Refractory ventricular fibrillation remains a problem for out of hospital cardiac arrests, despite advances in treatment. While ventricular fibrillation is often treatable, there is a subset of cases that do not respond to repeated attempts at traditional defibrillation. Recent studies have suggested that double sequence defibrillation may be useful as in these patients. Double sequence defibrillation is a defibrillation technique wherein 2 shocks are delivered within quick succession. This study aimed to utilize a local EMS protocol in conjunction with a highly trained EMS unit to determine if double-sequence defibrillation results in improved outcomes in those patients with refractory ventricular fibrillation (RVF). RVF is generally considered to exist after 3 shock attempts.
This was a retrospective, observational study that observed 18 months of data from 24 paramedics specially trained in the use of double sequence defibrillation (DSD). All patients who received DSD following standard defibrillation attempts (defined as 6 shocks in this case) were included in the study. Likewise, to compare against the DSD patients, those patients with RVF treated with standard defibrillation were identified. Outcomes measured included pre-hospital ROSC, ROSC sustained to hospital, and survival to hospital discharge.
45 total patients were treated by these specialized paramedics over the 18 month period. Over the same time period, 175 patients were treated with standard defibrillation. In the DSD group, ROSC was obtained in 37 8% of patients, with 58.8% of those sustaining ROSC to the hospital. Only 3 patients (7%) survived to hospital discharge. Very similar results were noted in the non-DSD group. 34.9% achieved ROSC, 55.7% of those sustained ROSC to the hospital, and 6.6% survived to hospital discharge.
Our group discussed the multiple limitations of this study. First and foremost, the study looked at a very small sample size of only 45 total patients. Additionally, a lack of randomization and blinding are significant limitations. Demographically, the DSD group was noted to have a significantly higher proportion of witnessed arrests as compared to the non-DSD group. There was additionally no obvious ACLS standardization, and there is concern that these specially trained paramedics may be performing differently than standard paramedics in the field. They had also previously stated that the generally accepted definition of RVF occurred after 3 shocks, but placed in the protocol not to perform DSD until after 6 standard defibrillation attempts. In summary, there were many limitations to this study, but it certainly warrants further research.
Impact of total occlusion of culprit artery in acute non-ST elevation myocardial infarction: a systematic review and meta-analysis
Total occlusion of culprit artery usually results in a ST-elevation myocardial infarction. However, there is a subset of patients with elevated troponin without ST-segment elevation who are found on PCI to have total occlusion. The purpose of this study was to identify if there is a significant different in outcomes between NSTEMIs with and without total occlusion of the culprit artery.
This was a systematic review and meta-analysis of 7 studies that compared clinical outcomes of NSTEMI patients with partial, total, or non-occluded culprit arteries. Identification of studies was performed by the two lead authors, and disagreements on study inclusion was resolved with discussion between them. Quality of the included studies were measured by the Newcastle-Ottawas Scale, which assesses the methodological quality of cohort studies. Outcomes measured included all-cause mortality and major cardiac adverse events (MACE). Secondary parameters measured included Killip class, LVEF, and time to angiography.
A total of 40, of 700 patients were included in the analysis, of which 25.5% had total occlusion of the culprit artery. The frequency of culprit artery in the total occlusion group was noted to be RCA (40%) > LCX (32%) > LAD (28%), whereas the non-total occlusion group had a frequency of LAD (44%) > LCX (28%) > RCA (27%). In all of these cases, there was a lack of classic ST-elevation on EKG. Short term all-cause mortality was noted to be increased in the total occlusion group, with RR of 1.67, and medium to long term all-cause mortality was noted to be increased as well with a RR of 1.42. Likewise, patents with total occlusion had increased risk of MACE, with a relative risk of 1.41.
Although the studies included were all noted to be observational studies, and there may have been differences in EKG interpretation between the included studies, our group commended this meta-analysis for its good study inclusion. We discussed that while the line between STEMI and NSTEMI can be ambiguous, it's important to recognize that some of our patients with NSTEMIs can have what is essentially a "silent" STEMI, and to take extra care when interpreting EKGs and determining proper disposition. Additionally, we discussed the importance of always checking old EKGs, as there are often EKG changes besides ST-segment changes that may suggest a more serious etiology.
Refractory ventricular fibrillation treated with esmolol
Refractory ventricular fibrillation (RVF) remains a problem for out of hospital cardiac arrests, despite advances in treatment. While ventricular fibrillation is often treatable, there is a subset of cases that do not respond to repeated attempts at traditional defibrillation. Various animal studies, including case reports and case series, have reported success with the use of beta-blockers in RVF. However, there is limited evidence for the efficacy of adjunctive beta-blocker use versus traditional therapy. The purpose of this study is to evaluate the use of esmolol as a treatment for RVF in out-of-hospital cardiac arrests.
This was a single center retrospective pre-post study that followed patients from 2012 to 2013 who did not receive esmolol as part of their treatment for RVF, and compared outcomes to patients followed from 2014 to 2015 who did receive esmolol for the RVF treatment. Verbal consent for esmolol use was given by patients' relatives located at the bedside during resuscitation, with written consent obtained following the resuscitation. Outcomes measured included sustained ROSC without recurrence of RVF primarily, with secondary outcomes measured being survival to ICU admission, survival to discharge, and survival with favorable neurological outcomes.
16 patients were identified from the study group (post-phase) as having RVF, and 25 patients from the control group (pre-phase). Sustained ROSC was noted to be more common in the esmolol group, noted to be 56% versus 16% for the standard treatment group. The esmolol group additionally had better rate of survival to ICU admission (again 56% to 16%), but the difference in survival and survival with good neurological outcome was noted to be statistically insignificant.
Our group primarily discussed the chief limitation of this study: size. The study and control populations were very small, and large variations in data can exist when sample sizes are not sufficiently large. Additionally the nature of a pre-post study versus a randomized controlled trial allows significant bias to emerge. The study did note a statistically significant difference in rate of achieving ROSC between esmolol and non-esmolol groups. We discussed that is is possible for this study to change practice, in that we could use it as a last option, but that we would likely need more data, possibly in a multi-center randomized clinical trial, to make this a regular part of practice.
Submitted by Dr. Will Morris, PGY-1