Approach to tachycardia: Clinical sciences

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Introduction0:00–0:45

Tachycardia refers to a heart rate above 100 beats per minute, or bpm for short. Once identified, a 12-lead ECG can be used to determine if the tachycardia has a regular or irregular rhythm, and if the QRS complex is narrow or wide.
Further examination of the ECG can reveal details that help identify which type of tachycardia is present. Here’s a high-yield fact!
The typical definition of a normal heart rate is between 60 and 100 bpm. However, although tachycardia is technically considered to be above 100 bpm, the SIRS criteria consider tachycardia to be above 90 bpm.
Now, if a patient presents with signs or symptoms of tachycardia, first perform an ABCDE assessment to determine if they are unstable or stable.

Unstable patient0:45–1:48

If they’re unstable and a pulse is present, then follow the ACLS guidelines for Tachycardia with a Pulse.Next, stabilize their airway, breathing and circulation.
Provide supplemental oxygen, if hypoxemic, to maintain oxygen saturation above 90%. Next, obtain IV access and put your patient on continuous vital sign monitoring including blood pressure, heart rate, and pulse oximetry.
Then assess for signs and symptoms of unstable tachycardia, including heart rate above 150 bpm, hypotension, altered mental status, signs of shock, ischemic chest pain, or acute heart failure.
If your patient has unstable tachycardia, perform immediate synchronized cardioversion.Now let's go back to the ABCDE assessment and discuss stable patients.

Stable patient1:48–2:19

First, perform a focused history and physical examination. Individuals with tachycardia may report symptoms like palpitations, exercise intolerance, lightheadedness, or even syncope.
Additionally, physical exam might reveal a rapid heart rate, and if it’s over 100 beats per minute, you can diagnose stable tachycardia.
Next, obtain a 12-lead ECG and assess the heart rhythm by evaluating the consistency of the intervals from one R wave to the next, which is the R to R interval.

ECG analysis - regular rhythm and sinus tachycardia2:19–3:37

If the R to R interval is the same from beat to beat, this means that you’re dealing with a regular rhythm.Let’s deal with tachycardia with a regular rhythm.
First, assess the QRS duration, which corresponds to the width of the QRS complex. If the QRS complex is narrow, meaning under 120 milliseconds, there’s a narrow complex tachycardia.
In other words, the pacing originates above the ventricles, which suggest you are dealing with supraventricular tachycardia or SVT.
Next, assess the atrial activity on the ECG. Typical “sinus” P waves that precede each QRS complex, which are upright in leads I, II and aVF, are suggestive of sinus tachycardia, meaning it’s originating from the sinoatrial or SA node.
Now, go back to history and physical findings to determine the cause of sympathetic stimulation, which can be either physiologic or non-physiologic.
First, let’s start with physiologic stimulation.If your patient presents with physiologic stressors, like pregnancy, anxiety, pain, or exercise, consider physiologic sinus tachycardia from a non-pathologic stressor.

Physiologic stimulation3:37–4:21

On the other hand, if an individual has evidence of acute illness, like fever, dyspnea, or pallor, evaluate for pathologic conditions that can cause sinus tachycardia like infections, anemia, dehydration, or pulmonary embolism.
In these patients you should think of physiologic sinus tachycardia from a pathologic condition.Now, let’s go back and take a look at non-physiologic causes of sympathetic stimulation.

Non-physiologic stimulation4:21–5:19

If the workup reveals no obvious physiologic cause, but the individual reports symptoms like palpitations, fatigue or syncope, you should evaluate for heart rate changes related to posture.
Check the patient’s heart rate when they move from a supine to standing position. Once they stand up, if their heart rate increases by 30 beats per minute from baseline, or if it exceeds 120 beats per minute within 10 minutes, in the absence of postural hypotension you can diagnose postural orthostatic tachycardia syndrome, or POTS for short.
On the other hand, if the sinus tachycardia is symptomatic but unrelated to postural changes, you can diagnose inappropriate, or non-physiologic sinus tachycardia.Now let’s go back to the ECG and take a look at focal atrial tachycardia.In some cases of supraventricular tachycardia, the atrial activity shows P waves that are abnormal in morphology or deflection, but they’re consistent in appearance.

Focal atrial tachycardia5:19–5:50

This is focal atrial tachycardia, meaning the electrical impulse is coming from a spot in the atrium that’s outside of the SA node.

Typical AVNRT5:50–6:59

Now, let’s take a look at atrioventricular nodal reentrant tachycardia.Suppose you can’t see P waves at all, or if they’re just before or after the QRS complex, diagnose typical atrioventricular nodal reentrant tachycardia, or typical AVNRT.
This type of tachycardia occurs when there’s a reentry circuit within the AV node.Now, here’s a clinical pearl to keep in mind!
An individual presenting with typical AVNRT typically reports “neck pounding,” a symptom that occurs as the right atrium contracts against a closed tricuspid valve.
On exam, you might see neck pulsations that can guide you toward the correct diagnosis. Once you suspect it, you can confirm the diagnosis and treat AVNRT simultaneously!
Give IV adenosine or have the patient perform a vagal maneuver, such as the valsalva. If the tachycardia abruptly terminates, this is highly suggestive of AVNRT.

Orthodromic AVRT6:59–8:22

Let’s take a look at orthodromic AVRT.If the ECG reveals P waves that always follow the QRS, suspect orthodromic atrioventricular reciprocating tachycardia, or orthodromic AVRT for short.
In this form of supraventricular tachycardia, an electrical impulse travels down the AV node to the ventricle in the usual manner, but then returns back to the atrium through the accessory pathway located outside the AV node, creating a P wave that follows after the QRS.
The QRS is narrow because the ventricles are depolarized normally through the fast-conducting His-Purkinje system. Now, here’s a high yield fact!
Electrical signals conducted through an accessory pathway can cause the ventricles to contract earlier than normal, which is called pre-excitation.
Accessory pathways also create a two-way reentry circuit which can facilitate arrhythmias. A classic example is Wolff-Parkinson White syndrome, or WPW for short.
In WPW, the resting ECG has distinct findings, including a short PR interval under 120 milliseconds, delta waves, and a QRS duration over 110 milliseconds.Next, it’s Atrial flutter with rapid ventricular response.

Atrial flutter with rapid ventricular response8:22–8:56

Now let’s say the ECG reveals atypical inverted P with a P to P interval indicating an atrial rate equal to or greater than 250 beats per minute.
The P waves, also known as flutter waves, will have a negative sawtooth appearance in leads II, III and aVF, that conduct at a 2:1 or 3:1 ratio to the ventricles.
These findings are highly suggestive of atrial flutter with a rapid ventricular response.Ok, let’s switch gears and go back to the ECG to assess heart rhythm, and then assess QRS duration.If the patient’s rhythm is regular and the QRS complex is wide, meaning it’s over or equal to 120 milliseconds, first assess the morphology of the QRS complexes.

Wide complex tachycardias - Monomorphic VT8:56–10:22

If QRS complexes appear the same, and there’s AV dissociation, consider monomorphic ventricular tachycardia, or V-tach for short.
Monomorphic V-tach is the most commonly seen wide-complex tachycardia, which typically occurs in individuals with fibrosis of the conductive tissue from previous myocardial ischemia or infarction.Here’s a clinical pearl to keep in mind.
Remember our discussion of accessory pathways causing orthodromic conduction? Sometimes, when there’s an accessory pathway between the atrium and ventricle, the electrical impulses move in an antidromic direction, looping from the atrium to the ventricle through the accessory pathway and back up to the atrium through the AV node.
Just like in orthodromic conduction, this creates a re-entry circuit, maintaining the arrhythmia, but since ventricular excitation through the accessory pathway is slower than through the His-Purkinje system, the QRS is wide, and the tracing looks similar to monomorphic v-tach.

SVT with aberrancy10:22–10:49

On the other hand, the presence of a right or left bundle branch block can also slow spread of cardiac depolarization through the ventricular myocardium, which results in a wide QRS.
This is known as aberrant conduction. When atrial activity is present, but a wide complex tachycardia is present, you can diagnose supraventricular tachycardia with aberrancy.

Irregular rhythm tachycardia - Narrow complex10:49–12:00

Ok, now that we are done with tachycardia with a regular rhythm, let’s go back and switch our focus to tachycardia with an irregular rhythm.
Again, the first step is to assess the QRS duration. If the QRS is narrow, or under 120 milliseconds, assess the atrial activity on the ECG.
If there are no obvious P waves and there’s an irregular ventricular response, that’s atrial fibrillation with a rapid ventricular response.
On the other hand, if you see P waves that have 3 or more distinct morphologies, you’re dealing with multifocal atrial tachycardia, or MAT for short.
Here’s a high yield fact! MAT is often seen in pulmonary disease like COPD, coronary disease, and valvular heart disease, as well as hypomagnesemia and theophylline use.
Management of the underlying condition will sometimes terminate MAT. Be sure to avoid beta-blockers in patients with pulmonary disease.If the ECG shows an irregular rhythm with QRS complexes that are wide, meaning over 120 milliseconds, there’s an irregular wide complex tachycardia.

Wide complex12:00–13:13

In this case, again assess the morphology of each QRS complex. If it’s variable, that’s polymorphic ventricular tachycardia or polymorphic V-tach for short.
Polymorphic V-tach is commonly caused by acute myocardial infarction or hypertrophic cardiomyopathy, so if you see it, make sure to evaluate for these conditions.
If the wide QRS complex waxes and wanes in size in a sinusoidal pattern, diagnose Torsades de pointes. Now, one last high yield fact!
Torsades de pointes is associated with a prolonged QT interval during sinus rhythm, which might be congenital, but also has many reversible causes, including bradycardia; medications like antiarrhythmics, erythromycin, pentamidine, phenothiazines and haloperidol; or electrolyte abnormalities like hypokalemia and hypomagnesemia.
In fact, IV magnesium is the treatment of choice! Alright, as a quick recap… When approaching a patient with tachycardia, first perform the ABCDE assessment to determine if your patient is unstable or stable.

Review13:13–14:59

If unstable with a detectable pulse, follow the ACLS guidelines for Tachycardia with a Pulse. On the other hand, if stable, obtain a 12-lead ECG and assess the heart rhythm.
In stable patients with regular rhythm, first, assess the QRS duration. If the ECG reveals narrow QRS complexes, your next step is to assess the atrial activity to differentiate between the most important conditions.
The first one is sinus tachycardia, which covers physiologic tachycardia from non-pathologic and pathologic causes; and non-physiologic tachycardia, such as postural orthostatic tachycardia syndrome and inappropriate sinus tachycardia.
Other important conditions include focal atrial tachycardia, typical AVNRT, and orthodromic AVRT, as well as atrial flutter with rapid ventricular response.
However, if there’s a regular rhythm with wide QRS complexes, you should assess QRS morphology. In this case, you should think of monomorphic ventricular tachycardia and supraventricular tachycardia with aberrancy.On the other hand, if your patient presents with tachycardia with an irregular rhythm, again assess the QRS duration.
If there’s a narrow QRS complex, consider atrial fibrillation with a rapid ventricular response or multifocal atrial tachycardia.
However, if your patient presents with wide QRS complexes, consider polymorphic ventricular tachycardia and Torsades de pointes.
Approach to tachycardia: Video, Causes, Symptoms | Osmosis