Outcomes by rescue shock number during the metabolic phase of porcine ventricular fibrillation resuscitation

Time boundaries of the three-phase time-sensitive model for ventricular fibrillation cardiac arrest

Aim

Ventricular fibrillation (VF) cardiac arrest may consist of three time-sensitive phases: electrical, circulatory, and metabolic. However, the time boundaries of these phases are unclear. We aimed to determine the time boundaries of the three-phase model for VF cardiac arrest.

Methods

We reviewed 20,741 out-of-hospital cardiac arrest cases with initial VF and presumed cardiac origin from the All-Japan Utstein-style registry between 2013 and 2017. The study endpoint was 1-month neurologically intact survival. The collapse-to-shock interval was defined as the time from collapse to the first shock delivery by emergency medical service personnel. The patients were divided into the bystander cardiopulmonary resuscitation (CPR, n = 11,606) and non-bystander CPR (n = 9135) groups.

Results

In the bystander CPR group, the collapse-to-shock times that were associated with increased adjusted 1-month neurologically intact survival, compared with those in the non-bystander CPR group, ranged from 7 min (42.9% [244/4999] vs. 26.0% [119/458], adjusted odds ratio [aOR], 1.95; 95% confidence interval [CI], 1.44-2.63; P < 0.0001) to 17 min (17.1% [70/410] vs. 7.3% [21/288], aOR, 2.82; 95% CI, 1.62-4.91; P = 0.0002). However, the neurologically intact survival rate of the bystander CPR group was statistically insignificant compared with that of the non-bystander CPR group when the collapse-to-shock time was outside this range.

Conclusions

The time boundaries of the three-phase time-sensitive model for VF cardiac arrest may be defined as follows: electrical phase, from collapse to <7 min; circulatory phase, from 7 to 17 min; and metabolic phase, from >17 min onward.

Early Effects of Prolonged Cardiac Arrest and Ischemic Postconditioning during Cardiopulmonary Resuscitation on Cardiac and Brain Mitochondrial Function in Pigs

BACKGROUND

Out-of-hospital cardiac arrest (CA) is a prevalent medical crisis resulting in severe injury to the heart and brain and an overall survival of less than 10%. Mitochondrial dysfunction is predicted to be a key determinant of poor outcomes following prolonged CA. However, the onset and severity of mitochondrial dysfunction during CA and cardiopulmonary resuscitation (CPR) is not fully understood. Ischemic postconditioning (IPC), controlled pauses during the initiation of CPR, has been shown to improve cardiac function and neurologically favorable outcomes after 15min of CA. We tested the hypothesis that mitochondrial dysfunction develops during prolonged CA and can be rescued with IPC during CPR (IPC-CPR).

METHODS

A total of 63 swine were randomized to no ischemia (Naïve), 19min of ventricular fibrillation (VF) CA without CPR (Untreated VF), or 15min of CA with 4min of reperfusion with either standard CPR (S-CPR) or IPC-CPR. Mitochondria were isolated from the heart and brain to quantify respiration, rate of ATP synthesis, and calcium retention capacity (CRC). Reactive oxygen species (ROS) production was quantified from fresh frozen heart and brain tissue.

RESULTS

Compared to Naïve, Untreated VF induced cardiac and brain ROS overproduction concurrent with decreased mitochondrial respiratory coupling and CRC, as well as decreased cardiac ATP synthesis. Compared to Untreated VF, S-CPR attenuated brain ROS overproduction but had no other effect on mitochondrial function in the heart or brain. Compared to Untreated VF, IPC-CPR improved cardiac mitochondrial respiratory coupling and rate of ATP synthesis, and decreased ROS overproduction in the heart and brain.

CONCLUSIONS

Fifteen minutes of VF CA results in diminished mitochondrial respiration, ATP synthesis, CRC, and increased ROS production in the heart and brain. IPC-CPR attenuates cardiac mitochondrial dysfunction caused by prolonged VF CA after only 4min of reperfusion, suggesting that IPC-CPR is an effective intervention to reduce cardiac injury. However, reperfusion with both CPR methods had limited effect on mitochondrial function in the brain, emphasizing an important physiological divergence in post-arrest recovery between those two vital organs.

β-adrenergic receptor-mediated cardiac contractility is inhibited via vasopressin type 1A-receptor-dependent signaling

BACKGROUND

Enhanced arginine vasopressin levels are associated with increased mortality during end-stage human heart failure, and cardiac arginine vasopressin type 1A receptor (V1AR) expression becomes increased. Additionally, mice with cardiac-restricted V1AR overexpression develop cardiomyopathy and decreased β-adrenergic receptor (βAR) responsiveness. This led us to hypothesize that V1AR signaling regulates βAR responsiveness and in doing so contributes to development of heart failure.

METHODS AND RESULTS

Transaortic constriction resulted in decreased cardiac function and βAR density and increased cardiac V1AR expression, effects reversed by a V1AR-selective antagonist. Molecularly, V1AR stimulation led to decreased βAR ligand affinity, as well as βAR-induced Ca(2+) mobilization and cAMP generation in isolated adult cardiomyocytes, effects recapitulated via ex vivo Langendorff analysis. V1AR-mediated regulation of βAR responsiveness was demonstrated to occur in a previously unrecognized Gq protein-independent/G protein receptor kinase-dependent manner.

CONCLUSIONS

This newly discovered relationship between cardiac V1AR and βAR may be informative for the treatment of patients with acute decompensated heart failure and elevated arginine vasopressin.