Tag: defibrillation

Categories : Cardiovascular Disease Emergency MedicineTags :

Defibrillation Using 1/1000th the Energy could be Possible

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Photo by Mikhail Nilov

Researchers from Sergio Arboleda University in Colombia and the Georgia Institute of Technology in the US used an electrophysiological computer model of the heart’s electrical circuits to examine the effect of the applied voltage field in multiple fibrillation-defibrillation scenarios. Their research, published in the interdisciplinary journal Chaos, discovered that far less energy is needed than is currently used in state-of-the-art defibrillation techniques.

“The results were not at all what we expected. We learned the mechanism for ultra-low-energy defibrillation is not related to synchronisation of the excitation waves like we thought, but is instead related to whether the waves manage to propagate across regions of the tissue which have not had the time to fully recover from a previous excitation,” author Roman Grigoriev said. “Our focus was on finding the optimal variation in time of the applied electric field over an extended time interval. Since the length of the time interval is not known a priori, it was incremented until a defibrillating protocol was found.”

The authors applied an adjoint optimization method, which aims to achieve a desired result, defibrillation in this case, by solving the electrophysiologic model for a given voltage input and looping backward through time to determine the correction to the voltage profile that will successfully defibrillate irregular heart activity while reducing the energy the most.

Energy reduction in defibrillation devices is an active area of research. While defibrillators are often successful at ending dangerous arrhythmias in patients, they are painful and cause damage to the cardiac tissue.

“Existing low-energy defibrillation protocols yield only a moderate reduction in tissue damage and pain,” Grigoriev said. “Our study shows these can be completely eliminated. Conventional protocols require substantial power for implantable defibrillators-cardioverters (ICDs), and replacement surgeries carry substantial health risks.”

In a normal rhythm, electrochemical waves triggered by pacemaker cells at the top of the atria propagate through the heart, causing synchronised contractions. During arrhythmias, such as fibrillation, the excitation waves start to quickly rotate instead of propagating through and leaving the tissue, as in normal rhythm.

“Under some conditions, an excitation wave may or may not be able to propagate through the tissue. This is called the ‘vulnerable window,’” Grigoriev said. “The outcome depends on very small changes in the timing of the excitation wave or very small external perturbations.

“The mechanism of ultra-low-energy defibrillation we uncovered exploits this sensitivity. Varying the electrical field profile over a relatively long time interval allows blocking the propagation of the rotating excitation waves through the ‘sensitive’ regions of tissue, successfully terminating the irregular electric activity in the heart.”

Source: American Institute of Physics

Categories : Cardiovascular Disease Emergency MedicineTags : 1 Comment

New Approach to Defibrillation may Improve Cardiac Arrest Outcomes

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Joshua Lupton, MD, has no memory of his own cardiac arrest in 2016. He only knows that first responders resuscitated his heart with a shock from a defibrillator, ultimately leading to his complete recovery and putting him among fewer than one in 10 people nationwide who survive cardiac arrest outside of a hospital.

He attributes his survival to the rapid defibrillation he received from first responders – but not everybody is so fortunate.

Now, as lead author on an observational study published in JAMA Network Open, he and co-authors from Oregon Health & Science University say the study suggests the position in which responders initially place the two defibrillator pads on the body may make a significant difference in returning spontaneous blood circulation after shock from a defibrillator.

“The less time that you’re in cardiac arrest, the better,” said Lupton, assistant professor of emergency medicine in the OHSU School of Medicine. “The longer your brain has low blood flow, the lower your chances of having a good outcome.”

Researchers used data from the Portland Cardiac Arrest Epidemiologic Registry, which comprehensively recorded the placement position of defibrillation pads from July 1, 2019, through June 30, 2023. For purposes of the study, researchers reviewed 255 cases treated by Tualatin Valley Fire & Rescue, where the two pads were placed either at the front and side or front and back.

They found placing the pads in front and back had 2.64-fold greater odds of returning spontaneous blood circulation, compared with placing the pads on the person’s front and side.

The current common knowledge among health care professionals is that pad placement – whether front and side, or front and back – is equally beneficial in cardiac arrest. The researchers cautioned that their new study is only observational and not a definitive clinical trial. Yet, given the crucial importance of reviving the heartbeat as quickly as possible, the results do suggest a benefit from placing the pads on the front and back rather than the front and side.

“The key is, you want energy that goes from one pad to the other through the heart,” said senior author Mohamud Daya, MD, professor of emergency medicine in the OHSU School of Medicine.

Placing the pads in the front and back may effectively “sandwich” the heart, raising the possibility that the electrical current will be delivered more comprehensively to the organ. 

However, that’s not readily possible in many cases. For example, the patient may be overweight or positioned in such a way that they can’t be easily moved.

“It can be hard to roll people,” said Daya, who also serves as medical director for Tualatin Valley Fire & Rescue. “Emergency medical responders can often do it, but the lay public may not be able to move a person. It’s also important to deliver the electrical current as quickly as possible.”

In that respect, pad placement is only one factor among many in successfully treating cardiac arrest.

Lupton survived his cardiac arrest and went on to complete medical school at the very hospital where he spent several days recovering in the intensive care unit – Johns Hopkins University in Baltimore. The episode led him to alter the focus of his research so that he could examine ways to optimise early care for cardiac arrest patients.

The results of the new study surprised him.

“I didn’t expect to see such a big difference,” he said. “The fact that we did may light a fire in the medical community to fund some additional research to learn more.”

Source: Oregon Health & Science University

Categories : Cardiovascular DiseaseTags :

A Model for Gentler Defibrillation for the Heart

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Photo by Stephen Andrews: https://www.pexels.com/photo/shallow-focus-of-electrocardiogram-9408866/

Using light pulses as a model for electrical defibrillation, Göttingen scientists developed a method to assess and modulate the heart function. This has paved the way for an efficient and direct treatment for cardiac arrhythmias. This may be an alternative for the strong and painful electrical shocks currently used.

Cardiac arrhythmias account for around 15-20% of annual deaths worldwide. In case of acute and life-threatening arrhythmias, defibrillators can be used to restart the regular beating of the heart. A strong electrical pulse brings cardiac activity to a brief standstill before it can be resumed in an orderly way. Whereas this treatment can save lives very effectively, the strong electrical pulses can also have negative side effects such as damage of the heart tissue or strong pain.

“We developed a new and much milder method which allows the heart to get back into the right rhythm,” says Stefan Luther, Max Planck Research Group leader at the MPI-DS and professor the University Göttingen Medical Center. “Our results show that it is possible to control the cardiac system with much lower energy intensity,” he continues.

To test their method, the scientists, from the Max Planck Institute for Dynamics and Self-Organization (MPI-DS) and the University Göttingen Medical Center, used genetically modified mouse hearts that can be stimulated by light. In this setting, a sequence of optical light pulses is triggered using a closed-loop pacing algorithm. Each pulse is triggered in response to the measured arrhythmic activity.

With this pacing protocol, the team was able to effectively control and terminate cardiac arrhythmias even at low energy intensities that do not activate the heart, but only modulate its excitability.

“Instead of administering a single high-energy shock to restore normal heart rhythm, we use our understanding of the dynamics of cardiac arrhythmias to gently terminate them.” explains Sayedeh Hussaini, first author of the study.

“This results in a subtle treatment method with far less energy per pulse, more than 40 times less compared to the conventional strategy” she reports.

The research team will also use these findings to improve the control of arrhythmias using electrical pulses. This may result in advanced defibrillators causing less pain and side-effects for patients.

Source: Max Planck Institute for Dynamics and Self-Organization

Categories : Cardiovascular Disease Emergency MedicineTags :

Better Survivor Outcomes One Year after Cardiac Arrest When Bystanders Perform Defibrillation

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Survivors of out-of-hospital cardiac arrest (OHCA) who received initial bystander defibrillation with a nearby automated external defibrillator (AED) reported better outcomes at 12 months after arrest compared with those initially defibrillated by paramedics, according to a new study from Monash University which appears in Heart.

The retrospective study recruited adult non-traumatic OHCA with initial shockable rhythms between 2010 and 2019. Survivors at 12 months after arrest were invited to participate in structured telephone interviews. Outcomes were identified using the Glasgow Outcome Scale-Extended (GOS-E), EuroQol-5 Dimension (EQ-5D), 12-Item Short Form Health Survey and living and work status-related questions.

Of 6050 patients, 3211 (53.1%) had a pulse on hospital arrival, while 1879 (31.1%) were discharged alive. Survival rates were highest with bystander defibrillation (52.8%), followed by dispatched first responders (36.7%) and paramedics (27.9%). Of the survivors, 1802 (29.8%) survived to 12-month post-arrest; of these 1520 (84.4%) were interviewed. 1088 (71.6%) were initially shocked by paramedics, 271 (17.8%) by first responders and 161 (10.6%) by bystanders. Bystander-shocked survivors reported higher rates of living at home without care (87.5%), upper good recovery (GOS-E=8) (41.7%) and EQ-5D visual analogue scale (VAS) ≥ 80 (64.9%) compared with first responder and paramedics, respectively. After adjustment, initial bystander defibrillation was associated with higher odds of EQ-5D VAS ≥ 80 (adjusted OR (AOR) 1.56), good functional recovery (GOS-E ≥ 7) (AOR 1.53), living at home without care (AOR 1.77) and returning to work (AOR 1.72) compared with paramedic defibrillation.

Categories : Cardiovascular DiseaseTags :

Better Outcomes with Earlier Adrenaline Treatment in Cardiac Arrest

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Earlier adrenaline treatment during a cardiac arrest is linked to better recovery compared to later treatment, according to preliminary research to be presented at the American Heart Association’s Resuscitation Science Symposium (ReSS) 2021.

“Our study’s findings should guide emergency medical services professionals towards earlier administration of epinephrine [adrenaline] during out-of-hospital cardiac arrest management,” said lead study author Shengyuan Luo, MD, MHS, an internal medicine resident physician at Rush University Medical Center in Chicago.

Previous research found that only about 1 in 5 people survive a cardiac arrest outside of the hospital and those who do survive often have long-term impairment in the ability to perform daily living tasks.

During a cardiac arrest, immediate CPR (cardiopulmonary resuscitation) is critical. For some types of cardiac arrest, an AED (automated external defibrillator) also is used to deliver an electric shock through the chest to the heart to restore a heartbeat. For these ‘shockable’ cardiac arrests, adrenalineis injected to help restore blood flow. Previous research indicated that adrenaline should be given after three unsuccessful electric shocks with an AED, however, it was unclear whether it should be given even earlier – such as after the first electric shock.

To compare the effects of earlier versus later administration of adrenaline, the researchers examined medical records to compare epinephrine timing to patient recovery. Study subjects included 6416 multi-ethnic adults across North America who had an out of hospital cardiac arrest with shockable initial rhythm from 2011-2015. They were an average age of 64 years, and most were men.

Overall, adrenaline administration within four minutes after the first shock from an AED was associated with greater chances of recovery, while administration after four minutes was associated with reduced chances. Specifically, people who received adrenaline after four minutes were nearly half as likely to have heartbeat and blood flow restored before hospital admittance and half as likely to survive to hospital discharge or be able to perform daily tasks, as measured by a standard test, at discharge. Additionally, the risks of later adrenaline treatment rose with each minute of delayed treatment.

“It is crucial that whenever a cardiac arrest event is suspected, the emergency medical system be notified and activated immediately, so that people with cardiac arrest receive timely, life-saving medical care,” Dr Luo said.

These findings support the latest American Heart Association CPR and Emergency Cardiovascular Care Guidelines, which were released in October 2020. The guidelines indicate adrenaline should be administered as early as possible to maximise good resuscitation outcome chances. The guideline recommendation was based on previous observational data that suggest better outcomes when adrenaline is given sooner.

Source: EurekAlert!