthetized and instrumented with a left ventricular catheter. Baseline hemodynamic data were obtained. Animals were then disconnected from the ventilator. Hemodynamic data were then collected at two minute intervals until flat line of the LV catheter. Time to loss of pulse, loss of pressure wave form and cessation of electrical activity/ventricular fibrillation were measured. Data are reported as mean ± standard error of the mean. Results Hearts experienced an initial period of tachycardia and hypertension after cessation of ventilation. This was followed by a rapid decline in left ventricular pressure. Loss of pulse and the pressure wave form were relatively consistent between animals occurring at 7.4±.7 min (range 5-9 min) and 9.8±.5 min (range 9-11 min), respectively. Electrical silence was variable and occurred at 30.1±7.3 min (range 11-43 min). Conclusions The definition of cardiac death may have important implications for recovery of DCD hearts for transplantation. Loss of pulse is an early event associated with ongoing cardiac contractile function and has the greatest potential for organ recovery. Flat line of the pressure wave is a later but relatively predictable event. Electrical activity can persists for a long periods of warm ischemia and likely will not yield acceptable hearts for transplantation using conventional preservation techniques.