Hearts too good to die
In 1961 the Journal of the American Medical Association (JAMA) published an article titled Hearts too good to die (JAMA, 1961). A total of 500 cases of fatal myocardial infarction were examined. The authors reported that 60–70% of all cases had no myocardial disease or acute coronary syndrome. Indeed, the majority of the victims were healthy and tragically killed by a sudden and random electrical event. An excerpt from the article follows:
[…] Of every 10 such victims, the heart in 6 or 7 showed no recent disease in coronary arteries or in heart muscle. In other words, the heart today is anatomically the same as it was yesterday except that an electrical charge developed which fibrillated the heart. This electrical factor came and killed and disappeared and was not found in the dead heart. The cause of death in these victims is not explained on the basis of morbid anatomy. This is not a new experience for either the pathologist or the internist. That there is something lacking in our understanding of this problem is indicated when death occurs after the victim was given “a clean bill of health” and no explanation of death […]
Saving hearts that are too good to die is the goal of cardiopulmonary resuscitation (CPR).
Sudden cardiac arrest and death
Cardiac arrest is the mechanism of death for most diseases and conditions, including non-cardiovascular conditions. A cardiac arrest can be expected or unexpected. The most common cause of cardiac arrest is cardiovascular disease. Sudden unexpected cardiac arrests cause 50% of all deaths from cardiovascular disease. Approximately 50% of these deaths are the first manifestation of cardiovascular disease. Furthermore, sudden cardiac arrests account for 50% of all years of life lost due to cardiovascular disease (Myerburg et al). Sudden unexpected cardiac arrest is the mechanism of death for about half of all individuals with heart failure (Packer et al) and 30% of people with diabetes (Cavallari et al).
Organizational challenges in cardiac arrest
Optimal management of sudden cardiac arrest requires comprehensive efforts and resources, ranging from continuously training laymen in the community to establishing advanced post-resuscitation care. Since the majority of all sudden cardiac arrests occur outside hospitals, the chain of care includes laymen, emergency dispatchers, ambulance, first-responders (police, fire brigade, rescue services), the emergency room, intensive care unit (ICU), coronary care unit (CCU), regular wards and rehabilitation facilities. Depending on the cause of the arrest, other units may be critical (e.g. trauma unit). Careful and evidence-based planning at the societal level (e.g. CPR education programs) and local level (e.g. EMS protocols, in-hospital protocols, etc) is necessary to improve outcomes in out-of-hospital cardiac arrest (OHCA) and in-hospital cardiac arrest (IHCA).
Initiating or withholding CPR
In cases of an unexpected cardiac arrest in an individual with any likelihood of survival, cardiopulmonary resuscitation (CPR) should be started. If cardiac arrest is an expected consequence of a disease course (e.g. terminal cancer, terminal heart failure, etc), CPR should not be started. Moreover, CPR should not be started if it is evident that survival is impossible. The term do not attempt CPR (DNACPR) describes circumstances and conditions in which CPR should be withheld in order to avoid futile attempts or subjecting the individual (and the relatives) to unwanted interventions. Unfortunately, during the stressful circumstances surrounding a sudden cardiac arrest, uncertainty may arise with regard to no-flow time, low-flow time, patient preferences, patient background, and the decision to initiate CPR is often ambiguous. Since the risk of attempting CPR is extremely low and the potentially catastrophic consequences of wrongfully withholding an attempt, CPR is often initiated in individuals who are biologically dead or in whom resuscitation should not be attempted. Such CPR attempts are often terminated early and the initiation of CPR provides additional time for consideration. Because myocardial necrosis (myocardial infarction) occurs later than cerebral infarction (20 minutes vs. 4 minutes), futile resuscitation attempts may induce cardiac electrical activity, despite manifest biological death (brain death). Such cardiac activity ceases within minutes of terminating ventilation.
Time is neurons
The importance of time can not be overstated in cardiac arrest. Immediate CPR is essential in order to save the individual. CPR should be started as soon as a cardiac arrest is suspected. Individuals with out-of-hospital cardiac arrest should be transported immediately to the hospital with uninterrupted CPR. Survival in OHCA ranges from 3% to 20%; the large regional differences are explained by variations in criteria for initiating CPR, differences in inclusion criteria in various studies/registries and uncertainty due to small samples in some countries. The median age at OHCA is 66 years and 66% of all cases are male (Gräsner et al). The median time to CPR is 1 minute in IHCA, while the delay to ambulance/EMS arrival in OHCA has doubled from 5 minutes to 11 minutes between 1990 and 2021 (Jerkeman et al).
Ventricular arrhythmias
Ventricular tachycardia (VT) is relatively common in individuals with structural heart disease (e.g heart failure, ischemic heart disease, etc). Although most VTs terminate spontaneously, rapid VT (particularly in individuals with left ventricular dysfunction) may cause syncope and cardiovascular collapse. Coronary perfusion will then be reduced markedly, causing the VT to progress to ventricular fibrillation (VF) and cardiac arrest. This condition is highly unlikely to resolve spontaneously.
Paroxysmal ventricular fibrillation (VF) may also occur in various situations (e.g in advanced heart failure, in acute myocardial ischemia, etc). While a few seconds of VF may be asymptomatic, the risk of cardiac arrest is very high and VF resulting in cardiac arrest is highly unlikely to resolve spontaneously.
Death (biological death) occurs within minutes (5-6 minutes) of cardiac arrest unless CPR is started immediately. Immediate and efficient CPR can generate 20–25% of normal cardiac output, which is enough to postpone fatal cerebral injuries for several minutes, until ROSC can be achieved.
Emerging therapies: ECMO
ECMO can be potentially life-saving for a highly selected sub-group of patients. ECMO alarms are activated with pre-hospital or in-hospital protocols. Several slightly different ECMO criteria have been proposed and evaluated; they differ slightly with regard to limits for age, no-flow time, low-flow time, initial rhythm, time to ECMO cannulation, etc. The core principles are, however, whether the condition is potentially reversible and whether the long-term prognosis is good. The purpose of ECMO is to create time for definitive measures to take effect or be initiated. The scientific basis for the use of ECMO in cardiac arrest is ambiguous (Suverein et al). Approximately 20% of patients receiving ECMO survive out-of-hospital cardiac arrest (Nolan et al).
Continued education and preparation
All professionals and healthcare systems who manage patients with cardiac arrest should undergo continuous CPR training and evaluation of cardiac arrest protocols and performance. Performance is evaluated using validated outcome measures (e.g. 30-day survival, cerebral performance among survivors, survival to hospital discharge, time to CPR, time to EMS arrival, time to first defibrillation).
