CARDIAC ANATOMY
The apex of the heart is located at the _.
Tip of the left ventricle.
The cardiac cell at rest has what kind of electrical charge?
Negative charge due to high intracellular potassium (K+), low intracellular sodium (Na+), and the action of the Na+/K+ pump, which keeps more positive ions outside than inside.
The QRS complex represents _.
Ventricular depolarization
The baseline on the EKG strip is considered to be the
Isoelectric line. It represents the zero-voltage reference point. Used as the baseline to determine elevation or depression of waveforms (e.g., ST elevation/depression).
A beat that appears on the rhythm strip after a long pause and causes a slower rhythm than the normal rhythm is called a(n) _.
Escape beat ~ atrial escape beat if it originates in the atria, junctional escape beat if it comes from the AV junction, Ventricular escape beat if it originates in the ventricles.
Escape beats are the heart's protective backup mechanism that prevent the rhythm from stopping when the primary pacemaker (Usually the SA node) fails or pauses.
Which statement about the RA is true?
1. It is a receiving chamber for Oxygenated blood returning from the lungs.
2. It is the major pumping chamber of the heart.
3. It is about 100% saturated with Oxygen.
4. It is the receiving chamber for deoxygenated blood coming from the vena cava.
4. It is the receiving chamber for deoxygenated blood coming from the vena cava.
Phase 3 – Repolarization
Which interval is the atrial depolarization + delay at the AV node before reaching the ventricles.
PR Interval
The PR interval measures the time it takes for the impulse to travel from the _.
The PR interval measures the time it takes for the impulse to travel from the SA node through the atria and the AV node.
Sinus tachycardia's heart rate is
> 100 bpm
Which valves open to allow the ventricles to fill?
Atrioventricular Valves (Tricuspid and Mitral)
Phase 1 – Initial Repolarization
Depolarization of a cardiac cell occurs when:
Sodium rushes into the cell
Which of the following is NOT a bipolar lead?
aVF → This is an augmented unipolar limb lead, not bipolar.
Bipolar Leads
In which rhythm is an escape beat sometimes seen?
Sinus arrest / sinus pause
The first heart sound (S1) is associated with the closure of which heart valves?
Atrioventricular Valves (Tricuspid and Mitral)
Phase 0 – Rapid Depolarization
Repolarization of a ventricular myocyte is primarily caused by:
Potassium efflux
Name the three augmented leads.
Which of the following junctional rhythms typically cause no ill effects?
PJC and accelerated junctional rhythm
Blood clots collecting in the atria are a possible complication of what rhythm?
Atrial Fibrillation
Phase 2 – Plateau Phase
The plateau phase (Phase 2) of the action potential is mainly due to:
Equal movement of calcium in and potassium out
Lead II connects which limbs?
Right arm (Negative electrode)
Left leg (positive electrode)
Lead II “travels down the body” — right arm → left leg — which is why it usually shows the clearest P waves and is commonly used for monitoring.
Junctional rhythms originate in the
atrioventricular junction.
Name the five great arteries that arise off the base of the heart.
1. Superior Vena Cava
2. Inferior Vena Cava
3. Pulmonary Artery
4. Aorta
5. Pulmonary Veins
Pacemaker cells have only three phases. What are they?
Pacemaker cells have phases 0, 3, and 4 only:
Phase 0 of the ventricular action potential corresponds to what on the EKG?
QRS complex
What are the V1 through V6 leads called?
Precordial or chest leads. They are unipolar leads.
In first-degree AV block, the site of the block is the
AV Node