Cardiopulm Unit 2 Electrocardiography Flashcards
What is Sinus Rhythm?
Any cardiac rhythm in which depolarizes of the cardiac muscle begins at the sinus node
Abnormal cardiac rates/rhythms can occur if what?
- The SA node fails to function normally (e.g., sinus bradycardia or tachycardia)
- Other pacemaker sites within the atria or ventricles (e.g., ectopic pacemakes) trigger depolarization
- Conduction of electrical impulses between the hearts atria and ventricles is delayed or interrupted (AV block)
- Abnormal conduction pathways are followed (e.g., accessory pathways between atria and ventricles)
What happens as the wave of depolarization moves toward a positive electroid?
A positive deflection is observed on the ECG
What happens as the wave of depolarization moves away from a positive electroid?
A negative deflection is observed on the ECG
What happens as the wave of depolarization moves perpendicular to the positive electroid?
An isoelectric deflection is observed on the ECG (i.e., a deflection with both positive and negative components)
Lead 1, “looks” at what aspect of the heart?
It looks at the lateral aspect of the heart
Lead 2, “looks’’ at what aspect of the heart?
The base of the heart
Lead 3, looks at what aspect of the heart?
The inferior medial aspect of the heart
What do precoidial leads do?
The provide a view of the heart in the transverse plane
(Labled V1-V6)
In an ECG, what is a segment?
The region between two waves
In an ECG, what is an Interval?
A duration of time that includes one segment and one or more waves
What does the P wave represent?
Depolarization of both atria. The P wave is the first ECG Deflection
What is the P-R Interval?
This is the electrical transmission from the atria to the ventricles
This typically takes 0.12-0.20sec
What does the QRS Complex represent?
The QRS complex indicates ventricular depolarization
- The R wave is the initial positive deflection
- The Negative deflection before the R wave is the Q wave
- The negative deflection after the R wave is the S wave
This typically takes 0.06-0.10sec
What does the S-T segment and T wave represent?
Both represent Ventricular Repolarization
- The S-T segment extends from the S wave to the beginning of the T wave
- The T-wave represents the repolarization of both ventricles
What are the S-T segments and T wave sensitive indicators of?
They are sensitive indicators of the oxygen supply status of the ventricular myocardium
What does R-R Wave represent?
Ventricular Depolarization (Ventricular systole)
- The measurment between each R-R wave give you sense on how regular or irregular the rhythm is
What is Sinus Bradycardia?
This is characterized by a sinoatrial (SA) node discharge rate less than 60bpm with normal P waves and QRS complexes
When is Sinus Bradycardia normal in/at?
- Rest
- Sleep
- Well-trained athletes due to increased vagal tone and stroke volume
- With some medications (e.g., beta- or calcium channel-blockers)
What are some Pathologic Causes of Sinus Bradycardia?
- Depressed intrinsic SA node automaticity due to ischemic heart disease or cardiomyopathy
- Heart blocks
- Metabolic dysfunction (e.g., hypothyroidism)
- TBI and increased intracranial pressures (Cushings’ reflex)
What is important to know about Mild Sinus Bradycardia?
- Its usually asymptomatic and does not require treatment. More pronounced HR decline, usually in the setting of a pathological condition, could produce a fall in cardiac output with Sx of fatigue, light-headedness, confusion, and/or syncope
What is the significance of Symptomatic Sinus Bradycardia?
The key clinical question is whether the bradycardia is causes the patients Sx, or some other illness is causing bradycardia
- All bradycardias that present with signs or symptoms (hypotension, signs of heart failure, ventricular arrhythmias) should be evaluated at a higher level of medical care
What is Sinus Tachycardia Characterized by?
Its characterized by a sinoatrial (SA) node discharge rate greater than 100bpm with normal P waves and QRS complexes
- This most often results from increased sympathetic and/or decreased parasympathetic (vagal) tone
When is Sinus Tachycardia appropriate? When is it from a pathological conditions?
- Its appropriate in response to exercise (~10bpm per MET)
Pathological conditions such as:
- Fever
- Pain
- Infections
- Hypoxemia
- Hyperthyroidism
- Hypovolemia (e.g., hemorrhage, dehydration)
- Amenia
- Low Cardiac output
What might Sinus Tachycardia lead to? What signs should we look for?
If the heart rate is too high, cardiac output may fall due to the markedly reduced ventricular filling time. In these cases, look for signs of:
-Hypotension
-Acute Altered Mental status (AMS)
-Ischemic chest discomfort due to increasing myocardial oxygen demand but reduced coronary blood flow
-Acute Heart Failure
- In these cases, a higher level of medical attention is necessary in order to determine whether the patient’s tachycardia is producing hemodynamic instability and other S/S or whether the S/S are producing tachycardia
What is Supraventricular Tachycardia (SVT)?
Rapid heart rhythm originating above the hearts ventricles, typcially involving the atria or atrioventricular node
What are Ectopic beats/focus?
Areas where the heart contracts itself; outside the normal conduction pathway.
- They typically have weaker contractions
Supraventricular Tachycardia
What is Atrial Tachycardia?
Abnormal heart rhythm that is characterized by a series of three or more consecutive ectopic beats originating in the atria
Supraventricular Tachycardia
What is Atrial Flutter?
This is characterized by a rapid, organized, and regular atrial rhythm. It has a unique re-entrant circuit, usually in the right atrium, which leads to the classic “Sawtooth” patten seen on the ECG
- Usually has a rate of 250-350bpm
- Usually has more than 1 P wave before every QRS complex
Re-entrant Circuit: Self-sustaining electrical pathway in the heart in which the impulse continues to circle through the tissue, causing repeated stimulation and a rapid heartbeat
How can Atrial Flutter occur? What type of patients can this occur in?
The structural and functional changes to the atrial myocardium following an Myocaridal Infarction or other sources of myocardial injury (e.g., surgery) can alter normal electrial conduction paths and set up a reentrant circuit.
- Atrial flutters can occur in individuals with other pre-existing heart conditions (e.g., valvular disease, pericarditis), have renal failure, hypertension, or chronic lung disease
Supraventricular Tachycardia
Is Atrial Flutter Permanent?
This may be paroxysmal/transient, persisting (lasting days or weeks), or permanent.
Supraventricular Tachycardia
What is Atrial Fibrillation?
The most common type of Serious Arrhythmia. This is characterized by a very fast and disorganized atrail rhythm, resulting from multiple ectopic foci and/or multiple reentry circuits generating electrical impulses in a chaotic manner. This leads to irregular rhythm known as “irregularly irregular” pulse.
- Erratic quivering or twitching of the atrial muscle
How can you tell the difference between Atrial Flutter and Atrial Fibrillation?
- Atrial Flutter is a more organized and REGULAR atrial rhythm
- Atrial Fibrillation, has no true P waves are found. The AV node acts to control the most of the impulses that initiate QRS complex; therefore a totally irregularly irregular rhythm exist
Is this picture an example of Atrial Flutter or Atrial Fibrillation?
Atrial Fibrillation
- There are no true P waves
Is this picture an example of Atrial Flutter or Atrial Fibrillation?
Atrial Flutter
- The P waves are organized and in rhythm, it also makes a “Sawtooth” like pattern
What can Atrial Flutter and Atrial Fibrillation result in?
Although they are not, in and of themselves, considered lifethreatening, they can lead to serious and potentially life-threatening complications if not properly managed:
- Stroke risk due to blood stasis
- Induce heart failure via tachycardia-induced cardiomyopathy
Sx of both atrial flutter and atrial fibrillation will largely depend on underlying ventricular rate