Lec8 ECG part I- Practice strips

Quiz 3 content --Practice flashcards covering ECG rhythm strip interpretation, cardiac electrical conduction, and clinical impressions from BMS 595 lecture notes.

What is the preferred baseline segment on an ECG, according to the systematic approach?

The TP segment is a better baseline than the PR segment. TP represents the only true period of cardiac electrical silence

What is the standard value of the horizontal X-axis on ECG paper?

Time ($25\,\text{mm/sec}$).

What is the standard value of the vertical Y-axis on ECG paper?

Voltage ($10\,\text{mm/mV}$).

What occurrence characterizes Phase 0 of cardiac electrical events?

Ventricular Depolarization featuring fast $Na^+$ channel influx and the beginning of the QRS complex.

What happens during Phase 1 of the cardiac action potential?

Initial rapid repolarization (drop in mV) occurs due to the closing of fast $Na^+$ channels and $Cl^-$ entering the cell.

What occurs during the Phase 2 'Plateau stage'?

Inflow and outflow currents are balanced and the EKG returns to baseline; slow $Na^+$ and $Ca^{++}$ channels are open.

What is shown on the EKG during Phase 3?

A repolarizing T wave, while $K^+$ channels open, $Ca^{++}$ channels close, and $K^+$ escapes from the cell.

What role does the Na-K ATP pump play in Phase 4?

It pumps $Na^+$ out of and $K^+$ into the myocyte during the recovery phase.

Define Cardiac Arrest

Cardiac arrest occurs when the heart malfunctions and stops beating unexpectedly, triggered by an electrical malfunction. (arrythmia)

What physical state does a person enter seconds after cardiac arrest?

The person becomes unresponsive, is not breathing, or is only gasping.

In terms of categories, what kind of problem is Cardiac Arrest labeled as?

An 'ELECTRICAL' problem.

What causes a Heart Attack to occur?

A heart attack occurs when blood flow to the heart is blocked (a 'CIRCULATION' problem).

What are the specific symptoms of a heart attack mentioned for women?

Shortness of breath, nausea/vomiting, and back or jaw pain.

How frequently do out-of-hospital cardiac arrests occur annually in the United States?

Nearly $360,000$ annually.

What is the link between heart attacks and cardiac arrest?

Most heart attacks do not lead to cardiac arrest, but when cardiac arrest occurs, heart attack is a common cause.

Where are the Internodal Pathways found in the heart?

In the walls of the right atrium and inter-atrial septum.

What are the three specific internodal pathways?

Anterior, Middle, and Posterior.

What is the function of the Bachmann bundle?

It is a small tract of specialized cells that transmits impulses through the inter-atrial septum.

What is the 'normal' range (inherent pacing rate) for the SA Node?

60-100 bpm

What is the inherent pacing rate of atrial foci?

60-80 bpm

What is the inherent pacing rate of junctional foci?

40-60 BPM

What is the inherent pacing rate of ventricular foci?

20-40 bpm

What is the function of the SA Node regarding other lower foci?

The SA Node overdrive-suppresses all lower foci.

On a Lead II rhythm strip, how many big boxes represent a 3-second interval?

15 big boxes (noted by 3-second hash marks).

Which wall of the heart is visualized by the Lead II rhythm strip?

The inferior wall of the LV.

Which two areas of the heart are NOT visualized well by any chest lead?

The right ventricular wall ($X$) and the left ventricle posterior wall ($Y$).

According to the Precordial lead axes, when does an upward deflection occur?

When current flows toward the arrowheads.

According to the Precordial lead axes, when does a downward deflection occur?

When current flows away from the arrowheads.

According to the Precordial lead axes, when does no deflection occur?

When current flows perpendicular to the arrows (axes).

What are the names of the three Augmented Limb Leads?

Lead aVR, Lead aVL, and Lead aVF.

What does the Frontal plane of the 3-D view represent in cardiac activity?

Axis Deviation (associated with the 6 limb leads).

What does the Horizontal plane of the 3-D view represent in cardiac activity?

Axis Rotation (associated with the 6 chest leads).

Which leads localize the lateral LCx (Left Circumflex) coronary artery?

Leads I, aVL, V5, and V6 (also aVR).

Which leads localize the inferior RCA (Right Coronary Artery)?

Leads II, III, and aVF.

Which leads localize the septal LAD (Left Anterior Descending) artery?

Leads V1 and V2.

Which leads localize the anterior LAD artery?

Leads V3 and V4.

What are the five main components of ECG interpretation?

Heart Rate, Rhythm, Axis, Wave morphology, and Intervals and segments analysis.

What is the definition of Tachycardia?

$> 100\,\text{bpm}$.

What is the definition of Bradycardia?

$< 60\,\text{bpm}$.

How is the heart rate calculated if a patient has a regular rhythm using large squares?

Divide 300 by the number of large squares present within one $R\text{-}R$ interval.

If there are 4 large squares in an $R\text{-}R$ interval, what is the heart rate?

$75\,\text{bpm}$ ($300/4$).

How is the heart rate calculated for an irregular heart rhythm using a rhythm strip?

Multiply the number of complexes on a 10-second rhythm strip by 6.

What constitutes a 'Regularly irregular' heart rhythm?

A recurrent pattern of irregularity.

What constitutes an 'Irregularly irregular' heart rhythm?

Completely disorganized.

How can rhythm regularity be manually checked on a physical rhythm strip?

Mark out several consecutive $R\text{-}R$ intervals on a piece of paper and move them along the strip to check if subsequent intervals are similar.

What ECG findings suggest a diagnosis of atrial fibrillation?

Absent P waves and an irregular rhythm.

What is the normal duration for a PR interval?

Between $120\text{--}200\,\text{ms}$ ($3\text{--}5$ small squares).

What does a prolonged PR interval ($> 0.2\,\text{seconds}$) suggest?

Atrioventricular delay (AV block).

What are the typical findings for First-degree heart block (AV block)?

A fixed prolonged PR interval ($> 200\,\text{ms}$).

Describe typical ECG findings in Mobitz type 1 AV block.

Progressive prolongation of the PR interval until eventually the atrial impulse is not conducted and the QRS complex is dropped.

What happens after a QRS complex is dropped in Mobitz type 1 AV block?

AV nodal conduction resumes with the next beat and the sequence repeats.

What are the typical ECG findings in Mobitz type 2 AV block?

A consistent PR interval duration with intermittently dropped QRS complexes due to a failure of conduction.

What repeating cycles are common in Mobitz type 2 block?

Dropping every 3rd ($3:1$ block) or 4th ($4:1$ block) P wave.

What characterizes Third-degree AV block?

The presence of P waves and QRS complexes that have no association with each other due to the atria and ventricles functioning independently.

What maintains cardiac function in a third-degree AV block?

A junctional or ventricular pacemaker.

What is the duration and source of a Narrow-complex escape rhythm?

$< 0.12\,\text{seconds}$; originates above the bifurcation of the bundle of His.

What is the duration and source of a Broad-complex escape rhythm?

$> 0.12\,\text{seconds}$; originates from below the bifurcation of the bundle of His.

Where does First-degree AV block anatomically occur?

Between the SA node and the AV node (within the atrium).

Where does Mobitz I (Wenckebach) AV block occur?

IN the AV node.

Where does Mobitz II AV block occur?

After the AV node in the bundle of His or Purkinje fibers.

Where does Third-degree AV block occur?

Anywhere from the AV node down causing complete blockage of conduction.

What are two possible meanings for a shortened PR interval?

The P-wave originates closer to the AV node, or the atrial impulse is taking an accessory pathway shortcut.

What is the 'delta wave' a sign of?

The ventricles are being activated earlier than normal from a point distant to the AV node, causing a slurred upstroke of the QRS complex.

What is required to diagnose Wolff-Parkinson-White syndrome besides a delta wave?

Evidence of tachyarrhythmias.

What three characteristics should be assessed for a QRS complex?

Width, Height, and Morphology.

What is the threshold for a NARROW QRS complex?

$< 0.12\,\text{seconds}$.

When does a narrow QRS complex occur?

When the impulse is conducted down the bundle of His and the Purkinje fiber to the ventricles.

What causes a broad QRS complex to occur?

An abnormal depolarization sequence, such as a ventricular ectopic or a bundle branch block.

Why does a bundle branch block result in a broad QRS complex?

The impulse reaches one ventricle rapidly then must spread slowly across the myocardium to the other ventricle.

How are small QRS complexes defined for limb leads?

$< 5\,\text{mm}$.

How are small QRS complexes defined for chest leads?

$< 10\,\text{mm}$.

What do tall QRS complexes imply?

Ventricular hypertrophy (though it can be due to body habitus).

What are two algorithms for measuring Left Ventricular Hypertrophy (LVH)?

Sokolow-Lyon index or the Cornell index.

What criteria define a pathological Q wave?

It is $> 25\%$ the size of the following R wave OR $> 2\,\text{mm}$ in height and $> 40\,\text{ms}$ in width.

What should be checked to rule out previous myocardial infarction when a Q wave is found?

Look for Q waves in an entire territory (e.g. anterior or inferior).

Where should the transition from $S > R$ to $R > S$ wave occur across the chest leads?

In leads V3 or V4.

What can poor R wave progression (S > R through V5 and V6) signify?

A sign of previous MI or poor lead position in large people.

Define the ST segment.

The part of the ECG between the end of the S wave and the start of the T wave.

What is the J point on an ECG?

The point where the S wave joins the ST segment.

What is 'High take-off' or 'benign early repolarization'?

A normal variant causing a raised J point and subsequent raised ST segment.

At what age is benign early repolarization most common?

Mostly under the age of 50.

How do T waves in benign early repolarization differ from those in STEMI?

In benign early repolarization, T waves are raised; in STEMI, the T wave remains the same size while the ST segment is raised.

When is ST-elevation considered significant in limb leads?

Greater than $1\,\text{mm}$ ($1$ small square) in 2 or more contiguous leads.

When is ST-elevation considered significant in chest leads?

$> 2\,\text{mm}$ in 2 or more chest leads.

What is the most common cause of significant ST-elevation?

Acute full-thickness myocardial infarction.

What indicates myocardial ischemia regarding ST depression?

ST depression $\ge 0.5\,\text{mm}$ in $\ge 2$ contiguous leads.

When are T waves considered 'tall' in limb and chest leads?

$> 5\,\text{mm}$ in limb leads and $> 10\,\text{mm}$ in chest leads.

What condition is classically associated with 'tall tented T waves'?

Hyperkaliemia.

Where are inverted T waves considered a normal variant?

Inverted in V1 is normal, and inversion in lead III is a normal variant.

In which leads does Left Ventricular Hypertrophy typically show T wave inversion?

In the lateral leads.

According to the notes, what percentage of ITU patients have evidence of T wave inversion?

Around $50\%$.Ratio: around 50%.

What can biphasic T waves indicate?

Ischemia and hypokalemia.

Flattened T waves are a non-specific sign of which two issues?

Ischemia or electrolyte imbalance.

What is a U wave, and where is it best seen?

A $> 0.5\,\text{mm}$ deflection after the T wave, best seen in V2 or V3.

What is the first ECG change seen during STEMI?

'Hyperacute T waves' which appear peaked.