Reversible Causes of Cardiac Arrest: Beyond the H’s and T’s

When learning about advanced cardiac life support (ACLS) in medical school, students learn about a mnemonic called the H’s and T’s. These are associated with the steps they need to follow during a cardiac arrest event. However, they don’t exactly explain the reversible causes of a cardiac arrest from a patient standpoint.

This article will briefly cover the 5 H’s and T’s so that the average Joe can become familiar with them- as they are related to what causes a cardiac arrest to happen. But most importantly, while you cannot reverse a cardiac arrest once it has occurred, you can take steps to prevent cardiac arrest from happening again by focusing on the causes. So, I’ll go over some important things you can do in your everyday life to help reverse these causes of cardiac arrest. And finally, I’ll go over what to do if one occurs. Ready? Here we go!

>>Click here to skip to the FREE downloadable Cardiac Emergency Response Plan.<<

What is a Cardiac Arrest?

A cardiac arrest is when your heart suddenly stops pumping. A scary fact is that even those without a diagnosis of heart disease can suffer a cardiac arrest. This may be for several reasons, which we’ll discuss below.

When the heart stops pumping, blood cannot get to any of your organs, including your brain. So it is absolutely critical that the heart start beating again ASAP.

According to the National Heart, Lung, and Blood Institute, about 300,000 to 450,000 deaths each year in the U.S. are attributed to cardiac arrests. And nearly half of cardiac arrests happen to those who didn’t even know they had a heart issue (1).

The Shocking Truth: Nine out of ten people who have a cardiac arrest outside of a hospital die- often within minutes.

Cardiac Arrest Versus Heart Attack

While a cardiac arrest and a heart attack are both very serious events and can lead to death if not treated quickly, there are some major differences between the two.

In short, the major difference between a cardiac arrest and a heart attack is HOW they develop. A cardiac arrest is an electrical issue whereas a heart attack is a blood supply issue.

It is very common to mistake the two because they are both fatal and very serious heart events. However, it may be easier to remember if you think of the definition of arrest, which means “the act of stopping” or “the condition of being stopped or inactive”, according to the Merriam-Webster Dictionary (2). A heart attack on the other hand is an attack on the heart brought on by a blockage or blood clot that damages part of the heart. Blockages are usually the result of a condition called coronary artery disease (CAD) which is an extremely common heart disease (1).

For more information on the difference between heart attack and cardiac arrest, you can read the article, “Heart Attack and Sudden Cardiac Arrest Differences” from the American Heart Association webpage.

Common Causes of Cardiac Arrest

While I mentioned that CAD is the most common cause of heart attack, it is also a cause of cardiac arrest. In addition, a heart attack may increase your risk of having a cardiac arrest and is one common cause.

When it comes to a cardiac arrest there are specific medical conditions that can lead to an arrest, but also behavior and activity triggers that can bring on this deadly event.

EKG report with black stethoscope lying on top of EKG paper.

Medical Conditions Leading to Cardiac Arrest

The most common medical conditions that cause cardiac arrest are irregular heartbeats, also called arrhythmias (1,2). In fact, there are two specific types of arrhythmias that contribute to cardiac arrest. These are ventricular fibrillation and long Q-T syndrome (2,3,4). These electrical issues cause your heart’s upper and lower chambers to not work together.

There are other medical conditions that may contribute to cardiac arrest as well. They include:

  • Coronary heart disease
  • Cardiomyopathy
  • Heart valve disease
  • Congenital heart defects

Behavior and Activity Triggers Leading to Cardiac Arrest

There are everyday “triggers” that can also cause a cardiac arrest. Many of these activities are controllable and more importantly reversible causes of cardiac arrest. These include:

  • Physical bodily stress, including exercise and competitive sports
  • Heavy alcohol intake or binge drinking
  • Excessive caffeine intake
  • Recent substance abuse- including cocaine, marijuana, and amphetamines
  • Severe emotional stress occurring within the past month
  • Contracting the influenza virus within the past month

While you may not be able to 100% protect against getting the flu, you can control other behavioral factors in this category. For example you can avoid alcohol and drug use. Or you can limit caffeine intake by drinking only 1-2 cups of coffee daily (5).

It’s also important to note that suddenly increasing physical exercise when you are sedentary OR suddenly increasing caffeine intake can trigger a cardiac arrest. So to those who take caffeine pills, powders, or energy drinks- be mindful of how much caffeine you’re consuming!

Factors That Increase Cardiac Arrest Risk

Some individuals may unfortunately have a higher risk of cardiac arrest than others. These risk factors are out of your control and are based on age, sex, race and ethnicity, family history, and whether or not you have other heart or medical conditions.

Age– your risk will increase as you age. For those under 30 years old, causes are most likely congenital, from heart structural abnormalities, or from substance abuse.

Gender– older men are more likely than women to have a cardiac arrest, however incidence in women tends to increase after menopause.

Race and Ethnicity– the African American population are at higher risk than others for heart disease, high blood pressure, and diabetes. This leads to a higher risk for cardiac arrest as well. African American women have a higher risk than African American men do. And Hispanic and Asian populations are at lower risk than Caucasians.

Family History– having a family history of heart disease or cardiac arrest increases your likelihood of a cardiac arrest.

Other Heart and/or Medical Conditions– if you have any of the medical conditions listed above or have nutrient deficiencies you may be at higher risk. For example, having low potassium or magnesium levels may affect heart rhythms, leading to cardiac arrest (6).

While having any or all of these risk factors is not a guarantee that you will suffer a cardiac arrest, they are important things to consider. You can take control of your life and your health outcome by taking preventative measures.

See the section on “Preventative Measures for Cardiac Patients” below to see what you can do right now.

The H’s and T’s of Cardiac Arrest

When medical students go through advanced cardiac life support (ACLS) training, they learn about the 5 H’s and 5 T’s.

This is a mnemonic to help remember what conditions to assess during treatment of a cardiac arrest. One or more of these conditions could be what caused the cardiac arrest to occur. Let’s briefly go through the H’s and T’s of ACLS.

H Causes of Reversible Cardiac Arrest

1. HypovolemiaHypovolemia is the loss of fluid in your body which may have caused the arrest. Cardiac arrest patients will likely receive IV fluids or blood to replace what was lost.
2. HypoxiaHypoxia is a medical term meaning lack of oxygen in your body tissue. Medical staff will make sure the airway is open and oxygen is being received. This may require being put on ventilator support.
3. Hydrogen ion (acidosis)Cardiac arrest patients may be in respiratory acidosis, meaning your body isn’t properly removing the carbon dioxide it’s producing. Patients may be supplemented with sodium bicarbonate to balance out the acidosis.
4. Hyper-/hypokalemiaHyperkalemia is when potassium level is too high while hypokalemia is when it is too low. An imbalance of potassium may be a cause of cardiac arrest. Staff will provide care to get potassium level back to a normal range.
5. HypothermiaHypothermia is when your body temperature is too low. Medical staff will provide care to quickly raise body temp to a normal level.

T Causes of Reversible Cardiac Arrest

1. ToxinsThis involves any toxic agents as a cause of cardiac arrest. It could include medications such as digoxin, beta-blockers, and calcium channel blockers or street drugs, like cocaine. Poison control may be called.
2. Tamponade (cardiac)A cardiac tamponade occurs when fluid builds up in the pericardium (the sac surrounding the heart). Emergency staff will need to remove the fluid which is putting pressure on the heart with a procedure called a pericardiocentesis.
3. Tension pneumothoraxTension pneumothorax is when air enters into the pleural cavity and cannot escape. This can lead to tension build up and cardiac arrest. Staff will need to remove the air to decrease pressure.
4. Thrombosis (heart)Coronary (heart) thrombosis is a blockage of blood flow within an artery caused by a blood clot.
5. Thrombosis (lung)Pulmonary (lung) thrombosis is a blockage of the main artery of the lung. This can lead to respiratory collapse and cardiac arrest. If this is the cause, a surgical procedure called thrombectomy may be performed.

Survival Rate After Cardiac Arrest

The survival rate after a cardiac arrest depends largely on the setting. Survival is much more likely if a cardiac arrest happens in a hospital setting versus outside of a hospital setting where immediate help is not available.

Two factors that will greatly increase chances of survival are initiation of cardiopulmonary resuscitation (CPR) and use of an automated external defibrillator (AED).

These measures are crucial for reversing a cardiac arrest, or at least decreasing neurological damage (7).

It is estimated that whether these out of hospital cardiac arrests occur at a residence, a public setting, or at a nursing home, the survival rate for adults is only around 10%. Additionally, factors such as geographical location and ethnicity show differences in the chance of survival (8).

Current statistics show that survival rates are higher among those living in the Midwest and South compared to those in the Southeast. And overall survival and return of brain function is more likely in White populations compared to Hispanic, African American, and Asian populations (8).

Emergency sign outside of a hospital

This difference is mainly due to delays in the onset of medical care. Remember that time is of the essence when it comes to a major cardiac event. Swift action with CPR and an AED device will always increase survival rate and the return of neurological function.

Precautionary Measures for Cardiac Arrest Patients

There isn’t much you can do when you are the one having an active cardiac arrest. You will likely not be able to call for help. And you cannot perform life-saving techniques on yourself.

However, for those with a history of heart disease, you may have already thought about what you would do in an emergency situation, such as a cardiac arrest.

The following sections will cover some actionable steps you can implement now to get help if a cardiac event happens to you.

Post Emergency Numbers

Posting important emergency phone numbers somewhere within eyesight is beneficial. One of the most common places people tend to post emergency numbers is on their refrigerator. However, if you are not at home, you can keep a list in your wallet, purse, or even keep it on a medical alert bracelet or necklace.

Some of these emergency numbers may include an emergency contact person (spouse, other relative, caregiver, etc.), local police, fire station, Poison Control, and of course 9-1-1.

During a cardiac arrest, having these numbers available to those around you can help improve your chances of survival. The quicker you get help, the better your chances.

Keep an Emergency Alert Device

Many individuals may opt to keep an emergency alert device on them at all times. These help to notify emergency personnel at the push of a button.

You may have heard of a product called Life Alert. Yes, I’m talking about those commercials on television with the older woman yelling, “Help! I’ve fallen and I can’t get up!” Well, this is one example of an emergency alert device. It could potentially save your life and has multiple uses such as in the event of a fall, a heart attack or other cardiac event, or personal protection.

There are many options to choose from when it comes to these devices. They come in different forms such as watches or devices the size of a garage opener. Some even have built-in GPS and free trial periods. Here are a few great options available:

Elderly man given a kiss on temple to elderly woman outdoors on overcast day.

Make Sure You’re Never Alone

While it may not be feasible to always be in the presence of others, it’s important to not be alone too often. If you are at high risk of a cardiac event, you want to be around people who can help or who can call 9-1-1 for you.

Additionally, this backs up the need for an emergency alert system such as a device previously discussed. If you live alone, having a device such as the ones discussed may be the best option for immediate help.

Some families even adjust living arrangements, either temporarily or permanently, so that loved ones are not by themselves.

Preventative Measures for Cardiac Patients

Now that you know some reversible causes of cardiac arrest, let’s go over some diet and lifestyle recommendations to prevent and reverse heart disease.

Dietary Interventions

Following a healthy diet can prolong health and longevity and decrease your chances of developing chronic disease. A cardioprotective dietary pattern, including the Mediterranean diet and DASH diet, is proven to decrease the risk of cardiovascular disease.

These two specific diets focus on higher intake of fruits, vegetables, whole grains, beans, lean protein sources, such as fish and seafood, low fat dairy, and nuts and seeds.

They also encourage limiting intake of saturated fats, including red meats, yogurt, cheeses and other saturated fats. Sweets and added sugars are also kept to a minimum.

You can learn more about the Mediterranean diet by reading Mediterranean Diet For Beginners (Get Started Today!). Even keeping healthy Mediterranean pantry staples on-hand can help you eat a more healthful diet.

To receive a free heart healthy grocery shopping list, click the image below to sign up to my email list:

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Or receive a downloadable copy of the Top 25 Heart Healthy Foods List:

Top 25 Heart Healthy Foods

Lifestyle Interventions

How you live life on a daily basis can have a major impact on your health.

In order to reverse and prevent causes of cardiac arrest, recommendations include avoiding harmful behaviors such as:

  • Smoking
  • Alcohol use
  • Use of illegal street drugs or misuse of legal prescribed drugs
  • Living a mostly sedentary lifestyle

Instead, come up with a lifestyle plan. And be consistent with it.

A heart-healthy lifestyle should include making sure you are eating healthy, nutrient-rich foods, getting adequate amounts of sleep (7-9 hours/night), engaging in at least 150 minutes of physical activity per week, managing stress levels, and avoiding the harmful lifestyle behaviors listed above.

Related Article: 5 Things You Can Do to Support Heart Health NOW!

Developing a Cardiac Emergency Response Plan

As another precautionary measure, you may want to start thinking about the best cardiac emergency response plan for you or your loved one.

A cardiac emergency response plan (CERP) is a written document of the steps to take to reduce death from cardiac arrest. Many facilities, including schools are trained to implement a CERP in order to reduce chaos and help save lives during a cardiac event. Likewise, it is also essential information for YOU and your loved ones.

Writing A Cardiac Emergency Response Plan

Start by getting a sheet of paper or type the following steps into a Word document on the computer and print off.

  1. Who will be a part of your Cardiac Emergency Response Plan team? Make sure to have at least one person on your list that is certified in how to provide CPR and use an AED device. List all team members.
  2. Write down the specific steps each member will take during a cardiac arrest. You may even want to do a mock cardiac emergency drill!

Make sure to review and update your plan and steps at least annually. Give it to all team members and post it somewhere it can be easily seen.

You can also download this free cardiac emergency response plan PDF I created for you:

Pictured: AED device which may be located in highly visible areas in malls, theaters, and other public buildings

Where To Find a CPR/AED Course

I highly recommend CPR and AED classes. In fact I think everyone should take a CPR, first aid, and AED class at some point in their lives. These classes are very valuable and can help save lives in emergency situations.

If you do take a CPR/AED course, you must take a recertification class every 2 years. But keep in mind that being certified is not NECESSARY in a cardiac emergency. Even children can learn to do chest compressions. Certification is just highly recommended to make sure you know exactly what to do. Some classes are taught in-person while others are conveniently available online.

Here are some links to help find a course in your area:


So, I hope you feel more knowledgeable on the difference between a cardiac arrest and heart attack and the reversible causes of cardiac arrest. You should feel more confident in how to prevent a cardiac arrest from happening to you. Learning the H’s and T’s of cardiac arrest can help you pinpoint ways to prevent or reverse cardiac arrest.

A cardiac arrest can happen for multiple reasons. For those without a history of heart issues, you may feel there’s nothing you can do to prevent it. But the truth is, a heart-healthy diet and lifestyle can potentially help you.

A strong heart is a healthy heart. Continue to focus on all areas of health including physical activity, avoiding unhealthy habits like smoking and alcohol use, managing risk factors, and of course following a heart healthy diet which includes whole grains, fruits, vegetables, low fat dairy, lean protein sources, and limited added sugars and saturated fat. By following these tips, you can decrease your chances of ever having to use your cardiac emergency response plan.

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