1 E & 2A : Electrocardiogram (ECG) & Cardiac Cycle Flashcards
What is the Lead I of the ECG?
The potential difference recorded between the electrodes on the persons left arm (LA) and right arm (RA )
What is the Basic (3 Lead) ECG?
4 electrodes are placed on both the patient’s arms and the left leg
Does a lead equals a electrode?
What is a lead?
No!
a lead is a particular view of electrical actiivity of the heart
What is lead II and III?
Lim leads recorded between the right arm and left leg LEAD II
and left arm and left leg LEAD III
How many electrodes are used?
What are the 6 precordial(chest) electrodes?
What are the 4 limb electrodes?
10 used.
V1, V2, V3, V4, V5, V6
RA, LA, RL, and LL–> Give 6 views (I, II, III, aVL, aVF, and aVR)
What is the P wave?
What is the T wave?
P–>depolarization of the atria
T–> repolarization of the ventricles
What is the QRS complex?
- depolarization of the ventricles
- triggers main pumping contractions
What is the PQ segment ?
-Time when the impulse is traveling through the AV node, bundle of His, and bundle branches
What is the QT interval?
**Onset of QRS complex to end of T wave
What is the ST segment?
End of the QRS complex to onset of T wave
What is the ST interval?
End of QRS complex to end of T wave
What is a normal sinus rhythm (NSR)
Rate- within normal limits for age; in adults 60-100 bpm
Rhythm- Regular
P waves- uniform, positive (upright) in lead II, one precedes each QRS complex
PR interval- within normal limits for age & constant from beat to beat;ln adults 0.12-0.20 sec
QRS duration- 0.10 sec or less
What is the PR interval?
Onset of P wave to middle of QRS complex
What is overdrive suppression?
The AV Node and the Purkinje fibers are LATENT PACEMAKERS that my exhibit automaticity & override the SA node if it is suppresed.
- The intrinsic rate of phase 4 depolarization ( & HR ) is FASTEST in the SA node and SLOWEST in the Purkinje fibers.
***SA NODE–> AV NODE–> Purkinje fibers
What is a cardiac cycle?
- coordinated sequence of mechanical and electrical events that repeats with every heartbeat
- At a HR of 75 bets/min, each cardiac cycle last 0.8 seconds
What is systole?
- Period of contraction and emptying
- Atrial systole and ventricular systole
What is Diastole?
- Period of relaxation and filling
- Atrial diastole and ventricular diastole
What is Stroke Volume (SV)?
- Quantity of blood pumped out either ventricle per beat
- @ REST - 70 ml/beat\; max 120 ml/ beat
What is HR?
- # of times the HR bats per minute
- @ REST - 72 bats/min; Max = 230 beats/min
What is Cardiac Output? (CO)
- Quantity of blood pumped by either ventricle per minuet
- @ rest= 5L/min; Max 20-25 L/min
**HR X SV = CO
What is Venous Return (VR) ?
- Quantity of blood returned to the heart per minute
- Normally, venous returns = CO
What is End Diastolic Volume? (EDV)
-Quantity of blood remaining in either ventricle at the end of ventricular diastole
***AVG = 130 ml
What is End Systolic Volume (ESV)?
-Quantity of blood remaining in either ventricle at the end of ventricular systole
In the Wigger’s Diagram, What happens at the end of isovolumetric ventricular relaxation?
L. Atrial (LAP) exceeds L. ventricular pressure (LVP)
Result: opening of the mitral valve
***Ventricular filling occurs
What are the 3 distinct phases of ventricular filling?
1) Rapid passive filling
2) Slow passive filling (diastasis)
3) Atrial Systole
What occurs in Rapid passive filling during ventricular filling?
Blood flows quickly thru the mitral valve & into the relaxed ventricle ; Ventricular volume INCREASES
- *No muscle contraction occurs
- 3rd HEART SOUND PRODUCED
What occurs during Slow Passive Filling?
Blood flows slowly thru the mitral valve & into the relaxed ventricle;
- ** Ventricular volume continues to increase (majority of ventricular filling!!)
- No muscle contraction
What occurs during Atrial Systole?
- The L. Atrium must FIRST depolarize
- Atria contract—> 4th heart sound produced
** Contribution of atrial contraction to ventricular filling his usually SMALL( 10-15 % of the total ventricular volume)
What occurs after Atrial Systole, LVP > LAP and the mitral valve shuts?
The 1st heart sound is produced
*** The volume of blood in the left ventricle at this point is the EDV ( increases the pre-load–> increases amount of blood ejected during systole)
What occurs during isovolumetric ventricular contraction?
-The L. ventricle must FIRST be depolarized
- Ventricles contract, & LVP rises
- NO EJECTION of BLOOD OCCURS as the L. ventricular volume remains constant
What occurs during RAPID ventricular ejection?
The L. ventricular develops enough pressure such that LVP exceeds aortic pressure
-Aortic semilunar valve OPENS and BLOOD is EJECTED; Aortic pressure rises & L. Ventricular pressure
What occurs when entering back into isovolumetric ventricular relaxation?
-Once blood is ejected, LVP falls below Aortic pressure & the Aortic Semilunar valve SHUTS; 2nd heart sound produced
- Volume of blood remaining in the L. Ventricle after ejection is the ESV
- Aortic pressure falls as blood runs off to arteries
- **T wave produced
During Isovolumetric ventricular relaxation what occurs when all 4 chambers are relaxed and all of tis valves are CLOSED?
- Ventricular volume is constant; Ventricular pressure is decreasing
- The L. atrium is filling w/ blood that has returned to it via pulmonary veins; atrial pressure is rising
What occurs during the Dichrotic Notch?
-CLOSURE of the AORTIC VALVE causes a brief rise in aortic pressure as back-flowing blood rebound off the closed valve cusps
Note: significant in relation to coronary blood flow !
