P Wave:  We can associate the P wave of an EKG with the contraction of the atria and the relaxation of the ventricles (diastole - dub).

QRS Wave: The QRS wave is sometimes called the QRS complex, and it represents the depolarization of the ventricles. This quickly leads to the contraction of the ventricles and ejection of blood out of the heart and into the large arteries exiting the heart (systole - lub).

T Wave: Recovery of the ventricles.

The Heart and Its Nodes

Electrocardiogram (EKG)

Normal Sinus Rhythm

This is the normal rhythm of the heart. The electrical impulse originates within the SA node and travels through the atria to the AV node. After a brief delay, the impulse travels down the bundle branches, though the Purkinje fibers to the ventricles. What you want your patient ECG to look like.

Sinus Bradycardia

Sinus bradycardia is a sinus rhythm with a rate of 40-60 bpm. This in a healthy athletic person may be 'normal', but other causes may be due to increased vagal tone from drug abuse, hypoglycemia and brain injury with increase intracranial pressure (ICP) as examples. Usually benign and often caused by patients on beta blockers.

Sinus Tachycardia

Sinus tachycardia is a normal sinus rhythm but with a heart rate over 100 bpm. It is a normal response to exercise, excitement and some illnesses. Not usually a surprise if it is triggered in response to regulatory changes e.g. shock. But if there is no apparent trigger then medications may be required to suppress the rhythm. The impulse generating the heart beats are normal, but they are occurring at a faster pace than normal. Seen during exercise.

Sinus Arrhythmia

Sinus arrhythmia looks normal except for slight irregularities. Is a normal physiological phenomenon, most commonly seen in young, healthy people. 

Ventricular Fibrillation (VF)

Disorganized electrical signals cause the ventricles to quiver instead of contract in a rhythmic fashion. A patient will be unconscious as blood is not pumped to the brain. Immediate treatment by defibrillation is indicated. This condition may occur during or after a heart attack.

This patient needs to be defibrillated!! QUICKLY

Asystole

A state of no cardiac electrical activity, as such no contractions of the myocardium and no cardiac output or blood flow are present.

Carry out CPR!!

Match the following EKGs with the correct rhythm name. Sinus Bradycardia Ventricular Fibrillation (VF) Sinus Arrhythmia Sinus Tachycardia Asystole Normal Sinus Rhythm 1. _______________________________

2. ______________________________

3. ______________________________

4. ______________________________

5. ________________________________

6. ________________________________

What is Vagal Tone?

Vagal tone is the degree of activity occurring within the parasympathetic nervous system, resulting in changes to the heart rate and other key functions.

The vagus nerve, among many other things, inhibits the heartbeat to keep the organ beating within a safe range.

When the vagal tone increases or decreases, a patient will experience changes in heart rate, and these can sometimes become dangerous or even fatal.When activity increases, patients experience   bradycardia , where the heart slows down, because the inhibitory effect of the vagus nerve is stronger.

Patients with decreased tone will develop tachycardia , a fast heart rate, because the nerve is not acting to suppress activity within the heart. This can be the result of a temporary situation, or a long term health problem. Sometimes, changes are not necessarily a sign of disease. Athletes, for example, have a higher vagal tone, and as a result will have a slow resting heart rate.

The vagus nerve experiences reflex reactions in response to certain physical stimuli, like being dashed with cold water or tensing the abdomen. Its goal is to keep the body in a state of homeostasis, where all internal systems are stable and running at a reasonable speed for the conditions. In response to some stimuli, vagal activity can decrease, allowing the heart to speed up. This may increase the flow of blood, facilitating the flight or fight response.

Medical professionals can use a variety of techniques to examine the level of influence being exerted by a patient's parasympathetic nervous system. This can include listening to the heart and running tests with various stimuli to see how the patient responds. If a patient appears to have a disorder involving the vagus nerve, the healthcare professional can look into possible causes and discuss treatment options with the patient. Some patients may be prone to issues like fainting because of changes vagal tone or the intensity of responses to stimuli.

Researchers also believe the vagus nerve can provide important information about stress levels. Fluctuations in tone may indicate rising or falling levels of stress, including chronic stress, where people's bodies may be stuck in a permanent state of heightened awareness. Understanding stress is important for treating conditions like post traumatic stress disorder and can help medical practitioners explore possible methods for treatment and management, including using medications and psychotherapy to help patients reduce stress levels and stay healthy.