A Look at the Strangely-Intermingled Relationship between Heroin and other Opiate-induced Overdoses and Sudden Cardiac Arrest
Heroin overdoses are on the rise all across the United States. This is due to recent governmental policies which restrict access to prescription opioid medications. While these recent initiatives have been implemented with great intentions for public safety, an unintended rebound effect of heroin flooding the streets of major cities all across the United States is currently in progress. With the prevalence of these increased numbers of overdoses coinciding with the media attention given by the recent New Hampshire primaries, the nation is becoming more aware of the problem.
During a heroin overdose, there are many factors at play that contribute to ending the life of the user. As such, sudden cardiac arrest (SCA) is one of these factors. When a heroin user is exhibiting signs of SCA such as agonal respirations, as opposed to other signs that are common during an overdose including labored breathing, it is important these patients not only have access to lifesaving overdose-reversal medications such as Narcan, but also are given access to equally life-saving treatments such as cardiopulmonary resuscitation (CPR) and automated external defibrillator (AED) devices.
It is important that anyone who attempts to respond to a patient known to have overdosed on an opioid be able to differentiate between the signs and symptoms of a strict overdose (i.e., labored, shallow breaths) and the signs of an overdose coexisting with an SCA (agonal respirations or gasping) and provide treatment accordingly.
What Happens During a Heroin Overdose?
In order to understand this topic, it is important to understand the physiology of a heroin or opioid overdose. Heroin is pharmacologically known as diacetylmorphine. It is almost chemically identical to morphine, except it has been reacted with a chemical agent to allow it to cross the blood-brain barrier faster than morphine, resulting in the “rush” that keeps too many users coming back for more.
Heroin and other opioids are known as mu-opioid receptor agonists. Inside the human body, there are interfaces known as opioid receptors which act to regulate pain, among other things. While there are several different types of opioid receptors, the ones active in heroin use are known as “mu” receptors. An agonist to these receptors means that the substance will attach and activate these receptors. When this happens, the way the body interprets pain is altered, which is why opioids are the most effective pain-control substances known to man. A mu-opioid receptor antagonist is a substance which also attaches to these receptors but does not activate them to give the pain-control response and euphoria that is present with agonists. 
When a person overdoses on heroin or another opiate, this is generally due to one of two situations. The first and most common reason for heroin overdoses is due to the unknown purity of the street drug obtained. A user may be accustomed to a product which is approximately 40% pure, and then may unknowingly come across product which has a much-higher purity. When this happens, especially during an injection, the person’s body will not be able to handle the same amount of drug the person normally uses of the lower-purity product, and will go into overdose. The second common situation occurs when an addict has had a substantial amount of sober time and then relapses. These individuals may not take into account their tolerance for the drug has decreased dramatically during their clean time, and then they mistakenly assume their body can handle the same dose it could when they stopped using. The overdose happens in this situation, too, and the symptoms are generally easy to identify.
In a standard opioid/heroin overdose, the individual will generally be almost completely unresponsive, but will still have a pulse. The life threatening condition that occurs during these standard overdoses has to do with the opiate substance’s direct effect on the respiratory system. It dramatically slows down the patient’s respiratory rate until they become hypoxic. As previously mentioned, these people will still have a pulse and will be breathing very, very slowly; sometimes as slow as 4-5 respirations per minute, while the normal, healthy respiratory rate is between 12-20 per minute.  These people will have pinpoint pupils, and if conscious, may be vomiting uncontrollably and acting very confused.
Generally, when a bystander comes across a person
experiencing a life-threatening overdose, the victim
will already be in an almost-unresponsive state. When these overdoses occur, the patient can be given an opioid antagonist, such as naloxone (Narcan®), as described above. This medication will immediately reverse the effects of the culprit opioid, and the patient will very quickly regain a normal breathing pattern and will regain consciousness. A physically-addicted addict will also be thrown into acute withdrawal as the Narcan will eliminate the possibility of and saturation of the mu-receptor by any remaining agonist present. There is currently a large societal effort to make Narcan available to the public for bystander-assisted treatment of an acute opiate overdose, and the American Heart Association has even included a method for bystander-administered emergency injections in their new Guidelines for CPR and ECC. 
SCA-Complicated Overdose Situations
Additionally, there is another type of complication which can occur with these overdoses. Depending on the user’s overall health condition, including any pre-existing cardiac comorbidities, the overdose may actually trigger an instance of sudden cardiac arrest. In these cases, it becomes very confusing for the uninformed bystander who may witness this event, because of the contradictions in how to treat SCA versus how to treat a heroin overdose. Because of this, it is very important the general public be well-educated in the protocol which is most likely to result in survival.
With the overall survival rates of SCA without immediate CPR and AED treatment being less than 10%, it is obviously a pretty grim situation when an individual is suffering from an overdose concurrently complicated with an SCA episode. When this occurs, one must be able to first differentiate between the signs of a simple overdose (pulse still present with labored breathing) versus the signs of SCA (pulse not present, gasping may occur, and patient is completely unresponsive). If the event has been correctly identified as an arrest, the bystander-provider must immediately initiate SCA-specific treatment, including continuous chest compressions as well as AED initiation, if available, until emergency medical services (EMS) arrives at the scene. In localities which currently allow for bystander access to Narcan, a second person can administer the Narcan while the primary responder continues CPR/AED treatment. While the hypoxia from the overdose can be fatal, a person in SCA is already clinically dead, so the primary focus must be on attempting to revive the patient by restarting his/her heart. Without this occurring, the administration of Narcan will do absolutely nothing for the already-dead patient.
Prevention and Prevalence
According to the National Institute of Drug Abuse (2015) , heroin overdoses alone accounted for approximately 12,000 reported deaths in 2014, while deaths from opioid-based prescription drugs tops in at approximately 19,000 during the same time period. These rates have been dramatically on the rise; in 2001, only approximately 4,000 deaths were attributed to these two factors. This is almost an eight-fold increase in the prevalence of opioid-related overdose deaths in the United States, making it a very prominent health crisis which has received much attention. Out of these deaths, it is uncertain how many of them end up with cardiac-related complications, as this data is not reported.
However, even with such an increase in these deaths, the total number of annual cardiac arrest-related deaths is more than a ten-fold increase of all opioid-related deaths combined, and comes in at approximately 350,000. A societal phenomenon has occurred in which more media coverage and public health attention has been allotted to the deaths which occur from these overdoses than the astronomical amount which occur from SCA. There are a few hypothetical explanations for this.
First, using heroin is looked upon as a choice, while suffering an episode of sudden cardiac arrest is not. Also, most overdoses occur due to injected heroin as opposed to other routes of administration, and intravenous drug use in itself is a major public health issue which brings with it the chance of contracting a multitude of diseases if the user decides to share a needle with another user.
Society looks upon these overdoses as deaths which can be easily prevented because the use of these drugs is looked upon as an individual choice of the user. Therefore, more effort is put into treatment programs to prevent future use among addicts. Unfortunately, when dealing with opioids, there is a very high relapse rate because of the physical addiction which occurs with the drug followed by the intense psychological cravings after the physical withdrawal is over.
When it comes to heroin and opioid overdoses, one point of view regarding prevention is very simple and sounds great in theory: heroin overdoses are completely preventable in the most simplistic means possible; abstain from using these drugs altogether. However, in reality, this approach simply does not work because of the aforementioned physiology of the addiction. Many times, ex-users who have been clean for many years will relapse after experiencing some sort of trauma or accident which results in the medical use of opioid painkillers to treat the immediate pain associated with the event. From this point, these ex-addicts are released from the hospital or other medical care and once their prescription runs out, their addictive nature has already taken full control of their mind creating an all-powerful compulsion to use. This is one of the ways where the second reason for overdose described above can come to fruition.
Many times, the societal focus can better serve the public health if risk-lowering protocols are put into place, such as methadone-maintenance treatment programs, where the addict receives a predetermined dose of methadone, a long-lasting opioid agonist, daily by a nurse at a treatment facility. Many times, this approach eliminates the up-and-down instability associated with using drugs such as heroin because the long-lasting nature of methadone keeps the mu-opioid receptors occupied for a full 24-36 hours. Most of these patients are able to return to a normal standard of living as well as find and keep employment.
Sometimes this method of treatment can be used as a stop-gap measure, and after some time of stabilization, the user can then wean off of the methadone under the supervision of medical staff until free from any substance. With other individuals, maintenance treatment is a lifelong process, but the individual will still abstain from using any other opiates. This approach to treatment can be a powerful tool in public health risk reduction by eliminating the use and sharing of injection equipment as well as by preventing overdose from other illicit opiates. Either way the situation is approached, be it through abstinence from all substances, inpatient detoxification and rehabilitation, or via maintenance programs, the problem of opioid-related overdose deaths can be greatly reduced.
Obviously, access to any and all of these treatment options should be available and promoted to the public. In fact, if this visibility of treatment options were to occur, there is a good probability society would begin to again see a decrease in the amount of deaths related to opioid overdose instead of the steady rise which has been experienced so far. This would obviously have an impact on reducing some of the deaths caused by SCA, albeit rather nominal when compared to the overall number of deaths associated with such events.
Keeping all of this in mind, the message to be aware of is these deaths, while dramatically on the rise, are preventable. When compared to the overall number of deaths attributed to sudden cardiac arrest every year, the 31,000 deaths associated with all opioids seems rather miniscule. However, as these deaths can be prevented via abstinence, rehabilitation, and/or methadone maintenance treatment, they will always receive more public attention and scrutiny than the deaths which occur spontaneously due to events such as SCA. In any event, when a patient’s overdose becomes complicated by an episode of sudden cardiac arrest, it then becomes the responsibility of the responder to be able to identify the culprit and respond accordingly.
Having knowledge of the 2015 AHA Guidelines and the procedures for identification of a witnessed event will greatly help in these situations. To sum it up, however, if the patient is known to have just used an opioid and becomes unresponsive, the bystander must evaluate the person for signs of life, such as pulse and true breathing. If the individual is pulseless and gasping, SCA is likely the culprit. Even though a known overdose is occurring, when SCA is involved, the bystander must begin appropriate treatment protocol for SCA. This includes immediately beginning chest compressions and having another person, if available, call 911 while looking for an available AED.
This second individual may also administer the Narcan injection, if available. However, in order for the patient to have a chance of survival, the focus must be on reviving the clinically dead patient via the use of CPR and AED until rescue workers arrive. In most cases, the Narcan will be administered upon arrival and during transport to the receiving hospital. As with all bystander-assisted treatment situations, there is one guiding principle: awareness of the issue and appropriate initiation of treatment is the key to patient survival, be it in the instance of overdose, SCA, or a combination of both.
 Selective antagonists work on specific opioid receptors. When the mu-opioid receptors have been attached to by these antagonists, they produce a blockade effect, which means that the person to which an antagonist has been given will not be able to experience the euphoria associated with the agonists, such as heroin. However, when a person is involved in an opioid overdose, these agonists are able to “compete” for space on the receptors, and as they perform this action, the person experiencing the overdose will immediately have the effects of the opioid overdose reversed, and will sometimes even be thrown immediately into “acute withdrawal.” This is unpleasant, but it acts to save the life of the overdosed addict. This information comes from http://www.opiate.com/antagonist.
 Information comes from http://www.novusdetox.com.
 Details in the Highlights of the 2015 American Heart Association Guideline Updates for CPR and ECC at https://eccguidelines.heart.org/wp-content/uploads/2015/10/2015-AHA-Guidelines-Highlights-English.pdf.
 Statistics for overdose deaths from NIDA are available at http://www.drugabuse.gov/related-topics/trends-statistics/overdose-death-rates.