Case 2
A 22-year-old woman with a known history of heroin abuse was brought to our ED by emergency medical services (EMS) following an unwitnessed cardiac arrest pulseless electrical activity (PEA). The patient’s parents stated that when they saw the patient approximately 5 hours earlier, she appeared normal physically and was behaving normally. Emergency medical technicians (EMTs) administered several milligrams of IV naloxone without success. The patient was intubated while en route to the hospital and CPR was performed for 35 minutes, after which ROSC was achieved.
However, en route to the hospital, the patient developed V-fib, for which she was unsuccessfully defibrillated three times at 200 J. Upon arrival at the ED, the patient was defibrillated twice more at 200 J but remained in V-fib. On the third pulse check DSD was performed, and the patient subsequently converted to a PEA rhythm; CPR was continued for two more cycles, after which the patient regained a weak pulse and an ETCO2 of 55 mm Hg. A central line was placed and the patient was started on IV epinephrine and dopamine. In the ICU she received targeted temperature management, but ultimately expired that evening.
Case 3
A 39-year-old woman with no known medical history was brought to the ED by EMS after she was discovered to be unconscious and pulseless by her husband in their home. Upon arrival, the EMTs found the patient in V-fib and performed endotracheal intubation and 30 minutes of CPR. The EMS report recorded that the patient had been defibrillated a total of five times at the scene before achieving ROSC. En route to the hospital, however, the patient’s rhythm reverted to V-fib; CPR was again initiated along with an unsuccessful attempt at defibrillation. The EMTs then administered 300 mg of IV amiodarone, 1 amp of sodium bicarbonate, and epinephrine IV every 3 to 5 minutes.
Upon arrival at the ED, the EP attempted defibrillation twice, unsuccessfully. The patient was then given IV magnesium, 1 amp of sodium bicarbonate IV, and three doses of IV epinephrine, but remained in V-fib. The EP then attempted DSD but with no success, but a second application of DSD resulted in conversion to a junctional bradycardia. After 1 hour of CPR, ROSC was achieved, and the patient was transferred to the ICU. Unfortunately, due to the burden of neurological damage from the cardiac arrest and poor predicted outcome, the patient’s family ultimately decided to have care withdrawn overnight. The patient expired shortly after being extubated.
Discussion
Out-of-hospital cardiac arrest remains a leading cause of death today; of which cardiac arrests due to V-fib are associated with the highest survival rates.4 Our three cases suggest that application of DSD may be of benefit in the ED, in the treatment of refractory V-fib and refractory pulseless V-tach. All three of the patients we described achieved ROSC after DSD and unsuccessful prior attempts with standard defibrillation, though only one of the patients was discharged home with good neurological status.
One of the earliest known studies of the applications of DSD on human subjects was described in 1994 by Hoch et al.5 The study included 2,990 patients who underwent a total of 5,450 electrophysiological studies over a period of 3 years. The researchers induced V-fib/pulseless V-tach in approximately 30% of their study population. Five of these patients, who were all men with a mean age of 55 years, experienced refractory V-fib each of whom required seven to 20 unsuccessful attempts at defibrillation. The researchers ultimately found that when they applied DSD, only one attempt was needed for successful conversion to normal sinus rhythm in all five of the patients.5The authors acknowledged that there were many limitations to their study, which will likely continue to be factors in future studies as well.
DSD exists in the form of reviews, case reports, and retrospective studies in most of the recent literature. The reason for the paucity of research is probably due to the relative rarity and random nature of refractory V-fib (0.1% of V-fib arrests),6 making it nearly impossible for researchers to conduct large-scale studies in a controlled environment. Another limitation that hinders DSD research studies is the large number of variables that can determine a patient’s chance of survival after defibrillation. These variables include age, comorbidities, risk factors, timing of arrival at the ED, application and quality of prehospital CPR, laboratory abnormalities, and other patient-specific neurological or metabolic processes.
Several case series previously reported on the use of DSD, most of which describe patients in the out-of-hospital setting. The findings from these case series appear promising—at least to the extent in which patients were converted out of V-fib through DSD.
In 2014, Cabañas et al6 reported on a retrospective case series of 10 patients treated with DSD between 2008 and 2010, and found that 70% of the patients were successfully converted by DSD out of refractory V-fib. Unfortunately, none of the patients survived to hospital discharge.
Another recent retrospective study conducted by Cortez et al7 of 12 patients with refractory V-fib treated with DSD found that nine of the 12 patients (75%) converted out of V-fib, three of whom survived to hospital discharge, with two patients (16.7%) discharged with a CPC of 1.7 Lastly, Merlin et al8 reported on a retrospective case series in 2015 of EMTs delivering DSS in the field to a total of seven patients with refractory V-fib, five of whom (71%) were successfully converted out of V-fib, with four (57%) surviving to hospital admission.8