ECG of the Week

23 December 2013

What’s going on here??

Once again I'm going to ask for a little more.

The correct answer will contain:

1)  The correct interpretation of the ECG

 2) An brief explanation of how you arrived with your answer.

i.e. If the ECG was 3^rd degree block your answer should be something like;

“Third Degree Block. There is complete dissociation of atrial and ventricular activity.”

The first person to submit (e-mail) the correct answer and the brief explanation about the ECG will win a $5.00 Starbucks Gift card!!!

09 December 2013 ECG of the Week: Answer

ECG of the Week: Answer

 09 December 2013

Answer: Acute inferior myocardial infarction

ST elevation in the inferior leads II, III and aVF with reciprocal ST depression in the anterior leads

Congrats to Beth for being the first to send in the correct answer!

ECG of the Week

 09 December 2013

What’s going on here??

Once again I'm going to ask for a little more.

The correct answer will contain:

1)  The correct interpretation of the ECG

 2) An brief explanation of how you arrived with your answer.

i.e. If the ECG was 3^rd degree block your answer should be something like;

“Third Degree Block. There is complete dissociation of atrial and ventricular activity.”

The first person to submit (e-mail) the correct answer and the brief explanation about the ECG will win a $5.00 Starbucks Gift card!!!

Electrophysiology....Where to start.

Electrophysiology

Where to start?

Cardiac Electrophysiology is the study of the heart’s electrical system. The process of learning electrophysiology can be very confusing. Knowing where to start studying is key. 

 Understanding how the heart initiates an electrical impulse and conducts that impulse throughout the heart is the foundation of electrophysiology. This "foundation" allows for a better understanding of arrhythmias and their treatment.

 Needless to say, it allows for a better understanding of what's going on in the EP Lab and more important, why.

The bottom line.....Figure this out and you just about have EP whipped!

The Cardiac Action Potential

“The Foundation”

“The cardiac action potential is one of the most despised and misunderstood topics in electrophysiologic testing. It is also a leading cause of the mystique surrounding electrophysiology testing."  R. Fogrose, M.D.

I'll try to make this as painless as possible.

The following are the basics of how and why heart cells contract.

Cardiac Cells

Electrically-charged.....

Ions are electrically-charged particles contained in fluid that fills and surrounds the cardiac cells.

A positively-charged (+) ion has lost an electron.

                       

     A negatively-charged (-) ion has gained an electron.

The cardiac myocyte (Heart Cell) is a specialized muscle cell and is only found in the heart. The most important function of heart cells is to contract rhythmically and systematically.  The contraction of the heart as a whole is as a direct result of the contraction of all of the tiny cells of the heart muscle called Myocytes.

Myocytes branch to form a “Y” and interlock so that when one cell is stimulated to contract, so are the adjacent cells

 Each Myocyte has a nucleus and multiple myofibrils – parallel strands of tissue that run the length of the cell. Myocytes are separated by discs that have low electrical impedance, which allows fast conduction of electrical impulse.

(Fig 1) "Y" shaped Myocytes

Each cell in our body is surrounded by a thin cell membrane. Different ions can move across the cell membrane through the special ion channels (think of the channels as gates or gated channels). The channels can freely let one type of ion go through the membrane and block passage of other types of ions.

Because ions are charged molecules, an electrical gradient is also established across (between outside and inside) the cell membrane, transforming each cell into a tiny battery. The resulting voltage difference across the cell membrane is called the Transmembrane Potential.

The Transmembrane Potential is negative inside then outside, to be more exact it has a resting membrane potential of approximately (- 0.1 V or -100mV).

Depolarization

The gated channels, in response to a stimulus (electrical, mechanical, or chemical), open and allow positive charged sodium ions to rush into the cell, causing a rapid positively directed change in the transmembrane potential. 

When these stereotypical voltage changes are graphed against time, the result is the cardiac action potential.





(Fig 2) The 5 Phases of the Cardiac Action Potential

Phase 0 is the immediate depolarization that sends the voltage past the zero millivolt level, making it positive. This is due to the sudden increase in membrane permeability to sodium ions and decrease in potassium permeability. Once the high sodium permeability decreases, slight repolarization occurs. The moment when the voltage declines makes up Phase 1.

The membrane potential then reaches a steady point at around zero millivolts. This is called the plateau of the action potential, and it makes up the gist of Phase 2 as well. There is a reason for this moment of steadiness in the voltage. The inward flow of calcium ions is equal to that of the outward flow of potassium ions.

So, why doesn’t the voltage just remain at zero? Well, because of the falling membrane potential, the calcium permeability declines while the potassium permeability increases. This initiates repolarization once again, and it makes up Phase 3. The voltage decreases to its original value where it will remain steady until the next action potential is generated (Phase 4).

Effective Refractory Period

Once an action potential is initiated, there is a period of time comprising phases 0, 1, 2, and part of phase 3 that a new action potential cannot be initiated. This is termed the effective refractory period (ERP) or the absolute refractory period (ARP) of the cell. During the ERP, stimulation of the cell by an adjacent cell undergoing depolarization does not produce new, propagated action potentials.

The ERP acts as a protective mechanism in the heart by preventing multiple, compounded action potentials from occurring (i.e., it limits the frequency of depolarization and therefore heart rate). This is important because at very high heart rates, the heart would be unable to adequately fill with blood and therefore ventricular ejection would be reduced.

Automaticity

Automaticity is the ability of the Myocytes to depolarize spontaneously, i.e. without external electrical stimulation from the nervous system.

This spontaneous depolarization is due to the plasma membranes within the within certain area of the heart that have reduced permeability to potassium (K+), but still allow passive transfer of calcium ions, allowing a net charge to build until it spontaneously depolarizes.  

That’s it!...For now!          I hope that wasn't to painful. 

Next will be normal conduction.

Answer: ECG of the Week 11 November 2013

Answer: ECG of the Week

11 November 2013

 

Answer: Acute anterolateral MI

Acute anterolateral MI is recongnized by ST segment elevation in leads I, aVL and the precordial leads overlying the anterior and lateral surfaces of the heart (V3 - V6). Generally speaking, the more significant the ST elevation , the more severe the infarction. The lack of reciprocal ST changes in the inferior leads made this one a little difficult.

 

The take away about this ECG, if you see ST Elevation like this...Let someone Know!!

 

As for the winner of this week’s gift card, I need to confer with the “judges” for a ruling about this one.

 

 

 

 

 

 

 

 

ECG of the Week 

11 November 2013

***See Below for New Rules

What’s going on here??

This week I'm going to ask for a little more.

The correct answer will contain:

1)      The correct interpretation of the ECG

2)      An brief explanation of how you arrived with your answer.

i.e. If the ECG was 3^rd degree block your answer should be something like;

              “Third Degree Block. There is complete dissociation of atrial and ventricular activity.”

The first person to submit (e-mail) the correct answer and the brief explanation about the ECG will win a $5.00 Starbucks Gift card!!!

Answer to ECG of the Week 04 November 2013

                 Answer  
         ECG of the Week 

04 November 2013

This ECG was a little tricky.

I’ll let this week’s winner provide the answer;

“It’s underlying complete heart block with Ventricular pacing turned down to a rate of 30-35?”

            Complete heart block is easily identified by the complete disassociation of P waves to Ventricular QRS's.

            The absence of ventricular pacing spikes make the second part of the interpretation is a little more difficult.

            The Morphology of the QRS is all that you had to go on (where the ventricles are being stimulated from or where the ventricular impulse begins).

           

First look at the Ventricular Rhythm, its regular.  Next look at lead V₁. The QRS is negative and very wide (>120mS), so that makes it a Left Bundle Branch Block (LBBB). A LBBB indicates that the impulse is originating somewhere in the right ventricle.

            Look at all of the V leads. In the V leads there is not a transition from Negative to Positive. Meaning The V leads are “pointing” at the right ventricular apex. 

Question, when a pacemaker is implanted, where is the RV lead placed? Answer; The right ventricular apex.

This patient was 100% pacer-dependent. They were in the procedure room for an A-fib ablation. The patients pacemaker had be programmed to VVI 40 just prior to the start of the procedure. The ECG was a result of the device programming.

Congratulations to Beth…..again!!!!  She was the first to submit the correct answer.

Honorable mention this week goes to: Theresa, Maribeth, Jamie and Diana.

Reminder: EP Education Lecture 05 November 2013

Just a Reminder:

05 November 2013

EP Education Lecture will be: 
SubQ ICD-Placement and Nursing Implications

Dr. Christopher Rowley, M.D. 
Electrophysiology Fellow and Clinical Instructor Cardiology Division

Medical University of South Carolina    

Time/Location: 0730hrs in Prep and Recovery Conference Room

See You There!

ECG of the Week 04 November 2013

         ECG of the Week 

04 November 2013

This ECG is a little tricky. Look closely at it.

Hard copies will be on the board.

The first person to submit (e-mail) the correct answer and a brief explanation about the ECG will win a $5.00 Starbucks Gift card!!! 

I'll Post the answer and winner on Monday.

Have fun and Good Luck!!!

Answer to the ECG of the Week 28 October 2013

  Answer: ECG of the Week

Answer: Counterclockwise Typical Atrial Flutter

Typical Atrial Flutter can be identified by the characteristic ‘sawtooth’ pattern. The direction of travel can be determined by looking at the inferior leads (leads II, III, and avF). In this case they are negative, which indicates counterclockwise flutter. Positive flutter waves in the inferior leads would indicate Clockwise Typical Atrial Flutter.

Congratulations to Beth for being the first person to submit the correct answer. 

Honorable Mention goes to Theresa and Jamie who both answered correctly but submitted their answers after Beth.

ECG of the Week 28 October 2013

ECG of the Week

28 October 2013

What’s going on here???

This week's ECG is again pretty easy.

However.

This week I am looking for a more detail. What type?? What Direction?? What Rate?? Be specific.

The first person to submit (e-mail) the correct answer and a brief explanation about the ECG will win a $5.00 Starbucks Giftcard!!! 

I'll Post the answer and winner on Monday.

Have fun and Good Luck!!!

  

Answer for ECG of the Week 21 October 2013

ECG of the Week

21 October 2013

Answer:   Atrial Fibrilliation

This is a good basic 12 lead ECG example of atrial fibrillation with a rapid ventricular response (approx. 150bpm) showing the identifying characteristics of atrial fibrillation:  no P waves, an irregularly-irregular rhythm, and a "fibrillatory" baseline. 

Congratulations to Theresa for correctly identifying the ECG. 

Great Job!!!

The Basic EP Study

The Basic Electrophysiologic Study

An electrophysiologic, or EP, study provides information that is key to diagnosing and treating arrhythmias.

EP studies most often are recommended for patients with symptoms indicative of heart rhythm disorders or for people who may be at risk for Sudden Cardiac Death.

What EP Studies can do.

Intracardiac electrophysiologic studies (EPS) are utilized to diagnosis and treat arrhythmias:

  1) Sinus Node Dysfunction

  2) Intraventricular and AV conduction disturbances,

  3) Supraventricular Tachycardia's (SVT)

  4) Ventricular tachycardia's (VT's),

  5) Preexcitation syndromes (WPW)

  6) Ventricular fibrillation (VF).

The diagnostic electrode catheters

Diagnostic electrode catheters consist of insulated wires attached to electrodes. At the proximal (near) end of the catheter, each wire is attached to a plug that can be connected to an external recording or pacing device.

A common electrode catheter is quadripolar. It has two electrode pairs that can be used to record EGM information at two intracardiac sites or record and pace simultaneously. Typically, the proximal pair records electrical activity and the distal pair delivers pacing stimuli.

Electrode size varies from 2 mm to 8 mm and electrode spacing from 2 mm to 10 mm. Close spacing (2 mm) provides detail in a small area of tissue. Greater spacing (5 to 10 mm) reflects a larger tissue area. All electrodes are numbered. The distal electrode is always number 1.

Electrode catheters are available in a variety of sizes and shapes (e.g., halo, basket). Catheters may have multiple electrode pairs that can record multiple IEGMs simultaneously, such as the Decapolar catheter.

Placement of Catheters

HRA Catheter

The high right atrial (HRA) catheter is placed in the lateral wall of the high right atrium, near the junction of the SVC and as close to the SA node as possible.

The HRA catheter is positioned away from the ventricles, so it senses atrial activity only. The HRA EGM is somewhat aligned with the surface P-wave since both represent atrial depolarization.

HIS Catheter

The His bundle (HIS) catheter is placed across the posterior aspect of the tricuspid valve, as close to the His bundle as possible. It straddles the major structures of the AV conduction system.

The HIS catheter electrodes sense electrical signals in the low right atrium, AV node, His bundle, and a portion of the right ventricle. Proper catheter placement is essential for recording conduction time. The catheter is generally maneuvered until the best electrode recording pair is established.

The HIS EGM has three major deflections:

            − The A spike (first deflection) represents depolarization of the low right atrium as the electrical impulse enters he AV node. It is loosely aligned with the HRA signal and the surface P-wave.

           

            − The H spike (second deflection) represents His bundle depolarization as the impulse exits the AV node. It is loosely aligned with the surface PR interval.

           

            − The V spike (third deflection) represents depolarization of the right ventricle near the HIS catheter. It is loosely aligned with the surface QRS complex.

Note: No deflection is produced as the electrical impulse travels through the AV node because AV conduction is slow.

CS Catheter

The coronary sinus (CS) catheter is placed posterior and slightly inferior to the tricuspid valve. It is close to the posterior aspect of the mitral valve.

The CS catheter follows the coronary sinus which lies in the AV groove. The proximal electrodes are more atrial and the distal electrodes lie directly between the atria and the ventricles.

Because the CS catheter lies in the AV groove, the CS EGM records both atrial and ventricular signals. From left to right, the atrial component of the CS EGM is loosely aligned with the atrial component of the HIS and HRA signals and the surface P-wave.

RV Catheter

The right ventricular (RV) catheter is placed in the right ventricular apex (RVA). It should not sense atrial or His bundle signals as they are out of range.

The RVA EGM records electrical activity in the right ventricle and right bundle branch. From right to left, the RV signal can be loosely aligned with the ventricular component of the CS and HIS signals and the surface QRS complex.

Now that the Catheters in Placed

Its time for the EP Study.

                        The EP Study can be broken down into 3 parts:

                                    1) Basic Intervals

                                    2) Atrial Study

                                    3) Ventricular Study

(See Part II   Basic Intervals)

How to Measure Basic Intervals

Basic Intervals

The measurement of vital signs is a part of basic patient assessment. In Electrophysiology, Basic Intervals (BI’s) is the basic assessment of the cardiac conduction system. Sort of the "vital signs" of the conduction system.

Basic Intervals measure the amount of time it takes an impulse to travel thru the conduction system.  Ideally this is performed when the patient is in Sinus Rhythm. 

Basic Intervals are usually taken during an EP study and at the end of an ablation procedure.

How to Measure Basic Intervals

**Note**    Learning to measure Basic Intervals takes lots of time,  practice and patience.

An easy way to learn how measure BI’s is, during a procedure,  have a Fellow or Attending measure and record  basic interval measurements and then reproduce their measurements yourself. 

P-A)  Measured between the earliest activation recorded atrial activity in any channel (either the   P- wave onset, or that of the earliest arterial electrogram) and the rapid deflection of the atrial electrogram (not earliest) on the HIS Bundle catheter.                                                                            Normal P-A interval is; 25-55 mS.

A-H)  Measured between the rapid deflection (not the point where the A signal leaves the baseline) atrial electrogram recorded by the HIS catheter and earliest deflection of the HIS electrogram itself.    Normal A-H interval is; 55-125 mS.

H-V) Measured from the earliest deflection of the HIS electrogram and the earliest recorded ventricular activation.  Normal H-V is; 35-60mS

P-R)  Measured from the earliest activation recorded atrial activity and the earliest recorded ventricular activation. Normal P-R interval is; 120mS to 200mS.

QRS)  Measured from the earliest recorded ventricular activation to the point that the ventricular electrogram returns to baseline.  Normal QRS is; ≤ 100mS.

QT) Measured from the earliest ventricular activation to the point the T-Wave returns back to baseline.  Normal QT is; Men-≤ 450/Women-≤ 470

R-R)   Measured from the earliest ventricular activation to the earliest ventricular activation of the next Sinus Beat.   Normal R-R is; 1000mS to 600mS (60bpm to 100bpm).

Measured Basic Intervals

Again, it takes time and practice and patience to learn to measure Basic Intervals. Don’t get discouraged…….keep trying!