Arrythmias (Ventricular and Atrial)

Question 1

Define “Arrythmia” or “Dysrythmias” vs “Normal Sinus rhythm”.

Answer 1

Normal sinus rhythm is 60-100 bpm, normal rate and rhythm. An “arrythmia” or “dysrhythmia” is any disturbance in the rate, regularity, site of origin or conduction of the cardiac electrical impulse.

Question 2

What are some clinical manifestations of arrythmias? Why do they occur?

Answer 2

Palpitations (awareness of ones own heartbeat, due to sudden acceleration or deceleration of HR), light headedness or syncope (associated with decreased cardiac output), whereas rapid HR can increase cardiac demand for O2 and manifest as angina. It can also manifest as sudden death.

Question 3

What are causes of Arrythmias and how does the mnemonic HIS DEBS help answer this?

Answer 3

H- Hypoxia: myocardium deprived of O2, often caused by severe chronic lung disease or acute PE.
I - Ischemia and Infections: MI’s, anginas, or Myocarditis.
S - Sympathetic Stimulation: Hyperthyroidism, CHF, nervousness or exercise triggers increased sympathetic tone and thus accelerated HR → Arrythmia.
D – Drugs: Quinidine are one of the leading culprits of arrythmias, but this is an anti arrythmia Dx.
E – Electrolyte Disturbances: Hypokalemia, especially, but also imbalances of Ca and Mg → arrythmia.
B – Bradycardia: Slow heart rate seems to induce arrythmia.
S – Stretch: Enlargement or Hypertrophy of atria and ventricles, such as CHF and valvular disease induced hypertrophy.

Question 4

What should be ordered if an arrythmia is suspected?

Answer 4

A rhythm strip, of a lead that can help identify the arrythmia.

Question 5

To calculate heart rate quickly…

Answer 5

Find an R wave on or close to a dark line of the square, and count the big boxes until the next R wave. Quick memorization: 1 box between R wave = 300 bpm. 2 = 150. 3 = 100. 4 = 75. 5 = 60. 6 = 50.
Logic: Each box represents 0.2s, so divide 1 sec/ however many boxes (multiples of 0.2), then multiply by 60.
Ex: 2 boxes between R wave = 0.4 s. 1/0.4 = 2.5. 2.5 x 60 = 150 bpm.
ALTERNATIVE: 300 divided by however many large squares between R waves.

Question 6

What are arrythmias of the sinus origin?

Answer 6

Electrical conduction through the normal pathway, but it might be too fast, too slow, or irregular.

Question 7

What are Eptopic arrythmias?

Answer 7

The pacemaker is something other than the SA node.

Question 8

Re-entrant arrythmias are

Answer 8

Basically, if transmission of impulse goes at the same rate everywhere in the heart there is no problem, however if there is fibrosis due to MI on one region, conduction will be slower in that region as opposed to the other side, so in a circular loop where the original conduction bifurcates and meets up again once the circle closes (at the same time), in a re-entrant arrythmia it wont meet and thus the conduction will go in a loop instead, sending depolarization all over the place, providing the electrical source to override the firing of the SA node.

Question 9

What are conduction blocks?

Answer 9

Normal electrical pathway but encounters a block somewhere

Question 10

What are pre-excitation syndromes?

Answer 10

Electrical pathway follows an accessory conduction pathway that bypass the normal ones, providing a short circuit.

Question 11

What is sinus tachycardia or sinus bradycardia, what conditions accompany these symptoms?

Answer 11

HR greater than 100 is tachycardia, which might be a sign of CHF, severe lung disease or slight hyperthyroidism. HR below 60 can occur in early stages of acute MI. These can also be perfectly normal in exercise or in a trained athlete.

Question 12

What is sinus arrythmia?

Answer 12

Normal rate but slightly irregular rhythm, which might be physiologic (inspiration accelerates HR and expiration slows it down normally).

Question 13

What is sinus arrest, asystole, and escape beats?

Answer 13

SA stops firing is sinus arrest, and prolonged electrical inactivity is asystole, seen in a dead patient. If SA stops firing something else in the heart should take over, and this is called an “escape beat”.
What is the rate of firing of other pacemaker cells besides SA node? Which is the most common for escape beats?
Atrial pacemakers discharge at 60-75 bpm, Junctional pacemakers (found near AV node) 40-60, ventricular pacemaker 30-45 bpm. Junctional pacemakers are most common escape beats.

Question 14

How would junctional escape present in an EKG?

Answer 14

It can show as no p wave, or a retrograde P wave which will show an inverted p wave in lead two and an upright p wave in lead aVR, whereas normally its the other way around.

Question 15

Where would we see the retrograde P wave in a junctional escape?

Answer 15

Before, during or after the qrs complex, but if both atria and ventricles depolarize at the same time the retrograde P wave will be masked by the qrs complex.

Question 16

What is “Sinus Exit Block?”

Answer 16

Failure of SA node depolarization to get into the atria. Which is practically the same thing as a sinus arrest, in either case there is failure of the SA node to depolarize the surrounding tissue.

Question 17

How do escape beats and eptopic rhythms differ?

Answer 17

Escape beats is a couple of beats, eptopic rhythms are sustained rhythms of pacemaker activity outside of the SA node. One of the most common causes of this is digitalis toxicity, where other pacemaker cells get accelerated to be faster than the SA node and thus overrides the SA node.

Question 18

A normal P wave means…

Answer 18

The arrythmia must be caused by something below the atrium, since atrial depolarization is fine.

Question 19

A normal, narrow QRS complex means… but if it isnt normal it means…

Answer 19

The arrythmia must originate above or at the AV node, since ventricular depolarization is fine. If QRS complex is not normal (too wide, greater than 0.12s or greater than 3 small boxes) then something must be wrong within the ventricular myocardium (because depolarization is initiated in the ventricular myocardium NOT the conduction system).

Question 20

What is AV dissociation?

Answer 20

There is no corrolation between the QRS complex and a P wave, normally it should be 1 p wave followed by 1 qrs complex but in an AV dissociation one p wave can be followed by 2 qrs complex before another p wave appears.

Question 21

How can you recognize an atrial premature beat?

Answer 21

It is shaped differently and the timing is off, it will look different from the normal sinus p wave, and will appear earlier than anticipated in the EKG.

Question 22

How can you tell between a junctional escape beat vs a junctional premature beat?

Answer 22

The latter occurs early, prematurely but interposing in the normal sinus rhythm, the latter occurs late following a long pause where the SA fails to fire. Both will be missing a P wave or have a retrograde P wave.

Question 23

What are the 5 types of sustained supraventricular arrythmias?

Answer 23

Paroximal supraventricular tachycardia (PSVT) aka AV nodal reentrant tachycardia
Atrial Flutter
Atrial Fibrillation
Multifocal atrial tachycardia (MAT)
Paroxymal atrial tachycardia (PAT), aka ectopic atrial tachycardia

Question 24

What are the signs of a PSVT? How to find it in an EKG? How to Dx and sometimes treat?

Answer 24

Occurs in absolutely normal hearts perhaps due to coffee intake, 150-250 bpm. Look at V1 for a pseudo R’, a blip in the QRS complex (which is narrow, as normal). Often this is not easily identified. It is a re-entry loop around the AV node, thus it is Dx-ed and sometimes terminated by a carotid message, by interrupting the re-entrant loop.

Question 25

What is Atrial Flutter?

Answer 25

Re-entrant loop that is around the annulus of the tricuspid valves, thus a carotid message will NOT cure this arrythmia, it will however make it more apparent in the EKG. Generally, this loop causes the atria to depolarize very rapidly where 2 p waves are seen followed by a qrs complex. But this depolarization is too rapid for the ventricles to keep up, so a common pattern is this: p p qrs, p p qrs, p p p p, that is, for every two cycles of p wave depol one qrs complex goes missing. “Saw tooth” pattern of P waves.

Question 26

What is Atrial Fibrillation?

Answer 26

Multiple re-entrant cycles occur at completely unpredictable fashion, no true p waves are seen, it appears flat or undulates slightly → ventricles fire randomly, in an irregularly irregular fashion. Thus, we can see fibrillation waves (which are undulating p waves, but sometimes no p waves) + irregularly irregular QRS complex = a fib.

Question 27

What is associated with a fib?

Answer 27

Mitral valve disease, coronary artery disease, hyperthyroidism, PE, pericarditis can also cause this. Most common cause is long standing HTN.

Question 28

How does a MAT appear in the EKG?

Answer 28

Multiple shapes of the P waves (at least 3 different kinds) and irregular PR length and thus qrs complexes rate of being fired varies. P waves however appear before every qrs complex, even if the shapes and timing varies.

Question 29

What are common causes of MAT and what is it?

Answer 29

It results probably from random firing of several different ectopic atrial foci, associated with patients with severe lung disease.

Question 30

Where is PAT common? Why is it caused?

Answer 30

It can be seen in otherwise normal hearts, most commonly in digitalis toxicity. It can be caused due to enhanced automaticity of ectopic atrial focus or from a reentrant circuit within the atria (less common).

Question 31

How can u tell a PAT from a PSVT? What can carotid message do to help Dx?

Answer 31

Sometimes you can’t unless you catch it in the warm-up or cool down period, where the rhythm will be somewhat irregular. Normally in PAT if you dont get the warmup or cool down periods, its a regular rhytm. Carotid message will have NO effect on PAT, but might slow down or even cure PSVT.

Question 32

When can PVC (Premature Ventricular Contractions) be dangerous?

Answer 32

It can trigger ventricular tachycardia or ventricular fibrillation → death.

Question 33

How do PVC’s appear in an EKG? Why?

Answer 33

Wide, bizarre looking qrs complex, might appear randomly or alternate with normal sinus beats. This is because the ventricular depolarization is not following a normal conduction pathway.

Question 34

What is ventricular tachycardia (VTs)?

Answer 34

A run of 3 more more consequetive PVCs, might even appear irregular → medical emergency because this can lead to cardiac arrest.

Question 35

What are Ventricular Fibrillations?

Answer 35

A preterminal event, seen solely in dying hearts. No true qrs complex, the EKG reading jumps spasmodically or undulates gently, must do cardiopulmonary resucitation and electrical defibrillations at once → medical emergency.

Question 36

What is Torsades De Pointes? How does it look?

Answer 36

“Twisting of points” it is seen in patients with prolonged QT intervals (perhaps due to hypo Ca, Mg, or K, or MI). It looks just like VT’s but it spirals around the baseline changing their axis and amplitude.

Question 37

How do accelerated idioventricular rhythm look?

Answer 37

No P waves, wide qrs complex and rate is about 75 bpm.