The news last Thursday was startling.  Laurent Vidal, the 30-year-old French triathlete, reportedly suffered a “heart attack” and cardiac arrest during a swim training session.  You may recall that Vidal is the star of the French triathlon team and finished 5th in the London Olympics.  By report, he complained of chest pain and later collapsed in cardiac arrest.  News accounts indicated that he was revived, regaining consciousness, and was transported to the hospital for further care.  Follow-up reporting suggested that therapeutic hypothermia as well as induced coma had been employed in his treatment.  Over the weekend there was very little reporting, though, at least in the English news media, so I don’t have any additional information about his condition to share here.  On Monday came a Tweet from Vidal:  “Hello world.”  I’ll take that as a good sign and wish Laurent and his fiancé, fellow triathlete Andrea Hewitt, all the best during his recovery.

Interestingly, in a report this morning, came some additional information about Vidal’s medical history.  We learned that Vidal had suffered from exertional syncope (blacking out while exercising) on two previous occasions and had undergone a detailed evaluation after the 2nd episode, in 2011.  At that time he was given the diagnosis of neurocardiogenic syncope, a condition that was thought not to be serious.  I’m sure these previous incidents will be given new consideration in light of Vidal’s cardiac arrest episode.

I can tell from the questions I’ve received about this incident that cardiac arrest remains somewhat of a mystery.  Beyond cardiopulmonary resuscitation (CPR), and possibly the use of an automated external defibrillator (AED), most people don’t have much familiarity with the treatment of victims of cardiac arrest.  Non-medical folks might go a lifetime and never witness such an event.  I thought I’d use Vidal’s story as a starting point for a discussion about the treatment of victims of cardiac arrest.

Cardiac Arrest

We use the term “cardiac arrest” when an individual’s heart has stopped beating effectively.  The victim loses consciousness and stops breathing.  When this happens suddenly, without warning, we use the term “sudden cardiac arrest,” or SCA.  The victim of SCA immediately appears lifeless.

Cardiac arrest is a different problem than “heart attack.”  I’ve written a previous blog post on the terminology of cardiac arrest versus heart attack.  In short, a heart attack occurs when there is complete blockage in one of the coronary arteries that brings blood flow and oxygen to the heart muscle.  This condition typically produces chest pain.  Affected patients are evaluated with coronary arteriography and undergo procedures like coronary stent placement or heart bypass surgery as treatments.

Cardiac arrest occurs because there is a sudden change in the normal electrical activity of the heart.  There is a collection of abnormal heart rhythms, called arrhythmias, that can be responsible:  ventricular fibrillation (VF), ventricular tachycardia (VT), asystole, or pulseless electrical activity (PEA).  With each of these arrhythmias, the heart does not beat effectively and therefore does not pump any appreciable amount of blood.  The blood pressure falls to zero and a pulse can no longer be felt.

Without treatment, the victim of SCA has died.  The American Heart Association (AHA) suggests a conceptual framework called the “Chain of Survival” to outline the necessary links to increase the odds for survival:

1. Immediate recognition of cardiac arrest and activation of the emergency response system
2. Early CPR with emphasis on chest compressions
3. Rapid defibrillation, if needed
4. Effective advanced life support
5. Integrated post-cardiac arrest care.

Initial Treatment

If a victim of cardiac arrest is to become a survivor, there must be prompt and appropriate care at each step along the Chain of Survival.

It is important for bystanders to recognize the victim of cardiac arrest–unconscious, not breathing, no pulse.  The initial treatment is CPR.  In the United States, the AHA and American Red Cross offer classes in CPR.  For people who are not healthcare workers, the AHA teaches chest compression-only CPR, instructing the rescuer to do chest compressions centered over the breastbone, or sternum, at a rate of 100 compressions per minute.  The AHA teaches that the 100 compressions per minute rhythm can be maintained by doing the compressions to the beat of the 1983 Bee Gee’s hit song, “Staying Alive.”  Healthcare workers are taught how to do rescue breathing interspersed between sets of chest compressions, either in 1- or 2-rescuer scenarios.  If no nearby bystanders are trained in rescue breathing, then chest compressions alone are appropriate as an initial treatment.

While CPR is being performed, bystander rescuers need to notify the emergency medical system (EMS) to summon more advanced care for the victim.  In the United States, bystanders can call 9-1-1 to alert the appropriate authorities.  The telephone dispatcher will arrange for emergency medical technicians (EMTs) or paramedics to be dispatched to the scene.  The dispatcher can also remain on the telephone to help provide guidance to the bystanders who are tending to the victim.

If there is an AED nearby, somebody should fetch it.   These devices are often located in public spaces such as schools, shopping centers, fitness centers, etc.  They may also be on hand for special events.  The use of the AED is often taught in conjuction with the basic CPR course.  Even without instruction, the AED is designed to “talk you through” how to use the device in an emergency situation.  The AED is opened and the ON/OFF switch is turned ON.  An electronic voice will provide instructions to attach defibrillator pads to the victim’s chest in 2 locations.  The AED will analyze the victim’s heart rhythm and determine if a defibrillation shock would be helpful.  Such a shock is helpful if the rhythm is VF or VT, but is not helpful if the rhythm is asystole or PEA.  If needed, the AED will ask the rescuers to stand clear and it will deliver an appropriate shock, asking you to resume CPR if the shock does not terminate the arrhythmia.  If the shock is successful, the AED will instruct the rescuers to just monitor the patient.  If no shock is needed, the AED will instruct to continue CPR.  The AED will continue to monitor the heart rhythm and work through this same algorithm repeatedly at several-minute intervals until EMS personnel arrive on the scene.

I mentioned at the outset that the survival rate for out-of-hospital cardiac arrest was poor.  It’s encouraging, though, that in localities or situations where CPR training is widespread, the survival rate can be much higher.  Interestingly, in a recent review of SCA at long-distance running events, the survival rate was reported at 29% and was attributed in large part to prompt CPR provided by bystanders.

Advanced Life Support

The next phase of care might best be called advanced cardiac life support (ACLS).  This care is generally begun by EMTs or paramedics who were dispatched to the scene where a cardiac arrest victim is already receiving CPR by bystanders.  Information about the circumstances leading to the victim’s collapse should be passed along to the medical professionals who respond.  Sometimes there are very helpful details.

Away from the hospital setting, advanced life support is usually provided by EMTs or paramedics who have specialized training in this area.  In the hospital setting, many employees–nurses, physicians, and others–can take classes offered by the AHA to become certified in ACLS.  As a result, there may well be ACLS-trained bystanders when somebody suffers cardiac arrest.

Advanced life support will include both chest compressions as well as rescue breathing.  Supplemental oxygen will be provided and breaths will be administered initially using a bag-valve mask.  If the victim is not immediately revived, an oral or nasotracheal tube may be placed into the trachea (the windpipe) to continue to administer breaths to the victim.  Electrode patches will be placed on the victim’s skin and an EKG monitor will be used to determine the heart rhythm.  With CPR and rescue breathing in progress, the advanced cardiac life support phase of care is governed by algorithms that are specific to the exact type of heart rhythm.  There are 2 primary algorithms–1 for VF/pulseless VT and another for asystole/PEA.  In the hospital setting, we actually have hand-held cards with the algorithms to help guide a team of rescuers.

Included in the algorithms will be the use of medications, if needed, as well as defibrillation, if needed, depending upon the particular heart rhythm.  CPR, rescue breathing, and the resuscitation algorithm is pursued while the victim is transported to the hospital. 

Hospital Care

Efforts at resuscitation continue until either the victim’s normal heart rhythm is restored or the team of caregivers concludes that further efforts will be fruitless.  There is no absolute convention about how long resuscitative efforts should be continued, but there are certainly examples of patients who are successfully resuscitated after prolonged CPR.  As just one example, I’ve written here at the blog about the soccer player, Fabrice Muamba, who was revived after 78 minutes of CPR.

If a victim’s heart rhythm is restored, then there are 2 major immediate goals:  1) prevent a recurrence of the near-fatal arrhythmia and 2) protect the body’s organs, as much as possible, from the effects of the disturbed circulation while the resuscitation efforts were being made.  Efforts at the first goal will depend upon the known, or suspected, cause.  Evaluation and monitoring is conducted to be certain that the blood oxygen levels and blood electrolyte levels are appropriate.  Often, anti-arrhythmic medications will be used for this purpose.  The second goal is also very important.  We know that, even with CPR that is successful and results in revival of the patient, there can be insufficient blood supply to the body’s organs for a period of time.  The brain is particularly susceptible to injury because of inadequate blood floow or oxygen, even for relatively short periods of time.  One technique that has gained popularity in recent years is the use of induced coma combined with hypothermia (lowering the body temperature by several degrees) to reduce the metabolic demands on the brain for a period of about 48 hours.  This allows potentially better recovery of the brain.  We know that such an approach may improve the neurologic outcomes for at least some patients who have suffered cardiac arrest.  This technique appears to have been used in the case of Laurent Vidal.

The last issue is to determine what caused the cardiac arrest.  There’s actually a fairly long list of possible causes.  In the sports setting, for younger athletes the most likely heart-related causes are hypertrophic cardiomyopathy (HCM)–an inherited disorder of the heart muscle; a coronary artery anomaly–an artery that developed abnormally during development; an inherited cardiac ion channel abnormality (eg, long QT syndrome); or arrhythmogenic right ventricular cardiomyopathy (ARVC)–another inherited disorder of the heart muscle.  But sometimes cardiac arrest may be have a non-cardiac cause like pulmonary embolism or stroke.  Even a sharp blow to the chest can produce cardiac arrest, a situation called “comotio cordis.”  The evaluation of survivors of cardiac arrest is done in a systematic way to sort through the various possibilities.  It’s usually possible to determine a cause, but there’s a small chance that no cause is found.

Related Posts:

1.  Sudden cardiac arrest in NCAA student athletes

2.  Dana Vollmer and ICD

3.  Athletes, Sudden Death, and CPR