Lab 4: Questions

What does an ECG measure? A) an individual cardiac action potential B) mechanical events in the heart C) the collective electrical activity of the heart D) the movement of the cardiac muscles

C) the collective electrical activity of the heart

Which lead usually has the largest R wave? A) I B) II C) III

B) II

Based on both of the images on this page, which limb lead's axis is the closest to a normal cardiac axis vector? A) Lead I B) Lead II C) Lead III D) Lead aVF E) Lead aVL F) Lead aVR

B) Lead II

Which is heard in aortic stenosis? A) a mid-diastolic murmur B) a murmur that peaks during mid-systole C) a murmur that lasts throughout diastole D) a murmur of equal amplitude that lasts throughout systole

B) a murmur that peaks during mid-systole

What do you feel when palpating a pulse? A) blood flow B) pressure wave

B) pressure wave

Aortic stenosis

The defective valve impedes blood flow during ventricular systole. This results in a characteristic systolic murmur that increases in loudness to mid-systole and then fades gradually. The second heart sound may be softer than normal, too.

True/False: the correct naming of the complexes in Lead V1 in this example is RsR'.

True

The ECG is a useful tool for detecting which of the following? Ventricular arrhythmias Abnormal plasma sodium Abnormal heart valves An enlarged left ventricle

USEFUL: >Ventricular arrhythmias >An enlarged left ventricle NOT USEFUL: >Abnormal plasma sodium >Abnormal heart valves

How many electrodes are used to create 12 different leads (i.e., 12 different electrode configurations)? A) 3 B) 4 C) 10 D) 12

C) 10

Aortic regurgitation

The defective valve does not close properly so blood flows back into the ventricle during early diastole. This results in an early diastolic murmur that follows the second heart sound and gradually decreases in intensity.

Which of the lower red arrows (a-d) is the correct summation of the upper two blue arrows? a b c d

a

Why is ventricular systolic pressure greater on the left side of the heart? A) because the aortic valve is stiffer than the pulmonary valve and thus requires a greater pressure to open it B) because the left side of the heart pumps a greater amount of blood than the right side of the heart C) to overcome the greater vascular resistance of the systemic circulation D) all of the above

C) to overcome the greater vascular resistance of the systemic circulation

Describe the relationships between the first and second heart sounds, and the finger pulse.

In relation to the heart sounds, the finger pulse is delayed. The finger pulse's rise begins after the first sound, and it reaches a maximum at approximately the time of the second sound. The dicrotic notch in the pulse waveform follows the second heart sound. The dicrotic notch is a short-lived decrease in pressure in the ascending aorta, which occurs following closure of the aortic valve. Blood that has just been pumped out of the left ventricle temporarily flows back against the closed valve, which gives rise to the characteristic V-shaped notch in the pulse pressure wave. It is sometimes used as a marker for the end of systole.

Describe the physiological events occurring in the heart muscle represented by each ECG component (the P wave, QRS complex, and T wave). Why does the QRS complex have the largest amplitude?

The P wave represents atrial depolarization. The QRS complex represents ventricular depolarization. Atrial repolarization is occurring at the same time as ventricular depolarization, but is relatively small and consequently hidden by the QRS. The T wave represents ventricular repolarization. The QRS is largest as the muscle mass of the ventricles is greater than that of the atria, and ventricular depolarization occurs significantly faster than ventricular repolarization.

Anatomical sites where a pulse can be palpated often correspond to "pressure points" for stopping hemorrhage in first aid treatment. Why?

These points are where the arteries are closest to the skin and close to bone, which serves as an excellent surface on which to compress the artery.

The phases of the cardiac cycle are shown in the diagram above: atrial contraction, isovolumetric contraction, ejection, isovolumetric relaxation and rapid filling. When do the AV valves close? A) at the start of isovolumetric contraction B) between ejection and isovolumetric relaxation C) between isovolumetric contraction and ejection D) between isovolumetric relaxation and rapid filling E) between rapid filling and atrial contraction

A) at the start of isovolumetric contraction

Which of the following is responsible for generating the first heart sound, then the second heart sound? A) closing of the AV valves, then closing of the semilunar valves B) closing of the AV valves, then opening of the semilunar valves C) opening of the AV valves, then opening of the semilunar valves D) opening of the semilunar valves, then opening of the AV valves

A) closing of the AV valves, then closing of the semilunar valves

Systole includes which two stages of the cardiac cycle? A) isovolumetric contraction and ejection B) isovolumetric contraction and isovolumetric relaxation C) isovolumetric contraction and rapid filling D) rapid filling and atrial contraction

A) isovolumetric contraction and ejection

How many limb leads are there in a standard 12-lead ECG? A) 3 B) 6 C) 10 D) 12

B) 6

During which phase does the left ventricular volume remain the same and the left ventricular pressure increase rapidly? A) atrial contraction B) ejection C) IVCT D) IVRT E) rapid filling

C) IVCT

During which phase of systole does the aortic valve remain closed? A) atrial contraction B) ejection C) IVCT D) IVCT and Ejection E) IVRT F) rapid filling

C) IVCT

Which region of the heart generates electrical activity the fastest? A) AV Node B) internodal tracts C) purkinje fibers D) SA Node

D) SA Node

Which of these sentences is true? A) from an ECG, the single electrical axis can be determined and it sits in one of four heart quadrants B) lead II is the only lead with a large positive R wave on an ECG C) the electrical axis is a single cardiac action potential recorded over the course of the cardiac cycle D) the electrical axis is a combination of all the action potentials in the heart

D) the electrical axis is a combination of all the action potentials in the heart

All vectors are moving away from aVR. What does this mean for the QRS complex, the P wave and the T wave in an aVR ECG tracing? A) the main wave in the QRS complex and the P wave are negative, but the T wave is positive B) the main wave in the QRS complex and the T wave are negative, but the P wave is positive C) the main wave in the QRS complex is negative, but the P and T waves are positive D) the main wave in the QRS complex, P wave, and T wave are all negative

D) the main wave in the QRS complex, P wave, and T wave are all negative

The AV valves are forced closed when ________ pressure becomes ________ than ________ pressure. A) atrial; greater; venous B) atrial; greater; ventricular C) ventricular; greater; aortic D) ventricular; greater; atrial

D) ventricular; greater; atrial

Mitral regurgitation

Damage to the valve structure leads to a leak of blood from the contracting ventricle. This leak results in a high-pitched murmur heard throughout systole. There may also be a third heart sound.

Which statement correctly describes the cardiac cycle's two phases? A) diastole - atria relax; systole - ventricles relax B) diastole - ventricles contract; systole - ventricles relax C) systole - atria contract; diastole - ventricles contract D) systole - atria relax; diastole - atria contract E) systole - ventricles contract; diastole - ventricles relax

E) systole - ventricles contract; diastole - ventricles relax

True/False: The volume of the blood received and ejected via the left ventricle is greater than the volume of blood received and ejected via the right ventricle.

False

Which of these events are associated with systole and which are associated with diastole? A fall in ventricular blood volume The second heart sound Rapidly increasing ventricular pressure The P wave A rapid increase in aortic pressure

SYSTOLIC: >A fall in ventricular blood volume >Rapidly increasing ventricular pressure >A rapid increase in aortic pressure DIASTOLIC: >The P wave >The second heart sound

Categorize the following statements regarding heart valves and sounds. A heart sound is heard when a heart valve closes A heart sound is heard when a heart valve opens A heart sound is heard both when the heart valve opens and when it closes Heart valves close when the ventricles reach their maximum filling capacity The first heart sound is due to the closure of the AV valves

TRUE: >A heart sound is heard when a heart valve closes >The first heart sound is due to the closure of the AV valves FALSE: >A heart sound is heard when a heart valve opens >A heart sound is heard both when the heart valve opens and when it closes >Heart valves close when the ventricles reach their maximum filling capacity

Which of the following statements about the chest leads is true, and which are false? In V1 and V2, both positive and negative P waves can be normal In V1 and V2, T waves are always positive V1 and V2 face the wall of the right ventricle V3 and V4 may have prominent R and S waves V3 and V4 lie near the interventricular septum

TRUE: >In V1 and V2, both positive and negative P waves can be normal >V1 and V2 face the wall of the right ventricle >V3 and V4 may have prominent R and S waves >V3 and V4 lie near the interventricular septum FALSE: >In V1 and V2, T waves are always positive

Which of the following statements about the limb leads are true, and which are false? Lead II is usually the lead with the greatest R wave amplitude Lead III is the best lead for detecting P waves Einthoven's Triangle is an imaginary triangle -- not a piece of medical equipment

TRUE: >Lead II is usually the lead with the greatest R wave amplitude >Einthoven's Triangle is an imaginary triangle -- not a piece of medical equipment FALSE: >Lead III is the best lead for detecting P waves

Categorize the following statements about the cardiac cycle. The AV and semilunar valves are never open at the same time during the cardiac cycle The AV and semilunar valves are never closed at the same time during the cardiac cycle When the atria contract, blood is forced into the ventricles through the open AV valves The cardiac cycle begins with early ventricular systole The term "cardiac cycle" has the same meaning as "cardiac output" There is a delay between the right AV valve closing and the left AV valve due to volume differences in the ventricles

TRUE: >The AV and semilunar valves are never open at the same time during the cardiac cycle >When the atria contract, blood is forced into the ventricles through the open AV valves FALSE: >The AV and semilunar valves are never closed at the same time during the cardiac cycle >The cardiac cycle begins with early ventricular systole >The term "cardiac cycle" has the same meaning as "cardiac output" >There is a delay between the right AV valve closing and the left AV valve due to volume differences in the ventricles

Why does the second heart sound occur after the T wave?

The T wave represents ventricular repolarization. This is followed by ventricular relaxation, during which the pressure in the ventricles falls. When the pressure in the left ventricle falls below the pressure in the aorta, the aortic valve closes. When the pressure in the right ventricle falls below the pressure in the main pulmonary artery, the pulmonary valve closes. It is the closure of these two valves that is heard as the second heart sound. Together the aortic and pulmonary valves are known as the semilunar valves.

Would the relationship be the same if you had recorded the carotid pulse? Justify your answer.

The carotid pulse would show the same relationship as the finger pulse. The carotid pulse's rise would begin after the first sound, and it would show a characteristic dicrotic notch following the second heart sound. As the pulse wave takes a finite time to travel, we see a significant delay from the heart sounds to the corresponding events in the pulse wave when it is measured at the finger. Since the carotid artery is nearer to the heart, the carotid pulse will begin to rise earlier and reach a peak sooner than seen in the more peripheral finger pulse recording.

What affect did compression of each artery have on the finger pulse? What do you conclude from your results?

The finger pulse was relatively unaffected when either the radial or ulnar arteries were compressed. However, compression of the brachial artery largely abolished the finger pulse. The conclusion is that the palmar arches are supplied by both the radial and ulnar arteries, and loss of one arterial supply is compensated for by the other.

What activity in the heart is associated with the first heart sound ("lub"), and what is associated with the second ("dub")?

The first heart sound "lub" occurs during early ventricular systole. The atria relax while the ventricles contract. The atrioventricular (AV) valves are forced closed. This closure prevents the backflow of blood. Interestingly, part of the sound may also derive from mechanical events occurring in the ventricular muscle. The second heart sound "dub" occurs during early ventricular diastole. The atria and ventricles relax. Pressure fails in the aorta and pulmonary arteries, and the semilunar valves close. This closure prevents backflow of blood into the ventricles.

Mitral stenosis

There is narrowing of the orifice of the valve. A low pitched, mid-diastolic murmur is heard. There is often a louder than normal first sound as the valve is shut more forcefully than normal.

True/False: If an aortic valve was fibrosed and unable to open properly, there would be obstruction to flow through the valve during ventricular systole, giving a systolic murmur.

True