Matters of the Heart

Cardiac Nursing

This is a post series. If you would like to quickly access the other posts in this series, there is a menu at the bottom of this post where all the other posts are linked.

Cardiac pathophysiology, medications, and nursing interventions.

The heart is vital to understand because it is the organ that circulates blood around the body. In a way, it is the lifeline to all other organs, meaning they will not survive without the heart working properly.

Your heart creates its own electricity that contracts the myocytes (heart cells) creating a squeeze inside its chambers forcing blood to get on its way through the body. This ability to create electrical impulses is called automaticity. There are 3 major areas of the heart that have the ability to generate their own electrical impulses: The sinoatrial node (SA node), the Atrioventricular node (AV node) and the Bundle of His/Purkinje fibers. This trio is called the natural pacemakers of the heart.

The SA node fires at a rate of 60-100 beats per minute. This is what we consider a normal heart rate. The SA node is the main boss of the heart, like the manager of the heart. It oversees the daily work of the heart.

If the SA node isn’t working then the AV node takes over, it is naturally a pacemaker at 40-60 beats per minute. The AV node is like the team leaders, they get their orders from the SA node, but if the SA node goes to a conference the team still carries on with orders from the AV node.

This brings us to the worker bee’s of the heart: the Bundle of His and the Purkinje Fibers. They take their orders from the AV node, who takes their orders from the SA node. But if the managers and team leads are gone, the show must go on, so the Bundle of His and Purkinje Fibers will carry the team at 30-40 beats per minute. This is of course not ideal but something is better than nothing (AKA flat line).


As with all teams, there are influencing factors. The heart beats naturally on its own but what if the needs of the body change and the heart must change its speed to meet the demands of the body? That is where the Vagus Nerve, Cranial Nerve X, comes into play.

The cardiac muscle is innervated via the vagus nerve which is controlled by the autonomic nervous system. Remember fight or flight versus rest and digest? Well, these are the two ‘modes’ of the autonomic nervous system.

Let’s break this down: The autonomic system either increases (sympathetic) or decreases (parasympathetic) your heart rate based on your body’s needs. If you are being chased by a bear, your sympathetic nervous system autonomically tells your heart to speed the fudge up. This circulates the blood more quickly so your body can do super awesome things like run away from a bear. If you are binge-watching Netflix, your parasympathetic system takes your heart rate down to a less intense rate because you do not need to be able to lift a car off your baby while starting the next episode of Shameless.

These electrical impulses create a series of actions throughout the heart. A 12-lead ECG can read the electrical activity and give us an idea of which actions are doing their job and which ones are not. If all the actions are performing their jobs consistently than we call this normal sinus rhythm (or NSR). There are, of course, many variations to the results of a 12-lead and each result has a meaning.

As a nurse, it is your job to care for your patients’ cardiovascular system, making it vital to know how to read an ECG, recognize and treat cardiac problems, and know the physiology of cardiac conditions.


That is why Patrick from PatMacRN and Susan from BossRN have come together to create this resource for all of you, for free. Please enjoy!

Disclaimer: This material should be used to supplement your understanding of the cardiovascular system. Any use of the information given in this post series is at your own risk and should be verified prior to making it a part of your nursing practice. There may be affiliate links associated with some products but we promise that we will never recommend anything that we don’t use ourselves.

Cardiac Assessment for Nurses

When you perform a cardiac assessment, you will be assessing more than just the heart. For example, you will look at a patient’s skin to assess their perfusion, or their breathing because having a myocardial infarction can sometimes make a patient short of breath. You will also listen to heart sounds and check pulses so it is important to remember that you perform a broad assessment.

Here is an example of me doing a cardiac assessment on a patient:

I will walk up to the person and ask them a question that is open-ended to assess their ability to hold a conversation without becoming winded. While getting a visual on their breathing rate, effort, and rhythm, I will place my fingers on the radial pulse to assess if their pulses are strong, weak, thready, and regular/irregular. This also gives me information about the patient’s skin such as temperature, moisture, and turgor.

I then use my stethoscope to listen to heart sounds. I am listening for S1 and S2 but also trying to eliminate pericardial friction rub or murmurs. While listening to heart sounds, I will count the heart rate. I then chart my cardiac assessment, making sure I note relevant vital signs (Heart rate, blood pressure, respirations), my objective data and subjective data.

Questions to make sure you ask include, “Are you having any chest pain?” or “any shortness of breath? How about with exertion?” as well as “are you experiencing any dizziness?”

Any abnormal finding should warrant an ECG and the results of that ECG should be included with the charted assessment.

Wanna know what stethoscope to use? Patrick and Susan both use Littmann stethoscopes. Check out which stethoscopes we use:

How to listen to heart sounds

The good ole ‘Lub Dub’ assessment can be daunting.

I remember in nursing school, listening to a patient’s heart sounds and thinking, ”The heart is there and I can hear it making noises.” I even remember a patient having a murmur and my clinical instructor having us all come listen. I listened and thought, “…The heart is still making noises.”



So what do these noises mean?

Well at the basic level, Lub is S1 and Dub is S2. S1 literally means first heart sound, or sound 1. S2 means second sound. If all things are going as planned this is all you should be hearing when listening to heart sounds.

S1: Lub is the sound of the Mitral and Tricuspid valves closing. This is the beginning of the systolic blood pressure, which ends as soon as you hear S2. S1 can be heard the loudest over the apex of the heart.

S2: Dub is the closure of the aortic and pulmonic valves and the beginning of diastole. During the pause between S2 and S1 is when the ventricles are filling.

S3: Also called a ventricular gallop, has been said to sound like “ken-tuc-ky” Ken being S1, Tuc being S2, and ky being S3. If you hear this sound and the patient is over 30 years of age, it means that the ventricles are resisting filling during diastole and can be a sign of heart failure or even ischemia.

S4: Also called an atrial gallop, has been said to sound like “Ten-nes-see” Ten being S4, nes being S1 and see being S2. It has been noted to be heard prior to a myocardial infarction where the ECG shows normal sinus rhythm. A fourth heart sound can also indicate hypertrophic cardiomyopathy, aortic stenosis or systemic hypertension.

In my experience, S3 and S4 are incredibly difficult to hear unless you are in a perfectly quiet environment and you have lots of experience hearing these sounds. Clinically speaking, we have many diagnostic tests that can accomplish similar outcomes. It is a good skill to master, but until you become a pro at hearing heart sounds, know that you can use other diagnostic testing to come to the same clinical conclusion. If you are going to be specializing in cardiac nursing you may want to invest in a robust stethoscope like the Littmann 3100 Electronic Stethoscope.

Murmurs are swooshing or a swishing sound that can mean a valve isn’t closing all the way or that there is a hole in the heart. Using the Mnemonic APE to MAN, listen to the heart sounds in each position. Many heart murmurs do not cause any issues and do not need any treatment. Some heart murmurs will need treatment. For children, it is more concerning to hear a heart murmur. For adults, there is a bigger chance it is what is called an innocent murmur (meaning not really concerning).


Cardiac enzymes and lab work

Cardiac Enzymes

Blood work that may be used to help further monitor or diagnose a cardiac condition may include: Troponins (Trops), Myoglobin, Creatinine Kinase (CK), Brain Natriuretic Peptide (BNP), D-Dimer, PT/PTT/INR (Coags) and Complete Metabolic Panel (CMP). Test result ranges as well as collection techniques and times, will vary per facility so check your facilities protocols.

Troponins: This cardiac enzyme is a protein found in both cardiac and skeletal muscle. There are 3 different types of troponins that can be tested for, but Troponin I is more specific to the heart. When the heart is stressed out it will release this enzyme about 3-4 hours after the initial ‘insult’ or ‘stressor’ to the heart. Generally, most facilities will get an initial troponin and then re-check another troponin 2 hours later. If a patient has a normal ECG but a positive Troponin, they will likely be treated for a non-ST Elevated Myocardial Infarction (NON-STEMI)

Myoglobin: This protein is found in muscle and binds oxygen to the muscle cells. When damage occurs to the muscle, myoglobin will be released into the bloodstream. Myoglobin can be tested along with troponins.

Creatinine Kinase: This protein, found in both cardiac and skeletal muscle, is released when there is any kind of damage to muscles. There are 3 types of CK that can be tested: CK-MB, CK-BB, CK-MM. CK-MB is specific to cardiac muscle.

Brain Natriuretic Peptide: BNP is made in the heart and when the chambers of the heart are stretched too much, BNP is released. The more the heart is stretched, the more BNP is released. BNP is mostly used to measure heart failure, thus the higher the BNP, the more the heart is in failure.

D-Dimer: This lab test detects protein released from a blood clot when it is dissolving. A blood clot could cause a myocardial infarction if lodged in the heart. It might also indicate a pulmonary embolism (PE) or deep vein thrombosis (DVT). This test is less often used but can help detect an MI in the early stages.

PT/PTT/INR: If a patient has an arrhythmia, such as atrial fibrillation, or they are at a high risk for developing blood clots, they may be on a blood thinner such as Coumadin or aspirin. In these patients, it is important to monitor the coagulation lab work. The therapeutic range for these patients depends on the specific patient and their plan of care.

Complete Metabolic Panel: This lab is important to monitor and check because the myocytes are able to contract using channels that move electrolytes. When the electrolytes are imbalanced, the heart can have an arrhythmia.

If lab work is confusing to you, I recommend using Lab Values for Nurses By NRSNG. (I recommend this because I helped write it!)

Cardiac Manifestations

There is literally a multitude of physical manifestations that we, as nurses, may come across in our physical assessment of our patients. Thankfully, if you assess your ABC’s (or CABs lol) you should be able to pick up on many these manifestations.



For the sake of alphabetism, let’s stick with the ABC framework to group some of the primary cardiovascular clinical and physical manifestations that come up in the care of patients experiencing cardiovascular complications.

A: Airway – A compromised airway can lead to a nurses nightmare, in regards to cardiovascular issues. This is because the respiratory is linked in an eternal love-hate relationship with the cardiovascular system. Lol! The following are some physical manifestations that can result in cardiovascular compromise or issues.

  • Deviated trachea – Normally, the trachea should be midline. However, when there is a pressure balance lower in the respiratory tract (the lungs), the trachea will deviate to the right or the left. Remember, if you see this manifestation, something is going down or is about to go down. The usual culprit is a pneumothorax. The trachea always deviates to the side with less pressure. So if the trachea deviates to the left, there is likely a pneumothorax in the right lung.
  • Tachycardia – Tachycardia can results from the poor oxygenation as related to a compromised airway or from hyperventilation related to the panic feeling patients can get when they are conscious and their airway is compromised.
  • Cyanosis – A bluish (or some time gray) tint to the skin of the affected area, due to a lack of oxygen delivery. This can present in a focused area, such as the lips or the nails beds. It can also be present in the extremities in something known as acrocyanosis.

B: Breathing –

  • Tachypnea – Rapid breathing (Tachypnea) can increase feelings of panic and also accelerate respiratory and cardiovascular compromise. When patients are tachypneic they are not able to adequately exchange O2 and CO2. Thus tachypnea can cause or worsen tachycardia. Supplemental O2 and keeping the patient calm are critical. Be careful not to over oxygenate patients though, and be mindful of oxygenation protocol for those with COPD, Emphysema, or other similar respiratory issues.
  • Tachycardia – See above
  • Cyanosis – See below

C: Circulation – Circulation is the most obvious wildcard in the ABC deck. Circulatory compromise has many manifestations. Common manifestations are listed below.

  • Tachypnea and Tachycardia – See above.
  • Cyanosis – See above
  • Edema- Poor circulation can often lead to blood and other bodily fluid becoming stagnant and pooling in various areas of the body. These areas include, but are not limited to the lower extremities (Legs, ankles, and feet), Upper extremities, lungs, trachea, the face, and the heart itself.
  • Jugular Vein Distention (JVD) 
  • Distant Heart sounds with Auscultation – Common in cardiac tamponade, when fluid excess fluid is surrounding and restricting the hearts movement. It should be noted that heart sound can also sound distant when a patient has more adipose (fat) tissue for the clinician’s stethoscope to penetrate.
  • PAC/PVC, or skipped heartbeats – These are often “electrical” or conduction problems that can lead to circulatory problems if not addressed or resolved.

How do you read an EKG



So 12 lead ECGs can be daunting. Learning to read them takes time, practice and repetition. But I recommend starting with the basics.

Familiarise yourself with the paper that an ECG is printed on. An ECG is printed on a graph paper that has tiny little boxes on it.



The width of a small box is 0.04 seconds

5 small boxes make 1 large box. The large box is 0.2 seconds.

5 large boxes make 1 second.

A common length to read an ECG strip is 6 seconds, or 30 large boxes, and is called the ‘six-second strip.’

The height is 0.5 millivolts (mV). When you are just starting to learn ECGs, memorizing the actual height measurement is not all that critical. It is important to use the height to discern the isoelectric line and any variance from the isoelectric line. The isoelectric line is the line that the ECG is mostly on except during those moments where the line is deflected up or downward. In other words, if someone was flatlining, they would be completely flatlined on the isoelectric line.



The next thing you need to do is practice identifying all the waves on a normal sinus EKG.

Normal Sinus Rhythm


You will need to identify if the wave is present or not when interpreting an ECG. If a wave is not present, it will give you insight into the rhythm. For example, atrial fibrillation will be missing the p wave. Once you get skilled at identifying all the waves, you will need to answer a few questions for different parts of the waves.

P wave:

  1. Is there a P wave?
  2. Is the P wave happening regularly?
  3. Does every P wave have a QRS complex following it?
  4. Do all the P waves look the same?

PR interval:

  1. Is the PR interval between 0.12-0.2 seconds?
  2. Does the interval time stay the same or vary?

QRS complex:

  1. Is the QRS interval between 0.08-0.1 seconds?
  2. Are they the same height?
  3. Is the R wave to R wave consistent?  

T wave:

  1. Is there a T wave?
  2. Does it follow a QRS complex?
  3. How tall is the wave?

QT interval

  1. Is the interval less than 0.44 seconds?

ST segment

  1. Is the line flat and in line with the isoelectric line?

Having all the details of how to read a normal sinus EKG out of the way, when an ECG prints out of the ECG machine, you will notice that there is a small narrative on the top of the ECG… Telling you what rhythm is being shown… So why do I need to know how to read an ECG? Because you are responsible for being able to catch when the machine is improperly reading an ECG. Sometimes it says that it is a totally fine ECG when it’s not and vice versa.

Reading Electrocardiograms

Patrick and Susan both use ECG interpretation made incredibly easy the pocket guide

What are Atrial Arrhythmias

Abnormal rhythms in the atria (the 2 upper chambers of the heart), can be more common in everyday life, in some instances. Atrial arrhythmias can sometimes be considered less of an immediate threat, but that can change quickly.

Atrial arrhythmias can vary in how serious they are., for example, Premature Atrial Contractions (PACs) is when the atrium contract prematurely, typically after an initial pulse from the sinus node and before the contraction of the ventricles. PACs can occur for a myriad of reasons, such as drinking a caffeinated beverage, increased stress or even due to the consumption of excessive alcohol and tobacco products.

Atrial flutter (A-flutter) and Atrial fibrillation (A-fib) are the 2 more serious atrial arrhythmias. A-flutter and A-fib can sometimes be confusing to differentiate, and they are treated in similar ways. The biggest difference is regularity and pattern. A-flutter is typically a steady rhythm, with a consistent pattern of atrial flutters to ventricular contractions and discharge (QRS complex). Simply put, A-fib tends to be inconsistent in nature and the heart rate varies quite regularly. It is not uncommon for those experiencing A-flutter to progress to A-fib.

Junctional rhythms and accelerated atrial rhythms, like SVT, are Rhythms than can cause serious issues for your patients. Junctional rhythms concerns impulses that originate at the AV node, instead of the SA node, thus no P-wave is visible most times or an inverted p-wave may be visible.

Finally, Supraventricular Tachycardia (SVT) is a Rhythm that can be serious if it persists for a significant amount of time, untreated, allow it’s not uncommon for some to have short bursts of this. The “supra” in this long and fancy word indicated that tachycardia exists above the ventricles. Many times, people who are experiencing SVT feel similar to A-fib patients who are experiencing accelerated rates, especially with a patient experiencing A-fib with Rapid Ventricular Response (A-fib RVR).

What are Ventricular Arrhythmias

The most dangerous type of arrhythmia are those originating from the ventricles. When the ventricles are not pumping appropriately, blood flow becomes disrupted. The body can only maintain Ventricular Fibrillation, or V-Fib, for 6 minutes before cardiovascular collapse and cardiac arrest occurs.

Some people have Premature Ventricular Contractions, or PVCs, this is a relatively common heartbeat that originates from the Purkinje fibers. It will not have a P wave before the beat because it got its message to beat from the Purkinje fibers and not the SA or AV node. It is generally considered not concerning unless a run of PVCs are strung together.

When 3 or more PVCs in a row occur at a rate of 100 beats per minute it is considered ventricular tachycardia, or V-Tach, which left untreated can turn into ventricular fibrillation. As discussed above, V-Fib is concerning.

Do you think this is V-Tach or V-Fib?


Vascular cardiac problems you should know

The heart itself is like an engine, and what would an engine be if it didn’t have pipes and tubing to put gas to good use. It is the same with the heart. Just as the piping and tubing may have blockages and issues in our cars, our heart may also experience issues with blockages and other issues. The most significant and common arterial and vascular issues that can arise in nursing practice are as follows:

  • Blockages:
  • Arterial or vascular flow and pooling issues:
  • Arterial and vascular wall deficiencies:
    • Aortic Aneurysm

How do medications affect the heart

Cardiac Medication

Let’s just say that there exist a mind-boggling amount of medications that affect the cardiovascular system. Rather than trying to address each of these medications, individually, we will be discussing medications in the structure of their classification and types. Common medication types that you will come across in the care of cardiovascular patients are Beta-blocker (BBs), Angiotensin-converting enzyme (ACE) inhibitors, Angiotensin receptor blockers (ARBs), and Calcium Channel Blockers (CCBs). The medications all work in different ways, to help the heart function properly, both “electrically and “Mechanically”.

Thanks for stopping by. This is a blog post series that will be covering all of the topics that have been touched on in this post! Enjoy and leave a comment if you have any questions or topics you’d like covered!


Additional sources:


Written by:

Patrick McMurray of PatMacRN is a full-time critical and intermediate care nurse at Level I academic trauma center. In his spare time, Patrick enjoys reading, traveling, and improving his French language skills.

Susan DuPont of BossRN is a full-time bedside emergency room nurse in a level one trauma center. In her spare time, she likes to fish, hunt, and travel.

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