ECG & CV Test Review

Which chamber pumps blood to the lungs?

Right ventricle

Which chamber pumps blood to the body?

Left ventricle

Which valve prevents backflow of blood into left atrium?

Mitral valve (also known as the bicuspid valve)

Which valve prevents backflow of blood into right atrium?

Tricuspid valve

Which valve prevents backflow of blood into left ventricle?

Aortic valve

Which valve prevents backflow of blood into right ventricle?

Pulmonary valve

Which blood vessel is the site of gas, nutrients, hormone, and waste exchange between the blood and the cells.

Capillaries

What’s the difference between pulmonary and systemic circulation?

• Pulmonary circulation carries deoxygenated blood from the right side of the heart to the lungs (to release $\text{CO}_2$ and pick up $\text{O}_2$) and returns oxygenated blood to the left side.

• Systemic circulation carries oxygenated blood from the left side of the heart to the rest of the body (delivering nutrients and $\text{O}_2$) and returns deoxygenated blood to the right sid

What is coronary circulation?

The network of blood vessels (coronary arteries and veins) that supplies oxygenated blood and nutrients directly to the heart muscle (myocardium) and removes metabolic waste.

What artery is known as the "widow maker" when severely blocked?

Left anterior descending (LAD) artery

What’s the difference between depolarization and repolarization?

• Depolarization: The electrical activation of myocardial cells caused by an influx of positive ions (primarily sodium), which triggers muscular contraction.

• Repolarization: The return of the cell's membrane to its resting electrical state via ion movement (primarily potassium), allowing the muscle to relax.

What is the natural pacemaker of the heart? What does it do? What is its rate range?

Sinoatrial (SA) node. It initiates electrical impulses that set the rhythm and basic rate of the heart.

Rate range: 60 to 100 beats per minute (bpm)

What does the AV node do? What is its rate range?

• Atrioventricular (AV) node. It temporarily delays the electrical impulse to allow the ventricles to fill completely with blood before they contract.

• Rate range: 40 to 60 bpm.

What does the Bundle of His do?

Conducts electrical impulses from the AV node down through the fibrous skeleton of the heart into the interventricular septum.

What does the Right Bundle Branch (RBB) do?

Carries electrical impulses down the right side of the interventricular septum to the right ventricle.

What does the Left Bundle Branch (LBB) do?

Carries electrical impulses down the left side of the interventricular septum to the left ventricle.

What do the Purkinje Fibers do? What is its rate range?

• A network of fibers that rapidly spread electrical impulses throughout the ventricular myocardium to trigger coordinated ventricular contraction.

• Rate range: 20 to 40 bpm.

What’s the difference between systole and diastole?

• Systole: The contraction phase of the heart chambers where blood is pumped out.

• Diastole: The relaxation phase of the heart chambers where they fill with blood.

What it is the purpose of an ECG?

• To record the heart's electrical activity over time, aiding in the diagnosis of arrhythmias, heart attacks (myocardial infarction), electrolyte imbalances, and structural issues.

What are electrodes?

Adhesive sensor pads placed on the patient's skin to detect the electrical currents generated by the heart.

What are leads?

• Graphical views or perspectives of the heart's electrical activity, calculated by measuring voltage differences between combinations of electrodes.

How many electrodes are used to create a 12-lead ECG? How is this possible?

10 electrodes are used (4 limb electrodes and 6 chest electrodes). This creates 12 distinct electrical views by measuring signals from different physical angles and mathematically combining them (using Einthoven's triangle and Wilson's central terminal).

What is the ground electrode?

Typically placed on the right leg, it acts as a baseline reference point to minimize electrical interference and noise.

Where is precordial chest lead V1 placed?

• Fourth intercostal space at the right sternal border.

Where is precordial chest lead V2 placed?

Fourth intercostal space at the left sternal border.

Where is precordial chest lead V3 placed?

Midway between V2 and V4.

Where is precordial chest lead V4 placed?

Fifth intercostal space at the left midclavicular line.

Where is precordial chest lead V5 placed?

Fifth intercostal space at the left anterior axillary line (horizontal to V4).

Where is precordial chest lead V6 placed?

• Fifth intercostal space at the left midaxillary line (horizontal to V4 and V5).

What is an artifact?

Unwanted external or physiological interference/noise on an ECG tracing that distorts the accurate electrical wave signals.

Distinguish between Somatic Tremor Artifact, Wandering Baseline, AC Interference.

• Somatic Tremor: Caused by patient movement, muscle tension, or shivering, producing jagged, irregular baseline fluctuations.

• Wandering Baseline: Caused by breathing movements, poor skin preparation, or loose electrodes, causing the baseline to drift up and down.

• AC Interference: Caused by nearby electrical equipment or power lines, producing uniform, small, sharp, jagged spikes.

What does the P wave represent? What is its normal duration?

• Represents atrial depolarization.

• Normal duration: Less than 0.12 seconds (under 3 small boxes).

What does the PR Segment represent?

Represents the delay of the electrical impulse at the AV node (the flat line between the end of the P wave and the start of the QRS complex).

What does the PR Interval represent?

• Represents the time from the start of atrial depolarization to the start of ventricular depolarization (beginning of P wave to beginning of QRS).

• Normal duration: 0.12 to 0.20 seconds (3 to 5 small boxes).

What does the QRS complex represent? What is its normal duration?

• Represents ventricular depolarization.

• Normal duration: 0.06 to 0.10 seconds (less than 0.12 seconds).

What happens during the creation of the Q wave?

The initial downward deflection of the QRS complex, representing the depolarization of the interventricular septum (from left to right).

What happens during the creation of the R wave?

The first upward deflection of the QRS complex, representing the mass depolarization of the ventricular walls.

What happens during the creation of the S wave?

The downward deflection following the R wave, representing the final depolarization of the basal portions of the ventricles.

What the ST Segment represents? What are the clinical significances?

• Represents the interval between ventricular depolarization and repolarization (when ventricles are fully contracted).

• Clinical significance: Elevation or depression can indicate acute myocardial injury, ischemia, or infarction (heart attack).

What does the T wave represent? What does an invert T wave indicate?

• Represents ventricular repolarization.

• Inverted T wave indication: Can indicate myocardial ischemia, myocardial infarction, electrolyte disturbances, or ventricular hypertrophy.

What does the QT Interval represent? What is the clinical significance?

• Represents the total time taken for ventricular depolarization and repolarization.

• Clinical significance: A prolonged QT interval can put a patient at risk for dangerous, life-threatening ventricular arrhythmias like Torsades de Pointes.

If the U wave is seen, what is the clinical significance?

• A small wave following the T wave (representing repolarization of the Purkinje fibers).

• Clinical significance: While sometimes normal, a prominent U wave often points to hypokalemia (low potassium levels), medication side effects, or heart disease.